Optical test system and test method for measuring total temperature of supersonic combustion flow field

Abstract

The invention discloses an optical test system and method for measuring the total temperature of a supersonic combustion flow field, and relates to the field of combustion flow field measurement. The system comprises supersonic combustion incoming flow, a time sequence synchronizer, a first laser, a first focusing lens, a first total reflection plane mirror, a second laser, a second focusing lens, a sheet light lens, a second total reflection plane mirror, a computer, an ICCD, a tunable laser diode, a laser controller, a photoelectric detector, an industrial personal computer and a signal monitor. On the basis of a non-contact optical testing technology, the local total temperature is obtained by measuring the speed and the static temperature of the combustion flow field at the same time on the premise that the flow structure and the combustion state of the combustion flow field are not damaged, the structure of the supersonic combustion flow field is not obviously affected, unnecessary oblique shock waves are not caused, and the measurement accuracy is high. And the local and downstream flow and combustion states of the tested combustion flow field are not influenced.

Description

Technical Field

[0001] The present invention relates to the field of combustion flow field measurement, and in particular to an optical test system and a test method for measuring the total temperature of a supersonic combustion flow field. Background Art

[0002] In the field of supersonic combustion, total temperature can be used to reflect the important parameter of combustion efficiency. For engines, it can further reflect the performance of the combustion chamber. Therefore, total temperature is a key experimental parameter in the basic science and engineering application fields of combustion. Nowadays, the method of measuring total temperature is mainly the contact measurement technology of the total temperature probe. For example, the next-generation wind tunnel test equipment (NG-Turb) reported by the German Aerospace Agency (DLR) in 2023 uses three parameters: mass flow, total temperature and total pressure to reflect all boundary conditions of the equipment. The total temperature measurement method mentioned is still an immersed pneumatic probe (pneumatic probe). For detailed information, see the literature Andreas Pahs, Anna-Samira Franz-Xaver Torsten Wolf, Turbine operation and measurement at DLRs next generation turbine test facility[C], Proceedings of ASME Turbo Expo2023, GT2023-102118. The contact method of the aerodynamic probe has a significant impact on the supersonic flow field structure, causing unnecessary oblique shock waves, which in turn affect the flow and combustion conditions at the probe location and downstream. Summary of the invention

[0003] The present invention is based on non-contact optical testing technology. Without destroying the flow structure and combustion state of the combustion flow field, the local total temperature is obtained by simultaneously measuring the velocity and static temperature of the combustion flow field, providing a new idea for measuring the total temperature of the supersonic combustion flow field, and further providing a new test device and method for quantifying combustion efficiency and evaluating engine combustion chamber performance.

[0004] To achieve the above-mentioned object of the invention, the present invention provides an optical test system for measuring the total temperature of a supersonic combustion flow field, the system comprising:

[0005] Supersonic combustion flow, timing synchronizer, first laser, first focusing lens, first total reflection plane mirror, second laser, second focusing lens, sheet light lens, second total reflection plane mirror, computer, ICCD, tunable laser diode, laser controller, photoelectric detector, industrial computer and signal monitor;

[0006] The supersonic combustion flow flows to a preset area to form a combustion flow field to be measured, which is used to provide a test measurement object; the timing synchronizer is used to control the timing relationship between the various components in the system; the first laser is used to generate a first pulse laser, which is focused by a first focusing lens and then emitted to a first total reflection plane mirror, and the laser reflected by the first total reflection plane mirror is emitted into the combustion flow field to be measured; the second laser is used to generate a second pulse laser, which is focused by a second focusing lens and then emitted to a sheet light lens, and the sheet light lens processes the focused laser into a sheet light, which is reflected by the second total reflection plane mirror and then emitted into the combustion flow field to be measured; the tunable laser diode is used to generate a laser that scans at a fixed frequency within a preset range; the laser controller is used to control the output wavelength and frequency of the tunable laser diode; the photodetector is used to receive the signal of the laser emitted by the tunable laser diode after passing through the combustion flow field to be measured; the industrial computer is used to control the laser controller, as well as to collect and store the signal information transmitted by the photodetector, and to process the near-infrared band absorption spectrum test data in the signal information; the signal monitor is used to monitor the near-infrared band absorption spectrum test data.

