JPH04355357A - Constant volume combustion apparatus for combustion characteristic evaluation for liquid fuel oil - Google Patents

Abstract

PURPOSE:To obtain a combustion apparatus which enables observation of a flame propagation state of a liquid fuel oil and easy and accurate measurement of a combustion speed in a laboratory manner. CONSTITUTION:A combustion apparatus is provided with a burning apparatus body which has a combustion chamber 11 closed inside while having a window 12 for observation, a heater 3 mounted on the external surface of the burning apparatus body, a temperature detector 4 for detecting the temperature of the combustion chamber 11, a liquid fuel oil feeder 5 to supply a specified amount of a liquid fuel oil to the combustion chamber 11, an air feeder for supplying air to the combustion chamber 11, a stirrer 7 having a stirring member 22 movable in the combustion chamber 11 and an ignition plug 8 which can form a spark in the combustion chamber 11. When performing a measurement, first, the combustion chamber 11 is purged inside and then, the liquid fuel oil as sample is supplied thereto. The stirring member 22 is operated manually to form a premixed gas with the air. Thereafter, the mixed gas is ignited. The state of flame propagation is observed through the window 12 for observation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant volume combustor for observing the state of flame propagation of liquid fuel oil and measuring the combustion rate in a laboratory in order to evaluate the combustibility of liquid fuel oil.

0002

2. Description of the Related Art In order to improve the output of a spark ignition engine, it is important to make the thermal cycle as close as possible to the Otto cycle, which is based on constant volume combustion with ignition at compression top dead center, in order to increase thermal efficiency.

[0003] At present, actual combustion requires a period of about 40 to 60 degrees of crank angle, and efforts are being made to shorten this combustion period while preventing knocking and NOx generation, that is, increasing the combustion speed. This is desperately needed as a measure to improve output or thermal efficiency. Therefore, if the relationship between combustion speed and fuel oil properties can be understood, it is possible to design fuel oil with the aim of improving output. To do this, it is necessary to measure the combustion rate of a mixture of evaporated liquid fuel oil and premixed air with air under conditions similar to those during engine operation.

0004

[Problems to be Solved by the Invention] However, although the method of measuring combustion speed, combustion pressure, and flame propagation velocity using an actual engine is a method that conforms to the usage conditions of fuel oil, there are many related factors. If there are too many, there are problems such as the inability to clearly understand the relationship between specific fuel oil properties and specific combustion speed, etc.

On the other hand, basic combustion rate measurement methods include the burner method and the circular tube method. However, these methods mainly measure measurements using gaseous fuel, and when these methods are applied to liquid fuel oil, the properties of liquid fuel and gaseous fuel are significantly different, so the conventional burner method and circular method described above are difficult to apply. With the pipe method, etc., it is difficult to form a premixture of liquid fuel, so there are problems such as difficulty in reproducing the combustion state inside the engine. Regarding the method of forming a premixture, a method has been proposed in which a premixture is formed in an external tank separated from the combustion chamber and fuel is supplied to the combustion chamber, but in this case, if mixed fuel is used, During the transfer process, the composition changes due to differences in the diffusion rate of the mixed components, causing problems such as the inability to make accurate measurements. For this reason, it is desired to develop a constant volume combustion apparatus that can observe the flame propagation state of liquid fuel oil and measure the combustion rate in a laboratory.

The present invention was made in view of the above circumstances, and aims to develop a combustor that can easily and reliably measure the flame propagation state of liquid fuel oil and the combustion rate in a laboratory. More specifically, the object is to provide a laboratory technique for evaluating the combustion characteristics of single or mixed liquid fuel oils, particularly gasoline base materials and additives.

[0007]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the inventors have found that after supplying a predetermined amount of air into a container in advance, and then injecting liquid fuel oil, By stirring, a homogeneous mixture can be formed directly.
Furthermore, by using a constant volume combustor that can measure the resulting flame propagation through an observation window by igniting and burning this air-fuel mixture, using a laser beam refraction method, etc., liquid fuel oil can be measured. The present inventors have discovered that the flammability of flammability can be evaluated in a laboratory, and have completed the present invention.

