阅读说明：本技术 一种模拟喷管中高超声速凝结过程的装置及诊断方法 (Device for simulating high supersonic velocity condensation process in spray pipe and diagnosis method ) 是由 金熠 黄生洪 王新宝 陈龙奎 王浩楠 李建斌 于 2021-08-27 设计创作，主要内容包括：本发明公开了一种模拟喷管中高超声速凝结过程的装置及诊断方法,包括模拟喷管装置和测量系统；所述模拟喷管装置包括试验段(1)、连接段(9)和真空段(11)；所述测量系统包括TDLAS测量系统、压力测量系统和高速摄影系统。所述装置基于稀疏波原理,利用稀疏波在壁面与高压段和低压段气体接触面反射,造成测点位置压力持续下降,进而增大过冷度,导致物质凝结,该装置保证了试验段流场的均匀性,同时实现了在较小时间尺度(<1ms)上实现物质的高超声速凝结过程。所述测量方法基于TDLAS测量原理,采用了多激光器信号耦合与一种新型基线拟合方法,保证了测量的多样性且时间分辨率在100kHz及以上。(The invention discloses a device for simulating a high supersonic velocity condensation process in a spray pipe and a diagnosis method, wherein the device comprises a simulation spray pipe device and a measurement system; the simulated nozzle device comprises a test section (1), a connecting section (9) and a vacuum section (11); the measurement system includes a TDLAS measurement system, a pressure measurement system and a high speed photography system. The device is based on the principle of sparse waves, the pressure at the position of a measuring point is continuously reduced by utilizing the reflection of the sparse waves on the gas contact surfaces of the wall surface and the high-pressure section and the low-pressure section, the super-cooling degree is further increased, and the material is condensed, so that the uniformity of a flow field of a test section is ensured, and the hypersonic condensation process of the material is realized on a smaller time scale (less than 1 ms). The measuring method is based on a TDLAS measuring principle, adopts multi-laser signal coupling and a novel baseline fitting method, ensures the measuring diversity and the time resolution ratio of 100kHz and above.)

1. The device for simulating the high supersonic velocity condensation process in the spray pipe is characterized in that: the device comprises a simulated nozzle device and a measuring system;

the simulated nozzle device comprises a test section (1), a connecting section (9) and a vacuum section (11), wherein the test section (1) is connected with the connecting section (9), and the connecting section (9) is fixed at an opening of the vacuum section (11); the test section (1) comprises a rectangular inner cavity (2), an optical fiber fixing device (6), a pressure control valve (7), an observation window (8) and 3 pressure measuring points (3, 4 and 5); the connecting section (9) comprises a rectangular frame, a pure copper conductor (10), a gasket, a polyester film (PET) and an electric fuse system; the vacuum section (11) comprises a cavity, an upper observation port (12), a rear observation port (13), a pumping pump (18) and a pressure display (14);

the measuring system comprises a TDLAS measuring system, a pressure measuring system and a high-speed photographing system; the TDLAS measuring system comprises a signal generator, a laser controller, a laser detector, a collimator, an optical fiber coupler, an etalon, a single mode optical fiber, a multi-mode optical fiber and an oscilloscope, wherein the signal generator outputs a voltage signal to the laser controller, the laser controller generates corresponding temperature and current to control the laser to output a laser signal, the laser signal is superposed into a laser signal through the optical fiber coupler to be transmitted in the single-mode optical fiber, a collimator is arranged at the outlet of the single-mode optical fiber and connected to an optical fiber fixing device (6) in the test section (1) to ensure the linear propagation in the flow field, the other end of the optical fiber fixing device (6) of the test section (1) is provided with a multimode optical fiber with a larger aperture than that of the single mode optical fiber to receive laser signals flowing through a flow field to be tested, and then a laser detector is utilized to convert the laser signals into electric signals to be transmitted to an oscilloscope; the pressure measurement system comprises three pressure sensors and pressure transmitters, wherein the three pressure sensors are axially distributed on pressure measurement points (3, 4 and 5) in the left direction, the middle direction and the right direction at the bottom of the test section (1), and pressure signals obtained by measurement are converted into electric signals by the pressure transmitters and transmitted to an oscilloscope; the high-speed photographing system comprises a film light measurement of the expansion process in the test section (1) and photographing of the connecting section (9) in the vacuum section (11), wherein the high-speed camera (17) photographs a flow field at the film breaking moment and directly transmits a photographed picture to a storage medium.

