Engine combustion state testing device and method based on photomultiplier tube array

Abstract

The invention discloses an engine combustion state testing device and method based on a photomultiplier tube array, and the device is characterized in that the device is based on an engine combustion chamber which is provided with a supporting plate and a concave cavity, and comprises the photomultiplier tube array. The photomultiplier tube array is sequentially connected with the multi-channel data acquisition system and the processing terminal through the I-V conversion and signal enhancement module; the testing device further comprises a pressure sensor arranged in an engine combustion chamber and a camera arranged outside a window of the engine combustion chamber. The pressure sensor and the camera are used for collecting pressure signals of the combustion chamber and shooting flame images of the combustion chamber respectively. The problem that in the prior art, the combustion state of an engine with a flame stabilizing structure cannot be accurately recognized and monitored in real time is solved.

Description

Technical field

[0001] The present invention belongs to the technical field of engine combustion state monitoring, and in particular relates to an engine combustion state testing device and method based on a photomultiplier tube array. [Background Technology]

[0002] In the actual use of Rocket-Based Combined Cycle (RBCC) ramjet engines, in order to further expand the operating speed range and airspace of the engine combustion chamber, a composite flame stabilization structure consisting of a support plate and a cavity is generally introduced to meet a wider range of flame stabilization requirements. However, the characteristics of a wide Mach number range and a flight altitude range and complex mission requirements will lead to variable combustion chamber inlet parameters during actual wide-speed maneuvering flight. The engine may experience abnormal conditions such as overflow failure to start, thrust oscillation, or even flameout and shutdown. Since the multi-zone coupled flame stabilization structure such as the support plate shear layer, the support plate recirculation zone, and the cavity recirculation zone will increase the complexity of the turbulent combustion flow field, it is more difficult to identify the combustion mode in the engine in real time and online to control the engine. At present, there is no good solution for this field.

[0003] Existing combustion stability testing methods mainly rely on sensors, infrared camera technology, thermocouples and other equipment, but these methods usually have problems such as slow response speed, large signal noise or inability to provide sufficient spatial resolution. For example, in the most commonly used pressure monitoring method, there is a time lag effect in the process of pressure changes caused by shock wave motion and heat release in the combustion chamber being fed back to the pressure sensor on the wall. [Summary of the invention]

[0004] The purpose of the present invention is to provide an engine combustion state testing device and method based on a photomultiplier tube array, so as to solve the problem that the prior art cannot accurately identify and monitor the combustion state of an engine with a flame stabilization structure in real time.

[0005] The present invention adopts the following technical solution: an engine combustion state test device based on a photomultiplier tube array, characterized in that it is based on an engine combustion chamber provided with a support plate and a cavity, the test device includes a photomultiplier tube array, and the photomultiplier tube array is sequentially connected to a multi-channel data acquisition system and a processing terminal through an IV conversion and signal enhancement module;

[0006] The test device also includes a pressure sensor arranged in the engine combustion chamber and a camera arranged outside the engine combustion chamber window, the pressure sensor and the camera are used to collect the pressure signal of the combustion chamber and take the image of the combustion chamber flame respectively;

[0007] The photomultiplier tube array specifically includes:

[0008] The three sensor array mounting parts are all plate-type structures with multiple mounting holes arranged horizontally and vertically to form an m*n array, where m≥1 and n≥2; they are respectively installed outside the observation windows at the top and on both sides of the combustion chamber;

[0009] m*n photomultiplier tubes, each including m*n collimating lenses, are mounted on each mounting hole; each collimating lens is connected to a photodiode via an optical fiber;

[0010] Among them, each photomultiplier tube is used to observe the flame combustion state in the area from the rear edge of the support plate to the front edge of the cavity in the combustion chamber and obtain a photoelectric signal; the IV conversion and signal enhancement module is used to receive and enhance the photoelectric signal; the processing terminal is used to analyze and process the received photoelectric signal, pressure signal and flame image to establish a mapping relationship between the photoelectric signal and the flame state; the data terminal is also used to realize feedback control of the engine according to the received photoelectric signal.

[0011] Furthermore, in each sensor array mounting member:

[0012] The line connecting the centers of the m mounting holes in the first column is at a distance of l from the rear edge of the support plate, and the line connecting the centers of the m mounting holes in the nth column points to the front edge of the cavity; l represents the front edge position of the fire in the combustion chamber.

