Turbine blade integrated laser endoscopic PIV flow field measuring device

Abstract

The invention belongs to the technical field of turbine internal flow field testing and optical measurement, and discloses a turbine blade integrated laser endoscopic PIV flow field measuring device which is suitable for measuring airflow velocity field distribution in a turbine inlet, a turbine outlet, an interstage and a rotor channel under high-speed and space-limited working conditions. The invention relates to a laser endoscopic probe, which is characterized by comprising an endoscopic probe, a turbine stator blade, an optical window, a turbine rotor blade, a target measurement area, a turbine case, an imaging camera, a laser and a light guide arm, a small-size optical interface is arranged on the turbine case, and the laser endoscopic probe and the turbine stator blade with the optical window are compactly integrated; laser sheet light is introduced into a turbine channel, and fine measurement of velocity fields in a turbine inlet and outlet, inter-stage and a rotor channel is realized in cooperation with an external camera under high-speed and space-limited working conditions. Compared with a traditional PIV arrangement depending on a large-size observation window and an external optical system, the method has the advantages of being small in case change, small in original flow field disturbance, large in measurable area range and the like, and the measurement precision and engineering applicability of a complex flow structure in a turbine can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of turbine internal flow field testing and optical measurement technology, specifically relating to an integrated laser endoscopic PIV flow field measurement device for turbine blades, which is suitable for measuring the airflow velocity field distribution in turbine inlet and outlet, interstage and rotor channels under high-speed and space-constrained conditions. Background Technology

[0002] The measurement of the airflow velocity field inside turbines currently relies mainly on traditional contact flow field testing techniques such as aerodynamic probes, wall pressure arrays, and hot wire / hot film. These contact measurements are highly susceptible to flow field interference and can only obtain local point information, making them unsuitable for the demanding requirements of fine-grained velocity field measurement inside turbines. Particle Image Velocimetry (PIV), as a non-contact, transient, full-field measurement method, acquires the velocity vector field of airflow on a plane by tracking particles as they move with the fluid and performing related calculations on their displacement. Conventional PIV systems generally face severe occlusion problems when measuring critical near-wall regions such as the trailing edge, root, and tip of turbine rotor blades. The rotor blade body, the preceding and following stage stator blades, and the hub and casing structures easily obstruct the laser beam and camera line of sight, resulting in only localized areas within the blade passage being effectively illuminated and imaged. In addition, the turbine's internal space is small and the casing is closed. Due to the limitations of the test section's viewing angle and optical path arrangement, the laser sheet light cannot penetrate deep into the blade root corner area and the blade tip leakage flow channel. This results in the measurable area being limited to the mid-span section area, making it difficult to obtain complete velocity field information covering complex flow structures such as trailing edge shear layer, endwall secondary flow, and blade tip leakage vortex.

[0003] CN120294360A discloses an endoscopic PIV (Picture-in-Video) 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 sheet light source to capture images of the internal flow field of the impeller. However, the endoscope itself can interfere with the original flow field. On the one hand, the endoscope occupies part of the channel cross-sectional area, increasing the local blockage rate and altering the velocity distribution in the near-wall region, potentially inducing boundary layer thickening, local separation, or enhanced secondary flow. On the other hand, when measuring the wake region of turbomachinery, the turbulence from the support rods can alter the original wake and corner flow patterns, thus affecting the identification of the actual flow structure. Furthermore, if the endoscope is improperly sized or its insertion position is not properly arranged, its interference effect will be further amplified, weakening the reliability of the measurement results in numerical simulation verification and mechanism analysis.

[0004] Therefore, existing technologies lack a compact PIV measurement device suitable for the confined space inside a turbine, capable of precisely measuring the airflow velocity field distribution within the turbine passage, between stages, and inlet / outlet regions of the rotor. To address this, an integrated laser endoscope PIV flow field measurement device for turbine blades is proposed. By cooperating with the endoscope probe in the turbine stator blade, laser light is introduced from inside the blade into the turbine passage, achieving internal measurement with minimal disturbance to the original flow field. The endoscope probe can be positioned within the stator blade preceding the turbine rotor blade, measuring the velocity field distribution near the rotor leading edge from the upstream direction. Alternatively, it can be positioned within the stator blade following the rotor blade, measuring the velocity field distribution near the rotor trailing edge from the downstream direction, thus enabling precise measurement of the airflow velocity field within the turbine inlet / outlet, between stages, and rotor passage. Summary of the Invention