2. The device for simulating a hypersonic coagulation process in a nozzle of claim 1, wherein: the simulated nozzle device can ensure the uniformity of a flow field of a test section.

3. The device for simulating a hypersonic coagulation process in a nozzle of claim 1, wherein: the simulated nozzle device is capable of achieving a hypersonic condensation process of matter on a small time scale (<1 ms).

4. The device for simulating a hypersonic coagulation process in a nozzle of claim 1, wherein: the measurement system can ensure the measurement diversity and the time resolution of 100kHz and above.

5. The device for simulating a hypersonic coagulation process in a nozzle of claim 1, wherein: the test section (1) is of a rectangular inner cavity (2) structure and is completely symmetrical; the propagation speed of the rarefaction wave can be changed by adjusting the length of the test section (1).

6. The device for simulating a hypersonic coagulation process in a nozzle of claim 4, wherein: the TDLAS measurement system adopts a measurement channel, and multiple laser signals are coupled into one path of signal to achieve the function of simultaneously measuring multiple component information; and by using a baseline fitting method, a laser output signal is divided into two paths of signals through an optical fiber coupler, one path of signal passes through a flow field to be measured to obtain flow field information to be measured, the other path of original signal is directly received by a laser detector, the original signal corresponds to a transmission signal through signal processing, at the moment, the original signal can be used as a baseline of the transmission signal to be processed in the next step, and the measured time resolution can reach 100kHz or above.

7. A method of diagnosing a hypersonic coagulation process in a simulated nozzle, using the apparatus of any of claims 1 to 6, comprising the steps of:

firstly, pumping the vacuum section (11) to a vacuum state through a self-carrying pumping pump (18), then utilizing a vacuum pump to connect a pressure control valve (7) to adjust the initial pressure of the test section (1), and simultaneously filling the prepared experimental gas into the test section (1) through the pressure control valve (7); when the requirement of design experiment parameters is met, the electric blasting wire system can be charged, when the voltage reaches 1000V, the electric blasting wire system discharges instantly, the temperature of the nichrome wire rises rapidly at the moment, the PET film breaks instantly, the test section (1) and the vacuum section (11) begin to expand at a high speed under the action of pressure difference, along with the propagation of sparse waves, the material begins a hypersonic condensation process, at the moment, the measurement system takes a pressure drop signal as a trigger signal to acquire a pressure signal, a laser transmission signal and a high-speed photographic picture in the film breaking process, and then the water vapor condensation characteristic is analyzed through data processing.

Technical Field

The invention relates to the field of hypersonic condensation of substances, in particular to a device for simulating a hypersonic condensation process in a spray pipe and a diagnosis method.

Background

In the combustion heating type wind tunnel, no matter hydrogen fuel or hydrocarbon fuel is adopted, water vapor exists in products, and before product gas enters a wind tunnel test section through a device spray pipe, the water vapor in combustion products can be rapidly condensed due to rapid expansion of the gas along an expansion section of the spray pipe and temperature reduction. Meanwhile, when the air flow passes through the compression surface of the tested engine, the temperature and the pressure are suddenly increased due to shock wave compression, and phase change phenomena such as re-evaporation of condensed water drops can be caused. From the existing literature, the condensed phase change of water vapor in the wind tunnel may affect the parameters of the nozzle outlet, the flow field quality and the measurement accuracy in many ways. Therefore, in the hypersonic wind tunnel heated by combustion, the water vapor component can generate a strong unsteady phase change process in the ground simulation test process, so that the test flow field is changed, the ground simulation test result is influenced, and the performance evaluation, the pneumatic design and the like of the high-speed aircraft are influenced.

