CN109827704B

CN109827704B - Microscale detonation thrust measuring device based on suspension oscillation method

Info

Publication number: CN109827704B
Application number: CN201910151375.0A
Authority: CN
Inventors: 王可; 赵明皓; 郑家炜; 何建男; 范玮; 李江红
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2019-02-28
Filing date: 2019-02-28
Publication date: 2020-08-25
Anticipated expiration: 2039-02-28
Also published as: CN109827704A

Abstract

The invention designs a microscale detonation thrust measuring device based on a pendulous pendulum method. The device utilizes adjusting nut to adjust the whole levelness of pendulum system, and the ceramic bearing that adopts low frictional resistance can reduce system's resistance to minimum simultaneously, adopts non-contact measurement and control in addition, can measure the thrust of microscale knockings more accurately to through measuring the swing curve of pendulum platform under the no-load condition, still can revise the data that the later stage obtained, further reduce measuring error. The device solves the problems that the friction resistance of the conventional pendulum suspension system is large, the pendulum suspension system does not horizontally swing, and the resistance caused by the power supply and measurement circuit of the detonation tube is large, and can be used in the fields of detonation propulsion, detonation experiments, thrust measurement of a micro propeller and the like.

Description

Microscale detonation thrust measuring device based on suspension oscillation method

Technical Field

The invention relates to the field of micro-scale detonation thrust measurement, in particular to a micro-scale detonation thrust measurement device based on a suspension method.

Background

The micro-scale detonation is generally referred to as detonation in a combustor with an equivalent diameter of a few tenths to a few millimeters, and has the characteristics of less environmental pollution and high energy density compared with a chemical battery-based power source. In addition, unlike common micro-scale combustion, the detonation can generate high-speed, high-temperature and high-pressure combustion waves instantly, has a simple structure and no rotating parts, and theoretically meets the requirements of small volume, light weight and high energy density required by a micro-power device. Therefore, the micro-scale detonation combustion has wider research prospect for providing power for small devices. At present, because the conventional thrust measuring device is mainly used for a large-scale combustor, the measurement result is less affected by the measurement error generated by the conventional thrust measuring device, and the thrust generated by micro-scale detonation is relatively less, if the conventional thrust measuring device is used for measurement, the measurement result is greatly affected by the measurement error, and even the thrust is submerged, so that the high-precision micro-scale detonation thrust measuring device is urgently needed.

Currently, there are two main methods for knock thrust measurement, direct measurement and indirect measurement. The direct measurement method is that the thrust of the detonation engine is directly measured by a sensor on a test bed, the engine is supported on a test bed through a rolling bearing, the other group of rolling bearings is used for limiting the radial movement of the engine, so that the engine can only move along the axial direction, the thrust generated by the engine during working is transmitted to the piezoelectric type force sensor through the force transmission mandril, and the time domain waveform of the pulse thrust can be obtained, then, the instantaneous thrust waveform in a certain time is integrated with the time, and the average value is taken to obtain the average thrust value of the engine under a certain working condition, but for micro-scale knocking, the direct measurement method is not suitable for the thrust measurement of microscale knocking because the friction resistance of the bearing on the test run rack, the friction resistance of the piezoelectric force sensor and the measurement error of the test run rack can greatly influence the measurement result.

The indirect measurement method is to measure the physical parameters related to the thrust of the engine, such as angle, displacement, torque and the like, and then calculate the magnitude of the thrust through a formula. The common indirect measuring device has a balance type structure, a torsional pendulum type structure and a suspended pendulum type structure, wherein the principle of the suspended pendulum type structure is simplest and easy to realize, the measuring precision is high, and the sensitivity can be adjusted by changing the length of the swing arm, so that the indirect measuring device is widely researched. However, the testing system of the existing pendulum type thrust measuring device still has some defects. For example, the suspension pendulum device designed by Kiyanda in studying the Impulse generated by the single Pulse Detonation tube is heavy, and a Power supply circuit and an air supply device are connected between the suspension pendulum system and the outside, which greatly increase the resistance during the suspension pendulum movement, thereby affecting the measurement accuracy of the system, and furthermore, when a thin wire or a steel wire is used as the pendulum rope, the levelness of the suspension pendulum is difficult to adjust, thereby the gravity center of the suspension pendulum device cannot be accurately measured, and a large measurement error is caused (Kiyanda C, Tanguay V, Higgins a J, et al. effect of Transient gasdynamic processing on the Impulse of Pulse degradation Engines [ J ]. Journal of Impulse degradation Engines, 2002,18(5):1124 1126.).