That is, the gist of the present invention is to provide a combustor main body that forms a sealed combustion chamber inside and has an observation window, a heater attached to the outer surface of the combustor main body, and a combustor main body that has an observation window. a temperature detector that detects the temperature of the combustion chamber; a liquid fuel oil supply device that supplies a predetermined amount of liquid fuel oil to the combustion chamber; an air supply device that supplies air to the combustion chamber; The combustion chamber is characterized in that it comprises a stirrer having a stirring member, and a spark plug capable of forming a spark within the combustion chamber.

[0009]

[Operation] While keeping the temperature of the combustion chamber at the set value, the combustion chamber is purged, a predetermined amount of air is supplied, and then the liquid fuel oil to be measured is transferred from the liquid fuel oil supply device onto the stirring member. Drip. Next, the stirring member is moved up and down to form a premixture of liquid fuel oil and air in the combustion chamber. Next, after igniting the premixed mixture with a spark, the flame propagation is observed through an observation window using an optical measuring instrument. Further, according to the device of the present invention, since a premixture can be directly formed in the combustion chamber, it can be applied not only to a single liquid fuel but also to a mixed liquid fuel.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below with reference to the drawings showing one embodiment. In FIG. 1, 1 is a combustion device. The combustion device 1 includes a combustor main body 2, a heater 3, a temperature detector 4, a liquid fuel oil supply device 5, a gas supply/discharge device 6, an agitator 7, and a spark plug 8. The main material of the combustor body 2 is stainless steel (SUS304), and a sealed combustion chamber 11 is formed inside. There is no particular restriction on the size and shape of the combustion chamber 11, but considering the formation of a homogeneous mixture, it is approximately 30 to 80 mm x approximately 30 to 80 mm x approximately 150 mm.
It is a rectangular parallelepiped of ~400 mm or a cylinder of equivalent capacity. The volume of the combustion chamber 11 is 300 cc or more. Combustion chamber 1
When 1 is a cylinder or a rectangular parallelepiped, an observation window 12 is formed on two wall surfaces penetrating the combustion chamber 11 in a straight line so that the flame propagation situation inside the combustion chamber can be observed.
is sealed airtight with Pyrex glass. Laser light, etc. from an optical measuring device is irradiated into the combustion chamber 11 through the observation window 12, and reflection, transmission, attenuation, refraction, etc. of the laser light is used to detect flames, etc. in the combustion chamber. The situation can be observed. Heaters 3 for temperature control are attached to all the outer surfaces of the combustor main body 2 other than the observation window 12, and the heaters 3 are further covered with a heat insulating material. As the heater 3, a sheathed heater can be used.

A temperature detector 4 is attached to the combustor body 2 to detect the temperature of the wall of the combustor body 2 or the temperature of the combustion chamber 11. For example, the temperature sensor 4 has an outer diameter of 1.6 m.
A K-type thermocouple (sheath type) of 1.5 m is inserted and attached to the side surface 78 mm from the top surface of the combustion chamber 11 until its tip is flush with the inner wall surface. However, if the heater is installed to cover the entire combustor body 2, the temperature within the wall surface of the combustion chamber 11 can be made almost uniform, so the installation position of the temperature sensor 4 is particularly limited. It's not a thing.

An ignition plug 8 is provided at the top of the combustion chamber 11. The ignition plug 8 is one for automobiles (for example, one made by NGK,
ZFR5A-11) etc. can be used. However, in order to improve ignitability, the electrode diameter of the spark plug can be set to 0.5 mm, and the gap can be set to 1.2 mm. Spark plug 8
is driven by a circuit (not shown) configured to cause sparks to fly between the electrodes.

A liquid fuel supply device 5 is disposed at the top of the combustor body 2. The liquid fuel supplier 5 supplies a predetermined amount of liquid fuel oil to the combustion chamber 11, and for example, a microsyringe can be used as the liquid fuel supplier 5. The combustion chamber 11 is connected to the gas supply/exhaust device 6. The gas supply/discharge device 6 includes an air intake pipe 13 , an air supply pipe 14 , an air supply pipe 15 , a gas suction pipe 16 , a gas discharge pipe 17 , a compressed air source 18 connected to the air supply pipe 14 , and a gas suction pipe 16 . The vacuum pump 21 is connected to the vacuum pump 21. Air intake pipe 1
3 is provided with a valve A, the air supply pipe 14 is provided with a valve B, the gas discharge pipe 17 is provided with a valve C, and the gas suction pipe 16 is provided with a valve D, respectively. Air supply pipe 15, gas suction pipe 16
And the gas exhaust pipe 17 communicates with the combustion chamber 11 .

