A wall-adhered integrated three-dimensional endoscopic PIV probe for high temperature flow field test

Abstract

The application belongs to the technical field of aero-engine internal compressor flow field testing and optical measurement, and particularly relates to an integrated three-dimensional endoscopic PIV probe for aero-engine internal flow field measurement, which is suitable for three-dimensional velocity vector measurement of internal flow field of aero-engines, gas turbines, industrial compressors and other limited spaces. The probe is characterized by comprising an integrated probe body, a left imaging channel, a laser emission channel, a right imaging channel, an optical window, a spherical lens, a cylindrical lens, an objective lens group, a Littrow prism, a Hopkins cylindrical lens system, an eyepiece group, a blowing channel, an air inlet, an air suction port, an external connecting flange, an external laser interface, an external camera interface, an imaging camera, a laser and a target measurement area. The probe is integrated with a laser illumination channel, left and right stereo imaging channels, a cooling system and a blowing system in a high-temperature-resistant cylindrical probe body. The front end of the probe is flush and attached to the inner wall of the measured equipment. Through sheet-shaped laser illumination, double-view endoscopic imaging, window cleaning and water-cooling thermal protection, low-interference synchronous measurement of three-dimensional velocity vector field of high-temperature limited internal flow field such as a combustion chamber, a turbine or a casing is realized.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine flow field testing and optical measurement technology, specifically relating to a wall-mounted integrated three-dimensional endoscopic PIV probe for high-temperature flow field testing, which is suitable for three-dimensional velocity vector measurement of the internal flow field in high-temperature and high-pressure confined spaces such as aero-engine turbines and combustion chambers. Background Technology

[0002] In the aerodynamic performance studies of complex components such as turbines and combustion chambers of aero-engines, the velocity distribution, unsteady structure, and turbulent characteristics within the flow field are key parameters. Traditional particle image velocimetry (PIV) systems typically employ an "external" layout. By seeding tracer particles into the incoming flow and using an external sheet laser with a transparent window on the sidewall for illumination, combined with imaging by an external camera, the velocity vector field on the measurement plane can be obtained. Conventional PIV arrangements usually rely on large transparent observation windows on the sidewalls or top cover of the measurement area, with the laser sheet light and camera line of sight passing through the wall from the outside into the blade passage.

[0003] However, aero engines operate in high-temperature and high-pressure environments, and the casing, as a primary load-bearing component, has extremely high requirements for structural strength, airtightness, and contamination resistance. Installing large optical windows would severely compromise the integrity and load-bearing structure of the casing, posing significant safety hazards and often failing to meet the testing standards for the entire engine. Particularly for hot-end components such as the combustion chamber and turbine, the internal airflow temperature can reach thousands of degrees Celsius. Extreme thermal shock and sustained high-temperature environments pose a severe challenge to the survivability of measuring devices. Conventional optical glass, precision lens assemblies, and adhesive media are highly susceptible to thermal cracking, coating peeling, or performance degradation under such high-temperature conditions.

[0004] Furthermore, the internal structure of an engine is extremely compact, especially in the turbine and other blade passage areas, where the installation space is very small, physically making it impossible to install a conventional PIV observation window. Secondly, the internal flow channels of an engine are typically complex spatial curved surfaces. Creating a flat glass window on a curved surface is extremely difficult; and if a curved window is used to conform to the flow channel shape, or if optical measurements are performed directly through the curved flow channel walls, light will undergo complex refraction and reflection as it passes through different media interfaces. This leads to severe image distortion, deformation, and path deflection of the laser sheet light. This optical distortion directly causes significant errors in velocity vector calculations, resulting in measurement data that cannot accurately reflect the flow field characteristics.

