An experimental method and device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine

Abstract

The present invention provides an experimental method and device for matching the boundary layer flow of the air inlet with the air intake of an aviation turbojet engine. The relative position of the air inlet and the turbojet engine is adjusted according to the development trend of the actual air inlet boundary layer, so as to find a suitable position to optimize the air intake conditions of the turbojet engine. The influence of the air inlet on the performance of the turbojet engine is measured by using precise control technology, thereby solving the problem of matching the boundary layer flow of the air inlet of the turbojet engine with the air intake of the turbojet engine.

Description

Technical Field

[0001] The invention relates to the field of aviation technology, and in particular to an experimental method and device for matching an inlet boundary layer flow with an aviation turbojet engine inlet. Background Art

[0002] Air has a viscous property, and the viscosity of air is related to temperature. Because of the viscosity of air, when gas flows through an object, it will generate a viscous force, which will hinder the flow of gas and form a layer of low-energy airflow on the surface of the object, called a boundary layer. The thickness of the boundary is not only related to the viscosity of the gas, but also to the roughness of the surface of the object and the airflow speed. Due to the existence of the inlet boundary layer, simply connecting the turbojet engine to the inlet and conducting a joint experiment of the turbojet engine and the inlet will inevitably affect the performance of the turbojet engine. However, the current joint experiment of the turbojet engine inlet does not consider the impact of the boundary layer flow development of the airflow in the inlet on the performance of the turbojet engine, so it is impossible to solve the problem of matching the boundary layer flow of the turbojet engine inlet with the turbojet engine intake. Summary of the invention

[0003] The purpose of the present invention is to provide an experimental method for matching the boundary layer flow of an air inlet duct with the air intake of an aviation turbojet engine, so as to solve the problem of matching the boundary layer flow of an air inlet duct of a turbojet engine with the air intake of a turbojet engine.

[0004] To achieve the above object, the technical solution adopted by the present invention is: to provide an experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine, and the experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine comprises the following steps:

[0005] S1. Install the turbojet engine on the turbojet engine performance test bench according to the turbojet engine requirements to ensure that the thrust T test of the turbojet engine is normal;

[0006] S2. Install the air intake duct in front of the turbojet engine intake, install the slide rail and electric push rod under the air intake duct, where the electric push rod can push the air intake duct to move freely on the slide rail, install other test components, connect and debug, and ensure normal control and testing;

[0007] S3. According to the turbojet engine test requirements, the turbojet engine test conditions are divided into low-speed state, cruising state, and high-speed state, and the speeds of the turbojet engine in the three states are respectively taken for experiments according to the turbojet engine working conditions;

[0008] S4. The turbojet engine is in a low speed state as the turbojet engine test speed. The engine is located outside the actual working length of the inlet duct, so that the boundary layer of the inlet duct is fully developed, and the wall boundary layer thickness at different positions of the same longitudinal section of the inlet duct is measured;

[0009] S5, repeating step S4, respectively measuring the boundary layer thickness of the inlet wall surface when the turbojet engine is in a cruising state and a high-speed state, and recording the data;

[0010] S6. Based on the experimental data of steps S4 and S5, a model for estimating the thickness of the intake duct at different speeds is completed;

[0011] S7, taking the low speed state of the turbojet engine as the experimental speed of the turbojet engine, according to the development trend of the inlet boundary layer obtained in step S6, the electric push rod is controlled to push the inlet along the slide rail, and the relative position of the inlet and the turbojet engine inlet is changed, so that the turbojet engine adjusts the relative position according to the development of the inlet boundary layer, so that the turbojet engine is in the area where the boundary layer is not fully developed; at this time, the thrust T2 of the turbojet engine is measured and recorded;

[0012] S8, repeating step S7, respectively measuring the thrust of the turbojet engine in the cruising state and the high-speed state of the turbojet engine;

[0013] S9. Compare and analyze the thrust data of the turbojet engine measured by steps S7 and S8 with the thrust data recorded by steps S4 and S5 to obtain the parameters affecting the thrust of the turbojet engine by the inlet boundary layer flow.

