JP2005265486A - Measuring process for combustion propagation analysis of fuel and flame spreading, and test method of flame propagation mode of fuel using device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air flow tracking device for measuring combustion propagation analysis between fuel droplets and flame spreading in the nongravitaional or microgravitational state by PTV measurement, and a test method of a flame propagation mode by the PTV measurement between fuel droplet particles. <P>SOLUTION: This measuring device for combustion propagation analysis and flame spreading has (a) in a housing or in a partitioned space, (b) a suspension line support base for supporting a suspension line, (c) a droplet generation device for generating a simulated droplet, (d) a tracer particle supply device for supplying a tracer particle cloud, and (e) an ignition device, and also has (f) an optical measuring system and (g) a sequencer for controlling them. In the device, (d) the tracer particle supply device has (d1) a tracer particle selection means for removing gross particles in the tracer particles and supplying only particles having the uniform particle size. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a combustion propagation analysis of liquid fuel, a flame spread measurement apparatus, and a test method of a fuel flame propagation mode using the apparatus, and more particularly, a combustion propagation analysis of fuel under zero gravity or microgravity by PTV measurement. Further, the present invention relates to an air flow tracking device for measuring flame spread and a flame propagation mode test method by PTV measurement between fuel droplet particles using the device. The present invention also relates to an apparatus for measuring liquid fuel under zero or microgravity, and a method for testing a flame propagation mode of fuel using the apparatus.

  Conventionally, laser Doppler velocimeters and hot wire anemometers have been used for gas flow measurement, and temporal changes at a specific point have been measured. However, in a general turbulent flow field, turbulent vortices with various dimensions are generated intermittently, and their distribution changes in a complex manner with time. It is difficult to estimate based on time-series flow velocity data. Therefore, in recent years, in conjunction with advances in image processing and analysis technology, it may be attempted to determine the spatial distribution of the flow velocity by recording and analyzing laser seed images of a large number of seed particles suspended in the fluid. However, for this image flow velocity measurement, a particle tracking velocity method (PTV method) that tracks the movement of individual particles and a particle image flow velocity that statistically determines the movement of the particle group. (Particle Image Velocimetry; PIV method) has been carried out. Among them, the PIV method is a famous book by Markus Raffel, Christian E. Willert, Jeurgen Kompenhaus of Deutsches Zentrum fur Luft und Raum-fahrt (DLR) in Goettingen (in Japan, supervised by Toshio Kobayashi, Koji Okamoto, Masaaki Kawahashi, Shigeru Nishio) "PIV-Fundamentals and Applications of Particle Image Velocimetry" has been published). The PIV method includes auto-correlation PIV measurement and cross-correlation PIV measurement. In either case, the start and end points of the trace are determined by analyzing the trace image taken in units of several hundred microseconds. Thus, when obtaining the velocity vector, it is said that it can be used for measuring the gas flow in a cylinder of an internal combustion engine which is practical and less difficult to set the seed condition than the PTV method (Non-Patent Document). 1) is still based on the PTV method, which requires a PTV technique that can overcome the problems imposed on the seed conditions and perform accurate measurement. It is an important thing that can be a basic technical means to support the development of excellent PIV measurement technology.

In other words, the cars that have been used as the largest means of transportation in the 20th century are unlikely to take over for a while in the 21st century, and many vehicles such as electric cars, fuel cell cars, hybrid cars, natural gas cars, methanol cars, etc. Although pollution vehicles are being studied, developed and operated, it takes time to disseminate, and from such a current situation, improvement of exhaust gas from gasoline and diesel vehicles by state-of-the-art technology has become an urgent issue.
Spray combustion, which atomizes and burns liquid fuel, is a combustion method widely used in combustors such as boilers, furnaces, diesel engines, liquid rocket engines, and gas turbines. Elucidation of the mechanism of spray combustion contributes to the improvement of the performance of these combustors, and various problems such as improvement of fuel consumption rate and reduction of toxic gas emission, are now urgent issues of energy and environmental issues. It is thought that it will help to solve the problem. If the mechanism of combustion is clarified and the design of the combustor is theoretically performed, it is thought that it will greatly help industrially, such as shortening the development period and reducing development costs. It is a phenomenon that occurs in a very heterogeneous system consisting of fuel vapor and air. There are many factors governing spray combustion, and important ones include droplet diameter, fuel composition, temperature, gas composition, pressure, and the relative motion of the droplet and the surrounding gas. Further, since evaporation, diffusion, and mixing, and combustion of the resulting air-fuel mixture proceed and affect each other at the same time, it is very difficult to analyze the spray combustion phenomenon as it is. Therefore, there are many cases where individual combustion devices have been studied individually, and the general characteristics of spray combustion have not been grasped at present. In order to elucidate spray combustion, the following two approaches have been considered. When the vaporization of the droplets during spraying is extremely rapid and the combustion process proceeds relatively slowly, it is considered that combustion starts after evaporation of the droplets, which is close to the combustion of a burner diffusion flame. There have been many studies using burner diffusion flames and simple models of flames. On the other hand, when the droplets in the spray are relatively large and the combustion process proceeds relatively quickly, liquid phase particles remain until the end of combustion, and the evaporation process and the combustion process are parallel. It will be in a state of progress, and the evaporation rate of the droplets is considered to be a major factor governing its combustion rate. Based on this idea, research on droplet combustion has been conducted using a single fuel droplet, which is the minimum structural unit of spray combustion. However, in actual spray combustion, combustion proceeds while a large number of fuel droplets generated in the space influence each other. Therefore, there is a breakthrough in simply extending the knowledge gained from single fuel droplet research to spray combustion. The knowledge obtained from the study of the behavior of droplet interference and spread of fuel droplets is necessary.

  Therefore, when reviewing related technologies that have been publicly disclosed, Konishi et al. Measured the combustion rate constants when suspended droplets were placed horizontally and vertically, and calculated the correlation with the droplet spacing. As a result of shooting the flame, the interference effect between the droplets was as follows: 1) The combustion rate constant increased monotonously with the increase in the droplet interval, then gradually approached the value for a single droplet, 2 (1) A decrease in the combustion rate constant is observed when a single flame is in a collective combustion state covering the entire droplet row (Non-Patent Document 2).

  Mikami et al. Conducted a combustion experiment using two droplets of the same diameter and the same fuel in a normal gravity field and a microgravity field. In the gravitational field, the oxygen deficiency between the flames is not as severe as in the microgravity field, and when the two flames exist in a separated form, the effect of natural convection that supplies oxygen to the flame is stronger as the initial droplet interval is smaller, Except for the initial stage of combustion, the burning rate for the same dimensionless droplet diameter decreases monotonically with decreasing initial droplet spacing in the microgravity field, whereas it becomes maximum at an initial droplet spacing in the normal gravity field. Therefore, it has been reported that the influence of gravity on the interference combustion of droplets is maximized at a certain initial droplet interval (Non-patent Document 3).

  Yoshida et al. Arranged 10 quartz wire suspension lines in a line and suspended fuel droplets in a high-pressure atmosphere, then ignited the first fuel droplets in a microgravity field, and observed the flame burnout. As a result of the measurement of the flame spread speed, the flame propagation depends on the ambient pressure and the droplet interval, 1) flame propagation that occurs continuously, 2) flame propagation that occurs intermittently, 3) two adjacent droplets Report that it was found that there are three types of propagation mechanism of intermittent flames that ignite almost simultaneously (Non-Patent Document 4), and investigated the temperature distribution around the flames using a spherically symmetric heat conduction equation, We are studying the propagation mechanism.

  Kakuta et al. Also ignited and burned fuel droplets when a laminar flame propagating through a lean propane-air mixture filled in a constant pressure combustion vessel passed through a fuel droplet row held by quartz yarn. Investigation of the behavior and experiments show that the ignition delay of fuel droplets increases with increasing initial droplet diameter, increasing the normal boiling point of the fuel, and decreasing the equivalence ratio of the lean mixture. It can be seen that the propagating flame surface deforms in a convex shape in the traveling direction when passing through the droplet, and the curve indicating the ignition delay of the downstream droplet has a minimum value when the droplet interval is changed. It has been announced that it has been found (Non-patent Document 5).

  Umemura et al. Theoretically analyzed the growth process of diffusion flames created around ignited droplets, and revealed the mechanism of flame propagation between droplets at the front of the group-burning flame of a linear droplet row. The result of the analysis predicts the dependence on the droplet spacing recently measured in microgravity experiments, and supports the validity of the proposed flame propagation mechanism. Maximum flame propagation velocity is achieved with a droplet train with droplet spacing comparable to the maximum flame diameter achieved with isolated droplets burning under the same atmospheric conditions, mainly due to the heating of the droplets It is announced that it is governed by time, and the differences in the flame propagation mechanisms of the three modes that appear with changes in the droplet spacing are also considered (Non-Patent Documents 6 to 8).

  Kobayashi et al. Conducted a flank spreading experiment of decane droplets in a supercritical atmosphere in a microgravity field. Up to an atmospheric pressure of 5 MPa, the burning spread rate decreased as the pressure increased in the microgravity field, and the atmospheric pressure in a normal gravitational field as well. However, in the microgravity field, the droplets that burned at the critical pressure heated the droplets that were not burning. As a result of a verification experiment to investigate the fuel vapor ejection mechanism, it was observed that the fuel vapor was ejected by Marangoni convection. Published (Non-Patent Document 9).

  Furthermore, Kikuchi et al. Used a decane with a fuel droplet diameter of 1 mm and an initial ambient temperature of 573 K to determine the effect of premixed gas ignition, premixed flame structure, and heat conduction effect of droplets that did not spread. As a result of numerical calculation of the flame spread of the droplet row by changing the interval, diameter, and ambient temperature of the droplet to investigate, if the droplet interval is small, the flame front does not propagate through the premixed layer between the droplets The flame front travels through the premixing layer between the droplets when traveling around the droplets and the droplet spacing is relatively large, and when the droplet spacing is even larger, the flame is a droplet that does not spread out. It is reported that this occurs in droplets that do not spread before the premixed gas mixture spreads, and this process is considered to be an intermediate phenomenon of discontinuous premixed flame propagation. , The tendency of flame propagation speed is consistent with the experimental results of Non-Patent Document 9 Report are (Non-Patent Document 10).

  N. Rotii et al. Conducted an experiment in which droplets were launched in three rows, ignited from the end of a droplet stream, and the droplet diameter, mass flow rate, droplet temperature, and droplet row spacing were set constant. As a result of observing the spread and change, the spread rate increases as the initial droplet temperature increases. When the mass flow rate is constant, the droplet diameter is independent of the spread rate, It has been reported that the flame spread rate increases when the mass flow rate is increased (Non-patent Document 11).

  These studies looked at the spread of fire between droplets. In conventional research on combustion of fuel droplet arrays, a method of fixing fuel droplets in space using a suspension line such as a thin quartz thread has been used. However, in the droplet fixing method using the catenary line, the influence of the flow generated by the combustion on the movement of the liquid droplet and the movement of the liquid droplet on the flame spread cannot be examined.

Masahiro Shioji, Hiroshi Kawanabe; Progress of fuel measurement technology 2-Measurement of gas flow by particle image velocimetry (PIV)-; "Combustion Research" 113, 11-20 (1998) Katsuyuki Konishi (Harima Ishikawa Heavy Industries), Michikata Kono (Tokyo Univ.), Kazuo Iinuma (Hosei Univ.): Interference effect on combustion of fuel droplet trains, in Japanese, Journal of JSME, Vol.51, No.467, ( 1985), Page2218-2224 M. Mikami, H. Kato, J. Sato, and M. Kono ,: Influence of gravity on the interference combustion of fuel droplets, in Japanese, Journal of JSME, B, 61, (1994), 373-379 Shigetori Yoshida, Hitoshi Hara, Satoshi Okajima: Flame Propagation of Fuel Droplets in a High Pressure Atmosphere under Zero Gravity, in Japanese, Journal of JSME, B.55, (1989), Page1241-1246) T. Kadota, R. Kohama, D. Segawa, and M. Tsue .: Ignition of fuel droplet arrays by laminar propagation flames, in Japanese, Journal of JSME, B, 65, (1999), 303-309) A. Umemura, in: Flame propagation along a linear fuel droplet array under microgravity (3rd report, Model calculation of flame propagation), in Japanese, Journal of JSME, B, 68, (2002), 2636-2642 A. Umemura ,: Propagation of flame along a straight fuel droplet array under microgravity (2nd report, Flame propagation velocity characteristics), in Japanese, Journal of JSME, B68, (2002), 2429-2436 A. Umemura, in: “Flame Propagation along a Linear Fuel Droplet under Microgravity” (1st Report, Creating a Map of Flame Propagation Mode between Droplets), in Japanese, Journal of JSME, B, ( 2002), 68,2422-2428) H. Kobayashi, J. Park, T. Iwahashi, and T. Niioka ,: Flame spread experiment of n-decane droplets in high-pressure atmosphere, The Proc. Combust. Inst., 29, (2002), 2603- 2610) M. Kikuchi, T. Arai, S. Yoda, T. Tsukamoto, A. Umemura, M. Uchida, M. Kakei, and T. Niioka: Propagation of fuel droplets in microgravity and high temperature environments Study on Numerical Computation, The Proc. Combust. Inst., 29, (2002), 2611-2619) N. Rotii, A. Kari, K. Anders, and A. Froiin, Study of flow interaction near droplets and droplet row flame propagation, The Proc. Combust. Inst. 26, (1996), 1697-1703

Therefore, the object of the present invention is to easily and accurately analyze the behavior of specific fine particles, and in particular, to analyze the behavior of specific fine particles easily and accurately considering the correlation with neighboring similar particles by the PTV method. Combustion propagation analysis and flame spread that overcomes the constraints imposed on the seed conditions unique to the PTV method by removing only very coarse particles and providing only fine particles of uniform particle size to the marker for measurement. And a test method for a flame propagation mode of a fuel using the apparatus.
Another object of the present invention is to analyze the combustion propagation between fuel droplets under zero gravity or microgravity and to analyze the flame propagation of liquid fuel and the flame spread measurement device suitable for measuring flame spread. An object of the present invention is to provide a method for testing a flame propagation mode of a fuel using the apparatus.
According to the present invention, in particular, a novel and suitable airflow tracking device for analyzing combustion propagation between fuel droplets under zero gravity or microgravity by PTV measurement and measuring flame spread, and fuel liquid using the device A test method of flame propagation mode by PTV measurement between droplet particles is provided.