[0005] The published patent CN120177823A proposes an endoscopic PIV measurement system. Although the window size is reduced by using an endoscope, it has the following significant drawbacks: First, it has low integration. Separating the illumination and imaging optical paths requires inserting the illumination and imaging probes through two or more independent probe holes, which increases the number of openings in the housing and compromises the structural integrity. Second, it can only achieve two-dimensional measurement and is difficult to obtain the three-dimensional velocity components in complex turbulence. Third, most existing endoscopic probes extend directly into the flow channel. This "invasive" measurement significantly disrupts the original flow field, generating additional shock waves, wakes, and blockage effects, leading to distorted measurement results.

[0006] Existing technologies lack a device that can withstand high-temperature environments, achieve integrated three-dimensional measurement, and minimize flow field interference under single-hole insertion conditions. To address this, a wall-mounted integrated three-dimensional endoscopic PIV probe for flow field measurement in aero-engine combustion chambers and turbines is proposed. This probe integrates a laser emission channel and two imaging channels at a specific angle within a single probe body, along with a unified, high-efficiency cooling and purging structure. The probe head features a wall-mounted cross-section design, ensuring the structural integrity of the casing while achieving high-precision, low-interference three-dimensional PIV measurement within a high-temperature confined space. Summary of the Invention

[0007] The technical problem this invention aims to solve is as follows: Traditional external PIVs (Portable Observatory Vibrators) struggle to create large windows and suffer from severe optical distortion on curved windows under high temperature, high pressure, and extremely compact space constraints in core components such as aero-engine turbines and combustion chambers. Furthermore, existing endoscopic techniques require multiple probe holes, lack effective thermal protection, and suffer from wake and shock wave interference leading to measurement distortion when the probe directly penetrates the flow channel. This invention proposes a wall-mounted integrated 3D endoscopic PIV probe for high-temperature flow field testing. This probe employs a single-hole integrated design, integrating a laser illumination channel and two imaging channels at a specific angle into a single body, supplemented by efficient internal circulation cooling and a concealed film purging system. The probe head adopts a wall-mounted design that perfectly matches the curvature of the inner wall of the device under test, requiring only a single probe hole for installation, and the probe end face remains flush with the flow channel wall after installation. While ensuring the structural integrity of the casing, this invention achieves low-interference, high-precision measurement of 3D velocity vectors within a high-temperature confined space.

[0008] The technical solution of this invention is:

[0009] A wall-mounted integrated three-dimensional endoscopic PIV probe for high-temperature flow field testing is characterized by: an integrated probe body (1), a left imaging channel (2), a laser emission channel (3), a right imaging channel (4), optical windows (5), (6), and (7), a spherical lens (8), a cylindrical lens (9), an objective lens group (10) and (11), a Littoral prism (12) and (13), a Hopkins cylindrical lens system (14) and (15), an eyepiece group (16) and (17), a purge channel (18), an air inlet (19), an air suction port (20), a water inlet channel (21), (22), (23), and (24), a drain outlet (25), (26), (27), and (28), an external connecting flange (29), (30), (31), and (32), an external laser interface (33), an external camera interface (34) and (35), an imaging camera (36) and (37), a laser (38), and a target measurement area (39). The integrated probe body (1) is the main support structure of the probe. It is cylindrical in shape, with a diameter of 10~100mm and a length of 100~500mm. The integrated probe body (1) is made of stainless steel or other high-temperature resistant alloys, and its surface is coated with a high-temperature resistant heat-insulating coating.

[0010] Furthermore, the integrated probe body (1) has three through optical channels arranged side by side along the axial direction, as well as functional channels for thermal protection and cleaning. Among them, the laser emission channel (3) is located at the center of the integrated probe body (1) with a diameter of 1~20mm, and the left imaging channel (2) and the right imaging channel (4) are symmetrically distributed on both sides of the laser emission channel (3) with a diameter of 1~20mm;

[0011] Furthermore, external connecting flanges (29), (30), (31), and (32) are fixed on the outer wall of the integrated probe body (1) to install and fix the entire probe to the mounting holes on the combustion chamber or casing wall; the front end of the integrated probe body (1) is designed with a concave arc that matches the inner wall of the device under test, so that after the probe is fixed, its head end face can remain flush with the inner wall surface, reducing interference to the flow field;

