A three-dimensional dynamic boundary layer probe for measuring the hub between the rotating and static parts of a fan

Abstract

The present invention belongs to the technical field of subsonic three-dimensional flow field parameter measurement, and specifically relates to a three-dimensional dynamic boundary layer probe for measuring the hub between the rotor and stator of a fan. It includes a probe head, a strut, a dynamic pressure sensor, and a positioning block. The probe head includes a cylinder and a double-twist line of revolution body with a common bottom surface, and a dynamic pressure sensor is encapsulated inside. On the side surface of the double-twist line of revolution body of the probe head, there is a pressure sensing hole, which is connected to the dynamic pressure sensor inside the probe head. The sensor cable is led out of the probe tail through the inner channel of the probe strut, and a positioning block is sleeved on the probe tail. The present invention has been calibrated in a calibration wind tunnel and can measure the dynamic changes of three-dimensional flow field parameters in the boundary layer of the hub between the rotor and stator of the fan. The flow field parameters include the pitch angle of the airflow, the yaw angle of the airflow, total pressure, static pressure, and Mach number, providing measurement data for improving the performance of the fan. Compared with other boundary layer probes, the probe head of the present invention adopts a double-twist line of revolution body structure, the probe head is in an "I" shape, and the vertical distance from the center of the pressure sensing hole to the lowest point of the probe head is relatively small, having the advantages of self-positioning function, small size, high spatial resolution, being able to be inserted into the hub between the rotor and stator of the fan for measurement, small interference to the measured flow field, high measurement accuracy, and multi-parameter dynamic measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of subsonic three-dimensional flow field parameter measurement, and particularly relates to a three-dimensional dynamic boundary layer probe for measuring the hub between a fan rotor and a stator, which is applicable to measuring the dynamic changes of three-dimensional flow field parameters in the boundary layer of the hub between a fan rotor and a stator. The flow field parameters include the airflow pitch angle, airflow deflection angle, total pressure, static pressure, and Mach number. Background Art

[0002] Obtaining the three-dimensional dynamic boundary layer airflow pitch angle, airflow deflection angle, total pressure, static pressure, and Mach number of the hub between a fan rotor and a stator plays an important role in improving the performance of the fan. Due to the influence of the rotor blade wake, corner vortices, and other secondary flows on the boundary layer flow field in the hub area, the internal flow field has strong unsteadiness and vorticity. Moreover, the axial gap between the fan rotor and the stator is very small, especially in medium and small-sized fans, the axial gap between the rotor and the stator is even smaller. Therefore, for the measurement of three-dimensional flow field parameters inside the boundary layer of the hub between a fan rotor and a stator, there are measurement difficulties such as a large positive airflow pitch angle, a large airflow deflection angle, a thin boundary layer thickness, and a narrow measurement space.

[0003] Currently, the measurement of boundary layer flow field parameters can be divided into two methods: contact measurement and non-contact measurement.

[0004] Contact measurement mainly uses measurement methods such as boundary layer probes, hot wires, and dynamic wall static pressure sensors. For conventional boundary layer probes, since the probe head is L-shaped, it cannot be inserted into the space between the fan rotor and the stator for measurement. Moreover, the boundary layer probe also has a very large cavity effect and can only obtain the steady-state total pressure value at the measurement point, and cannot measure the dynamic changes of the airflow pitch angle, airflow deflection angle, static pressure, and Mach number. According to the insensitivity of the boundary layer probe to the airflow direction, when the flow field deflection angle is large, the boundary layer probe cannot obtain an accurate total pressure value. When using a hot wire probe to measure the boundary layer flow field, usually only one-dimensional flow field dynamic velocity signals can be measured, and no dynamic parameter information of the airflow pitch angle, airflow deflection angle, total pressure, static pressure, and Mach number can be provided. The dynamic wall static pressure sensor can be installed on the surface of the casing to measure the dynamic static pressure of the casing boundary layer. However, since the hub rotates, the installation of the sensor on the hub surface is restricted, and it is very difficult to measure the dynamic static pressure of the hub boundary layer. Moreover, the dynamic wall static pressure sensor cannot measure the airflow pitch angle, airflow deflection angle, total pressure, and Mach number.

