A PIV endoscope protection device for measuring high temperature gas flow velocity field

Abstract

The application belongs to the technical field of high-temperature flow field velocity testing, and discloses a PIV endoscope protection device for measuring high-temperature airflow velocity field. The device is characterized by a shell, an inner wall, a sapphire glass tube, a partition plate, a light guide window, a water inlet channel, a water outlet channel, an optical element, a mounting seat and a cavity. The shell, the inner wall and the sapphire glass tube are coaxially sleeved and form two interlayers respectively. The water inlet channel and the water outlet channel in the shape of Chinese character 'ji' are separated by the partition plate between the shell and the inner wall, so that the circulation of cooling water is realized, and the endoscope optical assembly and the sapphire glass tube are efficiently cooled. The structure can control the temperature near the sapphire glass tube below 500K under the extreme condition that the external environment temperature is as high as 2000K, effectively insulate high temperature and relieve thermal stress concentration, and ensure stable signal transmission and imaging measurement. Compared with the prior art, the endoscope probe can accurately reach the measurement area that cannot be covered by the traditional light source, and efficient and stable measurement of the flow field in high-temperature and complex narrow space can be realized.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature flow field velocity testing technology, specifically relating to a PIV endoscopic protection device for measuring the velocity field of high-temperature airflow, which is suitable for measuring the three-dimensional velocity field distribution inside the turbine channel, between stages, and at the turbine inlet and outlet under high-temperature and high-speed airflow conditions. Background Technology

[0002] Particle Image Velocimetry (PIV) involves introducing tracer particles into a flow field and illuminating the cross-section under test with a laser sheet light source. The trajectory of the moving particles on the cross-section is captured and recorded by a camera in a relatively short time, thereby obtaining information about the particle motion in the flow field and inferring the velocity distribution of the airflow.

[0003] PIV measurements primarily employ external optical systems to observe the overall flow field within the turbine. However, the current light source arrangement makes it difficult to effectively guide the laser sheet to the narrow cross-section inside the turbine. To accurately measure the complex flow fields between turbine stages and at the inlet and outlet, it is necessary to connect optical probes such as endoscopes to precisely guide the laser sheet light source and illuminate the measured cross-section. However, the internal environment of a high-pressure turbine is extremely hot, and the endoscope itself and its optical components are highly susceptible to damage from heat radiation and airflow erosion, leading to decreased measurement accuracy or even equipment failure. Furthermore, localized high-temperature areas can cause severe thermal stress concentration, further weakening the stability and lifespan of the endoscope structure.

[0004] Currently, although some endoscopic devices exist for PIV measurements in high-temperature environments, they still have significant shortcomings in terms of probe heat resistance, endoscopic window erosion resistance, cooling system efficiency, and optical path stability. These limitations make it difficult to meet the requirements for long-term, continuous, and accurate measurements in ultra-high temperature and high-speed airflow environments. Therefore, there is an urgent need to develop a PIV endoscopic protection device for measuring high-temperature airflow velocity fields. This device should effectively reduce the overall temperature, alleviate thermal stress effects, and improve structural strength and durability, ensuring the stability and safety of laser guidance, particle imaging, and data acquisition processes. This would enhance the reliability and application scope of high-temperature flow field testing technology. Summary of the Invention

[0005] The technical problem this invention aims to solve is the limitations of traditional PIV technology in high-temperature, small-scale regions during the measurement of three-dimensional velocity fields between turbine stages and at turbine inlet and outlet, as well as the structural damage to the endoscopic device caused by excessively high ambient temperatures. This invention provides a PIV endoscopic protection device for measuring high-temperature airflow velocity fields. Compared to existing PIV measurement devices, it provides effective thermal protection and cooling for the endoscope in high-temperature environments; it also features flexible adjustment capabilities, enabling the endoscope probe to accurately reach measurement areas that are difficult to cover with traditional light sources; and it achieves efficient and stable measurement of high-temperature, complex, and confined spatial flow fields.