[0014] In one embodiment, the low speed state, the cruising state, and the high speed state in step S3 are 0.25nmax, 0.5nmax, and 0.75nmax, respectively, where nmax is the maximum allowable speed of the turbojet engine.

[0015] In one embodiment, step S4 specifically includes: taking the intake arc outlet of the intake duct as the zero point as the first measuring point, taking a measuring point at intervals of 0.1L along the airflow direction, L is the length of the intake duct, and the number of measuring points is not less than 5; using a total pressure probe and a probe moving device to measure the thickness of the airflow boundary layer б at the wall at each measuring point; the total pressure probe is connected to the pressure scanning valve system to measure the thickness of the boundary layer б at each measuring point; after recording the data once, the turbojet engine is stopped, and the turbojet engine speed is once again pulled to a low speed state, the data is recorded, repeated multiple times, the average value is calculated, and the turbojet engine thrust T1 parameter is recorded.

[0016] In one embodiment, when the method in step S4 is used to measure the wall boundary layer thickness at different positions of the same longitudinal section of the air inlet duct, the measurement is repeated at least three times under each turbojet engine rotation state.

[0017] In one embodiment, step S6 specifically includes: taking the measuring point position as the horizontal coordinate and the boundary layer thickness as the vertical coordinate, making a boundary layer thickness development curve, estimating the development trend of the boundary layer through the boundary layer thickness curve, and thus judging whether the boundary layer has been fully developed.

[0018] Another object of the present invention is to provide a device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine, which is used to implement the experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine described in any one of the above embodiments, and the device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine comprises:

[0019] A turbojet engine, wherein the turbojet engine is arranged on an engine test bench;

[0020] An air inlet duct, the air inlet duct being movably sleeved on the air inlet end of the turbojet engine;

[0021] A ball bearing slide rail, the ball bearing slide rail is arranged on the bottom side of the air inlet duct, and the ball bearing slide rail is used to support the air inlet duct;

[0022] An electric push rod, one end of which is connected to the turbojet engine, and the other end of which is connected to the air inlet duct, and the electric push rod is used to push the air inlet duct to slide;

[0023] A displacement sensor, the displacement sensor is arranged on the electric push rod and is used to measure the positional relationship between the air inlet and the turbojet engine;

[0024] A plurality of boundary layer thickness measuring devices, wherein the boundary layer thickness measuring devices are linearly and equidistantly arranged on the air inlet;

[0025] An electronic pressure scanning valve, the electronic pressure scanning valve is electrically connected to the boundary layer thickness measuring device, and the electronic pressure scanning valve is used to measure the pressure change of the boundary layer thickness measuring device;

[0026] A pressure calibration device, the pressure calibration device is in communication with the electronic pressure scanning valve, and the pressure calibration device is used to perform pressure calibration on the electronic pressure scanning valve;

[0027] A computer system is electrically connected to the engine test bench, the electric push rod, the displacement sensor, and the electronic pressure scanning valve.

[0028] In one embodiment, the pressure calibration device is a nitrogen cylinder.

[0029] In one embodiment, eight boundary layer thickness measuring devices are disposed on the air inlet duct, and the distance between two adjacent boundary layer thickness measuring devices is 0.1L, where L is the length of the air inlet duct.

[0030] In one embodiment, the boundary layer thickness measuring device comprises:

[0031] A mounting frame, the mounting frame being arranged on an outer surface of the air inlet duct;

[0032] A stepper motor, wherein the stepper motor is arranged on the mounting frame;

[0033] A screw rod, which is rotatably mounted on the mounting frame and is connected to a power output end of the stepping motor;

[0034] A slider, the slider being matched with the screw rod;

[0035] A total pressure probe, one end of which passes through a small hole on the air inlet passage and extends into the air inlet passage, and the total pressure probe is connected to the slider;

[0036] A pressure measuring tube, one end of which is connected to the total pressure probe, and the other end of which is connected to the electronic pressure scanning valve.

