Variable incoming flow Mach number wind tunnel test method

Abstract

The invention discloses a variable incoming flow Mach number wind tunnel test method. The method comprises the following steps: firstly, acquiring throttling characteristics of related performance parameters of an outlet section of an air inlet channel under different Mach number working conditions; then, lip adjusting and throttling plug cone moving strategies are designed according to the requirements of a downstream engine; and finally, in the variable Mach number wind tunnel test process, the positions of the lip and the throttling cone are synchronously coupled and adjusted. The test method can ensure that the precursor shock wave and the lip are always in a sealed state under the variable incoming flow condition, reduce the overflow resistance, improve the flow capture capability, and adjust the related performance parameters of the outlet section of the air inlet to be stabilized in an expected range by changing the blockage ratio of the air inlet. And real-time matching of the air inlet channel and a downstream engine in the whole acceleration and deceleration transient process is achieved.

Description

Technical Field

[0001] This application relates to an adjustable inlet variable Mach number wind tunnel test method, belonging to the field of wind tunnel test method design and flow field control. Background Technology

[0002] Air-breathing hypersonic vehicles are hailed as the third revolution in the world's aerospace industry, following propeller-driven and jet aircraft, and represent a major strategic development direction for future civilian and military aircraft. Air-breathing hypersonic vehicles are characterized by a wide flight envelope, spanning subsonic, transonic, and supersonic speeds, up to hypersonic (Ma>5), with flight airspace typically ranging from 0 to 40 km or higher. The use of combined propulsion systems gives hypersonic vehicles the advantages of reusability, high durability and safety, low operating costs, and flexible launch and landing points. Therefore, they can be applied to hypersonic passenger aircraft, reconnaissance aircraft, bombers, or missiles, and can also provide platforms for space exploration and reusable space transportation. It is evident that the development of hypersonic vehicle technology has significant implications for the economy, military operations, and strategic defense.

[0003] As a crucial component of air-breathing propulsion systems, the air inlet primarily undertakes the task of decelerating and pressurizing high-altitude incoming airflow to achieve high aerodynamic performance with minimal total pressure loss. With the development of hypersonic vehicles, to achieve wide-speed-range and wide-airspace flight, the air inlet needs to address issues such as the inability to start when transitioning from subsonic to supersonic speeds, and surge problems caused by changes in engine throttle levers and high-pressure forward transmission from downstream. Therefore, the air inlet needs to maintain stable operation under varying flight conditions, and during wide-speed-range flight, it must meet the requirements of downstream engine parameters such as flow rate, total pressure recovery coefficient, and combustion chamber inlet Mach number to achieve efficient inlet-engine matching. Currently, there are no reported experimental methods for the inlet-engine matching process of adjustable geometry air inlets conducted in variable Mach number wind tunnels; therefore, this paper provides a detailed explanation of such experimental methods. Summary of the Invention

[0004] To address the problems existing in the prior art, this application aims to provide a wind tunnel test method for variable Mach number in an adjustable inlet duct. By adjusting the position of the throttle cone and changing the blockage ratio at the inlet duct outlet, the back pressure fluctuations during changes in the downstream engine throttle lever can be simulated. This method can stabilize the relevant performance parameters at the inlet duct outlet within a certain range during the acceleration and deceleration of the aircraft, thus meeting the requirements of the downstream engine.

[0005] The implementation steps of this invention are as follows:

[0006] A wind tunnel testing method for variable Mach number wind tunnel tests, wherein the wind tunnel tests include throttling characteristic tests at different Mach numbers, and the specific steps of the throttling characteristic tests are as follows:

[0007] S1 keeps the wind tunnel running at the set Mach number and adjusts the lip position to the corresponding incoming Mach number.

[0008] S2 advances the throttling cone multiple times, gradually bringing it into the throttling channel, and collects data on the intake duct flow status.

