Ledge to vary shock wave structure

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a projection to modify the structure of the shock wave aerodynamic structure and a method of operating an aerodynamic structure comprising a projection for changing the structure of the shock wave extending from the surface of said structure.

BACKGROUND

When the aircraft is a transonic flight speed in excess of the design of the Mach number, there is a tendency to increase the intensity of the shock wave on the wing and to an increase in aerodynamic drag. At some point, the shock wave can be strong enough to cause separation and flow behind the shock wave, which in turn can induce a buffeting on the wing or control surface. This buffeting can vary from mild to severe and can result in high local dynamic loads, to vibrational noise or deterioration of controllability of the aircraft.

The phenomenon of buffeting induced shock wave is known, and to prevent it before the shock wave is used blade baffle (vane vortex generators, VVGs). Such a method is generally effective, however, it is associated with an increase in power loss due to parasitic aerodynamic drag, which is present throughout the range of operating flight conditions.

As described in Holden, HA and Babinsky, H. (2003) Shock / boundary layer interaction control using 3D devices, published in the collection 41st Aerospace Sciences Meeting and Exhibit, January 6-9, 2003, Reno, Nevada, USA, Paper no . AIAA 2003-447, when the transonic flow passes through the three-dimensional projection to change the structure of the shock wave, supersonic local conditions induce the formation of a diffuse base shock wave lambda-shaped structure.

US 2006/0060720 uses a projection control shock wave to create a shock wave propagating from the lower surface of the wing.

Disclosure of invention

A first aspect of the present invention provides a projection for changing the structure of the shock wave, comprising expanding tapered nose and tail, wherein the tail has at least one contour line in a plane with two concave opposite sides.

The protrusion for changing the structure of the shock wave according to the first aspect of the present invention has an improved shape with relatively low aerodynamic resistance. Furthermore, the concave shape of the tail promotes longitudinal vortex flows which in certain modes of operation may reduce buffeting induced shock wave.

Opposite sides of the contour line in plan may be convex and smoothly connect the rear edge of the lip to change the structure of the shock wave, or can be connected at a point to form a peak.

Typically protrusion to change the structure of the shock wave has a leading edge, a trailing edge, an inner edge and an outer edge. The protrusion may blend smoothly with the surface at its edges or there may be a sharp concave transition at one or more edges of the protrusion.

Typically protrusion to change the structure of the shock wave substantially no sharp convex edges or points.

A second aspect of the present invention provides an aerodynamic structure comprising one or more projections to modify the structure of the above type shock extending from the surface of said structure. Generally, each protrusion to change the structure of the shock wave has such a shape and is disposed so as to modify the structure of the shock wave, which was formed to the surface structure in the absence of the protrusions to change the structure of the shock wave, when the construct is moving at transonic speeds. This is in contrast to US 2006/0060720, where he delivered the shock wave control is used to create a shock wave that would not exist in the absence of the projection control shock wave.

A third aspect of the invention provides a method of operating an aerodynamic structure comprising a projection for changing the structure of the shock wave extending from the surface of said structure, said method comprising the steps of:

provide the structural work in the first mode, in which the flow from the protrusion to change the structure of the shock wave is substantially fully attached, and provide the work structure in a second mode in which the shock wave is produced at the surface of the aerodynamic structure, with the projection to change the structure of the jump seal changes the structure of the shock wave, and the flow is separated from the projection to change the structure of the shock wave to form a pair of longitudinal vortex flows.

Typically, the second mode is a higher flow rate and / or a higher lift coefficient than the first mode.

This structure can be a structure with an aerodynamic profile, in particular an aircraft wing, horizontal tail stabilizer or control surface, the structural member of an aircraft, in particular a cabin, pylon or fin, or any other kind of aerodynamic structure, in particular the turbine blade .

In the case of an airfoil protrusion to change the structure of the shock wave can be located on a high pressure surface of said structure (i.e., on the lower surface in the case of an aircraft wing) but more preferably the surface is a low pressure airfoil (ie ., the upper surface in the case of an aircraft wing). Additionally, the protrusion usually has an apex which is positioned closer to the trailing edge of the aerodynamic structure, in other words, it is positioned behind the 50% chord. The top of the protrusion may be a single point or a flat plot. In the case of the flat portion of the front edge of the planar portion is located closer to the trailing edge of the airfoil.

