CN113390765B - Method for researching influence of shock wave on evaporation process of fuel liquid drops under supersonic airflow - Google Patents

Abstract

The invention belongs to the technical field of scramjet engines and detonation engines, and in particular relates to a research method for the influence of shock waves on fuel droplet evaporation processes under supersonic airflow. The research method includes step 1: calculating the pressure value of a critical gas in a high pressure section; Step 2, pre-pressurization in the high pressure section; Step 3, measure the initial light intensity; Step 4, atomization; Step 5, measure the particle size distribution of the fuel droplets before the shock wave; Step 6, generate a shock wave; Step 7, measure the shock wave The particle size distribution of the fuel droplets during the interaction with the fuel droplets; step 8, measuring the particle size distribution of the fuel droplets after the shock wave; step 9, pressure relief; and step 10, data processing. The invention can realize the generation of the particle size of the fuel droplet and the measurement of the particle size of the fuel droplet while generating the shock wave in the experiment.

Description

A research method for the effect of shock wave on the evaporation process of fuel droplets under supersonic airflow

technical field

The invention belongs to the technical field of scramjet engines and detonation engines, and particularly relates to a research method for the influence of shock waves on fuel droplet evaporation processes under supersonic airflow.

Background technique

The scramjet is the power plant of the air-breathing supersonic vehicle, which generally includes four parts: the intake port, the isolation section, the combustion chamber and the tail nozzle. When the scramjet is working, it flows through the intake port to decelerate and pressurize, and then enters the combustion chamber through the isolation section at supersonic speed, and mixes and burns with the propellant carried by the aircraft in the combustion chamber, thereby converting the chemical energy of the propellant into Thermal energy, the high temperature and high pressure gas after combustion then expands through the tail nozzle to do work to convert the thermal energy into kinetic energy. Since scramjets do not need to carry oxidants and have a high specific impulse, they are favored in the aerospace and defense fields.

Since the airflow velocity at the inlet of the combustion chamber of the scramjet is supersonic, the residence time of the combustible mixture in the combustion chamber is extremely short, and the supersonic airflow at the inlet of the combustion chamber will generate shock waves under the action of the inner wall of the combustion chamber, which makes the environment in the combustion chamber change. It is even worse, which brings great difficulties to the mixing and combustion of fuel and incoming air. How to complete the injection, atomization, evaporation, mixing and combustion of fuel in a limited space and a very short time has become a difficult problem in the field of scramjet research. Among them, the evaporation process occupies a long time in the whole process, and affects the mixing and combustion process, and finally affects the release of fuel chemical energy. Therefore, it is of great significance to study the effect of shock waves on the evaporation process of fuel droplets under supersonic airflow.

Due to the existence of the shock wave, when the fuel droplet size is large, the droplet will be broken by the shock wave, and it is impossible to study the droplet evaporation law by measuring the particle size change. Relevant theories show that when the droplet size satisfies the Weber number below the critical Weber number, the droplet will not break up, and the droplet breakup problem can no longer be considered when studying the problem of droplet evaporation. However, the droplet diameter at this time is reduced to the order of micrometers, and there is the interference of shock waves, so the traditional measurement method will be difficult to perform the particle size measurement task at this time. In addition, the droplet generation method usually used produces large droplet size, which is difficult to meet the requirements of the experiment. Therefore, when studying the effect of shock waves on the evaporation process of fuel droplets under supersonic airflow, it is difficult for existing experimental devices to simultaneously meet the needs of generating shock waves, generating small droplets and measuring the particle size of small droplets under the interference of shock waves.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is aimed at the deficiencies of the above-mentioned prior art, and provides a research method for the influence of shock waves on the evaporation process of fuel droplets under supersonic airflow. The research method can realize the generation of fuel droplets and the measurement of the particle size of fuel droplets while the shock wave is generated experimentally.

The technical scheme adopted by the present invention to solve the technical problem is: a method for researching the effect of shock waves on the evaporation process of fuel droplets under supersonic airflow, which is characterized in that the shock wave tube includes a shock wave tube along the movement direction of the incident shock wave. The high-pressure section, the low-pressure section and the experimental section are arranged in sequence, and a diaphragm is arranged between the high-pressure section and the low-pressure section; the research method includes the following steps:

Step 1. Calculate the pressure value of the critical gas in the high pressure section: the critical gas pressure value in the high pressure section is p ₄ The gas pressure in the low pressure section is p ₁ , and the ratio of p ₄ to p ₁ is p ₄₁ ; determine the required excitation Wave Mach number Ma _s , measure p ₁ , and then obtain the pressure value p ₄ of the critical gas in the high-pressure section through the relationship between p ₄₁ and Ma _s ;

Step 2, pre-pressurizing the high-pressure section: pressurizing the high-pressure section through the pressure control system, so that the gas pressure value p′ ₄ in the current high-pressure section is close to but less than p ₄ ;

Step 3. Measure the initial light intensity: use a multi-wavelength extinction method particle size measurement system to measure the initial light intensity before extinction;

Step 4. Atomization: start the air pump, the ultrasonic atomization system is connected to the experimental section, and the ultrasonic atomizer in the ultrasonic atomization system sprays the atomized fuel droplets into the stroke gas in the experimental section through the atomization transition section. Sol until reaching the set concentration;

Step 5. Measure the particle size distribution of the fuel droplets before the shock wave: at the same time of atomization, the particle size distribution of the fuel droplets in the experimental section is measured in real time by using the multi-wavelength extinction method to measure the particle size distribution, and the wavefront fuel is obtained. Variation curve of droplet size distribution with time;

Step 6. Generate shock wave: pressurize the high-pressure section through the pressure control system, so that the gas pressure value in the current high-pressure section reaches p ₄ ; at this time, the diaphragm is ruptured, and the gas in the high-pressure section quickly rushes into the low-pressure section and the experiment is performed. section, and shock waves are generated in the low pressure section and the experimental section;

Step 7. Measure the particle size distribution of fuel droplets during the interaction between the shock wave and the fuel droplets: when the shock wave moves, the multi-wavelength extinction method for particle size measurement system measures the particle size distribution of the fuel droplets in the experimental section in real time, And obtain the change curve of fuel droplet size distribution with time during the interaction between shock wave and fuel droplets; at the same time, through the installation distance between several low-pressure section piezoelectric sensors and the distance between several low-pressure section piezoelectric sensors when the shock wave occurs The response time difference is calculated at multiple groups of shock velocities, and the average value of multiple groups of shock velocities is taken as the actual shock velocity Δv, thereby obtaining the actual shock Mach number Ma _s ;