[0007] The principle of the present invention is as follows: water molecules in a combustion flow field can be marked by laser, and after marking, the flow velocity of the combustion flow field is calculated by recording the displacement of the marked molecules within a known time; water molecules can absorb energy of a laser in a certain infrared band, and the static temperature of the combustion flow field in the absorption area can be calculated through the absorption intensity of the absorbed infrared light; after obtaining the static temperature and flow velocity of the combustion flow field, the Mach number and total temperature of the combustion flow field, two key parameters of the supersonic combustion flow field, can be obtained based on the relationship between the static temperature, flow velocity, sound speed, Mach number and total temperature of the combustion flow field.

[0008] Wherein, in the embodiment of the present invention, the system further comprises: an oscilloscope, and the oscilloscope is used to check the timing relationship between the first laser, the second laser, the ICCD and the tunable laser diode.

[0009] Among them, in the embodiment of the present invention, the timing synchronizer is used to control the timing relationship between the components in the system, specifically: the timing synchronizer is used to control the first laser and the tunable laser diode to be turned on at the same time t0 and turned off at the same time t1, and to control the second laser and the ICCD to be turned on at the same time t2 and turned off at the same time t3. The order along the time axis is t0, t1, t2 and t3 respectively.

[0010] In the embodiment of the present invention, the first laser is used to generate a pulse laser with a wavelength of 193 nm, and the pulse laser is used to detect H 2 O splits into OH and H.

[0011] In this embodiment of the present invention, the second laser is used to generate a pulsed laser with a wavelength of 282 nm, which is used to excite the OH groups in the measured combustion flow field to a preset state, and the ICCD is used to record the fluorescence radiation generated by the OH groups during the regression process from the preset state to the initial state.

[0012] In the embodiment of the present invention, the computer is used to determine the position of the marked OH group based on the recording result of the ICCD.

[0013] The present invention also provides a test method based on the optical test system for measuring the total temperature of a supersonic combustion flow field, the test method comprising:

[0014] Step 1: Build an optical test system;

[0015] Step 2: Connect the components in the optical test system;

[0016] Step 3: Turn on the equipment in the optical test system;

[0017] Step 4: Adjust the position and direction of each device in the optical test system;

[0018] Step 5: Start the combustion flow field;

[0019] Step 6: Start the optical test system and control the equipment in the optical test system accordingly according to the preset timing relationship;

[0020] Step 7: After a period of time, turn off the optical test system and the combustion flow field in turn;

[0021] Step 8: Result processing: obtaining the total temperature of the combustion flow field based on the combustion flow field velocity and the combustion flow field static temperature.

[0022] One or more technical solutions provided by the present invention have at least the following technical effects or advantages:

[0023] The present invention can obtain the local total temperature by simultaneously measuring the velocity and static temperature of the combustion flow field based on non-contact optical testing technology without destroying the flow structure and combustion state of the combustion flow field. It will not cause a significant impact on the supersonic combustion flow field structure, nor will it cause unnecessary oblique shock waves, and will not affect the local and downstream flow and combustion states of the combustion flow field being tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of the present invention, and do not constitute a limitation on the embodiments of the present invention;

[0025] Figure 1 It is a schematic diagram of the principle of the optical test system for measuring the total temperature of the supersonic combustion flow field in the present invention;

[0026] Figure 2 It is a schematic diagram of the timing relationship of various components within a pulse time in the present invention;

[0027] Figure 3 This is a schematic diagram of the measurement location of the test site;

[0028] Figure 4 Schematic diagram of the test results of measuring position speed;

[0029] Figure 5 This is a schematic diagram of the test results of the temperature change at the measurement position over time;

[0030] Among them, 1-supersonic combustion flow, 2-timing synchronizer, 3-first laser, 4-first focusing lens, 5-first total reflection plane mirror, 6-second laser, 7-second focusing lens, 8-sheet light lens, 9-second total reflection plane mirror, 10-oscilloscope, 11-computer; 12-ICCD, 13-tunable laser diode, 14-laser controller, 15-photodetector, 16-industrial computer, 17-signal monitor. DETAILED DESCRIPTION