At present, in experimental research on coagulation at home and abroad, most of the experimental researches are carried out by combining related measurement methods with mobile spray pipe equipment at different positions along the flow direction of a spray pipe, and then measurement results at different positions are finally combined to be used as a description of the coagulation phenomenon. However, in this way, the repeatability requirement of the flow field is high between different sets of measurement experiments, and higher requirements are put forward on experimental equipment. Secondly, aiming at the quantitative test of the non-equilibrium condensation of the water vapor in the spray pipe, comprehensive information such as total pressure, a flow field structure and the like is focused on in many test researches which are carried out at present, and the quantitative measurement is focused on the size of the condensed liquid drops. For the phase-change flow field, quantitative real-time measurement of gas temperature and component concentration is an important means for researching the phase-change phenomenon. The near-infrared tunable semiconductor laser absorption spectrum (TDLAS) technology is used as a non-contact measurement method, and the gas temperature and the component concentration in the condensation process can be quantitatively measured by virtue of the characteristics of high sensitivity, quick response, non-contact and the like. However, the current method of using multiple lasers to measure in parallel when using TDLAS technique to measure the key parameters of the flow field requires the use of multiple measuring channels, and the measuring results cannot be synchronized effectively, so the processing procedure is very complicated. However, the current baseline fitting method adopted in TDLAS signal processing requires that a longer baseline is arranged at both ends of an absorption signal, but because the output wavelength of a laser is limited, the broadening of an absorption spectrum line is close to the output wavelength of the laser under the conditions of high temperature and high pressure, the current baseline fitting method cannot obtain an effective baseline, and at the moment, the output wavelength of the laser can only be increased by reducing the scanning frequency, which limits the time resolution of measurement to be generally below 10 kHz.

In view of this, it is necessary to design a device and a diagnostic method capable of simulating a hypersonic coagulation process in a nozzle, which can realize the hypersonic coagulation process on a small time scale (<1ms), ensure the uniformity of a flow field, and simultaneously realize the continuity of measurement and high time resolution of measurement (not less than 100 kHz).

Disclosure of Invention

The invention aims to provide a device and a diagnosis method for simulating a high supersonic velocity condensation process in a spray pipe, which can realize the following functions and indexes:

(1) the uniformity of the flow field of the test section can be ensured.

(2) A hypersonic condensation process of matter can be achieved on a small timescale (<1 ms).

(3) The measurement diversity can be ensured and the time resolution is 100kHz and above.

The invention adopts the following technical scheme:

a device for simulating a high supersonic velocity condensation process in a spray pipe comprises a simulated spray pipe device and a measuring system.

The simulated nozzle device comprises a test section, a connecting section and a vacuum section, wherein the test section is connected with the connecting section, and the connecting section is fixed at the opening of the vacuum section. The test section is of a rectangular inner cavity structure and is completely symmetrical; the propagation speed of the rarefaction wave can be changed by adjusting the length of the test segment.

The test section comprises a rectangular inner cavity, an optical fiber fixing device, a pressure control valve, an observation window and 3 pressure measuring points. The rectangular inner cavity is of a completely symmetrical structure, based on the principle of sparse waves, a sparse wave can be generated at a rectangular outlet when the spray pipe expands at a high speed and then uniformly spread into the rectangular flow field, and when the sparse wave reaches the bottom of a test section, the sparse wave is spread back at the same speed due to the reflection effect of the wall surface, so that the pressure drop speed at the position of a test point is further increased, the supercooling degree is further increased, and the condensation of substances is caused. The process simulates the hypersonic condensation process of substances in the spray pipe to a certain extent, as shown in fig. 1, the process of axial change of the test section along time corresponds to the axial change of the spray pipe along the position, and the continuity of measurement is realized. Meanwhile, the expansion time scale can reach within 1ms due to the design of the rectangular inner cavity of the test section, and the propagation speed of rarefaction waves can be changed by adjusting the length of the test section, so that the expansion time is further shortened, and the theoretical requirement is met. And the uniformity of the flow field of the test section is ensured by the unification of the cross section of the test section and the structure of the inner cavity, as shown in fig. 2, sparse waves generated by the test section in the expansion process are stably propagated into the flow field all the time, so that the uniformity of the rectangular inner cavity along the measuring direction is achieved. The optical fiber fixing device is externally connected to the tail part of the rectangular inner cavity, and the optical fiber collimator is fixed through the gasket and the gasket to keep the axial height consistent, so that laser signals can completely pass through the flow field and be received. The pressure control valve is externally connected to the middle part of the rectangular inner cavity and consists of two control valves, and the control of the pressure and the content of different components in a flow field can be realized by connecting the vacuum pump and the gas cylinder. The observation window is externally connected above the rectangular inner cavity and comprises a glass window sheet and a gasket, the change process in the flow field can be visually observed, and the dynamic detection of the condensation process of water vapor can be realized by combining a high-speed photography technology. The pressure measuring points are fixed at the bottom of the rectangular inner cavity, and three pressure measuring points along the same axial direction are distributed at the left position, the middle position and the right position, so that the uniformity of the flow field can be detected. Meanwhile, the optical fiber fixing device, the pressure control device and the observation window are externally connected so that the structure of the rectangular inner cavity is not interfered, and the uniformity of a flow field is ensured.

