Engine pneumatic probe closed circuit wind tunnel turntable test fixture

Abstract

The application discloses a kind of engine aerodynamic probe closed wind tunnel rotating window test fixture, it includes disc base, the disc surface of disc base is fixedly connected with the one end of symmetrical wing-shaped support arm, the other end of symmetrical wing-shaped support arm is fixedly connected with the outside wall of cylindrical fairing, disc base, symmetrical wing-shaped support arm and cylindrical fairing are provided with one intercommunication and for installing aerodynamic probe hole, and the hole in symmetrical wing-shaped support arm is the cavity hole matched with the installation part of aerodynamic probe, and the detection part of aerodynamic probe is penetrated in the hole on cylindrical fairing and extends into cylindrical fairing;The scheme is simulated by cylindrical fairing inside flow channel of engine, while the disturbance of aerodynamic probe shape step point is isolated to the pressure measuring hole of aerodynamic probe detection part;Cylindrical fairing front end is designed into annular thin edge tip, can prevent the disturbance of flowing airflow, guarantees the flow field quality of airflow in cylindrical fairing.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology, specifically to a wind tunnel rotating window test fixture for an engine aerodynamic probe. Background Technology

[0002] 1. Wind tunnel test

[0003] Wind tunnels are a very important ground testing facility in the aviation industry. Wind tunnel testing, numerical simulation, and flight testing are the three major methods of aerodynamic research. The theoretical basis of wind tunnel testing is the principle of relativity of motion. In actual flight, the airflow is stationary, and the aircraft moves in the airflow. In a wind tunnel, the aircraft or its components, models, etc., are fixed in the wind tunnel test area, while the airflow is flowing, thus simulating the relative motion between the aircraft and the airflow during flight.

[0004] A product or model requires the selection of a suitable wind tunnel for testing based on the experimental conditions. The main considerations for wind tunnel selection include: the size of the test sample relative to the wind tunnel size, the maximum Mach number tested in the wind tunnel, the flow field quality in the wind tunnel, the installation interface of the test sample, and any special testing requirements. Whether it's an open or closed wind tunnel, there is a test area that meets the flow field quality requirements. The effective test area for a closed wind tunnel is generally in the central region of the test section cross-section, with the specific range determined based on flow field calibration results, roughly 60% to 70% of the cross-section. Open wind tunnels do not have a fixed test section; their effective test area is also determined based on flow field calibration, generally not exceeding 60% of the size of the exit cross-section of the contraction section. The test part of the sample should be located within the effective test area of ​​the wind tunnel.

[0005] 2. Turbulent flow

[0006] Laminar flow is a stable airflow pattern in which the airflow moves along fixed, predictable streamlines, while turbulent flow is an unstable airflow pattern in which there is significant lateral movement and eddies. When laminar airflow flows over the surface of a continuous (streamlined) object with a finite length, it can usually maintain a laminar state of motion. However, when there is a large angle between the direction of continuous change of the object's surface and the direction of the airflow itself, resulting in an excessively large pressure gradient in the downstream direction, it will turn into turbulence or eddies.

[0007] When there are discontinuous step changes on the surface of an object, the airflow is disturbed by the step point and changes drastically, which will form a turbulent and eddy mixed flow near and downstream of the step point. The turbulence is constantly changing and causes continuous and unstable disturbances to the surrounding flow field. The shape of the disturbance is affected by a variety of factors such as the size of the disturbance point, the flow velocity, and the presence of a constraining wall.

[0008] 3. Pneumatic probe inside the engine

[0009] A certain number of aero-engine probes need to be installed inside the engine to measure the total pressure, static pressure and other internal pressures in different areas of the engine. Before each aero-engine probe is installed on the engine, it needs to undergo an aerodynamic consistency test to ensure that it meets the design and manufacturing specifications. The test equipment for conducting aerodynamic consistency tests on the aero-engine probes is the wind tunnel.

[0010] The pneumatic probe inside the engine can be divided into a mounting part and a detection part in terms of its external structure. The mounting part is generally completely fitted into the pre-reserved cavity surface inside the engine and is positioned by means of locating pins and slots. The mounting part is not exposed to the airflow. The probe of the detection part extends into the internal flow channel of the engine to measure the airflow pressure.