[0031] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those within the scope of this description. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0033] Embodiment 1;

[0034] Please refer to Figure 1 The principle of the total temperature measurement test device and method proposed by the present invention is as follows Figure 1As shown, α represents the angle between the 193nm laser and the infrared laser when they pass through the combustion flow field to be measured; λ represents the specific length of the 193nm laser that can be used to mark the water molecules for velocity measurement after being focused in the measured area. The total temperature finally obtained is the average total temperature in the rectangular area along the flow direction. The entire system includes several components and necessary accessories such as optical fiber connectors. The names and main functions of each component are as follows: supersonic combustion flow 1, providing the test measurement object; timing synchronizer 2, controlling the timing relationship between each component; the first laser 3, used to generate a pulsed laser with a wavelength of 193nm, which is used to split H2O in the combustion flow field into OH and H. This process can be regarded as marking OH at a specific position with a laser of 193nm wavelength; the first focusing lens 4, which focuses the laser emitted by the 193nm laser to increase the laser energy per unit space, The decomposition rate of H2O is improved; the first total reflection plane mirror 5 changes the transmission direction of the 193nm laser so that the laser enters the measured combustion flow field at a suitable position and direction; the second laser 6 is used to generate a pulsed laser with a wavelength of 282nm, which is used to excite the OH groups in the combustion flow field to a high energy state. The high energy state OH groups are unstable and will return to a low energy state. The regression process is accompanied by fluorescence radiation, which can be recorded by ICCD to determine the position of the marked OH groups; the second focusing lens 7 focuses the laser emitted by the 282nm laser so that the excitation within the unit space The light energy is increased, and the excitation rate of OH is increased; the sheet light lens 8 stretches the focused 282nm wavelength laser in one direction, so that the laser is shaped into a thin sheet laser; the second total reflection plane mirror 9 reflects the thin sheet laser into the position to be tested; the oscilloscope 10 is used to check the timing relationship between components 3, 6, 12 and 13; the computer 11; the ICCD 12; the tunable laser diode 13 is used to generate a laser that can be scanned at a fixed frequency within a certain range. The range and frequency are controlled by the laser controller 14 according to the specific test object. The laser in this band can be absorbed by H2O, This causes the signal collected by the photodetector 15 to change, and the combustion flow field parameters can be inversely calculated through the specific change amount; the laser controller 14 controls the output wavelength and frequency of the tunable laser diode 13; the photodetector 15 receives the signal of the laser emitted by the tunable laser diode 13 after passing through the combustion flow field; the industrial computer 16 controls the laser controller 14, collects and stores the information of the photodetector 15, processes the near-infrared band absorption spectrum test data, and obtains the average static temperature under the line of sight integration; the signal monitor 17 is a visualization medium for the near-infrared band absorption spectrum test control program. Among them, components 3-9, 11 and 12 are used to measure the flow velocity on the small line segment (assuming the length is λ) in the focus area on the line segment that passes through the combustion flow field after component 5. After obtaining the flow velocity on the line segment, its average value is calculated, and components 13-17 are used to measure the static temperature under the line of sight integration on the optical path.The relationship between various physical quantities is then used to calculate the average Mach number and average total temperature in the rectangular area covered by the length λ and angle ɑ in the combustion flow field area.

[0035] Figure 2 is the timing relationship of each component within a pulse time, Figure 2 193nm laser and near infrared laser in t 0 The pulsed laser is emitted at the same time, and then ends at the same time at t1. The near-infrared detector synchronously records the near-infrared laser. The 282nm laser and the camera are turned on at the same time at t2 and turned off at the same time at t3.