[0012] Furthermore, the laser emission channel (3) is used to transmit illumination laser. The external laser beam is emitted via the laser (38), enters the channel through the external laser interface (33) at the tail of the probe, and is expanded and focused by the internal cylindrical lens (9) and spherical lens (8) to form a sheet laser. Finally, it passes through the optical window (6) sealed at the center of the probe front end and exits to illuminate the target measurement area (39) located in front of the probe. The laser shaping optical elements in the laser emission channel (3) are not limited to the cylindrical lens (9) and spherical lens (8), but may also include collimating lenses, beam expander groups, Powell lenses, cylindrical lens groups, mirrors, prisms, graded refractive index lenses, fiber collimators, fiber couplers, sheet light shapers or combinations thereof; the external laser interface (33) can be directly connected to the free space laser optical path, or it can be connected to the laser (38) through optical fiber, fiber bundle, fiber connector or fiber collimation module;

[0013] Furthermore, the left imaging channel (2) and the right imaging channel (4) are used to transmit image signals. The front-end visual axes of these two channels, after passing through optical windows (5) and (7), point to the common target measurement area (39) and form a certain stereo angle (10°~60°). The tracer particle scattered light in the target measurement area (39) enters the imaging channel through the optical windows (5) and optical windows (7) on both sides of the probe front end, respectively.

[0014] Furthermore, the light entering the left imaging channel (2) and the right imaging channel (4) is first deflected by the Littoral prisms (12) and (13) to adapt to the observation requirements of the confined space and form the solid angle required for three-dimensional measurement. Then, it enters the objective lens group (10) and (11) at the front end for light collection and preliminary imaging. Subsequently, the image is transmitted with low loss in the slender tube through the Hopkins cylindrical lens system (14) and (15). Finally, it is exported through the eyepiece group (16) and (17) at the tail with adjustable focal length. The line-of-sight deflection element is not limited to a Littoral prism, but can also be a right-angle prism, a roof prism, a reflecting mirror, a wedge prism, an optical steering mirror group, a fiber optic image transfer module, or other optical elements capable of changing the direction of the imaging visual axis; the image transmission system is not limited to a Hopkins cylindrical lens system, but can also be a relay lens group, a gradient refractive index lens group, a rod lens system, a lens array, an imaging fiber bundle, a rigid endoscope image transfer system, a flexible endoscope image transfer system, or a combination thereof; the objective lens group (10), (11) and the eyepiece group (16), (17) can be a fixed focal length structure, or an adjustable focal length, adjustable aperture, or replaceable magnification structure;

[0015] Furthermore, external camera interfaces (34) and (35) are connected to the left imaging channel (2) and the right imaging channel (4) respectively, for docking with imaging cameras (36) and (37), thereby simultaneously acquiring particle images from two perspectives. A light-limiting structure can be set within the imaging channel, including an aperture, a light-blocking ring, a limiting hole, an extinction inner wall, or a combination thereof, for limiting stray light, controlling the field of view, improving imaging contrast, and reducing the impact of high-temperature wall radiation on particle image acquisition.

[0016] Furthermore, a cooling system is integrated inside the integrated probe body (1). The cooling system includes water inlet channels (21), (22), (23), (24) and drain outlets (25), (26), (27), (28). The water inlet channels (21), (22), (23), (24) have a diameter of 3~20mm, and their shells overlap with the inner wall of the integrated probe body (1), forming an integral design with the probe body (1), and have a certain bend at the probe head. The drain outlets (25), (26), (27), (28) have a diameter of 3~15mm;

[0017] Furthermore, the integrated probe body (1) incorporates a purging system. The purging system includes a purging channel (18), an air inlet (19), and an air intake (20). High-pressure gas is sprayed through this channel to the optical windows (5), (6), and (7) at the front end to prevent oil or particles from adhering and affecting the optical transmission performance. Purging can be performed before or during the experiment. The air inlet (19) and the air intake (20) can be interchanged to achieve a better purging effect. The diameter of the air inlet (19) and the air intake (20) is 3~10mm. The radial dimension of the purging channel (18) along the probe is 1~5mm, and the circumferential angle is 20°~60°.

