Double-rotor surface pressure measuring system and method based on double-endoscopic pressure-sensitive coating

Abstract

The invention discloses a birotor surface pressure measurement system and method based on double endoscopic pressure sensitive paint, and belongs to the technical field of turbomachinery pressure measurement. The method mainly comprises a double-endoscopic type optical pressure sensitive measuring system, a double-rotor phase locking system of a photoelectric sensor and an encoder and a double-endoscopic type rotor surface pressure synchronous measuring method, excitation and imaging of PSP are integrated in the same hard rod type endoscope, an optical straight rod endoscope with a 70-degree viewing angle is adopted, the visual field angle is 90 degrees, and the optical straight rod endoscope and the optical straight rod endoscope are integrated. And the endoscope rod extends into the flow field for a certain length, so that the acquisition of a global rotor blade image is realized. An endoscopic detection hole is formed, an optical endoscope is installed on the wall face of a cartridge receiver, a camera and the endoscope are fixed through a three-dimensional displacement mechanism, and the stability of an endoscopic measurement system is guaranteed. The reflective patch is attached to a rotor rotating shaft, the photoelectric sensor directly faces the reflective patch, external trigger signals of the photoelectric sensor are transmitted to the signal generator and the multi-channel data acquisition system respectively, and the signals are used for controlling light emitting of the light source and shooting of the camera on one hand and used for phase locking of the rotor on the other hand. And the encoder is arranged at one end of the motor shaft, is connected with the multi-channel data acquisition system, and is combined with the photoelectric sensor to jointly realize phase locking of the double rotors. Dark background images Id1 and Id2 and reference images Ir1 and Ir2 of the birotor are shot, and the corresponding reference pressures are Pr1 and Pr2 respectively. A phase-locked enhanced image synchronous acquisition method is adopted to obtain light-emitting images I1 and I2 of the surface of the rotor. And finally obtaining pressure distribution P1 and P2 of the surfaces of the double-rotor blades through image processing and a pressure sensitive coating calibration relational expression.

Description

Technical Field

[0001] The invention belongs to the technical field of impeller machinery pressure measurement, and in particular relates to a rotor surface pressure measurement method based on endoscopic optical pressure sensitive coating. Background Art

[0002] In order to meet the development needs of modern aircraft engines, designers have proposed counter-rotation technology to improve the overall performance of the engine. The proposal of the counter-rotation engine scheme is a revolutionary progress in the structural design of aircraft engines. The counter-rotation scheme has unique advantages: in terms of structure, due to the elimination of the stator between the two rows of rotors, under the premise of achieving the same boost ratio, the counter-rotation compressor makes the axial length of the engine shorter and lighter, which can improve the thrust-to-weight ratio of the aircraft engine. In terms of aerodynamics, due to the elimination of the stator components, the aerodynamic losses caused by factors such as friction and leakage related to it are eliminated, thereby improving the aerodynamic efficiency of the turbomachinery. In addition, the counter-rotation makes the gyroscopic torque generated by the rotors cancel each other, reducing the adverse effects of the gyroscopic torque effect on the engine and the aircraft, thereby improving the flight performance of the aircraft.

[0003] As the rotating parts of turbomachinery, the surface pressure of rotor blades is one of the important aerodynamic parameters. The surface pressure of blades reflects the interaction between blades and passage gas, can characterize the development of blade boundary layer flow state, can be used to judge flow separation, shock wave intensity and position, and is of great significance for the analysis of blade flow loss mechanism. With the continuous development of modern aero-engines towards high thrust-to-weight ratio and high load, the internal flow of compressors is extremely complex, especially in counter-rotating environments. Therefore, obtaining the pressure distribution on the surface of compressor rotor blades can provide key information for counter-rotating compressor aerodynamic design, calculation model aerodynamic load distribution, flow mechanism analysis, verification of CFD accuracy, etc., and is an important way to improve compressor performance. However, the high load, high speed and strong unsteady effect of turbomachinery are the main constraints for carrying out rotor blade surface pressure measurement, resulting in the acquisition of rotor surface pressure has always been one of the difficult problems in the field of turbomachinery.

