Intelligent flow control method and system for air-breathing high-speed aircraft

Abstract

The invention discloses an intelligent flow control method and system for an air-breathing high-speed aircraft, and relates to the field of flow control of aerodynamic performance of aircrafts, and the intelligent flow control method comprises the following steps: S1, arranging a suction module on a compression surface of an air inlet channel of the aircraft and / or a position, which is easy to cause flow separation, in the aircraft; s2, an air blowing module is arranged in the area, needing drag reduction, of the outer surface of the aircraft; and S3, the air source obtained through control of the driving module from the suction module is conveyed to the air blowing module through a regulating valve through the control system. According to the intelligent flow control method for the air-breathing type high-speed aircraft, air-source-free carrying of aircraft flow control is achieved, suction and blowing flow control can be achieved at the same time, namely, the aerodynamic performance of an air inlet channel is improved through suction, the aerodynamic performance of the outer surface of the aircraft is improved through blowing, and resistance is reduced.

Description

Technical Field

[0001] The present invention relates to the field of flow control for the aerodynamic performance of aircraft. More specifically, the present invention relates to an intelligent flow control method and system for air-breathing hypersonic aircraft. Background Art

[0002] Air-breathing hypersonic aircraft generally use a subsonic / combustion ramjet engine as the power system, which can perform hypersonic cruise and has strong maneuverability, and can meet the flight requirements of large range and wide speed range. As a key component of the air-breathing combined cycle engine, the inlet decelerates and pressurizes the oncoming flow through compression to provide oxidant for the combustion chamber. Designing a high-quality and high-flow hypersonic inlet is the primary task of engine design.

[0003] Air-breathing hypersonic aircraft have complex shock / boundary layer interference, which induces boundary layer separation and forms a large separation bubble. When the scale of the separation bubble exceeds a certain degree of the spatial scale of the hypersonic inlet, the flow capacity of the inlet decreases, the flow capture coefficient decreases significantly, the wave system and flow field structure of the inlet are damaged, the total pressure recovery of the inlet and the flow field uniformity decrease, resulting in inlet unstart. In the unstart mode, throat blockage will occur, resulting in surging, and the time-averaged pressure increases significantly. The instantaneous pressure load and aerodynamic drag can reach 20 times and 5 times the conventional start values respectively, causing deformation of the inlet structure and triggering flight accidents.

[0004] Flow control is to actively or passively interfere with the flow field by changing parameters such as the velocity, pressure, temperature, and density of the fluid, so as to optimize the fluid performance or reduce the fluid resistance. Flow control plays a very important role in improving the lift-drag ratio of aircraft, improving the starting performance of inlets, reducing noise and vibration.

[0005] Currently, the commonly used active flow control methods include: boundary layer suction, boundary layer blowing, energy deposition, magnetohydrodynamic control, etc. Among them, boundary layer suction has been proven by a large number of literature studies. By boundary layer suction, the low-speed gas in the boundary layer can be sucked away, so as to eliminate or reduce the separation zone. Similarly, a large number of literature studies have shown that boundary layer blowing can change the velocity profile shape of the fluid in the boundary layer, so as to reduce the frictional resistance, especially the drag reduction effect is most obvious in the turbulent boundary layer.

[0006] Currently, these flow controls are still difficult to be applied to air-breathing hypersonic aircraft. The main technical problems are: the air source treatment problem after boundary layer suction, and the problem that boundary layer blowing needs to carry an additional air source and the carried air source is limited. Summary of the Invention

[0007] An object of the present invention is to solve at least the above problems and / or defects and provide at least the advantages described hereinafter.

[0008] To achieve these objects and other advantages of the present invention, an intelligent flow control method for an air-breathing hypersonic vehicle is provided, including: S1. Arranging a suction module at the compression surface of the vehicle inlet and / or at positions inside the vehicle where flow separation is likely to occur; S2. Arranging a blowing module in the area of the vehicle outer surface where drag reduction is required; S3. Through the control system, the air source obtained by the drive module from the suction module is delivered to the blowing module through a regulating valve; Wherein, the control system detects the pressure change in the area where the suction module is located in real time through the sensor module, so as to adjust the suction volume by analyzing the state of the separation zone inside the vehicle; The control system detects the flow rate and pressure change in the area where the blowing module is located in real time through the sensor module, so as to control the blowing volume by analyzing the flow state of the vehicle outer surface.

