Inlet isolator flow control device and design method based on the aerodynamic elastic effect of the panel

Abstract

The present invention discloses an inlet isolator flow control device and a design method based on the aeroelastic effect of the panel. First, the selection of the elastic panel material is determined according to the pressure oscillation frequency and amplitude; the geometric dimensions of the elastic panel are determined according to the length and shape of the shock train in the isolator; the initial installation position of the elastic panel is determined according to the position of the first shock wave structure of the shock train. The change in the outlet pressure of the isolator causes the shock train to move back and forth, resulting in areas on the surface of the elastic panel in the isolator where the instantaneous pressure is higher than, equal to, or lower than the pressure in the sealed cavity. The pressure drives the elastic panel to deform and oscillate, enabling the oscillating energy of the shock train to be converted into displacement potential energy and kinetic energy through the elastic panel, thereby achieving the suppression of the shock train oscillation and improving the anti-backpressure ability of the isolator. The present invention can achieve the suppression of the unstable phenomenon of the shock train movement, improve the anti-backpressure ability of the isolator, and expand the working margin of the hypersonic inlet.

Description

Technical Field

[0001] The present invention belongs to the field of aircraft design, and particularly relates to an inlet isolator flow control device and design method based on the panel aeroelastic effect. Background Art

[0002] A scramjet engine mainly consists of a forebody, an inlet, an isolator, a combustion chamber, a nozzle, etc. The isolator is an important aerodynamic component of a supersonic ramjet engine, located between the inlet and the combustion chamber. In addition to the function of further decelerating and pressurizing the hypersonic oncoming flow, it can also isolate the combustion oscillation in the combustion chamber from interfering with the upstream inlet, expand the working range of the inlet, and prevent the inlet from unstarting.

[0003] However, for the internal flow field of the isolator, there are complex shock waves such as shock wave reflection, interaction between shock waves, interference between shock waves and boundary layers, and strong shock wave movement, which make the aerodynamic load and heat flux distribution on the isolator wall more complex. When the aircraft accelerates, a large amount of fuel combustion causes the pressure in the combustion chamber to rise, the reaction at the isolator outlet continuously increases, and there are phenomena such as low-frequency oscillating combustion and continuous change of the inlet angle of attack, all of which will cause the movement of the shock wave train in the isolator and result in complex movement instability phenomena such as oscillation, jump, separation and deflection, and hysteresis, which will pose a certain threat to the stable operation of the engine. Therefore, it is necessary to apply some flow control means in the isolator to suppress the oscillation and jump of the shock wave train and improve the anti-backpressure ability of the isolator. Summary of the Invention

[0004] The present invention provides an inlet isolator flow control device and design method based on the panel aeroelastic effect, which utilizes the aeroelastic effect of the elastic panel to control the movement of the shock wave train in the isolator, thereby avoiding the unstarting of the hypersonic inlet.

[0005] The technical solution to achieve the above object is as follows:

[0006] An inlet isolator flow control device based on the panel aeroelastic effect includes an isolator main body and an elastic panel. A cavity structure is provided on the isolator main body. The cavity structure and the elastic panel form a sealed cavity. The elastic panel is installed between the fairing and the cavity structure. A high-pressure air source for adjusting the pressure in the sealed cavity is arranged outside the sealed cavity, and a valve for controlling air charging and discharging is arranged between the high-pressure air source and the sealed cavity.

[0007] Further, convex platforms and through holes are arranged around the elastic panel. The central region of the inner surface is a cavity. The thickness of the central region of the elastic panel is less than that of the surrounding convex platforms. Threaded holes are arranged around the cavity structure. The elastic panel is connected to the isolator main body by screws passing through the through holes of the elastic panel and the threaded holes around the cavity structure.

[0008] Furthermore, a sealing strip is provided between the periphery of the cavity structure and the boss of the elastic wall panel.

[0009] Furthermore, when the isolation section is not working, the upper surface of the elastic wall panel is flush with the lower wall surface of the isolation section.

[0010] According to the above design method of the inlet duct isolation section flow control device based on the panel aerodynamic elastic effect, the following steps are included:

[0011] Step 1: Determine the material selection of the elastic wall panel according to the oscillation frequency and amplitude of the flow field outlet pressure during the shock train oscillation in the isolation section; Step 2: Determine the geometric dimensions of the elastic wall panel according to the shock train length and asymmetry in the isolation section; Step 3: Determine the initial installation position of the elastic wall panel according to the initial position of the first shock wave in the shock train.