[0004] In recent years, due to the advantages of optical pressure sensitive paint (PSP) pressure measurement technology such as high spatial resolution, non-invasive, and global pressure field measurement, PSP measurement technology has continued to develop and improve, providing a feasible and refined measurement method for the pressure field measurement of the impeller machinery rotor surface. When the PSP paint is excited by a light source of a specific wavelength, the luminous intensity of the paint is sensitive to the pressure on the model surface, thereby obtaining a quantitative relationship between the model surface pressure and the PSP luminous intensity. By using a camera to capture the PSP luminous image, each pixel in the image can be regarded as an independent pressure sensor. After image processing and calibration, the pressure distribution on the model surface can be obtained.

[0005] However, due to the geometric limitations of the measured model, the motion deformation of the model, the occlusion of the optical path, the image motion blur caused by the rotating model and other issues, the application of PSP measurement technology in the field of turbomachinery has brought challenges, resulting in relatively few PSP measurement studies in turbomachinery. PSP has been studied more on the stationary parts of the compressor, while the high-speed rotation of the compressor has put higher requirements on the performance of the PSP measurement system, resulting in less research on the rotating parts. Since the measurement of rotating parts is limited by the measurement environment, the measurement test of the rotor surface is difficult, and the PSP measurement research of the rotor is even more scarce. Therefore, there is still a lack of research on the measurement of compressor rotor surface pressure using PSP measurement technology.

[0006] Although PSP measurement technology has great advantages in high spatial resolution and full-domain measurement, it still faces great challenges when measuring the pressure field of the dual rotors of a counter-rotating compressor. Existing PSP measurement research is only for a single stage, especially the first stage or the imported fan, and the optical path layout is relatively easy to implement. However, for the whole machine test bench, the test space is severely limited and the blade density is large. In addition, the layout structure of the rotor + stator makes it impossible to illuminate from the inlet or outlet, making it difficult to photograph the rotor blades between the rows of the impeller machinery. The problem of optical path obstruction is particularly prominent, resulting in the actual pressure distribution on the surface of the rotor blades between the rows unknown, and it is impossible to study the flow mechanism on the surface of the rotor blades between the rows from an experimental perspective. Secondly, the two rows of rotors of the counter-rotating compressor rotate in opposite directions, and the two rows of rotors can run at different speeds. At present, there is no measurement of the dual rotors, and their actual flow characteristics are unclear. How to achieve the synchronous acquisition of PSP images of the dual rotors of the counter-rotating compressor is a difficult problem that needs to be solved in the acquisition of dual rotor PSP images. In addition, although the optical window can solve the problem of partial light path obstruction, the optical window is highly dangerous and has a great degree of damage to the impeller machinery, which poses a great challenge to the safety of the impeller machinery in actual measurement. In addition, there is not enough space to open the optical window, and the coverage of the optical window is limited, which can only provide a limited optical path, and the problem of limited light path still exists.

[0007] Therefore, in view of the above problems, it is necessary to develop a method for measuring the dual-rotor surface pressure of optical pressure-sensitive coatings in a small and limited test space of the whole machine test bench to solve the problem of dual-rotor surface pressure measurement of impeller machinery. Summary of the invention

[0008] In order to solve the difficulties faced in measuring the surface pressure of the dual rotors of impeller machinery and consider the measurement requirements of the surface pressure of the dual rotor blades, the present invention provides a dual rotor surface pressure measurement system and method based on dual endoscopic pressure sensitive coating, which can effectively solve the above problems.

[0009] The present invention provides a dual-rotor surface pressure measurement system and method based on dual-endoscopic pressure sensitive coating, which mainly include: a dual-rotor surface pressure measurement system based on dual-endoscopic PSP and a dual-rotor surface pressure measurement method based on dual-endoscopic PSP.

[0010] A rotor surface pressure measurement system based on dual-endoscopic pressure-sensitive coating is characterized by comprising a dual-endoscopic optical pressure-sensitive measurement synchronization system and a dual-rotor phase-locked system of "photoelectric sensor + encoder", wherein the excitation and imaging of PSP are integrated in the same rigid rod endoscope, and an optical straight rod endoscope with a viewing angle of 70° and a field of view of 90° is used to obtain the full-domain rotor blade image. The measurement system is mainly composed of an optical rigid rod endoscope, a light-guiding optical fiber, a CCD camera, a 650±15nm filter, a C-mount adapter, a 405nm excitation light source, a signal generator, a photoelectric sensor, a reflective patch, an encoder, a multi-channel data acquisition system, a three-dimensional displacement mechanism, a computer, etc.