  In the present invention, focusing on the movement of the droplets in the direction of the flame spread of the fuel droplet row, an experiment was conducted using a simple one-dimensional model of three fuel droplet rows (fixed-fixed-movable in the row direction). As a result, we have developed a measurement device with a pendulum mechanism in the third catenary line that is suitable for that purpose and enables movement in the row direction. Using this, we have developed a flame spread test in normal and microgravity fields. Based on the results of the method experiment and the results of PTV (Particle Tracking Velocimetry) measurement of the flow around the droplet caused by the spread of flame, a new and excellent flame propagation mode by PTV measurement between fuel droplet particles It came to invent the test method of this.

  Thus, the object of the present invention is (1) “(a) a catenary line supporting a catenary line in which a plurality of simulated suspended droplet nuclei are attached in a row in the housing or partition space of the present invention. And (c) droplet generation for generating simulated droplets by supplying liquid fuel to the plurality of simulated suspended droplet nuclei and forming a film of liquid fuel on the simulated suspended droplet nuclei. An apparatus, (d) a tracer particle supply device for supplying a tracer particle cloud to a region where a film of liquid fuel is formed on at least the plurality of simulated suspended droplet nuclei, and (e) an ignition device And a combustion propagation analysis and flame spread measurement device having (f) an optical measurement system and (g) a sequencer for controlling them in or outside the housing or partition space, wherein (d) the tracer The particle feeder is connected to the tracer particle source A region in which liquid particles are formed on the plurality of suspended suspended droplet nuclei by removing coarse particles in the tracer particles in the middle of the tracer particle supply path for supplying the matic, and only particles having a uniform particle size are formed. (D1) Combustion analysis and flame burn spread measuring device characterized by having a tracer particle sorting means for supplying to (1).

In addition, the above object is (2) “the measuring device according to (1) above, wherein the material forming the (a) housing or partition space is a light-transmitting material”. ;
(3) “(b) The catenary support stand supports the catenary line to which the first fixed suspended droplet, the second fixed suspended droplet, and the third moving suspended droplet are attached in order from the side closer to the ignition device. The measuring device according to item (1), characterized in that:
(4) "(b) The catenary line supported by the catenary support base partially supports a part of the plurality of simulated suspended droplet nuclei so as not to perform pendulum movement on the catenary support base, A thin wire of silicon carbide having a thickness of 20 μm or less that supports the remaining suspended suspended droplet nuclei so as to be capable of pendulum movement, and the interval between the plurality of suspended suspended droplet nuclei is adjustable. Measuring device according to item 3);
(5) “The plurality of simulated suspended droplet nuclei are ceramic spheres having a diameter of 30 to 800 μm and can be replaced with the suspended line or the suspended line support base” measuring device";
(6) “(c) The droplet generating device is composed of an air slide stage, a liquid fuel container, a fuel feeding device, a fuel supply pipe, a brass thin tube, and a regulating device, and the solenoid valve is turned ON / OFF by a sequencer. The measuring apparatus according to the item (1), wherein the forward / reverse movement of the air slide stage is controlled.
(7) “The fuel feeder has a microsyringe for injecting fuel guided from the fuel supply pipe to the brass thin tube, and a ball connected to the microsyringe and fed to the simulated suspended liquid droplet via a ball screw. As a measuring device according to item (6) above;
(8) “The measurement apparatus according to any one of the items (1) and (6), wherein the simulated droplet generated in the (c) droplet generation device has a diameter of 150 to 1600 μm” ;
(9) “The tracer particle supply device of (d) has a particle tank for storing silica particles having a volume average particle diameter of 0.05 to 12.0 μm, a particle supply pipe, and a particle cloud discharge pipe, The particle cloud discharge pipe has an air supply pipe for supplying air to the particle supply pipe via an air tank, a regulator, a solenoid valve, and a flow rate controller to form a particle cloud. The measuring device according to item (1), wherein a tip of the discharge pipe is located immediately below a brass thin tube for supplying the fuel.
(10) “Measuring device according to (1) above, further comprising a particle size distribution measuring device in the vicinity of the (d1) tracer particle sorting unit”;
(11) “(e) The ignition device includes an ignition power circuit including a step-up transformer for stepping up a voltage from a DC power source, and an ignition device when a trigger output to the ignition device is directly connected to the ignition device. The measurement apparatus according to (1) above, wherein the electric spark ignition device is controlled by the sequencer via a relay for avoiding noise from the sequencer and other obstacles;
(12) “(f) The optical measurement system includes laser film irradiation means and a high-speed video camera or a CCD digital camera having a CCD array. Measuring device ":
(13) “(g) The sequencer is composed of a CPU unit, an extension output unit, and a power supply unit, constitutes a control device together with a switch box, and controls a stepping motor, a solenoid valve, an ignition device, and the optical measurement system. The measuring device according to the item (1), characterized in that it exists;
(14) "Capsule covering the entire apparatus, capsule lifting means for lifting the capsule to a dropping tower, capsule separating means for separating the capsule from the capsule lifting means and allowing the capsule to fall freely, dropping This is achieved by the “measuring device according to item (1)” further including a microgravity applying unit having a buffer unit that buffers an impact force when the capsule is received.

  Still further, the object is to provide an airflow image transmitted by the optical measurement system using the measuring device according to any one of (15) “(1) to (14)” of the present invention. This information is recorded and recorded while visually checking the monitor image, the recorded airflow image is binarized as necessary, and the binarized image data is It is stored in a memory so that it can be recalled as necessary, and image information processing consisting of emphasis, averaging and / or selection is executed, and the binary image data is graphed. This is achieved by the “flame propagation mode test method by PTV measurement”.

According to the present invention, the behavior of specific fine particles can be analyzed easily and accurately. In particular, the behavior of specific fine particles can be easily and accurately analyzed in consideration of the correlation with similar similar particles by the PTV method. Combustion propagation analysis and measurement of flame spread by overcoming the restrictions imposed on the seed conditions unique to the PTV method, by removing very coarse particles easily and using only fine particles of uniform particle size as a marker for measurement. An apparatus and a method for testing a flame propagation mode of a fuel using the apparatus are provided.
Also, a combustion propagation analysis of liquid fuel suitable for measuring combustion propagation between fuel droplets under zero gravity or microgravity and measurement of flame spread, and a flame spread measurement device, and fuel flame propagation using the device A mode test method is provided. And this technique uses a new and suitable airflow tracking device suitable for analyzing combustion propagation between fuel droplets under zero gravity or microgravity by PTV measurement and measuring flame spread, and the device. This is a test method of flame propagation mode by PTV measurement between fuel droplet particles.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Normal gravity field]
Although the present invention is suitable for performing in a microgravity field, initially considering the difficulty of gravity experiments, after obtaining basic data in a normal gravitational field, the experiments for microgravity tests were focused on the purpose. The present invention was completed. Therefore, here, first, an experimental apparatus used in a normal gravitational field will be described as the basis of the present invention.

[Prototype measuring device]
Fig. 1 shows the outline of the prototype measuring device in the present invention. The apparatus includes (a) a housing or a partition space, (b) a catenary support for supporting a catenary line with a plurality of simulated suspended droplet nuclei attached in a row, and (c) the plurality of simulated pendulums. A liquid droplet generator for supplying liquid fuel to the liquid droplet core and forming a film of liquid fuel on the simulated suspended liquid droplet core, and (d) at least the plurality of simulated suspensions A tracer particle supply device for supplying a tracer particle cloud to a region where a film of liquid fuel is formed on a droplet nucleus, and (e) an ignition device, and (f) in the housing or partition space A combustion propagation analysis and flame spread measurement device having (g) a high-speed video camera of an optical measurement system, (g) a sequencer for controlling them, and (d) on the plurality of simulated suspended droplet nuclei Tracer in the area where the liquid fuel film is formed The tracer particle feeder for feeding the child clouds not shown.

The thickness of the silicon carbide in the measuring device of the present invention is preferably a thin line of 20 μm or less, and the simulated suspended droplet nucleus is preferably 30 to 800 μm in diameter. The interval between the simulated suspended droplet nuclei is adjustable, and the simulated suspended droplet nuclei can be replaced with a suspended line or a suspended line support.
Three fuel droplets were generated at the same time within the initial droplet diameter d0 = 0.8 mm ± 15%. A study was also made on a droplet having an initial droplet diameter d0 = 0.3 mm. Electric spark ignition was used as the ignition device, and the setting was made to minimize the effect of heating on the droplets. The droplet generator is composed of an air slide stage and a flow control valve that controls the air slide stage. As shown in FIG. 2, the first fixed suspended droplet, the second fixed suspended droplet, and the third moving suspended droplet are attached from the side closer to the ignition device. The first droplet is provided to suppress the influence of disturbance caused by spark ignition on the phenomenon. When ignition is performed, the vibration of the pendulum of the third droplet is attenuated. A Y-shaped pendulum is used for the third catenary. The optical measuring device is composed of a backlight and a high-speed camera with an image intensifier, and can record a contour image of a droplet and a self-luminous image of a flame as a continuous image. In order to block external convection, the core is surrounded by an acrylic plate housing.

[Catch line]
In consideration of heat resistance, strength, and mass, silicon carbide wires with a wire diameter of 15 μm are used for the first, second, and third Y-suspension wires. FIG. 3 shows a third Y-shaped catenary line. By processing the silicon carbide wire into a Y shape, it can be moved only in the column direction. In addition, the support part of the catenary line is provided with a ring so as not to resist the pendulum movement, and the reaction force from the support part is minimized. It joined using the instantaneous adhesive agent to the junction part of the silicon carbide wire. In addition, the joint is covered with ceramic to prevent the instantaneous adhesive from burning due to heat from combustion. The device of this example was manufactured with a diameter of about 200 μm so that the mass of the joint would not increase and prevent droplet movement. The length of the Y-shaped suspension line is set to 30 mm in order to increase the period of the pendulum and considering the ease of droplet generation. A ceramic sphere is used at the tip of the catenary line to support the fuel droplets. The diameter of the ceramic is changed according to the diameter of the droplet used for measurement. The diameter of the ceramic is about 200 μm when the droplet diameter is 0.8 mm, and about 50 μm when the droplet diameter is 0.3 mm.

[Droplet generator]
FIG. 4 shows an outline of a droplet generation device in the measurement apparatus of this example. This droplet generating device is composed of an air slide stage, a fuel supply pipe, a brass thin tube, and an adjusting device. The forward / backward control of the air slide stage is performed by turning on / off the electromagnetic valve by a sequencer.

[Micro syringe]
A micro-syringe with a capacity of 250 μ. Was used in this device. Three microsyringes are assigned to the first, second and third suspended droplets, respectively, and are connected to a brass tube by a fuel supply tube. The fuel in the microsyringe is pushed out via a ball screw by a stepping motor.

[Brass tubule from fuel supply pipe]
The fuel pushed out from the microsyringe passes through the fuel supply pipe and is discharged as droplets from the brass thin tube. The fuel supply pipe in the apparatus of this example is made of material SUS304, an inner diameter of 0.4 mm, and an outer diameter of 0.6 mm. In order to generate liquid droplets, a thin tube is necessary, and a smaller liquid droplet can be generated. Therefore, a brass tube with an inner diameter of 0.04 mm and an outer diameter of 0.1 mm is used in this example. The brass tube and fuel supply tube are joined by cutting the brass tube about 10 mm and joining the tip of the fuel supply tube with solder.

[Stepping motor and motor driver]
Table 1 shows the specifications of the stepping motor employed in the measuring apparatus of this example, and Table 2 shows the specifications of the motor driver. Upon receiving the signal from the sequencer, the motor driver drives the stepping motor to push out a certain amount of fuel in the microsyringe.

[Brass interstitial adjustment device]
The photograph of FIG. 5 shows a brass tubule. In order to generate fuel droplets on the catenary line, it is necessary that the brass tube is slightly touching the catenary line. Therefore, in order to adjust the minute distance between the tip of the catenary wire and the brass tube, the device used for adjusting the optical system is improved and used.