[0018] Furthermore, the materials of the optical windows (5), (6), and (7) are preferably sapphire glass or other high-pressure and corrosion-resistant optical glass, which have the characteristics of high temperature resistance, high pressure resistance and particle erosion resistance, and are sealed and matched with the left imaging channel (2), laser emission channel (3), and right imaging channel (4) of the head of the integrated probe body (1).

[0019] Furthermore, the imaging cameras (36) and (37) are connected to the laser (38) through a synchronous control system. The dual-pulse laser illumination and the phase-locked triggering mode of the camera are used to acquire time-related particle image sequences in the target measurement area (39) and reconstruct the three-dimensional velocity vector field through a three-dimensional cross-correlation algorithm.

[0020] The beneficial effects of this invention are:

[0021] To address the limitations of traditional external PIV probes in high-temperature, high-pressure, and extremely compact space constraints for core components such as aero-engine turbines and combustion chambers, which suffer from difficulties in creating large windows, severe optical distortion due to curved windows, and significant interference from intrusive flow fields, lack of effective thermal protection, and limitation to two-dimensional measurements, a wall-mounted integrated three-dimensional endoscopic PIV probe with high-temperature thermal protection is proposed. This probe employs a single-hole integrated design with end-face wall-mounted fitting, integrating a laser illumination channel and two imaging channels at a specific angle into a single unit. Supplemented by internal circulation cooling and concealed film purging within a specific flow channel, it can be installed through a single micro-hole, with the probe head perfectly fitting the flow channel wall. While maintaining the structural integrity of the casing, it achieves low-interference, high-precision measurement of three-dimensional velocity vectors within a high-temperature confined space.

[0022] Beneficial effect 1:

[0023] The laser illumination path and the dual imaging path with a specific parallax angle are highly integrated into a single miniature probe body, requiring only a probe hole to be made in the device wall to probe the interior. There is no need to make large transparent windows and arrange optical paths on a large scale, which significantly reduces the impact on the test section wall and the overall structural stiffness of the blade cascade. At the same time, it can realize the accurate measurement of three-dimensional velocity vectors in extremely confined spaces such as the narrow flow passage of aero-engine turbines.

[0024] Benefit 2:

[0025] Compared to the traditional approach that requires inserting multiple single-function probes simultaneously to achieve the same three-dimensional measurement purpose, this device only requires small holes and flange sealing structures on the local wall surface, eliminating the need for multiple holes. Furthermore, the probe head is designed with a concave arc that matches the inner wall surface of the device being measured. After the probe is fixed, its head end face can remain flush with the inner wall surface, greatly reducing the obstruction effect on the airflow inside the flow channel, effectively reducing wake and shock wave interference, and ensuring that the measured flow field information truly reflects the original flow state inside the device.

[0026] Benefit 3:

[0027] After the laser beam is shaped inside the integrated probe, it is directly injected into the channel of the device under test through the optical window on the probe head. The particle scattered light is then guided from inside the channel by the camera's endoscopic probe to an external imaging camera, forming a compact "endoscopic illumination + endoscopic imaging" optical path. Compared with traditional external long optical path solutions, the integrated endoscopic design effectively reduces geometric distortion and scattering interference caused by multiple refractions and reflections, improves particle image quality and related calculation accuracy, and makes the obtained velocity field information more representative and targeted.

[0028] Beneficial effect four:

[0029] The probe integrates a pneumatic purging system, which directs high-pressure gas to the optical window surface at the probe head via an internal purging channel. The purging channel is completely embedded within the probe body, with no protruding nozzles or conduits at the probe head. This concealed flow channel design effectively removes oil and particles from the optical window surface using high-pressure gas, ensuring optical transmission performance, while avoiding additional shock waves or wake interference caused by additional purging structures, thus ensuring the authenticity of the measured flow field and the accuracy of the measurement.