The stirrer 7 has a stirring member 22 and a drive shaft 23. The stirring member 22 is disposed within the combustion chamber 11,
It has a plate shape with holes, is located perpendicular to the central axis direction of the combustion chamber 11, and is movable within the combustion chamber 11. ,
The stirring member 22 is attached to a drive shaft 23. The drive shaft 23 passes through the combustion chamber 11 in the central axis direction, and also passes through the upper and lower walls 24 and 25 of the combustion chamber 11 so as to be able to slide in an airtight manner. Handles 2 are attached to the upper and lower ends of the drive shaft 23.
7 and 28 are provided, and when the drive shaft 23 is moved up and down by grasping these handles 27 and 28, the stirring member 22 moves up and down in the combustion chamber 11 along with this up and down movement, and the stirring member 22 moves up and down in the combustion chamber 11.
Stir the gas inside.

A pressure detector 31 is attached to the combustor body 2 to measure the combustion pressure within the combustion chamber 11. The pressure detector 31 is a piezoelectric transducer that detects the pressure difference as a voltage difference, and as shown in FIG. Enter 10.

When measuring a combustion exhibiting a flame propagation velocity on the order of several meters per second with an oscilloscope using a laser beam refraction optical measuring device and a pressure transducer, the capture velocity is becomes important. Examples of oscilloscopes include high-speed digital storage oscilloscopes.
can be used. Analysis and storage of data detected by the temperature detector 4 and pressure detector 31 is performed on a personal computer using dedicated software.

An optical measurement device 32 is used to obtain data for measuring the combustion rate within the combustion chamber 11. As the optical measuring device 32, for example, a laser beam refraction measuring device 33 can be used. As shown in FIG. 3, the laser beam refraction measurement device 33
Gas laser oscillator 34, variable transmittance filter 35, prism 36, half mirror 37, front reflector 38, half mirror 41, front reflector 42, front reflector 43, 44,
45, condenser lenses 46, 47, and 48, and light receiving elements 52, 53, and 54 incorporated in a light receiving element assembly 51. A laser beam 55 emitted from a He-Ne gas laser oscillator 34 has its intensity adjusted by a variable transmittance filter 35, then its optical path is changed by a prism 36, and is divided into two by a half mirror 37 to form a beam. - beam 56 and beam 57. One beam 56 is further divided into two by a half mirror 41 to become beams 58 and 59, making a total of three beams 57.
, 58, 59 are generated. These three beams 57, 5
8 and 59 are changed in optical path by surface reflections 43, 44, and 45, enter the combustion chamber 11 through the window 12, and are refracted by the flame in the combustion chamber 11, and then pass through the condenser lenses 46, 47, and 48 to the light receiving element assembly 51. The light receiving element 52 incorporated in
, 53, 54. Each of the three beams 57
, 58, 59, the state inside the combustion chamber 11 can be known.

In the combustion apparatus 1 configured as described above, the operation for evaluating the combustibility of liquid fuel oil is as follows. First, the combustion chamber 11 is purged and a premixture is formed. [Purge 1] Activate the heater 3 to clean the combustion chamber 11
The temperature is the initial setting temperature (taking into account the boiling point range of gasoline,
Room temperature to 200°C under atmospheric pressure, preferably about 50°C to 17
After the temperature reaches 0°C), the gas in the combustion chamber 11 is exhausted from the valve D on the bottom (see Figure 1) using the vacuum pump 21, and the air is sucked through the valve A installed on the upper side for purging. Continue for a sufficient period of time, for example from several minutes to several tens of minutes. [Purge 2] After purge 1, close valves A and D, open valve C, and apply a smaller amount of compressed air than valve B for several minutes to several tens of minutes, preferably for about 3 to about 8 minutes. Flow. after that,
Close valves B and C to complete the purge.

[Formation of premixture] Carbon, hydrogen, oxygen, nitrogen, and sulfur in 1 kg of liquid fuel are converted to c, h, and o, respectively.
, n. s (kg), the theoretical oxygen amount O0 required for combustion of 1 kg of fuel can be found using the following equation 1.