[0005] The technical problem this invention aims to solve is: addressing the difficulties in optical path arrangement and the challenge of accurately acquiring the velocity field distribution within the turbine inlet / outlet, interstage, and rotor channels in existing turbine internal PIV testing, the invention proposes an integrated laser endoscopic PIV flow field measurement device for turbine blades. Compared to traditional PIVs, it requires minimal modification to the casing, features a compact structure, good optical path stability, and a wide measurable area, enabling precise measurement of the velocity field within the turbine inlet / outlet, interstage, and rotor channels at high Mach numbers and in confined spaces.

[0006] The technical solution of this invention is:

[0007] An integrated laser endoscope PIV flow field measurement device for turbine blades is characterized by comprising an endoscope probe (1), a turbine stator blade (2), an optical window (3), a turbine rotor blade (4), a target measurement area (5), a turbine casing (6), an imaging camera (7), a laser (8), a light guide arm (9), and a hub (10). The endoscope probe (1) is connected to the laser (8) via the light guide arm (9). The turbine casing (6) has a pre-machined small-sized optical interface that matches the outer diameter of the probe, and a flange and sealing structure are provided to fix the endoscope probe (1) to the casing, while ensuring the airtightness of the turbine interior under high-speed and high-pressure conditions. The light guide arm (9) is connected to the laser (8). The optical device (8) is connected, the laser (8) is connected to the endoscope probe (1), and a row of optical windows (3) is opened along the blade height direction of the turbine stator blade (2). The endoscope probe (1) extends into the interior of the turbine stator blade (2) through the optical interface of the turbine casing (6) and draws out the laser through the optical window (3). A laser sheet of a certain thickness and width is formed in the target measurement area (5) in the turbine channel. Tracer particles are uniformly scattered in the turbine inlet so that the tracer particles pass through the target measurement area (5) with the airflow. The imaging camera (7) synchronously takes pictures of the target measurement area (5) of the turbine channel and obtains the particle image of the turbine rotor blade (4) outlet area in the confined space.

[0008] Furthermore, the optical window (3) is evenly opened on the outer surface of the turbine stator blade (2) with equal diameter and equal spacing along the blade height direction. The window material can be sapphire glass or other types of optical glass. The laser endoscope probe (1) can move up and down along the blade height inside the turbine stator blade (2) to adapt to the measurement needs of different positions.

[0009] Furthermore, the diameter of the optical window (3) is 4 mm to 12 mm, and the interval between the two windows is 6 mm to 30 mm, so as to maintain a smooth transition with the leading edge or sidewall outer surface of the turbine stator blade (2) to reduce the interference with the original flow field;

[0010] Furthermore, the imaging camera (7), turbine speed signal, and laser (8) are all connected to the synchronous control system, and particle image acquisition at different rotor angle positions is achieved through phase-locked triggering.

[0011] Furthermore, the endoscope probe (1) can be placed inside the turbine stator blade (2) one stage before the turbine rotor blade (4) to measure the velocity field of the front section of the turbine rotor blade (4) from the upstream direction;

[0012] Furthermore, the endoscopic probe (1) has a diameter of 4 mm to 12 mm and a length of 80 mm to 300 mm. The device can be equipped with two or more imaging cameras (7) forming a certain angle to simultaneously capture images of the measurement area (5) from different perspectives for three-dimensional PIV measurement.

[0013] The beneficial effects of this invention are:

[0014] To address the challenges of large modifications to the turbine casing and limited measurement areas in existing turbine internal flow field measurements, an integrated laser endoscopic pulse-wave (PIV) flow field measurement device for turbine blades is proposed. By compactly integrating the endoscopic probe with the stator blade and arranging optical windows on the stator blade, laser light is introduced into the turbine passage while preserving the original flow characteristics as much as possible, enabling the measurement of the velocity fields at the turbine inlet and outlet, between stages, and within the rotor passage.

