DE102012214734B3 - Portion of supersonic flow channel used in jet engine, has plane that is extended upstream of recess, and introducing portion and projection that are arranged in cross-section recess - Google Patents

Abstract

The portion (10) has a surface (12) that is provided with a fluid (30). A plane (32) is oriented in a main flow direction (14) over the surface. A cross-section recess (16) configured for inducing a fluid swirl (26), and is inducible. The plane is extended upstream of the recess and an introducing portion (18) and a projection (19) are arranged in the cross-section recess. The recess is extended transversely to the main flow direction in groove-shape. Independent claims are included for the following: (1) a supersonic flow channel; (2) a jet engine; (3) a lift device; and (4) a film with a structure for the reduction of flow resistance.

Description

TECHNICAL AREA

The invention relates to a body having at least one fluid-spillable surface with a global, parallel to a plane oriented main flow direction over the surface defining profile, wherein the surface with respect to the plane has a structure for reducing a flow resistance of the body Structure has at least one provided with a substantially circular section-shaped cross section recess for inducing a fluid vortex, so that the fluid vortex within the recess is inducible and can be localized substantially within the recess. Furthermore, the invention relates to a film having a corresponding surface structure.

STATE OF THE ART

In aircraft construction, but also, for example, in shipbuilding or in the construction of high-speed trains and motor vehicles, it is of great importance to obtain as low-resistance a shape as possible and also a surface with as little resistance as possible. The advantages of an aircraft, ship or vehicle with good flow characteristics, ie low flow resistance, are on the one hand in low energy consumption and thus fuel consumption, on the other hand higher speeds can be achieved with the same drive power. Overall, moving a body with low flow resistance so efficient by a fluid such. As air or water, which is particularly important at high energy costs.

In the US 2,899,150 A an aircraft wing is described which has a low surface friction in air. In this case, circular recesses are provided in groove form over the surface of the wing and transversely to the direction of flight and flow. In the recesses air swirls are created, which contribute to the reduction of the flow resistance of the wing.

In the US 6,363,972 B1 This idea is further pursued and various forms of recesses in the surface of a body provided, which is overflowed by air.

However, both structures have the disadvantage of still unsatisfactory high flow resistance.

From the WO 2011/091545 A1 There is a structure for reducing a flow resistance, which is very similar to the present structure and forms the preamble of the present independent claims. However, it has been found that this known structure is not yet optimal, especially for very high flow velocities far in the supersonic range, namely above Mach 3.

PRESENTATION OF THE INVENTION

The object of the invention is thus to further develop a body from the above technical field such that its flow resistance in a fluid for high flow velocities above the speed of sound, in particular above Mach 3, is further reduced.

This object is solved by the subject-matter of claims 1 and 13. Advantageous further embodiments are given by the subclaims. The subject of the invention is a body with at least one surface that can be overflowed by a fluid with a global, a parallel to a plane oriented main flow direction over the surface defining profile, wherein the surface with respect to the plane has a structure for reducing a flow resistance of the body. In this case, the structure has at least one recess provided with a substantially circular section-shaped cross-section for inducing a fluid vortex, so that the fluid vortex within the recess is inducible and can be localized substantially within the recess. The structure according to the invention has an inlet section arranged upstream of the recess, which runs parallel to the plane. Further, it has a downstream of the recess arranged projection which is acute-angled in its cross section.

The body thus has a surface that extends over a larger area. This can be both a plane and a curved surface (plane). Depending on the direction of flow of the body, the global course of the surface optionally defines a main flow direction of a fluid over the surface, so to speak an averaged flow direction. Small structures on the surface are only weak. The surface of the body according to the invention has a structure which comprises at least one recess with a substantially circular section-shaped cross-section and is suitable and designed for the induction of a fluid vortex. The structure further comprises an introduction section, which is on the one hand preceded by the recess in the direction of the main flow, so that a fluid flow overflowing the surface first passes through the introduction section. Further, the introduction section, unlike in through the WO 2011/091546 A1 formed prior art, parallel to that through the global surface of the Body defined and the main flow direction forming level. This means that with a globally horizontally extending surface, the introduction section is likewise oriented exclusively horizontally and is not inclined towards the recess. Furthermore, the structure according to the invention has a protruding from the plane away from the body projection which forms an acute angle in its cross section. Between the parallel to the plane extending introduction section and protruding from the plane projection is the protruding into the body recess, within which the fluid vortex is generated and localized. As a result of this structure, part of the fluid flow passing over the surface and passing through the introduction section is guided through the projection into the recess. In the recess, a fluid vortex is generated by the shape of the recess and by the fluid flow, which remains due to the shape of the recess substantially within the recess.