[0037] In one embodiment, the total pressure probe is a stainless steel tube with an outer diameter of 1.0 mm and an inner diameter of 0.6 mm.

[0038] One or more of the above technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0039] 1. Since a turbojet engine has an air inlet when installed, the performance of the air inlet directly affects the turbojet engine. However, considering only the total pressure loss of the air inlet can no longer meet the current demand for high performance of the engine. Therefore, the boundary layer flow of the air inlet is also a problem that must be considered in the turbojet engine experiment. The embodiment of the present invention can measure the impact of the dynamic changes of the air inlet boundary layer flow on the performance parameters of the turbojet engine.

[0040] 2. The present invention can estimate the development trend of the thickness of the boundary layer of the inlet duct according to the shapes of the inlet ducts of turbojet engines with different shapes, thereby using precise control technology to measure the impact of the inlet duct on the performance of the turbojet engine, and then solve the problem of matching the boundary layer flow of the turbojet engine inlet duct with the turbojet engine intake.

[0041] 3. Due to the wide speed operating range of the turbojet engine, the flow parameters of the inlet duct change dramatically. Therefore, changing the position of the turbojet engine in the inlet duct can effectively meet the requirements of the inlet duct for the operation of the turbojet engine.

[0042] 4. By measuring the parameters of the inlet boundary layer, the flow field changes in the inlet can be monitored at any time, thereby providing early warning information for the turbojet engine intake and preventing the turbojet engine from being damaged due to uneven intake. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 Produce a boundary layer thickness variation trend curve graph for the data of three different rotation speeds provided by the embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the structure of a device for matching the boundary layer flow of an air inlet with the air inlet of an aviation turbojet engine provided by an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of the installation position of a boundary layer thickness measuring device provided for an embodiment of the present invention;

[0047] Figure 4 A schematic structural diagram of a boundary layer thickness measuring device provided by an embodiment of the present invention.

[0048] The respective reference numerals are as follows:

[0049] 1. Intake duct; 2. Turbojet engine; 3. Electric push rod; 4. Displacement sensor; 5. Boundary layer thickness measuring device; 6. Ball slide; 7. Electronic pressure scanning valve; 8. Pressure calibration device; 9. Computer system; 10. Engine test bench; 51. Total pressure probe; 52. Pressure measuring tube; 53. Stepper motor; 54. Slider; 55. Screw; 56. Mounting frame. DETAILED DESCRIPTION

[0050] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0051] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0052] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0053] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] The present application embodiment provides an experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine, comprising the following steps:

[0055] S1. Install the turbojet engine on the turbojet engine performance test bench according to the turbojet engine requirements to ensure that the thrust T test of the turbojet engine is normal.

[0056] S2. Install the air intake duct in front of the turbojet engine intake, install the slide rail and electric push rod under the air intake duct, where the electric push rod can push the air intake duct to move freely on the slide rail, install other test components, connect and debug, and ensure normal control and testing.

[0057] S3. According to the turbojet engine test requirements, the turbojet engine test conditions are divided into low-speed state, cruising state, and high-speed state, and the speeds of the turbojet engine in the three states are respectively taken for experiments according to the turbojet engine working conditions;

[0058] Optionally, the low-speed state, cruising state and high-speed state are 0.25nmax, 0.5nmax and 0.75nmax respectively, where nmax is the maximum allowable speed of the turbojet engine.

[0059] S4. The turbojet engine is in a low speed state as the turbojet engine test speed. The engine is located outside the actual working length of the inlet duct, so that the boundary layer of the inlet duct is fully developed, and the wall boundary layer thickness at different positions of the same longitudinal section of the inlet duct is measured;

[0060] In detail, step S4 specifically includes: taking the intake arc outlet of the inlet duct as the zero point as the first measuring point, taking a measuring point at an interval of 0.1L along the airflow direction, L is the length of the inlet duct, and the number of measuring points is not less than 5; using a total pressure probe and a probe moving device at each measuring point to measure the thickness of the airflow boundary layer б at the wall; the total pressure probe is connected to the pressure scanning valve system to measure the thickness of the boundary layer б at each measuring point; after recording the data once, the turbojet engine is stopped, and the turbojet engine speed is once again pulled to a low speed state, and the data is recorded, repeated multiple times (at least three times), the average value is calculated, and the turbojet engine thrust T1 parameter is recorded.