[0013] Furthermore, the support plate is a triangular pyramid structure and is located in the sensor array mounting part at the top of the combustion chamber:

[0014] If m is an odd number, the center line of the middle row of mounting holes coincides with the symmetrical center line of the support plate;

[0015] If m is an even number, the rows of mounting holes are symmetrically arranged about the symmetry center line of the support plate.

[0016] Furthermore, the optical fiber adopts a one-input and multiple-output quartz optical fiber, and both the incident end and the output end of the optical fiber are planar optical fiber heads.

[0017] Furthermore, the IV conversion and signal enhancement module is connected to a power supply.

[0018] The second technical solution adopted by the present invention is a method for using an engine combustion state test device based on a photomultiplier tube array. The engine combustion state test device based on a photomultiplier tube array includes the following contents:

[0019] Step 1: Place photomultiplier tube arrays outside the observation windows on both sides and top of the engine combustion chamber;

[0020] Step 2: Data processing of the photoelectric signal obtained by the photomultiplier tube array;

[0021] Step 3: Collect the combustion chamber pressure test signal and capture the flame image of the combustion chamber. Based on the pressure test signal and flame image, match them with the photoelectric signal in time and space to identify the combustion mode of the combustion chamber corresponding to the photoelectric signal.

[0022] Step 4: According to the determined combustion mode, during the actual operation of the engine, the photoelectric signal obtained in real time by the photomultiplier tube array can be used to monitor whether the combustion chamber is in a normal working state of the strong combustion mode.

[0023] Furthermore, in step 3, the specific method for matching the photoelectric signal in time and space is:

[0024] The combustion chamber pressure signal and flame image at the same position in the combustion chamber at the same time are compared with the corresponding photoelectric signal, the corresponding photoelectric signal characteristics are analyzed, and a mapping relationship between the photoelectric signal and the combustion mode of the combustion chamber is established to determine whether the combustion mode of the combustion chamber is a strong combustion mode, a weak combustion mode or an undesirable state.

[0025] The beneficial effects of the present invention are:

[0026] This invention utilizes a sensor array mounting assembly, mounted outside the combustion chamber, with mounting locations for photomultiplier tubes (PMTs) positioned on top. This allows for contactless installation, eliminating interference with the flame flow field and extending its lifespan and stability. The array is simple to install and integrated, allowing for flexible adjustments based on varying engine operating conditions, combined with numerical simulations or practical experience, to ensure the PMT array accurately covers the area of ​​intense flame reaction, enabling more accurate measurements.

[0027] The present invention obtains photoelectric signals through a photomultiplier tube array, collects combustion chamber pressure test signals through a pressure sensor, and captures flame images of the combustion chamber through a camera; analyzes the photoelectric signals, pressure signals, and flame brightness signals to establish a mapping from test data to combustion states, and then can identify changes in the flame self-luminous intensity of the combustion chamber during the combustion process, and match the combustion chamber flame stabilization mode based on this, thereby achieving the purpose of accurately identifying and real-time monitoring the combustion state of an engine with a flame stabilization structure.

[0028] The testing device and method of the present invention offer the advantages of non-contact measurement, simple structure, integration, and rapid response and recognition, enabling real-time, online monitoring of the combustion state of RBCC engines. The test system is simple, compact, and easy to integrate, while also being lightweight. It also features a rapid recognition response, with photoelectric signals able to detect changes in combustion mode 452ms before pressure signals.

Brief Description of the Drawings

[0029] Figure 1Schematic diagram of the system structure of the engine combustion state test device based on the photomultiplier tube array of the present invention;

[0030] Figure 2 Schematic diagram of the installation position of the photomultiplier tube array of the engine combustion state test device based on the photomultiplier tube array of the present invention;

[0031] Figure 3 for Figure 2 Schematic top view of

[0032] Figure 4 Schematic diagram of the installation position of the photomultiplier tube array in the embodiment;

[0033] Figure 5 It is a continuous flame brightness image during the lean burnout process; Figure 5 (a) is the continuous flame brightness image corresponding to the strong combustion mode during the lean flameout process. Figure 5 (b) is the continuous flame brightness image corresponding to the weak combustion mode during the lean flameout process;

[0034] Figure 6 : is a comparison diagram of the photoelectric signal and the pressure signal during the lean flameout process in this embodiment;

[0035] Figure 7 3 is a comparison diagram of the changes in the photoelectric signal and flame brightness during the lean flameout process in this embodiment; wherein: stage I is a strong combustion mode; stage II is a weak combustion mode; stage III is an undesirable state.