[Air slide stage]
Table 3 shows the specifications of the air slide stage. In past apparatuses, a brass capillary was moved using a rotary solenoid to generate droplets. Such a conventional apparatus has problems such as that fine adjustment is not effective, a plurality of fuel droplets cannot be generated at the same time, and that brass capillaries and suspension lines may be damaged. Therefore, in the apparatus of this example, the brass tubule is moved using an air slide stage. The speed adjustment valve can adjust the moving speed of the stage forward and backward.

[Ignition device]
In the device of this example, spark ignition is used as an ignition device, and the ignition device is composed of an electrode, a spark generation circuit, and a DC12V battery. A platinum wire with a wire diameter of 0.2 mm is used for the electrode. The spark distance between the electrodes is about 1 mm, and the tip of the electrode is located about 1 mm from the catenary. Ignition is usually performed only on the first droplet.
FIG. 6 shows the ignition circuit. In this circuit, the primary coil and the secondary coil are electromagnetically coupled. A current is passed while the primary interrupter is connected, and this current is interrupted when the interrupter is disconnected. Since the capacitor is connected in parallel to the interrupter, an electric vibration circuit is formed together with the self-induction of the primary coil. A high voltage is generated in the secondary coil in response to a sudden current change in the primary coil, and a discharge occurs in the spark gap connected to the secondary side. Further, by using a variable resistor on the primary coil side, it is possible to control the ignition energy of the secondary coil, which is actually the case in this example. These two circuits are combined into an ignition circuit, and a 12 V battery is used as the power source.

[Control device]
The control device is composed of a sequencer and a switch box. In the case of the measuring device of this example, devices controlled by the sequencer are a stepping motor, a solenoid valve, an ignition device, and a high-speed camera.

[Sequencer]
The programmable controller consists of a CPU module, extension output unit, and power supply unit. In the case of the device in this example, an additional output unit is added because the number of outputs is insufficient with the CPU unit alone. The sequencer determines the amount of rotation for the motor driver. The number of output pulses is sent by a signal having a frequency corresponding to the rotation speed, and the stepping motor is moved. The program used in this example can change the number of output pulses in units of 10 pulses. The frequency is set to 1/10 of the number of output pulses. By connecting a personal computer to the CPU unit, it is possible to rewrite / read internal programs, monitor programs in real time, and output trigger signals. Also, the set value such as pulse output can be changed by the switch box. Table 4 shows the specifications of the CPU module. The extension output unit outputs a trigger signal to the ignition device, high-speed camera, and solenoid valve.

〔Switch box〕
FIG. 7 shows an outline of the switch box and an internal circuit. Table 5 shows wiring with a sequencer in the measurement apparatus of this example. The switch box is composed of a cable for inputting / outputting signals to / from the sequencer, a switch for sending a trigger to the sequencer, an LED for indicating the status and set value of each device, and a terminal for sending a signal to each device.
With this switch box, the number of output pulses to the stepping motor and the operating frequency can be easily changed. Furthermore, by using LEDs, the current state can be seen at a glance, and operations during measurement can be ensured. In addition, by supplying a pulse output from the sequencer to the piezo element, a sound can be emitted when the switch is pressed, which leads to prevention of erroneous operation.

Furthermore, if the trigger output to the ignition device is directly connected to the ignition device, noise from the ignition device becomes a sequencer and other obstacles, so a relay is provided between the sequencer and the ignition device. The usage of the switch box in the measuring apparatus of this example is as follows. In the present invention, this is merely an example, and of course, other embodiments can be used.
1. To perform trigger output with the switch box, first select the main menu. In the main menu, the “A”, “B”, and “C” buttons can be selected. Each button corresponds to “1” “2” “3” LED. Pressing the button corresponding to the lit lamp turns off.
2. In the switch box, the command to the sequencer of buttons other than “A”, “B” and “C” is changed according to the lighting pattern of the lamps “1”, “2” and “3”. In other words, when only the “1” lamp is lit, the operation that occurs when the “OK” button is pressed, and when the “1” and “2” lamps are lit, the operation that occurs when the “OK” button is pressed. Is different.
3. The main menu settings are divided into seven according to the combination of the three lamps. The lighting pattern used in the apparatus of this example has four settings: only “1” is lit, “1” and “2” are lit, “2” and “3” are lit, and only “3” is lit. 4. When setting the number of pulses to be output to the stepping motor, make sure that only “3” is lit. In the pulse number setting menu, use the “X”, “Y” and “Z” buttons to determine the number of pulses. “X” corresponds to the 10th place, “Y” corresponds to the 100th place, and “Z” corresponds to the 1000th place. The value is added each time the key is pressed. For example, if “X” is pressed 5 times, “Y” is pressed 2 times, and “Z” is pressed 3 times, the number of pulses is 3250. The operating frequency shares this value and is 3250pps.
Furthermore, trapezoidal control is performed with the <set value / 10pps> value as the start / stop frequency and the <set value / 10pps> as the acceleration / deceleration time. The motor operation with the set value is started by pressing the “OK” button.
5. The stepping motor can be operated at a constant speed by turning on the lamps “2” and “3”. In this menu, the motor that has started moving will not stop unless the “QUIT” button is pressed. The constant speed operation menu requires selection of a submenu. The sub menu is the same as the main menu, and the lamps of the corresponding buttons are changed as “X”-“I”, “Y”-“II”, “Z”-“III”.
By turning on the sub menu lamp, the rotation direction and rotation speed of the motor are determined. . The "III" lamp determines the direction of rotation. When this lamp is off, it moves in the forward direction, and when it is lit, it moves in the reverse direction. The “I” and “II” lamps determine the rotation speed. The motor moves at low speed when the “I” lamp is lit, at medium speed when the “II” lamp is lit, and at high speed when both the “I” and “II” lamps are lit. In addition, a safety device that automatically stops when the motor moves too far is installed.
6. When “1” and “2” lamps are lit, measurement can be performed. Each of “X” “Y” “Z” “OK” corresponds to “X” → solenoid valve, “Y” → stepping motor, “Z” → ignition device, “OK” → high speed camera, A trigger is output each time the button is pressed. However, in the case of a solenoid valve, it is turned on at the first time and turned off at the second time. Furthermore, for safety, the ignition device cannot be operated when the stage is moving forward.
7. When “1” lamp is lit, measurement can be performed with one button. Every time the “OK” button is pressed, the stage is advanced, the droplet is generated, the stage is moved backward, the ignition is performed, and a trigger is input to the high-speed camera. During this time, you can reset the measurement by pressing the “QUIT” button. If the droplet does not burn despite being ignited, you can press the “X” button several times before turning on the camera trigger. Can also send a trigger to the igniter.

[program]
In this apparatus example, a ladder language is used as a program language. Ladder language ladder means "ladder" and shows the connection between devices sensuously. It is also a language designed to be easily used by users who do not require deep knowledge of the program. Ladder creation editor is “Ladder Builder” which is included software.
FIG. 8 shows some programs actually used in the measurement.

[High speed camera]
A high-speed camera is preferably used as a means for observing the phenomenon. The high-speed camera used in this example is MEMRICAMci made by NAC Image Technology. Table 6 shows the specifications of this high-speed camera. The shooting speed is 30 to 2000 frames per second, and continuous recording with pre / center / post trigger is possible. Also, live shooting and recording in color is possible. In the actual measurement example, the shooting speed was set to 1000 frames per second and the shot was taken. Images recorded on the high-speed camera were recorded on a video tape recorder after the experiment was completed, and used as image data.

[Image Intensifier]
In the apparatus of this example, since the emission of the blue flame is weak when only the high-speed camera is photographed, it is impossible to photograph the flame spread phenomenon. Therefore, the image was photographed by amplifying the light by attaching an image intensifier (II) to a high-speed camera. In order to synchronize with the high-speed camera, the strobe output from the high-speed camera was input to II.

FIG. 8 shows a ladder program actually used in the apparatus of this example.
In addition, as a specification for high-speed video cameras, II adopted ILS made by NAC Corporation. Tables 7 and 8 show the specifications of II.

[Recorder]
Video captured by a CCD camera or high-speed video camera can be recorded by a video cassette recorder. When recording on the video cassette recorder, the signal sent from the camera is branched for monitoring and recording by the connector, so that recording can be performed simultaneously while checking on the monitor.

The measuring device of this example can be used as follows.
1． Wire the equipment and connect the sequencer and switch box with a cable. Connect the PLS1 output of the switch box to the motor driver, connect OUTPUT1 to the solenoid valve, OUTPUT2 to the high-speed camera, OUTPUT5 to the ignition device, and INPUT2 to the safety device of the fuel supply device.
2． Fill the compressor with air and check the operation of the air slide stage. (Since the stage is not moved for several hours, it may move forward rapidly.) To check the operation of the slide stage, press the “A” button and “B” button of the switch box once, and the main menu lamp “1” , Confirm that “2” is lit and press the “X” button. Similarly, when the advanced stage is moved backward, the “X” button may be pressed. Also, adjust the speed control valve as necessary.
3． Fill the microsyringe with fuel and confirm that droplets are generated from the tip of the brass tube.
If no droplet is produced, replace the brass tube. Be careful when the fuel has not been used for a long time, because the fuel from the copper tube to the SUS tube evaporates and droplets are not generated.
Four. The microsyringe is set in the fuel pusher and the number of output pulses to the stepping motor is determined to set the droplet diameter. To set the number of output pulses, the main menu lamp of the switch box and “3” of the main button are lit. In this state, by pressing the “X”, “Y”, and “Z” buttons, the number of output pulses is determined, and a droplet having a predetermined diameter is generated.
Five. Align the position of the tip of the catenary line in the row direction. The stage is advanced to adjust the position of the brass tubule and the tip of the catenary wire, and a droplet is generated on the catenary wire. In addition, the spark interval and the position of the suspended droplet are adjusted to ignite the suspended droplet. And it confirms that a droplet burns. When the stepping motor speed is set in (4), the stepping motor can be moved at the set value by pressing the “Y” button with the “1” and “2” lights on the main menu lamp. it can. Further, ignition is performed by pressing the “Z” button in this state. However, for safety reasons, when the stage is moving forward, the trigger is not activated and the “0” lamp is lit to notify the error.
6． Set up the high-speed camera. Switch the shutter setting knob to Lock, and check that the shutter setting is OPEN on the monitor. Set the trigger to END and set the shooting speed to 1000 shots per second. Then, adjust the height of II and high-speed camera and connect. Darken the room and focus the II and high-speed camera.
7． Set the focus of II to the catenary line. Brighten the backlight gradually and adjust the gain of II. In the case of measurement using the apparatus of this example, the gain value of II was set to 50-60.
8． The device was covered with an acrylic plate to prevent wind from entering to form a housing. After everything is ready, refill the syringe with fuel before starting the measurement.
9． Start measurement. With the switch box main menu lamps “1” and “2” lit, move the stage forward with the “X” button, generate droplets with the “Y” button, move the stage backward with the “X” button, “Z” ”Button to ignite the droplet, and after the burning of the droplet is finished, press the“ OK ”button to trigger the high-speed camera and take a picture of the phenomenon.
Ten. When the "OK" button is pressed with only the main menu lamp "1" on the switch box turned on, each time the button is pressed, the stage is advanced-> droplets are generated-> the stage is retracted->ignition-> high-speed camera Trigger input is executed.
11． The captured video is stored in a video cassette recorder for analysis.

[Measurement method]
The measurement can be performed as follows.
1. Check the video saved in the video cassette recorder.
2. The time code is inserted in the shot video in advance. Using that time code,
Determine the moving distance for each frame (0.033 ms) from the stationary state of the third droplet and determine the speed.
3. When determining the travel distance, determine the origin accurately and measure the distance for each frame on the monitor with a caliper.
4. Measure the distance in the x direction, the initial droplet diameter, the droplet spacing, and the spreading time.

[PTV measurement]
The basic features of PTV (particle image velocimetry) are described. In a PTV system instrument, tracer particles are added to the flow. The tracer particles are illuminated twice at a minute time interval in the flow plane. The scattered light from the tracer particles is recorded in successive frames by the camera. Tracer particle displacement between light pulses is obtained by image processing of PTV images. Excellent post-processing is required to handle the enormous amount of data obtained by PTV.

  FIG. 9 shows a typical apparatus example for recording PTV images in a wind tunnel experiment. Fine tracer particles are added to the flow and the cross section in the flow is illuminated twice by the laser sheet. The time interval between two pulses depends on the average flow velocity and the image magnification. It is assumed that the tracer particles move according to the local flow velocity between the two illuminations. From the digitized PTV image, the position information of each particle image, and incidental information such as brightness and size are acquired using a binary image, and the movement of the particle is analyzed. Using the fact that the moving direction of the particle image does not change greatly over a plurality of times and the relative positional relationship with surrounding particle images does not change greatly, the same particles over a plurality of times are tracked. The component in the light sheet of the local flow velocity vector, that is, the two-component velocity vector is obtained in consideration of the time difference between the two illuminations and the magnification of the image. This process is repeated for all inspection areas of the PTV image. The following reports on flow field visualization research have been made.

  Fukano et al. (Y. Fukano, H. Hisaki, S. Kida) worked on elucidating the flow field in the combustion chamber in order to understand the effect of the flow in the combustion chamber of a spark ignition natural gas engine on the engine performance. , T. kadota,: Flow characteristics in a combustion chamber of a spark-ignition natural gas engine, in Japanese, Journal of JSME, B, 64, (1998), 272-278). A high-resolution flow velocity measurement method that applied an image intensifier to the PTV method using a CCD camera was constructed, and the flow field in the combustion chamber was measured by changing the measurement cross section and the measurement crank angle. Tomimatsu et al. Showed a method for measuring PIV (Particle Image Velocimetry) in a spray combustion system. In addition, the spray combustion field was comprehensively observed by observing the structure of the spray combustion flame simultaneously with the velocity measurement (S. Tomimatsu, N. Fujisawa, and A. Hosokawa. Research on PIV measurement, in Japanese, The Visualization Society of Japan, 20, (2002), 389-392).