Therefore, in order to solve a series of problems that the levelness of the suspension pendulum device is difficult to adjust, the power supply and measurement line resistance of the detonation tube is large, the mechanical friction of a measurement system is large and the like, the invention designs the microscale detonation thrust measurement device based on the suspension pendulum method.

Disclosure of Invention

Technical problem to be solved

At present, a pendulous pendulum type thrust measuring device applied to the field of detonation has a large detonation tube size (generally, the inner diameter is larger than 10cm, and the tube length is larger than 1m), at the moment, the influence of friction resistance and non-horizontal swinging of a pendulous pendulum and the influence of resistance brought by power supply and a measuring circuit of the detonation tube on detonation thrust measurement are small, but when the pendulous pendulum type thrust measuring device is applied to microscale detonation thrust measurement, the problems bring large influence on the thrust measurement of the detonation tube, and even the deviation of a measuring result is more than 50%. Therefore, in order to overcome the defects of the existing suspension pendulum measurement technology, the invention designs a microscale detonation thrust measurement device based on a suspension pendulum method, which can greatly reduce the influence of the problems by means of devices such as a ceramic bearing with low friction resistance, a specially-made suspension pendulum platform, a high-precision displacement sensor, a high-speed camera and the like, thereby realizing high-precision measurement of microscale detonation thrust and simultaneously exploring the position and the detonation mode of a detonation point in a detonation tube. The device can be applied to the fields of detonation propulsion, detonation experiments, thrust measurement of miniature propellers and the like.

The technical scheme of the invention is as follows:

microscale detonation thrust measurement device based on suspension pendulum method, including swing subassembly, suspension pendulum platform subassembly, fixing device, detonation tube 9, measurement system and ignition system, its characterized in that: the swing assembly, the suspended pendulum platform assembly and the fixing device form a suspended pendulum system together, and the whole levelness of the suspended pendulum system can be conveniently adjusted through the adjusting nut 15; the ignition system is arranged in an igniter seat 13 below the pendulous platform 11 and is fixed by bolts, and the mixed gas in the detonation tube 9 can be ignited by remote control to eliminate the influence of a lead on pendulous oscillation; the measuring system depends on non-contact measurement, the horizontal displacement of the suspension pendulum device is measured by emitting and receiving laser through the displacement sensor 18, and in addition, the high-speed camera 19 is used for shooting the ignition and propagation process of gas in the detonation tube, so that the analysis of a detonation point and a detonation mode is facilitated.

The swing assembly is composed of four carbon fiber rods 14, eight ceramic bearings 17 with low friction resistance and eight bearing seats 16, the ceramic bearings 17 are installed in the bearing seats 16 and are fixed by elastic check rings, wherein the ceramic bearings 17 are the most important of the system, and according to design requirements, the ceramic bearings 17 with small friction resistance and certain load capacity are selected to reduce measurement errors as much as possible. Then insert carbon fiber pole 14 one end in the preformed hole of bearing frame 16, rely on adjusting nut 15 of hole outer wall to fix and adjust the downthehole degree of depth of carbon fiber pole 14 to accomplish the connection of 14 one ends of carbon fiber pole, then also carry out the same operation to its other end and other carbon fiber poles, install the swing subassembly on pendulum platform 11 at last, and finely tune adjusting nut 15, make the whole level that reaches of pendulum device, eliminate the influence of non-horizontal swing.