[0020]

[Math. 1] O0 = 1.867c + 5.6 (ho/8)
+1.6n+0.7s (Nm3/K
g) …(1)

[0021] If a substance containing sulfur is not used, the term 0.7S is deleted from the calculation formula. In this case, the theoretical air amount A0 is the theoretical oxygen amount O0 divided by the oxygen concentration in the air, so let's say it is 21%.
Then, it can be found from the following equation 2.

[0022]

[Math. 2] A0 = O0 /0.21 = 8.89c + 26.67 (ho/8)
+7.62n (Nm3/K
g) …(2)

[0023] Fuel amount F0
varies depending on the size, temperature, fuel oil composition, and equivalence ratio of the combustion chamber. Calculated based on the initial pressure and initial temperature, the amount of air in the combustion chamber is Ar (ml), the equivalence ratio is φ, and the density is ρ
(g/cm3), it can be found from the following equation 3.

[0024]

[Formula 3] F0 = Ar /A0 ×φ/ρ (μl)
...(3) However, in the experiments described later, about 20 to about 140 μl (0.02 cc to 0.14 cc
)It was used.

[0025] The amount of fuel calculated using Equation 3 is measured using a microsyringe (any device other than a microsyringe may be used as long as it can accurately measure a small amount and can be supplied externally) and dripped into the stirring member 22. do. After visually confirming the evaporation state of the fuel through the observation window 12, the stirring member 22 is moved up and down 50 times or more, preferably 100 times or more, to stir and form a premixed mixture.

[Stabilization of gas flow] The mixture is left to stand for about several minutes to about 10-odd minutes, preferably about 3 to 10 minutes, until the influence of turbulence due to stirring disappears and the mixture becomes uniform. If it is too short, the mixture may become uneven; if it is too long, heavy fuel may settle and become uneven.

Next, the flame front passage time is measured. When the air-fuel mixture is ignited by the ignition device, the oscilloscope 10 starts measurement in response to a trigger from the ignition signal. When a flame with a large density gradient crosses a laser beam, the beam is deflected by refraction, and the amount of light received by a light receiving element, such as a phototransistor, changes, thereby recording a voltage drop on the oscilloscope. Further, the data is automatically transferred to the personal computer 20 via a GPIB interface or the like.

Next, the combustion pressure is measured if necessary. Combustion pressure is measured by a pressure detector 31, for example, a piezoelectric transducer that detects a pressure difference as a voltage difference, at the same time as the flame front passage time is measured.

[Experimental example] (Experimental conditions) Initial pressure In an actual engine, approximately 8
．． 0 to 15 Kg·G/cm 2 , but the initial pressure was set to atmospheric pressure in order to give priority to ease of experimentation and safety. Equivalence ratio φ = 1.2 Air Standard Air Note 1 Equivalence ratio = Actual fuel-air ratio / Theoretical fuel-air ratio (stoichiometric ratio) Equivalence ratio > 1... Fuel rich equivalence ratio < 1... Fuel lean

Initial Temperature Considering the same reason as the selection of the initial pressure and the boiling point of gasoline and the chemical reaction temperature, the initial temperature was set at about 90 to 120°C, preferably about 100 to 115°C.

Temperature measurement position 26mm from the top of the combustion chamber,
Measurements were taken at positions of 78 mm, 130 mm, and 182 mm.

Measurement position of flame front passage time The laser was installed so as to intersect at right angles to the central axis of the container. Three laser passing positions were selected and set depending on the purpose of the experiment. The location was selected based on the following criteria. [Main laser passing position for fuel flame propagation velocity measurement] ■ 4 mm (a) from the center of the spark plug electrode gap (the shortest distance that is not affected by spark plug discharge, about 3 to 7 mm) ■ The center of the spark plug electrode gap from
99mm (b) (1/2 of the combustion chamber length) ■133mm (c) from the center of the spark plug electrode gap (2/3 of the combustion chamber length)

(Results and Discussion) Flame Propagation Velocity Distribution and Combustion Pressure in the Container In this experiment, the required movement of the flame front was determined from the flame front passage time measured at the measurement position shown in the measurement position of the flame front passage time. The time t (msec) was calculated, and the average flame propagation speed in that section was called the flame propagation speed SL, which was calculated using the following equation 4.