[0012] Furthermore, the specific content of Step 1 is as follows: The compressible unsteady Reynolds-averaged Navier-Stokes equation based on the ALE (Arbitrary Lagrangian Eulerian) method is used to describe the flow field in the isolation section. The k-ω SST turbulence model is adopted for the turbulence model. Based on the finite volume method of structured grids, combined with the third-order MUSCL (Monotone upstream centered schemes for conservation laws) reconstruction format, the AUSMPW+ (Advection upstream splitting method by pressure-based weight functions) format, and the LU-SGS (Lower upper symmetric guassseidel) time discretization method for numerical calculation to obtain the flow field pressure oscillation frequency f and amplitude ΔP during the shock train oscillation in the isolation section under dynamic back pressure. Through the calculation results of the elastic wall panel motion differential equation, select the materials that can realize the deformation of the elastic wall panel under the pressure drive with the oscillation frequency f and amplitude ΔP. The materials include stainless steel, aluminum alloy, titanium alloy, and C / C composite materials.

[0013] Furthermore, the geometric nonlinear problem is considered in the elastic wall panel motion differential equation in Step 1. The periphery of the elastic wall panel is a clamped boundary, and the finite element method is used to solve the elastic wall panel motion equation.

[0014] Further, step 2 is specifically as follows: Based on the motion characteristics of the shock train under dynamic backpressure obtained from numerical simulation, determine the geometric dimensions of the elastic wall panel according to the length and shape of the shock train in the isolator, so that the shock train is within the length range of the elastic wall panel during the movement process.

[0015] Further, the initial position of the shock train in step 3 is: Set the wall pressure ratio threshold α. When the ratio of the wall pressure value P to the oncoming flow static pressure P in reaches the set threshold, that is, P / P in = α, this position is defined as the leading edge position of the shock train and represents the position of the first shock wave of the shock train. The installation initial position is the position of the first shock wave of the shock train under the steady-state solution of the rigid isolator under the same oncoming flow conditions.

[0016] Further, α = 2.

[0017] The beneficial effects of the present invention include: (1), By the deformation and vibration of the elastic wall panel, the suppression of the unstable phenomenon of the shock train movement is realized, which can effectively improve the anti-backpressure ability of the isolator and expand the stable working margin of the supersonic and hypersonic inlets; (2), The present invention is jointly controlled by the sealed cavity and the dynamic backpressure, and is in a flat plate state when the isolator is not working, effectively reducing the resistance; (3), The structure of the present invention is simple and can be adaptively controlled by the oncoming flow conditions. Description of the Drawings

[0018] Figure 1 Flowchart for the design of improving the anti-backpressure ability of the isolator by using the wall panel aeroelastic effect

[0019] Figure 2 Geometric structure schematic diagram of the supersonic inlet and hypersonic inlet based on elastic wall panel control of the present invention.

[0020] Figure 3 Connection schematic diagram of the elastic wall panel and the isolator of the present invention.

[0021] Figure 4 Schematic diagram of the elastic wall panel oscillating and deforming following the flow field.

[0022] Figure 5 Top view of the main concave cavity structure of the isolator.

[0023] Figure 6 Schematic diagram of the deformation state of the elastic wall panel of the present invention.

[0024] Figure 7 Three-dimensional structure diagram of the elastic wall panel.

[0025] Figure 8 Three-dimensional structure diagram of the elastic wall panel.

[0026] Description of the reference numerals:

[0027] 1 - External compression oblique shock wave, 2 - Compression surface of the inlet, 3 - Lip of the inlet, 4 - Inner channel of the inlet, 5 - High - pressure gas source, 6 - Valve for controlling gas charging and discharging, 7 - Sealing cavity, 8 - Sealing strip, 9 - Connecting screw, 10 - Elastic wall panel, 11 - First shock wave of the shock train, 12 - Inner channel of the isolation section, 13 - Fairing, 14 - Main body of the isolation section. Specific implementation mode

[0028] The following further describes in detail a flow control device and design method for an inlet isolation section based on the aero - elastic effect of the wall panel in conjunction with the attached drawings.