[0009] S3 will repeatedly retract the throttle cone to gradually remove it from the throttle channel until the intake manifold returns to its normal flow state;

[0010] S4 Analyze the test results and check whether the relevant performance parameters of the inlet outlet section under each cone position meet the expected values; if there is no cone position that meets the expected values, adjust the inlet cone strategy and test again under the current incoming Mach number; if there is a cone position that meets the expected values, end the throttling characteristic test under the current constant Mach number incoming flow, and repeat steps S1-S3 under the new operating conditions to obtain the throttling characteristics of the relevant performance parameters under different incoming Mach numbers;

[0011] S5 designs throttling cone entry strategies for different operating conditions based on the throttling characteristics of relevant performance parameters under different incoming Mach numbers.

[0012] Furthermore, the wind tunnel test also includes a three-variable synchronous coupling adjustment test under varying Mach numbers. The specific steps of the three-variable synchronous coupling adjustment test are as follows:

[0013] Before the wind tunnel test begins, the lip position is adjusted to correspond to the initial Mach number of the wind tunnel, and the throttling cone is moved back to the inlet flow state.

[0014] After the wind tunnel is started, it is kept running at the initial Mach number for a period of time. The moving throttling cone ensures that it runs to the specified position at the current incoming Mach number according to the result of step S5.

[0015] Then, the incoming Mach number is changed, and the inlet lip and throttling cone are moved simultaneously so that the lip position always matches the incoming Mach number, and the downstream back pressure generated by the throttling cone can always decelerate and pressurize the inlet outlet airflow to the desired level according to the result of step S5.

[0016] Furthermore, the distance the blocking cone enters is related to the intake's resistance to back pressure and the expected values ​​of relevant performance parameters at the intake outlet.

[0017] As a preferred embodiment of this application, the relevant performance parameters of the intake outlet include the total pressure recovery coefficient of the outlet section, the Mach number of the outlet section, and the pressure boost ratio of the outlet section.

[0018] Furthermore, during the variable Mach number test, by synchronously coupling and adjusting the position of the intake lip and the blockage ratio, the relevant performance parameters of the intake outlet section are stabilized within a certain range to meet the requirements of downstream engines.

[0019] Beneficial effects:

[0020] According to the technical solution provided in this application, the throttling characteristics of relevant performance parameters under various Mach number conditions within a certain range of incoming Mach number can be obtained. Furthermore, the three-variable coupling adjustment process under varying incoming Mach number, varying inlet geometry, and varying blockage ratio during the acceleration and deceleration of the aircraft can be simulated, thereby achieving performance parameter matching between the inlet and the downstream engine in various flight transients. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a wind tunnel test model for an adjustable-lip, internally rotating air intake with variable Mach number.

[0022] In the diagram, 1 is the bulge front body, 2 is the integrated mechanism of the lip cover and side plate, 3 is the isolation section, 4 is the intake duct outlet section, 5 is the intake duct throttling section, and 6 is the throttling plug cone.

[0023] Figure 2 This is a linear relationship graph showing the change of the outlet cross-section Mach number with increasing blockage ratio under different incoming Mach numbers;

[0024] Among them, Ma e The Mach number at the inlet outlet section is represented by TR, the inlet blockage ratio is represented by Ma0, and the Mach number of the incoming flow during the wind tunnel test is represented by Ma0.

[0025] Figure 3 This is a linear relationship diagram showing the change of the intake outlet Mach number as the incoming flow Mach number increases under the coupled control of the lip and throttling cone. Detailed Implementation

[0026] To facilitate understanding of the present invention, the experimental method will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and should not be construed as limiting the present invention.

[0027] The air intake duct of this invention mainly consists of four parts, as detailed in the appendix. Figure 1The components are: 1-bulge forebody, 2-integrated lip and side plate mechanism, 3-isolation section, and 5-throttling section. The bulge forebody and isolation section are fixed. The integrated lip and side plate mechanism features a swept-back design and can move forward and backward along the flow path. Its purpose is to maintain the seal between the lip and the forebody shock wave, increasing flow capture and reducing overflow loss and overflow drag. Section 4 is the inlet outlet section, and the performance parameters on this section are the key measurement targets in this wind tunnel test. The throttling cone 6 can also move forward and backward along the flow path, simulating the downstream back pressure fluctuations during actual flight when the engine throttle changes by altering the downstream blockage ratio TR.