  As described above, there are many reports of visualization in the combustion device for PIV and PTV measurement. However, there is no report on the transient flow around the droplet in the spread of the fuel droplet row. Usually, in the gravitational field, the third droplet moved away from the second droplet before the third droplet burned out, so the flow caused by the spreading of the first and second droplets was the third liquid. It is thought to move the drop. Therefore, in the present invention, as a preliminary experimental example, the flow field around the third droplet at the time of spreading the flame was visualized. The experimental arrangement used at that time is shown in FIG.

[Example of measuring apparatus of the present invention]
The outline of the whole example of the measuring apparatus of this invention is shown in FIG. This PTV measuring device is a device in which a copper vapor laser as a light source, an optical system, and a tracer particle generator are newly mounted on the device shown in FIG. The copper vapor laser has a maximum output of 4 mJ / pulse and a pulse width of 10 to 40 ns. The laser light emitted from the copper vapor laser passes through the cylindrical lens to form a sheet, is reflected by the reflecting mirror, and then radiates upward from below the droplet. The laser sheet width in the visualization range is 0.2 mm. FIG. 11 shows the visualization range. The visualization range is a range surrounded by a dotted line in the drawing including the second droplet and the third droplet. In the PTV measurement using the device of this example, the third catenary line was not installed. The dimensionless droplet spacing l between the first and second droplets is 5.5 and the initial droplet diameter do is 0.8 mm. For optical measurement, the image intensifier was connected in two stages and the scattered light from the tracer was photographed with a high-speed camera. The exposure time of the high-speed camera is 900 μs, and the copper vapor laser irradiation time is 10 to 40 ns. The shooting speed was 1000 fps. In order to block convection from outside during measurement, the experimental part was surrounded by an acrylic plate to form a housing.

[Time chart]
The synchronization box and the wiring of each device are shown in FIG. 12, and the time chart is shown in FIG. In FIG. 13, (1) and (2) pull-down trigger signals are input to the synchronization box by the trigger switch. A trigger signal is input to the high-speed camera via the synchronization box. (3) The high-speed camera that receives the trigger signal takes an image at 1000 fps and outputs the strobe signal to II. The start time of the trigger signal and the strobe signal is the same. II receiving the strobe signal opens the shutter for 900μs with a delay of 0.04μs. (4) (5) The strobe signal is also output to the copper vapor laser through the synchronous box. The copper vapor laser emits a laser with an irradiation time of 10 to 40 ns with a delay of 0.04 μs. At that moment, II and high-speed cameras can receive the scattered light from the tracer particles.

[Copper vapor laser]
FIG. 14 shows an overview of the copper vapor laser, and Table 9 shows the specifications of the copper vapor laser. Since the video sensor is exposed by scattered light from minute tracer particles, a high-power light source for particle illumination is required. This is because there is a contradiction that if a large particle is used in order to obtain a better light scattering efficiency, the flow cannot be accurately followed. In many applications, a reasonable combination is used taking into account the laser power and tracer particle diameter requirements. In the present invention, a high-power copper vapor laser was selected to make the tracer particles as small as possible.

[Tracer particles]
Table 10 shows the specifications of the tracer particles used in the apparatus of this example. The diameter of the tracer particles with good followability to the fluid was selected to capture the transient flow of the spread of the flame. In addition, because it is a phenomenon accompanied by combustion, it was necessary to select a substance that would not cause the tracer particles to burn off due to the heat of combustion. SiO2 particles with a particle size of 1.5 μm and a density of 2.0 g / cm3 were used.

[Tracer particle feeder]
An outline of the tracer particle generator is shown in FIG. There are various methods for supplying the tracer particles. At first, an attempt was made to eject tracer particles with a large particle size into the experimental apparatus using compressed air. However, the average tracer particle diameter at the measurement unit was as large as 100 μm, and the fluid followability deteriorated. A tracer particle generator was developed. The tracer particle generator floats tracer particles using the vibration of an ultrasonic device. After that, the tracer particles are sent out by the fan, passed through the gravity classifier, and then supplied into the experimental device. As an inevitable general tendency of fine particles of this type, the tracer particles have a larger proportion of particles having a medium particle size (particle size near the number average particle size), and the smaller the particle size, And, the larger the size, the smaller the content of the mountain-shaped particle size distribution (not always showing the ideal Gaussian distribution, but often the irregular mountain-shaped), Mainly large particles. After passing through the gravity classifier, this large particle part was removed, and the tracer particle diameter averaged 2.9 μm.

[Gravity classifier]
An outline of the gravity classifying apparatus is shown in FIG. Tracer particles that are micronized and floated by the vibration of ultrasonic waves are supplied by a supply fan to the inside of the experimental device through a gravity classifier. At that time, particle size
Only particles of about 2.0 μm were taken out and large particle diameters were removed. A large particle size has a large mass (since the mass is proportional to the cube of the particle size, a small difference in particle size results in a large difference in mass), so it settles while passing through a long channel. On the other hand, the small particle size is supplied to the inside of the experimental apparatus because it does not settle in a long channel. The dimensions of the flow path are 1650 mm in the flow direction, 80 mm in length, and 40 mm in width
It is preferably about ± 20%.

[Tracer particle diameter measurement method]
In order to confirm whether a tracer with good followability was supplied to the fluid, the diameter of the tracer particles supplied from the tracer supply device was measured. Measurement was performed using a particle size distribution measuring apparatus and a microscope.

[Particle size distribution analyzer (LDSA)]
The laser light scattering type particle size distribution measuring device measures the particle diameter from the relationship between the scattering angle dependence of the scattered light intensity and the particle diameter, using the scattering angle of the light scattered by the particles in the parallel light flux. It is a device that uses Hunhofer diffraction. Details of LDSA are shown in Table 11. A He-Ne laser (wavelength 632.8 nm, red) is used as the light source, and the beam output from the laser becomes a parallel beam with a diameter of about 6 mm by a collimator. The beam is focused through the lens to the center of the sensor. The sensor is concentric, and the scattering intensity corresponding to the scattering angle can be measured sequentially from the inside to the outside of the sensor. When a particle of a certain diameter enters the laser beam, various scattering patterns occur depending on the size of the particle diameter. When the particle diameter is small, the scattering angle is large, and when the particle diameter is large, the scattering angle is small. When several particles are scattered at the same scattering angle, the scattered light is collected on the same circumference from the center of the sensor.

[Microscope equipment]
A prepared preparation with a scale was placed at the supply port of the tracer particle generator, and the tracer particles were attached and measured with a microscope.

[Tracer particle measurement method]
Tracer particles were measured in the following sequence.
1． Warm up the copper vapor laser in advance. Open tap faucet and drain cooling water. Open the neon gas plug and turn on the copper vapor laser start switch. At that time, pay attention to the lighting lamps and make sure that there are no abnormalities. After turning on the start switch, wait about 1 hour until the laser is ready for use.
2． Perform wiring for each device. Connect the PLC and switch box cables, connect the PLS1 output of the switch box to the motor driver, OUTPUT1 to the solenoid valve, OUTPUT2 to the high-speed camera, and OUTPUT5 to the ignition device.
3． Fill the compressor with air and check the operation of the air slide stage. To check the operation of the slide stage, press the “A” button and “B” button of the switch box once to confirm that the main menu lamps “1” and “2” are lit. The stage can be advanced by pressing the “X” button. Similarly, when the advanced stage is moved backward, the “X” button is pressed. The speed adjustment valve adjusts the forward / backward speed of the stage.
Four. Fill the microsyringe with fuel and confirm that droplets are generated from the tip of the brass tube. If no droplets are generated, replace the brass tubule. Also, it is desirable to replace all brass caps once a week.
(Note) Use extreme caution when filling the fuel to prevent foreign matter from entering the microsyringe.
Five. Set the microsyringe in the fuel extrusion device and set the rotation amount of the stepping motor so that droplets with a diameter of 0.8 mm can be generated. To set the rotation amount of the stepping motor, press the “C” switch on the main button of the switch box main menu lamp so that only “3” is lit. In this state, the number of output pulses is adjusted by pressing the “X”, “Y”, and “Z” buttons.
(Note) Number of steps of syringe stepping motor “X”: 10 steps (example) 20 steps: “X” 2 times-droplet diameter 0.5 mm
"Y" ... 100 Step 50 Step ... "X" 5 times-Droplet diameter 0.8mm
「Z」 ・ ・ ・ 1000 steps
6． Adjust the position of the catenary line. After the position is set, the position of the brass tubule is adjusted and a droplet is actually generated on the catenary line. Subsequently, the position of the ignition line is adjusted to confirm that the first suspended droplet is ignited and burned. When the rotation amount of the stepping motor is set, the stepping motor can be operated by pressing the “Y” button with the main menu lamps “1” and “2” lit. Furthermore, ignition is performed by pressing the “Z” button in this state.
7． Darken the room and oscillate copper vapor laser. Make sure that the laser is in a stable state. At that time, the laser sheet is adjusted using incense smoke.
8． Operate the tracer particle generator and adjust the particle supply fan so that the tracer particles can be sufficiently supplied into the experimental device. At that time, the supply amount of tracer particles is confirmed using a light source of a copper vapor laser.
9． Set up the high-speed camera and II.
(Note) When using II, be sure to darken the room so that it does not receive strong light.
Ten. Cover the device with an acrylic plate. If the experiment is not performed for a long time, the fuel from the brass tube to the SUS tube evaporates. Therefore, after all preparations are completed, the fuel in the syringe is filled again before starting the experiment.
11． When starting the experiment, start the tracer particle generator and irradiate the copper vapor laser. With the switch box main menu lamps “1” and “2” lit, move the stage forward with the “X” button, generate droplets with the “Y” button, move the stage backward with the “X” button, “Z” The first droplet is ignited with the button, and at the same time, a trigger is sent to the high-speed camera for shooting.
12． Store the captured images on a jazz drive and 8 mm tape. Then, TIF images are converted to BMP images and analyzed with PTV analysis software.

[Measurement method]
The flow field was analyzed using fluid measurement software "Flow-PTV" (Library Inc.).
1． The photographed image is converted from a TIF image to a BMP image and analyzed using PTV measurement software.
2． Measurement and tracking decision conditions in PTV measurement Grid spacing ... X-10
Y-10
Vector parameter: Set 10x mask, range, scale, and number of frames.
3． The items of the object luminance range and the object luminance area are adjusted. When performing PTV measurement of very fine tracer particles, turn on the special binarization item. Save as serial number file and text data.
(Note) Pay attention to the number and direction of particles, noise, and the movement of particles in serial number photographs.
Four. The initial velocity around the second droplet before the spreading of the flame is confirmed in advance from the text data. At that time, the average value of the velocity vector in the x direction and the velocity vector in the y direction was used as the initial velocity.
Five. To read the x-direction and y-direction velocities of each particle (couple number) in each image scene from text data, place the mouse on the vector start point of each particle, right-click, and check the particle couple number. The couple number and the couple number of the text data are matched to obtain the velocity in the x and y directions.
6． The relationship between the x-axis flow velocity and the dimensionless distance was investigated over time.

[Microgravity field]
The fuel droplets in spray combustion such as diesel engines and gas turbines are very small, so the effect of convection is small and a phenomenon close to spherical symmetry will occur. On the other hand, since it is difficult to conduct a combustion experiment using small fuel droplets, measurements are often made on relatively large fuel droplets with a diameter of about 1 mm. When the diameter of the fuel droplet is large, it is easily affected by convection. In order to reduce this effect and simulate the above phenomenon, it is necessary to perform measurement in a microgravity environment. In the present invention, measurement is performed using a droplet having a diameter of about 0.8 mm. In consideration of the movement of the third droplet due to the spreading of the flame, the measurement was performed in a microgravity environment in order to remove the complexities of phenomena due to natural convection and the restoring force of the pendulum due to gravity.

[Experimental device]
An outline of the entire microgravity measuring apparatus is shown in FIG. The microgravity measuring device has been improved so that it can be mounted on a falling capsule. The added devices are microgravity detection sensor, CCD camera, high pressure air tank and regulator. The measurement was performed using a drop tower (microgravity time 1.1 s). The optical measuring device consists of a CCD camera and a backlight, and recorded the contour image of the droplet and the self-luminous image of the flame as a continuous image. The falling capsule is lifted up to the top of the dropping tower by the winch. Droplets with an initial droplet diameter of 0.8 mm were generated at the top of the drop tower and started to fall. The microgravity detection sensor detects the microgravity state and sends a trigger signal to the sequencer. The sequencer activates the igniter and the droplets start to burn. The behavior of the third suspended droplet was observed.

