An aircraft flexible porous media skin and anti-icing method based thereon

Abstract

The present application belongs to the technical field of aircraft skin, and relates to an aircraft elastic porous medium skin, a plurality of hole bodies are prefabricated on the skin, an organ pipe type nozzle is installed in the hole body, the organ pipe type nozzle is connected with a jet control system for providing a heat medium for the organ pipe type nozzle; the organ pipe type nozzle comprises an inlet section, a resonance section, an intermediate section and an outlet section connected in sequence; the inlet section is provided with an incidence hole, the resonance section is provided with a resonance hole, the intermediate section is provided with an intermediate hole, and the outlet section is provided with an emission hole which is a diverging hole; the incidence hole, the resonance hole and the intermediate hole are all cylindrical holes, and the diameters of the incidence hole, the resonance hole and the intermediate hole gradually decrease. The elastic porous medium skin is used to induce the slip and micro-cavitation effect of unsteady boundary layer fluid, and the geometric parameters of the control hole are controlled, so that the self-adaptive boundary layer flow state is greatly reduced, the frictional resistance is reduced, and the outer lining has the characteristics of noise reduction, and has the scattering and absorption effect on sound waves.

Description

Technical Field

[0001] This invention belongs to the field of aircraft skin technology, specifically relating to an elastic porous medium skin for aircraft and an anti-icing method based thereon. Background Technology

[0002] The low Reynolds number effect is a key common bottleneck encountered by existing aircraft in expanding into near-space, high-altitude regions, and maritime airspace, and is considered an "international challenge." It has been proven that traditional lift-enhancing and drag-reducing technologies, as well as flow control techniques, are insufficient to meet and overcome the aforementioned aerodynamic development needs and obstacles. Therefore, it is essential to explore new lift-enhancing, drag-reducing, and flow control technologies. The fundamental solution to this problem lies in aerodynamics, primarily depending on a deeper understanding of the characteristics and control of low Reynolds number flows.

[0003] To some extent, boundary layer control is particularly important in viscous flows. Based on in-depth research in recent years, it is possible to utilize and control the positive effects of unsteady aerodynamics, such as nonlinear high lift, wall slip drag reduction, targeted energy transfer, and nonlinear energy sinks, to meet and overcome the aforementioned aerodynamic development needs and obstacles. Experiments have also verified that this technology is a feasible and efficient method.

[0004] Current de-icing technologies and skin anti-icing methods mostly focus on using engine waste heat to heat the entire skin surface. The disadvantage is that the heating area is too large, and it is difficult to maintain the desired anti-icing temperature under forced convection conditions. Summary of the Invention

[0005] The purpose of this invention is to provide an elastic porous medium skin for aircraft and an anti-icing method based thereon, which solves the problem in the prior art that it is difficult to maintain the desired anti-icing temperature when heating the entire skin surface using engine waste heat.

[0006] This invention is achieved through the following technical solution:

[0007] An elastic porous medium skin for an aircraft has several pre-fabricated holes on it, and an organ-shaped nozzle is installed in the holes. The organ-shaped nozzle is connected to a jet control system. The jet control system is used to provide a heat medium to the organ-shaped nozzle.

[0008] The bellows-shaped nozzle includes an inlet section, a resonant section, a middle section, and an outlet section connected in sequence; the inlet section has an injection hole, the resonant section has a resonant hole, the middle section has a middle hole, and the outlet section has an injection hole.

[0009] The entrance hole, resonant hole, and intermediate hole are all cylindrical holes, while the exit hole is a gradually expanding hole; the diameters of the entrance hole, resonant hole, and intermediate hole decrease sequentially; the entrance hole, resonant hole, intermediate hole, and exit hole are connected to form a jet cavity;

[0010] The injection port is located on the inner wall side of the skin, and the injection port is located on the outer wall side of the skin.

[0011] Furthermore, the bellows-shaped nozzle is made of piezoelectric composite material, which consists of a piezoelectric material cylindrical layer and a resin material matrix layer.

