A film with micro vortex generators and a dimpled rough surface

Abstract

The application belongs to the technical field of passive flow control, and discloses a film with micro vortex generators and a rough surface with pits, which comprises a substrate, the substrate is attached to the surface of a component to be improved, and an improvement assembly is arranged on the side of the substrate away from the component to be improved; the improvement assembly comprises a plurality of micro vortex generators and a plurality of pits, and the micro vortex generators and the pits are arranged alternately and spaced apart; the micro vortex generators are arranged in the shape of a triangular pyramid, and the edges of the triangular pyramid are directed towards the direction of the fluid flow. The application has the advantages of simple structure, fast response, easy attachment and the like, and also preliminarily solves the problems of additional resistance optimization, structure optimization and negative effect of the effect in the non-working state, can effectively control various flow separation phenomena, is convenient to carry and replace, has little influence on the original profile, and can significantly improve the aerodynamic performance of the equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of passive flow control, and particularly relates to a film with micro vortex generators and a rough surface with pits. BACKGROUND

[0002] On the surface of an airfoil, a turbine blade, and the inner surface of an inlet, flow separation is prone to occur due to the combined action of frictional resistance and adverse pressure gradient. After flow separation occurs, the boundary layer thickens, further separates from the surface, and causes the dissipation of fluid energy in the turbulent boundary layer and the separation shear layer, which can reduce the lift of the airfoil, reduce the working efficiency of the turbine blade, and reduce the total pressure recovery coefficient of the inlet outlet section. Flow separation can also increase the drag of the aircraft, and in severe cases, can even cause flight accidents. To address this problem, a series of flow control technologies have emerged, mainly including active control and passive control. So far, the passive flow control schemes mainly include adding vortex generators, setting guide vanes, and using swirl vortex reducers, which mainly mix the fluid by setting protrusions or separation baffles at the separation position to obtain energy to overcome the adverse pressure gradient, thereby eliminating fluid separation. The most mature passive flow control technology is the vortex generator, but the traditional vortex generator cannot produce the maximum total pressure recovery, cannot be self-adjusted according to the working condition changes, and is not easy to meet the wide envelope working requirements. The additional drag caused by the traditional vortex generator is also increased, especially in the non-working state, i.e., the boundary layer does not separate, which causes a large additional shape drag. In addition, for the traditional vortex generator, each application surface needs to be designed with a corresponding flow generator specific configuration, which has no universality. Due to this reason, the application of the traditional vortex generator has great limitations.

[0003] Therefore, there is a need for a film with micro vortex generators and a rough surface with pits to solve the problems of difficult arrangement, poor effect, large resistance, and poor universality of the traditional vortex generator technology. SUMMARY

[0004] To solve the above technical problems, the present application provides a film with micro vortex generators and a rough surface with pits, which is easy to arrange, has little effect on the surface of the object, has little additional shape drag, and has good flow control effect.

[0005] To achieve the above purpose, the present application provides a film with micro vortex generators and a rough surface with pits, which includes a substrate, the substrate is attached to the surface of a component to be improved, and an improvement assembly is arranged on the side of the substrate away from the component to be improved.

[0006] The improvement assembly includes a plurality of micro vortex generators and a plurality of pits, and the plurality of micro vortex generators and the pits are arranged alternately and spaced apart.

[0007] The micro vortex generator is arranged in a triangular pyramid shape, and the edge of the triangular pyramid is directed to the flow direction of the fluid.

[0008] Preferably, the base of the micro vortex generator is an isosceles triangle, and the axis of the isosceles triangle is consistent with the flow direction of the fluid.

[0009] Preferably, the recess is arranged between the two micro vortex generators in the normal direction of the fluid flow.

[0010] Preferably, the edge of the recess is tangent to the extension line of the base of the isosceles triangle of the micro vortex generator, the distance between the midpoint of the recess and the midpoint of the adjacent isosceles triangle is a, and the distance between the base of the isosceles triangle and the recess in the flow direction of the fluid is b.

[0011] Preferably, the base comprises a plurality of insulating layers arranged in a stack, the micro vortex generator is attached to the surface of the insulating layer away from the component to be improved, and the surface of the insulating layer close to the component to be improved is adhesive and attached to the surface of the component to be improved.

[0012] Preferably, the material of the insulating layer is high-temperature-resistant polyimide.

[0013] Preferably, the material of the micro vortex generator is a carbon fiber reinforced composite material with thermoplastic polyimide as the base resin.