[0011] In order to achieve pressure measurement on the entire rotor blade surface, the endoscope rod is extended into the flow field for a certain length. By opening an endoscope hole, the optical endoscope is installed on the wall of the casing. The camera and endoscope are fixed with a three-dimensional displacement mechanism to ensure the stability of the endoscope measurement system. The PSP excitation light source is connected to the endoscope light guide hole through the light guide fiber, and the PSP excitation light is introduced into the front end of the endoscope. The camera is connected to the eyepiece end of the endoscope through a C-mount adapter, and a filter is installed between the adapter and the camera to filter out the PSP excitation light.

[0012] The reflective patch is applied to the rotor rotating shaft, and the photoelectric sensor is facing the reflective patch. The external trigger signal of the photoelectric sensor is transmitted to the signal generator and the multi-channel data acquisition system respectively. The signal is used to control the light source and the camera on the one hand, and the phase lock of the rotor on the other hand. The encoder is installed at one end of the motor shaft, connected to the multi-channel data acquisition system, and combined with the photoelectric sensor to achieve the phase lock of the dual rotors. The light source is connected to the signal generator to control the light source to emit light. At the same time, the camera is also connected to the signal generator to control the camera to shoot.

[0013] A dual-rotor surface pressure measurement method based on dual-endoscopic pressure sensitive coating, the method includes synchronous excitation and imaging based on dual-endoscopic PSP and a dual-rotor PSP image synchronous acquisition method based on phase-locked enhancement, the steps are as follows:

[0014] (1) Endoscopic PSP excitation and imaging: The PSP excitation light source is introduced into the front end of the endoscope through the light-guiding optical fiber to achieve the excitation of the PSP coating on the blade surface. After the PSP coating is excited, it emits emission light, which is focused by the objective lens of the endoscope, amplified by the eyepiece of the endoscope, and then filtered out by the filter. Finally, it reaches the CCD camera for imaging, achieving the excitation and imaging of the PSP;

[0015] (2) Taking the rotor stationary state as the reference state for PSP measurement, the camera exposure time is determined when the rotor is stationary;

[0016] (3) The light source works in a trigger pulse mode, and the pulse width time of the light source under each experimental condition is determined according to the image motion blur evaluation and the blade tip speed of the experimental state;

[0017] (4) Every time the reflective patch passes over the photoelectric sensor, the photoelectric sensor emits a laser to illuminate the reflective patch and receives the reflective signal of the reflective patch. The TTL signal is transmitted to the signal generator through the signal transmission line as a light source and an external trigger signal of the camera, which is used to control the light source pulse and camera shooting. On the other hand, the external trigger signal is transmitted to the multi-channel data acquisition system. When the motor rotates one circle, the encoder outputs a certain number of pulse signals, which are transmitted to the multi-channel data acquisition system and combined with the pulse signal of the photoelectric sensor. The relative phase of the dual rotors is finally determined by calculating the number of encoder and photoelectric sensor pulses.

[0018] (5) Under the PSP reference state, turn off the excitation light source and the light source in the experimental environment, turn on the CCD camera to take dark background images respectively. The dark background images taken at this time are I d1 ,I d2 ;

[0019] (6) In the PSP reference state, turn on the excitation light source and CCD camera to capture the dual-rotor PSP reference image I r1 ,I r2 , the pressures in the reference state are P r1 , P r2 , corresponding to the atmospheric pressure in the experimental environment;

[0020] (7) Under the experimental conditions, the camera, light source, and signal generator are turned on synchronously. Each time the rotor blades are in the same phase, the signal generator receives the pulse signal of the photoelectric sensor and controls the light source to pulse excite the PSP coating on the surface of the dual rotors. During this period, the camera works in the long exposure mode. After multiple cycles of image superposition, the PSP luminescent images of the dual rotor surface are obtained, which are I1 and I2 respectively. At this time, the corresponding pressures on the dual rotor blade surfaces are P1 and P2 respectively.

[0021] (8) Dual rotor surface PSP luminescence images I1, I2 and reference image I r1 ,I r2 , firstly, distortion processing is performed to remove the influence of distortion effect, and then the dark background image I is subtracted. d1 ,I d2 After image registration and ratio processing, the ratio images are obtained as follows: r1 / I1、I r2 / I2;

[0022] (9) The pressure distribution on the surface of the rotor blade is calculated based on the pressure-light intensity calibration relationship obtained in advance.