[0012] Furthermore, each interface of the piezoelectric composite material is connected to a DC-powered negative capacitor control circuit. The DC-powered negative capacitor control circuit includes two fixed resistors R0 and R1, a variable resistor R2, a capacitor C0, and an operational amplifier. The negative terminal of the operational amplifier leads out three circuits that are respectively connected to the cylindrical layer of the piezoelectric material, and the positive terminal leads out three circuits that are connected to the other three interfaces and grounded.

[0013] Furthermore, the jet control system includes a water tank, an electric motor, a high-pressure water pump, and a power supply box. The power supply box, the electric motor, and the high-pressure water pump are connected in sequence. The high-pressure water pump is connected to the water tank through a pipeline, on which a throttle valve is installed. The high-pressure water pump is connected to the injection hole of the bellows-shaped nozzle.

[0014] Furthermore, the electric motor is connected to the high-pressure water pump via a coupling, and the heat transfer medium in the water tank is heated by the waste heat of the engine.

[0015] Furthermore, the diffusion angle of the gradually expanding aperture is 20-60°.

[0016] Furthermore, the diameter of the incident aperture is D0; the diameter of the resonant aperture is D and its length is L; the diameter of the intermediate aperture is d and its length is S; and the length of the exit section is S1.

[0017]

[0018] S = (2-6)d;

[0019] S1=(3-7)d.

[0020] Furthermore, the expression for calculating the diameter d of the intermediate hole is:

[0021]

[0022] Where q is the injection flow rate of the injection hole, P is the upstream pressure, n is the number of bellows-type nozzles, and b is the flow correction coefficient.

[0023] Furthermore, the expression for calculating the length L of the resonant aperture is:

[0024]

[0025] Where d is the diameter of the central hole, K N For the modulus coefficient, Sr *is the critical Strouhal number, and Ma is the Mach number.

[0026] The present invention also discloses an anti-icing method based on the elastic porous medium skin of the aircraft, comprising the following steps:

[0027] After the jet control system is activated, it provides a heat transfer medium to the organ-type nozzle;

[0028] The heat medium flows sequentially through the injection hole, resonance hole, intermediate hole and exit hole from the inside to the outside of the elastic porous medium skin, melting the ice on the outside of the skin;

[0029] Meanwhile, micro-cavitation jets are generated in the near-outlet flow field of the nozzles of the aircraft's elastic porous medium skin, and the superposition of the flow fields near the outlet of multiple accordion-shaped nozzles generates a virtual aerodynamic shape to replace the deformable wing.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The purpose of this invention is to provide an elastic porous medium skin for aircraft. Multiple accordion-shaped nozzles are installed in the existing skin structure to form an elastic porous medium skin. Each accordion-shaped nozzle includes an inlet section, a resonant section, a middle section, and an outlet section connected in sequence. An inlet port is formed in the inlet section, a resonant port in the resonant section, a middle port in the middle section, and an outlet port in the outlet section. The outlet port is a gradually expanding port. The heat transfer medium flows sequentially through the inlet port, resonant port, middle port, and outlet port from the inside to the outside of the elastic porous medium skin, melting ice on the outer side of the skin. Simultaneously, a micro-cavitation jet is generated in the flow field near the nozzle outlet of the aircraft's elastic porous medium skin. The superposition of the flow fields near the outlet of multiple accordion-shaped nozzles generates a virtual aerodynamic shape to replace a deformable wing. Due to the presence of the cavitation jet near the nozzle outlet, the flow direction of the incoming boundary layer fluid on the wing surface changes from the x-direction to the y-direction and continues to change back to the x-direction on the virtual shape surface, resulting in a slip effect. By utilizing elastic porous media skin to induce slip and microcavitation effects in unsteady boundary layer fluids and controlling the geometric parameters of the pores, the aim is to significantly reduce frictional resistance by adapting to the boundary layer flow state. Furthermore, this type of liner has noise reduction characteristics and can scatter and absorb sound waves.