Step 8. Measure the particle size distribution of the fuel droplets after the shock wave: After the shock wave, the particle size measurement system by the multi-wavelength extinction method continues to measure the particle size distribution of the fuel droplets in the experimental section in real time until the particle size distribution by the multi-wavelength extinction method is measured. The diameter system is restored to the original light intensity, and the measurement is stopped, so as to obtain the variation curve of the particle size distribution of the fuel droplets with time after the shock wave;

Step 9. Pressure relief: remove the exhaust gas in the shock tube through the pressure control system;

Step 10. Data processing: the computer mainframe is based on the multi-wavelength extinction method to measure the particle size distribution of the fuel droplets during the interaction between the shock wave and the fuel droplets. The time-dependent curve and the particle size distribution of the fuel droplets after the wave The relationship between the curve with time and the actual shock Mach number Ma _s is obtained to obtain the relationship between the fuel droplet evaporation rate and the shock Mach number Ma _s .

As a further preference of the present invention, in step 1, p ₁ is atmospheric pressure or a preset specific pressure value; the relational formula between p ₄₁ and _Mas is:

where a ₁₄ is the sound speed ratio, which can be expressed as:

Among them, γ ₁ is the specific heat ratio of the gas in the low pressure section, γ ₄ is the specific heat ratio of the gas in the high pressure section, M ₁ is the molecular weight of the gas in the low pressure section, M ₄ is the molecular weight of the gas in the high pressure section, and T ₁ is the initial stage of the gas in the low pressure section. temperature, T4 is the initial temperature of the gas in the high pressure section _.

As a further preference of the present invention, after the fuel droplets injected into the experimental section in step 4 reach the set concentration, the space between the ultrasonic atomization system and the experimental section is closed.

As a further preference of the present invention, the multi-wavelength extinction method particle size measurement system includes a fiber coupler, a diffraction grating, a photodetector, a signal adjustment circuit and a data acquisition card; in steps 3, 5, 7 and 8, the The coupler couples the optical paths of multiple wavelengths into one optical path and outputs it through the experimental section, and then divides it into optical paths with the same number of paths and wavelengths through the diffraction grating; the photodetector converts the detected light intensity signals of each wavelength into The electrical signal of the fuel droplet is transmitted to the data acquisition card through the signal adjustment circuit, so as to invert the change of the particle size and concentration of the fuel droplet, and obtain the corresponding change curve of the particle size distribution of the fuel droplet with time.

As a further preference of the present invention, in step 7, the actual shock Mach number Ma _s =Δv/a, and a is the speed of sound.

As a further preference of the present invention, the several low-voltage segment piezoelectric sensors are the low-voltage segment I piezoelectric sensors, the low-voltage segment II piezoelectric sensors, and the low-voltage segment III piezoelectric sensors arranged in sequence along the movement direction of the incident shock wave; the actual shock wave The calculation formula of speed Δv is as follows:

where:

The installation distance between the piezoelectric sensor No. I in the low-voltage section and the piezoelectric sensor in the low-voltage section II is ΔL ₁ ,

The response time difference between the piezoelectric sensor No. I in the low pressure section and the piezoelectric sensor No. II in the low pressure section is Δt ₁ ,

The installation distance between the piezoelectric sensor of the low-voltage section I and the piezoelectric sensor of the low-voltage section III is ΔL ₂ ,

The response time difference between the piezoelectric sensor No. I in the low pressure section and the piezoelectric sensor No. III in the low pressure section is Δt ₂ ,

The installation distance between the piezoelectric sensor of the low-voltage section II and the piezoelectric sensor of the low-voltage section III is ΔL ₃ ,

The response time difference between the piezoelectric sensor No. II in the low-voltage section and the piezoelectric sensor in the low-voltage section III is Δt ₃ .

Through the above technical solutions, with respect to the prior art, the present invention has the following beneficial effects:

1. During the experiment of the present invention, the micron-scale fuel droplets are generated by the ultrasonic atomization system and sprayed into the experimental section, and then the diaphragm is ruptured by pressurizing the high-pressure section, so that the low-pressure section and A shock wave is generated in the experimental section; at the same time, the particle size of the micron fuel droplets in the experimental section is measured in real time according to the multi-wavelength extinction method particle size measurement system.

2. The present invention can select diaphragms of different intensities to generate shock waves of different intensities according to the needs of the experiment, and because the inner section of the shock tube is all rectangular, the generated shock waves do not need to go through the circle-to-square section in the previous design scheme, so The resulting shock waves are of better quality.

3. The present invention detects the time difference between each low-voltage segment piezoelectric sensor and other low-voltage segment piezoelectric sensors to detect the pressure change through the installed several low-voltage segment piezoelectric sensors. The installation distance between the piezoelectric sensors in other low-voltage sections is used to calculate a plurality of shock wave velocities, and then the average value of the shock wave velocities is calculated to reduce the error.

4. The first detachable observation window and the second detachable observation window of the present invention can provide measurement channels for various measurement methods, and can meet the measurement requirements under different experimental conditions.

5. The atomizer adapter section of the present invention can not only connect the ultrasonic atomizer and the shock tube, but also can drive the sealing rod and other structures to move quickly through the cam handle to achieve rapid sealing; the cam handle does not require additional control The device can be locked by the gravity of the cam handle itself, so the failure rate is low and the reliability is high.

6. The selection of the laser light source array in the multi-wavelength extinction method particle size measurement system in the present invention is flexible, and light sources of different wavelengths can be selected and combined according to the extinction characteristics of the substances in the experimental section; the data acquisition card can be combined according to the sampling frequency. Choose as needed.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

FIG. 1 is a perspective view of the overall structure of the present invention.

FIG. 2 is a front view of the overall structure of the present invention.

3 is a top view of the overall structure of the present invention.

FIG. 4 is an assembly diagram of the sandwich section, diaphragm, high pressure section and low pressure I section of the present invention.

Figure 5 is an exploded view of the capsular segment and diaphragm of the present invention.

Figure 6 is an assembled view of the second removable viewing window of the present invention.

Figure 7 is an exploded view of the second removable viewing window of the present invention.

Figure 8 is a front view of the nebulizer adapter section of the present invention.

Figure 9 is a top view of the nebulizer adapter section of the present invention.

