Compressor blade integrated laser camera double-endoscopic PIV flow field measuring device

Abstract

The invention belongs to the technical field of gas compressor internal flow field testing and optical measurement, and relates to a gas compressor blade integrated laser camera double-endoscopic PIV flow field measuring device. The device comprises a laser endoscopic probe, a camera endoscopic probe, an optical window, a gas compressor stator blade, a gas compressor rotor blade, a casing, a hub, a light guide arm, a laser, an imaging camera and the like, a cavity is prefabricated in a blade body of the stator blade, and the high-pressure-resistant optical window is arranged on the outer surface of the blade; only a small-size optical interface matched with the outer diameter of an endoscopic probe is formed in a cartridge receiver, and laser sheet light and an imaging view field are led into an interstage channel of a gas compressor in an endoscopic mode. Tracer particles are uniformly scattered at an inlet of a gas compressor, a measurement plane is formed at an inlet, an outlet and an interstage area of a rotor by using a laser endoscopic probe, particle scattered light in a target measurement area is led out to an imaging camera outside a casing by using a camera endoscopic probe, and synchronous acquisition is realized by combining a rotating speed signal and laser triggering; and thus, high-Mach-number internal velocity field distribution of the multi-stage gas compressor is obtained. The device has the advantages of being small in case change, small in original flow field disturbance, suitable for narrow space high Mach number working conditions, capable of being expanded to three-dimensional PIV measurement and the like, and high-temporal-spatial-resolution experimental data can be provided for compressor rotation stall, surge and loss mechanism research.

Description

Technical Field

[0001] This invention belongs to the field of compressor flow field testing and optical measurement technology, specifically relating to a compressor blade integrated laser camera dual-endoscopic PIV flow field measurement device, which is suitable for measuring the airflow velocity field distribution in the compressor inlet and outlet, interstage and rotor channels under high Mach number, strong three-dimensional effect and confined space conditions. Background Technology

[0002] Currently, the measurement of the internal flow field of compressors still mainly relies on contact methods such as porous aerodynamic probes, wall pressure arrays, and hot wires. Although these methods can obtain overall performance and local parameters, they significantly disturb the original flow field and can only provide information from a limited number of measurement points, making it difficult to fully reveal typical unsteady flow characteristics such as compressor rotating stall, surge, and static rotor interference. Particle Image Velocimetry (PIV), as a non-contact, transient, and full-field measurement method, has been gradually introduced into compressor testing. However, most existing schemes rely on opening large-size optical windows on the casing and using external lasers and cameras for illumination and imaging. Due to limitations in installation space, available viewing angle, and refractive distortion, the laser beam and camera line of sight cannot penetrate deeply into the multi-stage channels, especially the rotor inlet, outlet, and narrow interstage areas, where the measurable range is limited. The flow field in key areas such as near-wall, endwall, and blade tip is difficult to fully cover and accurately reconstruct.

[0003] Publication number CN120294360A discloses an endoscopic PIV (Portable Airflow Measurement) testing device and method for the internal flow field of turbomachinery. An endoscope is inserted into the impeller casing and combined with a PIV test camera and a sheet light source to capture images of the internal flow field of the impeller. This PIV test focuses on single-camera endoscopic imaging. The probe arrangement can cause some obstruction and disturbance to the channel, altering the original wake and corner flow patterns, and affecting the identification of the true flow structure. Therefore, the existing technology lacks a compact, blade-integrated laser camera dual-endoscopic PIV flow field measurement device suitable for multi-stage compressor stationary rotor structures, capable of simultaneously introducing laser sheet light and imaging field of view within a limited installation space. This device would achieve high-precision, non-contact, full-field measurement of the airflow velocity field inside the compressor rotor inlet and outlet and interstage channels without disturbing the original flow field. Summary of the Invention

[0004] The technical problem this invention aims to solve is: addressing the difficulty in achieving non-contact full-field measurement within high Mach numbers and multi-stage blade passages due to limited installation space and insufficient field of view in compressor internal flow field testing. This invention proposes an integrated laser camera dual-endoscope PIV flow field measurement device for compressor blades. By introducing both the laser endoscope probe and the camera endoscope probe into the stator blade, non-contact full-field measurement of the airflow velocity field at the rotor inlet and outlet, interstages, and rotor passages of high Mach numbers and multi-stage compressors is achieved. This provides high spatiotemporal resolution experimental data for the study of compressor rotating stall, surge, and loss mechanisms.

