WO2014178205A1

WO2014178205A1 - Surface flow control system and surface flow control method

Info

Publication number: WO2014178205A1
Application number: PCT/JP2014/052105
Authority: WO
Inventors: 東潤郭; 良稲上田
Original assignee: 独立行政法人宇宙航空研究開発機構
Priority date: 2013-04-30
Filing date: 2014-01-30
Publication date: 2014-11-06
Also published as: JP6029068B2; JP2014214851A

Abstract

The purpose of the present invention is to provide a surface flow control system, with which laminarization of the boundary layer can be controlled over a broad range from low velocity to high velocity regardless of the form of the moving body and which has good efficiency and a simple structure that comprises only electric means, and a surface flow control method. A surface flow control system for controlling a plasma actuator provided on the surface of a moving body that moves relative to a fluid, wherein the plasma actuator is disposed near the front edge and is configured so that the plasma actuator can be controlled so as to change the cross flow velocity component of the boundary layer flow of the fluid on the surface of the moving body.

Description

Surface flow control system and surface flow control method

The present invention relates to a surface flow control system and a surface flow control including a moving body that moves relative to a fluid, a plasma actuator provided on a surface of the moving body, and a control unit that controls the plasma actuator. More particularly, the present invention relates to a surface flow control system and a surface flow control method suitable for aircraft wings.

The resistance acting on the moving body that moves relative to the fluid is divided into pressure resistance and frictional resistance. In particular, in the case of an aircraft, it is possible to improve fuel consumption by reducing these resistances.
Frictional resistance depends on the flow conditions in the boundary layer, and the laminar flow has a lower frictional resistance than the turbulent flow, and the flow around the aircraft in flight is maintained in a laminar flow, greatly reducing the frictional resistance. To contribute, it is desirable to laminate the flow around the aircraft, such as wings.
The aerodynamic phenomenon in which boundary layer flow changes from laminar flow to turbulent flow can be broadly divided into two types: TS (Tollmien-Schrichting) instability and CF (Cross-Flow) instability. Can be mentioned.
In particular, transition due to C—F instability is a dominant factor causing transition in an object shape having a large receding angle (for example, a swept wing of an aircraft).
When the transverse flow velocity component is large with respect to the direction of the boundary layer outer edge flow, the CF instability develops remarkably, and as a result, the boundary layer transitions from laminar flow to turbulent flow.

When the main wing form has a large receding angle, such as a supersonic aircraft, the transition from laminar flow to turbulent flow is caused by cross-flow instability.
This is a transition mechanism that occurs due to the dominant cross-flow component in the boundary layer due to the pressure gradient in the blade span direction.
For this reason, in the conventional technology, laminar airfoil with suppressed CF instability has been mainstream by adopting a fuselage shape that does not generate pressure distribution in the blade span direction. Since it is constrained by the wing shape due to laminar wing in the state, there is a problem that it cannot always have the optimum aerodynamic performance in a wide flight region from low speed to high speed flight region during takeoff and landing and cruise flight.

On the other hand, there is known one that controls the flow of fluid by a plasma actuator provided on the surface of a moving body that moves relative to the fluid (see

Patent Documents

1, 2, 3, etc.).
All of these known ones control the separation of the boundary layer of the fluid on the surface of the moving body or the downstream flow by generating a vertical airflow with respect to the surface of the moving body.

JP 2007-317656 A JP 2008-290710 A JP 2012-047067 A

Known in Patent Documents 1 to 3 and the like control the separation of the boundary layer or control the flow on the downstream side by generating an air flow in the direction perpendicular to the surface of the moving body. It was impossible to control the transition from laminar flow to turbulent flow, and laminarization of the boundary layer was still dependent on the relative velocity between the airframe shape and the fluid.
In addition, in order to control boundary layer transition by suppressing CF instability, a method of injecting a jet stream into the boundary layer or sucking a flow in the boundary layer can be considered. In addition, there is a structural and efficient problem that a lot of energy needs to be supplied.

Therefore, the present inventor changes the CF instability by changing the transverse flow velocity component of the boundary layer flow of the fluid on the surface of the moving body by the plasma actuator, so that the instability can be changed regardless of the shape of the moving body. This led to a completely new idea that the laminarization of the boundary layer can be controlled in a wide range up to high speed.
That is, the present invention can control the laminarization of the boundary layer in a wide range from low speed to high speed regardless of the shape of the moving body, and has an efficient surface with a simple structure using only electric means. It is an object to provide a flow control system and a surface flow control method.

