PIV (Particle Image Velocimetry) endoscopic protection device for measuring high-temperature airflow velocity field

Abstract

The invention belongs to the technical field of high-temperature flow field velocity testing, and discloses a PIV (particle image velocimetry) endoscopic protection device for measuring a high-temperature airflow velocity field, which is suitable for measuring three-dimensional velocity field distribution in a turbine channel, between stages and at an inlet and an outlet of a turbine in a high-temperature and high-speed airflow environment. The device is characterized by comprising 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 respectively form two-stage interlayers; the space between the shell and the inner wall is divided into an n-shaped water inlet channel and an n-shaped water outlet channel through a partition plate, circulating flowing of cooling water is achieved, and an endoscope optical assembly and a sapphire glass tube are efficiently cooled. Light guide windows are formed in the side wall of the shell from top to bottom in an equal-diameter and equal-interval mode, and an optical element capable of moving up and down in the glass tube in the axial direction is combined, so that the narrow measurement section in the turbine can be accurately measured; according to the structure, the temperature near the sapphire glass tube can be controlled below 500K under the extreme condition that the external environment temperature is up to 2000K, high temperature is effectively isolated, thermal stress concentration is relieved, and stable signal transmission and imaging measurement are ensured. Compared with the prior art, the endoscope probe can accurately reach a measurement area which is difficult to cover by a traditional light source, and efficient and stable measurement of a high-temperature, complex and narrow space flow field is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature flow field velocity measurement, and particularly relates to a PIV endoscope protection device for measuring the velocity field of high-temperature airflows, which is applicable to measuring the three-dimensional velocity field distribution inside the turbine passage, between stages, and at the inlet and outlet of the turbine in a high-temperature and high-speed airflow environment. Background Art

[0002] Particle Image Velocimetry (PIV) adds tracer particles to the flow field and uses a laser sheet light source to irradiate the measured cross-section, so that the movement trajectories of the particles moving on the cross-section are recorded by a camera in a relatively short time, thereby obtaining the movement information of the particles in the flow field and further inversely calculating the velocity distribution of the airflow.

[0003] PIV measurement mainly uses an external optical system to observe the overall flow field of the machine. The light source arrangement method is difficult to effectively guide the laser sheet to the narrow cross-section inside the turbine; to accurately measure the complex internal flow fields such as between turbine stages and at the inlet and outlet, it is necessary to access an optical probe such as an endoscope to accurately guide and irradiate the laser sheet light source to the measured cross-section. However, the internal environment temperature of the high-pressure turbine is extremely high, and the endoscope body and its optical components are extremely easy to be damaged due to thermal radiation and airflow erosion, resulting in a decrease in measurement accuracy or even equipment failure; at the same time, serious thermal stress concentration problems will also be caused in local high-temperature areas, further weakening the stability and service life of the endoscope structure.

[0004] At present, although there are already some endoscope devices for PIV measurement in high-temperature environments, there are still obvious deficiencies in aspects such as the heat resistance of the probe, the erosion resistance of the endoscope window, the efficiency of the cooling system, and the optical path stability, and it is difficult to meet the requirements of long-term, continuous, and accurate measurement in an ultra-high-temperature and high-speed airflow environment. Therefore, there is an urgent need to develop a PIV endoscope protection device for measuring the velocity field of high-temperature airflows, which can effectively reduce the overall temperature, relieve the thermal stress effect, improve the structural strength and durability, and ensure the stability and safety of the laser guidance, particle imaging, and data acquisition processes, so as to improve the reliability and application range of high-temperature flow field measurement technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: aiming at the problems that in the process of measuring the three-dimensional velocity field of the turbine stage and the turbine inlet and outlet, the traditional PIV technology is limited in application in high-temperature small-scale areas, and the endoscope device structure is damaged due to the too high surrounding environment temperature. An invention provides a PIV endoscope protection device for measuring the velocity field of high-temperature airflows. Compared with the existing PIV measurement device, it can provide effective thermal protection and cooling for the endoscope in a high-temperature environment; at the same time, it has a flexible adjustment function, enabling the endoscope probe to accurately reach the measurement area that is difficult to cover by the traditional light source; and it realizes the efficient and stable measurement of the flow field in high-temperature, complex and narrow spaces.