[0005] The technical solution of this invention is:

[0006] A compressor blade integrated laser camera dual-endoscope PIV flow field measurement device is characterized by comprising a laser endoscope probe (1), a camera endoscope probe (2), a compressor stator blade (3), an optical window (4), a compressor rotor blade (5), a target measurement area (6), a casing (7), an imaging camera (8), a laser (9), a light guide arm (10), and a hub (11). The casing (7) is provided with a small-sized optical interface that matches the outer diameter of the laser endoscope probe (1) and the camera endoscope probe (2), and with the help of a flange and sealing structure, the laser endoscope probe (1) and the camera endoscope probe (2) are mounted on the compressor casing (7). The laser (9) is connected to the laser endoscope probe (1) through the light guide arm (10). The compressor stator blades (3) are provided with one or more rows of optical windows (4) along the blade height direction. The laser endoscope probe (1) extends into the interior of the compressor stator blades (3) through the optical interface of the casing (7) and draws out the laser through the optical window (4). A laser sheet with a certain thickness and width is formed in the target measurement area (6) in the compressor channel. Tracer particles are evenly spread at the compressor inlet so that the tracer particles pass through the target measurement area (6) with the airflow. The camera endoscope probe (2) is inserted into the compressor through another optical interface of the compressor casing (7) and transmits the scattered light of the tracer particles in the target measurement area (6) to the imaging camera (8) arranged outside the casing to realize the PIV measurement of the airflow velocity field inside the compressor.

[0007] Furthermore, the optical window (4) is uniformly opened on the outer surface of the compressor stator blade (3) with equal diameter and equal spacing along the blade height direction. The material of the optical window (4) is sapphire glass or other high-pressure resistant and corrosion resistant optical glass. The laser endoscope probe (1) and the camera endoscope probe (2) can move up and down along the blade height direction inside the compressor stator blade (3) to adapt to the measurement needs of different height positions.

[0008] Furthermore, the diameter of the optical window (4) is 1mm to 8mm, the spacing between two adjacent windows is 2mm to 40mm, and the outer surface of the window maintains a smooth transition with the outline of the leading edge or sidewall of the compressor stator blade (3) to reduce interference with the original channel flow field.

[0009] Furthermore, the imaging camera (8), the compressor rotor speed signal, and the laser (9) are all connected to the synchronous control system, and particle images in the target measurement area (6) are acquired at different rotor angle positions through phase-locked triggering.

[0010] Furthermore, the laser endoscope probe (1) and the camera endoscope probe (2) are located inside the same compressor stator blade (3), or inside two adjacent compressor stator blades (3);

[0011] Furthermore, the laser endoscope probe (1) can be placed inside the compressor stator blade (3) one stage before the compressor rotor blade (5) to observe the flow field in the front section of the compressor rotor blade (5) from the upstream direction, thereby realizing the measurement of the velocity field of the compressor rotor inlet section.

[0012] Furthermore, the diameter of the laser endoscope probe (1) and the camera endoscope probe (2) is 1mm to 8mm and the length is 80mm to 500mm; the device can be equipped with two or more imaging cameras (8), with a certain angle between their optical axes, to simultaneously capture images of the target measurement area (6) from different perspectives, thereby realizing the three-dimensional PIV measurement of the internal flow field of the compressor.

[0013] The beneficial effects of this invention are:

[0014] To address the limitations of existing compressor internal flow field measurements, such as restricted optical channels and difficulties in achieving non-contact full-field measurements at high Mach numbers and in multi-stage channels, a dual-endoscope PIV flow field measurement device integrating a laser camera and a compressor blade is proposed. By integrating the laser endoscope probe and the camera endoscope probe inside the stator blade and creating a high-intensity optical window on the outer surface of the blade, the laser beam and imaging field of view are directly introduced into the compressor channel, enabling precise measurement of the velocity field at the rotor inlet, outlet, and interstage channels.

[0015] Beneficial effect 1:

[0016] Only a small optical interface matching the outer diameter of the endoscope probe needs to be opened on the casing to complete the laser incident and imaging optical path arrangement. There is no need to process a large-area observation window, which greatly reduces the adverse effects on the overall structure, rigidity and sealing performance of the casing. It helps to maintain the original aerodynamic shape and flow field characteristics inside the compressor, and the measurement results are closer to the actual working state.