[0009] A system, which is applied to the intelligent flow control method of an air-breathing hypersonic vehicle, includes: A flow control subsystem; A control module cooperating with the flow control subsystem; A sensor module for obtaining the state information of the flow control subsystem; A drive module communicatively connected to the control module to switch the working state of the flow control subsystem; Wherein, the flow control subsystem includes: a suction module, a blowing module.

[0010] Preferably, the suction module is configured to adopt a suction block; Wherein, a plurality of suction holes are arranged on the side of the suction block close to the inner flow side, and a gas collecting cavity communicating with the suction holes is arranged on the other side.

[0011] Preferably, the suction holes are cylindrical holes, and the hole diameter is 1 mm.

[0012] Preferably, the blowing module is configured to adopt a blowing block; Wherein, a plurality of blowing holes are arranged on the side of the blowing block close to the inner flow side, and a blowing cavity communicating with the blowing holes is arranged on the other side.

[0013] Preferably, the blowing holes are cylindrical holes or slot-shaped, and the hole diameter or slot width is 1 mm; Wherein, each blowing hole has a predetermined inclination angle designed along the flow direction, and the blowing holes are unevenly distributed on the surface of the blowing block.

[0014] Preferably, the sensor module includes: Inner wall surface areas upstream and downstream of the suction module for feeding back the pressure change at the corresponding position to the pressure sensor Ⅰ of the control system in real time; A flow sensor disposed on the blowing cavity and connected to the regulating valve in the driving module for feeding back the blowing flow rate information to the control system in real time; Outer wall surface areas upstream and downstream of the blowing module for feeding back the pressure change at the corresponding position to the pressure sensor Ⅱ of the control system in real time.

[0015] Preferably, the driving module includes: An air supply pipeline connecting the suction module and the blowing module; A driver disposed on the air supply pipeline for sucking gas from the suction module; A compressed air tank disposed on the air supply pipeline for temporarily storing the gas sucked by the driver; A regulating valve disposed on the air supply pipeline for controlling the output gas flow rate of the compressed air tank; A gas flow meter disposed on the air supply pipeline for measuring the gas flow rate after being regulated by the regulating valve; Wherein, the regulating valve, the driver and the gas flow meter are all communicatively connected to the controller.

[0016] The present invention has at least the following beneficial effects: (1) The method and the system provided by the present invention can simultaneously achieve the flow control of suction and blowing, improve the aerodynamic performance of the intake duct by suction, improve the aerodynamic performance of the outer surface of the aircraft by blowing, and reduce the resistance.

[0017] (2) The method and the system provided by the present invention get rid of the problem that a gas source needs to be carried during the implementation of traditional flow control and the carried gas source is limited. This method can ensure that the aircraft continuously sucks and discharges gas within a long time and a wide speed range, and has sustainability.

[0018] (3) The method and the system provided by the present invention can, by monitoring the flow parameters of the intake duct and the aircraft surface in real time, and according to the changes in the internal and external surface flows, perform real-time online control on the driver and the regulating valve, achieving an intelligent flow control effect and ensuring that the flow control maintains the best performance state.