[0034]

[Formula 4] SL = L/t (m/sec)...
(4)

[0035] Here, L is the distance the flame moves (mm)
, t is the time required for movement (msec). The number of experiments was 3 to 7 under the same conditions in consideration of variations, and the average value was taken as the required time.

[0036] Figure 4 shows the behavior of the flame in the container for three types of substances, and plots the time when the flame front passes the measurement position, with the time when the flame front passes the measurement position 4 mm from the center of the electrode gap of the ignition plug as a reference. This is what I did. It can be seen that the flame propagation speed accelerates from ignition to 1/3 of the container, then advances at almost constant speed until the center of the container, and then decelerates after passing the center. Moreover, this tendency is the same for all substances,
Between 4 and 133 mm, the order of flame front arrival among fuels did not change depending on the measurement position. A pressure diagram under the same conditions is shown in FIG. The pressure rise shows the same tendency as the flame propagation behavior, rising when the flame surface reaches 1/3 of the container, becoming almost constant around the center of the container, and then...
After the rate of increase decreases and becomes constant again for a period of time,
It rises rapidly and reaches the maximum pressure. This rate of increase was greater as the flame propagation speed was faster, and a higher maximum pressure was reached in a shorter time.

Table 1 lists the test fuels and their flame propagation speeds (
m/sec) and maximum pressure (bar).

[Table 1]

[0038]

According to the present invention, it is possible to observe the flame propagation state and burn rate of liquid fuel oil, especially mixed liquid fuel oil, in a laboratory, which has been difficult to measure in the past. Therefore, according to this constant volume combustion device, it is possible to easily evaluate gasoline base materials and additives, and gasoline design becomes possible. The stirring device can easily form a good premixture in the combustion chamber by external operation, and can create good measurement conditions.

[Brief explanation of drawings]

FIG. 1 is an explanatory longitudinal cross-sectional view of a combustor main body.

FIG. 2 is a configuration explanatory diagram showing the configuration of a measurement system in a constant volume combustion apparatus.

FIG. 3 is a configuration explanatory diagram showing an optical measurement device.

FIG. 4 is a graph showing flame propagation behavior within the combustion chamber.

FIG. 5 is a graph showing the pressure course in the combustion chamber.

[Explanation of symbols]

1 Combustion device 2　Combustor body 3 Heater 4 Temperature detector 5 Liquid fuel oil supply device 6 Gas supply/discharge device 7 Stirrer 8. Spark plug 11 Combustion chamber 12 Observation window 13 Air intake pipe 14 Air supply pipe 15 Air supply pipe 16 Gas suction pipe 17 Gas exhaust pipe 18 Compressed air source 20 PC 21 Vacuum pump 22 Stirring member 23 Drive shaft 24 Upper wall 25 Lower wall 26 Side wall 27 Upper handle 28 Lower handle 31 Pressure detector 32 Optical measurement device 33 Laser beam refraction measurement device 34 He-Ne gas laser oscillator 35 Transmittance variable filter 36 Prism 37 Half mirror 38 Surface reflector 41 Half mirror 42 Surface reflector 43 Surface reflector 44 Surface reflector 45 Surface reflector 46 Condensing lens 47 Condensing lens 48 Condensing lens 51 Photo receiving element assembly 52 Photo receiving element 53 Photo receiving element 54 Photo receiving element 55 Laser beam 56 Laser beam 57 Laser beam

Claims (2)

[Claims] [Claim 1] A combustor body forming a sealed combustion chamber inside and having an observation window, a heater attached to an outer surface of the combustor body, and detecting the temperature of the combustion chamber. a temperature detector, a liquid fuel oil supply device that supplies a predetermined amount of liquid fuel oil to the combustion chamber, an air supply device that supplies air to the combustion chamber, and an agitator having a stirring member movable in the combustion chamber. A constant-volume combustion device for evaluating combustion characteristics of liquid fuel oil, comprising: and a spark plug capable of forming a spark within the combustion chamber. 2. The constant volume combustion apparatus for evaluating combustion characteristics of liquid fuel oil according to claim 1, further comprising a pressure detector for detecting the pressure within the combustion chamber.