[0014] Compared with the prior art, the present application has the following advantages and technical effects: the present application discloses a film with micro vortex generators and rough surface recesses, which realizes flow separation control through the micro vortex generators and recess structures on the surface, and is used for attaching to the surfaces where flow separation occurs, such as the wing, turbine blade, and inlet wall, to generate disturbance to the incoming flow, induce vortex structure, and control the separated airflow; when the airflow passes through the rough surface film, the micro vortex generators with triangular slope shape induce vortex, and since the height is low, all the vortexes are injected into the 10% of the boundary layer thickness, and the surface recess effectively suppresses the interaction of the separated flow in the separation area, promotes the mutual mixing of the low-speed low-energy airflow in the boundary layer and the high-energy airflow in the main flow, suppresses the formation of low-pressure flow to vortex, and improves the ability of the low-speed fluid in the boundary layer to resist the adverse pressure gradient, thereby promoting the flow separation and reattachment. Since the height of the rough surface micro vortex generator is only 10% of the boundary layer thickness, the aerodynamic drag of the attached surface is greatly reduced, the film is easy to attach to various controlled profiles, and the additional cost under the non-design state is reduced under the premise of ensuring good flow separation control effect.

[0015] The present application has the advantages of simple structure, fast response, easy to paste and the like, and also preliminarily solves the problems of additional resistance optimization, structure optimization and negative effect of effect in non-working state, can effectively control various flow separation phenomena, is convenient to carry and replace, has little influence on original profile, and can significantly improve the aerodynamic performance of equipment. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of this application illustrated in the drawings are provided to explain the present application and are not meant to limit the present application. In the drawings:

[0017] Figure 1 is a schematic view of the micro vortex generator and the rough surface with pits of the present application;

[0018] Figure 2 is a top view of the micro vortex generator and the rough surface with pits of the present application;

[0019] Figure 3 is a sectional view of the micro vortex generator and the rough surface with pits of the present application;

[0020] Figure 4 is a partial enlarged view of A in the present application; Figure 3

[0021] In the drawing: 1, base; 2, vortex generator; 3, pit; 4, insulating layer. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0023] In order to make the above objects, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0024] Referring to Figures 1-4 The present embodiment provides a micro vortex generator and a rough surface with pits, which comprises a base 1, the base 1 is attached to the surface of a component to be improved, and the side of the base 1 away from the component to be improved is provided with an improvement assembly;

[0025] The improvement assembly comprises a plurality of micro vortex generators 2 and a plurality of pits 3, and the plurality of micro vortex generators 2 and the plurality of pits 3 are arranged alternately and spaced apart;

[0026] ​The micro vortex generator 2 is arranged in a triangular pyramid shape, and the side edges of the triangular pyramid are directed to the fluid flow direction.

[0027] Flow separation is one of the most important problems in fluid mechanics, which can cause the lift of a wing to decrease, the drag to increase, and even stall the aircraft. When the Reynolds number decreases, the surface of a low-pressure turbine blade will present a large area of laminar flow, causing the suction surface to separate. When the load of the low-pressure turbine blade increases, such flow separation and wall end secondary flow will deteriorate sharply, which will seriously affect the performance of the gas turbine. For an inlet, the inlet of a modern fighter is generally an S-shaped inlet, and the curvature of the inlet along the flow direction is too large, which can cause serious flow separation, resulting in a decrease in the total pressure recovery coefficient of the outlet section, and reducing the quality of the airflow entering the engine. In summary, flow separation can adversely affect the stability and structural safety of an aircraft / gas turbine. The present application discloses a rough surface film with micro vortex generators 2 and pits 3, which can realize flow separation control through the micro vortex generators 2 and pit 3 structures on the surface, and can be attached to the surfaces where flow separation occurs, such as the wings, turbine blades, and inlet walls. By disturbing the incoming flow, vortex structures are induced to control the separated airflow. When the airflow passes through the rough surface film, the micro vortex generators 2 with triangular slope shapes induce vortexes. Since the height is low, all the vortexes are injected into the 10% of the boundary layer thickness. The surface pits 3 effectively suppress the interaction of the separated flow in the separation area, promote the mutual mixing of the low-speed and low-energy airflow in the boundary layer and the high-energy airflow in the main flow, and inhibit the formation of low-pressure flow vortices. The interaction between the two improves the ability of the low-speed fluid in the boundary layer to resist the adverse pressure gradient, and promotes the reattachment of flow separation. Since the height of the rough surface micro vortex generator 2 is only 10% of the boundary layer thickness, the aerodynamic drag of the attached surface is greatly reduced, which is easy to attach to various controlled surfaces and reduces the additional cost under the premise of ensuring good flow separation control effect.