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

[0007] A PIV endoscope protection device for measuring the high-temperature gas flow velocity field, 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. A sandwich layer 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 sandwich layer 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 gas 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). In order 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 heat stress concentration caused by high temperature;

[0009] Furthermore, the light guide windows (5) are opened 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 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). 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) can be a 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 opened 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 water inlet and outlet of the cooling water channel are designed to gradually and smoothly transition from a "cashew nut" - shaped cross - section to a circular cross - section structure, and the flow - through areas of each cross - section are equal, avoiding the flow separation and vortex phenomena caused by cross - section mutation. The cashew - nut - shaped 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.

[0014] The beneficial effects of the present invention are as follows:

[0015] Beneficial effect one: The sapphire glass tube and the hollow cylindrical shell are coaxially arranged. The shell supports and protects the internal components, effectively resisting the thermal shock of the external high - temperature gas flow. There is a cooling water channel between the shell and the inner wall, and the cooling water also plays a heat - insulation role. The cooling water has a "ji" - shaped flow layout, which can significantly improve the overall heat - transfer efficiency of the cooling device. The chamfer structure design is introduced at the corner, effectively alleviating the problem of thermal stress concentration caused by local structural mutation, and preventing local boiling of the cooling water in the high - temperature area or thermal ablation phenomenon caused by the cavity effect. Under the conditions of an external environmental temperature as high as 2000K and an air - flow Mach number of 1.5, the temperature near the sapphire glass tube can be effectively controlled below 500K.

[0016] Beneficial effect two: There is a cavity between the sapphire glass tube and the cooling device, which can reduce heat conduction. An optical element that can move up and down is arranged inside the sapphire glass tube, which can flexibly adjust the optical path, accurately guide the laser to the target cross - section, and the longitudinally equal - diameter and equally - spaced light - guiding windows can achieve multi - point uniform light emission, expanding the measurement coverage range.

[0017] Beneficial effect three: The water inlet and outlet of the cooling water channel are designed to gradually and smoothly transition from a "cashew nut" - shaped cross - section to a circular cross - section structure, and the flow - through areas of each cross - section are equal, avoiding the flow separation and vortex phenomena caused by cross - section mutation. The cashew - nut - shaped 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.

[0018] Beneficial effect four: The flexibly adjustable optical element and multi - point light - guiding windows of the present invention enable the laser to cover narrow spaces that are difficult to reach by traditional methods, and can perform PIV measurements continuously, accurately, and for a long time in small - scale areas of high - temperature and high - speed airflows. After calibration, the invention can realize the three - dimensional velocity - field distribution in the turbine channel, between stages, and at the inlet and outlet of the turbine in a high - temperature and high - speed airflow environment.

[0019] Beneficial effect five: The sapphire glass tube has excellent high light - transmittance and high - temperature resistance properties. It can also effectively solve the problems of sealing, anti - vibration, and structural strength in a high - temperature and high - speed airflow 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 thermal shock conditions; Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of a PIV endoscope protection device for measuring the high-temperature gas flow velocity field in an embodiment of the present invention.

[0021] Figure 2 is Figure 1 the front view of.

[0022] Figure 3 is Figure 1 the bottom view of.

[0023] Figure 4 is Figure 3 the cross-sectional view of the A-A section of.

[0024] Figure 5 is Figure 4 the partial enlarged view of.

[0025] Figure 6 is the sectional view of the changing shape of the water inlet and outlet sections.

[0026] Figure 7 is the schematic view of the specific implementation.

[0027] Wherein: 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 seat, 10 - cavity, 11 - displacement mechanism, 12 - turbine. Detailed Description of the Invention

[0028] The following describes in detail the preferred embodiments of the present invention 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 making a more clear and definite definition of the protection scope of the present invention.