[0005] Non-contact measurements mainly include measurement methods such as Particle Image Velocimetry (PIV), Laser Doppler Velocimetry (LDV), Phase Doppler Particle Analyzer (PDPA), and Pressure Sensitive Paint (PSP). PIV / LDV / PDPA do not interfere with the flow field and are commonly used for measuring flow field velocities. However, during the measurement of the boundary layer flow field velocity, problems such as wall reflection and low particle concentration exist, making it impossible to obtain accurate boundary layer velocity field data. Moreover, these measurement methods cannot provide dynamic change information of total pressure and static pressure. Pressure Sensitive Paint (PSP) can obtain the distribution cloud map of the dynamic static pressure on the wall surface by utilizing the sensitivity of the pressure sensitive coating to pressure, and can reflect the dynamic changes of the static pressure within the boundary layer of the hub. However, pressure sensitive paint is a macroscopic measurement method that cannot obtain accurate static pressure values, and furthermore, it cannot obtain dynamic information on the airflow pitch angle, airflow yaw angle, total pressure, and Mach number.

[0006] In the fan test, for the measurement of the three-dimensional flow field parameters of the boundary layer of the hub between the rotating and stationary parts, we more hope to obtain the dynamic changes of the airflow pitch angle, airflow yaw angle, total pressure, static pressure, and Mach number in the boundary layer flow field for validating the fan design and flow field diagnosis in order to improve the machine performance. The above-mentioned probes cannot meet the test requirements. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: to measure the dynamic changes of the airflow pitch angle, airflow yaw angle, total pressure, static pressure, and Mach number in the three-dimensional flow field of the boundary layer of the hub between the rotating and stationary parts of the fan. For this purpose, the present invention provides a three-dimensional dynamic boundary layer probe for measuring the hub between the rotating and stationary parts of the fan. Compared with other boundary layer probes, the present invention has the advantages of self-positioning function, small size, high spatial resolution, can be inserted into the rotating and stationary parts for measurement, small interference to the measured flow field, high measurement accuracy, and multi-parameter dynamic measurement. The present invention is suitable for measuring the dynamic changes of the airflow pitch angle, airflow yaw angle, total pressure, static pressure, and Mach number in the three-dimensional flow field of the boundary layer of the hub between the rotating and stationary parts of the fan.

[0008] The technical solution of the present invention is:

[0009] 1. A three-dimensional dynamic boundary layer probe for measuring the hub between the rotating and stationary parts of the fan, which is composed of a probe head (1), a strut (2), a dynamic pressure sensor (6), and a positioning block (8). It is characterized in that: the probe head (1) is a cylinder (3) and a surface of revolution of a lemniscate (4) with a common bottom surface. The connection between the cylinder (3) and the surface of revolution of the lemniscate (4) is smoothly transitioned by a curved surface. A dynamic pressure sensor (6) is encapsulated inside the probe head (1). On the surface of the surface of revolution of the lemniscate, a pressure sensing hole (5) is opened, which is an inclined hole (5). The inclined hole (5) is communicated with the dynamic pressure sensor (6) encapsulated inside the probe head (1). The center line of the inclined hole (5) and the axis of the cylinder (3) of the probe head (1) are in the same plane. The axis of the cylinder of the probe head (1) coincides with the axis of the probe strut (2).

[0010] 2. Further, the diameter of the cylinder (3) of the probe head (1) is d, and the value range is 1.5 mm ≤ d ≤ 2.3 mm, and the length is 4d to 8d.

[0011] 3. Further, the surface of revolution (4) is formed by rotating the AB curve segment on the lemniscate around the axis L. Point A is the intersection point of the lemniscate, the tangent line at point B is perpendicular to the tangent line at point A, and the rotation axis L passes through point A and is perpendicular to the tangent line at point A.