[0019] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will be understood by those skilled in the art through the research and practice of the present invention. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the cooperation between the main components of the air-breathing hypersonic vehicle and the intelligent flow control system; Figure 2 It is the top view of the suction module in the present invention; Figure 3 It is the sectional view of the suction module in the present invention; Figure 4 It is the top view of the blowing module in the present invention; Figure 5 It is the sectional view of the blowing module in the present invention; Figure 6 It is the working flow chart of the intelligent flow control system in the present invention; Figure 7 It is the schematic diagram of the drag reduction area on one surface of the aircraft; Figure 8 It shows the schematic diagrams of uniform and non-uniform blowhole distributions under the same quantity; Figure 9 It is the schematic diagram of the wall model without blowholes; Figure 10 It is the schematic diagram of the wall blowing model with uniform blowhole distribution; Figure 11 It is the schematic diagram of the wall blowing model with non-uniform blowhole distribution obtained by the method of the present invention; Figure 12 For Figures 9 - 11 the three types of models, the schematic diagram of the distribution of the skin friction coefficient along the flow direction; Among them, the intake duct compression surface - 1, separation zone - 2, shock wave structure - 3, intake duct inner compression surface - 4, internal flow separation zone - 5, combustion chamber - 6, tail nozzle - 7, airframe - 8, blowing module - 9, sensor module - 10, control module - 11, drive module - 12, suction module - 13, suction hole - 14, boundary layer - 15, air collection chamber - 16, blowhole - 17, exhaust chamber - 18, driver - 19, compressed air tank - 20, regulating valve - 21, pressure sensor Ⅰ - 22, flow sensor - 23, pressure sensor Ⅱ - 24, vertical line - 25, baseline j -26, baseline j the starting position of j -27, baseline Specific implementation manner

[0021] The following further elaborates on the present invention in conjunction with the attached drawings, so that those skilled in the art can implement it with reference to the description in the specification.

[0022] As Figure 1 shown ( Figure 1where Ma is the Mach number), conventional air-breathing hypersonic vehicles mainly include: an inlet, a combustion chamber 6, a nozzle 7, and a fuselage 8. When a conventional air-breathing hypersonic vehicle operates under design conditions and reaches supersonic or even hypersonic speeds, a shock wave structure 3 (also known as the vehicle wave system structure) is usually generated at the head of the vehicle, the compression surface 1 of the inlet, and other parts. After the air flow passes through the shock wave structure 3, its speed decreases and the pressure rises. At the forebody compression surface, the air flow boundary layer gradually thickens along the flow direction. At the same time, due to the increase in the downstream flow pressure caused by the shock wave structure 3, a separation zone 2 is locally induced on the compression surface ( Figure 2 the red area shown by the label 2 in the figure), and the existence of the separation zone will affect the capture flow of the inlet, and means need to be taken to eliminate the separation zone or reduce its size. Similarly, in the internal compression surface 4 of the inlet (also known as the internal flow path of the inlet), there is an interaction between the shock wave train and the boundary layer of the internal flow path, which will also cause a corresponding internal flow path separation zone 5 ( Figure 2 the red area shown by the label 5 in the figure). The existence of these separation zones will affect the starting performance of the inlet, so measures need to be taken to eliminate or reduce the separation zones.

[0023] However, in the present invention, an intelligent flow control system is provided on the main components of a conventional air-breathing hypersonic vehicle, including a flow control subsystem; a control module 11 cooperating with the flow control subsystem; a sensor module 10 for obtaining the state information of the flow control subsystem; a drive module 12 communicatively connected to the control module to switch the working state of the flow control subsystem; wherein, the flow control subsystem includes: a suction module 13 and a blowing module 9.

[0024] In actual application, the suction module is arranged at positions on the compression surface and inside the vehicle inlet that are prone to flow separation, and is used to suck the low-speed gas in the separation zone to achieve the effect of eliminating or reducing the separation zone.

[0025] In actual application, the blowing module is arranged on the outer surface of the vehicle (such as the fuselage, wing, etc.), and by ejecting gas outward, it changes the velocity profile of the external flow boundary layer to achieve the effect of reducing the frictional drag.

[0026] Furthermore, as Figures 2 - 3 shown, a plurality of suction holes 14 are provided on the suction module 13 (which can be directly machined on the vehicle surface as needed), and the number of suction holes 14 can be reasonably designed according to the size of the separation zone and the density of the holes; wherein, the suction holes 14 are cylindrical holes, and the hole diameter is generally 1 mm.

[0027] The suction holes 14 are formed by opening holes on the wall surface of the separation zone. There is a gas collection cavity 16 below the suction holes 14 for collecting the gas sucked from the boundary layer 15.