[0017] Benefit 2:

[0018] Multiple rows of optical windows are arranged along the stator blade height direction. Combined with the vertical movement of laser endoscope and camera endoscope probes inside the blade, measurement planes can be arranged at different blade heights and in different interstage channels, enabling regional measurements of the rotor inlet, outlet, and interstage flow fields. Compared to the traditional PIV arrangement that only observes from a single plane outside the casing, this invention can obtain more complete velocity field information, and is particularly beneficial for capturing typical flow structures such as endwall secondary flow, corner separation, and tip leakage flow.

[0019] Benefit 3:

[0020] The optical window is made of sapphire or other high-pressure and erosion-resistant optical glass, and its shape smoothly transitions to the leading edge or sidewall of the stator blade. On the one hand, it effectively protects the end of the endoscope probe and internal optical components from particle erosion and oil mist contamination. On the other hand, it reduces the additional disturbance of near-wall flow caused by geometrical abrupt changes, which is conducive to obtaining particle images with high signal-to-noise ratio and low distortion.

[0021] Beneficial effect four:

[0022] After the laser beam is shaped inside the stator blade, it is directly incident into the blade passage as a sheet beam. The imaging beam is transmitted to the imaging camera outside the casing via an endoscope probe. Compared with traditional external PIV systems with long optical paths, multiple refractions, or transmission through large windows, this invention significantly shortens the optical path, reduces refractive interfaces and reflective surfaces, and lowers geometric distortions and optical errors caused by density gradients, refractive index changes, and wall reflections. It also improves the spatial resolution and inversion accuracy of the velocity vector within the measurement field of view, making it suitable for transonic and even locally supersonic compressor passages.

[0023] Benefit 5:

[0024] The imaging camera is synchronously controlled with the compressor rotor speed signal and the laser, enabling phase-locked acquisition of the same target measurement area at different rotor angle positions. When three-dimensional measurements are required, two or more imaging cameras can be deployed in conjunction with the camera's endoscopic probe to form multi-view stereoscopic observation conditions, achieving high-precision reconstruction of the three-dimensional velocity vector field. This allows for characterization of the spatiotemporal evolution of rotating stall structures, surge precursors, and shock-boundary layer disturbances, and can also provide high-quality experimental data support for the study of compressor loss mechanisms and stability boundaries. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the specific implementation of the integrated laser camera dual-endoscopic PIV inside the compressor of the present invention.

[0026] Figure 2 This is a schematic diagram showing the interaction between the laser endoscope probe, the camera endoscope probe, the compressor stator blades, and the optical window.

[0027] Figure 3 A schematic diagram showing the location of the optical window on the compressor stator blade.

[0028] Figure 4 This is a top view showing the relative position of the measurement area of ​​the laser endoscope probe and camera endoscope probe within the compressor channel to the rotor blades.

[0029] Figure 5 This is a front view showing the relative positions of the laser endoscope probe, the camera endoscope probe, and the compressor rotor blades.

[0030] Wherein: 1-Laser endoscope probe, 2-Camera endoscope probe, 3-Compressor stator blade, 4-Optical window, 5-Compressor rotor blade, 6-Target measurement area, 7-Casing, 8-Imaging camera, 9-Laser, 10-Light guide arm, 11-Hub. Detailed Implementation

[0031] 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.

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] Example 1:

[0034] like Figures 1-5The diagram shows an integrated laser camera dual-endoscope PIV flow field measurement device for compressor blades, used to measure the velocity field distribution inside a compressor. It includes a laser endoscope probe (1), a camera endoscope probe (2), a compressor stator blade (3), an optical window (4), a compressor rotor blade (5), a target measurement area (6), a casing (7), an imaging camera (8), a laser (9), a light guide arm (10), and a hub (11). The laser endoscope probe (1) and the camera endoscope probe (2) are arranged inside the compressor stator blade (3) one stage after the compressor rotor blade (5), observing the flow field of the trailing edge of the compressor rotor blade (5) and its downstream region from the downstream direction, thus realizing the velocity field measurement of the compressor rotor outlet section. A small-sized optical interface matching the outer diameter of the laser endoscope probe (1) and the camera endoscope probe (2) is provided on the casing (7). With the help of flanges and sealing structures, the laser endoscope probe (1) and the camera endoscope probe (2) are mounted on the casing (7). The laser (9) is connected to the laser endoscope probe (1) via the light guide arm (10). Two rows of optical windows (4) are opened along the blade height direction of the compressor stator blade (3). The laser endoscope probe (1) extends into the interior of the stator blade (3) through the optical interface of the casing (7) and extracts the laser light through the optical window (4), forming a laser sheet with a certain thickness and width in the target measurement area (6) within the compressor channel. By adjusting the output energy and pulse interval of the laser (9) and cooperating with the optical element at the front end of the laser endoscope probe (1), the specific position and thickness of the laser sheet light in the channel are adjusted so that the target measurement area (6) covers the trailing edge and the area near the outlet of the compressor rotor blade (5). Tracer particles are uniformly seeded at the compressor inlet so that the tracer particles pass through the target measurement area (6) with the airflow. The camera endoscope probe (2) is inserted into the compressor from another optical interface of the casing (7), and its field of view is pointed to the target measurement area (6). The area is photographed synchronously, and the particle scattered light is transmitted to the imaging camera (8) outside the casing to realize the PIV measurement of the airflow velocity field in the compressor rotor outlet area.