[0061] S5. Repeat step S4 to measure the boundary layer thickness of the inlet wall when the turbojet engine is in a cruising state and a high-speed state, respectively, and record the data.

[0062] S6. Based on the experimental data of steps S4 and S5, a model for estimating the thickness of the intake duct at different speeds is completed;

[0063] In detail, step S6 specifically includes: taking the measuring point position as the horizontal coordinate and the boundary layer thickness as the vertical coordinate, making a boundary layer thickness development curve, estimating the development trend of the boundary layer through the boundary layer thickness curve, and thus judging whether the boundary layer has been fully developed.

[0064] S7, taking the low speed state of the turbojet engine as the experimental speed of the turbojet engine, according to the development trend of the inlet boundary layer obtained in step S6, the electric push rod is controlled to push the inlet along the slide rail, and the relative position of the inlet and the turbojet engine inlet is changed, so that the turbojet engine adjusts the relative position according to the development of the inlet boundary layer, so that the turbojet engine is in the area where the boundary layer is not fully developed; at this time, the thrust T2 of the turbojet engine is measured and recorded.

[0065] S8, repeat step S7, respectively measuring the thrust of the turbojet engine in the cruising state and the high-speed state of the turbojet engine.

[0066] S9. Compare and analyze the thrust data of the turbojet engine measured by steps S7 and S8 with the thrust data recorded by steps S4 and S5 to obtain the parameters affecting the thrust of the turbojet engine by the inlet boundary layer flow.

[0067] The embodiment of the present invention can use the above method to estimate the development trend of the inlet boundary layer thickness according to the shapes of turbojet engine inlets of different shapes, thereby using precise control technology to measure the impact of the inlet on the performance of the turbojet engine, and then solve the problem of matching the turbojet engine inlet boundary layer flow and the turbojet engine intake.

[0068] Example 1:

[0069] 1. This implementation is carried out on a micro turbojet engine test bench. The engine inlet outer diameter is 100mm and the maximum speed is 16000 rpm. Therefore, the three engine speeds are: n1 = 0.25*16000 = 4000 rpm, n2 = 0.5*16000 = 8000 rpm, n3 = 0.75*16000 = 12000 rpm. The inlet duct length is 500mm, and the actual working length is 300mm. At the beginning, the engine is at the position of 500mm at the tail end of the inlet duct, the inlet bell mouth is 50mm long and the inner diameter is 102mm.

[0070] 2. Start arranging points from the straight section after the intake of the intake duct, with a spacing of 0.1*500=50mm. Therefore, the measurement points of the intake duct boundary layer thickness are: (starting from the intake duct inlet) the first position is 50mm, the second position is 100mm, the third position is 150mm, the fourth position is 200mm, the fifth position is 250mm, the sixth position is 300mm, the seventh position is 350mm, and the eighth position is 400mm.

[0071] 3. The boundary layer thickness and engine thrust were measured at the turbojet engine speeds of 4000 rpm, 8000 rpm, and 12000 rpm as shown in the following table:

[0072]

[0073] Table 1 (speed 4000 rpm)

[0074]

[0075] Table 2 (speed 8000 rpm)

[0076]

[0077] Table 3 (speed 12000 rpm)

[0078] 4. The boundary layer thickness variation trend curve is made from the data of the three speeds. It can be seen that the boundary layer thickness is basically fully developed after 400mm at 4000 rpm, 350mm at 8000 rpm, and 250mm at 12000 rpm. Figure 1 shown.