[0015] Beneficial effect 1:

[0016] By opening a small-sized optical interface on the turbine casing and using an endoscope probe to introduce laser light into the turbine rotor channel through an optical window inside the stator blade, the optical path can be arranged without large window openings, significantly reducing the impact on the strength and sealing of the turbine casing, while maintaining the original flow field characteristics inside the turbine as much as possible, thus reducing structural modification and processing costs.

[0017] Benefit 2:

[0018] The endoscopic probe generates laser beams in the rotor blade inlet and outlet and channel, and the imaging camera simultaneously captures images of this area. This allows for the measurement of the velocity field of the rotor's main channel, trailing edge, and inlet / outlet cross-sections within a confined space. Compared to the traditional PIV arrangement, which can only acquire a local field of view outside the casing, this invention significantly expands the measurable area and improves the targeting and effectiveness of turbine internal flow field measurement.

[0019] Benefit 3:

[0020] The optical window has high hardness and high light transmittance, enabling it to work stably under high-speed airflow and strong vibration conditions. It effectively protects the endoscope probe inside the stator from high-speed airflow erosion and tracer particle erosion, while ensuring the quality of the optical path. This provides a reliable guarantee for clear and stable particle image acquisition in high-temperature and high-speed environments.

[0021] Beneficial effect four:

[0022] The imaging camera, along with the turbine speed signal and laser, is connected to the synchronous control system. By using a phase-locked triggering method, particle images are acquired at different angles and positions, reconstructing the phase-averaged and transient velocity distribution of the unsteady flow field inside the turbine. Compared with simple steady-state measurements, this method can more comprehensively reveal the spatiotemporal evolution of the complex flow structure inside the turbine.

[0023] Benefit 5:

[0024] The device of this invention can be arranged with two or more imaging cameras at a certain angle to realize three-dimensional PIV measurement. It can not only obtain the two-dimensional velocity components in the measurement plane, but also reconstruct the three-dimensional velocity vector field. It has higher accuracy in the identification and quantitative analysis of typical structures such as leakage vortices, secondary flow, and corner separation, and provides high-quality experimental data for the study of turbine internal flow mechanism and numerical simulation verification. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a specific implementation of the laser endoscope PIV device of the present invention inside a turbine.

[0026] Figure 2 This is a schematic diagram showing the relationship between the endoscopic probe, the turbine stator blades, and the optical window.

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

[0028] Figure 4 This is a top view showing the relative position of the endoscopic probe's measurement area within the turbine channel to the turbine rotor blades.

[0029] Figure 5 This is a front view showing the relative position of the endoscopic probe and the turbine rotor blades.

[0030] Among them: 1-Endoscopic probe, 2-Turbine stator blade, 3-Optical window, 4-Turbine rotor blade, 5-Target measurement area, 6-Turbine casing, 7-Imaging camera, 8-Laser, 9-Light guide arm, 10-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 two specific embodiments.

[0033] Example 1:

[0034] like Figures 1-5 The diagram shows an integrated laser endoscope (PIV) flow field measurement device for turbine blades, used to measure the velocity field distribution inside a turbine. It includes an endoscope probe (1), a turbine stator blade (2), an optical window (3), a turbine rotor blade (4), a target measurement area (5), a turbine casing (6), an imaging camera (7), a laser (8), a light guide arm (9), and a hub (10). The endoscope probe (1) is located inside the turbine stator blade (2) one stage after the turbine rotor blade (4), used to measure the flow field in the downstream region of the turbine rotor blade (4), thus achieving velocity field measurement at the turbine rotor outlet. The endoscope probe (1) is connected to the laser (8) via the light guide arm (9). The endoscope probe (1) is placed inside the turbine stator blade (2) of the turbine rotor blade (4) being measured. The three-dimensional velocity field of the rear section of the turbine rotor blade (4) is measured from the downstream direction. Based on the structure of the turbine casing (6) and the position of the turbine stator blade (2), the installation orientation of the endoscope probe (1) and the position of the small-sized optical interface of the casing are determined. The endoscope probe (1) is fixed to the turbine casing (6) through the flange and sealing structure, so that its front end extends into the turbine stator blade (2). The light guide arm (9) is connected to the laser (8), and the laser (8) is connected to the endoscope probe (1).