Fig. 10 is a perspective view of the adapter section of the atomizer of the present invention in a sealed state.

FIG. 11 is a perspective view of the adapter section of the atomizer of the present invention in an open state.

12 is a perspective view of the second blind hole plate of the present invention.

FIG. 13 is a perspective view of the transition section cavity of the present invention.

14 is a perspective view of the seal rod support plate of the present invention.

Fig. 15 is a perspective view of the seal rod linkage plate of the present invention.

Fig. 16 is a perspective view of the seal rod of the present invention.

17 is a perspective view of the cam handle of the present invention.

Fig. 18 is a perspective view of the packing nut of the present invention.

In the figure: 1. High pressure gas cylinder; 2. Pressure control cabinet; 3. The first blind hole plate; 4. High pressure section; 5. High pressure section piezoelectric sensor; Piezoelectric sensor of low voltage section I; 9. low voltage section II; 10. piezoelectric sensor of low voltage section II; 11. piezoelectric sensor of low voltage section III; 12. Laser light source array; 13. Optical fiber; 14. Experimental section; 15 .Second blind hole plate; 16. Adapter section cavity; 17. Seal rod support plate; 18. Signal conditioner; 19. Photoelectric detector; 20. Diffraction grating; 21. Data acquisition card; 22. Diversion pipe 23. Ultrasonic atomizer; 24. Computer host; 25. Display; 26. Air pump; 27. Air pump; 28. Three-way pipe joint; 29. High pressure pipeline; 30. Intake pipeline; Pipe; 32. Sealing rod linkage plate; 33. Sealing rod; 34. Cam handle; 35. Piezoelectric sensor signal transmission line; 36. Optical fiber coupler; 37. The outer frame of the first observation window; 38. The inner frame of the first observation window; 39. The outer frame of the second observation window; 40. The inner frame of the second observation window; 41. The signal transmission line of the photodetector; 42. The diaphragm; 43. The adjustment screw; 44. The first observation window glass; Cotter pin; 47. Hexagon socket head screw; 48. Nut; 49. First O-ring; 50. Second O-ring; 51. Sealing ring compression nut; 52. V-ring.

Detailed ways

The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are all simplified schematic diagrams, and only illustrate the basic structure of the present invention in a schematic manner, so they only show the structures related to the present invention.

Example 1

This example provides a preferred implementation, as shown in Figures 1 to 18, a research device for the effect of shock waves on the evaporation process of fuel droplets under supersonic airflow, including a control device, a shock tube system, and an ultrasonic atomization system , pressure detection system and multi-wavelength extinction particle size measurement system, the specific structures of these systems are as follows:

As shown in Figure 1, the above-mentioned control device comprises a computer host 24 and a display 25, the display 25 is connected with the computer host 24, and the computer host 24 is respectively connected with the pressure detection system and the multi-wavelength extinction method particle size measurement system through a data line. The above-mentioned shock tube system includes a shock tube and a pressure control system, wherein:

As shown in FIG. 1 , the above-mentioned shock tube includes a high-pressure section 4, a low-pressure section and an experimental section 14 arranged in sequence along the moving direction of the incident shock wave. Preferably, the shock tube can be a shock tube with a rectangular section; One end of the low-pressure section is sealed with a first blind hole plate 3, and a diaphragm 42 is sealed at the junction of the high-pressure section 4 and the low-pressure section; the above-mentioned low-pressure section includes a low-pressure section 7 and a low-pressure section arranged in sequence along the direction of incident shock wave movement. Section II 9; the two opposite sides of the experimental section 14 are respectively provided with a first detachable observation window and a second detachable observation window. Preferably, the inner section of the experimental section 14 is designed to be rectangular, so as to ensure the smoothness of the inner surface while opening the window, and to avoid the introduction of complex wave systems due to the impact of the uneven inner surface on the shock front; two detachable observation windows and two The experimental section 14 between the detachable observation windows forms a measurement channel that is convenient for the measurement of the multi-wavelength extinction method particle size measurement system.

The present embodiment also includes a diaphragm section 6, which is used to clamp the diaphragm 42 and is arranged between the high-pressure section 4 and the low-pressure section, and is designed to separate the high-pressure section 4 and the low-pressure section before the diaphragm 42 is ruptured isolated to create different initial pressures. Preferably, the inner sections of the high pressure section 4, the sandwich section 6 and the low pressure section and the shape of the diaphragm 42 are all rectangular, so as to avoid the shock wave in the prior art that needs to go through a circular section and the geometry of the shock wave front changes. Impact on shock quality.

As shown in FIGS. 3 , 6 and 7 , the first detachable observation window includes a first observation window inner frame 38 , a first observation window outer frame 37 and a first observation window glass, and the second detachable observation window includes a second observation window The window inner frame 40 , the second observation window outer frame 39 and the second observation window glass 44 . The first observation window glass is located between the first observation window inner frame 38 and the first observation window outer frame 37. Preferably, the inner surface of the first observation window glass and the first observation window inner frame 38 are adjusted by the adjustment of 12 adjusting screws 43. The inner surfaces overlap. It is worth noting that during the adjustment process, the adjustment screw 43 should be adjusted diagonally. The second detachable observation window has the same structure as the first detachable observation window, and the second observation window glass 44 is located between the second observation window inner frame 40 and the second observation window outer frame 39 , preferably, through 12 adjustment screws 43 Under the adjustment action, the inner surface of the second observation window glass 44 coincides with the inner surface of the inner frame 40 of the second observation window. It is worth noting that during the adjustment process, the adjustment screws 43 should be adjusted diagonally. After the first detachable observation window or the second detachable observation window is assembled, the first detachable observation window or the second detachable observation window will be fixed to the experimental section 14 as a detachable whole through 14 connecting screws 45 , the inner surfaces of the first detachable observation window and the second detachable observation window after installation are flush with the inner surface of the experimental section 14 . That is, after installation, the inner surface of the first observation window glass, the inner surface of the first observation window inner frame 38 and the inner surface of the experimental section 14 are in the same plane, and the inner surface of the second observation window glass 44 and the second observation window inner frame 40 are in the same plane. The inner surface of the surface test section 14 is in the same plane, and because of the high machining precision of the parts, there is no obvious gap at the fitting place, and the introduction of complex wave systems due to uneven inner surface is avoided as much as possible.