[0036] Among them, 1. Model combustion chamber, 2. Sensor array mounting part, 3. Collimating lens; 4. Optical fiber; 5. Photodiode; 6. IV conversion and signal enhancement module; 7. Power supply; 8. Multi-channel data acquisition system; 9. Processing terminal, 10. Mounting hole, 11. Support plate, 12. Concave cavity, 13. Back edge of support plate, 14. Front edge of concave cavity. [Specific implementation method]

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The present invention provides an engine combustion state test device based on a photomultiplier tube array, which is based on an engine combustion chamber provided with a support plate 11 and a cavity 12. Figure 1 As shown, the test device includes a photomultiplier tube array, which is connected to a multi-channel data acquisition system 8 and a processing terminal 9 in sequence through an IV conversion and signal enhancement module 6; the multi-channel data acquisition system 8 is a measurement and control box, and its total number of available acquisition channels is 45; the maximum acquisition frequency is 15K; an automatic trigger acquisition system can be set to facilitate determining the zero time of data acquisition, and the automatic trigger acquisition can generally be started when the heater is started or at the ignition time.

[0039] The test device also includes a pressure sensor arranged in the engine combustion chamber and a camera arranged outside the engine combustion chamber window. The pressure sensor and the camera are used to collect the pressure signal of the combustion chamber and shoot the combustion chamber flame image respectively.

[0040] like Figure 2 As shown, the photomultiplier tube array specifically includes:

[0041] The three sensor array mounting members 2 are all plate-type structures, provided with a plurality of mounting holes 10 arranged horizontally and vertically to form an m*n array, m≥1, n≥2; and are respectively arranged outside the observation windows at the top and both sides of the combustion chamber.

[0042] m*n photomultiplier tubes, each comprising m*n collimating lenses 3 , are mounted on each mounting hole 10 ; each collimating lens 3 is connected to a photodiode 5 via an optical fiber 4 .

[0043] Among them, each photomultiplier tube is used to observe the flame combustion state in the area from the rear edge 13 of the support plate to the front edge 14 of the concave cavity in the combustion chamber and obtain a photoelectric signal; the IV conversion and signal enhancement module 6 is used to receive and enhance the photoelectric signal; the processing terminal 9 is used to analyze and process the received photoelectric signal, pressure signal and flame image to establish a mapping relationship between the photoelectric signal and the flame state; the data terminal 9 is also used to realize feedback control of the engine according to the received photoelectric signal.

[0044] Key mappings include the relationship between pressure and photoelectric signals, and between photoelectric signals and flame brightness images. First, the mapping relationship from pressure to photoelectric signals is derived, illustrating that during combustion state changes such as lean burnout, sudden changes in the pressure signal lag behind those in the photoelectric signal. This lag is attributed to the slow dissipation of pressure waves in the restricted flow path after flame quenching during flameout evolution, due to structural constraints and residual heat. The relationship between the photoelectric and flame brightness images illustrates the specific evolution of the combustion chamber flame morphology during this photoelectric signal reduction process.

[0045] In some embodiments, in each sensor array mount 2:

[0046] like Figure 2 As shown, the line connecting the centers of the m mounting holes 10 in the first column is at a distance l from the rear edge 13 of the support plate, and the line connecting the centers of the m mounting holes 10 in the nth column points to the front edge 14 of the cavity; l represents the front edge position of the fire in the combustion chamber.

[0047] The calculation process of l is as follows: first, the fuel atomization and fragmentation time and ignition delay time are determined based on the temperature, pressure and equivalence ratio of the combustion chamber under the incoming flow conditions. Then, they are multiplied by the local airflow velocity in the combustion chamber to obtain the estimated ignition front position. Finally, on this basis, the starting position of the sensor array test is obtained.