[0035] A row of optical windows (3) is opened radially on the turbine stator blade (2). The endoscope probe (1) extends into the interior of the turbine stator blade (2) through the optical interface of the turbine casing (6) and extracts the laser through the optical window (3). A laser sheet of a certain thickness and width is formed in the target measurement area (5) in the turbine channel. The output energy and pulse interval of the laser (8) are adjusted, and the specific position and thickness of the laser sheet in the turbine channel are adjusted in conjunction with the optical element at the front end of the endoscope probe (1) so that the target measurement area (5) covers the area near the trailing edge and outlet of the turbine rotor blade (4). Tracer particles are uniformly seeded at the turbine inlet so that the tracer particles pass through the target measurement area (5) with the airflow. Subsequently, the imaging camera (7) synchronously captures the target measurement area (5) to obtain particle images of the area near the trailing edge and outlet of the turbine rotor blade (4) in a narrow space. Further, flow field characteristics such as vorticity, turbulence intensity, and secondary flow intensity can be calculated to realize the fine measurement and mechanism analysis of the flow field at the trailing edge and outlet of the turbine rotor blade.

[0036] In this embodiment, the optical window (3) is preferably a sapphire glass optical window, which is opened from top to bottom on the leading edge or sidewall of the turbine stator blade (2) in a manner with equal diameter and equal spacing. The laser emitted by the laser (8) enters the endoscope probe (1) through the light guide arm (9) and forms a sheet of light in the target measurement area (5) of the turbine channel through the preset sapphire glass optical window (3). The endoscope probe (1) can move up and down along the blade height inside the turbine stator blade (2) to adapt to the measurement needs of different positions. Preferably, the diameter of the optical window (3) is 8 mm, the spacing between the two windows is 20 mm, the diameter of the endoscope probe (1) is 6 mm, and the length is 250 mm. The optical window (3) maintains a smooth transition with the outer surface of the leading edge or sidewall of the turbine stator blade (2) to reduce interference with the original flow field. The imaging camera (7) is set outside the turbine casing (6) and images the target measurement area (5) through an external window. It is connected to the synchronous control system along with the turbine speed signal and the laser (8). The particle image is acquired at different rotor angle positions through the phase-locked triggering method, thereby obtaining the flow field information in the outlet area of ​​the turbine rotor blade (4) and the main flow channel.

[0037] Example 2:

[0038] An endoscope probe (1) is placed inside the turbine stator blade (2) one stage upstream of the turbine rotor blade (4) to measure the flow field in the upstream region of the turbine rotor blade (4) and realize the measurement of the turbine rotor inlet velocity field distribution. Specifically, based on the structure of the turbine casing (6) and the position of the turbine stator blade (2) upstream of the turbine rotor blade (4), the installation orientation of the endoscope probe (1) and the position of the small-sized optical interface of the casing are determined. The endoscope probe (1) is fixed to the turbine casing (6) through the flange and sealing structure, so that its front end extends into the interior of the upstream turbine stator blade (2). The turbine stator blade (2) has a row of optical windows (3) opened on the trailing edge or sidewall near the rotor inlet along the blade height direction. The endoscope probe (1) extends into the interior of the turbine stator blade (2) through the casing optical interface and draws out the laser through the optical window (3) to form a laser sheet light in the turbine channel located upstream of the leading edge of the turbine rotor blade (4) and near the inlet section. This area is defined as the target measurement area (5).

[0039] By adjusting the output energy and pulse interval of the laser (8), and coordinating with the optical elements at the front end of the endoscope probe (1) to adjust the specific position and thickness of the laser beam within the turbine channel, the target measurement area (5) covers key flow regions such as the leading edge, inlet boundary layer, and endwall corner region of the turbine rotor blade (4). Tracer particles are uniformly seeded at the turbine inlet, allowing them to pass through the target measurement area (5) with the airflow and then enter the turbine rotor blade (4) channel. An imaging camera (7) is positioned outside the turbine casing (6) to simultaneously capture images of the target measurement area (5) located near the rotor leading edge and inlet. Through phase-locked triggering with the turbine speed signal and the laser (8), particle images at different rotor angle positions are acquired, obtaining the velocity field at the inlet of the turbine rotor blade (4), providing experimental basis for studying incoming flow distortion, endwall secondary flow, corner separation, and rotation-stationary interference.