[0006] The technical solution of the present invention is as follows:

[0007] A PIV endoscope protection device for measuring the velocity field of high-temperature air flow, characterized in that it includes a housing (1), an inner wall (2), a sapphire glass tube (3), a partition (4), a light guide window (5), a water inlet channel (6), a water outlet channel (7), an optical element (8), a mounting seat (9) and a cavity (10). The housing (1), the inner wall (2) and the sapphire glass tube (3) are coaxially sleeved. An interlayer is formed between the housing (1) and the inner wall (2) and between the inner wall (2) and the sapphire glass tube (3). The water-cooling channel is arranged at the interlayer between the housing (1) and the inner wall (2). An optical element (8) is arranged inside the sapphire glass tube (3), which has excellent high light transmittance and high temperature resistance, and can also effectively solve the problems of sealing, anti-vibration and structural strength in the high-temperature and high-speed air flow environment through its high strength and high hardness characteristics, ensuring that the protection device can still maintain good optical performance and structural stability under severe vibration and strong heat shock conditions.

[0008] Furthermore, the housing (1) and the inner wall (2) are separated by a vertically arranged partition (4) to form a water inlet channel (6) and a water outlet channel (7), so that the cooling water channel flows in a "zigzag" path to cool the sapphire glass tube (3) and the optical element (8). To prevent the cooling water from boiling in a local area, a chamfer is designed at the water flow channel corner area at the head of the device to avoid structural damage caused by thermal stress concentration due to high temperature.

[0009] Furthermore, the light guide windows (5) are arranged on the side wall of the housing (1) from top to bottom in an equal-diameter and equal-spacing manner and penetrate through the partition (4) to directly reach the internal cavity (10). The optical signal of the target measurement area enters the optical element (8) inside the sapphire glass tube (3) through the preset light guide window (5), and then is guided to the outside by the optical element (8). The optical element (8) can move up and down axially inside the sapphire glass tube (3) to adapt to the measurement requirements at different positions. The optical element (8) can be a reflecting mirror or an endoscope camera.

[0010] Furthermore, a mounting seat (9) is provided at the rear of the device, on which four fixing threads are provided for fixing the device to the turbine casing to ensure the stability and position accuracy of the device during operation.

[0011] Furthermore, the diameter of the housing (1) is 8 mm to 20 mm, the length is 50 mm to 250 mm, and the diameter of the inner wall (2) is 6 mm to 15 mm.

[0012] Furthermore, the inner diameter of the sapphire glass tube (3) is 4 mm to 10 mm, the outer diameter is 5 mm to 13 mm, and the diameter of the light guide window (5) is 1 mm to 5 mm.

[0013] Furthermore, the cooling water channel inlet and outlet are designed to gradually transition from a cashew nut-shaped cross-section to a circular cross-section structure. The flow area of ​​each cross-section is equal, avoiding flow separation and eddy current phenomena caused by abrupt changes in cross-section. The cashew nut-shaped cross-section can effectively guide the fluid to generate appropriate turbulence in the initial stage of entering the pipe, increasing the local heat exchange efficiency and improving the cooling effect.

[0014] The beneficial effects of this invention are:

[0015] Benefit 1: The sapphire glass tube is coaxially arranged with the hollow cylindrical outer shell. The outer shell supports and protects the internal components, effectively resisting the thermal shock of the external high-temperature airflow. Cooling water channels are provided between the outer shell and the inner wall, and the cooling water also acts as insulation. The cooling water flows in a "U"-shaped pattern, significantly improving the overall heat exchange efficiency of the cooling device. Chamfered corners effectively alleviate thermal stress concentration caused by abrupt structural changes and prevent localized boiling of the cooling water in high-temperature areas or thermal ablation due to the cavity effect. This allows the temperature near the sapphire glass tube to be effectively controlled below 500K even under external ambient temperatures as high as 2000K and airflow Mach number 1.5.

[0016] Benefit 2: A cavity is provided between the sapphire glass tube and the cooling device, which reduces heat conduction. The sapphire glass tube contains vertically movable optical elements, allowing for flexible adjustment of the optical path and accurate guidance of the laser to the target cross-section. The longitudinally equidistant and equally spaced light guide windows enable uniform emission from multiple points, expanding the measurement coverage area.

[0017] Benefit 3: The cooling water channel inlet and outlet are designed to gradually transition from a cashew nut-shaped cross-section to a circular cross-section structure. The flow area of ​​each cross-section is equal, avoiding flow separation and eddy current phenomena caused by abrupt changes in cross-section. The cashew nut-shaped cross-section can effectively guide the fluid to generate appropriate turbulence in the early stage of entering the pipe, increase the local heat exchange efficiency, and improve the cooling effect.