[0023]

[0024] Among them, P ref and I ref are the pressure and PSP light intensity in the reference state, P and I are the pressure and PSP light intensity in the experimental state, A and B are constants related to temperature T, which can be obtained through calibration.

[0025] By adopting the above technical solution, the present invention has the following beneficial effects:

[0026] The present invention proposes a dual-rotor surface pressure measurement system and method based on dual-endoscopic pressure-sensitive coating, and its beneficial effects are as follows:

[0027] (1) It can solve the problem of limited light path caused by high risk of optical windows, great damage to impeller machinery and limited coverage.

[0028] (2) By integrating PSP excitation and image acquisition into the same endoscope shaft, the surface pressure of the rotor between rows of the impeller machinery can be obtained;

[0029] (3) It can effectively solve the problem of synchronous measurement of surface pressure of dual rotors of turbomachinery;

[0030] (4) This measurement method can realize non-destructive measurement of the surface pressure of dual rotor blades in a limited test space;

[0031] (5) The phase-locking system based on photoelectric sensor + encoder has high phase-locking accuracy and good economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the following will introduce the drawings required for the specific implementation or the prior art description. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. Figure 1Schematic diagram of a dual-rotor surface pressure measurement system based on dual-endoscopic optical pressure-sensitive coating. Figure 2 This is a schematic diagram of the installation and fixation of the endoscope system. Figure 3 Schematic diagram of endoscope lighting and shooting angles.

[0033] Explanation of the numbers in the figure: casing 1, rotor blades sprayed with PSP 2 and 3, reflective patches 4 and 39, photoelectric sensors 5 and 38, gearboxes 6 and 37, motors 7 and 36, encoders 8 and 35, rotating shafts 9 and 34, signal transmission lines 10, 11, 32 and 33, sprayed with TSP (Temperature sensitive paint) blades 12 and 31, optical endoscopes 13 and 30, endoscope light guide holes 14 and 29, optical fibers 15 and 28, endoscope C-mount adapters 16 and 27, 650±15nm filters 17 and 26, CCD cameras 18 and 25, 405nm excitation light sources 19 and 24, signal generators 20 and 23, multi-channel signal acquisition system 21, computer 22, fixed block 40, endoscope hole 41, three-coordinate displacement mechanism 42, CH1 port 43 of signal generator 23, CH2 port 44 of signal generator 23, TRIG port 45 of signal generator 23, CH1 port 46 of signal generator 20, CH2 port 47 of signal generator 20, TRIG port 48 of signal generator 20. DETAILED DESCRIPTION

[0034] The following is a further detailed description of the dual rotor surface pressure measurement system and method based on the dual endoscope PSP in conjunction with specific examples and drawings. The described embodiments are only part of the embodiments of the present invention, but not all of them.

[0035] The present invention proposes a dual-rotor surface pressure measurement system and method based on a dual-endoscopic PSP, including: a dual-rotor surface pressure measurement synchronization system based on a dual-endoscopic PSP and a dual-rotor surface pressure synchronization measurement method based on a dual-endoscopic PSP. The system and method are mainly used for the dual-rotor surface pressure synchronization measurement in a whole-machine test bench where the test space is limited and there is severe light path obstruction. The method has the advantages of not destroying the impeller mechanical aerodynamic layout and geometric structure, and can realize non-destructive measurement of the full-range pressure of the dual-rotor blades.

[0036] The dual-rotor surface pressure measurement system based on dual-endoscopic PSP established by the present invention mainly comprises: a dual-endoscopic pressure sensitive coating synchronous measurement system and a dual-rotor phase-locked system of "photoelectric sensor + encoder", which mainly comprises an organic box (1), rotor blades (2) and (3) sprayed with PSP, reflective patches (4) and (39), photoelectric sensors (5) and (38), gearboxes (6) and (37), motors (7) and (36), encoders (8) and (35), rotating shafts (9) and (34), signal transmission lines (10), (11), (32) and (33), blades (1) sprayed with TSP 2) and (31), optical endoscope (13) and (30), endoscope light guide hole (14) and (29), optical fiber (15) and (28), endoscope C-mount adapter (16) and (27), 650±15nm filter (17) and (26), CCD camera (18) and (25), 405nm excitation light source (19) and (24), signal generator (20) and (23), multi-channel signal acquisition system (21), computer (22), fixed block (40), endoscope hole (41), three-coordinate displacement mechanism (42), etc. The specific system composition and connection method are as follows: Figure 1 As shown, the installation and fixation of the endoscope system is as follows Figure 2 The specific connection and fixing methods of the system components are as follows:

[0037] In order to achieve the pressure measurement on the entire rotor blade surface, an optical straight-rod endoscope with a viewing angle of 70° is used. The viewing angle is 90°, and the endoscope rod extends a certain length into the flow field. The lighting and shooting directions are as follows: Figure 3 shown.