[0048] In some embodiments, as Figure 3 As shown, the support plate 11 is a triangular pyramid structure and is located in the sensor array mounting member 2 at the top of the combustion chamber:

[0049] If m is an odd number, the centerline of the middle row of mounting holes 10 coincides with the symmetrical centerline of the support plate 11;

[0050] If m is an even number, the rows of mounting holes 10 are symmetrically arranged about the symmetry center line of the support plate 11 .

[0051] In some embodiments, the optical fiber 4 is a quartz optical fiber with one input and multiple outputs, and both the input end and the output end of the optical fiber 4 are planar optical fiber heads.

[0052] In some embodiments, the IV conversion and signal enhancement module 6 is connected to a power supply 7. The power supply 7 inputs 220V AC and outputs 5V DC. The power supply voltage of the IV conversion and signal enhancement module 6 is 5V, and its multiplication factor is adjusted according to the corresponding operating conditions to ensure that the tested voltage signal is within the range.

[0053] The present invention also provides a method for using an engine combustion state test device based on a photomultiplier tube array. The engine combustion state test device based on a photomultiplier tube array includes the following contents:

[0054] Step 1: Photomultiplier tube arrays are arranged outside the observation windows on both sides and the top of the engine combustion chamber; specifically: sensor array mounting parts 2 are set outside the quartz glass observation windows on both sides and the top of the engine combustion chamber, and collimating lenses 3 are installed on the sensor array mounting parts 2 accordingly. Each collimating lens 3 is connected to a photodiode 5 through an optical fiber 4. Each photodiode 5 is connected to an IV conversion and signal enhancement module 6, and then connected to a processing terminal 9.

[0055] Step 2: Data processing is performed on the photoelectric signals obtained by the photomultiplier tube array; data processing includes normalization, cropping, and denoising.

[0056] Step 3: Collect the combustion chamber pressure test signal and take a flame image of the combustion chamber; based on the pressure test signal and flame image, match them with the photoelectric signal in time and space to identify the combustion mode of the combustion chamber corresponding to the photoelectric signal; the combustion mode includes strong combustion mode, weak combustion mode and undesirable state.

[0057] Step 4: According to the determined combustion mode, during the actual operation of the engine, the photoelectric signal obtained in real time by the photomultiplier tube array can be used to monitor whether the combustion chamber is in a normal working state of the strong combustion mode.

[0058] In some embodiments, in step 3, the specific method of matching the photoelectric signal in time and space is:

[0059] The combustion chamber pressure signal and flame image at the same position in the combustion chamber at the same time are compared with the corresponding photoelectric signal, the corresponding photoelectric signal characteristics are analyzed, and a mapping relationship between the photoelectric signal and the combustion mode of the combustion chamber is established to determine whether the combustion mode of the combustion chamber is a strong combustion mode, a weak combustion mode or an undesirable state.

[0060] Example

[0061] Based on the previous numerical simulation method, a ground direct connection hot test was carried out. Figure 4 As shown, a sensor array mounting assembly 2 is installed outside the engine, located above the flame stabilization zone of the combustion chamber. A collimating lens 3 and subsequent equipment are installed in mounting holes 10. To ensure that the photomultiplier tube array can fully cover the intense reaction area of ​​the support plate-cavity flame stabilizer under different combustion modes, four photomultiplier tubes are installed at equal intervals. These installed photomultiplier tubes are designated L1 to L4, and their corresponding positions are: L1 corresponds to above the rear edge of the cavity; L2 corresponds to above the recirculation flame stabilization zone of the cavity; L3 corresponds to above the leading edge of the cavity; and L4 corresponds to above the recirculation flame stabilization zone at the rear edge of the support plate.

[0062] See also Figure 5 , which represents a continuous flame brightness image during the lean burnout process. Lean burnout refers to the process where the fuel flow rate decreases, the combustion chamber equivalence ratio drops, the combustion intensity weakens, the combustion chamber cannot maintain a high-pressure operating state, and the flame is quenched.

[0063] During the test, the flame image obtained by setting a high-speed camera was observed. Figure 4 (a) and Figure 4 The flame highlight area in (b) is basically located between the rear edge of the support plate and the concave cavity, which verifies that the sensor array installation position of the present invention can effectively monitor the flame stabilization zone of the combustion chamber. The flame brightness in Figure (b) has dropped significantly compared to Figure (a), so it is judged that the flame brightness in Figure (a) corresponds to a strong combustion mode, while the flame brightness in Figure (b) corresponds to a weak combustion mode. Plan the flame highlight area in the image and normalize it according to steps 2 and 3 to obtain Figure 5 The Area_100 light intensity signal is used as the basis to establish the mapping relationship between the photoelectric signal and the combustion mode.