[0012] 4. Further, the diameter of the inclined hole (5) is 0.2 mm to 0.4 mm, and the included angle between the center line of the inclined hole (5) and the axis of the cylinder (3) of the probe head (1) is θ, and the value range is 0° ≤ θ < 90°.

[0013] 5. Further, the vertical distance h from the center of the inclined hole (5) to the lowest point on the surface of the surface of revolution of the lemniscate (4) ranges from 0d ≤ h < 0.29d.

[0014] 6. Further, the probe rod (2) is a cylinder with a diameter of D, and the value range is 4 mm ≤ D ≤ 10 mm. There is a circular pipe inside it. The cable (7) of the dynamic pressure sensor encapsulated in the probe head (1) is led out of the probe tail through the pipe inside the probe rod (2), and a positioning block (8) is sleeved on the probe tail.

[0015] 7. Further, the positioning block (8) is an integral structure, including a rectangular parallelepiped base (9), a cylindrical boss (10), a through hole (11), and a threaded hole (12). It is sleeved on the probe tail through the through hole (11) and fixed by a countersunk head screw (13) passing through the threaded holes (12) on both sides of the boss (10), and the countersunk head screw (13) is completely embedded in the threaded hole (12).

[0016] 8. Further, the rectangular parallelepiped base (9) includes four rectangular sides and two square bottoms. Among the four sides, two adjacent sides are perpendicular to each other, and all four sides can be used as positioning surfaces. One bottom surface of the base (9) is connected to the cylindrical boss (10), and the perpendicular bisector of the bottom surface coincides with the axis of the boss (10). The axis of the boss (10) coincides with the center line of the through hole (11). The diameter of the through hole is D + 0.05 mm, the outer diameter of the boss is M, and the value range is D + 2 mm ≤ M ≤ D + 5 mm. The side length of the bottom surface of the base (9) is from M to M + 3 mm, and the thickness of the base (9) is H, and the value range is 2 mm ≤ H ≤ 5 mm.

[0017] The beneficial effects of the present invention are:

[0018] Compared with other boundary layer probes, the present invention is a three-dimensional dynamic boundary layer probe for measuring the hub between the rotating and stationary parts of a fan, and has the following beneficial effects:

[0019] Beneficial effect 1: The probe head of the present invention adopts a double-twisted wire spiral body structure, and the dynamic pressure sensor can be installed closer to the pressure sensing hole, which greatly reduces the volume of the cavity between the pressure sensing hole and the sensor, reduces the cavity effect, improves the frequency response of the probe, and can measure the dynamic parameters of the flow field; the vertical distance between the center of the pressure sensing hole and the lowest point of the double-twisted wire spiral body surface is small, which can realize the measurement of the three-dimensional flow field parameters inside the hub boundary layer, and the parameters include airflow pitch angle, airflow deflection angle, total pressure, static pressure and Mach number; the probe head is "丨"-shaped and small in size. On the one hand, the probe can be inserted into the fan rotor and static space for measurement, which causes little interference to the measured flow field. On the other hand, the probe has a high spatial resolution.

[0020] Beneficial effect two: There is a smooth curved surface transition between the double-twisted wire body and the cylindrical body of the probe head. When the airflow flows over the surface of the double-twisted wire body, the special structure of the double-twisted wire body can suppress the airflow separation on its surface and reduce the interference of the flow around the support rod head on the flow field in the boundary layer. On the other hand, when measuring the flow field parameters close to the hub, the present invention can suppress the scale of the horseshoe vortex at the front end of the probe head and improve the measurement accuracy.

[0021] Beneficial effect three: The positioning block used in the present invention is small in size and has little impact on the probe during the measurement process. Since the four sides can be used as positioning surfaces and can be replaced with each other, the positioning process is simple and convenient, and is more suitable for engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention.

[0023] Figure 2 It is the process of forming a lemniscate.

[0024] Figure 3 yes Figure 1 Right side view.

[0025] Figure 4 yes Figure 3 A partial enlarged view of .

[0026] Figure 5 yes Figure 3 Top view of the .

[0027] Figure 6 It is the test layout diagram of the probe.