As shown in Figures 1 and 2, the above-mentioned pressure control system is used to control the gas pressure introduced into the shock tube, and the pressure control system includes a high-pressure gas cylinder 1, a high-pressure pipeline 29, a pressure control cabinet 2, an intake pipeline 30, an exhaust gas Pipe 31 and tee fitting 28 . The high-pressure gas cylinder 1 is connected to the pressure control cabinet 2 through the high-pressure pipeline 29. The pressure control cabinet 2 is connected with an intake pipeline 30 and an exhaust pipeline 31. A hole is opened on the high-pressure section 4. Preferably, the hole is opened under the high-pressure section 4. On the side, the hole, the intake pipe 30 and the exhaust pipe 31 are connected through the tee pipe joint 28, and the pressure control system controls the intake and exhaust in the high pressure section 4 through the tee pipe joint 28, thereby controlling the pressure in the high pressure section 4. pressure. Preferably, the high-pressure gas cylinder 1 provides a pressure source for the high-pressure section 4 , and a pressure gauge, a pressure reducing valve and a stop valve are installed on the pressure control cabinet 2 for regulating and controlling the pressure in the high-pressure section 4 .

As shown in FIGS. 1 and 2 , the above-mentioned ultrasonic atomization system is used to inject micron-scale fuel droplets into the experimental section 14. The above-mentioned ultrasonic atomization system includes an ultrasonic atomizer 23, a guide pipe 22 and an atomizer. The transition section, wherein: the ultrasonic atomizer 23 stores liquid fuel, and the ultrasonic atomizer 23 has the advantages that the particle size of the liquid mist produced is small (the particle size of the liquid mist produced is in the order of microns) and the particle size distribution of the liquid mist produced is uniform. , which solves the problem of large particle size generated by the nozzle atomizer, and makes the particle size of the liquid mist generated small so that the problem of droplet breakage need not be considered in the experiment. One end of the diversion pipe 22 is connected with the ultrasonic atomizer 23 , and the other end is connected with the atomizer adapter section, and the atomizer adapter section is connected with the experimental section 14 .

As shown in FIGS. 8 to 11 , the above-mentioned atomizer adapter section includes a second blind hole plate 15 with a hole, an adapter section cavity 16 , a sealing rod supporting plate 17 with a hole, and a sealing rod linkage plate with a hole. 32 and several sealing rods 33. The second blind hole plate 15 with holes, the transition section cavity 16, and the sealing rod support plate 17 are assembled to form a cavity that communicates with the shock tube. The cavity is used to transfer into the shock tube and is generated by the ultrasonic atomizer 23. of liquid mist.

As shown in FIG. 1 , FIG. 8 , FIG. 9 and FIG. 12 , the above-mentioned second blind hole plate 15 is connected to the experimental section 14 on the shock tube, and the side of the second blind hole plate 15 with holes that is in contact with the experimental section 14 A boss is arranged in the middle, and a plurality of through holes are opened on the boss. The droplets are distributed evenly after entering the shock tube. Preferably, the above-mentioned second blind hole plate 15 with holes is made of stainless steel, and a sealing ring groove is milled on the surface of the second blind hole plate 15 with holes connecting with the experimental section 14 for installing the first O-ring 49 Ensure the air tightness of the shock tube.

As shown in FIG. 8 , FIG. 9 and FIG. 13 , the adapter section cavity 16 is made of stainless steel, and is located between the second blind hole plate 15 with holes and the sealing rod support plate 17 . Preferably, the adapter section cavity 16 is fixedly connected to the second blind hole plate 15 through the cooperation of the socket head cap screws 47 and the nut 48, and sealing ring grooves are milled on the two end faces of the adapter section cavity 16 respectively for installing the second blind hole plate 15. Two O-rings 50 ensure the air tightness of the adapter section of the atomizer.

As shown in Figure 8, Figure 9 and Figure 14, the above-mentioned sealing rod support plate 17 is fixedly connected with the adapter section cavity 16 through the cooperation of the socket head cap screws 47 and the nuts 48, and the sealing rod supporting plate 17 is provided with a number of openings on the boss. A number of through holes are coaxial, and the corresponding number is 6. Preferably, the above-mentioned sealing rod support plate 17 is made of stainless steel, and its function is to provide support for the sealing rod 33 to meet the requirements of the axial movement of the sealing rod 33 . The sealing rod support plate 17 is machined with a light hole portion for installing the V-ring 52, and a thread for installing the sealing ring pressing nut 51 is machined. The function of the sealing ring compression nut 51 has two parts. One is to press the V-ring 52 to meet the sealing requirements; play a limiting role.

As shown in FIGS. 8 , 9 and 15 , the above-mentioned sealing rod linkage plate 32 is arranged on the side of the sealing rod supporting plate 17 away from the cavity 16 of the transition section, and the sealing rod linkage plate 32 is provided with a number of holes corresponding to those provided on the boss. A number of through holes are coaxial, and the corresponding number is 6, and rotary shafts are respectively provided on opposite sides of the sealing rod linkage plate 32 .

As shown in FIG. 9 , FIG. 10 and FIG. 16 , one end of the sealing rod 33 is provided with a conical surface structure, and the other end is provided with a screw thread, and the number of sealing rods 33 is correspondingly six. One end of the six sealing rods 33 with threads is connected with the sealing rod linkage plate 32; the conical surface structure on the sealing rod 33 can cooperate with the conical end of several through holes opened on the boss to form a seal, and when forming a seal, the convex The side of the stage facing the experimental section 14 overlaps with the bottom surface of the sealing rod 33 to form the reflection surface of the shock wave, so that the shock tube is sealed. Because it is a cone-surface fit and the shock wave rushes toward the bottom surface of the sealing rod 33 , during the shock wave impact process, the cone-surface fit will become tighter and tighter, which ensures the air tightness of the shock tube. Since the sealing rod 33 in this embodiment is a slender rod, a die steel with higher hardness is selected during processing to prevent easy deformation during processing, and chrome-plated after grinding to prevent rusting.