The diameter of the essentially circular section-shaped cross-section of the recess can preferably be 23 mm for air flowing at sea level under standard conditions (air temperature 15 ° C., air pressure 1013 hPa, relative humidity 0%) with Mach 3 over the surface. The preferred diameter increases linearly with the expected flow velocity of air. An empirical formula for the dimensioning of the recess for gases is d = 8 · v / 1200, where d is the diameter of the recess in centimeters and v the velocity of the fluid flow in km / h. The surface in the recess is preferably coated with TiO ₂ , whereby a particularly low flow resistance between the fluidized fluid located in the recess and the edge of the recess is achieved. The recess may also have a deviating from a circular cross-section.

That is, a part of the fluid flow flowing directly over the surface is reliably and efficiently converted into a fluid vortex (Helmholtzwirbel) by the introduction portion, the projection and the recess, which remains substantially within the recess. That the fluid vortex remains substantially within the recess means that most of the particles in the recess (molecules, atoms, etc.) of the fluid remain within the recess in a stationary vortex, ie are not led out of the recess.

The fluidized vortex located in the recess directs fluid particles over the fluid vortex and thus the protrusion with a sustained fluid flow. Since the fluid vortex has a rotational velocity, the velocity difference between the outer edge of the fluid vortex and the fluid flow directed directly above the fluid vortex is very small, so that the flow resistance of the body, which increases in proportion to the flow velocity, can also be kept very small. In the area of the fluid vortex, therefore, the fluid flow over the surface hardly comes into direct contact with the (stationary) body, but mainly with the outer edge of the vortex. Due to the inventive design of the introduction section, an even more effective reduction of the flow resistance at flow velocities of the fluid flow of Mach 3 and more is also possible.

In a preferred embodiment, the recess is extended substantially transversely to the main flow direction, in particular groove-shaped. When the recess extends across the body transverse to the main flow direction, the effect of the surface structure is greatest. An angular deviation of up to 45 ° from the perpendicular to the main flow direction still allows a significant reduction of the flow resistance over known structures. In a particularly preferred groove-shaped embodiment of the structure, the recess extends transversely to the main flow direction over the entire surface.

Advantageously, the structure has a plurality of recesses, wherein the recesses of the plurality are arranged one behind the other, in particular in the main flow direction. To each of the recesses, an introduction portion and a projection are respectively connected, which are respectively arranged upstream and downstream of each of the recesses. The structure is particularly effective when there are many successive recesses in the main flow direction on the surface of the body. As a result, a large area of the body can be provided with the structure and a particularly effective reduction of the flow resistance is therefore possible. In this case, subsequent particles of the fluid stream flowing over the surface of the body hardly strike the surface of the body itself, but are almost completely directed away from the surface by the fluid vortices. Here, the speed difference between the fluid flow layer closest to the surface and each of the fluid vortices is very small, and so is the flow resistance.

In the case of a plurality of recesses, it is particularly advantageous if adjacent recesses are spaced from each other by 2 to 6 times, in particular 3 to 5 times, the diameter of the circular section-shaped cross section. The distance between the Recesses is determined in each case between the centers of adjacent recesses. By such a dimensioned distance between the recesses, preferably in the direction of the main flow direction, a particularly large reduction of the flow resistance of the body is achieved.

Advantageously, the introduction section is rectilinear, d. H. it runs along a flat, non-curved surface.