[0028] Furthermore, as Figures 4 - 5 shown, the blowing module 9 (which can be directly processed on the surface of the aircraft as needed) is composed of a plurality of blowing holes 17. The number of the blowing holes 17 can be reasonably designed according to the size of the drag reduction area on the outer surface of the aircraft and the density of the holes; Among them, the blowing holes 17 are cylindrical holes or slot-shaped holes, and the hole diameter or slot width is generally 1 mm. The blowing holes 17 can be designed with a certain inclination angle along the flow direction. The blowing holes 17 are formed by opening holes on the outer surface of the aircraft. There is an exhaust cavity 18 below the blowing holes 17. By blowing air, the velocity profile of the boundary layer 30 on the outer surface of the aircraft is affected, so as to achieve the effect of drag reduction.

[0029] It should be noted that in actual applications, the blowing holes can be arranged along the flow direction according to the distribution of the skin friction drag on the aircraft surface, taking the equal-spacing difference of the skin friction drag to arrange the blowing holes, that is, set as a non-uniform layout to achieve the best drag reduction effect. Specifically, the specific implementation of the non-uniform layout of the blowing holes is as follows: S1. First, for the aircraft that needs drag reduction, obtain the skin friction drag coefficient of the aircraft surface through methods such as experimental measurement, numerical simulation calculation or empirical estimation. Its definition is as follows: (1) In the above formula, C f is the skin friction drag coefficient (abbreviated as the friction drag coefficient), is the wall shear stress, and are the density and velocity of the reference oncoming flow respectively. Among them, the wall shear stress can be obtained through methods such as experimental measurement, numerical simulation calculation or empirical estimation.

[0030] S2. According to the obtained friction drag coefficient, analyze the drag reduction requirements of the entire aircraft surface, determine the area with the largest friction drag distribution value on the entire aircraft or the area 29 of the aircraft surface that needs drag reduction according to the aerodynamic analysis. As Figure 7 shown in the schematic diagram of the drag reduction area of a certain surface of the aircraft. On the surface of the aircraft where multiple blowing holes need to be arranged, divide the layout baseline of the wall blowing holes along the flow direction, and select any one baseline j ( Figure 7 in the baseline j is marked as 26, and the vertical line is marked as 25, which is used to represent the auxiliary line perpendicular to the baseline j on this surface), and its corresponding physical coordinate in the transverse direction is y j , and now it is given on the baselinej The porous distribution design method on it, and the remaining baselines refer to this method.

[0031] S3. Extract the baseline j The friction coefficient on it , and its distribution along the flow direction is as Figure 2 shown. Take the starting point and the ending point of the friction coefficients as and respectively. Take the number of wall blowing holes as N (take N = 5 as an example in the figure), then calculate the friction coefficient difference : (2) S4. Determine the position of each wall blowing hole according to the friction coefficient difference. The specific method is that according to Equation (2), the friction coefficient at the i -th position can be obtained as: (3) S5. According to the friction coefficient i at the -th position, combined with the friction coefficient distribution obtained in S4, inversely calculate the physical coordinate j along the flow direction corresponding to the friction coefficient on the baseline x i , x i represents the abscissa. It should be noted here that although the friction coefficient of the entire aircraft along the flow direction is not monotonically increasing or decreasing, due to factors such as boundary layer transition, the wall friction coefficient after the flow on the aircraft surface transitions to turbulence is much higher than that of laminar flow. Therefore, wall blowing is most effective for reducing drag in the turbulent boundary layer. After transitioning to turbulence, except for the action of shock wave interference or other special factors, the friction of the turbulent boundary value is necessarily monotonically changing along the flow direction. In addition, since the wall blowing holes will cause certain damage to the surface structure, generally only local areas are used for drag reduction. The area of this local area is small, so it can be considered that the friction coefficient is monotonically changing along the flow direction. Based on the above analysis, since is monotonic along the x coordinate in the flow direction, then value corresponds one-to-one with the x coordinate, and determining a certain quantity can determine the x value.

[0032] S6. On the baseline j, according to the number N of wall blowing holes, it can be known from the above steps that the position of each wall blowing hole is ([[]]END]] x i , y j), namely Figure 8 In Figure 8 , the marker 27 is the baseline j starting position, and the marker 28 is the baseline j ending position, Figure 8 in represents the differential value of the friction coefficient, represents the differential value of the distance along the flow direction.