A surface flow control system according to the present invention includes a moving body that moves relative to a fluid, a plasma actuator provided on a surface of the moving body, and a control means that controls the plasma actuator. In the control system, a front end edge of the moving body is formed to extend in a direction not perpendicular to a moving direction of the fluid, the plasma actuator is disposed in the vicinity of the front end edge, The control means is configured to control the plasma actuator so as to change the transverse flow velocity component of the boundary layer flow of the fluid on the surface of the moving body, thereby solving the problem.

A surface flow control method according to the present invention controls a plasma actuator provided on the surface of a moving body that moves relative to the fluid to change the boundary layer flow of the fluid on the surface of the moving body. And the said subject is solved by inducing the flow which changes the transverse flow velocity component of the boundary layer flow of the fluid of the said moving body surface with the said plasma actuator.

According to the surface flow control system of the first aspect of the present invention, the front end edge of the moving body extends in a direction that is not perpendicular to the moving direction of the fluid. The transition to the flow is a factor in which the CF instability dominates, and the plasma actuator is arranged in the vicinity of the front edge, and changes the transverse flow velocity component of the boundary layer flow of the fluid on the moving body surface. Therefore, it is possible to control the laminar flow of the boundary layer in a wide range from low speed to high speed regardless of the shape of the moving body, and it is possible to control it efficiently with a simple structure using only electrical means. It becomes.

The plasma actuator generates a volume force near the surface in the boundary layer, induces a flow along the surface (counder effect), and induces a flow by the plasma actuator in the opposite direction of the transverse flow velocity direction that induces the transition. It is possible to suppress the development of the velocity component, to suppress the transition caused by the lateral flow instability, and to reverse the transition by inducing the flow in the direction of the lateral flow velocity.
Also, transitions due to cross-flow instability often predominate near the front edge of the wing, and when other devices are applied near the front edge where the boundary layer is very thin, the increase in pressure resistance depends on the device. Although the unevenness may promote the boundary layer transition, it is possible to control only the lateral flow velocity component without changing the pressure resistance by arranging the plasma actuator in the vicinity of the front edge.
Furthermore, since the transverse direction component is slower than the mainstream direction velocity, a sufficient effect can be obtained by the control by the plasma actuator.

According to the second aspect of the present invention, the plasma actuators are arranged in multiple stages at a predetermined interval from the vicinity of the front edge, so that the lateral flow velocity component can be controlled in a wider range in the flow direction. Further, it becomes possible to control more reliably.
According to the configuration of the third aspect of the present invention, the control means is configured to be able to control the plasma actuator so as to reduce the transverse flow velocity component of the boundary layer flow of the fluid on the surface of the moving body. Transition from laminar flow to turbulent flow due to the qualitative property can be suppressed, and frictional resistance can be reduced.
According to the configuration of the present invention, since the moving body is a retreating wing of an aircraft, in a supersonic aircraft or the like, without being constrained by a wing shape for laminar wing in a certain flight state, Optimum aerodynamic performance can be obtained in the low-speed flight region during cruise flight from take-off and landing and in the wide flight region of the high-speed flight region.
According to the configuration of the fifth aspect of the present invention, the control means is configured to be able to control the operation of the plasma actuator in accordance with the relative velocity between the moving body and the fluid, so that the boundary in a wide range from low speed to high speed. The laminar flow can be optimally controlled.

According to the surface flow control method according to the sixth aspect of the present invention, the plasma actuator provided on the surface of the moving body that moves relative to the fluid is controlled to control the lateral flow velocity of the boundary layer flow of the fluid on the surface of the moving body. By changing the components, it is possible to control the laminarization of the boundary layer in a wide range from low speed to high speed regardless of the shape of the moving body, and to control efficiently with a simple structure using only electrical means. It becomes possible to do.
According to the configuration of the seventh aspect of the present invention, by inducing a flow that reduces the transverse flow velocity component of the boundary layer flow of the fluid on the surface of the moving body by the plasma actuator, the layer of the boundary layer is surely caused by the instability of the transverse flow. Transition from flow to turbulent flow can be suppressed, and frictional resistance can be reduced.