[0028] Further, the base 1 is preferably an insulating flexible layer, which serves as a base layer, facilitating the installation of the micro vortex generator 2 and the adhesion to the controlled surface. In addition, by using the base 1 as a base, the entire rough surface film can be formed into a sheet structure to reduce the impact on the aerodynamic shape of the controlled surface.

[0029] Further, the pits 3 are used to cooperate with the micro vortex generator 2 to assist and strengthen the action of the micro vortex generator 2. Under the dual action of the micro vortex generator 2 and the surface pits 3, the ability of the separated fluid to resist the adverse pressure gradient is greatly improved, the separated fluid is reattached, the mutual mixing of the low-speed and low-energy airflow in the boundary layer and the high-energy airflow in the main flow is further promoted, and the ability of the low-speed fluid in the boundary layer to resist the adverse pressure gradient is improved.

[0030] Furthermore, the depression 3 is made using an etching process and is located between the two micro eddy current generators 2. It has a depth of 2 mm and a diameter of 4 mm.

[0031] Further optimization involves designing the base of the micro vortex generator 2 as an isosceles triangle, with its axis aligned with the flow direction of the fluid. In this embodiment, the micro vortex generator 2 has an isosceles triangle base with a leg length of 4mm, a base length of 3mm, and a height of 3mm. Its axis aligns with the flow direction, and the height of the micro vortex generator 2 is only about 10% of the boundary layer thickness. This significantly reduces the additional resistance generated by the controlled surface and further minimizes the extra costs associated with non-design conditions.

[0032] In a further optimized design, the depression 3 is formed on the base 1, located between two micro vortex generators 2 in the normal direction of the fluid flow. The edge of the depression 3 is tangent to the extension of the base of the isosceles triangle of the vortex generator 2. The distance between the midpoint of the depression 3 and the midpoint of the adjacent isosceles triangle is 'a', and the distance between the base of the isosceles triangle and the depression 3 in the direction of fluid movement is 'b'. In this embodiment, the base of the isosceles triangle of the micro vortex generator 2 is tangent to the circle of the depression 3, and the distance from the midpoint of the base to the point of tangency between the extension and the circle is 'a' = 2 mm. In the direction of the flow, the micro vortex generators 2 and the depression 3 are arranged alternately, and the vertical distance from the base of the isosceles triangle of the micro vortex generator 2 to the center of the circular depression 3 in the downstream direction is 'b' = 4 mm.

[0033] Further optimization of the scheme: The substrate 1 comprises several layers of insulating layers 4 stacked together. The micro eddy current generator 2 is adhered and fixed to the surface of the insulating layer 4 away from the part to be improved, while the insulating layer 4 facing the part to be improved is adhesive and adheres to the surface of the part to be improved. The insulating layer 4 is made of high-temperature resistant polyimide. In this embodiment, the substrate 1 is formed by stacking several layers of flexible insulating layers 4. The eddy current generator 2 and the depression 3 are located on one side of the substrate 1, and the other side has strong adhesion to adhere to the surface of the controlled object, ensuring that it will not fall off. In this embodiment, the base layer uses Kapton tape, which is made of polyimide and each layer is 1mm thick. In this embodiment, four layers of Kapton tape are used, which is stacked to facilitate tight adhesion between the layers and to facilitate the application of the rough film device to the object surface. The entire installation and control process is simple. In addition, the stacking of multiple flexible insulating layers 4 facilitates the adjustment of the thickness of the substrate 1, thereby facilitating the control of the thickness within a reasonable range to ensure that the thickness meets the flow control requirements of the controlled surface. Furthermore, the substrate 1 can be replaced at any time.

[0034] Furthermore, the thickness of substrate 1 is 4 mm.

[0035] Further, the shape of the base 1 in this example can be cut according to the surface to be attached as needed, and the shape is determined according to the specific structure of the controlled profile. After being cut appropriately, the micro vortex generator 2 and the rough surface of the pit 3 should be attached to the separation point or separation line of the flow separation area, and should completely cover the separation point or separation line.

[0036] Further optimization scheme, the micro vortex generator 2 material is carbon fiber reinforced composite material with thermoplastic polyimide as base resin.