[0038] The composition and installation principle of the dual endoscope system are the same, so a single endoscope system is used as an example for explanation. The optical endoscope (13) is connected to the CCD camera (18) through a C-mount adapter (16), and a filter (17) is installed at the front end of the CCD camera; the endoscope light guide hole (14) is connected to the light guide fiber (15), and the PSP excitation light source (19) is introduced into the endoscope through the light guide fiber.

[0039] An endoscope hole (41) is provided on the casing (1), one end of the endoscope objective lens is mounted in the endoscope hole, and the end of the endoscope objective lens is fixed by a fixing block (40). The endoscope and its accessories, camera, and light source are all fixedly mounted on a three-dimensional displacement mechanism (42), such as Figure 2 shown.

[0040] Photoelectric sensors (5) and (38) are respectively fixed on the bases of the gearboxes (6) and (37), facing the rotor rotating shafts (9) and (34), and reflective patches (4) and (39) are respectively attached to the rotor rotating shafts to reflect the laser light emitted by the photoelectric sensors, so as to achieve phase-locked triggering.

[0041] Encoders (8) and (35) are respectively mounted on the tail shaft of the motor and are combined with a photoelectric sensor to determine the relative phase of the dual rotor blades.

[0042] The photoelectric sensors (5) and (38) are connected to the external trigger signal TRIG ports of the signal generators (20) and (23) through signal transmission lines (10) and (33), respectively. The pulse signals of the photoelectric sensors are used for synchronous phase locking of the dual rotor blades and as external trigger signals for controlling the operation of the camera and the light source. In addition, the pulse signals of the photoelectric sensors (5) and (38) are respectively transmitted to the multi-channel data acquisition system (21); the encoders (8) and (35) transmit the pulse signals to the multi-channel data acquisition system (21) through signal transmission lines (11) and (32), respectively, and the relative phases of the dual rotor blades are determined in combination with the pulse signals of the photoelectric sensors.

[0043] The light sources (19) and (24) are connected to the CH2 ports of the signal generators (20) and (23) respectively through signal transmission lines, so as to control the light sources to perform pulse stroboscopic excitation of the coating. The CCD cameras (18) and (25) are connected to the CH1 ports of the signal generators (20) and (23) respectively, so as to control the camera to shoot. In addition, the CCD cameras (18) and (25) are connected to the computer (22) through signal transmission lines, so as to transmit and save real-time images.

[0044] The present invention provides a dual-rotor surface pressure synchronous measurement method based on dual-endoscopic pressure sensitive coating, including excitation and imaging based on dual-endoscopic PSP and a PSP image enhancement acquisition method based on phase lock, which is specifically implemented as follows:

[0045] 1) Endoscopic PSP excitation and imaging process: PSP excitation and imaging are integrated in the same rigid rod endoscope. The PSP excitation light source is introduced into the front end of the endoscope through the light-guiding optical fiber to achieve the excitation of the PSP coating on the blade surface. After the PSP coating is excited, it emits emission light, which is focused by the objective lens of the endoscope, amplified by the eyepiece of the endoscope, and then filtered out by the filter. Finally, it reaches the CCD camera for imaging, achieving the excitation and collection of PSP.

[0046] 2) Synchronous phase-locking principle and process: Every time the rotating shaft rotates one circle, every time the reflective patch sweeps over the photoelectric sensor, the photoelectric sensor emits a laser to illuminate the reflective patch, and receives the reflective signal of the reflective patch, and emits a pulse signal each time. The signal is transmitted to the signal generator through the signal transmission line, and the signal is transmitted to the light source through the CH2 port of the signal generator to control the light source to perform pulse stroboscopic; the signal is transmitted to the camera through the CH1 port to control the camera to shoot. On the other hand, the pulse signal emitted by the photoelectric sensor is transmitted to the multi-channel data acquisition system. In addition, when the rotating shaft rotates one circle, the encoder emits a fixed number of pulse signals, and the pulse signals are transmitted to the multi-channel data acquisition system. According to the pulse signal of the photoelectric sensor, the initial phase of the dual rotor is determined, and then the instantaneous phase of the dual rotor blades is obtained by calculating the number of encoder and photoelectric sensor pulses, and then the relative phase of the dual rotor blades is determined.