The connecting section comprises a rectangular frame, a pure copper conductor, a gasket, a polyester film (PET) and an electric blasting fuse system. The rectangular frame is internally provided with a groove, a rubber gasket can be filled, and when a PET membrane with a certain thickness is selected to be placed on the rubber gasket, the PET membrane is compressed by screws to achieve the effect of isolating the pressure of the test section and the vacuum section. The electric wire explosion system comprises a 1000V capacitor power supply and a 0.2mm nichrome wire, wherein the nichrome wire is tightly attached to the PET membrane. During the test, the power supply is charged firstly, when the voltage reaches 1000V, the discharge is carried out instantly, the temperature of the nichrome wire is rapidly increased, the PET film is broken instantly, and the test section and the vacuum section start a high-speed expansion process under the action of the pressure difference.

The vacuum section comprises a cavity, an upper observation port, a rear observation port, a pumping pump and a pressure display. The observation ports are glass window sheets, and the high-speed photography technology can be combined to observe the film breaking process at the outlet of the test section in the high-speed expansion process.

The measurement system includes a TDLAS measurement system, a pressure measurement system and a high speed photography system.

The TDLAS measuring system comprises a signal generator, a laser controller, a laser detector, a collimator, an optical fiber coupler, an etalon, a single-mode optical fiber, a multi-mode optical fiber and an oscilloscope, wherein the signal generator outputs a voltage signal to the laser controller, the laser controller generates a corresponding temperature and current to control the laser to output a laser signal, the laser signal is overlapped into a beam of laser signal through the optical fiber coupler to be transmitted in the single-mode optical fiber, the collimator is installed at an outlet of the single-mode optical fiber and connected to an optical fiber fixing device in a test section to ensure linear transmission in a flow field, the multi-mode optical fiber with a larger aperture than that of the single-mode optical fiber is installed at the other end of the optical fiber fixing device in the test section to receive the laser signal flowing through the flow field to be measured, and then the laser detector is used for converting the laser signal into an electric signal to be transmitted to the oscilloscope. The TDLAS measurement system adopts a measurement channel, and multiple laser signals are coupled into one path of signal to achieve the function of simultaneously measuring multiple component information; and by using a baseline fitting method, a laser output signal is divided into two paths of signals through an optical fiber coupler, one path of signal passes through a flow field to be measured to obtain flow field information to be measured, the other path of original signal is directly received by a laser detector, the original signal corresponds to a transmission signal through signal processing, at the moment, the original signal can be used as a baseline of the transmission signal to be processed in the next step, and the measured time resolution can reach 100kHz or above. Specifically, in order to be able to measure multi-component information simultaneously, a novel coupling method is proposed: the signal generator outputs three sawtooth wave signals with frequency of 100kHz, duty ratio of 1/3 and phase difference of 60 degrees, the laser controller enables the laser to output laser signals with the same characteristics, and the signals are coupled into one path through the optical fiber coupler so as to achieve the function of simultaneously measuring information of various components. The method only needs one measuring channel, can synchronize the results of all laser signals, and is simple in processing process. Meanwhile, the high scanning frequency makes the output wavelength of the laser shorter, which is not enough to obtain the scanning signal required by the traditional wavelength scanning method for base line fitting. Therefore, a baseline fitting method is proposed: the output signal of the laser is divided into two paths of signals by the optical fiber beam splitter, one path of signals passes through the flow field to be measured to acquire the information of the flow field to be measured, the other path of original signals is directly received by the laser detector, the original signals correspond to the transmission signals through signal processing, and at the moment, the original signals can be used as the base line of the transmission signals to be processed in the next step.