[0028] Wherein: 1 - probe head, 2 - probe rod, 3 - cylinder, 4 - lemniscate of Bernoulli of revolution, 5 - inclined hole, 6 - dynamic pressure sensor, 7 - cable of dynamic pressure sensor, 8 - positioning block, 9 - cuboid base, 10 - cylindrical boss, 11 - through hole, 12 - threaded hole, 13 - countersunk head screw, 14 - fan casing, 15 - rotor, 16 - stator, 17 - fan hub. Detailed implementation mode

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

[0030] As Figure 1 shown, in this embodiment, a three-dimensional dynamic boundary layer probe for measuring the hub between the rotating and static parts of a fan is introduced, which is composed of a probe head (1), a rod (2), a dynamic pressure sensor (6), and a positioning block (8). It is characterized in that: the probe head (1) is a cylinder (3) and a lemniscate of Bernoulli of revolution (4) with a common bottom surface. The connection between the cylinder (3) and the lemniscate of Bernoulli of revolution (4) has a smooth curved surface transition. A dynamic pressure sensor (6) is encapsulated in the probe head (1). On the surface of the lemniscate of Bernoulli of revolution, a pressure sensing hole (5) is opened, which is an inclined hole (5). The inclined hole (5) is communicated with the dynamic pressure sensor (6) encapsulated in the probe head (1). The center line of the inclined hole (5) and the axis of the cylinder (3) of the probe head (1) are in the same plane. The axis of the cylinder of the probe head (1) coincides with the axis of the probe rod (2).

[0031] The diameter of the cylinder (3) of the probe head (1) is 2 mm and the length is 10 mm.

[0032] The solid of revolution (4) is formed by rotating the AB curve segment on the lemniscate around the axis L. Point A is the intersection point of the lemniscate, the tangent at point B is perpendicular to the tangent at point A, and the rotation axis L passes through point A and is perpendicular to the tangent at point A.

[0033] The diameter of the inclined hole (5) is 0.3 mm, and the included angle between the center line of the inclined hole (5) and the axis of the cylinder (3) of the probe head (1) is 50°.

[0034] The vertical distance from the center of the inclined hole (5) to the lowest point on the surface of the lemniscate of Bernoulli of revolution (4) is 0.06 mm.

[0035] The probe rod (2) is a cylinder with a diameter of 6 mm. A circular pipe is opened inside it. The cable (7) of the dynamic pressure sensor encapsulated in the probe head (1) is led out of the probe tail through the pipe inside the probe rod (2). A positioning block (8) is sleeved at the probe tail.

[0036] The positioning block (8) is an integral structure, including a cuboid base (9), a cylindrical boss (10), a through hole (11), and a threaded hole (12). It is sleeved on the tail of the probe through the through hole (11) and fixed by countersunk head screws (13) passing through the threaded holes (12) on both sides of the boss (10). The countersunk head screws (13) are completely embedded in the threaded holes (12).

[0037] The cuboid base (9) includes four rectangular sides and two square bottoms. Two adjacent sides among the four sides are perpendicular to each other, and all four sides can be used as positioning surfaces. One bottom surface of the base (9) is connected to the cylindrical boss (10), and the perpendicular bisector of the bottom surface coincides with the axis of the boss (10). The axis of the boss (10) coincides with the center line of the through hole (11). The diameter of the through hole is 6.05 mm, the outer diameter of the boss is 9 mm, the side length of the bottom surface of the base (9) is 11 mm, and the thickness of the base (9) is 3 mm.

[0038] Calibrate the probe in a subsonic calibration wind tunnel. Select one side of the base (9) of the positioning block (8) as the positioning surface. Determine the relative position between the positioning surface of the positioning block (8) and the pressure sensing hole (5) through a spirit level. Fix the positioning block (8) with countersunk head screws (13). Obtain the pneumatic calibration coefficients of the probe at different incoming flow directions and different Mach numbers.