[0032] This invention discloses an elastic porous medium skin for aircraft. Using a jet generator, it can achieve high-altitude anti-icing and de-icing, and utilize the generated aerodynamic virtual shape to improve the skin's deformation degree. The aerodynamic virtual shape can expand the angle of attack range, improve airflow separation, reduce drag, and increase the lift-to-drag ratio. The actual controllable deformation rate of the piezoelectric composite material reaches over 85.7%, which can essentially achieve precise control of the geometric parameters of each section of the nozzle, thereby changing the effective throttling area to adapt to different external operating conditions. During service, when sound waves in the external flow field propagate to the nozzle outlet, the change in the diffuser cavity diameter at this time will generate standing waves through multiple reflections. If these standing waves resonate with the resonant hole at the middle of the nozzle, they will excite stronger cavitation. The sound waves dissipate some energy in this process, reducing the sound intensity and achieving noise reduction. Simultaneously, the micro-jet generated by the nozzle can reduce near-wall boundary layer pressure pulsation, also reducing noise.

[0033] The aeroelastic effect of a properly controlled flexible structure can give the wing excellent aerodynamic performance. The boundary layer slip phenomenon induced by the aeroelastic interaction with the incoming flow can delay flow separation at small angles of attack and reattach the separated flow at large angles of attack, resulting in significant lift and drag reduction effects, as well as the positive effects listed above. This is also the main content of this invention, which is to induce cavitation jet by actively controlling the flexible structure (nozzle parameters, jet conditions). The heat and momentum generated can achieve the effects of anti-icing and de-icing. Attached Figure Description

[0034] Figure 1 This is a schematic diagram showing the change in velocity distribution between a conventional skin and the elastic porous medium skin of the present invention.

[0035] Figure 2 This is a schematic diagram of the structure of the bellows-shaped nozzle of the present invention, wherein:

[0036] D0 - Entrance aperture diameter, mm; D - Resonant aperture diameter, mm; L - Resonant aperture length, mm;

[0037] d - Diameter of the intermediate hole, mm; S - Length of the intermediate hole, mm; S1 - Length of the exit hole, mm;

[0038] α - Diffusion angle

[0039] Figure 3 This is a radial schematic diagram of the organ-type nozzle with a diffuser cavity of the present invention (purple represents the cavity wall thickness).

[0040] Figure 4 This is a schematic diagram of the DC power supply negative capacitor control circuit for the piezoelectric composite material of the present invention;

[0041] Figure 5 This is a schematic diagram of the jet control system of the present invention;

[0042] Figure 6 This is a schematic diagram of the wind tunnel test site for the present invention.

[0043] The components include: 1. Power supply box; 2. Motor; 3. Coupling; 4. High-pressure water pump; 5. Water tank; 6. Throttling valve; 7. Bellows nozzle.

[0044] 71. Entrance aperture; 72. Resonance aperture; 73. Intermediate aperture; 74. Exit aperture. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0046] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0047] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus.

[0048] This invention discloses an elastic porous medium skin for an aircraft, wherein a plurality of holes are prefabricated on the skin, and an organ-tube type nozzle 7 is installed in the holes, such as... Figure 5 As shown, the bellows-shaped nozzle 7 is connected to a jet control system; the jet control system is used to provide the bellows-shaped nozzle 7 with the jetting heat medium; as shown... Figure 2As shown, the bellows-shaped nozzle 7 includes an inlet section, a resonant section, an intermediate section, and an outlet section connected in sequence; the inlet section has an injection hole 71, the resonant section has a resonant hole 72, the intermediate section has an intermediate hole 73, and the outlet section has an exit hole 74; the injection hole 71, the resonant hole 72, and the intermediate hole 73 are all cylindrical holes, and the exit hole 74 is a gradually expanding hole; the diameters of the injection hole 71, the resonant hole 72, and the intermediate hole 73 decrease sequentially; the injection hole 71, the resonant hole 72, the intermediate hole 73, and the exit hole 74 are connected to form a jet cavity; the injection hole 71 is located on the inner wall side of the skin, and the exit hole 74 is located on the outer wall side of the skin.