The pressure measurement system comprises three pressure sensors and a pressure transmitter, wherein the three pressure sensors are axially distributed on pressure measurement points in the left direction, the middle direction and the right direction of the bottom of the test section, and pressure signals obtained by measurement are converted into electric signals by the pressure transmitter and transmitted to the oscilloscope. The measuring points of the multiple pressure sensors can measure the time of sparse waves reaching different positions at the bottom of the test section in the expansion process, and the uniformity of the flow field of the test section is verified through the uniformity of the three sensors.

The high-speed photographing system comprises the steps of measuring the sheet light in the expansion process in the test section and photographing the connecting section in the vacuum section, wherein the high-speed camera photographs the flow field at the membrane breaking moment and directly transmits the photographed picture to the storage medium. The membrane rupture process at the outlet of the test section in the high-speed expansion process can be observed.

A diagnostic method for simulating a hypersonic coagulation process in a spray pipe, which adopts the device as any one of the above, comprises the following steps:

firstly, pumping the vacuum section to a vacuum state through a self-contained vacuum pump in the vacuum section, then utilizing the vacuum pump to be connected with a pressure control valve to adjust the initial pressure of the test section, and simultaneously filling a certain amount of configured experimental gas into the test section through the pressure control valve; when the requirement of design experiment parameters is met, the electric blasting wire system can be charged, when the voltage reaches 1000V, the electric blasting wire system discharges instantly, the temperature of the nichrome wire rises rapidly at the moment, the PET film breaks instantly, the test section and the vacuum section begin to expand at a high speed under the action of pressure difference, along with the propagation of sparse waves, substances begin to undergo a hypersonic condensation process, the measurement system takes a pressure drop signal as a trigger signal to acquire a pressure signal, a laser transmission signal and a high-speed photographic picture in the film breaking process, and then the water vapor condensation characteristic is analyzed through data processing.

The advantages and positive effects are as follows:

the invention provides a device for simulating a high supersonic velocity condensation process in a spray pipe and a diagnosis method.

(1) The uniformity of the flow field of the test section is ensured. A rectangular inner cavity is designed, based on the principle of sparse waves, sparse waves can be generated at a rectangular outlet when a spray pipe expands at a high speed and then are uniformly transmitted into a rectangular flow field, when the sparse waves reach the bottom of a test section, the sparse waves are transmitted back at the same speed due to the reflection action of a wall surface, and then are reflected again at the contact surface of a high-pressure section and a low-pressure section, so that the pressure drop speed of a measuring point position is further reduced, the supercooling degree is increased, and the condensation of substances is caused. Meanwhile, the uniformity of the flow field of the test section is also ensured by the unification of the cross section and the inner cavity structure of the test section.

(2) A hypersonic condensation process of matter is achieved on a small time scale (<1 ms). Because the propagation speed of the sparse wave is related to the length of the test segment in the expansion process, and the pressure relief speed is also ensured by the unification of the cross section of the test segment and the structure of the inner cavity, the expansion time scale can reach within 1ms by the design of the rectangular inner cavity of the test segment, and the time for the sparse wave to reach the measurement position can also be changed by adjusting the length of the test segment, so that the expansion time is further shortened, and the theoretical requirement is met.