[0079] 5. According to the above data, the electric push rod is controlled to control the relative position of the air inlet and the engine to be within 400mm at 4000 rpm, within 350mm at 8000 rpm, and within 250mm at 12000 rpm. The engine thrust T2 is measured when the boundary layer of the engine is not fully developed. The parameters of the influence of the air inlet boundary layer flow on the thrust of the turbojet engine are obtained, and the data table is as follows:

[0080] <![CDATA[0.25n max ]]> <![CDATA[0.5n max ]]> <![CDATA[0.75n max ]]> <![CDATA[T1(N)]]> 107.3 258.3 417.3 <![CDATA[T2(N)]]> 104.2 251.4 413.5 <![CDATA[(T1-T2) / T1×100%]]> 2.8％ 2.6％ 0.9％

[0081] Table 4 (Parameters of influence of inlet boundary layer flow on turbojet engine thrust)

[0082] Another object of the present invention is to provide a device for matching the boundary layer flow of the air inlet 1 with the air inlet of the aircraft turbojet engine 2, which is used to implement the experimental method for matching the boundary layer flow of the air inlet 1 with the air inlet of the aircraft turbojet engine 2 of any of the above embodiments, and the device for matching the boundary layer flow of the air inlet 1 with the air inlet of the aircraft turbojet engine 2 comprises a turbojet engine 2, a computer system 9, a ball slide 6, an electric push rod 3, a displacement sensor 4, a plurality of boundary layer thickness measuring devices 5, an electronic pressure scanning valve 7, a pressure calibration device 8, and an air inlet 1. Among them, the turbojet engine 2 is arranged on an engine test bench 10. The air inlet 1 is movably sleeved at the air inlet end of the turbojet engine 2. The ball slide 6 is arranged on the bottom side of the air inlet 1, and the ball slide 6 is used to support the air inlet 1. One end of the electric push rod 3 is connected to the turbojet engine 2, and the other end of the electric push rod 3 is connected to the air inlet 1, and the electric push rod 3 is used to push the air inlet 1 to slide. The displacement sensor 4 is arranged on the electric push rod 3, and is used to measure the positional relationship between the air inlet 1 and the turbojet engine 2. The boundary layer thickness measuring devices 5 are arranged linearly and equidistantly on the intake duct 1. The electronic pressure scanning valve 7 is electrically connected to the boundary layer thickness measuring device 5, and the electronic pressure scanning valve 7 is used to measure the pressure change of the boundary layer thickness measuring device 5. The pressure calibration device 8 is connected to the electronic pressure scanning valve 7, and the pressure calibration device 8 is used to perform pressure calibration on the electronic pressure scanning valve 7. The computer system 9 is electrically connected to the engine test bench 10, the electric push rod 3, the displacement sensor 4, and the electronic pressure scanning valve 7.

[0083] The turbojet engine 2 is installed on the engine test bench 10, and the air inlet 1 is slidably sleeved on the air inlet end of the turbojet engine 2, and the air inlet 1 and the turbojet engine 2 are connected with an electric push rod 3, so that the air inlet 1 can slide under the thrust of the electric push rod 3, thereby adjusting the positional relationship between the turbojet engine 2 and the air inlet 1. And by arranging a ball slide rail 6 below the air inlet 1, the air inlet 1 is supported by the ball slide rail 6, so that the electric push rod 3 can adjust the position of the air inlet 1 more smoothly. The displacement sensor 4 is arranged on the electric push rod 3, and the displacement sensor 4 measures the relative position between the air inlet 1 and the turbojet engine 2 by monitoring the state of the electric push rod 3. The boundary layer thickness measurement of the air inlet 1 is completed by the boundary layer thickness measurement device 5, and the boundary layer thickness measurement device 5 is connected to the electronic pressure scanning valve 7, and the pressure change of the boundary layer is measured by the electronic pressure scanning valve 7. The pressure calibration device 8 is used to provide online calibration pressure to the electronic pressure scanning valve 7 (the pressure calibration device 8 can be a nitrogen bottle). The turbojet engine 2 and other measurement parameters are all measured and controlled by the computer system 9.