[0035] The optical window (4) is preferably made of sapphire glass and is uniformly opened at the leading edge of the stator blade (3) along the blade height direction of the compressor stator blade (3) with equal diameter and equal spacing. The optical window (4) is preferably 2 mm in diameter and 10 mm apart. The optical window (4) and the outer surface of the compressor stator blade (3) are smoothly transitioned to reduce interference with the original channel flow field. The diameter of the laser endoscope probe (1) and the camera endoscope probe (2) is 1.6 mm and the length is 350 mm. The rear end of the camera endoscope probe (2) is connected to the imaging camera (8) arranged outside the casing (7) through an optical interface. The imaging camera (8) is a high-speed CMOS camera. The laser (9), the imaging camera (8) and the compressor rotor speed signal are connected to the synchronous control system. The laser double pulse and camera exposure are triggered by phase locking. The double-frame images of the tracer particles in the target measurement area (6) are collected at different rotor angle positions to obtain the flow field information of the compressor rotor blade (5) outlet area and the main channel.

[0036] Example 2:

[0037] The laser endoscope probe (1) and the camera endoscope probe (2) are arranged inside the compressor stator blade (3) one stage before the compressor rotor blade (5) to observe the flow field of the leading edge and front section of the compressor rotor blade (5) from the upstream direction, thereby realizing the velocity field measurement of the compressor rotor inlet section. A small-sized optical interface matching the outer diameter of the laser endoscope probe (1) and the camera endoscope probe (2) is opened on the casing (7). With the help of the flange and sealing structure, the laser endoscope probe (1) and the camera endoscope probe (2) are installed on the casing (7). The laser (9) is connected to the laser endoscope probe (1) through the light guide arm (10). Two rows of optical windows (4) are opened along the blade height direction of the compressor stator blade (3). The laser endoscope probe (1) extends into the stator blade (3) through the optical interface of the casing (7) and draws out the laser through the optical window (4) to form a laser sheet with a certain thickness and width in the target measurement area (6) in the compressor channel. By adjusting the output energy and pulse interval of the laser (9), and in conjunction with the optical elements at the front end of the laser endoscope probe (1), the specific position and thickness of the laser sheet light in the channel are adjusted so that the target measurement area (6) covers the trailing edge and the area near the outlet of the compressor rotor blade (5). Tracer particles are uniformly seeded at the compressor inlet so that the tracer particles pass through the target measurement area (6) with the airflow. The camera endoscope probe (2) is inserted into the compressor from another optical interface of the casing (7), with its field of view pointing to the target measurement area (6), and synchronously photographs the area. The particle scattered light is transmitted to the imaging camera (8) outside the casing to realize the PIV measurement of the airflow velocity field in the compressor rotor outlet area.