As shown in FIG. 8 to FIG. 11 and FIG. 17 , this embodiment also includes two cam handles 34 symmetrically installed on the sealing rod linkage plate 32 . Intermittent on and off. The cam handle 34 includes a cam and a handle. A hole is opened in the middle of the cam, and the handle is fixedly connected to the cam. The hole in the middle of the cam on the cam handle 34 is sleeved on the rotary shaft and fixed, and the cam handle 34 can be rotated only by pushing the handle. The rotation of the cam handle 34 drives the sealing rod linkage plate 32 to move along the axis direction of the hole on the sealing rod support plate 17, and then simultaneously drives the six sealing rods 33 to move along the axis direction of the above-mentioned through holes, so as to realize the connection between the sealing rod 33 and the hole with the hole. The contact and disengagement of the second blind orifice plate 15 further controls the start and stop of the liquid mist entering the shock tube. Preferably, a cotter pin 46 is installed on the rotary shaft of the cam handle 34 and located away from the sealing rod linkage plate 32 , and the cotter pin 46 restricts the axial movement of the cam handle 34 along the rotary shaft. The above-mentioned sealing rod linkage plate 32 can be moved quickly with the help of the cam handle 34, and can be locked by the gravity of the cam handle 34, avoiding the use of a separate control mechanism to control the movement and locking of the sealing rod linkage plate 32, thereby introducing other unreliable factor.

As shown in FIG. 11 , when the sealing rod 33 is out of contact with the second blind hole plate 15 with holes, the adapter section cavity 16 is in a state of communication with the experimental section 14 , and the liquid mist can be sprayed from the adapter section of the atomization adapter section. The cavity 16 enters the experimental section 14; as shown in FIG. 9 and FIG. 10 , when the sealing rod 33 contacts the second blind hole plate 15 with a hole, a fit is formed. At this time, the adapter section cavity 16 and the experimental section 14 are closed state.

As shown in FIG. 1 and FIG. 3 , the above-mentioned pressure detection system includes several piezoelectric sensors in the low pressure section and piezoelectric sensors 5 in the high pressure section. The plurality of low-voltage segment piezoelectric sensors include a low-voltage segment I piezoelectric sensor 8, a low-voltage segment II piezoelectric sensor 10, and a low-voltage segment III piezoelectric sensor 11, which are sequentially arranged along the motion direction of the incident shock wave. Preferably, three instrument holes are arranged at intervals above the low-voltage II section 9, and the low-voltage section I piezoelectric sensor 8, the low-voltage section II piezoelectric sensor 10 and the low-voltage section II piezoelectric sensor 10 and Piezoelectric sensor 11 in the low pressure section III. An instrument hole is opened above the high-voltage section 4, and the high-voltage section piezoelectric sensor 5 is installed in the instrument hole.

The high-voltage segment piezoelectric sensor 5, the low-voltage segment I piezoelectric sensor 8, the low-voltage segment II piezoelectric sensor 10, and the low-voltage segment III piezoelectric sensor 11 are respectively connected to one end of the piezoelectric sensor signal transmission line 35 through a data line. The other end of the signal transmission line 35 is connected to the computer host 24 . Preferably, the piezoelectric sensor signal transmission line 35 transmits the signals of the high-voltage segment piezoelectric sensor 5, the low-voltage segment I piezoelectric sensor 8, the low-voltage segment II piezoelectric sensor 10, and the low-voltage segment III piezoelectric sensor 11 to the computer after processing. host 24 and displayed on the display 25. Among them, the high pressure section piezoelectric sensor 5 is used to more accurately measure the pressure of the high pressure section 4 to record the actual working conditions of the experiment; the low pressure section I piezoelectric sensor 8, the low pressure section II piezoelectric sensor 10 and the low pressure section III pressure The electrical sensor 11 is used to detect the pressure on the low-voltage II segment 9 corresponding to the low-voltage segment piezoelectric sensor, and the computer host 24 records the pressure changes of the three low-voltage segment piezoelectric sensors. According to the measurement of the installation distance ΔL between any two piezoelectric sensors in the low pressure section and the time difference Δt when the pressure change is detected between any two piezoelectric sensors in the low pressure section, the speed of the shock wave Δv can be calculated, Δv=ΔL/Δt, and then Multiple sets of Δv values are averaged to reduce error.

As shown in FIG. 1 and FIG. 3, the multi-wavelength extinction particle size measurement system includes a laser light source array 12, an optical fiber 13, an optical fiber coupler 36, a diffraction grating 20, a photodetector 19, a signal conditioner 18, a data acquisition card 21 and Photodetector signal transmission line 41 . The optical fiber coupler 36, the optical fiber 13, and the laser light source array 12 are arranged on the side of the first detachable observation window facing the external environment in sequence; the diffraction grating 20 is arranged on the side of the second detachable observation window facing the external environment; the photodetector 19 Disposed in the reflection path of the diffraction grating 20 , the photodetector 19 is connected to the signal conditioner 18 , and the signal conditioner 18 is connected to the data acquisition card 21 . Preferably, the above-mentioned laser light source array 12 selects light sources of specific wavelengths for combination according to the extinction characteristic of the measured substance, which has certain flexibility.

The above-mentioned optical fibers 13 respectively transmit the light of each wavelength in the laser light source array 12 to the optical fiber coupler 36, and are coupled into one path of light through the fiber coupler 36 and emitted, and then the synthesized path of light is vertically injected through the first observation window glass. The sample cell in the experimental section 14 passes through the sample cell and vertically passes through the second observation window glass and exits, and then splits light under the action of the diffraction grating 20. The number of optical paths after splitting is consistent with the number of optical paths before coupling, that is, the wave number.

The above-mentioned photodetector 19 can detect the light intensity of each wavelength optical path after splitting, and convert the light intensity signal into an electrical signal, which is collected by the data acquisition card 21 after passing through the signal conditioner 18, and passes through the photodetector signal transmission line. 41 is transmitted to the computer host 24 . Under the control of the computer host 24, the changes of the light intensity signal can be continuously measured, and the changes in the particle size and concentration of the liquid mist in the experimental section 14 can be inverted through the inversion algorithm, and then the effect of the shock wave on the evaporation process of the fuel droplets at supersonic speed can be studied. influences. The extinction method has the advantages of small measurement lower limit and no need for calibration, so it can meet the needs of measuring the particle size change of micron-scale droplets in the presence of shock shock.

As shown in FIG. 2, the present embodiment also includes a suction pump 26, and a hole is provided on the low-pressure I section 7, and the hole is connected with the suction pump 26 through the suction pipe 27, and the suction pump 26 is used for suctioning and guiding the low-pressure section during atomization. air flow inside.