[Fall tower]
In order to realize a microgravity environment, the falling tower in the Nihon University production engineering high-tech research center was used. The falling tower is a device that realizes a microgravity environment by the free-fall method. The falling tower owned by the University is a method of falling in the atmosphere. FIG. 18 shows a full view of the fall tower. The falling tower is 8.6m in total height, 5.4m in free fall distance, 0.9m in the deceleration part, and can realize a microgravity environment of about 1.1 s. The two guide wires inside the falling tower are installed vertically to prevent the capsule from rotating during lifting and landing. The capsule is raised and lowered by a winch. The winch is installed on the side of the drop tower, and the wire is connected to the capsule detaching device via two smoothing wheels attached to the top of the drop tower. In addition, a guide rail for fixing the capsule separating device is installed at the top of the dropping tower. A limit switch is attached to the guide rail, and the winch stops automatically when the capsule separating device enters the guide rail and the limit switch is activated. In order to efficiently absorb the drop impact of the capsule, the sponge mat in the drop tower bottom deceleration chamber is arranged to have an air damper structure.

[Falling capsule]
FIG. 19 shows an outline of the falling capsule. The falling capsule has a double structure of an outer capsule and an inner capsule, and the measuring device is mounted on the inner capsule. Before falling, the inner capsule is located at the top of the outer capsule, and the bottom of both is 150 mm away. While the capsule is falling, the outer capsule receives air resistance, so the falling speed is slower than that of free fall, and both gradually approach and come into contact when landing. With this structure, the air speed of the inner capsule equipped with the experimental device is extremely low, and the deviation from free fall due to air resistance can be reduced. The gravitational acceleration inside the inner capsule is about 10-4 G0.
An aluminum alloy was used as the structural material of the outer capsule. It has a diameter of 1.0 m, a total length of 1.4 m, and a mass of about 100 kg. A wooden truncated cone is attached to the bottom to reduce the air resistance when dropped. At the bottom of the inner side, there are a sponge for absorbing the impact when the inner capsule collides and seven suction cups for preventing splashing. There are two working windows on the outer wall of the outer capsule so that the measuring device in the inner capsule can be operated without taking out the inner capsule from the outer capsule.
The inner capsule on which the device is mounted is composed of a top plate, a bottom plate and four pillars with a diameter of 0.8 m. On the top board are two CCD camera image output terminals (BNC connector), AC100V supply terminals (Connector1, 4Pin), and droplet generation switch terminals (Connector2, 8Pin). BNCconnector is a terminal for outputting video to a video cassette recorder, and it is connected to an external video recorder even when dropped. Connector1 and Connector2 are disconnected when dropped. Since power is required even during the fall, power was supplied using an Omron backup 100 VAC power source. A nitrogen cylinder is mounted on the bottom plate, and the charged nitrogen is used to move the air slide stage forward and backward. In addition, two octagonal platforms are installed on the inner capsule so as to sandwich the measuring device, and a device is placed on each of them.

[[Capsule separation device]]
[Drop cutting device before change]
FIG. 20 shows an outline of the capsule separating apparatus. This separating device is composed of an air cylinder, an electromagnetic coil, a solenoid valve, and an air tank. To detach the capsule, detach the capsule by pulling out the two pins from the suspension plate attached to the capsule. The weight of the capsule is supported only by pin A, and pin B is a safety pin. The pins are operated on the control panel beside the drop tower.
FIG. 21 shows the switch arrangement of the control panel. The switch on panel 1 is for safety devices. Turn on SW 1P and SW 1S, and release the safety device with the reset button. Panel 2 is a control switch for the separation device, and is set to the RELEASE side during measurement, and is usually set to the SET side when working in a drop tower. SW 5P on panel 5 is a DC 5V power supply switch. When turned on, power is supplied to panel 1. The two buttons on panel 6 are switches for disconnecting the falling capsule. When the first button is pressed, the electromagnetic coil of the disconnecting device works and pin B is released. Pressing the second button opens the solenoid valve, and the air cylinder is activated to release pin A. During measurement, the capsules are separated by pressing both buttons simultaneously.

[Falling device after change]
FIG. 22 shows the structure of the separation device after the change. In the early fall method, the separation vibration moved the third catenary line into the microgravity, so the conventional separation device was significantly changed. The current separation method is a structure in which chemical tape is heated by nichrome wire in order to minimize vibration during separation. The chemical tape (white) was selected in consideration of the weight of the capsule to be lifted, the heat of the nichrome wire, and the ease of experimentation. FIG. 23 shows how to tie. A knot was also used to lift the outer and inner capsules using chemical tape. Moai knots were safe because the knots were tightened using the weight of the capsules.

[Method of operation]
1. Perform wiring for each device. Connect the drop device, power supply, CCD camera, and video cassette recorder, and open the nitrogen cylinder plug.
(Note) The maximum filling pressure of the nitrogen cylinder is 120 kgf / cm2.
2． Perform the same settings and operations as in Experimental Methods 2-6 in the PTV ground experiment.
(Note 1) In the PTV ground experiment 3, the compressor was not filled in the microgravity experiment.
(Note 2) The adjustment method of the ignition line position in the case of PTV ground experiment 6 is different because the structure of the ignition line is changed in the microgravity experiment.
3． As soon as the experimental apparatus is adjusted and set, insert the inner capsule into the outer capsule and lift it with a winch.
Four. Place a sponge mat for shock absorption in the deceleration chamber at the bottom of the fall tower, and raise the fall capsule to the top of the fall tower using a winch.
Five. After confirming the safety of the falling tower, turn on the switches on the control panel in the following order. (Description and arrangement of each switch is shown in FIG. 21)
6． Panel 1 SW 1P, SW 1S → SW 1R RESET → Panel 5 SW 5P → Panel 2 SW
Set 2L to RELEASE side.
7． Droplets are generated and attached to the catenary line by remote control.
(Note) In microgravity experiments, droplets are generated just before the drop at the top of the drop tower.
8． After confirming that the droplet has reached the target size, video cassette recorder recording is performed.
9． As soon as all the drops are ready, the capsule 6 is separated by simultaneously pressing the two release buttons SW 6B and SW 6R on panel 6.
Ten. Analyzes video recorded on a video cassette recorder.

[Measurement method]
1. Check the video saved in the video cassette recorder.
2. When determining the movement distance of the third droplet, determine the initial position accurately and measure the movement distance on the screen with calipers. Multiply the distance on the screen to find the actual distance traveled.
3. The relationship between the dimensionless distance in the x and y directions and time was used as data.

[Experimental parameters]
The equivalent droplet diameter d0, dimensionless droplet spacing s, and dimensionless movement distance Δx are defined below.
[Equivalent droplet diameter]
As the droplet diameter, the equivalent droplet diameter defined by d0 = (a2b) 1/3 was used, using the minor axis a and major axis b of the droplet. The initial diameter of the droplet row was expressed as d0 using the average value of the second initial droplet diameter and the third initial droplet diameter.

[Dimensionless droplet spacing]
The distance between the second droplet and the third droplet was divided by the average value d0 of the second initial droplet diameter and the third initial droplet diameter to obtain a dimensionless droplet interval s.
[Dimensionless travel distance]
The amount of movement of the third droplet is based on the position before combustion, and the amount of movement from there is divided by the average value of the initial diameter of the second droplet and the diameter of the third initial droplet. .

[Burn spread induction time]
Ignition was defined as the case where flame emission was confirmed around the fuel droplet. The flame spread induction time is the time required for the flame spread from the second droplet to the third droplet. A Fourier number represented by 20 / F at l = was used for the flame spread induction time. The temperature propagation rate () P / a C λ ρ =, the constant-pressure specific heat PC was the air value at 300 k, and the density 3 kg / m ρ was the air value at 300 k.

[Measurement conditions]
Measurements were performed in normal and microgravity fields. In a normal gravitational field, the initial droplet diameter d0 was 0.8 mm and 0.3 mm, and the behavior of the third suspended droplet was observed by changing the droplet interval. In the PTV measurement, the dimensionless droplet interval s was fixed at 5.5. The initial droplet diameter d0 was 0.8 mm, and the flow field around the second and third droplets was visualized. In the microgravity field, the initial droplet diameter d0 was 0.8 mm, and the behavior of the third suspended droplet was observed.
Positive heptane was used as the fuel, and atmospheric pressure air was used as the atmosphere. The air temperature was 300 ± 3K.

[[Application Example of Measurement Method of the Present Invention]]
Such a measuring method of the present invention can be applied to the following consideration and analysis of various items.
[Quasi-stationary theory of combustion]
By understanding the quasi-stationary theory of single droplets, we can better understand the considerations of combustion and droplet movement in a fuel droplet train. Here, the quasi-stationary theory of a single droplet will be described.
In combustion of fuel droplets, diffusion of fuel vapor and air (or oxygen) and heat transfer dominate the phenomenon. Considering these points, when one model is constructed, it is as shown in FIG.
That is, a droplet with a radius of 1 R evaporates by receiving heat from the outside such as a flame surface and blows out fuel vapor. The fuel vapor diffuses outward and reacts with the air diffused from the outside to the inside, forming a flame front. Therefore, on the flame surface, the fuel vapor and oxygen concentrations are zero and the temperature is the flame temperature fθ.

[Mass transfer of fuel vapor]
The fuel vapor concentration is C _F kg / kg if 1 kg of fuel mixture is contained in the fuel vapor F kg C, and the amount is ρC _F if the mixture density is 3 kg / m ρ. . The fuel vapor is saturated on the droplet surface and is considered to diffuse outward due to the concentration difference. Therefore, if the diffusion coefficient is D m ² / s, -D · d (ρC per unit time and unit area _F ) / dr fuel vapor is molecularly diffused. Furthermore, the unit time the fuel vapor blowout velocity u is given, the addition of both because per unit area fuel vapor .rho.c _F u moves with convection outward _{ρC F uD · d (ρC F} ) / dr
Originally, the blowing speed moves the entire mixture outward, so the amount of moving steam per unit time and unit area is ρu. So if you put them equal,

  It becomes. Let the inside of the fuel vapor layer be represented by subscript 1 and apply Equation (1). If the amount of fuel evaporation per unit time is w kg / s

It becomes. If the region outside the flame surface is represented by subscript 2, oxygen with a concentration of OX C diffuses inward by D ₂ · d (ρ ₂ C _OX ) / dr. However, ρ ₂ C _OX u is hindered by the outward flow. If the oxygen in the flame surface reacts with the fuel vapor to become zero, if the theoretical ζ times oxygen is required

となる。これが物質移動の式である。境界条件は火炎面上でとると、

It becomes. This is the mass transfer equation. If the boundary condition is on the flame surface,

として式（３）に代入して

Substituting into equation (3) as

となり、図２５に濃度分布の概要が示される。

FIG. 25 shows an outline of the density distribution.

[Heat transfer]
If the temperature inside the flame surface is θ ₁ , heat of λ ₁ dθ ₁ / / dr is transmitted inward per unit time and unit area, and C _P1 ρ ₁ u (θ ₁ − θ _W

となる。ただしθ_Wは液滴表面温度である。
火炎面より外側の領域においては燃料の発熱量をH とすれば，燃焼反応による全発熱量wH のうちからwL を差し引いた( ) w H L . が外側に向かって伝導しかつ，吹き出し流Ｃ_Ｐ２ ρ_２u(θ₁-θ_∞)によって移動するから

It becomes. Where θ _W is the droplet surface temperature.
If the calorific value of the fuel in the region outside the flame front and H, minus wL from among all calorific wH by combustion reaction () w HL. Conduction vital outward, balloon stream C _P2 Because it moves by ρ ₂ u (θ ₁ -θ _∞ )

となる． θ∞ は遠方の温度である．これらが熱移動の基礎式である．境界条件は火炎面内側に対して

It becomes. θ∞ is the distant temperature. These are the basic equations for heat transfer. Boundary conditions for the flame front

火炎面外側に対して

Against the outside of the flame

となる。この解は

It becomes. This solution is

となる。図３６に温度分布の概略を示す。
式（４）においてr ＝ ∞として

It becomes. FIG. 36 shows an outline of the temperature distribution.
In equation (4), r = ∞

近似式を使えば

If you use an approximate expression

燃焼速度定数Ｃ_bは

The burning rate constant _Cb is

で定義されdt 時間にdＲ_１だけ液滴の半径が小さくなったとすれば液滴の密度ρ_f としてdt 時間の蒸発量 ｗ dtは

If the radius of the droplet becomes smaller by dR _{1 in} dt time, the evaporation density w dt in the dt time is expressed as the droplet density ρ _f

であるから

Because

となり燃焼速度定数から蒸発量が求まる。

The evaporation amount is obtained from the combustion rate constant.

[[Gravity field]]
[Definition of mode]
Since it is considered that the movement of the third droplet changes depending on the spreading form, in the present invention, the spreading form is defined as follows.
FIG. 27 is a conceptual diagram of the flame spread mode. Mode 1 is when the third suspended droplet is wrapped in the flame of the second suspended droplet, and the flame spreads. In the case of mode 3, the flame of the third suspended droplet was generated independently of the flame of the second suspended droplet, and in mode 4, the third suspended droplet did not spread. It was a case.

[[Droplet diameter 0.8 mm]]
[Relationship between dimensionless droplet interval and mode]
FIG. 28 shows the relationship between the dimensionless droplet interval s and the mode when the initial droplet diameter is 0.8 mm. s = 1.0 to 3.0 indicates mode 1, s = 2.5 to 4.0 is mode 2, s = 3.5 to 7.0 is mode 3, and s = 6.5 and above did not spread.