Explanatory drawing of the flow of the position of 100 mm from a wing outer edge and center. The graph of the transverse flow component by the numerical analysis of FIG. The graph of the transition analysis of the boundary layer flow of the state of FIG. The graph of Psi in the state of FIG. Graph of transition analysis of boundary layer flow when cross flow is zero. 6 is a graph of Psi in the state of FIG. Model explanatory drawing of the surface flow control system which concerns on one Embodiment of this invention. Sectional explanatory drawing of the plasma actuator of FIG. Graph of wing surface flow velocity. Boundary layer profile graph. Graph of wing surface velocity at other conditions. The graph of the surface velocity of the wing in other conditions.

100 ... Wing 110 ... Plasma actuator 111 ... Electrode 112 ... Dielectric layer

The surface flow control system of the present invention is a surface flow control system comprising a moving body that moves relative to a fluid, a plasma actuator provided on the surface of the moving body, and a control means for controlling the plasma actuator. The front end edge of the moving body is formed to extend in a direction not perpendicular to the moving direction of the fluid, the plasma actuator is disposed in the vicinity of the front end edge, and the control means is provided on the surface of the moving body. The plasma actuator can be controlled so as to change the transverse flow velocity component of the boundary layer flow of the fluid. Laminarization of the boundary layer in a wide range from low speed to high speed regardless of the shape of the moving body As long as it is controllable and efficient with a simple structure using only electric means, any specific embodiment may be used.

The surface flow control system and the surface flow control method according to the present invention will be described in more detail.
For example, as shown in FIG. 1, for a wing having a width of 250 mm from the center, a receding angle of the front edge of 60 °, and an angle of attack (AOA) of 3 °, when the flow velocity (U) is 19 m / s, the blade is 100 mm from the center. In position, it creates a surface flow, roughly as shown by the dotted line.
When the flow field at this position was analyzed by numerical analysis (CFD), it was found that there was a transverse flow velocity component as shown in FIG.
Where C is the blade length, X is the distance from the front edge, Z (mm) is the height from the blade surface, and V (m / s) is the transverse flow (blade tip method (bottom of Fig. 1 Direction) is a positive speed component, and the center direction (upward in FIG. 1) is a negative speed component.

In this condition, transition analysis of a boundary layer flow (e ⁿ method) the result of, as shown in FIG. 3, and N value abruptly increases in the vicinity of the front edge of the wing, thereby, the front end It can be seen that a transition from laminar to turbulent flow is likely to occur near the edge.
The main factor of the N value shown in FIG. 3 can be determined from the characteristics of Psi shown in FIG. Since Psi in FIG. 4 is not 0, it is indicated that the N value in FIG. 3 is an N value developed by the transverse flow component.
From these analysis results, in the case of a blade with a receding angle of 60 degrees, it is determined that the boundary layer transition is a transition caused by CF instability.
When the lateral flow component is forcibly set to 0 under the above conditions, the N value distribution decreases rapidly as shown in FIG. Then, as shown in FIG. 6, the Psi value is 0, and the N value in FIG. 5 is determined to be a transition caused by TS instability.
When the above analysis results are combined, the boundary layer transition is a transition due to CF instability due to the lateral flow component, and it can be understood that the possibility of the boundary layer transition is greatly reduced when there is no lateral flow.

As shown in FIG. 7, the surface flow control system according to an embodiment of the present invention is formed on the surface near the front edge of the above-described blade (width 250 mm from the center, receding angle 60 ° of the front edge). A plasma actuator having a length of 100 mm centering on a position 100 mm from the center is provided, and a control means (not shown) controls the output of the plasma actuator to change the transverse flow velocity component of the boundary layer flow.
As shown in FIG. 8, the plasma actuator 110 is a dielectric barrier discharge plasma actuator in which two electrodes 111 are provided on both surfaces of the dielectric layer 112 so as to be shifted in position, and is embedded along the surface of the blade 100. Is installed.
Further, the voltage applied to the two electrodes 111 of the plasma actuator 110 is controlled by a control means (not shown).

A wind tunnel experiment was performed on the blade 100 equipped with the above-described surface flow control system under conditions of an angle of attack (AOA) of 4 ° and a flow velocity (U) of 10 m / s.
The transition position of the boundary layer flow from laminar flow to turbulent flow can be determined by the flow velocity (Up) of the blade surface measured by a Preston tube having a diameter of 1 mm.
In other words, in the case of laminar flow, the flow velocity is small near the surface, and the flow velocity suddenly increases as it moves away from the surface, but in the case of turbulent flow, the flow velocity near the surface is slightly larger and as it moves away from the surface. It is known that the flow rate gradually increases.
Therefore, the position where the flow velocity (Up) measured by the Preston tube changes from the low level to the high level can be determined as the transition position from the laminar flow to the turbulent flow of the boundary layer flow.