[0039] In actual measurement, install and fix the probe on the displacement mechanism. The specific process is as follows: Use a spirit level to adjust the positioning surface of the displacement mechanism to be horizontal. Install the probe on the displacement mechanism. Place a spirit level on the positioning surface of the positioning block (8) of the probe. Rotate the probe along the axis of the probe strut (2). Adjust the positioning surface to be horizontal through the spirit level. Determine the relative position between the center line of the inclined hole (5) and the positioning surface of the displacement mechanism. Fix the probe on the displacement mechanism; the displacement mechanism for installing the probe is installed on the casing (14) of the fan to be measured through a positioning device. Adjust the displacement mechanism to insert the probe into a certain radial position within the boundary layer of the hub (17) between the fan rotor (15) and the stator (16), as Figure 6 shown. According to the known average incoming flow direction, adjust the probe through the displacement mechanism to align the pressure sensing hole with the average incoming flow direction. Taking this position as the reference, use the displacement mechanism to drive the probe to rotate 3 angles in the counterclockwise and clockwise directions respectively around the axis of the probe strut (2). The angle interval is 15°. A total of 7 angle positions are measured. At each angle position, combined with the pneumatic calibration coefficients of the probe at different incoming flow directions and different Mach numbers obtained from the subsonic calibration wind tunnel, calculate the pitch angle, yaw angle, total pressure, static pressure, and Mach number of the airflow in the measured flow field.

[0040] The present invention has a built-in positioning function. The positioning block (8) adopted has a small size and has little influence on the probe during the measurement process. Since all four side surfaces can be used as positioning surfaces and can be replaced with each other, the positioning process is simple and convenient, making it more suitable for engineering applications. The probe head (1) of the present invention includes a convolute (4). On the one hand, since the vertical distance between the center of the pressure sensing hole (5) and the lowest point on the surface of the convolute (4) is small, the present invention can measure the three-dimensional flow field dynamic parameters inside the boundary layer of the hub (17). On the other hand, the convolute (4) can suppress the separation of the airflow when flowing over its surface, weakening the interference of the flow around the strut head (1) on the internal flow field of the boundary layer. When measuring close to the hub (17), the convolute (4) can suppress the scale of the horseshoe vortex at the front end of the probe head (1). This structure improves the measurement accuracy of the boundary layer flow field of the hub (17). Finally, since the convolute (4) is flat, the dynamic sensor can be installed close to the pressure sensing hole (5), greatly reducing the cavity volume between the pressure sensing hole (5) and the sensor, reducing the cavity effect, and improving the frequency response of the probe. The present invention only includes one pressure sensing hole (5), and only one dynamic pressure sensor (6) is encapsulated in the cylinder (3) of the probe head (1). The diameter of the cylinder (3) of the probe head (1) is relatively small, with little interference to the measured flow field, having a high spatial resolution, and can be inserted between the fan rotor (15) and the stator (16) to measure the dynamic changes of the airflow pitch angle, airflow yaw angle, total pressure, static pressure, and Mach number of the three-dimensional flow field of the boundary layer of the hub (17).