In a preferred embodiment, the recess has a first edge located upstream in the main flow direction between the introduction section and the recess and a downstream second edge between the recess and the projection. In this case, the first edge is offset relative to the second edge substantially in the direction of the interior of the body in order to induce the fluid vortex in the recess. In this context, an edge is to be understood as an abrupt change in the surface orientation. It is present at the transitions between each recess and the surrounding parts of the surface, the lead-in section and the projection. Conversely, the fact that the first edge is offset substantially towards the interior of the body relative to the second edge means, conversely, that the second edge, as it were, protrudes away from the recess toward the first edge. The second edge is therefore another element that facilitates introduction of a fluid flow into the recess.

Advantageously, the furthest upstream location of the recess, d. H. the edge of the recess offset from the first edge towards the interior of the body to locate the fluid vortex substantially within the recess. The furthest upstream location of the recess is below the first edge. In this case, the location of the edge of the recess is meant, from which a fluid flow following the edge of the recess always has a component of movement in the downstream direction, ie it moves at least partially in the direction of the main flow direction. In the case of a circular section-shaped cross section of the recess, this point is a point with a tangent perpendicular to the main flow direction to the edge of the recess. That is, a fluid particle of the fluid vortex within the recess at the first edge at least partially moves in the direction of the main flow direction and not exclusively perpendicular to the main flow direction. This is a secure localization of the fluid vortex substantially connected within the recess.

In a preferred embodiment, the second edge is offset from the first edge of the recess by 0.4 times to 0.8 times, preferably by 0.6 times the diameter of the circular section cross section in the main flow direction. This arrangement of the second edge relative to the first edge of the recess in turn allows a particularly effective reduction of the flow resistance of the surface. This depends on the one hand with a secure localization of the vortex inside the corresponding recess, on the other hand with an effective introduction of the fluid into the recess in cooperation with the introduction section together.

Advantageously, the circular arc section of the cross section of the recess measures between 225 ° and 315 °, preferably between 260 ° and 290 °, so that the recess has an angular range of between 135 ° and 45 °, preferably between 100 ° and 70 °, of its cross section is open. The angular range of the opening depends on the expected speed of the fluid flow. A correspondingly dimensioned opening of the recess in turn serves for a particularly efficient reduction of the flow resistance of the surface and thus of the body, which is flowed over or around the fluid.

A flow channel according to the invention, in particular a supersonic flow channel, comprises a body as described above. This ensures a particularly low-friction fluid flow through the flow channel. In particular, the flow channel may be an ejection nozzle of a jet engine in which at least partially a fluid flow with supersonic velocity may be present, for example a Laval nozzle. An inventive jet engine and a buoyancy device according to the invention are also provided with a body described above. In this case, the buoyancy device, the flow channel or the jet engine preferably has a surface covered with fluid, which is essentially completely provided with the structure described above.

According to a further aspect of the invention, a film comprises a structure for reducing a flow resistance of a body which can be overflowed by a fluid in a main flow direction and onto whose surface the film can be applied, the surface of the body extending along a plane. In this case, the structure has at least one recess provided with a substantially circular section-shaped cross section for inducing a fluid vortex, so that the fluid vortex within the recess is inducible and can be localized substantially within the recess. The foil is through in that the structure has an introduction section upstream of the recess in the main flow direction for introducing a fluid flow into the recess which runs parallel to the plane. Furthermore, the structure has an acute-angled cross-section projection, which is arranged downstream of the recess. A film according to the invention is therefore suitable for producing a body according to the invention by coating a surface of an almost arbitrary body with the film.

A further aspect of the invention resides in the use of a surface structure overflowable by a fluid in a main flow direction, as described above, for inducing a fluid vortex in order to reduce a flow resistance of a body provided with the surface structure.

Further preferred embodiments will become apparent from the following description of the figures and the totality of the claims.

BRIEF FIGURE DESCRIPTION

The figure shows in a side sectional view a section of a body with a surface structure according to a preferred embodiment.

WAYS FOR CARRYING OUT THE INVENTION

The figure shows a side sectional view of a body 10 along a surface 12 of the body 10 that of a fluid 30 along a main flow direction 14 is overflowed. The body 10 has in the figure a global surface area extending along a plane 32 extends. The level 32 in the figure is straight, that is not curved. However, it is also possible that the level 32 is slightly curved. Then, the structure described below is formed against the curved global plane.