[0064] Regarding the mapping relationship between pressure and photoelectric signal, through analysis of specific data, it is found that during the flameout process, the flame brightness signal suddenly dropped (around 4.4 seconds), and the pressure signal remained at 0.12MPa, with no downward trend; around 4.9 seconds, the pressure suddenly dropped, and at this moment the photoelectric signal completely dropped to a state close to 0, indicating that the flame was completely quenched in this state, and the engine pressure was maintained by the flame in the rear combustion chamber; Regarding the mapping relationship between photoelectric signal and flame brightness, through analysis of specific data, it can be seen that both of them dropped to a low-brightness state of flame quenching (the value is close to 0) at basically the same time.

[0065] See also Figure 6 Comparison chart of photoelectric signals and pressure signals during lean flameout. Stage I is strong combustion mode, stage II is weak combustion mode, and stage III is an undesirable state. Area_100 represents the area of ​​the image enclosed by pixels with grayscale values ​​greater than 100 in the captured spontaneous flame brightness image, indicating the area of ​​the high-brightness area; Gray_sum represents the sum of all grayscale values ​​in the captured spontaneous flame brightness image, indicating the overall brightness within the combustion chamber shooting window at this moment.

[0066] After processing the photoelectric signal according to steps 2 and 3, and analyzing its intensity and fluctuations in combination with the aforementioned Area_100 light intensity signal, a mapping relationship between the photoelectric signal and the combustion mode can be established:

[0067] Throughout the entire engine combustion phase, the signal intensity and fluctuations at positions L1 and L2 closely match the highlight flame brightness signal Area_100, demonstrating a mapping relationship between photoelectric signals and combustion modes. In Phase I, the photoelectric normalized signal values ​​at position L1 ranged from 7.21% to 67.18%, with a time-average of 33.20%. The photoelectric normalized signal values ​​at position L2 ranged from 13.03% to 69.57%, with a time-average of 40.47%. Both values ​​were relatively high, thus classifying Phase I as a strong combustion mode. In stage II, the photoelectric normalized signal value at the L1 position was in the range of 1.37% to 8.64%, with an average value of 4.43%. The photoelectric normalized signal value at the L2 position was between 1.67% and 17.66%, with an average value of 8.31%. Compared with stage I, the signal value showed a significant decrease, so stage II was classified as a weak combustion mode; in stage III, the photoelectric normalized signal values ​​were all below 2.5%, with no obvious fluctuations, and it was classified as an unsatisfactory combustion mode.

[0068] See also Figure 7Comparison of photoelectric signals and flame brightness changes during lean flameout. Stage I represents strong combustion, Stage II represents weak combustion, and Stage III represents an undesirable state. First-S1 represents the pressure signal curve near L1, and First-S2 represents the pressure signal curve near L2. After processing the collected pressure signal according to steps 2 and 3, its intensity and fluctuation are compared and analyzed in combination with the photoelectric signal:

[0069] In Phase I, the normalized photoelectric signal was strongest at positions L1 and L2, and weakest at position L4. The pressure signal was also strongest and fluctuated dramatically during this phase. In Phase II, the photoelectric signal from L1 to L4 decreased overall, and a sudden pressure drop occurred during this period. This indicates that the pressure signal detected the transition from strong to weak combustion in the combustion chamber, but this detection was delayed compared to the photoelectric signal. In Phase III, the photoelectric signal dropped to its lowest level and remained essentially stable, while the pressure signal also experienced a significant drop during this period. This indicates that when the combustion mode changes, the photoelectric signal changes before the pressure signal.

[0070] The above experiments verified that photoelectric signals can be used as combustion mode identification signals. The signals from the photomultiplier tube array test system can be used to identify the corresponding combustion mode, enabling combustion state testing. Based on this, control can be performed when the mode changes, stabilizing combustion in a strong combustion mode. In summary, the test device used in the present invention is suitable for accurately identifying and real-time monitoring the combustion state of engines with flame stabilization structures.