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

[0030] As Figures 1 to 6 shown, it is a PIV endoscope protection device for measuring the high-temperature gas flow velocity field of the present invention. Figure 7 is a schematic diagram of the device of the present invention for measuring 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 seat (9) and a cavity (10). The outer shell (1), the inner wall (2) and the sapphire glass tube (3) are coaxially sleeved. Interlayers are 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 arranged at the interlayer between the outer shell (1) and the inner wall (2). An optical element (8) is arranged inside the sapphire glass tube (3);

[0031] Between the outer shell (1) and the inner wall (2), a vertical partition (4) is provided to separate and form an inlet channel (6) and an outlet channel (7), so that the cooling water channel flows in a "Ji" - shaped path to cool the sapphire glass tube (3) and the optical element (8). To prevent the cooling water from boiling in a local area, chamfers are designed at the corner areas of the water flow channels at the head of the device to avoid structural damage caused by thermal stress concentration due to high temperature. Thus, under the conditions of an external environmental temperature as high as 2000K and an air flow Mach number of 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 (4) directly to 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 - guiding window (5), and then is guided to an external camera by the optical element (8). Among them, 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;

[0033] At the rear of the device, there is a mounting seat (9) with four fixing threads provided thereon for fixing the device to the turbine casing to ensure 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" - shaped cross - section to a circular cross - section structure, and the flow - through areas of each cross - section are equal to avoid flow separation and vortex phenomena caused by sudden changes in the cross - section. The cashew - nut - shaped cross - section can effectively guide the fluid to generate appropriate turbulence at the initial stage of entering the pipeline, increase the local heat - exchange efficiency, and improve 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) with a positioning accuracy of ±0.01 mm. The laser beam penetrates the light guiding window (5) after being refracted by the reflector and irradiates the cross-section where the tracer particles are located. The external high-speed camera synchronously captures two frames of images. Subsequently, the displacement mechanism (11) translates the optical element (8) to the next measurement position according to the preset stepping program, repeats the 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, the distribution map of the three-dimensional velocity field inside the turbine can be obtained, realizing the dynamic, continuous, and accurate measurement of small-scale regions of high-temperature and high-speed airflow.

[0038] A PIV endoscope protection device for measuring the velocity field of high-temperature airflow introduced in the embodiment of the present invention is equipped with an axially flexible movable optical element and a multi-point light guiding window, which can enable the light source to reach the narrow space of the turbine, realize long-term, continuous, and precise PIV measurement of small-scale regions of high-temperature and high-speed airflow, so that under the conditions of an external environmental temperature of up to 2000 K and a Mach number of 1.5, the device can still effectively control the temperature of the sapphire glass tube and the optical element below 500 K, provide reliable thermal protection and cooling for the endoscope, relieve the thermal stress concentration, ensure the stable transmission of signals and the imaging quality, can cover narrow spaces that are difficult to reach by traditional methods, and significantly improve the stability, accuracy, and application range of PIV measurement of the high-temperature airflow velocity field.

Claims

1. The technical solution of the present invention is: a PIV endoscope protection device for measuring the high-temperature air flow velocity field, 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), which has excellent high light transmittance and high temperature resistance. Also, due to its high strength and high hardness characteristics, it can effectively solve the problems of sealing, anti-vibration and structural strength in the high-temperature and high-speed airflow environment, ensuring that the protection device can still maintain good optical performance and structural stability under severe vibration and strong heat shock conditions; Further, 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 "Ji” - shaped 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 heat stress concentration due to high temperature; Further, the light guide windows (5) are opened 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 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). Among them, 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) can be a reflector or an endoscope camera; Further, a mounting seat (9) is provided at the rear of the device, on which four fixing threads are opened for fixing the device to the turbine casing to ensure the stability and position accuracy of the device during operation; Further, 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; Further, 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; Further, the water inlet and outlet of the cooling water channel are designed to gradually and smoothly transition from a "cashew - nut” - shaped cross - section to a circular cross - section structure, and the flow area of each cross - section is equal, avoiding flow separation and vortex phenomena caused by sudden cross - section changes. The cashew - nut - shaped 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 improving the cooling effect.

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