[0049] For the specific layout and interrelationships of the jet control system, see [link to relevant documentation]. Figure 5 The jet control system includes a water tank 5, an electric motor 2, a high-pressure water pump 4, and a power supply box 1. The power supply box 1, the electric motor, and the high-pressure water pump 4 are connected in sequence. The high-pressure water pump 4 is connected to the water tank 5 through a pipeline, on which a throttle valve 6 is installed. The high-pressure water pump 4 is connected to the inlet 71 of the bellows-shaped nozzle 7. Through the jet control system, the heat transfer medium can be introduced into each bellows-shaped nozzle 7 via the high-pressure water pump 4, jetting from the inside of the skin to the outside of the skin, thereby melting the ice on the skin.

[0050] Microcavitated jets are generated in the near-outlet flow field of the nozzles of the aircraft's elastic porous medium skin. The superposition of flow fields at the inlet and outlet of multiple nozzles can generate virtual aerodynamic shapes to replace deformable wings.

[0051] In order to ensure the necessary rigidity and strength during the design process of the skin, the base part still uses common aluminum-magnesium alloy as the manufacturing material, and only the nozzle structure wall inside the skin uses piezoelectric composite material.

[0052] In the design process of the skin, the selection of the nozzle type is as follows: Figure 2 The image shows a bellows nozzle with a gradually expanding outlet section.

[0053] To ensure the stability and continuity of the cavitation jet generated by this structure, the geometric parameters involved are guided by well-established cavitation generation theories. For example... Figure 2 As shown, the geometric dimensions of each part of the nozzle are determined according to corresponding empirical formulas. For example, the length of the cylindrical orifice is determined by the flow rate provided by the water pump, the number of nozzles, and a correction factor.

[0054] The diameter of the central orifice (73) is the first parameter, and it is mainly determined by the flow-pressure formula:

[0055]

[0056] Where q is the incident flow rate of the inlet orifice 71, i.e., the inlet cross-sectional flow rate of the bellows-shaped nozzle 7 structure; P is the upstream pressure; n is the number of nozzles (the number of nozzles required per unit skin area is determined based on the porosity); and b is the flow rate correction coefficient, which is determined by... Figure 5 After determining the jet flow rate q and pressure P of the water pump delivered to the injection port 71, d can be determined.

[0057] The next step is to determine the size of the resonant orifice 72 of the nozzle. The square of the ratio between the diameter D of the resonant orifice 72 and the diameter of the intermediate orifice 73d is generally in the range of 10-11. At the same time, the square of the ratio between the diameter D0 of the injection orifice 71 and the diameter of the resonant orifice 72D is generally taken as 3.5-4.5.

[0058] The Mach number should be 0.08-0.1, and the Strouhal number should be 0.3. The dimensionless parameters mentioned here refer to the flow state inside the nozzle. For example, the jet velocity at each cross section is 0.08-0.1 of the local speed of sound at each cross section inside the nozzle.

[0059] The second important parameter of the resonant aperture 72 is its length L, which needs to be determined by the modulus, the critical Strouhal number, and the Mach number. Firstly, the vibration within the resonant aperture 72 is strongest when the self-excited oscillation frequency equals the natural frequency of the resonant aperture 72. At this point: This explains why the natural frequency f is affected by the modulus coefficient K. N The influence of three parameters: disturbance velocity a, and length of resonant aperture 72.

[0060] Modulus coefficient K N Depending on the diameter ratio mentioned above, the oscillation modulus can be taken as 1 / 2 or 1 / 2 minus 1 / 4. The self-excited oscillation frequency can be determined by the critical Strouhal number, the diameter of the central aperture 73, and the speed of sound. Now, substituting f into the equation again... * Given the condition f, we can obtain: The asterisk (*) represents a critical parameter. The length L of the resonant aperture 72 can be determined using this formula.