The surface 12 has a recess 16 which has a circular section-shaped cross-section and preferably has a surface of titanium dioxide or another substantially inert and / or friction-reducing surface. In mainstream direction 14 the recess 16 upstream, ie upstream, is an introductory section 18 the recess 16 formed, which is parallel to the plane 32 extends and the fluid flowing over it 30 in the direction of the recess 16 passes. At the transition between the introductory section 18 and the recess 16 the structure forms a first edge 20 , which is shown in cross-section as a slightly acute-angled tip. In mainstream direction 14 the recess 16 downstream, ie downstream, the preferred structure according to the invention has a projection 19 on top of that level 32 protrudes from. The lead 19 is formed in its cross-section strongly acute-angled, so that it has a sharp edge to be displayed in cross section as a tip 22 which is the main flow direction 14 opposes to a portion of the fluid 30 for an introduction into the recess 16 secede. The structure of the recess with its features is preferably in the direction of the main flow direction 14 periodically continues to the effect of each recess 16 including introductory section 18 and lead 19 to reinforce.

The sectional plane of the figure runs along the main flow direction 14 of the fluid 30 above the surface 12 of the body 10 , The recess 16 thus extends substantially transversely to the main flow direction 14 , out of the plane of the figure or into it. This also applies analogously to the introductory section 18 and the lead 19 as well as the associated edges 20 and 22 ,

Opposite the plane 32 has the recess 16 a depth T of 14 mm at a diameter D of 23 mm. The lead 19 is about 8 mm from the plane 32 out. The first edge 20 is at an opening distance r of 14 mm upstream of the second edge 22 , These dimensions are for a flow rate of air under (static) standard conditions of at least Mach 3 optimized and may vary depending on the desired flow rate range.

The first edge 20 and the second edge 22 limit an opening of the recess 16 , They thus define an angular range W, which can be referred to as the opening angle, in a center M of the recess 16 is measured and shown in the figure. The depth T of the lowest point of the recess 16 under the first edge 20 is in the preferred embodiment shown in the figure 0.6 times the diameter D of the corresponding recess. The second edge 22 is opposite the first edge 20 opposite to the depth direction, that is from the body 10 pointing away, offset.

The lead 19 is in the range of the second edge 22 strong acute-angled formed. Downstream of the second edge 22 the projection has a slight convex curvature, which is defined in the cross section of the figure by a radius of curvature R1. The radius of curvature R1 measures 57 mm in the illustrated preferred embodiment. In the transition between the arched ledge 19 and the subsequent surface 12 of the body 10 is about level 32 rounded with a radius of curvature R2, which is 12 mm in the illustrated embodiment. Downstream of this rounded transition preferably another closes parallel to the plane 32 extending inlet portion of a subsequent structure in the flow direction with introduction portion, recess and projection. By juxtaposing a plurality of recesses, the flow resistance of the body can be further reduced.

A the surface 12 overflowing fluid 30 , whose main flow direction 14 through the global history of the surface 12 is defined, arrives in his directly to the surface 12 adjacent area on the introduction section 18 , The introductory section 18 directs the fluid 30 towards the edge 22 of the projection 19 , which is a partial flow in the recess 16 conducts where indicated by the circular shape of the cross section of the recess 16 a fluid vortex 26 is induced. The second edge 22 divide it into the recess 16 introduced fluid flow 24 from a further fluid flow 28 that over the second edge 22 the recess 16 passed away. The continuing fluid flow 28 and all overlying layers will be through the fluid vortex 26 in the recess 16 with a very low flow resistance across the surface 12 of the body 10 directed.

The fluid vortex 26 in the recess 16 is due to the flowing fluid 30 permanently driven and remains as long as the fluid 30 over the surface 12 of the body 10 flows. Due to the high rotational speed of the vortex 26 There is only a minimal difference in speed between the fluid flow that continues to flow 28 and the fluid vortex 26 , Due to the minimal speed difference hardly creates flow resistance in the fluid vortex.