[0033] In addition, in order to show the differences from the traditional design method, under the condition of ensuring the same number of wall blowing holes, Figure 8 the distribution positions of the wall blowing holes with uniform distribution as shown by A1, A2, and A3 on the baseline j and the distribution positions of the wall blowing holes with non-uniform distribution obtained by the method of the present invention as shown by B1, B2, and B3 are also given. It can be seen that the arrangement rules of the wall blowing holes obtained by the two methods are completely different, so the corresponding drag reduction effects must be different. In the following text, it is proved by examples that the design method of the present invention has a better drag reduction effect.

[0034] S7. For the positions of other baseline wall blowing holes, refer to steps S3 to S6. Through the above method, the wall blowing porous design method for the entire drag reduction area can be determined.

[0035] Example: For a two-dimensional inclined wedge with a leading edge angle θ = 22.5°, and the curvature of the upper surface of the inclined wedge gradually decreases, and the curvature at the end is zero. Under this working condition, wall models without blowing holes as shown in Figure 9 , wall blowing models with uniformly distributed blowing holes as shown in Figure 10 , and wall blowing models with non-uniformly distributed blowing holes obtained by the design method of the present invention as shown in Figure 11 are respectively constructed. To prove the design effect of the present invention, the computational fluid dynamics method is used to simulate the flow field, and the incoming flow Mach number is 5, and the wall blowing speed is set to 1% of the incoming flow speed.

[0036] Based on Figure 12 the distribution diagrams of the skin friction coefficients along the flow direction on the surfaces of the three types of models given ( Figure 12 in C f is the skin friction coefficient, and x / L represents the dimensionless distance along the flow direction), it can be seen that compared with no wall blowing, both of the two porous arrangement methods with wall blowing can effectively reduce the wall friction. At the same time, compared with the porous arrangement method with uniform distribution, except for the relatively high friction in some local areas, the friction in most of the overall areas of the arrangement method of the present invention is lower than that of the traditional method, indicating that the comprehensive drag reduction effect of the porous arrangement of the present invention has been significantly improved.

[0037] Furthermore, as in Figure 1 ,Figure 6 as shown in (wherein, Figure 6 the solid line with an arrow represents the air flow direction, the dashed line with an arrow represents the detection data feedback direction of the sensor, and the dotted line with an arrow represents the direction for the controller to send control signals). The sensor module 10 (including the inner surface pressure sensor and the outer surface pressure sensor) is arranged in the upstream and downstream regions of the suction module and the blowing module, responsible for monitoring the dynamic changes of the pressure at the corresponding positions and feeding back the pressure information to the control system in real time. Specifically, the pressure sensor Ⅰ 22 is set in the inner wall surface regions upstream and downstream of the suction module, for feeding back the pressure changes at the corresponding positions to the control system in real time; is set on the blowing chamber and connected to the regulating valve in the drive module to feed back the blowing flow rate information to the control system in real time; the pressure sensor Ⅱ 24 is set in the outer wall surface regions upstream and downstream of the blowing module, for feeding back the pressure changes at the corresponding positions to the control system in real time.

[0038] Furthermore, as Figure 6 shown, the drive module includes a driver 19, a compressed air tank 20 and a regulating valve 21. The driver is responsible for sucking gas from the suction module to the compression tank, and the regulating valve is responsible for controlling the discharge of the compressed gas to the blowing module. At the same time, as needed, a gas flow meter for measuring the gas flow rate flowing through the pipeline after the regulation of the regulating valve can also be set.

[0039] Furthermore, as Figure 6 shown, the control module 11 is the control unit of the entire intelligent flow control. By analyzing the pressure changes in the suction module, it controls the power of the driver for sucking, analyzes the pressure changes in the blowing area to control the size of the regulating valve switch, and conducts feedback by monitoring the flow sensor.