[0018] Fourthly, the flexible adjustable optical elements and multi-point light guide windows of this invention enable laser coverage of narrow spaces that are difficult to reach using traditional methods, allowing for long-term, continuous, and accurate PIV measurements in small-scale regions with high-temperature, high-speed airflow. After calibration, the invention can realize the three-dimensional velocity field distribution within the turbine channel, between stages, and at the turbine inlet and outlet under high-temperature, high-speed airflow conditions.

[0019] Benefit 5: Sapphire glass tubes have excellent high light transmittance and high temperature resistance. They can also effectively solve the problems of sealing, vibration resistance and structural strength in high temperature and high speed airflow environments through their high strength and high hardness characteristics, ensuring that the protection device can still maintain good optical performance and structural stability under severe vibration and strong thermal shock conditions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a PIV endoscopic protection device for measuring the velocity field of high-temperature airflow in an embodiment of the present invention.

[0021] Figure 2 for Figure 1 The main view.

[0022] Figure 3 for Figure 1 A bottom view.

[0023] Figure 4 for Figure 1 Sectional view of section AA.

[0024] Figure 5 for Figure 4 A magnified view of a portion of the image.

[0025] Figure 6 This is a cross-sectional view showing the changing shape of the water inlet and outlet sections.

[0026] Figure 7 This is a schematic diagram illustrating the specific implementation.

[0027] The components are: 1-outer shell, 2-inner wall, 3-sapphire glass tube, 4-partition, 5-light guide window, 6-water inlet channel, 7-water outlet channel, 8-reflector, 9-mounting base, 10-cavity, 11-displacement mechanism, 12-turbine. Detailed Implementation

[0028] 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.

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] like Figures 1-6 The image shows a PIV endoscopic protection device for measuring high-temperature airflow velocity fields according to the present invention. Figure 7 This is a schematic diagram of the device of the present invention used to measure the three-dimensional velocity field distribution in a multi-stage turbine channel. It includes an outer shell (1), an inner wall (2), a sapphire glass tube (3), a partition (4), a light guide window (5), a water inlet channel (6), a water outlet channel (7), an optical element (8), a mounting base (9), and a cavity (10). The outer shell (1), the inner wall (2), and the sapphire glass tube (3) are coaxially fitted together. An interlayer is formed between the outer shell (1) and the inner wall (2) and between the inner wall (2) and the sapphire glass tube (3). The water cooling channel is set in the interlayer between the outer shell (1) and the inner wall (2). The optical element (8) is set inside the sapphire glass tube (3).

[0031] Between the outer shell (1) and the inner wall (2), a partition plate (4) arranged vertically is used to separate and form an inlet channel (6) and an outlet channel (7), so that the cooling water channel flows in a "zigzag" path, cooling the sapphire glass tube (3) and the optical element (8). To prevent the boiling phenomenon of the cooling water in a local area, a chamfer is designed at the corner area of the water flow channel at the head of the device, avoiding the structural damage caused by the concentration of thermal stress due to high temperature. Under the condition that the external environmental temperature is as high as 2000K and the air flow Mach number is 1.5, the temperature of the optical element can be effectively controlled at about 340K;

[0032] The light guiding windows (5) are arranged on the side wall of the outer shell (1) from top to bottom in an equal-diameter and equal-spacing manner, and penetrate through the partition plate (4) and directly lead to the internal cavity (10). The light signal in the target measurement area enters the optical element (8) in the sapphire glass tube (3) through the preset light guiding window (5), and then is guided by the optical element (8) to an external camera. Among them, the optical element (8) can move up and down axially inside the sapphire glass tube (3) to adapt to the measurement requirements at different positions. The optical element (8) is a reflector;

[0033] An installation seat (9) is provided at the rear of the device, and four fixing threads are provided thereon for fixing the device to the turbine casing, ensuring the stability and position accuracy of the device during operation;

[0034] In this embodiment, it is preferably that the diameter of the outer shell (1) is 12 mm, the length is 180 mm, and the diameter of the inner wall (2) is 9 mm;

[0035] The inner diameter of the sapphire glass tube (3) is 6 mm, the outer diameter is 8 mm, and the diameter of the light guiding window (5) is 2 mm;

[0036] The inlet and outlet of the cooling water channel are designed to gradually and smoothly transition from a "cashew nut" cross-section to a circular cross-section structure, and the flow areas of each cross-section are equal, avoiding the flow separation and vortex phenomena caused by the sudden change of the cross-section. The cashew nut cross-section can effectively guide the fluid to generate appropriate turbulence at the initial stage of entering the pipeline, increasing the local heat exchange efficiency and enhancing the cooling effect.