In addition, the fluid vortex forms an "air cushion", via which the further flowing fluid flow 28 is passed and through which the fluid flow 28 not or only barely in direct contact with the surface 12 of the body 10 even comes.

Claims (13)

Body ( 10 ) with at least one of a fluid ( 30 ) overflowable surface ( 12 ) with a global, a parallel to a plane ( 32 ) oriented main flow direction ( 14 ) over the surface ( 12 ) defining course, wherein the surface ( 12 ) in relation to the level ( 32 ) a structure for reducing a flow resistance of the body ( 10 ), wherein the structure has at least one recess provided with a circular section-shaped cross-section (FIG. 16 ) for inducing a fluid vortex ( 26 ), so that the fluid vortex ( 26 ) within the recess ( 16 ) is inducible and locatable within the recess, characterized in that the structure is parallel to the plane ( 32 ) extending and upstream of the recess ( 16 ) introductory section ( 18 ) and an acute cross-section and downstream of the recess ( 16 ) arranged projection ( 19 ) having. Body ( 10 ) according to claim 1, wherein the recess ( 16 ) transverse to the main flow direction ( 14 ) is extended, in particular groove-shaped. Body ( 10 ) according to claim 1 or 2, wherein the structure comprises a plurality of recesses ( 16 ), wherein the recesses ( 16 ) in particular in the main flow direction ( 14 ) are arranged one behind the other lying. Body ( 10 ) according to claim 3, wherein adjacent recesses ( 16 ), depending on the density, viscosity and temperature of the fluid, are spaced apart from each other, preferably by 2 times to 6 times the diameter (D) of the circular section cross section. Body ( 10 ) according to one of the preceding claims, wherein the introductory section ( 18 ) is rectilinear, Body ( 10 ) according to one of the preceding claims, wherein the recess ( 16 ) one in the main flow direction ( 14 ) upstream first edge ( 20 ) between the introductory section ( 18 ) and the recess ( 16 ) and a downstream in the main flow direction Second edge ( 22 ) between the recess ( 16 ) and the lead ( 19 ), wherein the first edge ( 20 ) opposite the second edge ( 22 ) towards the interior of the body ( 10 ) is offset to the fluid vortex ( 26 ) in the recess ( 15 ). Body ( 10 ) according to claim 6, wherein the furthest upstream location of the recess ( 16 ) opposite the first edge ( 20 ) towards the interior of the body ( 10 ) is offset to the fluid vortex ( 26 ) within the recess ( 16 ) to locate. Body ( 10 ) according to claim 5 or 7, wherein the second edge ( 22 ) opposite the first edge ( 20 ) is offset by 0.4 times to 0.8 times, preferably by 0.5 times the diameter (D) of the circular section-shaped cross section in the main flow direction. Body ( 10 ) according to one of the preceding claims, wherein the circular portion of the cross section the recess ( 16 ), depending on the density, viscosity and temperature of the fluid, between 225 ° and 315 °, preferably between 260 ° and 290 °, so that the recess ( 16 ) is opened over an angular range of between 135 ° and 45 °, preferably between 100 ° and 70 ° of its cross section. Flow channel, in particular supersonic flow channel, with a body ( 10 ) according to one of claims 1 to 9. Jet engine with a body ( 10 ) according to one of claims 1 to 9. Buoyancy device with a body ( 10 ) according to one of claims 1 to 9. Film having a structure for reducing a flow resistance of one of a fluid in a main flow direction ( 14 ) überströmbaren or umströmbaren body on the surface of the film is applied, wherein, the surface of the body along a plane ( 32 ), wherein the structure has at least one recess provided with a circular section-shaped cross-section (FIG. 16 ) for the induction of a fluid vortex ( 26 ), so that the fluid vortex ( 26 ) within the recess ( 16 ) is inducible and locatable within the recess, characterized in that the structure is parallel to the plane ( 32 ) extending and upstream of the recess ( 16 ) introductory section ( 18 ) and an acute cross-section and downstream of the recess ( 16 ) arranged projection ( 19 ) having.

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