[0029] As Figure 2-5 shown, the hypersonic inlet / isolation section structure provided by the present invention with an elastic wall panel includes: the main body 14 of the isolation section and the elastic wall panel 10. The main body 14 of the isolation section is provided with a sealing cavity 7. The pressure in the sealing cavity 7 is controlled by a high - pressure gas source 5 and an air inlet pipe connecting the high - pressure gas source and the sealing cavity 7. A valve 6 for controlling gas charging and discharging is provided on the air inlet pipe. The elastic wall panel 10 is installed between the fairing 13 and the sealing cavity 7. A sealing strip 8 is provided between the convex platforms around the concave cavity structure of the main body 14 of the isolation section and the convex platforms of the elastic wall panel 10, and the elastic wall panel 10 and the main body 14 of the isolation section are sequentially connected by connecting screws 9. The isolation section is composed of a fairing 13 and the main body 14 of the isolation section. As Figure 7 and Figure 8 shown, the elastic wall panel provided by the present invention is provided with convex platforms and through - holes around it, and the inner central area is a concave cavity. The central area of the wall panel is smaller than the convex platforms around it. When the isolation section starts to work, the shock train generated by the interaction between the oncoming shock wave and the boundary layer acts on the area of the elastic wall panel. There is a pressure difference between the upper and lower surfaces of the wall panel, and the wall panel begins to vibrate under forced vibration. The cross - sectional area of the isolation section changes, and the shock train and the separation zone fluctuate with the vibration of the wall panel. When combustion oscillation occurs in the combustion chamber, the pressure in the outlet flow field of the isolation section oscillates periodically, resulting in the reciprocating movement of the shock train in the isolation section. The changing pressure field drives the elastic wall panel to produce small deformations and vibrations, so that the background wave system and the distribution of low - energy flow near the wall surface change, thereby realizing the suppression of the instability of the shock train movement and achieving the improvement of the anti - back - pressure ability of the isolation section.

[0030] The sealing cavity and the isolation section are integrally designed. The height of the cavity is sufficient to accommodate a certain amount of high - pressure gas, so that there is a sufficient pressure difference for deformation between the upper and lower surfaces of the elastic wall panel during operation; when the gas charging and discharging valve is closed, the pressure in the sealing cavity is constant.

[0031] The design method of the flow control device for the inlet isolation section based on the aero - elastic effect of the wall panel of the present invention includes the following steps:

[0032] Step 1: Determine the material selection of the elastic wall panel according to the oscillation frequency and amplitude of the flow field outlet pressure during the oscillation of the shock train in the isolation section; Step 2: Determine the geometric dimensions of the elastic wall panel (10) according to the length and asymmetry of the shock train in the isolation section; Step 3: Determine the initial installation position of the elastic wall panel (10) according to the initial position of the first shock wave of the shock train.

[0033] According to Figure 1 the design flow chart for improving the anti-backpressure ability of the isolation section based on the aeroelastic effect of the wall panel is given. In Step 1, the compressible unsteady Reynolds-averaged Navier-Stokes equations based on the ALE (Arbitrary Lagrangian Eulerian) method are used to describe the internal flow field of the isolation section. The k-ω SST turbulence model is adopted for the turbulence model. Based on the finite volume method of structured grids, combined with the third-order MUSCL (Monotone upstream centered schemes for conservation laws) reconstruction format, the AUSMPW+ (Advection upstream splitting method by pressure-based weight functions) format, and the LU-SGS (Lower upper symmetric guassseidel) time discretization method for numerical calculation. Based on the flow field results of the rigid isolation section under the steady backpressure condition obtained from the numerical simulation, the initial position of the first shock wave 11 of the shock train is obtained. The initial position of the first shock wave 11 of the shock train is determined by the wall pressure rise method, that is, the wall pressure ratio threshold α = 2 is set. When the ratio of the wall pressure value P to the incoming flow static pressure P in reaches the set threshold α, this position is defined as the leading edge position of the shock train and represents the position of the first shock wave 11 of the shock train. The initial position is the position of the first shock wave 11 of the shock train under the steady state solution of the rigid isolation section under the same incoming flow conditions.

[0034] Furthermore, monitoring points are arranged at equal intervals on the wall of the isolation section for numerical simulation. The monitoring points are used to record the time response of the wall pressure at this position in the isolation section. By performing Fourier calculation on the pressure time history of the monitoring points, the flow field pressure oscillation frequency f and amplitude ΔP during the shock train oscillation process in the isolation section under dynamic backpressure are obtained. The motion differential equation of the elastic wall panel considers geometric nonlinear problems. The elastic wall panel is fixed at its four sides, and the finite element method is used to solve the motion equation of the elastic wall panel to analyze the relationship between the motion characteristics of the elastic wall panel and the aerodynamic load it receives: an elastic wall panel material that can achieve obvious deformation is selected under the pressure drive with an oscillation frequency f and an amplitude of ΔP. The selection of the wall panel material is to perform numerical simulations for multiple wall panel conditions (including density, geometric parameters, etc.) under the same flow field conditions and establish a database, and then a suitable material can be selected from the database. The materials of the elastic wall panel include stainless steel, titanium alloy, aluminum alloy, and C / C composite materials, etc.