[0047] 3) In order to reduce the interference of ambient light and other stray light and reduce the reflective effect of the blades, black paint was sprayed on the two adjacent blades and the casing at the phase of the blade to be tested before the experiment began;

[0048] 4) Considering the dynamic balance of the impeller machinery rotor, a symmetrical spraying scheme of PSP and TSP is adopted on the rotor blades, such as Figure 1 As shown, the temperature sensitive coating TSP was used to evaluate the effect of temperature on PSP measurement results.

[0049] 5) According to the actual shape of the blade, mark no less than 6 marking points on the surface of the blade to be measured. More marking points need to be arranged where the curvature of the blade is large for image registration;

[0050] 6) The rotor stationary state is used as the reference state for PSP measurement. The camera exposure time when the gray value of the PSP image reaches 2 / 3 of the camera full well value is used as the final exposure time to determine the camera exposure time.

[0051] 7) The light source works in a trigger pulse mode, and the pulse width time of the light source under each experimental condition is determined according to the image motion blur evaluation and the blade tip speed of the experimental state.

[0052] 8) Under the PSP reference state, turn off the excitation light source and the light source in the experimental environment, turn on the CCD camera to shoot, and then take a dark background image I d1 ,I d2 ;

[0053] 9) In the PSP reference state, turn on the excitation light source and CCD camera to take the dual-rotor PSP reference image I and r1 ,I r2 , the pressures in the reference state are P r1 , P r2, which corresponds to the atmospheric pressure in the experimental environment.

[0054] 10) Under the experimental conditions, the camera, light source, and signal generator are turned on synchronously. Each time the rotor blades are in the same phase, the signal generators (20) and (23) receive the pulse signals of the photoelectric sensors (5) and (38), respectively, and control the light sources (19) and (24) to pulse excite the PSP coating on the surfaces of the rotors (2) and (3). During this period, the camera works in a long exposure mode. After multiple cycles of image superposition, the PSP luminescent images of the rotor surface are obtained, which are I1 and I2, respectively. At this time, the corresponding pressures on the surfaces of the dual rotor blades are P1 and P2, respectively.

[0055] 11) Since the endoscope uses a wide-angle lens, it brings the problem of image distortion, so the image needs to be dedistorted; after dedistortion using the fisheye lens model distortion algorithm, the double rotor surface PSP luminous images I1, I2 and the reference image I r1 ,I r2 , respectively subtract the dark background image I d1 ,I d2 ; Align the experimental image with the reference image; after alignment, perform image comparison processing I r1 / I1、I r2 / I2, eliminates the effects caused by the non-uniformity of the excitation irradiation and the non-uniformity of the photosensitive molecules in the coating layer;

[0056] 12) The pressure distribution on the surface of the rotor blade is calculated based on the previously obtained pressure-light intensity calibration relationship.

[0057]

[0058] Among them, P ref and I ref are the pressure and PSP light intensity in the reference state, P and I are the pressure and PSP light intensity in the experimental state, A and B are constants related to temperature T, which can be obtained through calibration.

[0059] The dual-rotor surface pressure measurement system and method based on dual-endoscopic PSP proposed in the present invention can realize the synchronous measurement of the dual-rotor surface pressure in a small and limited test space, which can effectively solve the problems of light path obstruction and light path limitation, and realize the measurement of the surface pressure of the dual-rotor blades between rows of impeller machinery. In addition, during actual measurement, this method only needs to open a small-sized endoscopic hole on the wall of the impeller machinery, which is convenient for actual processing and installation, saves experimental costs, and has the advantage of non-destructive and refined pressure measurement. In addition, the phase-locked system based on photoelectric sensor + encoder has high phase-locked accuracy and good economy.