Claims

1. A method of using a three-dimensional dynamic boundary layer probe for measuring the hub between a fan rotor and a stator to achieve the dynamic variation of three-dimensional flow field parameters within the boundary layer of the hub. The flow field parameters include the pitch angle of the air flow, the yaw angle of the air flow, total pressure, static pressure, and Mach number. The structure of the three-dimensional dynamic boundary layer probe for measuring the hub between a fan rotor and a stator used is composed of a probe head (1), a strut (2), a dynamic pressure sensor (6), and a positioning block (8), and is characterized in that: The probe head (1) is a co-planar cylinder (3) and a surface of revolution formed by a lemniscate, with a smooth surface transition at the connection between the cylinder (3) and the surface of revolution formed by the lemniscate. A dynamic pressure sensor (6) is encapsulated inside the probe head (1). On the surface of the surface of revolution formed by the lemniscate, an inclined hole (5) is provided as a pressure sensing hole. The inclined hole (5) communicates with the dynamic pressure sensor (6) encapsulated inside the probe head (1). The center line of the inclined hole (5) and the axis of the cylinder (3) of the probe head (1) are in the same plane, and the axis of the cylinder of the probe head (1) coincides with the axis of the probe strut (2). The diameter of the cylinder (3) of the probe head (1) is d, and the value range is 1.5 mm ≤ d ≤ 2.3 mm, with a length of 4d to 8d. The surface of revolution (4) is formed by rotating the AB curve segment on the lemniscate around the axis L. Point A is the intersection point of the lemniscate, and the tangent line at point B is perpendicular to the tangent line at point A. The rotation axis L passes through point A and is perpendicular to the tangent line at point A. The diameter of the inclined hole (5) is 0.2 mm to 0.4 mm. The included angle between the center line of the inclined hole (5) and the axis of the cylinder (3) of the probe head (1) is θ, and the value range is 0° ≤ θ < 90°. The vertical distance from the center of the inclined hole (5) to the lowest point on the surface of the surface of revolution formed by the lemniscate is h, and the value range is 0d ≤ h < 0.29d. The probe strut (2) is a cylinder with a diameter of D, and the value range is 4 mm ≤ D ≤ 10 mm. A circular pipe is provided inside it. The cable (7) of the dynamic pressure sensor encapsulated inside the probe head (1) is led out of the probe tail through the pipe inside the probe strut (2). A positioning block (8) is sleeved on the probe tail. The positioning block (8) is an integral structure, including a rectangular base (9), a cylindrical boss (10), a through hole (11), and a threaded hole (12). It is sleeved on the probe tail through the through hole (11) and fixed by a countersunk head screw (13) passing through the threaded holes (12) on both sides of the boss (10). The countersunk head screw (13) is completely embedded in the threaded hole (12). The rectangular base (9) includes four rectangular sides and two square bottoms. Among the four sides, two adjacent sides are perpendicular to each other, and all four sides can be used as positioning surfaces. One bottom surface of the base (9) is connected to the cylindrical boss (10), and the perpendicular bisector of the bottom surface coincides with the axis of the boss (10). The axis of the boss (10) coincides with the center line of the through hole (11). The diameter of the through hole is D + 0.05 mm. The outer diameter of the boss is M, and the value range is D + 2 mm ≤ M ≤ D + 5 mm. The side length of the bottom surface of the base (9) is M to M + 3 mm, and the thickness of the base (9) is H, and the value range is 2 mm ≤ H ≤ 5 mm. The probe is calibrated in a subsonic calibration wind tunnel. One side of the base (9) of the positioning block (8) is selected as the positioning surface. The relative position between the positioning surface of the positioning block (8) and the inclined hole (5) is determined by a spirit level, and the positioning block (8) is fixed by the countersunk head screw (13). Under different oncoming flow directions and different Mach numbers, the aerodynamic calibration coefficients of the probe are obtained. The using steps are as follows. The first step: Use a level to adjust the level of the positioning surface of the displacement mechanism. Install the probe on the displacement mechanism. Place the level on the positioning surface of the probe positioning block (8). Rotate the probe along the axis of the probe support rod (2). Adjust the level of the positioning surface through the level to determine the relative position between the center line of the inclined hole (5) and the positioning surface of the displacement mechanism. Fix the probe on the displacement mechanism. The second step: Install the displacement mechanism with the probe on the casing (14) of the fan to be measured through the positioning device. Adjust the displacement mechanism to insert the probe into a certain radial position within the boundary layer of the hub (17) between the fan rotor (15) and the stator (16). According to the known average oncoming flow direction, adjust the probe through the displacement mechanism to align the pressure sensing holes with the average oncoming flow direction. The third step: Taking this position as the reference, use the displacement mechanism to drive the probe to rotate 3 angles in the counterclockwise and clockwise directions respectively around the axis of the probe support rod (2). The angle interval is 10° to 20°, and a total of 7 angle positions are measured. The fourth step: At each angle position, combine the probe aerodynamic calibration coefficients obtained in the subsonic calibration wind tunnel under different oncoming flow directions and different Mach numbers to calculate the pitch angle, yaw angle, total pressure, static pressure and Mach number of the airflow in the flow field to be measured.

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