[0036] The present invention is Figure 3 Measurement tests were carried out on the test objects shown. Figure 3 In the figure, a is the original image of the object being measured, and b is a schematic diagram of the measured position. The vertical upward arrow represents the area where the 193nm laser acts, the arrow from the lower right to the upper left represents the area where the near-infrared laser acts, and the parallelogram represents the area where the 282nm laser acts. In the center of a space with upper, lower, front and rear limits, there is a jet of gas ejected from left to right. From the brightness distribution of the gas, it can be found that there is a strong discontinuous combustion flow field similar to an oblique shock wave, which can be judged that the gas is a supersonic gas. Due to the combustion chemical reaction, in Figure 3 (b) The middle measured position has H 2 O exists, Figure 3 The 193nm laser from bottom to top will 2 O dissociates into OH and H( Figure 2 The t shown 0 time), Figure 3 From the lower left to the upper right, the 282nm light excites OH to a state that can be recorded by ICCD ( Figure 2 The t shown 1 moment); when the 193nm laser is triggered, Figure 3 (b) The mid-infrared laser absorption H from the lower right to the upper left (the angle with the 193nm laser direction in the experiment is 15°). 2 O signal and is recorded by the photodetector ( Figure 2 The t shown 0 time).

[0037] Figure 4 The t recorded by 193nm laser and 282nm laser are given. 1 -t 0 The velocity of the combustion flow field under test within a certain time, t 0 When 193nm laser is applied to H 2 O produces OH, t 1The 282nm laser records the position of OH at the same time, and the speed can be calculated by the time difference and the displacement at the two times. Figure 3 The velocity distribution in the vertical direction from 14.9mm to 23.3mm is as follows: Figure 4 As shown, the average velocity of the combustion flow field is 1000m / s.

[0038] Figure 5 The mid-infrared laser absorption H 2 The average temperature of the line on the optical path recorded by the O spectrum, Figure 5 The figure shows the variation of the average temperature over time. Due to the relatively large temperature fluctuation over time under supersonic combustion, Figure 5 Only the temperature data within a relatively stable period of time was captured, and the data was time-averaged to obtain an average temperature of 1125K.

[0039] Among them, after obtaining the flow velocity and static temperature of the combustion flow field, the sound velocity is calculated through the relationship between the static temperature of the combustion flow field and the sound velocity, the combustion flow field Mach number is calculated through the relationship between the sound velocity, the flow velocity of the combustion flow field and the Mach number of the combustion flow field, and the total temperature of the combustion flow field is calculated through the relationship between the Mach number of the combustion flow field, the static temperature of the combustion flow field and the total temperature of the combustion flow field.

[0040] According to the calculation formula of the sonic velocity of the combustion flow field, the calculation formula of the Mach number, and the relationship between the total temperature and the static temperature, the total temperature calculation process of the measured area is as follows:

[0041]

[0042] T * =T·(1+0.165·Ma 2 )=1125·(1+0.165·1.52 2 )=1554K(3)

[0043] In formula (1), c is the speed of sound, T is the static temperature, in formula (2), Ma is the Mach number, V is the speed, and in formula (3), T * The total temperature is calculated to be about 1554K in the supersonic combustion area with a height of 8.5mm and a width of 2.3mm.

[0044] Based on the above embodiments, the present invention also provides a test method for an optical test system for measuring total temperature of a supersonic combustion flow field. The test method includes:

[0045] Step 1: Build an optical test system;

[0046] Step 2: Connect the components in the optical test system;

[0047] Step 3: Turn on the equipment in the optical test system;

[0048] Step 4: Adjust the position and direction of each device in the optical test system;

[0049] Step 5: Start the combustion flow field;

[0050] Step 6: Start the optical test system and control the equipment in the optical test system accordingly according to the preset timing relationship;

[0051] Step 7: After a period of time, turn off the optical test system and the combustion flow field in turn;

[0052] Step 8: Result processing: obtaining the total temperature of the combustion flow field based on the combustion flow field velocity and the combustion flow field static temperature.