[0061] After determining the diameter d of the intermediate hole 73 and the size of the resonant hole 72, the length S of the intermediate hole 73 is determined. This parameter is usually determined by a ratio. Currently, the length S of the intermediate hole 73 should be 2-6 times the diameter d of the intermediate hole 73, so S = (2-6)d.

[0062] Similarly, the length S1 of the exit hole 74 is also determined by the ratio range of the diameter d of the intermediate hole 73. Generally, the length S1 of the exit hole 74 is taken as 3-7 times the diameter d of the intermediate hole 73, that is, S1=(3-7)d.

[0063] like Figure 2As shown, since the nozzle contains a gradually expanding section, the diffusion angle α is an extremely important parameter, which is generally taken as 20-60 degrees, with 30 degrees being the most common.

[0064] The bellows-shaped nozzle 7 is made of piezoelectric composite material, which consists of piezoelectric sheets and resin. The geometric arrangement of the piezoelectric sheets is explained below: From... Figure 2 Starting from the left, the nozzle's jet cavity is divided into an inlet orifice (corresponding to diameter D0), a resonant orifice 72 (corresponding to length L and diameter D), an intermediate orifice 73 (corresponding to length S and diameter d), and an outlet orifice 74 (corresponding to length S1 and diffusion angle α). From the left view, one can see the circular channel cross-sections (concentric circles with diameters D0, D, and d) and variable diameter cross-sections (the inlet and outlet cross-sections of the resonant orifice 72) of the inlet orifice, resonant orifice 72, and intermediate orifice 73. Since actual piezoelectric structures cannot have zero wall thickness, the circular channel cross-sections have a thickness (corresponding to...). Figure 3 The dark gray rings in the diagram represent three piezoelectric cylindrical layers of the same thickness but different diameters in three dimensions. Similarly, the light gray rings between the dark gray rings represent the resin matrix layer. The three piezoelectric layers are 0.6 mm thick cylindrical layers connected by resin material. The thickness of the resin matrix cylindrical layers is determined by calculating the diameter parameters of each cavity as described above.

[0065] like Figure 3 As shown, Figure 2 The left view of the nozzle is shown, where the dark gray areas represent the wall thickness of each cylindrical segment, and the light gray annular structure represents the diameter-changing plane between the cylindrical segments, perpendicular to the direction of the left view. The overall square boundary represents the relative size of the nozzle, conforming to the porosity, and the area of ​​the skin it can act upon.

[0066] The circuits connected to each interface of the piezoelectric composite material in the nozzle section of the skin are DC-powered negative capacitor control circuits, such as... Figure 4 As shown, the DC power supply negative capacitor control circuit includes two fixed resistors R0 and R1, one variable resistor R2, one capacitor C0, and an arithmetic unit, model LM324N.

[0067] Figure 3 The three-layer piezoelectric structure shown has dark gray sections corresponding to the wall thickness of each cylindrical segment; the light gray rings represent the variable diameter interfaces of the cylindrical segments, perpendicular to the direction of the left view. Meanwhile, Figure 4 The negative terminal of the operational amplifier has three circuits connected to the piezoelectric structure, and the positive terminal also has three circuits connected to three other interfaces and grounded.

[0068] and Figure 4 The specific connection method of the circuit is as follows: Figure 3The piezoelectric material cylindrical layer and the matrix cylindrical layer shown are numbered 1-6 in descending order of radius, with 1 being the outermost (largest radius) purple ring outer boundary. Boundaries 1, 4, and 5 are grounded (0), and boundaries 2, 3, and 6 are connected to the negative terminal of the operational amplifier in the negative capacitor circuit.

[0069] Figure 5 This is a basic pipeline diagram. The flow rate of each branch pipe in the diagram corresponds to 1 / n of the total flow rate. n and the diameter d of the central hole 73 are taken as the same value in the empirical formula. Both are parameters that need to be determined based on the pump power. This process should consider the balance between maximizing energy saving of pump allocation and the optimal flow rate required for cavitation effect.