[0030] Benefit 5:

[0031] The probe adopts an integrated design of cooling channel and housing. The water inlet channel has a specific bend at the probe head. This structure allows the cooling medium to provide impact cooling to the laser emission channel and two imaging channel areas at the probe head, specifically enhancing the cooling effect of the three optical channel areas at the probe head. At the same time, the integrated design ensures that the cooling channel housing and the probe body housing are tightly connected, enhancing the cooling effect of the entire probe outer wall surface. This effectively prevents the probe housing from deforming or the internal precision optical components from being damaged in high-temperature environments, significantly improving the reliability and lifespan of the probe when working in the high-temperature core area of ​​aero-engines.

[0032] Benefit 6:

[0033] The complex geometric coupling between the sheet light plane generated by the laser emission channel and the focal planes of the left and right imaging channels has been precisely calibrated and locked during the probe manufacturing and assembly stage. At the test site, only the mechanical installation of the probe and the connection of external cables are required to conduct the test. This completely avoids the time-consuming and challenging coupling adjustment of the laser sheet light and the dual-camera field of view within the confined and complex test bench space of an aero-engine, greatly simplifying the testing process of the 3D PIV system and significantly reducing the technical threshold and time cost of testing. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of an integrated PIV probe according to an embodiment of the present invention.

[0035] Figure 2 This is a top view of an integrated PIV probe according to an embodiment of the present invention.

[0036] Figure 3 This is a sectional view of section AA.

[0037] Figure 4 This is a sectional view of section BB.

[0038] Figure 5 This is a cross-sectional view of section CC.

[0039] Figure 6This is a sectional view of section DD.

[0040] Figure 7 This is a schematic diagram illustrating a specific implementation of an integrated PIV probe inside a turbine in an embodiment of the present invention.

[0041] Wherein: 1-Integrated probe body, 2-Left imaging channel, 3-Laser emission channel, 4-Right imaging channel, 5, 6, 7-Optical window, 8-Spherical lens, 9-Cylindrical lens, 10, 11-Objective lens group, 12, 13-Littoral prism, 14, 15-Hopkins cylindrical lens, 16, 17-Eyepiece group, 18-Purge channel, 19-Air inlet, 20-Air suction port, 21, 22, 23, 24-Water inlet channel, 25, 26, 27, 28-Drain outlet, 29, 30, 31, 32-External connection flange, 33-External laser interface, 34, 35-External camera interface, 36, 37-Imaging camera, 38-Laser, 39-Target measurement area. Detailed Implementation

[0042] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 1 , Figure 2 As shown in the figure, this embodiment introduces a wall-mounted integrated three-dimensional endoscopic PIV probe for high-temperature flow field testing, which mainly consists of an integrated probe body (1), a left imaging channel (2), a laser emission channel (3), a right imaging channel (4), optical windows (5), (6), (7), a spherical lens (8), a cylindrical lens (9), an objective lens group (10), (11), a Littoral prism (12), (13), a Hopkins cylindrical lens system (14), (15), an eyepiece group (16), (17), a purge channel (18), an air inlet (19), an air suction port (20), a water inlet channel (21), (22), (23), (24), a drain port (25), (26), (27), (28), an external connecting flange (29), (30), (31), (32), an external laser interface (33), and an external camera interface (34), (35). The feature is that the integrated probe body (1) is the main support structure of the probe, and its shape is cylindrical with a diameter of 40 mm and a length of 300 mm. The integrated probe body (1) is made of stainless steel and its surface is coated with a high-temperature resistant heat-insulating coating.