[0053] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0054] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An optical test system for measuring the total temperature of a supersonic combustion flow field, characterized in that: The system comprises: Supersonic combustion flow, timing synchronizer, first laser, first focusing lens, first total reflection plane mirror, second laser, second focusing lens, sheet light lens, second total reflection plane mirror, computer, ICCD, tunable laser diode, laser controller, photoelectric detector, industrial computer and signal monitor; Among them, the supersonic combustion flow flows to the preset area to form the combustion flow field to be measured, which is used to provide the test measurement object; the timing synchronizer is used to control the timing relationship between the various components in the system; the first laser is used to generate a first pulse laser, which is focused by the first focusing lens and then emitted to the first total reflection plane mirror, and the laser reflected by the first total reflection plane mirror is emitted into the combustion flow field to be measured; the second laser is used to generate a second pulse laser, which is focused by the second focusing lens and then emitted to the sheet light lens, and the sheet light lens processes the focused laser into a sheet light, which is reflected by the second total reflection plane mirror and then emitted into the combustion flow field to be measured; the ICCD records the displacement of the marked substance within a known time, and the results of the ICCD and the oscilloscope are viewed and recorded by a computer; it can A tunable laser diode is used to generate a near-infrared laser that scans at a fixed frequency within a preset range; a laser controller is used to control the output wavelength and frequency of the tunable laser diode; a photodetector is used to receive the signal after the laser emitted by the tunable laser diode passes through the combustion flow field to be measured; an industrial computer is used to control the laser controller, as well as to collect and store the signal information transmitted by the photodetector, and to process the near-infrared band absorption spectrum test data in the signal information; a signal monitor is used to monitor the near-infrared band absorption spectrum test data; a computer calculates the combustion flow field flow velocity based on the results recorded by the ICCD and the oscilloscope; the industrial computer and the signal monitor are used to obtain the combustion flow field static temperature; the combustion flow field total temperature is obtained based on the combustion flow field flow velocity and the combustion flow field static temperature.

2. The optical test system for measuring total temperature of supersonic combustion flow field according to claim 1, characterized in that: The system further comprises an oscilloscope for checking the timing relationship among the first laser, the second laser, the ICCD and the tunable laser diode.

3. The optical test system for measuring total temperature of a supersonic combustion flow field according to claim 2, characterized in that: The timing synchronizer is used to control the timing relationship between the components in the system, specifically: the timing synchronizer is used to control the first laser and the tunable laser diode to be turned on at time t0 and turned off at time t1 at the same time, and to control the second laser and the ICCD to be turned on at time t2 and turned off at time t3 at the same time.

4. The optical test system for measuring total temperature of a supersonic combustion flow field according to claim 1, characterized in that: The first laser is used to generate a pulse laser with a wavelength of 193 nm, and the pulse laser is used to decompose H2O in the measured combustion flow field into OH and H.

5. The optical test system for measuring total temperature of supersonic combustion flow field according to claim 1, characterized in that: The second laser is used to generate a pulsed laser with a wavelength of 282nm, which is used to excite the OH groups in the measured combustion flow field to a preset state. The ICCD is used to record the fluorescence radiation generated by the OH groups in the process of regression from the preset state to the initial state.

6. The optical test system for measuring total temperature of supersonic combustion flow field according to claim 5, characterized in that: A computer is used to determine the position of the labeled OH groups based on the ICCD recordings.

7. The optical test system for measuring total temperature of a supersonic combustion flow field according to claim 1, characterized in that: The total temperature of the combustion flow field is calculated as follows: the speed of sound is calculated through the relationship between the static temperature of the combustion flow field and the speed of sound; the Mach number of the combustion flow field is calculated through the relationship between the speed of sound, the flow velocity of the combustion flow field and the Mach number; the total temperature of the combustion flow field is calculated through the relationship between the Mach number of the combustion flow field, the static temperature of the combustion flow field and the total temperature of the combustion flow field.

8. A test method of an optical test system for measuring total temperature of a supersonic combustion flow field based on any one of claims 1 to 7, characterized in that: The test method includes: Step 1: Build an optical test system; Step 2: Connect the components in the optical test system; Step 3: Turn on the equipment in the optical test system; Step 4: Adjust the position and direction of each device in the optical test system; Step 5: Start the combustion flow field; Step 6: Start the optical test system and control the equipment in the optical test system accordingly according to the preset timing relationship; Step 7: After a period of time, turn off the optical test system and the combustion flow field in turn; Step 8: Result processing: obtaining the total temperature of the combustion flow field based on the combustion flow field velocity and the combustion flow field static temperature.

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