[0035] Furthermore, based on the motion characteristics of the shock train under dynamic backpressure obtained from numerical simulation, the geometric dimensions of the elastic wall panel are determined according to the length, position, and shape of the shock train in the isolation section, so that the shock train is within the length range of the elastic wall panel during the motion process. In particular, the first shock wave 11 of the shock train can fully act on the elastic wall panel 10. Among them, when the elastic wall panel 10 is installed, it is connected to the isolation section main body 14 by connecting screws 9. A groove is provided on the isolation section main body for installing a sealing strip 8 to ensure good sealing performance of the sealing cavity 7.

[0036] The two-way fluid-structure interaction method is used to perform numerical simulation calculations on the interaction process between the shock train and the elastic wall panel structure in the isolation section to obtain the vibration frequency and amplitude of the elastic wall panel, as well as the deformation shape of the wall panel. As Figure 4 shown, the aerodynamic load on the upper surface of the elastic wall panel 10 comes from the periodically changing flow field pressure in the channel 12 in the isolation section, and the aerodynamic load on its lower surface comes from the pressure in the sealing cavity 7. The pressure in the sealing cavity 7 is controlled by a high-pressure air source 5 and a valve 6 connecting the high-pressure air source and the sealing cavity. The two-way fluid-structure interaction method is used to perform numerical simulation calculations on the interaction process between the shock train and the elastic wall panel structure in the isolation section. When the shock train moves, there will be an area with a high instantaneous pressure. The pressure on the flow field side of the elastic wall panel 10 is higher than the pressure in the sealing cavity 7, and the elastic wall panel 10 deforms downward. The instantaneous high-pressure energy of the air flow is converted into the kinetic energy and elastic potential energy of the elastic wall panel moving downward; in the area with a low instantaneous pressure, the pressure on the flow field side of the elastic wall panel 10 is lower than the pressure in the sealing cavity 7, and the elastic wall panel 10 deforms upward. The pressure potential energy in the cavity is converted into the kinetic energy and elastic potential energy of the elastic wall panel moving upward. As Figure 6As shown, the flexible wall panel vibrates or deforms under the action of the pressure difference between the upper and lower surfaces. The vibration or deformation causes a transient change in the curvature of the wall panel, and the changing wall curvature affects the characteristics such as the breathing motion of the separation bubble and the shock train symmetry under the shock wave / boundary layer interference, thereby realizing the flow control of the shock train in the hypersonic inlet isolator through the aeroelastic effect of the flexible wall panel. On the other hand, the combined structure of the flexible wall panel 10 and the sealing cavity 7 will cause the flow field oscillation energy induced by combustion oscillation to transfer to the flexible wall panel 10 and gradually dissipate, effectively suppressing the unstable phenomenon of the shock train motion in the isolator, thereby improving the anti-backpressure ability of the isolator.

[0037] The working principle of the present invention is as follows: A flexible wall panel is arranged in the isolator. By utilizing the pressure oscillation in the bottom sealing cavity and the flow field pressure under the dynamic backpressure, the flexible wall panel is driven to deform and vibrate, so as to change the background wave system and the distribution of low-energy flow near the wall surface, thereby suppressing the unstable phenomenon of the shock train motion and achieving the improvement of the anti-backpressure ability of the isolator.

[0038] The working process of the above shock train flow control device is as follows:

[0039] When the flow field is not started, the flexible wall panel 10 is in an undeformed state, and its upper surface is flush with the main body 14 of the isolator.

[0040] When the flow field in the flow channel 4 of the inlet runs, the shock train generated by the oncoming flow acts on the area of the flexible wall panel 10, and the high-pressure gas source 5 fills the sealing cavity 7 with gas. Under the action of the pressure difference between the upper and lower wall surfaces, the wall panel begins to deform and vibrate. The deformation state of the flexible wall panel is as Figure 6 , under the action of the instantaneous pressure difference, the wall panel vibrates, resulting in a change in the wall panel curvature. The changing wall curvature affects the characteristics such as the breathing motion of the separation bubble and the shock train symmetry under the shock wave / boundary layer interference, thereby realizing the flow control of the shock train in the hypersonic inlet isolator through the aeroelastic effect of the flexible wall panel.