This embodiment also provides a method for researching the effect of shock waves on the evaporation process of fuel droplets under supersonic airflow, including the following steps:

Step 1. Calculate the pressure value of the critical gas in the high pressure section 4: the critical gas pressure value in the high pressure section 4 is p ₄ The gas pressure in the low pressure section is p ₁ , and the ratio of p ₄ to p ₁ is p ₄₁ ; The shock Mach number Ma _s is required, and p ₁ is measured, and then the pressure value p ₄ of the critical gas in the high-pressure section 4 is obtained through the relationship between p ₄₁ and Ma _s ;

Wherein, p ₁ is atmospheric pressure or a preset specific pressure value;

The relation between p ₄₁ and _Mas is:

where a ₁₄ is the sound speed ratio, which can be expressed as:

Among them, γ ₁ is the specific heat ratio of the gas in the low pressure section, γ ₄ is the specific heat ratio of the gas in the high pressure section, M ₁ is the molecular weight of the gas in the low pressure section, M ₄ is the molecular weight of the gas in the high pressure section, and T ₁ is the initial stage of the gas in the low pressure section. temperature, T4 is the initial temperature of the gas in the high pressure section _.

Step 2. Pre-pressurization of the high-pressure section 4: pressurize the high-pressure section 4 through the pressure control system, so that the current gas pressure value p ₄ ′ in the high-pressure section 4 is close to but less than p ₄ ;

Step 3. Measure the initial light intensity: use a multi-wavelength extinction method particle size measurement system to measure the light intensity after passing through the experimental section 14 and the two observation windows to obtain the initial light intensity before extinction.

The optical paths of multiple wavelengths are coupled into a bundle of optical paths through the fiber coupler 36 and the output passes through the first detachable observation window, the experimental section 14, the second detachable tube cleaning window in sequence, and then is divided into the number of paths and the number of wavelengths by the diffraction grating 20 The same optical path; the photodetector 19 converts the detected light intensity signal of each wavelength into an electrical signal and transmits it to the data acquisition card 21 through the signal adjustment circuit, thereby obtaining the light intensity signal before extinction.

Step 4, atomization: start the air pump 26, the ultrasonic atomization system is communicated with the experimental section 14, and the ultrasonic atomizer 23 in the ultrasonic atomization system sprays the atomized fuel droplets into the experimental section through the atomization transition section The aerosol is formed within 14 until the set concentration is reached;

Among them, by rotating the cam handle 34, the sealing rod linkage plate 32 is pushed to move in the direction of the adapter section cavity 16, so that the end of the conical surface structure of the sealing rod 33 is separated from the second blind hole plate 15 with holes, so that the ultrasonic atomization system The adapter section cavity 16 in the test section communicates with the experimental section 14 ; after the fuel droplets injected into the experimental section 14 reach the set concentration, turn the cam handle 34 to make the sealing rod linkage plate 32 move away from the adapter section cavity 16 . Move, so that the conical end of the sealing rod 33 is matched with the conical end of the through holes opened on the boss, so that the transition section cavity 16 of the ultrasonic atomization system and the experimental section 14 are closed.

Step 5. Measure the particle size distribution of the fuel droplets before the shock wave: at the same time of atomization, use the multi-wavelength extinction method to measure the particle size distribution of the fuel droplets in the experimental section 14 in real time to measure the particle size distribution, and obtain the wavefront fuel Variation curve of droplet size distribution with time;

The optical paths of multiple wavelengths are coupled into a beam of optical paths through the fiber coupler 36 and output through the experimental section 14, and then divided into optical paths with the same number of paths as the number of wavelengths by the diffraction grating 20; The wavelength light intensity signal and the converted electrical signal are transmitted to the data acquisition card 21 through the signal adjustment circuit, so as to obtain the light intensity after extinction by the aerosol, and then combine with the initial light intensity before extinction measured in step 3 to invert the fuel The change of droplet size and concentration can be used to obtain the variation curve of wavefront fuel droplet size distribution with time.

Step 6. Generate a shock wave: pressurize the high-pressure section 4 through the pressure control system, so that the current gas pressure value in the high-pressure section 4 reaches p ₄ ; at this time, the diaphragm 42 is ruptured, and the gas in the high-pressure section 4 quickly rushes into The low pressure section and the experimental section 14, and shock waves are generated in the low pressure section and the experimental section 14;

Step 7. Measure the particle size distribution of the fuel droplets during the interaction between the shock wave and the fuel droplets: when the shock wave moves, the multi-wavelength extinction method for particle size measurement system measures the particle size distribution of the fuel droplets in the experimental section 14 in real time. , and obtain the variation curve of the particle size distribution of fuel droplets with time during the interaction between the shock wave and the fuel droplets; at the same time, through the installation distance between the piezoelectric sensors in the low pressure section and the piezoelectric sensors in the low pressure section when the shock wave moves The response time difference between the multiple groups of shock velocities is calculated, and the average value of the multiple groups of shock velocities is taken as the actual shock velocity Δv, so as to obtain the actual shock Mach number Ma _s , Ma _s =Δv/a, a is the speed of sound;

The formula for calculating the actual shock velocity Δv is as follows:

where:

The installation distance between the piezoelectric sensor No. I in the low-voltage section and the piezoelectric sensor in the low-voltage section II is ΔL ₁ ,

The response time difference between the piezoelectric sensor No. I in the low pressure section and the piezoelectric sensor No. II in the low pressure section is Δt ₁ ,

The installation distance between the piezoelectric sensor of the low-voltage section I and the piezoelectric sensor of the low-voltage section III is ΔL ₂ ,

The response time difference between the piezoelectric sensor No. I in the low pressure section and the piezoelectric sensor No. III in the low pressure section is Δt ₂ ,

The installation distance between the piezoelectric sensor of the low-voltage section II and the piezoelectric sensor of the low-voltage section III is ΔL ₃ ,

The response time difference between the piezoelectric sensor No. II in the low-voltage section and the piezoelectric sensor in the low-voltage section III is Δt ₃ .

The optical paths of multiple wavelengths are coupled into a beam of optical paths through the fiber coupler 36 and output through the experimental section 14, and then divided into optical paths with the same number of paths as the number of wavelengths by the diffraction grating 20; The electrical signal converted from the wavelength light intensity signal is transmitted to the data acquisition card 21 through the signal adjustment circuit, so as to obtain the light intensity during the interaction between the shock wave and the fuel droplet, and then combined with the initial light intensity before extinction measured in step 3 , inversion of the changes in the particle size and concentration of the fuel droplets, and the time-dependent curve of the distribution of the fuel droplet size during the interaction between the shock wave and the fuel droplets is obtained.