[0060] Finally, it should be noted that the above is only a specific implementation method of the present disclosure and is only used to illustrate the technical solution of the present invention, but the protection scope of the present disclosure is not limited to this. Any technician familiar with the technical field can easily modify or replace it within the technical scope disclosed in the present disclosure, and it should be covered by the protection scope of the present disclosure.

Claims

1. A dual-rotor surface pressure measurement system based on dual-endoscopic pressure-sensitive coating, characterized in that: The invention comprises a dual-endoscopic pressure sensitive coating measurement system and a dual-rotor phase-locked system of "photoelectric sensor + encoder", which mainly comprises an organic box (1), rotor blades (2) and (3) sprayed with PSP, reflective patches (4) and (39), photoelectric sensors (5) and (38), gearboxes (6) and (37), motors (7) and (36), encoders (8) and (35), rotating shafts (9) and (34), signal transmission lines (10), (11), (32) and (33), blades sprayed with TSP (12) and (31), optical endoscopes (13) and (30), endoscope guides Light holes (14) and (29), optical fibers (15) and (28), endoscope C-mount adapters (16) and (27), 650±15nm filters (17) and (26), CCD cameras (18) and (25), 405nm excitation light sources (19) and (24), signal generators (20) and (23), multi-channel signal acquisition systems (21), computers (22), fixed blocks (40), endoscope holes (41), three-coordinate displacement mechanisms (42), etc. The specific system components and connection methods are shown in FIG1 , and the installation and fixation of the endoscope system are shown in FIG2 . The specific connection and fixation methods of the system components are as follows: 1) An optical straight-rod endoscope with a viewing angle of 70° is used to shoot and illuminate the blades sprayed with PSP. The field of view is 90°, and the endoscope rod extends a certain length into the flow field. In order to obtain the full-domain rotor blade image, the lighting and shooting directions are shown in Figure 3. 2) The composition and installation principle of the dual endoscope system are the same, and a single endoscope system is used as an example for explanation. The optical endoscope (13) is connected to the CCD camera (18) through a C-mount adapter (16), and a filter (17) is installed at the front end of the CCD camera; the endoscope light guide hole (14) is connected to the light guide fiber (15), and the PSP excitation light source (19) is introduced into the endoscope through the light guide fiber. 3) An endoscope hole (41) is opened on the casing (1), one end of the endoscope objective lens is mounted in the endoscope hole, and the endoscope objective lens end is fixed by a fixing block (40). The endoscope and its accessories, camera, and light source are all fixedly mounted on the three-dimensional displacement mechanism (42). 4) Photoelectric sensors (5) and (38) are respectively fixed on the bases of the gearboxes (6) and (37), facing the rotor rotating shafts (9) and (34), and reflective patches (4) and (39) are respectively attached to the rotor rotating shafts to reflect the laser emitted by the photoelectric sensors to achieve phase-locked triggering. Encoders (8) and (35) are respectively installed on the tail shafts of the motor ends, and are combined with the photoelectric sensors to determine the relative phases of the dual rotor blades. 5) The photoelectric sensors (5) and (38) are connected to the external trigger signal TRIG ports of the signal generators (20) and (23) through signal transmission lines (10) and (33), respectively. The pulse signals of the photoelectric sensors are used for synchronous phase locking of the dual rotor blades and as external trigger signals for controlling the operation of the camera and the light source. In addition, the pulse signals of the photoelectric sensors (5) and (38) are respectively transmitted to the multi-channel data acquisition system (21); the encoders (8) and (35) transmit the pulse signals to the multi-channel data acquisition system (21) through signal transmission lines (11) and (32), respectively, and the relative phase of the dual rotor blades is determined in combination with the pulse signals of the photoelectric sensors. 6) The light sources (19) and (24) are connected to the CH2 ports of the signal generators (20) and (23) respectively through signal transmission lines, so as to control the light sources to perform pulse stroboscopic excitation of the coating. The CCD cameras (18) and (25) are connected to the CH1 ports of the signal generators (20) and (23) respectively, so as to control the camera to shoot. In addition, the CCD cameras (18) and (25) are connected to the computer (22) through signal transmission lines, so as to transmit and save real-time images.