(3) Ensuring the measurement diversity and the time resolution of 100kHz and above. In order to avoid the problem of complex multi-measurement channel and data processing caused by parallel measurement of multiple lasers in multi-component measurement, a novel coupling mode is provided: the signal generator outputs three sawtooth wave signals with frequency of 100kHz, duty ratio of 1/3 and phase difference of 60 degrees, the laser controller enables the laser to output laser signals with the same characteristics, and the signals are coupled into one path through the optical fiber coupler so as to achieve the function of simultaneously measuring information of various components. Meanwhile, the high scanning frequency makes the output wavelength of the laser shorter, which is not enough to obtain the scanning signal required by the traditional wavelength scanning method for base line fitting. Therefore, a new baseline fitting method is proposed: the output signal of the laser is divided into two paths of signals by the optical fiber beam splitter, one path of signals passes through the flow field to be measured to acquire the information of the flow field to be measured, the other path of original signals is directly received by the laser detector, the original signals correspond to the transmission signals through signal processing, and at the moment, the original signals can be used as the base line of the transmission signals to be processed in the next step.

Drawings

FIG. 1 is a schematic diagram showing the process of axial variation of a test section along time corresponding to the variation of a nozzle along the axial direction of position;

FIG. 2 is a schematic view of the uniformity of the flow field in the test section;

FIG. 3 is a schematic top view of a simulated nozzle assembly according to an embodiment of the present invention;

FIG. 4 is a schematic front view of a simulated nozzle assembly according to an embodiment of the present invention;

FIG. 5 is a schematic flow chart of a measurement system according to an embodiment of the present invention;

FIG. 6 is a diagram of three laser coupling signals provided by an embodiment of the present invention;

fig. 7 is a method for fitting a baseline according to an embodiment of the present invention.

Description of reference numerals: 1. a test section; 2. a rectangular inner cavity; 3. measuring a middle pressure point; 4. measuring a right pressure point; 5. a left pressure measurement point; 6. an optical fiber fixing device; 7. a pressure control valve; 8. an observation window; 9. a connecting section; 10. a pure copper conductor; 11. a vacuum section; 12. an upper observation port; 13. a rear observation port; 14. displaying the pressure; 15. the connecting section and the vacuum section are provided with threaded holes; 16. the test section and the connecting section are provided with threaded holes; 17. a high-speed camera; 18. a pumping pump.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in FIGS. 3 and 4, the device for simulating the hypersonic coagulation process in the spray pipe comprises a simulated spray pipe device and a measuring system. The simulated nozzle device mainly comprises a test section 1, a connecting section 9 and a vacuum section 11, wherein the test section 1 and the connecting section 9 are connected with a screw at a threaded hole 16 of the connecting section through the test section, and the connecting section 9 is fixed at an opening of the vacuum section 11 through a screw at a threaded hole 15 of the connecting section and the vacuum section.

The test section 1 mainly comprises a rectangular inner cavity 2, a middle pressure measuring point 3, a right side pressure measuring point 4, a left side pressure measuring point 5, an optical fiber fixing device 6, a pressure control valve 7 and an observation window 8. The rectangular inner cavity 2 is of a completely symmetrical structure, based on the principle of sparse waves, a sparse wave can be generated at a rectangular outlet when the spray pipe expands at a high speed and then uniformly spread into the rectangular flow field, when the sparse wave reaches the bottom of the test section 1, due to the reflection effect of the wall surface, the sparse wave is spread back at the same speed, so that the pressure drop speed at the position of a test point is further increased, the supercooling degree is increased, and the condensation of substances is caused. The process simulates the hypersonic condensation process of substances in the spray pipe to a certain extent, as shown in fig. 1, the process of axial change of the test section 1 along time corresponds to the axial change of the spray pipe along the position, and the continuity of measurement is realized. Meanwhile, the design of the rectangular inner cavity 2 of the test section enables the expansion time scale to reach within 1ms, and the propagation speed of rarefaction waves can be changed by adjusting the length of the test section, so that the expansion time is further shortened, and the theoretical requirement is met. And the uniformity of the flow field of the test section is ensured by the unification of the cross section of the test section and the structure of the inner cavity, as shown in fig. 2, sparse waves generated by the test section 1 in the expansion process are stably propagated into the flow field all the time, so that the uniformity of the rectangular inner cavity 2 along the measuring direction is achieved. The optical fiber fixing device 6 is externally connected to the tail part of the rectangular inner cavity 2, and the optical fiber collimator is fixed through a gasket and a gasket to keep the axial height consistent, so that laser signals can completely pass through a flow field and be received. The pressure control valve 7 is connected to the middle part of the rectangular inner cavity 2 and consists of two control valves, and the control of the pressure and the content of different components in a flow field can be realized through an external vacuum pump and an external gas cylinder. The observation window 8 is externally connected above the rectangular inner cavity 2 and comprises a glass window sheet and a gasket, so that the change process in the flow field can be visually observed, and the dynamic detection of the water vapor condensation process can be realized by combining a high-speed photography technology. The pressure measuring points 3, 4 and 5 are fixed at the bottom of the rectangular inner cavity 2, and three pressure measuring points along the same axial direction are distributed at the left position, the middle position and the right position, so that the uniformity of the flow field can be detected. The external design of the optical fiber fixing device 6, the pressure control device 7 and the observation window 8 ensures that the structure of the rectangular inner cavity 2 is not interfered, and the uniformity of a flow field is ensured.