[0040] In this embodiment, the optical window (3) is also preferably made of sapphire glass and is opened from top to bottom on the trailing edge or sidewall of the upstream turbine stator blade (2) in a manner with equal diameter and equal spacing. The endoscope probe (1) can move up and down along the blade height inside the turbine stator blade (2) to adapt to the measurement needs of different positions. Preferably, the diameter of the optical window (3) is 8 mm, the spacing between the two windows is 20 mm, the diameter of the endoscope probe (1) is 6 mm, and the length is 250 mm. The optical window (3) maintains a smooth transition with the outer surface of the trailing edge or sidewall of the turbine stator blade (2) to reduce interference with the original flow field.

[0041] In this embodiment of the invention, by compactly integrating the endoscope probe (1) with the turbine stator blades (2), PIV measurements are performed on the rotor inlet and outlet regions from both upstream and downstream directions. The two embodiments complement each other, allowing the velocity field distribution on the rotor inlet and outlet sides to be obtained separately, thus enabling full-process observation and mechanism analysis of the flow evolution process within the turbine rotor channel. Simultaneously, by using the optical window (3) to introduce laser light into the turbine channel, the velocity field measurement of key areas inside the turbine can be completed in a high-speed, confined space environment without the need for large-size openings in the turbine casing (6), significantly reducing interference to the casing structure and the original flow field, and improving the applicability and accuracy of internal flow field measurement.

Claims

1. A turbine blade integrated laser endoscopic PIV flow field measurement device, characterized in that: The system includes an endoscope probe (1), turbine stator blades (2), an optical window (3), turbine rotor blades (4), a target measurement area (5), a turbine casing (6), an imaging camera (7), a laser (8), a light guide arm (9), and a hub (10). The endoscope probe (1) is connected to the laser (8) via the light guide arm (9). The turbine casing (6) has a pre-machined small-sized optical interface that matches the outer diameter of the probe, and a flange and sealing structure are provided to fix the endoscope probe (1) to the casing, while ensuring the airtightness of the turbine interior under high-speed and high-pressure conditions. The light guide arm (9) is connected to the laser (8). Connect the endoscope probe (1), and open a row of optical windows (3) along the blade height direction of the turbine stator blade (2). The endoscope probe (1) extends into the interior of the turbine stator blade (2) through the optical interface of the turbine casing (6), and draws out the laser through the optical window (3) to form a laser sheet of a certain thickness and width in the target measurement area (5) in the turbine channel. The tracer particles are evenly distributed in the turbine inlet, so that the tracer particles pass through the target measurement area (5) with the airflow. The imaging camera (7) synchronously takes pictures of the target measurement area (5) of the turbine channel and obtains the particle image of the turbine rotor blade (4) outlet area in the confined space. Furthermore, the optical window (3) is evenly opened on the outer surface of the turbine stator blade (2) with equal diameter and equal spacing along the blade height direction. The window material can be sapphire glass or other types of optical glass. The laser endoscope probe (1) can move up and down along the blade height inside the turbine stator blade (2) to adapt to the measurement needs of different positions. Furthermore, the diameter of the optical window (3) is 4 mm to 12 mm, and the interval between the two windows is 6 mm to 30 mm, so as to maintain a smooth transition with the leading edge or sidewall outer surface of the turbine stator blade (2) to reduce the interference with the original flow field; Furthermore, the imaging camera (7), turbine speed signal, and laser (8) are all connected to the synchronous control system, and particle image acquisition at different rotor angle positions is achieved through phase-locked triggering. Furthermore, the endoscope probe (1) can be placed inside the turbine stator blade (2) one stage before the turbine rotor blade (4) to measure the velocity field of the front section of the turbine rotor blade (4) from the upstream direction; Furthermore, the endoscopic probe (1) has a diameter of 4 mm to 12 mm and a length of 80 mm to 300 mm. The device can be equipped with two or more imaging cameras (7) forming a certain angle to simultaneously capture images of the measurement area (5) from different perspectives for three-dimensional PIV measurement.

Images