2. A method for measuring the surface pressure of a dual rotor based on a dual endoscope pressure sensitive coating implemented by the measurement system according to claim 1, characterized in that: The steps are as follows: Step 1: Endoscopic PSP excitation and imaging process: PSP excitation and imaging are integrated into the same rigid rod endoscope. The PSP excitation light source is introduced into the front end of the endoscope through the light-guiding optical fiber to achieve the excitation of the PSP coating on the blade surface. After the PSP coating is excited, it emits emission light, which is focused by the objective lens of the endoscope, amplified by the eyepiece of the endoscope, and then filtered out by the filter. Finally, it reaches the CCD camera for imaging, achieving the excitation and collection of PSP. Step 2: Synchronous phase-locking principle and process: Every time the rotating shaft rotates one circle, every time the reflective patch sweeps over the photoelectric sensor, the photoelectric sensor emits a laser to illuminate the reflective patch, and receives the reflective signal of the reflective patch, and emits a pulse signal each time, and transmits the signal through the signal transmission line, on the one hand, to the signal generator, and transmits the signal to the light source through the CH2 port of the signal generator to control the light source to perform pulse stroboscopic; the signal is transmitted to the camera through the CH1 port to control the camera to shoot. On the other hand, the pulse signal emitted by the photoelectric sensor is transmitted to the multi-channel data acquisition system. In addition, when the rotating shaft rotates one circle, the encoder emits a fixed number of pulse signals, and transmits the pulse signals to the multi-channel data acquisition system. According to the pulse signal of the photoelectric sensor, the initial phase of the dual rotor is determined, and then the instantaneous phase of the dual rotor blades is obtained by calculating the number of encoder and photoelectric sensor pulses, and then the relative phase of the dual rotor blades is determined. Step 3: In order to reduce the interference of ambient light and other stray light and reduce the reflective effect of the blades, black paint was sprayed on the two adjacent blades and the casing at the phase of the blade to be tested before the experiment began; Step 4: Considering the dynamic balance of the turbomachinery rotor, a symmetrical spraying scheme of PSP and TSP is adopted on the rotor blades, as shown in Figure 1, and the temperature-sensitive coating TSP is used to evaluate the influence of temperature on the PSP measurement results. Step 5: According to the actual shape of the blade, mark no less than 6 marking points on the surface of the blade to be measured. More marking points need to be arranged where the curvature of the blade is large for image registration; Step 6: Take the rotor stationary state as the reference state for PSP measurement, and take the camera exposure time when the gray value of the PSP image reaches 2 / 3 of the camera full well value as the final exposure time to determine the camera exposure time. Step 7: The light source works in the trigger pulse mode. According to the image motion blur evaluation and the blade tip speed of the experimental state, the pulse width time of the light source under each experimental condition is determined. Step 8: Under the PSP reference state, turn off the excitation light source and the light source in the experimental environment, turn on the CCD camera to shoot, and then take a dark background image I d1 ,I d2 ; Step 9: In the PSP reference state, turn on the excitation light source and CCD camera to take the dual-rotor PSP reference image I r1 ,I r2 , the pressures in the reference state are P r1 , P r2 , which corresponds to the atmospheric pressure in the experimental environment. Step 10: Under the experimental conditions, the camera, light source, and signal generator are turned on synchronously. Each time the rotor blades are in the same phase, the signal generators (20) and (23) receive the pulse signals of the photoelectric sensors (5) and (38), respectively, and control the light sources (19) and (24) to pulse excite the PSP coating on the surfaces of the rotors (2) and (3). During this period, the camera works in a long exposure mode. After multiple cycles of image superposition, the PSP luminescent images of the rotor surface are obtained, which are I1 and I2, respectively. At this time, the corresponding pressures on the surfaces of the dual rotor blades are P1 and P2, respectively. Step 11: Since the endoscope uses a wide-angle lens, it brings the problem of image distortion, so the image needs to be dedistorted; after dedistortion using the fisheye lens model distortion algorithm, the PSP luminous images I1, I2 and the reference image I r1 ,I r2 , respectively subtract the dark background image I d1 ,I d2 ; Align the experimental image with the reference image; after alignment, perform image comparison processing I r1 / I1、I r2 / I2, eliminates the effects caused by the non-uniformity of the excitation irradiation and the non-uniformity of the photosensitive molecules in the coating layer; Step 12: Calculate the pressure distribution on the rotor blade surface based on the previously obtained pressure-light intensity calibration relationship. Among them, P ref and I ref are the pressure and PSP light intensity in the reference state, P and I are the pressure and PSP light intensity in the experimental state, A and B are constants related to temperature T, which can be obtained through calibration.

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