The suspension platform assembly is composed of an integrated suspension platform 11, a detonation tube fixing block, a reflecting table 5 and a bearing shaft 1, and machining materials of the suspension platform assembly are aviation aluminum, so that the weight of the device can be reduced. The suspension platform 11 is a cuboid structure, and four groups of mutually parallel bosses 10 are processed above the suspension platform and used for mounting a swing assembly; and each surface is provided with a reserved hole for installing a level gauge, a detonation tube fixing block, a reflecting table 5, an ignition system and the like. During installation, the swing components corresponding to the bosses 10 of the suspension platform 11 are installed on the bosses and are fixed by the bearing shafts 1 and the nuts, the reflecting table 5 is fixed on the side wall of the suspension platform, the ignition system is installed on the igniter base 13, and finally the detonation tube 9 and the upper and lower fixing blocks thereof are installed.

The fixture is similar to the integrated suspended pendulum platform 11 except that it has only four circular through holes for installing the expansion bolts and fixing them to the roof, and then installing the pendulum assembly thereon.

The detonation tube 9 is a transparent straight tube with a smooth inner wall, and the front end of the detonation tube is provided with a detachable ignition head 2 for air inlet and ignition. During the installation, place the detonation pipe on two lower fixed blocks 3, then place upper fixed block 8 to fix with the bolt, accomplish the installation, can select the fixed block of corresponding size according to the external diameter of detonation pipe simultaneously, in order to satisfy the experimental requirement.

The measuring system consists of a high-speed camera 19 and a displacement sensor 18, wherein the high-speed camera 19 is used for shooting the detonation and propagation processes of the mixed gas in the detonation tube 9; the displacement sensor 18 is used for measuring the horizontal displacement of the suspended pendulum platform 11, and further calculating the thrust generated by the detonation tube. The most beneficial effect of using the two instruments is that non-contact measurement can be realized, and the influence of the resistance of an external circuit on a pendulum suspension system is avoided.

The ignition system is divided into a controller and an ignition device, wherein the ignition device is arranged on the suspended platform 11 and realizes ignition through electric spark discharge; the controller is used for remote control, and synchronous triggering of the ignition device and the measuring device can be realized. The detonation of the mixed gas in the detonation tube is realized through non-contact control, so that the frictional resistance of the system can be reduced.

Advantageous effects

By adopting the microscale detonation thrust measuring device provided by the invention, the thrust of microscale detonation can be accurately measured. According to the invention, the carbon fiber rod is used as the swing assembly for the first time, and the levelness of the suspended pendulum is adjusted by using the adjusting nut, so that the problem that the levelness of the conventional rope-type suspended pendulum is difficult to adjust is solved; meanwhile, the ceramic bearing with low friction resistance is adopted as a rotating device, so that the resistance of the suspended pendulum during swinging can be greatly reduced, a free swinging curve of the suspended pendulum under the no-load condition can be measured by using a displacement sensor, the damping coefficient of the suspended pendulum can be reversely worked out according to a suspended pendulum motion equation, and the measured thrust can be corrected; in addition, the measuring system and the ignition system are in direct contact with the suspended pendulum to measure and control ignition, so that the influence of an external circuit on the measurement precision of the suspended pendulum is avoided; the invention has the advantages that the micro-scale detonation is particularly suitable for carrying out thrust measurement on the detonation tube with the equivalent diameter between a few tenths and a few millimeters, the space of the suspension swing platform is larger, the detonation tube is simpler to replace, the experimental efficiency can be greatly improved, and the experimental time is saved.

Drawings

Fig. 1 is a schematic view of the overall assembly of the thrust measuring device of the present invention (partially installed and not including the measuring device and ignition system).

Fig. 2 is a view (bottom view) of a suspended platform assembly of the thrust measurement device of the present invention.

Fig. 3 is an overall schematic view of a swing assembly of the thrust measuring device of the present invention.

Fig. 4 is a schematic view of the overall measurement structure of the thrust measuring device of the present invention.

In the figure, 1 bearing shaft 2, a lower fixed block 3 of a detonation tube ignition head, 4 an ignition wire outlet, 5 a reflection table, 6 and a weight-reducing square hole

7 level gauge seat 8 upper fixed block 9 detonation tube 10 dangling boss 11 dangling platform 12 fixed hole 13 igniter seat 14 carbon fiber rod 15 adjusting nut 16 bearing seat 17 ceramic bearing 18 laser displacement sensor 19 high speed camera

20 ignition wire.