[Droplet behavior]
FIGS. 29 to 32 show an image of the flame spread behavior and the behavior of the third droplet with time. The time t when the flame spread over the second suspended droplet was set to 0.0 s. The broken line in the photograph shows the initial position of the third droplet. The direction away from the second droplet was the positive direction, and the approaching direction was the negative direction. In the figure, tig indicates the time when the third droplet spreads.
Figure 29 shows the case of mode 1. The dimensionless droplet spacing s is 2.8. In the image at t = 0 s, the second droplet spreads out at the moment the first droplet ignites. In the image at t = 0.1 s, the second and third droplets repel each other and the third droplet begins to move in the positive direction. At t = 0.15 s, the third droplet moves further in the positive direction, and the moving distance in the positive direction becomes maximum. At t = 0.2 s, the movement turns in the negative direction due to the restoring force of the pendulum. At t = 0.35 s, the movement turns in the positive direction. The maximum value of the travel distance at t = 0.45 s was larger than the maximum value of the travel distance at t = 0.15 s. At t = 0.5 s, the movement turns negative again.

  FIG. 30 shows the case of mode 2. The dimensionless droplet spacing s is 3.4. In the image at t = 0 s, the second droplet burns out at the moment when the first droplet is ignited. In the image at t = 0.1 s, the second and third droplets repel each other and the third droplet begins to move in the positive direction. In the image at t = 0.2 s, the second and third droplets repel each other, the third droplet moves in the positive direction, and the moving distance in the positive direction is maximized. At t = 0.25 s, the movement turns in the negative direction due to the restoring force of the pendulum. At t = 0.35 s, the movement turns again in the positive direction. After t = 0.55 s, the third droplet came out from the visualization range and measurement was not possible. In Mode 2, the reason for the movement of the third droplet is the same as in the case of s = 2.0, but the point that should be noted is that the forward movement distance after the spread of the flame is large.

  FIG. 31 shows the case of mode 3. The dimensionless droplet spacing s is 5.7. In the image at t = 0.1 s, the third droplet moved in the positive direction at the moment when it spread from the first droplet to the second droplet. From t = 0.1 s, it can be inferred that the third droplet is moving in the negative direction due to the restoring force of the pendulum and the effect of natural convection. In the image at t = 0.4 s, the second and third droplets repel each other and the third droplet moves in the positive direction due to the flow of burned gas generated by combustion.

  FIG. 32 shows the case where the third droplet did not burn and spread. The dimensionless droplet spacing s is 7.0. At t = 0.1 s, the third droplet moves in the positive direction under the influence of the expansion flow caused by the spreading of the second droplet, and thereafter vibrates. Compared to s = 5.7, the moving distance in the negative direction is increased. This is thought to be due to the strong influence of natural convection.

[Movement of fuel droplets before spreading (in case of heptane)]
FIG. 33 shows the relationship between the dimensionless droplet interval and the positive direction dimensionless maximum moving distance Δxmax1 before the spreading of the flame occurs. Δxmax1 represents the degree of force exerted on the third droplet by the flow of the fuel vapor and the burnt gas generated initially by the second droplet. Below s = 5.0, Δxmax1 was set to zero because the spread of the flame occurred before the third droplet moved. In addition, when the third droplet burns and spreads while moving in the positive direction, it is represented by a white circle and the position where the third droplet burns and spread is designated as Δxmax1. If no spread from the first droplet to the second droplet occurs, it is not added to the plot. Δxmax1 decreases from s = 5.5 to s = 6.5. It is considered that the third droplet is moved by receiving a drag force due to the thermal expansion flow generated by the spreading of the first droplet, and further the thermal expansion flow generated by the spreading of the second droplet is added. At s> 5.5, Δxmax1 decreases with increasing dimensionless droplet spacing because the thermal expansion flow of the first and second droplets decreases with increasing dimensionless droplet spacing and This is thought to be caused by the spreading of the second droplet after the maximum movement of the third droplet due to the thermal expansion flow of the droplet takes a negative value and the direction of movement changes in the negative direction. That is, it is considered that Δxmax1 is determined by the position and velocity of the third droplet at the time when the second droplet spreads and spreads.

[Movement of water droplets by combustion (for water)]
In order to investigate whether the third droplet evaporates due to the heat of the flame of the second droplet, and the drag experienced by the third droplet at s <5.5, A similar experiment was conducted using water.
FIG. 34 shows the relationship between the dimensionless droplet interval and Δxmax1 of the third droplet. In the case of water, the initial maximum value of the dimensionless moving distance in the positive direction is Δxmax1. As in the case of using fuel droplets as the third droplet, Δxmax1 decreases as the dimensionless droplet spacing increases. When fuel droplets are used, Δxmax1 shows a value of 0.62 near s = 5.0, and when water droplets are used, Δxmax1 shows a value of 0.4. Here, considering the case where the first and second droplets are dragged by the thermal expansion flow and are balanced with gravity, the displacement of the droplets is inversely proportional to the density of the droplets. The difference between the two values can be explained quantitatively by the difference in density of fuel and water. From the above, it is considered that the third droplet evaporation contributes little to the movement of the third droplet.

[Movement of droplet after spreading]
FIG. 35 shows the relationship between the dimensionless droplet interval and the dimensionless maximum movement distance Δxmax2 after combustion when the initial droplet diameter is 0.8 mm. Δxmax2 is the maximum value of the Δx maximum after the third droplet has spread. Δxmax2 represents the degree of drag exerted on the third droplet by the flow of fuel vapor and burned gas generated by the second and third droplets. After the third droplet spread and spread, there was no case where Δx did not reach the maximum value and the combustion ended. (See FIGS. 29 to 32) Δxmax2 was set to zero when the third droplet did not spread and spread. When the dimensionless droplet interval is from 1.2 to 3.3, Δxmax2 increases, takes a maximum value at s = 3.3, and decreases to s = 7.4. The reason why Δxmax2 takes the maximum value at s = 3.3 is unknown in detail because the movement in the positive direction before combustion, the spreading position, the restoring force of the pendulum, natural convection, etc. complicate the phenomenon. When the amount of movement in the x direction increases due to the pendulum mechanism, it is strongly influenced by upward natural convection. Therefore, since it is not known how the fuel vapor and burnt gas affect the movement of the third droplet, the experiment must be conducted in a microgravity environment without the influence of natural convection and the restoring force of the pendulum.

[Burning delay time]
The effect of the phenomenon in which the third droplet moves in the positive direction before the spreading spread on the burning spread induction time was investigated. FIG. 36 shows the relationship between the dimensionless droplet interval and the dimensionless flame spread induction time τ. The flame spread induction time when the third droplet was a fixed droplet was the flame spread induction time between the first and second droplets. Τ in the case of fixed-fixed droplets becomes infinite near the dimensionless droplet interval s = 6.2. Τ between fixed and moving droplets increases rapidly around s = 5.8. When the dimensionless droplet interval is in the range of 5.5 to 5.8, in the case of fixed-moving droplets, the third droplet moves away from the second droplet before spreading, so τ is smaller than that between fixed-moving droplets. It will be longer and the spread limit will be shorter.

[When droplet diameter is 0.3 mm]
Previous experiments have been performed using an initial droplet diameter of about 0.8 mm. When the initial droplet diameter is reduced, the effect of natural convection decreases and the spreading phenomenon in a microgravity field can be observed. Therefore, the initial droplet diameter was set to 0.3 mm and the experiment was conducted.

[Relationship between dimensionless droplet interval and mode]
FIG. 37 shows the relationship between the dimensionless droplet interval and the mode when the initial droplet diameter is 0.3 mm. The spread limit is about 6 for a droplet with an initial droplet diameter of 0.8 mm, whereas s is about 12 and doubled for an initial droplet diameter of 0.3 mm. I understand. When the droplet diameter is large, natural convection is strengthened and the flame of the droplet is extended upward. Conversely, when the droplet diameter is small, natural convection is weakened and the flame spreads in a spherical shape. Therefore, compared to the initial droplet diameter of 0.8 mm, the flame diameter in the flame spread direction with respect to the initial droplet diameter is larger, and it is considered that s indicating the flame spread limit has increased.

[Movement of fuel droplets before spreading]
Even when the initial droplet diameter was 0.3 mm, the forward movement of the third droplet before spreading was observed, so the data was organized in the same way as when d0 = 0.8 mm.
FIG. 38 shows the relationship between Δxmax1 and the dimensionless droplet spacing. Δxmax1 decreases from around s = 11. It was found that the behavior of the droplet before spreading when d0 = 0.3 mm is qualitatively the same as when d0 = 0.8 mm. The maximum value of Δxmax1 when d0 = 0.3 mm is about twice as large as that when d0 = 0.8 mm. It was found that the movement of the droplet becomes significant when the droplet diameter decreases.

[Drop behavior after spreading]
In the case of an initial droplet diameter of 0.3 mm, the movement after combustion was not observed because the combustion time of the third droplet was short.

[Burning delay time]
FIG. 39 shows the relationship between the dimensionless droplet spacing and the dimensionless flame spread induction time τ when the initial droplet diameter is 0.3 mm. Τ between fixed and fixed droplets was defined the same as in the case of an initial droplet diameter of 0.8 mm. Τ between fixed and fixed droplets becomes infinite near the dimensionless droplet interval s = 12.5. Τ between fixed and moving droplets increases rapidly around s = 11.5. When the dimensionless droplet interval is in the range of 10 to 11.5, the τ is longer than that between the fixed and fixed droplets because the third droplet moves away from the second droplet before spreading and spreading between the fixed and moving droplets. Therefore, it is considered that the flame spread limit becomes smaller. When the initial droplet diameter was 0.3 mm, τ showed the same dimensionless droplet spacing dependence as τ when the initial droplet diameter was 0.8 mm.

[[PTV measurement]]
In order to investigate in detail the cause of the third droplet moving in the positive direction before the spread of the flares occurred, the flow generated by the spread of the flares in the second droplet was measured by PTV.

[Tracer particle diameter, particle size distribution measurement results]
A particle size distribution analyzer (LDSA) was used to measure the tracer particle diameter. At the beginning of the experiment, tracer particles were sprayed using an air jet to supply tracer particles. FIG. 40 shows the particle size distribution of the tracer particle diameter when an air jet is used. It can be seen that the tracer particle diameter has extreme values of two peaks at about 8 and 60 μm, including primary particles and huge secondary particles in which many primary particles are aggregated. However, FIG. 41 shows the results when the tracer particles are scattered using ultrasonic vibration. Most of the tracer particle diameters were around 2.9 μm. When this result is converted into a number distribution, it becomes FIG. 42, and it can be seen that the number of tracer particles with a particle diameter of about 2.9 μm is the majority.

[Micrograph results]
FIG. 43 shows a micrograph of the tracer particles. The memory interval is 10 μm, and the dots that can be seen in the circle are the tracer particles. The tracer particle diameter was about 2.0 μm. The measurement result of the particle size distribution measuring device and the measurement result of the micrograph coincided. Therefore, it can be considered that a small tracer particle diameter could be supplied.

[Tracer particle motion]
The injection tracer method has been used so far by adding various landmark materials that move in the same manner as the fluid, so-called tracer particles, and visualizing the flow situation by the lines and patterns drawn. It is one of the most convenient and widely used methods among the visualization methods.
In order to accurately grasp the flow situation, it is necessary to select tracer particles having a high tracking ability with respect to the flow and mix it with the flow in a well-controlled manner.
When the flow is visualized by the injection tracer method, the followability of the tracer particles used to the flow is one of the important factors that influence the accuracy of the visualization. For this reason, it is necessary to consider in advance the tracer particle followability in consideration of the flow velocity, the shape of the flow field, the type of fluid, and the like. The main factors that influence follow-up include Brownian motion and follow-up in acceleration and vibration fields. In this section, we investigate the effects of Brownian motion, acceleration, and thermophoresis.

[Brownian motion of particles]
When particles of air collide with the particles from various directions and at various speeds, the particles move irregularly without regularity. This movement is called the Brownian movement. The thermal motion of air particles becomes active as the temperature rises, so the Brownian particles also become active. Therefore, the air particles collide vigorously, so the amount of Brownian particles driven increases, and the Brownian motion becomes more active as the temperature increases. The larger the brown particles, the larger the mass, so the amount of air particles that push the brown particles decreases. In addition, since the surface area of Brownian particles becomes large, when a large amount of air particles collide from various directions at once, the forces of each other cancel each other, and the force received by Brownian particles becomes small. This shows that Brownian motion is less likely to occur when the Brownian particles are large.

ここで， k はボルツマン定数，T は流体の絶対温度， ｔは時間である．本発明では，流体温度2000 K とし，

Where k is the Boltzmann constant, T is the absolute temperature of the fluid, and t is the time. In the present invention, the fluid temperature is 2000 K,

と，表すことができる。本発明において，直径ｄ＝2.9 μm の粒子が1 ms でブラウン運動する移動距離は，

It can be expressed as. In the present invention, the moving distance that a particle having a diameter d = 2.9 μm makes Brownian motion in 1 ms is

となる．1 ms に移動する距離は， 0.18 m μ となり無視できる値である．

It becomes. The distance traveled in 1 ms is 0.18 m μ, which is negligible.

