Patent Application
20180065732
This application claims priority to European Patent Application EP 16 187 248.6 filed Sep. 5, 2016, the entire disclosure of which is incorporated by reference herein.
The present disclosure relates to a fluidic actuator and to a flow body, in particular for an aircraft.
Although it is possible to use surfaces around which fluid flows for many different applications, the present disclosure and the problem on which it is based will be explained in more detail with reference to aircraft surfaces around which fluid flows.
To control the separation of boundary layers on bodies with fluid flowing around them, in particular on airfoils of aircraft, pulses of compressed air are often blown onto the surface of the body around which the fluid flows. This is used to energize the boundary layer, thus preventing the boundary layer from separating and achieving favorable pressure distribution along the surface resulting in better lift and lower flow resistance of the flow body.
EP 2 650 213 A1 discloses a flow body comprising a fluidic actuator. The fluidic actuator comprises a blowing duct connected to an opening formed in a flow surface of the flow body and to a compressed air source. By a control pressure variation device, pulses of a pressurized fluid provided by the compressed air source can be produced through the openings in the flow surface.
The blowing ducts of this kind of fluidic actuator usually have to be positioned within the cross section of the flow body. This limits the available installation space. The flow direction of the pressurized fluid blown out, defined by both the course of the blowing duct and the openings in the flow surface, is thus often determined by structural conditions. In particular, it is often necessary to find a compromise between requirements in terms of fluid mechanics and structural requirements.
An idea of the present disclosure is to provide a fluidic actuator by which the fluid-mechanics properties of a flow body are improved and which can be easily integrated in the flow body.
Another idea of the present disclosure is to provide a flow body that is improved in terms of fluid mechanics.
According to a first aspect of the disclosure herein, a fluidic actuator for influencing a flow of a surrounding fluid along a flow surface is provided. The fluidic actuator comprises a blowing duct having an intake opening provided at its first end for connecting to a pressurized-fluid source, and a blowing opening provided at its second end for connecting to a surface blowing opening formed in the flow surface. Furthermore, the fluidic actuator comprises a suction duct having a suction opening provided at its first end for connecting to a surface suction opening which is formed in the flow surface and arranged at a distance from the surface blowing opening in a flow direction of the surrounding fluid. At its second end, the suction duct flows into the blowing duct at an entrainment opening provided or disposed between the first end of the blowing duct and the second end of the blowing duct.
According to an embodiment of the disclosure herein, therefore, a fluidic actuator having both a blowing duct for blowing a pressurized fluid at a flow surface and a suction duct for sucking fluid at the flow surface is provided. In particular, the suction duct flows into the blowing duct at an entrainment opening or recirculation opening, and is thus connected to the blowing duct so as to conduct fluid. This design causes a mass flow of the pressurized fluid through the blowing duct and suction of fluid found in the suction duct into the blowing duct. This is referred to as “entrainment”. The pressurized fluid can thus be transported through the blowing duct and blown out through a surface blowing opening in the flow surface in order to influence the flow. At this opening, the mass flow exits as a jet at a jet exit angle relative to the flow surface. The described design of the fluidic actuator causes suction of fluid, i.e. the generation of negative pressure at the suction opening of the suction duct or surface suction opening, at a suction opening of the suction duct, which opening can be connected to a surface suction opening in the flow surface, by fluid being sucked out of the suction duct into the blowing duct as a result of the flow of the pressurized fluid through the suction duct. The negative pressure generated changes the jet exit angle of the exiting pressurized-fluid jet. In particular, the pressurized-fluid jet is deflected towards the surface suction opening. Therefore, the actual jet exit angle of the pressurized fluid is decoupled from the geometric exit angle determined by the course of the blowing duct or surface blowing opening as a result of the recirculation of the suction duct into the blowing duct of the fluidic actuator. Therefore, the blowing duct and the suction duct of the fluidic actuator can be positioned within a flow body in a space-saving manner. By the fluidic actuator, therefore, a jet vector control is produced, i.e. a targeted, variable adjustment of the flow direction of the pressurized-fluid jet. At the same time, the suction of fluid at the flow surface makes it possible to influence the jet exit angle of the pressurized fluid blown out at the flow surface in a targeted manner adapted to the fluid-mechanics conditions. Since the suction is brought about by entrainment as a result of the suction duct flowing into the blowing duct, no additional suction components are required. This creates a compact, space-saving design and reduces the weight of the fluidic actuator. The design of the fluidic actuator also means that no movable components are required to generate the negative pressure at the flow surface. This is a significant advantage in terms of the reliability and maintenance of the fluidic actuator.
According to another development of the fluidic actuator, the entrainment opening faces the blowing opening. The suction duct thus flows into the blowing duct at an angle of less than or equal to 90° to the longitudinal extension of the blowing duct. The flow into the duct can be approximately tangential. This reduces flow losses in the region of the entrainment opening and increases the efficiency of the entrainment.