[0041] The above shows and describes the basic principle, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A design method for an inlet duct isolation section flow control device based on a wall plate aeroelastic effect, the device comprising an isolation section body (14) and an elastic wall plate (10), the isolation section body (14) being provided with a concave cavity structure, the concave cavity structure and the elastic wall plate (10) forming a sealed cavity (7), the elastic wall plate (10) being installed between a fairing (13) and the concave cavity structure, a high-pressure gas source (5) for regulating the pressure in the sealed cavity (7) being provided outside the sealed cavity (7), and a valve (6) for controlling the filling and discharge of gas being provided between the high-pressure gas source (5) and the sealed cavity (7); It is characterized in that The design method comprises the following steps: Step 1: Determine the material selection of the elastic wall plate according to the oscillation frequency and amplitude of the flow field outlet pressure when the shock wave train oscillates in the isolation section; Step 2: Determine the geometric dimensions of the elastic wall plate (10) according to the length and asymmetry of the shock wave train in the isolation section; Step 3: Determine the initial installation position of the elastic wall plate (10) according to the initial position of the first shock wave in the shock wave train.

2. The design method of the inlet isolator flow control device based on the panel aerodynamic elastic effect according to claim 1, characterized in that: The step 1 specifically comprises: using the compressible unsteady Reynolds-averaged Navier-Stokes equations based on the arbitrary Lagrangian Euler (ALE) method to describe the flow field in the isolation section, using the k-ωSST turbulence model as the turbulence model, and performing numerical calculations based on the structured grid finite volume method, combined with the monotonic upwind center method of the third-order conservation law, namely the MUSCL reconstruction format, the upwind splitting method based on the pressure weight function, namely the AUSMPW+ format, and the lower-upper symmetric Gauss-Seidel method, namely the LU-SGS time discretization method, to obtain the flow field pressure oscillation frequency f and amplitude ΔP during the shock wave train oscillation process in the isolation section under dynamic back pressure. Based on the calculation results of the differential equation of motion of the elastic wall panel, materials that can realize deformation of the elastic wall panel under pressure drive with an oscillation frequency f and an amplitude of ΔP are selected, and the materials include stainless steel, aluminum alloy, titanium alloy, and C / C composite material.

3. The design method of the inlet isolator flow control device based on the panel aerodynamic elastic effect according to claim 2, characterized in that: In the step 1, the differential equation of motion of the elastic wall panel (10) takes into account geometric nonlinearity, the elastic wall panel (10) is surrounded by fixed boundaries, and the finite element method is used to solve the equation of motion of the elastic wall panel (10).

4. The design method of the flow control device for the inlet isolator based on the wall panel aerodynamic elastic effect according to claim 3, characterized in that: The step 2 specifically comprises: based on the motion characteristics of the shock wave train under dynamic back pressure obtained by numerical simulation, determining the geometric dimensions of the elastic wall plate (10) according to the length and shape of the shock wave train in the isolation section, so that the shock wave train is within the length range of the elastic wall plate (10) during the motion process.

5. The design method of the inlet isolator flow control device based on the panel aerodynamic elastic effect according to claim 4, characterized in that: The initial position of the shock wave train in step 3 is: set the wall pressure ratio threshold α, when the wall pressure value P is equal to the static pressure P of the incoming flow, in The ratio of P / P in =α, which is defined as the leading edge position of the shock train and represents the position of the first shock wave of the shock train. The initial installation position is the position of the first shock wave of the shock train under the steady-state solution of the rigid isolation section under the same incoming flow conditions.

6. The design method of the flow control device for the inlet isolator based on the panel aerodynamic elastic effect according to claim 5, characterized in that: α＝2。 7. The design method of the flow control device for the air inlet isolation section based on the aeroelastic effect of the wall panel according to claim 1 is characterized in that: The elastic wall plate (10) is provided with bosses and through holes around the periphery, and the central area of the inner surface is a concave cavity. The thickness of the central area of the elastic wall plate (10) is smaller than the bosses around the periphery. Threaded holes are provided around the concave cavity structure. The elastic wall plate (10) is connected to the isolation section body (14) by screws (9) passing through the through holes of the elastic wall plate (10) and the threaded holes around the concave cavity structure.

8. The design method of the flow control device for the inlet isolator based on the wall panel aerodynamic elastic effect according to claim 7, characterized in that, A sealing strip (8) is provided between the periphery of the concave cavity structure and the boss of the elastic wall plate (10).

9. The design method of the flow control device for the air inlet isolation section based on the aeroelastic effect of the wall panel according to any one of claims 7-8, characterized in that: When the isolation section is not working, the upper surface of the elastic wall plate (10) is flush with the lower wall surface of the isolation section.

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