[0084] In one embodiment, in order to measure the development of the boundary layer along the air inlet duct 1, 8 boundary layer thickness measuring devices 5 are arranged on the air inlet duct 1, and the distance between two adjacent boundary layer thickness measuring devices 5 is 0.1L, where L is the length of the air inlet duct 1. The development of the boundary layer thickness of the air inlet duct 1 can be estimated based on the measurement parameters at the 8 points.

[0085] In one embodiment, the boundary layer thickness measuring device 5 includes a mounting frame 56, a stepper motor 53, a screw, a pressure measuring tube 52, a total pressure probe 51 (optionally, the total pressure probe 51 can be a stainless steel tube with an outer diameter of 1.0 mm and an inner diameter of 0.6 mm), and a slider 54. The mounting frame 56 is arranged on the outer surface of the air intake duct 1. The stepper motor 53 is arranged on the mounting frame 56. The screw can be rotatably arranged on the mounting frame 56, and the screw is connected to the power output end of the stepper motor 53. The slider 54 is matched with the screw (one end of the slider 54 can be slidably matched with the mounting frame 56, so that when the screw rotates, the slider 54 drives the total pressure probe 51 to move up and down), one end of the total pressure probe 51 passes through a small hole (the diameter of the small hole can be 2 mm) opened on the air intake duct 1, and extends into the air intake duct 1, and the total pressure probe 51 is connected to the slider 54. One end of the pressure measuring tube 52 is connected to the total pressure probe 51, and the other end of the pressure measuring tube 52 is connected to the electronic pressure scanning valve 7. The stepper motor 53 drives the lead screw 55 to rotate, so that the slider 54 moves along the axial direction of the lead screw 55. The total pressure probe 51 is fixedly connected to the slider 54 and can move with the slider 54. The moving distance of the total pressure probe 51 can be accurately calculated by the number of steps of the stepper motor 53 and the pitch of the lead screw 55, so that the thickness of the boundary layer can be measured by the change of the total pressure of the airflow.

[0086] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine, characterized in that: The experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine comprises the following steps: S1. Install the turbojet engine on the turbojet engine performance test bench according to the turbojet engine requirements to ensure that the thrust T test of the turbojet engine is normal; S2. Install the air intake duct in front of the turbojet engine intake, install the slide rail and electric push rod under the air intake duct, where the electric push rod can push the air intake duct to move freely on the slide rail, install other test components, connect and debug, and ensure normal control and testing; S3. According to the turbojet engine test requirements, the turbojet engine test conditions are divided into low-speed state, cruising state, and high-speed state, and the speeds of the turbojet engine in the three states are respectively taken for experiments according to the turbojet engine working conditions; S4. The turbojet engine is in a low speed state as the turbojet engine test speed. The engine is located outside the actual working length of the inlet duct, so that the boundary layer of the inlet duct is fully developed, and the wall boundary layer thickness at different positions of the same longitudinal section of the inlet duct is measured; S5, repeating step S4, respectively measuring the boundary layer thickness of the inlet wall surface when the turbojet engine is in a cruising state and a high-speed state, and recording the data; S6. Based on the experimental data of steps S4 and S5, a model for estimating the thickness of the intake duct at different speeds is completed; S7, taking the low speed state of the turbojet engine as the experimental speed of the turbojet engine, according to the development trend of the inlet boundary layer obtained in step S6, the electric push rod is controlled to push the inlet along the slide rail, and the relative position of the inlet and the turbojet engine inlet is changed, so that the turbojet engine adjusts the relative position according to the development of the inlet boundary layer, so that the turbojet engine is in the area where the boundary layer is not fully developed; at this time, the thrust T2 of the turbojet engine is measured and recorded; S8, repeating step S7, respectively measuring the thrust of the turbojet engine in the cruising state and the high-speed state of the turbojet engine; S9. Compare and analyze the thrust data of the turbojet engine measured by steps S7 and S8 with the thrust data recorded by steps S4 and S5 to obtain the parameters affecting the thrust of the turbojet engine by the inlet boundary layer flow.

2. The experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 1, characterized in that: The low speed state, cruising state and high speed state in step S3 are 0.25nmax, 0.5nmax and 0.75nmax respectively, wherein nmax is the maximum allowable speed of the turbojet engine.