[0011] Typically, to ensure proper installation and fit with pre-reserved surfaces inside the engine, the mounting and sensing parts of the pneumatic probe cannot have a continuous change in shape; instead, they contain abrupt changes in shape with sharp edges and corners, resulting in the following defects:

[0012] 1. Because the transition between the pneumatic probe mounting section and the probe section is not smooth, there are abrupt changes in the shape, such as sharp edges or corners (e.g., Figure 5 As shown in the figure), and these shape step points are very close to the pressure measurement holes of the probe section. During wind tunnel testing, if the shape step points are directly exposed to the airflow, turbulence zones will be generated (such as...). Figure 6 (As shown); thus affecting the stability of the flow field around the pressure measuring hole of the probe, and affecting the accuracy of the test.

[0013] 2. Closed-loop wind tunnels are the most common type of wind tunnel both domestically and internationally. These wind tunnels share a common characteristic: a slow-moving boundary layer exists near the tunnel wall surface of the test section. If the aerodynamic probe only extends part of the probe into the test section (e.g., ...), ... Figure 7 As shown in the diagram, the probe will be located within the boundary layer. Since the flow velocity in the boundary layer is much lower than the velocity at the center, and the flow field is non-uniform, this does not meet the test requirements. During the test, the main test area of ​​the sample needs to avoid the boundary layer and be installed in the central area of ​​the test section (effective test area). If the installation part of the pneumatic probe is also extended into the test section (e.g., ...), the probe will be placed within the boundary layer. Figure 8 As shown in the diagram, this exposes the abrupt changes in the shape of the pneumatic probe to the airflow, creating a turbulence zone. This, in turn, affects the measurement accuracy of the probed area.

[0014] 3. Because open wind tunnels lack the constraint of tunnel walls on streamlines, the effective test area that meets flow field requirements is only a very small region between the contraction and diffusion sections. To place the probe portion of the aerodynamic probe within the effective test area of ​​the open test section, even for conventionally sized open wind tunnels, there will be turbulence problems caused by the step-like changes in shape (e.g., ...). Figure 9 (As shown). Summary of the Invention

[0015] To address the aforementioned shortcomings of existing technologies, this invention provides a closed-loop wind tunnel test fixture for engine aerodynamic probes, which solves the problem of difficulty in conducting aerodynamic consistency tests on aerodynamic probes in closed-loop wind tunnels.

[0016] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0017] A closed-window wind tunnel test fixture for an engine aerodynamic probe is provided, comprising a disc base, the disc surface of which is fixedly connected to one end of a symmetrical airfoil support arm, and the other end of which is fixedly connected to the outer wall of a cylindrical fairing. The disc base, the symmetrical airfoil support arm, and the cylindrical fairing are provided with interconnected channels for mounting the aerodynamic probe. The channel located in the symmetrical airfoil support arm is a cavity hole adapted to the mounting part of the aerodynamic probe. The detection part of the aerodynamic probe passes through the channel located in the cylindrical fairing and extends into the cylindrical fairing.

[0018] Furthermore, a frustum-shaped flow-in hole is provided at the front port of the cylindrical fairing. The large-diameter end of the flow-in hole is connected to the outer edge of the front end of the cylindrical fairing and forms an annular thin-edged tip. The small-diameter end of the flow-in hole is smoothly connected to the inner annular surface of the cylindrical fairing.

[0019] Furthermore, the inclination angle of the conical surface of the drainage hole is 20 degrees.

[0020] Furthermore, the axial distance between the channel on the cylindrical fairing and the tip of the annular thin edge is not less than twice the length of the detection part of the pneumatic probe.

[0021] Furthermore, the inner wall shape of the cylindrical fairing is the same as the shape of the internal flow channel wall of the engine at the location where the aerodynamic probe is installed.

[0022] Furthermore, the diameter of the cylindrical fairing is 3-4 times the length of the detection section of the pneumatic probe.

[0023] Furthermore, the axis of the cylindrical fairing is parallel to the disk surface of the disk base, and the disk surface of the disk base is provided with engraving lines, which are perpendicular to the axis of the cylindrical fairing.

[0024] Furthermore, the disc base is fixed to the rotating window interface of the test section with screws.