[0045] The relative positions and structures of the probe's internal optical channels, water inlet channels, and purging channels are as follows: Figure 3 As shown. The integrated probe body (1) integrates a laser emission channel (3), imaging channels (2), (4), water inlet channels (21), (22), (23), (24) and a purge channel (18). Among them, the laser emission channel (3) is located at the geometric center of the cross-section of the integrated probe body (1) and has a diameter of 8 mm. The left imaging channel (2) and the right imaging channel (4) are symmetrically distributed with the laser emission channel (3) as the center, close to the central axis of the probe, and have a diameter of 6 mm. The four water inlet channels (21), (22), (23), (24) are distributed on the upper and lower sides of the above optical channels. The four water inlet channels are arranged in a rectangular array around the center of the probe and have a diameter of 10 mm. The purge channel (18) is set in the shell of the integrated probe body (1). Its cross-section is an arc-shaped long groove structure extending along the circumference of the probe. The radial dimension of the arc-shaped long groove structure is 1 mm and the circumferential coverage is 20°.

[0046] The cross-section of the probe inlet pipe drain outlet is as follows Figure 4 As shown. The four drain outlets (25), (26), (27), and (28) are located in the central area of ​​the integrated probe body (1), interspersed between the optical channel and the water inlet channel, and symmetrically distributed around the central laser emission channel (3), with a diameter of 6 mm.

[0047] The probe imaging system, laser system, and purge system, as well as... Figure 5As shown. The laser emission system is located at the central axis of the probe, and the external laser interface (33) is connected to the laser emission channel (3). The laser beam enters from the bottom, passes through the cylindrical lens (9) and spherical lens (8) arranged in series inside the channel, and after being shaped and focused by the lens group, it forms a sheet light source that passes through the central optical window (6) at the top and is projected into the flow field to be measured. The imaging system includes two symmetrical optical paths, which are arranged on both sides of the laser channel. The front ends of the left imaging channel (2) and the right imaging channel (4) are respectively equipped with optical windows (5) and (7), objective lens groups (10) and (11), and Littoral prisms (12) and (13). Scattered light from the flow field enters through the window, is first refracted by Littoral prisms (12) and (13), then collected and initially imaged by objective lens groups (10) and (11), and then transmitted downwards along the long tube through the Hopkins cylindrical lens system (14) and (15) composed of multiple lens groups. Finally, the output is adjusted by the eyepiece group (16) and (17) at the bottom, and docked with the imaging camera through the external camera interface (34) and (35). The purging system is mainly composed of a longitudinally continuous purging channel (18). High-pressure clean gas enters through the air inlet (19) located at the bottom of the probe, is transported to the probe head along the purging channel (18), and is ejected from the nozzles around the optical window to achieve the purging cleaning effect. The gas is then sucked out through the suction port (20). The diameter of the air inlet (19) and the suction port (20) is 3 mm.

[0048] The probe cooling system is as follows Figure 6 As shown. The water inlet channels (21), (22), (23), and (24) run axially through the entire integrated probe body (1), and their outer walls overlap with the inner walls of the probe body's outer shell, adopting an integrated structural design. This design not only enhances the overall structural rigidity of the probe but also allows the cooling water to directly and effectively cool the outer wall of the probe. In the probe head area, the water inlet channels (21), (22), (23), and (24) are designed with a significant inward bend. This bend guides the cooling medium to change its flow direction, enabling it to directly impact and cool the central area at the top of the probe, specifically enhancing the cooling effect on the head areas of the laser emission channel (3) and the imaging channels (2) and (4) on both sides.

[0049] The specific implementation scheme of this probe inside the turbine is as follows: Figure 7As shown. The integrated probe body (1) penetrates the single probe hole reserved on the turbine casing wall and extends into the flow channel. It is rigidly fixed to the casing wall and hermetically sealed using external connecting flanges (29), (30), (31), and (32). Before the experiment, the air inlet (19) and air intake (20) are connected to the external air source system to clean the optical windows (5), (6), and (7) on the probe head. The external laser interface (33) at the tail of the probe is connected to the laser (38) through the optical guide arm. The external camera interfaces (34) and (35) are connected to two imaging cameras (36) and (37) respectively through fiber bundles. The water inlet channels (21), (22), (23), and (24) are connected to the cooling water source system. During the test, the laser beam is projected through the probe to form a sheet-like target measurement area (39) that cuts into the main flow direction of the turbine at the front end. When the tracer particles pass through the light sheet with the mainstream, they are scattered. Under the phase-locking trigger of the synchronous controller, the two imaging cameras (36) and (37) synchronously acquire the particle image sequence through the internal optical path of the probe. Finally, the three-dimensional cross-correlation algorithm is combined to solve the image and reconstruct a high-precision three-dimensional velocity vector field in the confined space.