Step 8. Measure the particle size distribution of the fuel droplets after the shock wave: after the shock wave, the multi-wavelength extinction method for particle size measurement system continues to measure the particle size distribution of the fuel droplets in the experimental section 14 in real time until the fuel droplets are completely evaporated. Stop the measurement to obtain the variation curve of the fuel droplet size distribution with time after the shock wave;

Step 9. Pressure relief: remove the exhaust gas in the shock tube through the pressure control system;

Step 10. Data processing: the computer host 24 according to the multi-wavelength extinction method to measure the particle size distribution curve of the fuel droplet size distribution with time during the interaction between the shock wave and the fuel droplet, and the fuel droplet size after the wave. The relationship between the curve of the distribution over time and the actual shock Mach number Ma _s was obtained, thereby obtaining the relationship between the fuel droplet evaporation rate and the shock Mach number Ma _s .

For the convenience of verifying the above-mentioned research method, the present embodiment provides a specific implementation scheme, which is as follows:

The experimental conditions are set as a shock wave of Mach 1.4 is obtained by driving air with nitrogen at room temperature, and the initial conditions are γ ₁ =γ ₄ =1.4; M ₁ =29, M ₄ =28; T ₁ =T ₄ =298K.

Step 1. Calculate p ₄₁ :

When the pressure of the low pressure section is atmospheric pressure, the required pressure of the high pressure section 4 is p ₄ =4.881atm≈0.495MPa.

According to the above experimental conditions, step 2: due to the small particle size of the droplets in the liquid mist, the evaporation life of the droplets is also short even at normal temperature and pressure, that is, the evaporation is completed in a short time, and the high-pressure section 4 is added. It takes a long time to pressurize, so it is too late to fill the low-pressure section of the shock tube with the required liquid mist and then pressurize the high-pressure section 4. In order to pass the shock wave as soon as possible after the liquid mist is distributed, the high pressure section can be pre-pressurized so that the pressure of the high pressure section 4 is slightly lower than the calculated value p ₄ =0.495MPa.

Step 3: After the atomization is completed, the high pressure section 4 is rapidly pressurized to the required pressure to rupture the diaphragm 42, thereby generating a shock wave. Since the pressure of the high pressure section 4 has been close to the required pressure p ₄ before, the time from continuing to pressurize to the rupture of the diaphragm 42 is very short. The actual shock wave velocity can be calculated from the distance and response time between several piezoelectric sensors in the low-voltage section.

To sum up, during the experiment of this embodiment, the ultrasonic atomization system is used to generate micron-scale fuel droplets and spray the micron-scale fuel droplets into the experimental section 14, and then pressurize the high-pressure section 4 to make the diaphragm 42 The particle size of the micron-scale fuel droplets in the experimental section 14 is measured in real time according to the multi-wavelength extinction method particle size measurement system.

In this embodiment, diaphragms 42 of different intensities can be selected according to experimental requirements to generate shock waves of different intensities, and because the inner cross-section of the shock tube is all rectangular, the generated shock waves do not need to go through the circle-to-square section in the previous design scheme, so The resulting shock waves are of better quality.

This embodiment detects the time difference between the detected pressure change between each low-voltage segment piezoelectric sensor and other low-voltage segment piezoelectric sensors by installing several low-voltage segment piezoelectric sensors. The installation distance between the piezoelectric sensors in the low-voltage section calculates multiple shock wave velocities, and then calculates the average value of the shock wave velocities to reduce errors.

The first detachable observation window and the second detachable observation window of this embodiment can provide measurement channels for various measurement methods, and can meet measurement requirements under different experimental conditions.

The selection of the laser light source array 12 in the multi-wavelength extinction method particle size measurement system in this embodiment is flexible, and light sources of different wavelengths can be selected and combined according to the extinction characteristics of the substances in the experimental section 14; the data acquisition card 21 can be combined according to the sampling frequency needs to be selected.

In this embodiment, the multi-wavelength extinction method is used to measure the particle size. When the particle size is measured by means of optics, the interaction between the shock wave and the liquid mist will affect the scattering of light, and the pressure and temperature after the shock wave will also increase. It has a certain influence on the scattering of light, so the measuring instrument that accepts the scattered light signal cannot meet the needs of the experiment. In the measurement process of the extinction method, since the transmitted light passing through the particle system is collected during the measurement, rather than the scattered light of the particles, the optical signal is stronger; in addition, the shock wave has little influence on the light intensity, so the extinction The method of measuring particle size can be used in experiments where shock shock is present. In addition, the extinction method not only collects the light intensity signal after passing through the particle system, but also collects the light intensity signal before passing through the particle system. It is an absolute measurement method and does not require calibration.

In this embodiment, a continuous laser light source is used, so the data collection frequency depends on the collection frequency of the data collection card 21, and data collection cards 21 with different collection frequencies can be selected according to the needs of the experiment. For example, the time for the shock wave to pass through the measurement area is in the order of microseconds, so a data acquisition card 21 with a collection frequency of 1 MHz can be used to ensure reliable data collection during the time the shock wave passes through. In order to collect more reliable data in a specific time, a data acquisition card 21 with a higher acquisition frequency can be used, so the selection of the acquisition frequency has flexibility.

In this embodiment, the wavelength selection of light in the multi-wavelength extinction method has flexibility. The choice of wavelength has an impact on the inversion of particle size, so the particle size distribution range can be measured in advance with the help of a mature particle size measuring device without shock shock, and an appropriate wavelength can be selected according to the measured particle size range to form the composition. required laser light source array 12 .

It will be understood by one of ordinary skill in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as herein, are not to be taken in an idealized or overly formal sense. explain.

The meaning of "and/or" in this application means that each of them exists alone or both are included.

The meaning of "connection" in this application may be a direct connection between components or an indirect connection between components through other components.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper side", "lower side", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description , rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, "first", "second", etc. Invention limitations.

Taking the above ideal embodiments according to the present invention as inspiration, and through the above description, relevant personnel can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the contents in the specification, and the technical scope must be determined according to the scope of the claims.