As a result of the wind tunnel experiment, as shown in FIG. 9, the transition position of the boundary layer flow from the laminar flow to the turbulent flow was 250 mm from the front edge when the plasma actuator was not used. When a voltage of 13 kV was applied to the actuator, the actuator retracted to a position 450 mm from the front edge.
Even in the boundary layer profile at the position of X = 400 mm (X / C = 0.39) in FIG. 7, as shown in FIG. 10, when the plasma actuator is not used, a turbulent flow profile is shown. When a voltage of 13 kV is applied, a laminar flow profile is shown, and it can be confirmed that the transition position of the boundary layer flow from the laminar flow to the turbulent flow is retreated.

FIG. 11 and FIG. 12 show the results of wind tunnel experiments conducted under conditions of an angle of attack (AOA) of 4 °, a flow velocity (U) of 15 m / s, an angle of attack (AOA) of 4 °, and a flow velocity (U) of 19 m / s.
Even under these conditions, it can be seen that the transition position of the boundary layer flow from laminar flow to turbulent flow is retreated by using the plasma actuator.
That is, it is possible to easily retreat the transition position from the laminar flow to the turbulent flow of the boundary layer flow by reducing the transverse flow velocity component using the plasma actuator.
Conversely, if the plasma actuator is operated so as to increase the transverse flow velocity component, the transition position of the boundary layer flow from laminar flow to turbulent flow can be advanced.

In the above embodiment, only one row of plasma actuators is provided parallel to the front edge, but any angle may be used as long as the lateral flow velocity component can be changed. Multiple stages may be provided at predetermined intervals, and different voltages may be applied to each stage.
This makes it possible to finely control the lateral flow velocity component over a wide range in the blade length direction, and to optimally control the transition position of the boundary layer flow from laminar flow to turbulent flow even under different conditions. . For example, in a supersonic aircraft, etc., the transition position from laminar to turbulent flow of the boundary layer flow should be displaced so as to be optimal in the low speed flight region during cruise flight from takeoff and landing, and in the wide flight region of the high speed flight region. Can be achieved and optimum aerodynamic performance can be obtained.

As described above, according to the present invention, it is possible to control laminarization of the boundary layer in a wide range from low speed to high speed regardless of the shape of the moving body, and with a simple structure using only electric means. The surface flow can be controlled efficiently.
The surface flow control system of the present invention is preferably applied to an aircraft, particularly a supersonic aircraft having a swept wing, but may be applied to a ship or a land mobile body, and the mobile body itself is a structure. Etc., and may be used in applications where only the fluid moves.
Further, the moving body may move relative to the fluid by rotating, such as a propeller or a windmill.

Claims

A surface flow control system comprising a moving body that moves relative to a fluid, a plasma actuator provided on a surface of the moving body, and a control unit that controls the plasma actuator,
The front end edge of the moving body is formed to extend in a direction not perpendicular to the moving direction of the fluid,
The plasma actuator is disposed near the front edge,
2. The surface flow control system according to claim 1, wherein the control means is configured to control a plasma actuator so as to change a transverse flow velocity component of a boundary layer flow of a fluid on the surface of the moving body.
2. The surface flow control system according to claim 1, wherein the plasma actuators are arranged in multiple stages at a predetermined interval from the vicinity of the front edge portion.
3. The surface according to claim 1, wherein the control means is configured to control a plasma actuator so as to reduce a transverse flow velocity component of a boundary layer flow of a fluid on the surface of the moving body. Flow control system.
The surface flow control system according to any one of claims 1 to 3, wherein the moving body is a swept wing of an aircraft.
5. The surface flow control according to claim 1, wherein the control unit is configured to be able to control an operation of the plasma actuator in accordance with a relative velocity between the moving body and the fluid. system.
A surface flow control method for controlling a plasma actuator provided on a surface of a moving body that moves relative to a fluid to change a boundary layer flow of the fluid on the surface of the moving body,
A surface flow control method characterized by inducing a flow that changes a transverse flow velocity component of a boundary layer flow of a fluid on the surface of the moving body by the plasma actuator.
7. The surface flow control method according to claim 6, wherein the plasma actuator induces a flow that reduces a transverse flow velocity component of a boundary layer flow of the fluid on the surface of the moving body.