[0037] Working principle:

[0038] Refer to the attached Figure 2 When the fluid passes through the rough surface of the pit 3, the flow field is disturbed under the action of the micro vortex generator 2. The flow direction of the airflow passing through the leading edge of the micro vortex generator 2 will separate in a small range. This part of the small separation flow continues to flow through the side surface of the micro vortex generator 2 and develops backward, and a secondary separation is generated at the tail of the side surface to induce the generation of vortex. This vortex is a pair of strong reverse rotating vortexes. Under the action of the vortex, the position of the main flow area in the boundary layer is lowered, and the speed of the fluid near the surface is increased. Further, channels are formed between adjacent vortex generators 2. The channel vortex is generated by the separation flow of the micro vortex generator 2 in the channel. The channel vortex also lowers the high-energy fluid by entrainment, so that the kinetic energy of the boundary layer fluid is increased. The trailing edge of the triangular slope type micro vortex generator 2 has a certain width, which has a certain hindering effect on the separation flow, forming a wake. The mixing of the fluid in the wake area is strengthened, and the low-speed fluid in the boundary layer and the high-energy fluid in the main flow area are mixed with each other, which improves the ability of the boundary layer to resist the adverse pressure gradient and promotes the reattachment of the separated flow.

[0039] The existence of the pit 3 in the flow direction X makes the main flow position of the boundary layer move downward, and the position of the pit 3 is the main area of the wake area behind the micro vortex generator 2, which makes the mixing action of the wake area more intense. After the fluid flows through the rear slope surface of the micro vortex generator 2, it continues to flow downstream, but has a tendency to flow to the surface of the controlled profile. At this time, the pit 3 behind the micro vortex generator 2 makes the fluid flow directly into the pit 3, and then be lifted through the circular surface. This part of the low-energy airflow near the surface is mixed with the main flow above, and the kinetic energy is increased. The pit 3 in the Y direction is located in the middle of the channel between the vortex generators 2. The fluid flows through the channel, the flow passage is narrowed, and the flow velocity is increased. The pit 3 at this position has a shock effect on the accelerated fluid. After the surface pit 3 is increased, the size of the channel vortex is increased, and the effect of lowering the high-energy fluid by entrainment is also more intense, so that the kinetic energy of the boundary layer fluid is increased.

[0040] The whole structure has the advantages of simple structure, fast response, easy to stick and the like, and preliminarily solves the problems of additional resistance optimization, structure optimization and negative effect in non-working state.

[0041] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0042] The above-described embodiments are only preferred modes of the present application, and do not limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application as defined by the claims.

Claims

1. A film having micro vortex generators and a dimpled roughened surface, characterized by: The application relates to a base (1) which is attached to the surface of a component to be improved, wherein the side of the base (1) away from the component to be improved is provided with an improvement assembly; the improvement assembly comprises a plurality of micro vortex generators (2) and a plurality of cavities (3), and the micro vortex generators (2) and the cavities (3) are arranged in an alternating manner; the micro vortex generators (2) are provided in a triangular pyramid shape, and the edge of the triangular pyramid is directed towards the fluid flow direction; the bottom surface of the micro vortex generator (2) is an isosceles triangle, and the axis of the isosceles triangle is consistent with the fluid flow direction; the cavities (3) are arranged on the base (1), and the cavities (3) are located between two micro vortex generators (2) in the normal direction of the fluid flow; the edge of the cavity (3) is tangent to the extension line of the isosceles triangle bottom edge of the vortex generator (2), the distance between the midpoint of the cavity (3) and the midpoint of the adjacent isosceles triangle is a, and the distance between the isosceles triangle bottom edge and the cavity (3) in the fluid flow direction is b.

2. The film with micro vortex generators and dimpled rough surface of claim 1, wherein: the base (1) comprises a plurality of insulating layers (4) arranged in a stacking manner, the micro vortex generators (2) are attached to the surface of the insulating layer (4) away from the component to be improved, and the insulating layer (4) towards the component to be improved is adhesive and attached to the surface of the component to be improved.

3. The film with micro vortex generators and dimpled rough surface of claim 2, wherein: the material of the insulating layer (4) is high-temperature-resistant polyimide.

4. The film with micro vortex generators and dimpled rough surface of claim 2, wherein: the material of the micro vortex generator (2) is a carbon fiber reinforced composite material with thermoplastic polyimide as the base resin.

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