[0025] Furthermore, the length of the symmetrical airfoil arm is determined based on the boundary layer thickness of the closed test section, and the difference between the length of the symmetrical airfoil arm and the boundary layer thickness of the closed test section is not less than 5 cm.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This scheme uses a cylindrical fairing to simulate the internal flow channel of an engine, while isolating the turbulence generated by the step point of the aerodynamic probe's shape from interfering with the pressure measurement hole of the aerodynamic probe's detection part; the front end of the cylindrical fairing is designed as an annular thin-edged tip, which can prevent the flowing air from generating turbulence and ensure the flow field quality of the airflow inside the cylindrical fairing.

[0028] 2. This solution uses symmetrical airfoil arms to facilitate the installation of aerodynamic probes while keeping the probe's detection portion away from the wind tunnel wall, thus avoiding the influence of the wall boundary layer. Furthermore, the symmetrical airfoil arms' straightening effect on the airflow will not cause excessive interference to the airflow.

[0029] 3. This solution can ensure the installation accuracy of the pneumatic probe and the cylindrical fairing by testing and correcting the angle of the scribe line. For example, the verticality of the scribe line can be ensured by using a plumb line, thereby ensuring the horizontality of the pneumatic probe and the cylindrical fairing. Attached Figure Description

[0030] Figure 1 This is the front view of the engine aerodynamic probe closed-hole wind tunnel rotating window test fixture.

[0031] Figure 2 This is a top view of the engine aerodynamic probe closed-hole wind tunnel rotating window test fixture.

[0032] Figure 3 This is a left view of the engine pneumatic probe closed-hole wind tunnel rotating window test fixture.

[0033] Figure 4 This is a cross-sectional view of a cylindrical fairing.

[0034] Figure 5 This is a simplified diagram of the shape of a pneumatic probe in the prior art.

[0035] Figure 6 This is a schematic diagram of the turbulence zone at the step point of the pneumatic probe.

[0036] Figure 7 This is a schematic diagram showing the installation of the pneumatic probe close to the wall of a closed wind tunnel test section.

[0037] Figure 8 This is a schematic diagram of the installation of a pneumatic probe in the effective testing area of ​​a closed wind tunnel.

[0038] Figure 9 This is a schematic diagram of a pneumatic probe installed in a standard-sized open wind tunnel.

[0039] Among them, 1. Circular base, 2. Symmetrical airfoil support arm, 3. Cylindrical fairing, 301. Annular thin edge tip, 302. Drain hole, 303. Smooth transition area, 4. Pneumatic probe, 5. Grating, 6. Screw. Detailed Implementation

[0040] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0041] like Figure 1 As shown, a closed-window wind tunnel test fixture for an engine aerodynamic probe 4 is provided, which includes a disc base 1. The disc surface of the disc base 1 is fixedly connected to one end of a symmetrical airfoil support arm 2, and the other end of the symmetrical airfoil support arm 2 is fixedly connected to the outer wall of a cylindrical fairing 3. The disc base 1, the symmetrical airfoil support arm 2, and the cylindrical fairing 3 are provided with a channel that is interconnected and used to install the aerodynamic probe 4. The channel located in the symmetrical airfoil support arm 2 is a cavity hole that matches the mounting part of the aerodynamic probe 4. The detection part of the aerodynamic probe 4 passes through the channel located in the cylindrical fairing 3 and extends into the cylindrical fairing 3.

[0042] As an optional implementation, the disc base 1 is fixed to the test section's rotating window interface by screws 6. The axis of the cylindrical fairing 3 is set parallel to the disc surface of the disc base 1. The disc surface of the disc base 1 is provided with a scribe line 5, and the scribe line 5 is set perpendicular to the axis of the cylindrical fairing 3. This solution can ensure the installation accuracy of the angle of the aerodynamic probe 4 and the cylindrical fairing 3 by testing and correcting the angle of the scribe line 5. For example, a plumb line can be used to compare with the scribe line 5 on the disc base 1, and the angle of the wind tunnel rotating window can be rotated until the scribe line 5 is aligned with the direction of the plumb line, thereby ensuring the levelness of the aerodynamic probe 4 and the cylindrical fairing 3.