Furthermore, between the entrainment opening and the blowing opening the blowing duct has a cross section that is greater than a cross section of the blowing duct between the intake opening and the entrainment opening. According to this development, the cross-sectional area of the suction duct is increased downstream of the entrainment opening in relation to a flow direction from the supply opening to the blowing opening of the suction duct. As a result, the flow rate of the mass flow, which is greater as a result of the entrainment out of the suction duct, can be controlled and thus any possible flow losses reduced.
According to a further embodiment of the fluidic actuator, a central body forms a blowing duct wall extending between the entrainment opening and the blowing opening of the blowing duct, and a suction duct wall. In particular, the central body is arranged between the blowing duct and the suction duct, and its opposite surfaces define each duct. This gives the fluidic actuator a particularly compact design. It also creates a high degree of freedom in the design of the surfaces of the central body that define the ducts, meaning the ducts can be produced having an extension in terms of flow losses in a simple and space-saving manner.
According to another embodiment, the fluidic actuator additionally comprises a supply variation device, by which a supply of a pressurized fluid, provided by the pressurized-fluid source, into the blowing duct can be controlled, the intake opening of the blowing duct being connected to an output of the variation device and it being possible to connect an inlet of the variation device to the pressurized-fluid source. The supply variation device in particular forms a control device for the pressurized-fluid mass flow being supplied to the blowing duct. The device can make it possible to blow out different mass flows depending on the fluid-mechanics requirements for the flow of a surrounding fluid along the flow surface.
The supply variation device can be designed such that the supply of the pressurized fluid into the blowing duct can be stopped periodically. This means that the pressurized fluid can be blown out in pulses, making it possible to introduce eddy structures into the flow of the surrounding fluid in a particularly effective manner, in order to prevent flow separation.
According to a second aspect of the present disclosure, a flow body comprising a flow surface over which a surrounding fluid is intended to flow in a flow direction is provided. The flow body comprises a fluidic actuator having a blowing duct having an intake opening provided at its first end for connecting to a pressurized-fluid source, and a blowing opening provided at its second end, which opening is connected to a surface blowing opening formed in the flow surface. The flow body also comprises a suction duct having a suction opening that is provided at its first end and connected to surface suction opening that is formed in the flow surface and arranged at a distance from the surface blowing opening in a flow direction of the surrounding fluid, the suction duct flowing, at its second end, into the blowing duct at an entrainment opening provided or disposed between the first end of the blowing duct and the second end of the blowing duct.
A flow body comprising a fluidic actuator is thus provided. The fluidic actuator can in particular be designed according to one of the aforementioned embodiments.
By the aforementioned option to decouple the geometric exit angle for the blowing duct or surface blowing opening in the flow body from the actual jet exit angle of the pressurized fluid that can be blown through the surface blowing opening, the fluidic actuator can be integrated in the flow body. In particular, mechanical strength requirements and fluid-mechanics requirements on the flow body can thus be taken into account at the same time and separately from one another. In particular, the fluid-mechanics properties of the flow body can be improved by the adjustability of the jet exit angle as a result of the suction duct of the fluidic actuator being connected to the surface suction opening in the flow body.
According to another development, the surface suction opening is arranged downstream of the surface blowing opening in relation to the flow direction of the surrounding fluid. In this way, the jet exit angle of the pressurized-fluid jet is reduced in relation to the flow direction, because of the deflection of the pressurized-fluid jet exiting from the surface blowing opening towards the surface suction opening. This allows the fluidic actuator to be integrated such that the blowing duct extends approximately perpendicularly or generally transversely to the flow surface, which is advantageous in terms of integrating the fluidic actuator in the flow body in a mechanically robust manner.
According to an alternative embodiment of the flow body, the surface suction opening is arranged upstream of the surface blowing opening in relation to the flow direction. As a result, the pressurized-fluid jet that can be blown out of the surface blowing opening can exit at a steeper angle relative to the flow direction of the surrounding fluid. This allows the fluidic actuator to be integrated such that the blowing duct extends approximately in parallel with or generally along the flow surface. This is particularly favorable in terms of integrating the fluidic actuator in very thin flow bodies having little available space.
According to another development of the flow body, a central axis of the blowing duct produced in the region of the blowing opening of the blowing duct forms an acute angle with a tangent produced on the flow surface at the site of the surface blowing opening. An acute angle can make influencing the surrounding flow particularly effective.
The acute angle between the central axis of the blowing duct and the tangent at the flow surface can be between 85° and 5°. Within this range, the surface blowing openings can be formed in the flow surface in a simple manner in terms of production. The acute angle can be between 60° and 15°. In this angular range, the flow of the surrounding fluid can be influenced in a particularly effective manner.