[0040] Furthermore, as Figure 6 shown, the control module 11 (also called the controller) is responsible for the operation control of the entire flow control. The controller is pre-set with an intelligent control algorithm. By receiving the sensor information in the suction module area, it analyzes the state of the separation area, and then controls the power of the driver, thereby adjusting the suction effect. At the same time, the controller also receives the sensor information in the blowing module area, and controls the size of the regulating valve by analyzing the outer surface flow state, thereby adjusting the blowing effect.

[0041] The present invention intends to combine the two flow control technologies of suction and blowing. By introducing an intelligent control system, it can control the size of the separation area of the inlet of the air-breathing aircraft, improve the starting performance of the inlet, and at the same time achieve the effect of drag reduction on the outer surface of the aircraft. The air source obtained by the suction control is used for the blowing control, solving the air source problem of the flow control. The control system realizes closed-loop control and has sustainability.

[0042] The above solution is only an illustration of a preferred example, but is not limited thereto. When implementing the present invention, appropriate substitutions and / or modifications can be made according to the needs of users.

[0043] Although the embodiments of the present invention have been disclosed above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated and described examples here.

Claims

1. An intelligent flow control method for an air-breathing hypersonic vehicle, characterized in that Comprising: S1. Arranging a suction module at the compression surface of the aircraft inlet and / or at positions inside the aircraft where flow separation is likely to occur; S2. Arranging a blowing module in the area on the outer surface of the aircraft that requires drag reduction; S3. Through the control system, the air source obtained by the drive module from the suction module is delivered to the blowing module through a regulating valve; Wherein, the control system uses a sensor module to detect the pressure change in the area where the suction module is located in real time, so as to adjust the suction volume by analyzing the state of the separation zone inside the aircraft; The control system uses a sensor module to detect the flow rate and pressure change in the area where the blowing module is located in real time, so as to control the blowing volume by analyzing the flow state on the outer surface of the aircraft.

2. A system, which is applied to the intelligent flow control method for an air-breathing hypersonic vehicle as described in claim 1, wherein, Comprising: A flow control subsystem; A control module cooperating with the flow control subsystem; A sensor module for obtaining the state information of the flow control subsystem; A drive module communicatively connected to the control module to switch the working state of the flow control subsystem; Wherein, the flow control subsystem includes: a suction module, a blowing module.

3. The system according to claim 2, characterized in that, The suction module is configured to adopt a suction block; Wherein, the suction block is provided with a plurality of suction holes near the inner flow side, and a gas collecting cavity communicating with the suction holes is provided on the other side.

4. The system according to claim 3, wherein The suction holes are cylindrical holes with a hole diameter of 1 mm.

5. The system according to claim 2, wherein The blowing module is configured to adopt a blowing block; Wherein, the blowing block is provided with a plurality of blowing holes near the inner flow side, and a blowing cavity communicating with the blowing holes is provided on the other side.

6. The system according to claim 5, wherein The blowing holes are cylindrical holes or slot-shaped, with a hole diameter or slot width of 1 mm; Wherein, each blowing hole has a predetermined inclination angle designed along the flow direction, and each blowing hole is non-uniformly arranged on the surface of the blowing block.

7. The system according to claim 2, wherein The sensor module includes: A pressure sensor I arranged in the inner wall surface area upstream and downstream of the suction module, for feeding back the pressure change at the corresponding position to the control system in real time; A flow sensor arranged on the blowing cavity and connected to the regulating valve in the drive module, for feeding back the blowing flow rate information to the control system in real time; A pressure sensor II arranged in the outer wall surface area upstream and downstream of the blowing module, for feeding back the pressure change at the corresponding position to the control system in real time.

8. The system according to claim 2, wherein The drive module includes: An air delivery pipeline connecting the suction module and the blowing module; A driver arranged on the air delivery pipeline for sucking gas from the suction module; A compressed air tank arranged on the air delivery pipeline for temporarily storing the gas sucked by the driver; A regulating valve arranged on the air delivery pipeline for controlling the gas flow rate output by the compressed air tank; A gas flow meter arranged on the air delivery pipeline for measuring the gas flow rate after being adjusted by the regulating valve; Wherein, the regulating valve, the driver, and the gas flow meter are all communicatively connected to the controller.

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