[0028] The waverider forebody (bulge forebody) has a groove, allowing the integrated lip and swept side plate to move along a preset trajectory; the integrated lip and swept side plate are embedded into the aircraft fuselage through the groove of the bulge forebody and can move along the groove driven by a motor or electric motor; the (variable cross-section) isolation section is connected to the forebody and has a drainage channel between it and the integrated lip and side plate mechanism, the size of which is determined by the relative position of the integrated lip.

[0029] Furthermore, driven by an electric motor (electric steel), the integrated component of the lip and side plate moves along the slide groove. This not only allows the intake manifold contraction ratio to change according to a given pattern, thus avoiding intake manifold inaction caused by flow congestion in the internal pressure section, but also creates a venting slot with varying area at the inlet cross-section of the isolation section. This allows excess airflow to be discharged, meeting the engine's flow requirements under different operating conditions. In addition, the change in the lip position at different incoming Mach numbers can achieve perfect matching with the forebody shock wave, increasing flow capture.

[0030] Specifically, the movable integrated lip and swept-back sideplate, relative to the fuselage, can be adjusted forward and backward along the streamline direction according to the tilt angle of the forebody shock wave at different incoming Mach numbers and the target flow capture requirements at the inlet of the air intake. When the incoming Mach number is the highest in the design velocity range, the movable mechanism is located at the rearmost position along the flow direction. At this time, the upper wall of the smallest cross-section of the movable lip is completely in contact with the upper wall of the inlet cross-section of the isolation section, and there is no venting gap in the inner flow channel. As the incoming Mach number decreases, in order to ensure a good sealing of the forebody shock wave, the movable mechanism gradually moves forward, and the moving distance is determined by the position of the forebody shock wave. As the movable lip moves forward, the distance between the upper wall of the inlet cross-section of the isolation section and the upper wall of the movable lip gradually increases, thus forming a venting gap. The increase in the area of ​​the venting gap can discharge excess airflow, thereby solving the problem of throat blockage at low incoming Mach numbers. When the incoming Mach number drops to the lowest point in the design speed range, the movable lip is located at the front limit position along the flow direction. At this time, the air intake duct has a small contraction, and part of the airflow flowing into the compression section overflows from the vent, which can ensure that the air intake duct starts successfully.

[0031] The inlet model of this invention was tested in a variable Mach number wind tunnel. This testing method is applicable to acceleration and deceleration processes in wind tunnel tests with any variable Mach number. Based on the above-described inlet structure, the incoming Mach number of this wind tunnel varies from Ma2 to Ma4. This wind tunnel test includes an acceleration process from Ma2 to Ma4, a deceleration process from Ma4 to Ma2, and a throttling process at a certain incoming Mach number. Due to space limitations, this paper only briefly describes the relevant test processes and results. This testing method is applicable to acceleration and deceleration processes in wind tunnel tests with any variable Mach number; the variable incoming Mach number wind tunnel testing method of this application includes the following steps:

[0032] (1) First, keep the wind tunnel running at a certain Mach number and adjust the lip position to the corresponding incoming Mach number. At this time, the throttling cone should be as far away from the outlet section of the throttling section as possible so that the entire intake is in a flow state (the intake blockage ratio is 0).

[0033] (2) Under the conditions of step (1), advance the throttling cone multiple times to gradually enter the throttling channel. After each cone movement, wait for a period of time to collect data. The distance the cone enters (intake blockage ratio) is related to the intake's back pressure resistance and the expected values ​​of relevant performance parameters at the intake outlet.

[0034] (3) After completing step (2), retract the throttling cone multiple times to gradually remove it from the throttling channel until the intake channel returns to flow. After each cone movement, wait for a period of time before collecting data.