Claims

1. An engine combustion state test device based on a photomultiplier tube array, characterized in that: Based on an engine combustion chamber provided with a support plate (11) and a cavity (12), the test device includes a photomultiplier tube array, and the photomultiplier tube array is sequentially connected to a multi-channel data acquisition system (8) and a processing terminal (9) through an IV conversion and signal enhancement module (6); The testing device further includes a pressure sensor disposed in the engine combustion chamber and a camera disposed outside the engine combustion chamber window, wherein the pressure sensor and the camera are used to collect the pressure signal of the combustion chamber and capture the flame image of the combustion chamber respectively; The photomultiplier tube array specifically includes: Three sensor array mounting members (2) are all plate-type structures, provided with a plurality of mounting holes (10) arranged horizontally and vertically to form an m*n array, where m≥1 and n≥2; and are respectively arranged outside the observation windows at the top and both sides of the combustion chamber; m*n photomultiplier tubes, each comprising m*n collimating lenses (3), respectively mounted on each of the mounting holes (10); each of the collimating lenses (3) is connected to a photodiode (5) via an optical fiber (4); Each of the photomultiplier tubes is used to observe the flame combustion state in the area from the rear edge (13) of the support plate to the front edge (14) of the cavity in the combustion chamber and obtain a photoelectric signal; the IV conversion and signal enhancement module (6) is used to receive and enhance the photoelectric signal; the processing terminal (9) is used to analyze and process the received photoelectric signal, pressure signal and flame image to establish a mapping relationship between the photoelectric signal and the flame state; the data terminal (9) is also used to realize feedback control of the engine according to the received photoelectric signal.

2. The engine combustion state testing device based on a photomultiplier tube array according to claim 1, characterized in that: In each of the sensor array mounting members (2): The distance between the center lines of the m mounting holes (10) in the first column and the rear edge (13) of the support plate is l, and the distance between the center lines of the m mounting holes (10) in the nth column points to the front edge (14) of the cavity; l represents the front edge position of the ignition in the combustion chamber.

3. The engine combustion state testing device based on a photomultiplier tube array according to claim 2, characterized in that: The support plate (11) is a triangular pyramid structure and is located in the sensor array mounting member (2) at the top of the combustion chamber: If m is an odd number, the center line of the middle row of mounting holes (10) coincides with the symmetrical center line of the support plate (11); If m is an even number, the mounting holes (10) in each row are symmetrically arranged about the symmetry center line of the support plate (11).

4. The engine combustion state testing device based on a photomultiplier tube array according to any one of claims 1 to 3, characterized in that: The optical fiber (4) adopts a quartz optical fiber with one input and multiple outputs, and both the input end and the output end of the optical fiber (4) are planar optical fiber heads.

5. The engine combustion state testing device based on a photomultiplier tube array according to any one of claims 1 to 3, characterized in that: The IV conversion and signal enhancement module (6) is connected to a power supply (7).

6. A method for using an engine combustion state test device based on a photomultiplier tube array, characterized in that: The engine combustion state testing device based on a photomultiplier tube array according to any one of claims 1 to 5 comprises the following contents: Step 1: Place photomultiplier tube arrays outside the observation windows on both sides and top of the engine combustion chamber; Step 2: performing data processing on the photoelectric signal obtained by the photomultiplier tube array; Step 3: Acquire a combustion chamber pressure test signal and capture a flame image of the combustion chamber; based on the pressure test signal and the flame image, match them with the photoelectric signal in time and space to identify the combustion mode of the combustion chamber corresponding to the photoelectric signal; Step 4: According to the determined combustion mode, during the actual operation of the engine, the photoelectric signal obtained in real time by the photomultiplier tube array can be used to monitor whether the combustion chamber is in a normal working state of the strong combustion mode.

7. The method of use according to claim 6, wherein: In step 3, the specific method for matching the photoelectric signal in time and space is: The combustion chamber pressure signal and flame image at the same position in the combustion chamber at the same time are compared with the corresponding photoelectric signal, the corresponding photoelectric signal characteristics are analyzed, and a mapping relationship between the photoelectric signal and the combustion mode of the combustion chamber is established to determine whether the combustion mode of the combustion chamber is a strong combustion mode, a weak combustion mode or an undesirable state.

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