The connecting section 9 mainly comprises a rectangular frame, a pure copper conductor 10, a gasket, a polyester film and an electric wire explosion system. The rectangular frame is internally provided with a groove, a rubber gasket can be filled, and when a PET (polyethylene terephthalate) membrane with a certain thickness is selected to be placed on the rubber gasket, the PET membrane is compressed by screws to achieve the effect of isolating the pressure of the test section 1 and the vacuum section 11. The electric wire explosion system comprises a 1000V capacitor power supply and a 0.2mm nichrome wire, wherein the nichrome wire is tightly attached to the PET membrane. During the test, the power supply is charged firstly, when the voltage reaches 1000V, the power supply discharges instantly, the temperature of the nichrome wire rises rapidly at the moment, the PET film breaks instantly, and the test section 1 and the vacuum section 11 start a high-speed expansion process under the action of the pressure difference.

The vacuum section 11 mainly comprises a cavity, an upper observation port 12, a rear observation port 13, a pumping pump 18 and a pressure display 14. The observation ports are glass window sheets, and the high-speed photography technology can be combined to observe the film breaking process at the outlet of the test section in the high-speed expansion process.

The hypersonic condensation process of the substance is mainly realized by the pressure difference between the test section 1 and the vacuum section 11, and the operation process is as follows: firstly, a polyester film is installed on a connecting section 9 and is tightly pressed at a test section 1 by a gasket and a rectangular frame, so that the test section 1 and a vacuum section 11 have corresponding pressure difference, then a nichrome wire is installed on a pure copper conductor 10 of the test section 1 and is tightly attached to the polyester film, the film can be completely broken when a metal wire is electrified, then the test section 1 and the connecting section 9 are connected with a screw at a threaded hole 16 of the connecting section through the test section, the connecting section 9 is fixed at an opening of the vacuum section 11 through a screw at a threaded hole 15 of the connecting section and the vacuum section, and finally an electric wire explosion system is connected.

As shown in fig. 5, the present invention relates to a measurement system process, which includes a TDLAS measurement system, a pressure measurement system, and a high-speed camera system.

The TDLAS measuring system comprises a signal generator, a laser controller, a laser detector, a collimator, an optical fiber coupler, an etalon, a single-mode optical fiber, a multi-mode optical fiber and an oscilloscope, wherein the signal generator outputs a voltage signal to the laser controller, the laser controller generates a corresponding temperature and current to control the laser to output a laser signal, the laser signal is overlapped into a beam of laser signal to be transmitted in the single-mode optical fiber through the optical fiber coupler, the collimator is installed at an outlet of the single-mode optical fiber and connected to an optical fiber fixing device 6 in a test section 1 to ensure linear transmission in a flow field, the multi-mode optical fiber with a larger aperture than that of the single-mode optical fiber is installed at the other end of the optical fiber fixing device 6 in the test section 1 to receive the laser signal flowing through the flow field to be measured, and then the laser detector converts the laser signal into an electric signal to be transmitted to the oscilloscope.