[0050] This invention introduces a wall-mounted integrated three-dimensional endoscopic PIV probe for high-temperature flow field testing. It employs a highly integrated design of laser illumination and dual-view imaging optical paths, encapsulating two imaging channels and a laser channel within a single probe body. Thermal protection and window self-cleaning are achieved through an integrated cooling circuit and pneumatic purging system within the probe. When measuring flow fields in confined spaces such as aero-engine turbines, this probe does not require large observation windows or multiple probe holes; it can operate simply by insertion through a single hole in the casing wall. The probe head adheres to the inner wall of the casing, thus enabling accurate measurement of the three-dimensional velocity vector of the internal flow field while ensuring the structural integrity of the equipment and without interfering with the original flow field.

Claims

1. A wall-mounted integrated three-dimensional endoscopic PIV probe for high-temperature flow field testing, characterized in that: The integrated probe body (1), left imaging channel (2), laser emission channel (3), right imaging channel (4), optical windows (5), (6), (7), spherical lens (8), cylindrical lens (9), objective lens group (10), (11), Littoral prism (12), (13), Hopkins cylindrical lens system (14), (15), eyepiece group (16), (17), purge channel (18), air inlet (19), air intake (20), water inlet channel (21), (22), (23), (24), drain (25), (26), (27), (28), external connection flange (29), (30), (31), (32), external laser interface (33), external camera interface (34), (35), imaging camera (36), (37), laser (38) and target measurement area (39). The integrated probe body (1) is the main support structure of the probe. It is cylindrical in shape, with a diameter of 10~100mm and a length of 100~500mm. The integrated probe body (1) is made of stainless steel or other high-temperature resistant alloys, and its surface is coated with a high-temperature resistant heat-insulating coating. Furthermore, the integrated probe body (1) has three through optical channels arranged side by side along the axial direction, as well as functional channels for thermal protection and cleaning. Among them, the laser emission channel (3) is located at the center of the integrated probe body (1) with a diameter of 1~20mm. The left imaging channel (2) and the right imaging channel (4) are symmetrically distributed on both sides of the laser emission channel (3) with a diameter of 1~20mm. Furthermore, external connecting flanges (29), (30), (31), and (32) are fixed on the outer wall of the integrated probe body (1) to install and fix the entire probe to the mounting holes on the combustion chamber or casing wall; the front end of the integrated probe body (1) is designed with a concave arc that matches the inner wall of the device under test, so that after the probe is fixed, its head end face can remain flush with the inner wall surface, reducing interference to the flow field; Furthermore, the laser emission channel (3) is used to transmit illumination laser. The external laser beam is emitted via the laser (38), enters the channel through the external laser interface (33) at the tail of the probe, and is expanded and focused by the internal cylindrical lens (9) and spherical lens (8) to form a sheet laser. Finally, it passes through the optical window (6) sealed at the center of the probe front end and exits to illuminate the target measurement area (39) located in front of the probe. The laser shaping optical elements in the laser emission channel (3) are not limited to the cylindrical lens (9) and spherical lens (8), but may also include collimating lenses, beam expander groups, Powell lenses, cylindrical lens groups, mirrors, prisms, graded refractive index lenses, fiber collimators, fiber couplers, sheet light shapers or combinations thereof; the external laser interface (33) can be directly connected to the free space laser optical path, or it can be connected to the laser (38) through optical fiber, fiber bundle, fiber connector or fiber collimation module; Furthermore, the left imaging channel (2) and the right imaging channel (4) are used to transmit image signals. The front-end visual axes of these two channels, after passing through optical windows (5) and (7), point to the common target measurement area (39) and form a