[Movement of particles by temperature gradient (thermophoresis)]
Fine particles floating in a flow field with a temperature gradient move from a high temperature part to a low temperature part by thermophoresis. The moving speed v of the particles is given by

Where T is the absolute temperature of the fluid, dt / dy is the temperature gradient of the flow field, and λ _f and λ _p are the thermal conductivities of the fluid and particles. In this study, fluid temperature t = 300 k, thermal conductivity λ _f = 0.0259 W / m K, kinematic viscosity ν _f = 15.5 mm ² / s, thermal conductivity of SiO ₂ λ _P = 1.38 W / m K The temperature gradient dt / dy is 400 K / mm when calculated from the quasi-stationary theory as the adiabatic flame temperature 2270 K. The moving speed v in the air of 300 K is
v = 0.558mm / s (17)
From the above equation, the distance traveled in 1 ms is 0.558 μm, which is negligible.

[Acceleration of particles]
When injecting particles into a fluid from a nozzle, small hole, etc., or when the particles flow through a flow field of varying speed, it takes some time for the particles to reach the fluid velocity uf. Meanwhile, the force acting on the particle is the force that accelerates (or decelerates) the particle and the fluid resistance, and the fluid resistance follows Stokes' law. The particle acceleration du _p / dt can be expressed as follows.

粒子の初期速度をゼロとすると粒子の速度p u は

If the initial particle velocity is zero, the particle velocity pu is

となる．したがって，粒子が流体速度の99％に達するまでの時間ｔ_０は

It becomes. Therefore, the time t ₀ until the particles reach 99% of the fluid velocity is

となる．粒子の初期速度がゼロの場合について評価しており，粒子の初期速度が流体速度に近いほど加速時間と移動距離は小さくなる．平均粒直径2.9μm,密度2g/cm3 のSiO2 粒子，PTV 計測から得られた流速60 mm/s について,粒子が流速の99％に達するまでの時間0 t は0.26 ms である。撮影速度は1000 fps であるので，画像が更新されるまでにトレーサ粒子は流体の速度を十分に示していることがわかる。 これらトレーサ粒子の運動が計測に与える影響は小さいことがわかった。

It becomes. The case where the initial velocity of the particle is zero is evaluated, and the acceleration time and the moving distance become smaller as the initial velocity of the particle is closer to the fluid velocity. For SiO2 particles with an average particle diameter of 2.9μm, density of 2g / cm3, and a flow rate of 60 mm / s obtained from PTV measurement, the time 0 t until the particles reach 99% of the flow rate is 0.26 ms. Since the imaging speed is 1000 fps, it can be seen that the tracer particles sufficiently indicate the fluid velocity before the image is updated. It was found that the movement of these tracer particles had little effect on the measurement.

[Flow that spreads out]
FIG. 44 is a PTV image after the second liquid droplet spreads. The flow behavior was shown with time. The time when the second droplet spreads and spreads was set to zero. At t = -1 ms, the flow with the first droplet can be confirmed. t = 0 to 4 ms is the process in which the second droplet spreads and the flame surrounds the droplet. A vector is displayed radially around the second droplet, and the length of the vector decreases as the distance from the second droplet increases. The flow velocity near the flame is about 120 mm / s. At t = 5 to 10, there was no tracer particles near the flame, so the flow velocity at a position away from the flame was observed to be 60 mm / s. The thermal expansion flow generated by the spreading of the second droplet exists radially around the second droplet, and the flow velocity decreases with increasing distance from the second droplet. The effect of natural convection appears at t = 19 ms, and the effect of natural convection increases at t = 30 ms.

[Influence of initial speed]
The x-axis was set in the row direction, and the direction from the second droplet to the third droplet was positive. The tracer particles were moving vertically upward at an average initial velocity of 25 mm / s at an angle of 66 ° with the x-axis due to the constraints of the feeder. The average x-direction velocity was 10 mm / s. The speed measurement range is shown in FIG. The range enclosed by a dotted line is used, and the flow velocity data is the average value of the y component of the velocity vector measured at each time. Figure 46 shows the relationship between the velocity in the y direction and time. The origin of time was set to zero when the second droplet spread and spread. At t = -28 ms, a flow of 22 mm / s is generated by the tracer particle feeder. At t = -25 ms, the first droplet ignites, and the velocity in the y direction decreases due to the influence of the thermal expansion flow. At t = 0 ms, the second droplet spreads and the velocity in the y direction is 0 mm / s. In other words, there is no y-direction velocity at the time when the second droplet spreads and the flow produced by the tracer particle supply device is considered to have little effect on the phenomenon.

[Flow spatial and temporal changes]
FIG. 47 shows a measurement range when vectors obtained by PTV measurement are arranged in time series. The average value of the x component of the velocity vector measured in the range surrounded by the dotted line was used as data. The relationship between the flow velocity in the x-axis direction and the dimensionless distance is shown in FIG. 48 over time. The dimensionless distance x from the second droplet is the value obtained by dividing the x-axis direction distance from the second droplet center by the initial diameter of the second droplet. The origin of the time is the time when the second droplet spreads. The dimensionless interval between the first and second droplets was 5.5. From t = 0 to 30 ms, the flow velocity exceeds 30 mm / s. It can be seen that the heat generated by the first and second droplets and the expanded flow of the burned gas extend to around s = 12.0. This suggests that the effect of the thermal expansion flow of the first droplet reaches about s = 6.0 in FIG. When t = 50 ms, the effect of natural convection becomes stronger in the range of s> 6.0, and the flow velocity turns in the negative direction. From the above, it is considered that the third droplet moved in the positive direction under the influence of the thermal expansion flow before the third droplet spread and then moved in the negative direction due to the effect of natural convection.

[Thermal expansion flow]
FIG. 49 shows a detailed continuous image of flame spread at s = 5.7. The time when the second droplet spread and spread was set to zero. It can be seen that the second droplet burns and the flame develops at t = 0 ms. At t = 1 ms, a flame traveling around the second droplet can be observed. At t = 2 to 3 ms, a triple flame traveling along the leading edge of the flame is observed. At t = 4 to 6 ms, it was observed that the flame progressed to wrap around the second droplet, and collided and blown out. FIG. 50 shows the result obtained by PTV measurement of the flame. The flow velocity was superimposed on the images at the time when the flame collided to show the flow velocity. It can be seen that the flow velocity increases at the position where the flame of the second droplet collides. The flow rate was about 150 mm / s.

[[Physical phenomenon of flow]]
[Calculation of movement before spreading]
The phenomenon of moving away from the second droplet before the third droplet spreads is verified using simple calculations. As shown in FIG. 51, the balance between the drag force and gravity received by the pendulum placed in a uniform flow was calculated. The flow velocity obtained by PTV measurement was used as the uniform flow velocity. The numerical values used for the calculation are shown below. Droplet radius r is 0.4 × 10 ^-3 m, heptane density ρ is 679.5 kg / m ³ , viscosity coefficient of air (at atmospheric pressure, 20 ° C) μ is 1.822 × 10 ^-7 Pa s, obtained from PTV measurement The flow velocity V was 50 × 10 ⁻³ m, and the arm length l of the catenary line was 30 × 10 ⁻³ m.
Assuming the droplet is a sphere and calculating the mass

The dimensionless moving distance Δx = 0.29 above is the numerical value at the balanced position. When d ₀ = 0.8 mm, Δxmax1 is about 0.5. Since this value is the maximum value of the movement amplitude of the third droplet, the value of the balance position is estimated to be 0.25. From the above results, the calculation result of the pendulum placed in a uniform flow and the result of Δx of the normal gravitational field are in good agreement.

[Velocity calculation of thermal expansion flow]
From the PTV measurement, it was confirmed that the flame was transmitted to the premixed layer formed on the second droplet and pushed the surrounding fluid away at the early stage of the second droplet spreading. FIG. 52 shows the premixed flame propagation process of the second droplet that has spread due to the heat of the flame of the first droplet. The radius r was taken from the center of the second droplet and the time was shown. At the initial stage when the flame spreads in the second droplet, the flame radius is small, and the flame radius increases as the flame advances through the second droplet. This is considered to be because the burned gas is heated by the flame and expands and cannot expand in the direction of the droplet, and therefore expands in the direction outside the droplet. The increase in flame radius δ _F was considered to push out the air around the second droplet, and the flow velocity of the thermal expansion flow generated during propagation of the premixed gas layer flame was simply measured.
From the image of FIG. 49, V _{1 is} a value obtained by calculating the volume of the sphere from the flame radius at the moment when the flame spreads in the second droplet, and V ₁ is a value obtained by calculating the volume of the sphere from the radius of the flame when the flame spread is completed. ₂ Increased volume ΔV is

となる。PTV 計測の結果では，熱膨張流の瞬間流速は約120 mm/s であった。計算で得られた結果は平均流速85 mm/s であり実験結果より小さい。火炎外側の気体の膨張を考慮していないこと，および，次のパラグラフで計算する燃焼ガス流速より大きな値を示していることより，定性的に本モデルは熱膨張流発生メカニズムを表現していると考えられる。

It becomes. As a result of PTV measurement, the instantaneous flow velocity of the thermal expansion flow was about 120 mm / s. The calculated result is an average flow velocity of 85 mm / s, which is smaller than the experimental result. This model qualitatively expresses the mechanism of thermal expansion flow generation because it does not consider the expansion of the gas outside the flame and shows a value larger than the combustion gas flow velocity calculated in the next paragraph. it is conceivable that.

[Calculation of burnt gas flow velocity after second droplet spreading]
The quasi-stationary theory was used to examine whether the flow after the envelope flame was established in the second droplet was caused by the flow of burned gas. It is considered to be close to a quasi-stationary state. The flow velocity outside the flame is calculated 10 ms after the second droplet spreads and spreads (see FIG. 44). In this state, the flame is spherical and the influence of natural convection is small. FIG. 53 shows the calculation conditions. The temperature of the flame is the adiabatic flame temperature, and the shape of the flame and droplet is assumed to be a sphere. The flame position obtained by PTV measurement was used.
FIG. 54 shows the time variation of the square of the droplet diameter in the case of a single droplet. Since the start of combustion, the combustion rate constant kb was 2 0.76 mm / s. From this combustion rate constant, the evaporation amount is calculated using equation (3-12).

になる。ヘプタン−空気予混合気の断熱火炎温度と燃焼によって生じる生成物質の分圧を断熱火炎温度プログラムより計算した。その結果を表１２ に示す。液滴燃焼の場合，火炎が形成される位置での当量比は１と考えられることから，当量比1 においての断熱火炎温度と燃焼生成物の分圧率を算出した。断熱火炎温度TFlameは2270.072 K となり，燃焼生成物の分圧率は生成比率が大きい順にＮ₂ =0.715, H_２O=0.135, CO_２ =0.109 となる。この生成物質の分圧率からダルトンの法則より N_２, H_２O, CO_２ の密度を求めると

become. The adiabatic flame temperature of the heptane-air premixed gas and the partial pressure of the product produced by combustion were calculated from the adiabatic flame temperature program. The results are shown in Table 12. In the case of droplet combustion, the equivalent ratio at the position where the flame is formed is considered to be 1. Therefore, the adiabatic flame temperature and the partial pressure ratio of the combustion product at the equivalent ratio 1 were calculated. The adiabatic flame temperature TFlame is 2270.072 K, and the partial pressure ratios of the combustion products are N ₂ = 0.715, H ₂ O = 0.135, and CO ₂ = 0.109 in descending order of generation ratio. The density of N ₂ , H ₂ O, CO ₂ is obtained from Dalton's law from the partial pressure ratio of this product.

となる。第二液滴に燃え広がりが生じてから10 ms 後の火炎面外縁の流速は，約38 mm/sであることがわかる。図４８での第二液滴に燃え広がりが生じてから10 ms 後の火炎半径の無次元位置x = 2.2（実際の火炎半径は1.7 mm である）付近の流速は32 mm/s であり定量的に一致した。このことから，第二液滴に燃え広がりが生じてから10 ms 後の火炎面外側においては，既燃ガスが流れを生じていると考えられる．これらの計算により，モデルを簡略化したにもかかわらず，計算結果とPTV 計測の結果が定性的に一致した。
以上の考察から，燃え広がりによって生じる流れには二つの流れがあることが本発明によりわかった。
１， 火炎が第二液滴の予混合気層を伝播する際に発生する熱膨張流がつくる流れ。
２， 火炎伝播が完了した後，燃焼によって生じた既燃ガスがつくる流れ。
また，予混合火炎伝播により生じる熱膨張流の流速は既燃ガスによって生じる流れの流速よりも大きいことがわかった．

It becomes. It can be seen that the flow velocity at the outer edge of the flame 10 ms after the spread of the second droplet is about 38 mm / s. The flow velocity around the dimensionless position x = 2.2 of the flame radius 10 ms after the spread of the second drop in Fig. 48 (actual flame radius is 1.7 mm) is 32 mm / s, which is quantitative. Matched. From this, it is considered that burned gas is flowing outside the flame surface 10 ms after the second droplet spreads. Although these calculations simplified the model, the calculation results and PTV measurement results qualitatively matched.
From the above consideration, it has been found by the present invention that there are two flows caused by the spread of the flame.
1, Flow created by a thermal expansion flow generated when a flame propagates through the premixed gas layer of the second droplet.
2, Flow created by burned gas generated by combustion after flame propagation is completed.
It was also found that the flow velocity of the thermal expansion flow generated by the premixed flame propagation is larger than the flow velocity generated by the burned gas.