3. The experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 1, characterized in that: Step S4 specifically includes: taking the intake arc outlet of the intake duct as the zero point as the first measuring point, taking a measuring point at intervals of 0.1L along the airflow direction, L is the length of the intake duct, and the number of measuring points is not less than 5; using a total pressure probe and a probe moving device to measure the thickness of the airflow boundary layer б at the wall at each measuring point; the total pressure probe is connected to the pressure scanning valve system to measure the thickness of the boundary layer б at each measuring point; after recording the data once, the turbojet engine is stopped, and the turbojet engine speed is once again pulled to a low speed state, the data is recorded, repeated multiple times, the average value is calculated, and the turbojet engine thrust T1 parameter is recorded.

4. The experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 3, characterized in that: When the method in step S4 is used to measure the wall boundary layer thickness at different positions of the same longitudinal section of the air inlet duct, the measurement is repeated at least three times under each turbojet engine rotation state.

5. The experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 1, characterized in that: Step S6 specifically includes: taking the measuring point position as the horizontal coordinate and the boundary layer thickness as the vertical coordinate, making a boundary layer thickness development curve, estimating the development trend of the boundary layer through the boundary layer thickness curve, and thus judging whether the boundary layer has been fully developed.

6. A device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine, used for implementing the experimental method for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine as described in any one of claims 1 to 5, characterized in that: The device for matching the inlet boundary layer flow with the aviation turbojet engine inlet includes: A turbojet engine, wherein the turbojet engine is arranged on an engine test bench; An air inlet duct, the air inlet duct being movably sleeved on the air inlet end of the turbojet engine; A ball bearing slide rail, the ball bearing slide rail is arranged on the bottom side of the air inlet duct, and the ball bearing slide rail is used to support the air inlet duct; An electric push rod, one end of which is connected to the turbojet engine, and the other end of which is connected to the air inlet duct, and the electric push rod is used to push the air inlet duct to slide; A displacement sensor, the displacement sensor is arranged on the electric push rod and is used to measure the positional relationship between the air inlet and the turbojet engine; A plurality of boundary layer thickness measuring devices, wherein the boundary layer thickness measuring devices are linearly and equidistantly arranged on the air inlet; An electronic pressure scanning valve, the electronic pressure scanning valve is electrically connected to the boundary layer thickness measuring device, and the electronic pressure scanning valve is used to measure the pressure change of the boundary layer thickness measuring device; A pressure calibration device, the pressure calibration device is in communication with the electronic pressure scanning valve, and the pressure calibration device is used to perform pressure calibration on the electronic pressure scanning valve; A computer system is electrically connected to the engine test bench, the electric push rod, the displacement sensor, and the electronic pressure scanning valve.

7. The device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 6, characterized in that: The pressure calibration device is a nitrogen cylinder.

8. The device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 6, characterized in that: Eight boundary layer thickness measuring devices are arranged on the air inlet duct, and the distance between two adjacent boundary layer thickness measuring devices is 0.1L, where L is the length of the air inlet duct.

9. The device for matching the inlet boundary layer flow with the inlet of an aviation turbojet engine according to claim 6, characterized in that: The boundary layer thickness measuring device comprises: A mounting frame, the mounting frame being arranged on an outer surface of the air inlet duct; A stepper motor, wherein the stepper motor is arranged on the mounting frame; A screw rod, which is rotatably mounted on the mounting frame and is connected to a power output end of the stepping motor; A slider, the slider being matched with the screw rod; A total pressure probe, one end of which passes through a small hole on the air inlet passage and extends into the air inlet passage, and the total pressure probe is connected to the slider; A pressure measuring tube, one end of which is connected to the total pressure probe, and the other end of which is connected to the electronic pressure scanning valve.

10. The device for matching the boundary layer flow of the air inlet with the air inlet of an aviation turbojet engine according to claim 9, characterized in that: The total pressure probe is a stainless steel tube with an outer diameter of 1.0 mm and an inner diameter of 0.6 mm.

Images