According to a third aspect of the disclosure herein, an airfoil for an aircraft is provided, comprising at least one flow body according to any of the aforementioned embodiments, the intake opening of the blowing duct of the fluidic actuator being connected to a pressurized-fluid source. When using the flow body as an airfoil component of an aircraft airfoil, the favorable properties thereof in terms of fluid mechanics because of the fluidic actuator, as well as the low weight thereof as a result of the simple design of the fluidic actuator, are particularly advantageous. In particular, the flow body can also be formed having particularly high mechanical stability because of the degree of structural design freedom provided by the fluidic actuator.
In this case, at least one flow body forms one of the airfoil components of the group consisting of or comprising the leading edge flap, trailing edge flap, main wing body, stabilizer and elevator. Because of the design of the fluidic actuator, there is a large structural play when integrating the actuator in the flow body, as set out above. This provides the advantage whereby the flow around a huge range of airfoil components of an aircraft can be influenced separately and effectively. In particular, the fluidic actuator also makes it possible to influence the flow even in relatively narrow airfoil regions or in those having a small cross-sectional thickness, e.g. the trailing edges of airfoils.
In this document, where directional details and axes are concerned, in particular directional details and axes relating to the course of physical structures, a course of an axis, direction or structure “along” another axis, direction or structure should be taken to mean that these, in particular the tangents produced at a given point on the structures, extend in each case at an angle of less than 45° to one another, for example less than or equal to 30°, and for example in parallel with one another.
In this document, where directional details and axes are concerned, in particular directional details and axes relating to the course of physical structures, a course of an axis, direction or structure “transversely to” another axis, direction or structure should be taken to mean that these, in particular the tangents produced at a given point on the structures, extend in each case at an angle of greater than or equal to 45° to one another, for example greater than or equal to 60°, and for example perpendicularly to one another.
Where “one-piece”, “single-piece”, “integral” components or components “in one piece” are mentioned, these should generally be taken as being present as a single part forming a material unit, and in particular as having been produced as such, it being impossible to detach one component from the other without destroying the material bond.
The disclosure herein will be described hereinafter with reference to the drawings, in which:
In the drawings, the same reference numerals denote like components or those with the same function, unless specified otherwise.
By way of example,
The flow body 100 also comprises at least one surface blowing opening 110 formed in the flow surface 100a. In particular, a plurality of surface blowing openings 110 can be arranged one behind the other in the flow body longitudinal direction L100. In the flow body 100 shown by way of example in
In addition to the surface blowing openings 110, the flow body 100 comprises at least one surface suction opening 120. In particular, a plurality of surface suction openings 120 can be arranged one behind the other in the flow body longitudinal direction L100. The surface suction openings 120 are arranged at a distance from one another in relation to a flow body depth direction D100 extending transversely to the flow body longitudinal direction L100. In
As shown schematically in
As shown in
The angle a10 can be between 85° and 5°. Within this range, the surface blowing openings 110 can be formed in the flow surface 100a in a simple manner in terms of production. For example, the angle is between 60° and 15°. In this angular range, the flow of the surrounding fluid can be influenced in a particularly effective manner.
As also shown in
Since the suction duct 20 flows into the blowing duct 10 at the entrainment opening 10, a pressurized-fluid mass flow flowing in a pressurized-fluid flow direction F from the first end 11 of the blowing duct 10 to the second end 12 of the blowing duct 10 causes fluid in the suction duct 20 to be sucked into the blowing duct 10. This “entrainment” of fluid found in the suction duct 20 leads to a mass flow of fluid through the suction duct 20 from the surface suction opening 120, to which the suction opening 21A of the suction duct 20 is connected, to the entrainment opening 22A. This is shown schematically in
As shown in
As can be seen in particular in
As shown in particular in
By adapting the parameters of the group consisting of or comprising the angle a10, the angle a20, the cross section c11, the cross section c12, the cross section c22 and the distance d, the exit angle a30 of the jet of the pressurized fluid blown out of the blowing opening 10 can be adjusted effectively.
In addition, a central body 30 arranged between the blowing duct 10 and the suction duct 20 can be provided, as shown in particular in
The central body 30 can in particular be designed as a hollow body, thereby reducing its weight. In particular, the central body 30 can be formed in one piece with, or be connected to, the structures or walls forming the suction duct 20 and/or the structure or walls forming the blowing duct 10. In addition, the central body 30 can be formed in one piece with, or be connected to, the structures or walls forming the flow surface 100a.
By the optional supply variation device 50 shown schematically in
By way of example,
As
Although the present disclosure has been explained by way of example above on the basis of embodiments, it is not limited thereto; instead it can be modified in many different ways. In particular, combinations of the above embodiments are also conceivable.
While at least one example embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16 187 248.6 | Sep 2016 | EP | regional |