[0037] The specific implementation is shown as Figure 7As shown, the displacement mechanism (11) drives the optical element (8) to move axially within the sapphire glass tube (3), achieving a positioning accuracy of ±0.01mm. The laser beam, after being refracted by a reflector, penetrates the light guide window (5) and illuminates the cross-section where the tracer particles are located. An external high-speed camera simultaneously captures two frames of images. Subsequently, the displacement mechanism (11) moves the optical element (8) to the next measurement position according to a preset stepping program, repeating laser irradiation and image acquisition until the entire circumferential and axial regions of the blade are covered. By performing digital correlation analysis on the particle images of each measurement cross-section, a three-dimensional velocity field distribution map inside the turbine can be obtained, enabling dynamic, continuous, and accurate measurement of small-scale regions of high-temperature, high-speed airflow.

[0038] This invention discloses a PIV (Pulse Vibration) endoscope protection device for measuring high-temperature airflow velocity fields. Equipped with axially movable optical elements and multi-point light guide windows, it enables the light source to reach the narrow space of the turbine, achieving long-term, continuous, and accurate PIV measurement of small-scale areas with high-temperature and high-speed airflow. Even under external ambient temperatures as high as 2000K and Mach number 1.5, the device can effectively control the temperature of the sapphire glass tube and optical elements below 500K, providing reliable thermal protection and cooling for the endoscope, alleviating thermal stress concentration, ensuring stable signal transmission and imaging quality, and covering narrow spaces that are difficult to reach by traditional methods. This significantly improves the stability, accuracy, and applicability of high-temperature airflow velocity field PIV measurement.

Claims

1. A PIV endoscopic protection device for measuring high-temperature airflow velocity fields, characterized in that: It includes a housing (1), an inner wall (2), a sapphire glass tube (3), a partition (4), a light guide window (5), a water inlet channel (6), a water outlet channel (7), an optical element (8), a mounting seat (9) and a cavity (10). The housing (1), the inner wall (2) and the sapphire glass tube (3) are coaxially sleeved. Interlayers are formed between the housing (1) and the inner wall (2) and between the inner wall (2) and the sapphire glass tube (3). The water cooling channel is arranged at the interlayer between the housing (1) and the inner wall (2). An optical element (8) is arranged inside the sapphire glass tube (3). Furthermore, the housing (1) and the inner wall (2) are separated by a vertically arranged partition (4) to form a water inlet channel (6) and a water outlet channel (7), so that the cooling water channel flows in a "zigzag" path to cool the sapphire glass tube (3) and the optical element (8). To prevent the cooling water from boiling in a local area, a chamfer is designed at the water flow path corner area at the head of the device to avoid structural damage caused by thermal stress concentration due to high temperature. Furthermore, the light guide windows (5) are arranged on the side wall of the housing (1) from top to bottom in an equal-diameter and equal-spacing manner and penetrate through the partition (4) directly to the internal cavity (10). The light signal of the target measurement area enters the optical element (8) inside the sapphire glass tube (3) through the preset light guide window (5), and then is guided to the outside by the optical element (8). The optical element (8) can move axially up and down inside the sapphire glass tube (3) to adapt to the measurement requirements at different positions. The optical element (8) is a reflector or an endoscope camera. Furthermore, a mounting seat (9) is provided at the rear of the device, and four fixing threads are provided thereon for fixing the device to the turbine casing to ensure the stability and position accuracy of the device during operation. Furthermore, the diameter of the housing (1) is 8 mm to 20 mm, and the length is 50 mm to 250 mm. The diameter of the inner wall (2) is 6 mm to 15 mm. Furthermore, the inner diameter of the sapphire glass tube (3) is 4 mm to 10 mm, the outer diameter is 5 mm to 13 mm, and the diameter of the light guide window (5) is 1 mm to 5 mm. Furthermore, the water inlet and outlet of the cooling water channel are designed to gradually and smoothly transition from a "cashew" - shaped cross-section to a circular cross-section structure, and the flow areas of each cross-section are equal.

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