[0038] In this embodiment, the optical window (4) is preferably made of sapphire glass and is uniformly arranged at the trailing edge of the compressor stator blade (3) with equal diameter and equal spacing along the blade height direction. The laser endoscope probe (1) and the camera endoscope probe (2) can move up and down along the blade height direction inside the stator blade (3) to adapt to the measurement requirements of different height sections such as near the hub, mid-span, and near the casing. The diameter of the optical window (4) is selected as 2 mm, the spacing between adjacent windows is 10 mm, and the outer surface of the optical window (4) maintains a smooth transition with the outer profile of the compressor stator blade (3) to reduce additional disturbance to the inlet flow field. The diameter of the laser endoscope probe (1) and the camera endoscope probe (2) is selected as 1.6 mm, and the length is 350 mm. The rear end of the camera endoscope probe (2) is connected to the imaging camera (8) arranged outside the casing (7) through an optical interface. The imaging camera (8) is a high-speed CMOS camera. The laser (9), imaging camera (8), and compressor rotor speed signal are connected to the synchronous control system. The laser double pulse and camera exposure are triggered by phase locking. The tracer particles in the target measurement area (6) are acquired at different rotor angle positions, thereby obtaining the spatiotemporal distribution characteristics of the unsteady flow field in the inlet area and main channel of the compressor rotor blade (5). This provides experimental data support for the analysis of inlet distortion, angle of attack change, and precursors of rotating stall.

[0039] In this embodiment of the invention, by compactly integrating the laser endoscope probe (1), the camera endoscope probe (2), and the compressor stator blade (3), the velocity field measurement of the key area inside the compressor can be realized in a high-speed, confined space environment without the need for large-size openings in the casing (7). This significantly reduces the impact on the casing structure and the original flow field, and improves the applicability and accuracy of the flow field measurement.

Claims

1. The technical solution of the present invention is: a compressor blade integrated laser camera dual-endoscopic PIV flow field measurement device, characterized in that: The compressor includes a laser endoscope probe (1), a camera endoscope probe (2), compressor stator blades (3), an optical window (4), compressor rotor blades (5), a target measurement area (6), a housing (7), an imaging camera (8), a laser (9), a light guide arm (10), and a hub (11). The housing (7) is provided with a small-sized optical interface that matches the outer diameter of the laser endoscope probe (1) and the camera endoscope probe (2). With the help of flanges and sealing structures, the laser endoscope probe (1) and the camera endoscope probe (2) are installed on the compressor housing (7). The laser (9) is connected to the laser endoscope probe (1) through the light guide arm (10). The compressor stator blades (3) are positioned along the blade height direction. One or more rows of optical windows (4) are opened, and the laser endoscope probe (1) is inserted into the compressor stator blade (3) through the optical interface of the casing (7). The laser is drawn out through the optical window (4) to form a laser sheet with a certain thickness and width in the target measurement area (6) in the compressor channel. Tracer particles are evenly spread in the compressor inlet so that the tracer particles pass through the target measurement area (6) with the airflow. The camera endoscope probe (2) is inserted into the compressor through another optical interface of the compressor casing (7) to transmit the scattered light of the tracer particles in the target measurement area (6) to the imaging camera (8) arranged outside the casing, so as to realize the PIV measurement of the airflow velocity field inside the compressor. Furthermore, the optical window (4) is uniformly opened on the outer surface of the compressor stator blade (3) with equal diameter and equal spacing along the blade height direction. The material of the optical window (4) is sapphire glass or other high-pressure resistant and corrosion resistant optical glass. The laser endoscope probe (1) and the camera endoscope probe (2) can move up and down along the blade height direction inside the compressor stator blade (3) to adapt to the measurement needs of different height positions. Furthermore, the diameter of the optical window (4) is 1mm to 8mm, the spacing between two adjacent windows is 2mm to 40mm, and the outer surface of the window maintains a smooth transition with the outline of the leading edge or sidewall of the compressor stator blade (3) to reduce interference with the original channel flow field. Furthermore, the imaging camera (8), the compressor rotor speed signal, and the laser (9) are all connected to the synchronous control system, and particle images in the target measurement area (6) are acquired at different rotor angle positions through phase-locked triggering. Furthermore, the laser endoscope probe (1) and the camera endoscope probe (2) are located inside the same compressor stator blade (3), or inside two adjacent compressor stator blades (3); Furthermore, the laser endoscope probe (1) can be placed inside the compressor stator blade (3) one stage before the compressor rotor blade (5) to observe the flow field in the front section of the compressor rotor blade (5) from the upstream direction, thereby realizing the measurement of the velocity field of the compressor rotor inlet section. Furthermore, the diameter of the laser endoscope probe (1) and the camera endoscope probe (2) is 1mm to 8mm and the length is 80mm to 500mm; the device can be equipped with two or more imaging cameras (8), with a certain angle between their optical axes, to simultaneously capture images of the target measurement area (6) from different perspectives, thereby realizing the three-dimensional PIV measurement of the internal flow field of the compressor.

Images