The pressure measurement system comprises three pressure sensors with the measuring range of 100kPa and pressure transmitters, wherein the three pressure sensors are axially distributed on pressure measuring points 3, 4 and 5 in the left direction, the middle direction and the right direction at the bottom of the test section 1, and pressure signals obtained by measurement are converted into electric signals by the pressure transmitters and transmitted to an oscilloscope. The measuring points of the multiple pressure sensors can measure the time of sparse waves reaching different positions at the bottom of the test section 1 in the expansion process, and the uniformity of a flow field of the test section is verified through the uniformity of the three sensors.

The high-speed photographic system comprises a film light measurement on the expansion process in the test section 1, and can visually observe the dynamic process of water vapor condensation in the flow field; the vacuum section 11 shoots the connecting section 9 at a high speed, and the shot picture is directly transmitted to a storage medium, so that the membrane rupture process at the outlet of the test section 1 in the high-speed expansion process can be observed.

The operation process is as follows: firstly, a signal generator outputs three sawtooth wave voltage signals with frequency of 100kHz, duty ratio of 1/3 and phase difference of 60 degrees to a first laser controller, a second laser controller and a third laser controller respectively, the three laser controllers generate corresponding temperature and current to the three lasers, the lasers output laser signals with the same characteristics, and the three laser controllers are coupled with one signal through an optical fiber coupler to achieve the function of simultaneously measuring multiple component information, and as shown in fig. 6, three laser signals with central wavelengths of 1653nm, 1409nm and 1395nm are output in an experiment and coupled in one period. Then, one path of optical fiber is arranged on an optical fiber fixing device 6 through a collimator, and a laser signal is received by a first laser detector after passing through a flow field of the test section 1; the other path of optical fiber is directly received by the second laser detector through the collimator without passing through the flow field to be measured, and is used as a reference signal to realize baseline fitting under high scanning frequency, as shown in fig. 7, the dotted line in the figure is a laser signal I0 without passing through the flow field to be measured, and the solid line is a laser signal passing through the flow fieldLaser signal I, which is obtained by Beer-Lambert absorption law I ═ I₀exp (-PXLS (T) phi (v)), wherein P is the pressure of the flow field, X is the water vapor content, L is the optical path of the laser passing through the flow field, S (T) is the linear intensity of the absorption line at the temperature T, and phi (v) is an absorption linear function, so that the corresponding absorption rate can be obtained, and further the information of the corresponding component can be calculated. Secondly, three pressure sensors are respectively arranged on a middle pressure side point 3, a right pressure measuring point 4 and a left pressure measuring point 5, pressure signals are converted into electric signals through pressure transmitters and transmitted to an oscilloscope for collection, the time of arrival of sparse waves during membrane rupture can be measured through the design of the same level at different positions, and then the uniformity of a flow field is judged. Meanwhile, the high-speed camera 17 is arranged at the observation window 8 of the test section 1 and the observation window 13 of the vacuum section, and can observe the aggregation phenomenon in the condensation process of water vapor and the process of simulating the high-speed expansion of the spray pipe.

After the equipment is installed, the equipment is pumped to a vacuum state through a self-carrying pumping pump 18 in a vacuum section 11, then the vacuum pump is connected with a pressure control valve 7 to adjust the initial pressure of a test section 1, and simultaneously, a certain amount of configured experimental gas is filled into the test section 1 through the pressure control valve 7; when the requirement of design experiment parameters is met, the electric blasting wire system can be charged, when the voltage reaches 1000V, the electric blasting wire system discharges instantly, the temperature of the nichrome wire rises rapidly at the moment, the PET film breaks instantly, the test section 1 and the vacuum section 11 begin to expand at a high speed under the action of pressure difference, along with the propagation of sparse waves, the material begins a hypersonic condensation process, the measurement system takes a pressure drop signal as a trigger signal to acquire a pressure signal, a laser transmission signal and a high-speed photographic picture in the film breaking process, and then the water vapor condensation characteristic is analyzed through data processing.

The invention has not been described in detail and is part of the common general knowledge of a person skilled in the art. The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and the preferred embodiments are not exhaustive and do not limit the invention to the precise embodiments described. Various modifications and improvements of the technical solution of the present invention may be made by those skilled in the art without departing from the spirit of the present invention, and the technical solution of the present invention is to be covered by the protection scope defined by the claims.