[0043] As an optional implementation, the length of the symmetrical airfoil support 2 is determined according to the boundary layer thickness of the closed test section, and the difference between the length of the symmetrical airfoil support 2 and the boundary layer thickness of the closed test section is not less than 5cm; so that the position of the detection part of the aerodynamic probe 4 is far away from the wind tunnel wall, thereby avoiding the influence of the boundary layer of the tunnel wall, and the rectification effect of the symmetrical airfoil support on the airflow will not cause excessive interference to the airflow.

[0044] As an optional implementation, the inner wall shape of the cylindrical fairing 3 is the same as the internal flow channel wall shape of the engine at the installation position of the pneumatic probe 4. The cylindrical fairing 3 simulates the internal flow channel of the engine, while isolating the interference of the turbulence generated by the step point of the pneumatic probe 4 on the pressure measuring hole of the detection part of the pneumatic probe 4. The diameter of the cylindrical fairing 3 is 3-4 times the length of the detection part of the pneumatic probe 4. A frustum-shaped flow guide hole 302 is opened at the front port of the cylindrical fairing 3, and the inclination angle of the conical surface of the flow guide hole 302 is... The angle is 20 degrees; the large-diameter end of the drainage hole 302 is connected to the outer edge of the front end of the cylindrical fairing 3 and forms an annular thin-edged tip 301, which can prevent the flowing air from generating turbulence; the axial distance between the channel on the cylindrical fairing 3 and the annular thin-edged tip 301 is not less than twice the length of the detection part of the pneumatic probe 4; the small-diameter end of the drainage hole 302 is smoothly connected to the inner annular surface of the cylindrical fairing 3 to form a smooth transition zone 303, which ensures the stability of the airflow and thus ensures the flow field quality of the airflow inside the cylindrical fairing 3.

Claims

1. A test fixture for a closed-aperture wind tunnel with an engine aerodynamic probe, characterized in that, Includes a disc base (1), the disc surface of which is fixedly connected to one end of a symmetrical airfoil support (2), and the other end of which is fixedly connected to the outer wall of a cylindrical fairing (3). The disc base (1), the symmetrical airfoil support (2), and the cylindrical fairing (3) are provided with a channel that is interconnected and used to install a pneumatic probe (4). The channel located in the symmetrical airfoil support (2) is a cavity hole that matches the mounting part of the pneumatic probe (4). The detection part of the pneumatic probe (4) passes through the channel located in the cylindrical fairing (3) and extends into the cylindrical fairing (3). The axis of the cylindrical fairing (3) is parallel to the disk surface of the disk base (1), and the disk surface of the disk base (1) is provided with engraving lines (5), which are perpendicular to the axis of the cylindrical fairing (3). The length of the symmetrical airfoil support (2) is determined based on the boundary layer thickness of the closed test section, and the difference between the length of the symmetrical airfoil support (2) and the boundary layer thickness of the closed test section is not less than 5 cm.

2. The engine pneumatic probe closed-aperture wind tunnel rotating window test fixture according to claim 1, characterized in that, The cylindrical fairing (3) has a frustum-shaped drainage hole (302) at its front port. The large-diameter end of the drainage hole (302) is connected to the outer edge of the front end of the cylindrical fairing (3) and forms an annular thin-edged tip (301). The small-diameter end of the drainage hole (302) is smoothly connected to the inner annular surface of the cylindrical fairing (3).

3. The engine aerodynamic probe closed-aperture wind tunnel rotating window test fixture according to claim 2, characterized in that, The inclination angle of the conical surface of the drainage hole (302) is 20 degrees.

4. The engine pneumatic probe closed-aperture wind tunnel rotating window test fixture according to claim 2, characterized in that, The axial distance between the channel located on the cylindrical fairing (3) and the annular thin edge tip (301) is not less than twice the length of the detection part of the pneumatic probe (4).

5. The engine pneumatic probe closed-aperture wind tunnel rotating window test fixture according to claim 1, characterized in that, The inner wall shape of the cylindrical fairing (3) is the same as the shape of the internal flow channel wall of the engine at the location where the pneumatic probe (4) is installed.

6. The engine pneumatic probe closed-aperture wind tunnel rotating window test fixture according to claim 1, characterized in that, The diameter of the cylindrical fairing (3) is 3-4 times the length of the detection part of the pneumatic probe (4).

7. The engine pneumatic probe closed-aperture wind tunnel rotating window test fixture according to claim 1, characterized in that, The disc base (1) is fixed to the test section turn window interface by screws (6).

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