[0035] (4) Analyze the test results and check whether the relevant performance parameters of the inlet outlet section under each cone position meet the expected values. If there is no cone position that meets the expected values, adjust the inlet cone strategy and test again under the current incoming Mach number; if there is a cone position that meets the expected values, end the throttling characteristic test under the current fixed Mach number incoming flow, and repeat steps (1) to (4) under the new operating conditions to obtain the throttling characteristics of the relevant performance parameters under different incoming Mach numbers.

[0036] (5) After obtaining the throttling characteristics of the relevant performance parameters under each incoming Mach number, design the throttling and blocking cone entry strategy under different working conditions according to actual needs.

[0037] (6) Before the wind tunnel test with variable Mach number begins, the lip position is adjusted to correspond to the initial Mach number of the wind tunnel, and the throttling cone is moved back to the inlet flow state.

[0038] (7) After the wind tunnel is started, maintain the initial Mach number for a period of time, move the throttling cone and ensure that it runs to the specified position under the current incoming Mach number according to the result of step (5).

[0039] (8) After completing step (7), the wind tunnel begins to change the incoming Mach number. At this time, the inlet lip and the throttling cone are moved simultaneously so that the lip position always matches the incoming Mach number, and the downstream back pressure generated by the throttling cone can always decelerate and pressurize the airflow at the inlet outlet to the desired level according to the result of step (5).

[0040] Example:

[0041] The specific experimental steps of this invention are as follows:

[0042] (1) When the wind tunnel starts at Mach number 2, adjust the integrated mechanism of the lip and side plate to keep the lip and the front shock wave matched. At the same time, move the throttling cone back to a position slightly downstream of the throttling section outlet section to keep the intake in a flow state.

[0043] (2) The wind tunnel is kept running at Mach number 2. The throttling cone is advanced step by step multiple times to increase the intake blockage ratio TR to 6.67%, 13.33%, 20.00%, 26.67%, 33.33%, 40.00%, 46.67% and 53.33% respectively. Then the throttling cone is moved back to the flow state (TR = 0.00%).

[0044] (3) The wind tunnel accelerates from Mach 2 to Mach 3, while the lip cover and side plate integrated mechanism retracts to the Mach 3 operating position. During this period, the throttling cone remains stationary, and the intake duct is always in a flow state.

[0045] (4) The wind tunnel is kept running at Mach number 3. The throttling cone advances gradually multiple times, increasing the intake blockage ratio TR to 13.33%, 26.67%, 40.00% and 53.33% respectively. Then the throttling cone is moved back to the flow state (TR = 0.00%).

[0046] (5) Accelerate the wind tunnel from Mach 3 to Mach 4, repeat the operations in steps (3) and (4), and complete the process of collecting the throttling characteristics under Mach 4 conditions.

[0047] (6) Analyze and organize the throttling characteristic data collected at incoming Mach numbers of 2, 3, and 4, and organize them into curves as follows: Figure 2 As shown. According to the Mach number requirement of the inlet outlet section in this embodiment of the invention, it is necessary to maintain Mach number at all times during acceleration. e Since the value is in the range of 0.35 to 0.45, the corresponding TR for the three operating conditions Ma0 = 2, 3 and 4 should be set to 46.67%, 53.33% and 60.00% respectively.

[0048] (7) The "three-variable" coupled wind tunnel test is started. At the initial moment, the wind tunnel is still started at Mach 2 with the incoming flow, and the initial positions of the lip and throttle cone are the same as those in step (1). However, during the period when the wind tunnel is started and Mach 2 is maintained, the throttle cone needs to advance rapidly, so that the intake blockage ratio rises to 46.67%.

[0049] (8) The wind tunnel flow begins to accelerate from Mach 2 to Mach 3. During this acceleration process, the lip and side plate integrated mechanism and the throttling cone are controlled simultaneously to make the lip move back from the Mach 2 position to the Mach 3 position, while the throttling cone moves forward to the position with a blockage ratio of 53.33%.