[0070] Installing the accordion-shaped nozzle 7 into a traditional aluminum-magnesium alloy skin can alter the boundary characteristics of the traditional aluminum-magnesium alloy skin. Figure 1 It is evident that without the porous media layer, i.e., without the bellows-shaped nozzle 7 installed, the velocity change only exhibits a smooth velocity distribution from 0 to U0; however, the introduction of the porous media layer causes the velocity distribution to exhibit a 0-U0 range. D -U i The process of -U0, where 0-U D -U i This is the slip process, and the corresponding x-boundary is the slip boundary.

[0071] Application Examples

[0072] The physical manufacturing and design of this skin were completed through a phase one of testing and verification with the support of a research project funded by the General Armaments Department. The skin used in the tests was calculated according to the aforementioned criteria, and the main parameters for each part are as follows: The test utilized a wind tunnel testing platform to simulate the low Reynolds number conditions (Re = 1E4-1E5) corresponding to the skin design, conducting tests within the Mach number range of 0.05-0.3. The main test verification indicators compared to traditional skin wings included: the rate of change of drag and lift coefficients, and the stall angle retardation rate.

[0073] like Figure 5 As shown, the piping system includes a motor 2, a coupling 3, a high-pressure water pump 4, a water tank 5, a throttle valve 6, and a nozzle structure. The high-pressure water pump 4 is powered by the motor 2 and coupling 3, and the water tank 5 supplies liquid, typically water. The high-pressure water pump 4 generates high pressure and a corresponding flow rate of liquid, which is then delivered to the throttle valve 6. The throttle valve 6 reduces some of the pressure and eliminates upstream pressure pulsations, thus reducing noise. The liquid is then sent to the jet nozzle to form a cavitation jet.

[0074] In the experiment Figure 6When the flexible skin pipeline shown is not flowing with liquid (passive control), the change rate of lift-to-drag ratio and the change of resistance are tested when the fluid flows through the porous skin: the maximum reduction rate of resistance is 89%, the maximum increase of lift coefficient is 47%, and the maximum increase of lift-to-drag ratio is 815%.

[0075] After adding liquid to the piping system (actively controlled), a virtual shape was created. The maximum resistance reduction rate was similar to that without liquid, both at 47%, but the maximum lift coefficient increased by 138%. The lift coefficient was significantly improved, and the large amount of heat generated by cavitation bubble collapse effectively addressed the icing problem at high altitudes. Furthermore, no nozzle clogging was observed during the experiment, verifying its stability and expected beneficial characteristics in a real-world operating environment.

[0076] First, this type of outer liner differs from some traditional skins. It has an adaptive porous structure and the overall material is flexible. The flexible structure here refers to the fact that the wall thickness of each cylindrical section of the nozzle can be changed, rather than the structure being a soft plastic material with low surface stiffness.

[0077] Secondly, the porous structure of this type of liner is not designed to adapt to a specific flow condition. The configuration of the pores can be controlled by using appropriate piezoelectric structures or super magnetostrictive materials, thereby adapting to a variety of flow conditions.

[0078] Furthermore, such liner materials create a virtual aerodynamic shape effect on the wing surface to replace deformable wings.