Detailed description of the preferred embodiments

The present invention will be described in further detail with reference to the accompanying drawings. The method for measuring the thrust of the microscale detonation tube comprises the following steps of:

step one, installing a swing assembly, inserting one end of a carbon fiber rod 14 into a preformed hole of a bearing seat 16, fixing and adjusting the depth of the carbon fiber rod 14 in the hole by means of an adjusting nut 15 on the outer wall of the hole, so that connection of one end of the carbon fiber rod 14 is completed, then carrying out the same operation on the other end of the carbon fiber rod and other carbon fiber rods 14, then placing a ceramic bearing 17 into the bearing seat 16, and fixing the ceramic bearing by using an elastic check ring.

And step two, mounting the fixing device on the roof and fixing the fixing device by using expansion screws. Then the four groups of swing assemblies are sequentially arranged on a boss 10 of the fixing device through a bearing shaft 1, and the bearing shaft 1 is fixed through a nut.

And step three, installing the detonation tubes 9, selecting corresponding fixed blocks according to the tube diameters of the detonation tubes 9, then installing the two lower fixed blocks 3 on the pendulous platform 11, placing the detonation tubes 9 above the pendulous platform, installing the fixed blocks 8, and finally fixing the detonation tubes 9 by bolts to finish the installation of the detonation tubes 9.

And step four, installing an ignition system, namely, firstly, powering off the ignition system, then placing an igniter on an igniter seat 13 on the lower side of the suspended pendulum platform 11, fixing the igniter by using a nut, and finally, enabling an ignition wire 20 to penetrate through an ignition wire outlet 4 from the lower side and be connected with a detonation tube ignition head 2 so as to supply power to a detonation tube 9 above the suspended pendulum platform 11.

And step five, installing the reflecting table 5 and the level meter on the suspended pendulum platform 11, then sequentially connecting the four swinging assemblies to the suspended pendulum platform 11, observing the level meter in real time, and correspondingly finely adjusting the adjusting nut 15 to enable the suspended pendulum system to be horizontal as a whole.

And step six, mounting the high-speed camera 19, firstly connecting the high-speed camera 19 with a computer, setting image parameters by using related software, then adjusting the height and direction of a tripod to enable the detonation tube 9 to be just positioned at the center of an image, and finally focusing until the inner cavity of the detonation tube 9 can be clearly seen.

And step seven, installing the laser displacement sensor 18, enabling the single laser beam emitted by the laser displacement sensor to vertically irradiate on the reflecting table 5 of the suspended pendulum platform 11, and then adjusting the horizontal distance between the sensor 18 and the suspended pendulum platform 11, so that the suspended pendulum platform can not impact the displacement sensor 18 during movement and can move within the measuring range of the sensor 18.

And step eight, opening an air charging device to fill mixed air for the detonation tube 9, and then starting each measuring system and each ignition system. After the inflation is finished, the inflation device is removed, when the pendulous platform 11 is completely static, the measurement and ignition are started, at the moment, the high-speed camera 19 shoots the detonation process of the gas in the detonation tube, the displacement sensor 18 records the relevant data of the oscillation process of the pendulous platform 11 so as to carry out relevant analysis, and according to calculation, the overall measurement error of the device is less than 1%.

And step nine, closing each measuring instrument, disassembling the suspended pendulum measuring device, sealing the bearing 17 by using a plastic film to prevent dust from entering the bearing ball, thereby completing the experimental process of the microscale detonation thrust measurement, and finally performing related analysis and calculation according to the measured data.

While the present invention has been described in detail and with reference to the drawings and the detailed description thereof, it is not intended to limit the invention to the embodiment, but it is possible for those skilled in the art to make various changes and modifications without departing from the spirit of the invention.