[[Microgravity field]]
[Behavior of third droplet]
In order to eliminate the effects of natural convection and the restoring force of the pendulum, experiments were conducted in a microgravity environment. The continuous photographs in FIG. 55 show the flame spread behavior in a microgravity environment when s = 4.5. To capture the movement of the third droplet in detail, the second and third droplets were magnified. The white line in the figure is the initial position of the third droplet. The start time of the microgravity environment was t = 0 s. The x-axis and y-axis were set as shown in FIG. The first droplet was ignited at t = 0.2 s. The photo at t = 0.2 s is the moment when the first droplet ignites, and at this point, three droplets are aligned. At t = 0.3 s, the third droplet has already spread and the third droplet starts moving in the positive direction, as in the case of the normal gravitational field. At t = 6.0 s, the flame grows out of the field of view, so no flame is visible in the image, but combustion continues.
The graph on the right side of Fig. 54 shows the time variation of the dimensionless travel distances Δx and Δy in the x and y directions. It can be seen that the velocity in the x direction is zero at t = 0 s. Due to the structure of the third catenary line, there is a movement in the y direction when moving to a microgravity environment, but the subsequent movement is small. At t = 0.20 s, the first droplet ignited, and at t = 0.23 s, the spreading of the second droplet was completed. Since the velocity of the third droplet increases around this time, the third droplet exerts a force in the direction away from the second droplet due to the thermal expansion flow generated by the spreading of the first and second droplets. It is thought that I received it. At t = 0.26 s, the third droplet spreads and spreads. After t = 0.3 s, the motion is almost constant, and after t = 0.6 s, the velocity is attenuated.

As is apparent from the detailed description above, in the present invention, focusing on the interference between the flame and the droplet in spray combustion, the three fuel droplet rows (first fixed suspension) using the pendulum suspension line movable in the row direction are used. Using a simple one-dimensional model (droplet-second fixed suspended droplet-movable suspended droplet in the third row direction), it was possible to measure the spread of fuel droplet rows. As a result of flame spread experiments and PTV measurements conducted in normal and microgravity fields, the following findings were obtained.
1. Before the third droplet burns and spreads, the third droplet receives the thermal expansion flow of the second droplet and moves away from the second droplet. This dimensionless maximum travel distance decreases as the dimensionless droplet spacing increases. A similar trend was observed when the initial droplet diameter was small. The dimensionless maximum travel distance when the initial droplet diameter was small was about twice as large as the dimensionless maximum travel distance when the initial droplet diameter was large. In other words, the dimensionless maximum travel distance increases as the initial droplet diameter decreases.
2. In order to consider the movement of the third droplet before the third droplet burns and spreads, an experiment was conducted using water droplets as the third droplet. As a result, the third droplet showed the same behavior as the fuel. In other words, the dimensionless maximum travel distance decreased as the dimensionless droplet spacing increased. The effect of evaporation of the third droplet on the movement was found to be small.
3. After the flame spreads over the third droplet, the third droplet moves away from the second droplet. The third droplet is thought to move by the fuel vapor flow and the burnt gas flow that generate the second and third droplets. The dimensionless maximum travel distance after spreading of the third droplet reached its maximum near the dimensionless droplet spacing3.
4. Comparing the flame spread induction time between the fixed and fixed droplets and the flame spread induction time between the fixed and moving droplets, the third droplet moves away from the second droplet between the fixed and moving droplets. In the vicinity of the limit distance, the flame spread induction time increases compared to the case between fixed and fixed droplets, and the flame spread limit decreases. There was no difference in the induction time for non-dimensional droplets other than the vicinity of the spread limit. When the droplet diameter is small, the dimensionless droplet spacing dependence of the flame spread induction time is qualitatively the same as when the droplet diameter is large.
5. From the PTV measurement, it was found that the flow in which the second droplet was generated spread radially from the second droplet, and the flow velocity decreased with increasing distance from the second droplet.
6. A triple flame traveling around the second droplet was observed, and it was confirmed that the thermal expansion flow was blown out when the flame collided. From the PTV measurement, the blowout flow rate was about 120 mm / s.
7. It was found that there are two flows caused by the spreading of the flame. 1) The flow created by the thermal expansion generated when the flame propagates through the premixed gas layer of the second droplet. The instantaneous flow velocity reached about 120mm / s. 2) The flow created by burned gas generated by combustion after flame propagation is completed. The flow velocity near the flame reached about 40 mm / s. It was also found that the flow velocity of the thermal expansion flow generated by the premixed flame propagation is larger than the flow velocity generated by the burned gas.
8. It was observed in the microgravity environment that the third droplet moved at almost constant speed in the direction away from the second droplet even after the spread of the flame.

It is the schematic of the whole prototype measuring apparatus in this invention. It is a layout of suspended droplets. It is the figure which showed the 3rd Y character catenary line. It is the schematic of the droplet production | generation apparatus in the measuring device in this invention. It is an adjustment apparatus of a brass tubule in the present invention. It is the figure which showed the ignition path | route. It is the figure which showed the outline and internal circuit of the switch box in this invention. It is the figure which showed the one part program actually used by the measurement of this invention. It is the figure which showed the typical apparatus example for the PTV image recording in the wind tunnel experiment in this invention. 1 is an overall schematic diagram of an example of a measuring apparatus according to the present invention. It is the figure which showed the visualization range in a measuring device. It is the figure which showed the synchronous box of the PTV experimental apparatus, and the wiring of each apparatus. It is the figure which showed the time chart of PTV measurement. It is the figure which showed the general view of the copper vapor laser. It is the figure which showed the schematic of the tracer particle generator. It is the figure which showed the schematic of the gravity classification apparatus. It is the figure which showed the schematic of the whole microgravity measuring apparatus. It is a figure of the fall tower for implement | achieving a microgravity environment. It is the figure which showed the fall capsule. It is the schematic of a capsule separating device. It is a figure showing switch arrangement of a control panel. It is the figure which showed the structure of the separation apparatus after a change. FIG. It is the figure which showed the model of the quasi-stationary theory of combustion. It is the figure which showed concentration distribution of fuel and air. It is the figure which showed temperature distribution. It is the figure which showed the flame spread form. FIG. 6 is a diagram showing a relationship between a dimensionless droplet interval s and a mode when an initial droplet diameter is 0.8 mm. It is the figure which showed the flame spread behavior image and the behavior of the 3rd droplet by time change. It is another figure which showed the image of the flame spread behavior, and the behavior of the 3rd droplet by time change. It is another figure which showed the image of the flame spread behavior, and the behavior of the 3rd droplet by time change. It is another figure which showed the image of the flame spread behavior, and the behavior of the 3rd droplet by time change. It is the figure which showed the relationship between the dimensionless droplet space | interval and the positive direction dimensionless maximum moving distance (DELTA) xmax1 before spreading. It is the figure which showed the relationship between dimensionless droplet space | interval and (DELTA) xmax1 of the 3rd droplet. FIG. 6 is a diagram showing a relationship between a dimensionless droplet interval and a dimensionless maximum moving distance Δxmax2 after combustion when the initial droplet diameter is 0.8 mm. It is the figure which showed the relationship between a dimensionless droplet space | interval and dimensionless flame spread induction time (tau). FIG. 5 is a diagram showing a relationship between a dimensionless droplet interval and a mode when an initial droplet diameter is 0.3 mm. FIG. 6 is a diagram showing a relationship between Δxmax1 and a dimensionless droplet interval. It is the figure which showed the relationship between dimensionless droplet space | interval and dimensionless flame spread induction time (tau) in the case of the initial droplet diameter of 0.3 mm. It is the figure which showed the particle size distribution of the tracer particle diameter at the time of using an air jet. It is the figure which showed the result at the time of scattering tracer particle | grains using the vibration of an ultrasonic wave. It is the figure which showed the tracer particle number distribution. It is a microscope picture figure of a tracer particle diameter. It is the figure which showed the PTV image of the 2nd droplet. It is the figure which showed the calculation range of the average y-axis direction speed. It is the figure which showed the time change of the y-axis direction average speed. It is the figure which showed the calculation range of the average x-axis direction speed. It is the figure which showed the time change of the x-axis direction average speed. It is the figure which showed the mode of the flame burning spread of the 2nd droplet. It is a figure showing the thermal expansion flow ejection from a triple flame and a 2nd droplet. It is the figure which showed the pendulum model of the droplet which receives a uniform flow. It is a calculation model of ambient flow velocity in premixed flame propagation. It is the figure which showed the calculation model of the burnt gas flow velocity in the flame vicinity in a quasi-stationary theory. It is the figure which showed the combustion rate constant of the single droplet. It is the figure which showed the behavior of the 3rd droplet in microgravity.

Claims (15)

(A) In the housing or in the partition space, (b) A suspended line support base for supporting a suspended line in which a plurality of simulated suspended droplet nuclei are attached in a row, and (c) the plurality of simulated suspended droplet nuclei. A liquid droplet generator for supplying simulated liquid droplets by supplying liquid fuel to the simulated suspended droplet nuclei and forming a film of the liquid fuel on the simulated suspended droplet nuclei; and (d) at least the plurality of simulated suspended droplet nuclei A tracer particle supply device for supplying a tracer particle cloud to a region on which a film of liquid fuel is formed; and (e) an ignition device, and in or out of the housing or partition space (f A combustion propagation analysis and flame spread measurement device having an optical measurement system and (g) a sequencer for controlling them, wherein (d) the tracer particles are supplied pneumatically from a tracer particle source by the tracer particle supply device. Supply path On the way, coarse particles in the tracer particles are removed, and only particles having a uniform particle size are supplied to a region where a film of liquid fuel is formed on the plurality of simulated suspended droplet nuclei (d1). A combustion propagation analysis and flame spread measurement apparatus characterized by comprising a tracer particle sorting means. The measuring apparatus according to claim 1, wherein (a) the material forming the housing or the partition space is a light transmissive material. The (b) suspension line support base supports the suspension line to which the first fixed suspended droplet, the second fixed suspended droplet, and the third moving suspended droplet are attached in order from the side closer to the ignition device. The measuring apparatus according to claim 1. (B) The catenary line supported by the catenary line support base partially supports a part of the plurality of simulated suspended droplet nuclei so as not to perform pendulum movement on the catenary line support base, and the other simulations 4. The measurement according to claim 3, wherein the thickness of the silicon carbide that supports the suspended droplet nuclei so as to allow pendulum movement is a thin line having a thickness of 20 μm or less, and the interval between the simulated suspended droplet nuclei is adjustable. apparatus. The measuring apparatus according to claim 3, wherein the plurality of simulated suspended droplet nuclei are ceramic spheres having a diameter of 30 to 800 μm and can be replaced with the suspended line or the suspended line support base. (C) The droplet generating device is composed of an air slide stage, a liquid fuel container, a fuel feeding device, a fuel supply pipe, a brass thin tube, and a regulating device, and the air slide stage is turned on and off by a sequencer. The measuring apparatus according to claim 1, wherein the forward / reverse movement is controlled. 7. The fuel feeding device includes a microsyringe that injects fuel guided from the fuel supply pipe to the brass thin tube and a ball that is connected to the microsyringe and feeds the fuel to a simulated suspended droplet through a ball screw. The measuring device described in 1. The measuring device according to claim 1, wherein the simulated droplet generated in the (c) droplet generating device has a diameter of 150 to 1600 μm. The tracer particle supply apparatus (d) has a particle tank for storing silica particles having a volume average particle diameter of 0.05 to 12.0 μm, a particle supply pipe, and a particle cloud discharge pipe. The pipe has an air supply pipe for supplying air to the particle supply pipe via an air tank, a regulator, a solenoid valve, and a flow rate controller to form a particle cloud, and the tip of the particle cloud discharge pipe The measuring device according to claim 1, wherein the measuring device is located immediately below a brass thin tube for supplying the fuel. The measuring apparatus according to claim 1, further comprising a particle size distribution measuring apparatus in the vicinity of the (d1) tracer particle sorting unit. The (e) ignition device has an ignition power circuit including a step-up transformer for stepping up a voltage from a DC power source, and noise from the ignition device when a trigger output to the ignition device is directly connected to the ignition device. The measuring apparatus according to claim 1, wherein the measuring apparatus is an electric spark ignition device controlled by a sequencer via a sequencer and a relay for avoiding other obstacles. 2. The measuring apparatus according to claim 1, wherein (f) the optical measurement system includes a laser film irradiation means and a high-speed video camera or a CCD digital camera having a CCD array. The (g) sequencer is composed of a CPU unit, an extension output unit, and a power supply unit, constitutes a control device together with a switch box, and controls a stepping motor, a solenoid valve, an ignition device, and the optical measurement system. The measuring apparatus according to claim 1. A capsule covering the entire apparatus, a capsule lifting means for lifting the capsule to a drop tower, a capsule separating means for separating the capsule from the capsule lifting means and allowing the capsule to fall freely, and the dropped capsule The measuring apparatus according to claim 1, further comprising a microgravity imparting unit having a buffer unit that cushions an impact force when received. The measurement device according to any one of claims 1 to 14, wherein the information on the airflow image transmitted by the optical measurement system (f) is branched for monitoring and recording by a connector, and the monitor image is visually confirmed. While recording and recording, the recorded airflow image is binarized as necessary, and the binarized image data is stored in a memory as required to be emphasized, averaged and / or selected. A flame propagation mode test method based on PTV measurement between fuel droplet particles, wherein the image information processing is executed and the binarized image data is graphed.

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