[0079] In the above-mentioned experimental examples, relevant theoretical results were also obtained, verifying that the active control skin of the adaptive variable structure can realize the directional transport of energy and guide the energy to the icing position. Furthermore, the aerodynamic virtual shape generated by this type of active control skin can better control the lift coefficient and other dynamic indicators without depending on the deformation of the actual wing. Within the operating conditions involved in the experiment, good lift-increasing and drag-reducing effects were achieved.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An elastic porous dielectric skin for an aircraft, characterized in that, Several holes are prefabricated on the skin, and an organ-type nozzle (7) is installed in the holes. The organ-type nozzle (7) is connected to a jet control system. The jet control system is used to provide heat medium to the organ-type nozzle (7). The bellows-shaped nozzle (7) includes an inlet section, a resonant section, an intermediate section and an outlet section connected in sequence; the inlet section has an injection hole (71), the resonant section has a resonant hole (72), the intermediate section has an intermediate hole (73), and the outlet section has an injection hole (74). The inlet hole (71), the resonant hole (72), and the intermediate hole (73) are all cylindrical holes, and the outlet hole (74) is a gradually expanding hole; the diameters of the inlet hole (71), the resonant hole (72), and the intermediate hole (73) decrease sequentially; the inlet hole (71), the resonant hole (72), the intermediate hole (73), and the outlet hole (74) are coaxially connected to form a jet cavity; The inlet (71) is located on the inner wall side of the skin, and the outlet (74) is located on the outer wall side of the skin.

2. The elastic porous dielectric skin for an aircraft according to claim 1, characterized in that, The bellows-shaped nozzle (7) is made of piezoelectric composite material, which consists of a piezoelectric cylindrical layer and a resin matrix layer.

3. The elastic porous dielectric skin for an aircraft according to claim 2, characterized in that, Each interface of the piezoelectric composite material is connected to a DC-powered negative capacitor control circuit, which contains two fixed resistors. , A variable resistor A capacitor And an operational amplifier, with three circuits leading from the negative terminal of the operational amplifier to be connected to the piezoelectric cylindrical layer, and three circuits leading from the positive terminal to be connected to three other interfaces and grounded.

4. The elastic porous dielectric skin for an aircraft according to claim 1, characterized in that, The jet control system includes a water tank (5), an electric motor (2), a high-pressure water pump (4) and a power supply box (1). The power supply box (1), the electric motor and the high-pressure water pump (4) are connected in sequence. The high-pressure water pump (4) is connected to the water tank (5) through a pipeline. A throttle valve (6) is provided on the pipeline. The high-pressure water pump (4) is connected to the inlet (71) of the bellows-shaped nozzle (7).

5. The elastic porous dielectric skin for an aircraft according to claim 4, characterized in that, The electric motor (2) is connected to the high-pressure water pump (4) via a coupling (3), and the heat medium in the water tank (5) is heated by the waste heat of the engine.

6. The elastic porous dielectric skin for an aircraft according to claim 1, characterized in that, The diffusion angle of the gradually expanding orifice is 20-60°.

7. The elastic porous dielectric skin for an aircraft according to claim 1, characterized in that, The diameter of the inlet hole (71) is D0; the diameter of the resonant hole (72) is D and the length is L; the diameter of the intermediate hole (73) is d and the length is S; the length of the outlet section is S1. ； S = (2-6)d; S1 = (3-7)d.

8. The elastic porous dielectric skin for an aircraft according to claim 7, characterized in that, The expression for calculating the diameter d of the intermediate hole (73) is: ； Where q is the injection flow rate of the injection hole (71), P is the upstream pressure, n is the number of bellows-type nozzles (7), and b is the flow correction coefficient.

9. The elastic porous dielectric skin for an aircraft according to claim 7, characterized in that, The expression for calculating the length L of the resonant aperture (72) is: ； Where d is the diameter of the intermediate hole (73), Modulus coefficient, The critical Strouhal number is... It is the Mach number.

10. A method for preventing icing of an aircraft's elastic porous medium skin based on any one of claims 1-9, characterized in that, Includes the following steps: After the jet control system is turned on, it provides a heat medium to the bellows-shaped nozzle (7); The heat medium flows sequentially from the inside to the outside of the elastic porous medium skin through the injection hole (71), the resonant hole (72), the intermediate hole (73) and the exit hole (74), melting the ice on the outside of the skin; Meanwhile, a micro-cavitation jet is generated in the near-outlet flow field of the nozzle of the aircraft's elastic porous medium skin, and the flow fields near the outlet of multiple accordion-shaped nozzles (7) are superimposed to generate a virtual aerodynamic shape to replace the deformable wing.

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