Claims (4)

1. A research method for influence of shock waves on a fuel liquid droplet evaporation process under supersonic airflow is characterized by comprising a shock tube, wherein the shock tube comprises a high-pressure section, a low-pressure section and an experimental section which are sequentially arranged along the movement direction of an incident shock wave, and a diaphragm is arranged between the high-pressure section and the low-pressure section; the research method comprises the following steps:

step 1, calculating the pressure value of critical gas in a high-pressure section: critical gas pressure value in the high pressure section is p ₄ The pressure value of the gas in the low-pressure section is p ₁ ，p ₄ And p ₁ Has a ratio of p ₄₁ (ii) a Determining the Mach number Ma of the required shock wave _s Measuring p ₁ Through p ₄₁ And Ma _s To obtain the pressure value p of the critical gas in the high-pressure section ₄ ；

Step 2, pre-pressurizing a high-pressure section: the high-pressure section is pressurized through a pressure control system, so that the gas pressure value p 'in the current high-pressure section' ₄ Close to but less than p ₄ ；

Step 3, measuring initial light intensity: measuring initial light intensity before extinction by adopting a multi-wavelength extinction method particle size measurement system;

step 4, atomization: starting an air pump, wherein an ultrasonic atomization system is communicated with an experimental section, and an ultrasonic atomizer in the ultrasonic atomization system sprays atomized fuel droplets into the experimental section through an atomization switching section to form aerosol until the concentration reaches a set concentration;

step 5, measuring the particle size distribution of the fuel droplets in the shock front: during atomization, a multi-wavelength extinction method measurement particle size system is adopted to measure the particle size distribution of the fuel droplets in the experimental section in real time, and a change curve of the particle size distribution of the wavefront fuel droplets along with time is obtained;

step 6, generating shock waves: by pressure controlThe system boosts the high-pressure section to make the gas pressure value in the current high-pressure section reach p ₄ (ii) a At the moment, the diaphragm is broken, the gas in the high-pressure section rapidly rushes into the low-pressure section and the experimental section, and shock waves are generated in the low-pressure section and the experimental section;

step 7, measuring the particle size distribution of the fuel droplets in the interaction process of the shock waves and the fuel droplets: when the shock wave moves, the particle size distribution of the fuel droplets in the experimental section is measured in real time by the particle size measuring system by the multi-wavelength extinction method, and a change curve of the particle size distribution of the fuel droplets along with time in the interaction process of the shock wave and the fuel droplets is obtained; meanwhile, a plurality of groups of shock wave speeds are calculated according to the installation distance between the piezoelectric sensors in the low-voltage sections and the response time difference between the piezoelectric sensors in the low-voltage sections during shock wave motion, the average value of the shock wave speeds is used as the actual shock wave speed delta v, and therefore the actual shock wave Mach number Ma is obtained _s ；

Actual shock Mach number Ma _s Δ v/a, a is the speed of sound;

the low-voltage section piezoelectric sensors are a low-voltage section I piezoelectric sensor, a low-voltage section II piezoelectric sensor and a low-voltage section III piezoelectric sensor which are sequentially arranged along the movement direction of the incident shock wave; the actual shock velocity Δ v is calculated as follows:

in the formula:

the installation distance between the low-voltage section I piezoelectric sensor and the low-voltage section II piezoelectric sensor is delta L ₁ ，

The response time difference between the low-voltage section I piezoelectric sensor and the low-voltage section II piezoelectric sensor is delta t ₁ ，

The installation distance between the low-voltage section I piezoelectric sensor and the low-voltage section III piezoelectric sensor is delta L ₂ ，

The response time difference between the low-voltage section I piezoelectric sensor and the low-voltage section III piezoelectric sensor is delta t ₂ ，

Low-voltage section II piezoelectric sensorThe installation distance between the sensor and the low-voltage section III piezoelectric sensor is delta L ₂ ，

The response time difference between the low-voltage section II piezoelectric sensor and the low-voltage section III piezoelectric sensor is delta t ₃ ；

Step 8, measuring the particle size distribution of fuel liquid drops after shock wave: after the shock wave is passed, the particle size distribution of the fuel droplets in the experimental section is continuously measured in real time by the particle size measuring system by the multi-wavelength extinction method until the fuel droplets are completely evaporated, and the measurement is stopped, so that a change curve of the particle size distribution of the fuel droplets after the shock wave along with the time is obtained;

step 9, pressure relief: removing waste gas in the shock tube through a pressure control system;

step 10, data processing: the host computer measures the change curve of the particle size distribution of the fuel droplets with time and the change curve of the particle size distribution of the fuel droplets with time after the interaction process of the fuel droplets and the actual shock Mach number Ma according to the multi-wavelength extinction method _s So as to obtain the evaporation rate of the fuel liquid drops and the shock wave Mach number Ma _s The relationship between them.

2. The method for researching the influence of the shock wave under the supersonic air flow on the evaporation process of the liquid droplets is characterized in that: in step 1 p ₁ The pressure is atmospheric pressure or a preset specific pressure value; p is a radical of formula ₄₁ And Ma _s The relation of (A) is as follows:

in the formula a ₁₄ For the sound speed ratio, it can be expressed as:

wherein, gamma is ₁ Specific heat ratio of gas in low-pressure section, gamma ₄ Specific heat ratio of gas in high pressure section, M ₁ Is lowMolecular weight of the ballast gas, M ₄ Is the molecular weight, T, of the gas in the high pressure section ₁ Is the initial temperature, T, of the gas in the low-pressure section ₄ Is the initial temperature of the gas in the high pressure section.

3. The method for researching the influence of the shock wave under the supersonic air flow on the evaporation process of the liquid droplets is characterized in that: and (4) after the fuel droplets sprayed into the experimental section in the step (4) reach the set concentration, sealing the space between the ultrasonic atomization system and the experimental section.

4. The method for researching the influence of the shock wave under the supersonic air flow on the evaporation process of the liquid droplets is characterized in that: the multi-wavelength extinction method particle size measurement system comprises an optical fiber coupler, a diffraction grating, a photoelectric detector, a signal adjusting circuit and a data acquisition card; in the steps 3, 5, 7 and 8, optical paths with multiple wavelengths are coupled into a beam of optical path through an optical fiber coupler and output to pass through an experimental section, and then the optical path with the same path number and wavelength number is divided into optical paths through a diffraction grating; the photoelectric detector converts detected light intensity signals of various wavelengths after light splitting into electric signals, and the electric signals are transmitted to the data acquisition card through the signal adjusting circuit, so that the change of the particle size and the concentration of the fuel droplets is inverted, and a corresponding change curve of the particle size distribution of the fuel droplets along with time is obtained.

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