Claims

1. Microscale detonation thrust measurement device based on pendulous pendulum method, including swing subassembly, pendulous pendulum platform subassembly, fixing device, detonation tube, measurement system and ignition system, its characterized in that: the swing assembly, the suspended pendulum platform assembly and the fixing device form a suspended pendulum system together, and the whole levelness of the suspended pendulum system can be conveniently adjusted through the adjusting nut; the swing assembly comprises four carbon fiber rods, eight ceramic bearings with low friction resistance and eight bearing seats, the carbon fiber rods are adopted to replace traditional ropes, the rigidity advantage of the carbon fiber rods can be fully achieved, the weight of the swing assembly is light, deformation cannot occur in the swing process, thrust loss can be reduced, the depth of the carbon fiber rods in the reserved holes can be fixed and adjusted through adjusting nuts on the bearing seats, the whole suspension device is made to be horizontal, and the influence of non-horizontal swing is eliminated; the suspension platform assembly consists of an integrated suspension platform, a detonation tube fixing block, a reflecting table and a bearing shaft, wherein the integrated suspension platform is made of aviation aluminum, the integrated suspension platform is of a cuboid structure, four groups of mutually parallel bosses are processed above the integrated suspension platform and used for mounting the swinging assembly, each group of bosses consists of two bosses, one boss is provided with a cylindrical through hole, and the other boss is provided with a semi-square semi-circular hole and used for being matched with the bearing shaft; different reserved holes are formed in each surface of the platform and used for mounting a level gauge, a detonation tube fixing block, a reflecting table and an ignition system; the reflecting table is used for receiving and reflecting signals of the displacement sensor so as to complete the measurement of the displacement; the bearing shaft is a cylindrical step shaft, one side of the bearing shaft is cut into a square shape and used for being fixed on the boss, the other side of the bearing shaft is turned with threads and used for installing a fixing nut, the middle of the bearing shaft is used for placing a bearing, and the position of the bearing shaft is fixed by an elastic retainer ring and a step; the ignition system is arranged below the suspended pendulum platform and fixed by bolts, and mixed gas in the detonation tube can be ignited by remote control, so that the influence of a guide wire on the suspended pendulum is eliminated; the measuring system depends on non-contact measurement, the horizontal displacement of the suspension pendulum device is measured by emitting and receiving laser through the displacement sensor, and in addition, a high-speed camera is used for shooting the ignition and propagation process of gas in the detonation tube, so that the analysis of a detonation point and a detonation mode is facilitated.

2. The microscale knocking thrust measuring device based on the pendulous method according to claim 1, wherein the bearing seat is formed by splicing a cuboid and a semi-cylinder, a carbon fiber rod reserved hole is formed in the cuboid and used for placing the carbon fiber rod, and threaded holes are formed in two sides of the outer wall and used for installing adjusting nuts; the semi-cylinder is internally provided with a bearing hole which has the property of a common bearing seat and can be used for placing an elastic check ring to fix the bearing.

3. The microscale detonation thrust measuring device based on the pendulous method of claim 1, characterized in that the detonation tube is fixed by upper and lower fixed blocks of the pendulous platform, and the fixed block with corresponding size can be selected according to the outer diameter of the detonation tube to meet experimental requirements.

4. The microscale knocking thrust measuring device based on the pendulous method according to claim 1, characterized in that the measuring system is composed of a high-speed camera and a displacement sensor, wherein the high-speed camera is used for shooting the detonation and propagation process of the mixed gas in the knocking pipe; the displacement sensor is used for measuring the horizontal displacement of the suspension platform and further calculating the thrust generated by the detonation tube; the system realizes synchronous displacement measurement and flow field observation, and the pendulum suspension system gets rid of unnecessary constraint and avoids thrust loss through non-contact measurement.

5. The microscale knocking thrust measuring device based on the pendulous method according to claim 1, wherein the ignition system is divided into a controller and an ignition device, wherein the ignition device is installed on the pendulous platform and realizes ignition through electric spark discharge; the controller is used for remote control and can accurately and simultaneously control the ignition and the triggering of the measuring device; the detonation of the mixed gas in the detonation tube is realized through non-contact control, so that the frictional resistance of the system can be reduced.