certain stereo angle (10°~60°). The tracer particle scattered light in the target measurement area (39) enters the imaging channel through the optical windows (5) and optical windows (7) on both sides of the probe front end, respectively. Furthermore, the light entering the left imaging channel (2) and the right imaging channel (4) is first deflected by the Littoral prisms (12) and (13) to adapt to the observation requirements of the confined space and form the solid angle required for three-dimensional measurement. Then, it enters the objective lens group (10) and (11) at the front end for light collection and preliminary imaging. Subsequently, the image is transmitted with low loss in the slender tube through the Hopkins cylindrical lens system (14) and (15). Finally, it is exported through the eyepiece group (16) and (17) at the tail with adjustable focal length. The line-of-sight deflection element is not limited to a Littoral prism, but can also be a right-angle prism, a roof prism, a reflecting mirror, a wedge prism, an optical steering mirror group, a fiber optic image transfer module, or other optical elements capable of changing the direction of the imaging visual axis; the image transmission system is not limited to a Hopkins cylindrical lens system, but can also be a relay lens group, a gradient refractive index lens group, a rod lens system, a lens array, an imaging fiber bundle, a rigid endoscope image transfer system, a flexible endoscope image transfer system, or a combination thereof; the objective lens group (10), (11) and the eyepiece group (16), (17) can be a fixed focal length structure, or an adjustable focal length, adjustable aperture, or replaceable magnification structure; Furthermore, external camera interfaces (34) and (35) are connected to the left imaging channel (2) and the right imaging channel (4) respectively, for docking with imaging cameras (36) and (37), thereby simultaneously acquiring particle images from two perspectives. A light-limiting structure can be set within the imaging channel, including an aperture, a light-blocking ring, a limiting hole, an extinction inner wall, or a combination thereof, for limiting stray light, controlling the field of view, improving imaging contrast, and reducing the impact of high-temperature wall radiation on particle image acquisition. Furthermore, a cooling system is integrated inside the integrated probe body (1). The cooling system includes water inlet channels (21), (22), (23), (24) and drain outlets (25), (26), (27), (28). The water inlet channels (21), (22), (23), (24) have a diameter of 3~20mm, and their shells overlap with the inner wall of the integrated probe body (1), forming an integral design with the probe body (1), and have a certain bend at the probe head. The drain outlets (25), (26), (27), (28) have a diameter of 3~15mm; Furthermore, the integrated probe body (1) incorporates a purging system. The purging system includes a purging channel (18), an air inlet (19), and an air intake (20). High-pressure gas is sprayed through this channel to the optical windows (5), (6), and (7) at the front end to prevent oil or particles from adhering and affecting the optical transmission performance. Purging can be performed before or during the experiment. The air inlet (19) and the air intake (20) can be interchanged to achieve a better purging effect. The diameter of the air inlet (19) and the air intake (20) is 3~10mm. The radial dimension of the purging channel (18) along the probe is 1~5mm, and the circumferential angle is covered by 20°~60°. Furthermore, the materials of the optical windows (5), (6), and (7) are preferably sapphire glass or other high-pressure and corrosion-resistant optical glass, which have the characteristics of high temperature resistance, high pressure resistance and particle erosion resistance, and are sealed and matched with the left imaging channel (2), laser emission channel (3), and right imaging channel (4) of the head of the integrated probe body (1). Furthermore, the imaging cameras (36) and (37) are connected to the laser (38) through a synchronous control system. The dual-pulse laser illumination and the phase-locked triggering mode of the camera are used to acquire time-related particle image sequences in the target measurement area (39) and reconstruct the three-dimensional velocity vector field through a three-dimensional cross-correlation algorithm.

Images