[0050] (9) During the acceleration of the wind tunnel airflow from Mach 3 to Mach 4, repeat step (8) to move the lip from the Mach 3 position to the Mach 4 position, while simultaneously controlling the throttle cone to advance to a position with a blockage ratio of 60.00%. This completes the "three-change" synchronous coupling adjustment operation of adjusting the intake lip position and changing the blockage ratio during the acceleration from Mach 2 to Mach 4, achieving matching between the intake duct and the downstream engine regarding the intake duct outlet Mach number, and satisfying the Mach requirement. e The requirement is to always maintain a value within the range of 0.35 to 0.45, such as Figure 3 As shown.

[0051] The above embodiment is only a specific example of the present invention, demonstrating that the throttling characteristics of the relevant performance parameters of the inlet outlet section under different incoming Mach numbers can be successfully obtained through this experimental method. Then, through data processing and result analysis, the adjustment law of the lip and throttling cone during the wind tunnel process of varying incoming Mach numbers is designed to achieve the matching of the performance parameters of the inlet and the downstream engine.

[0052] Obviously, the experimental method described in this invention is applicable to the acceleration and deceleration processes of wind tunnel tests with arbitrary Mach numbers, and can achieve the Mach numbers in addition to those in this acceleration embodiment. e The upstream and downstream matching of any performance parameters other than those specified in this invention. Therefore, any modifications made in accordance with the technical concept proposed in this invention, or based on this technical solution, fall within the protection scope of this invention.

Claims

1. A wind tunnel testing method for variable incoming Mach number, characterized in that, The wind tunnel test includes throttling characteristic tests at different Mach numbers. The specific steps of the throttling characteristic test are as follows: S1 keeps the wind tunnel running at the set Mach number and adjusts the lip position to the corresponding incoming Mach number. S2 advances the throttling cone multiple times, gradually bringing it into the throttling channel, and collects data on the intake duct flow status. S3 will repeatedly retract the throttle cone to gradually remove it from the throttle channel until the intake manifold returns to its normal flow state; S4 Analyze the test results and check whether the relevant performance parameters of the inlet outlet section under each cone position meet the expected values; if there is no cone position that meets the expected values, adjust the inlet cone strategy and test again under the current incoming Mach number; if there is a cone position that meets the expected values, end the throttling characteristic test under the current constant Mach number incoming flow, and repeat steps S1-S3 under the new operating conditions to obtain the throttling characteristics of the relevant performance parameters under different incoming Mach numbers; S5 designs throttling cone entry strategies for different operating conditions based on the throttling characteristics of relevant performance parameters under different incoming Mach numbers.

2. The wind tunnel testing method with variable incoming Mach number according to claim 1, characterized in that, The wind tunnel test also includes a three-variable synchronous coupling adjustment test under varying Mach numbers. The specific steps of the three-variable synchronous coupling adjustment test are as follows: Before the wind tunnel test begins, the lip position is adjusted to correspond to the initial Mach number of the wind tunnel, and the throttling cone is moved back to the inlet flow state. After the wind tunnel is started, it is kept running at the initial Mach number for a period of time. The moving throttling cone ensures that it runs to the specified position at the current incoming Mach number according to the result of step S5. Then, the incoming Mach number is changed, and the inlet lip and throttling cone are moved simultaneously so that the lip position always matches the incoming Mach number, and the downstream back pressure generated by the throttling cone can always decelerate and pressurize the inlet outlet airflow to the desired level according to the result of step S5.

3. A wind tunnel testing method for variable incoming Mach number according to claim 1 or 2, characterized in that, The distance the blocking cone enters is related to the intake's resistance to back pressure and the expected values ​​of relevant performance parameters at the intake outlet.

4. The wind tunnel testing method with variable incoming Mach number according to claim 3, characterized in that, The relevant performance parameters of the intake outlet include the total pressure recovery coefficient of the outlet section, the Mach number of the outlet section, and the pressure boost ratio of the outlet section.

5. A wind tunnel testing method for variable incoming Mach number according to claims 1 and 2, characterized in that, During the variable Mach number test, the relevant performance parameters of the intake duct outlet section are kept within the set range by synchronously and coupledly adjusting the position of the intake duct lip and the blockage ratio, thus meeting the requirements of downstream engines.

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