BRIEF DESCRIPTION OF DRAWINGS

The following describes the embodiments with reference to the accompanying drawings, in which:

Figure 1 - a top view of the top of an aircraft wing, the system comprising protrusions to change the structure of the shock wave according to the first embodiment, when operating in the normal mode of operation,

Figure 2 - a longitudinal section through the center of one of the projections on the axis AA in a normal mode of operation of the wing,

Figure 3 - is a plan view the top of the aircraft wing of Figure 1 in the abnormal mode of operation of the wing,

Figure 4 - a longitudinal sectional view through the center of one of the projections on the axis B-B in the abnormal mode of operation of the wing,

Figure 5 - is a cross-sectional view through the center of one of the projections on the axis C-C,

Figure 6 - is a plan view of one of the projections of the contour lines show the cumulative and

Figure 7 - a plan view of the top of an aircraft wing, the system comprising protrusions for changing the shock wave structure of the second embodiment of the invention.

EMBODIMENTS

Figure 1 shows a plan view of the upper surface of an aircraft wing. The wing has a leading edge 1 and a trailing edge 2, each of which is curved backwards relative to the free stream direction.

The upper surface of the wing comprises a system of three-dimensional projections to modify the structure of the shock wave extending from said surface. The system comprises a first group of projections 3 for changing the structure of the shock wave and a second group of projections 10 for changing the structure of the shock wave, located behind the first group.

Each protrusion 3 10 exits nominal surface 8 of the wing and the nominal surface 8 intersects the front edge 3a, 10a, the rear edge 3b, 10b, the inner edge 3c, 10c and the outer edge 3d, 10d. The lower part of all sides of the projection are concave and merge smoothly with the nominal surface 8. For example, the lower portion of the front side of the projection 9 in Figure 2 smoothly merges with the nominal surface 8 at leading edge 3a. Alternatively, there may be an abrupt transition at one or more edges of the protrusion. For example, the lower portion of the front side of the projection may be flat, as shown by the dashed line 9a. In this case, the front side of the projection 9a to change the structure of the shock wave has a sharp transition at the leading edge of the compound 3a with a nominal surface 8.

Figure 2 shows a sectional view through the center of one of the projections 3 on the axis A-A parallel with the free stream direction. The top 7 longitudinal section A-A is displaced as the center of the projection 6.

Apex 7 of each projection 3 placed behind the 50% chord, typically - between 60% and 65% chord.

At transonic speeds the shock wave is formed normal to the top surface of the wing. Figures 1 and 2 show the position of the shock wave 4, when the aircraft is flying with a Mach number and lift coefficient, which together define the normal mode of operation (usually associated with a phase of cruising range of operational modes of flight). In this normal mode of operation using the projections 3 for changing the structure of the shock wave and positioned so as to induce the formation of a blurred base 5 in the shock 4 seals lambda-shaped structure as shown in Figure 2, wherein the flow of the second group of projections 10 to change the structure of the shock wave is completely attached.

When the protrusions 3 to change the structure of the shock wave function optimally for their operation, i.e. when the shock seal 4 is located directly before the apex 7 of the projection, as shown in figure 2, base 5 has blurred the lambda-shaped structure with one front discontinuously 5a seal around the front edge of the ledge and jump to one rear seal 5b, located directly in front of the apex 7. Alternatively, instead of a single front seal jump 5a blurred base can be a lambda-shaped structure with the fan group of the front shocks.

The second group of protrusions 10 for changing the structure of the shock wave is used to change the structure of the jump 11 seal, which is formed at the surface of the wing when the aerodynamic structure operates at a higher Mach number or lift coefficient associated with an abnormal mode of operation as shown in Figures 3 and 4 . When the lift coefficient or Mach number increases, the shock moves back to the position 11 shown in Figure 3, the protrusions 10 to change the structure of the shock wave are arranged in such a way as to induce the formation of a blurred base 15 shock with a lambda-shaped structure, as shown in Figure 4.

It should be noted that, unlike vortex generators tabs have no sharp convex edges or points so the flow remains attached to the protrusions, if they work in an optimum mode (i.e. when the shock wave is located on a ledge just before its apex). A characteristic feature of three-dimensional projections to modify the structure of the shock wave is that the deviation from the optimal mode, i.e., when the shock wave is located on the ledge, but ahead of the vertex of the projection, the flow behind the lip tends to separate. This separation of the back projection used to form a pair of longitudinal eddy currents 12, 13 rotating in opposite directions, in the direction of the incoming flow, which has a positive impact on the buffeting at high speeds similar to VVG. These eddy currents in the surface layer comprises or pass directly over it. When in normal cruise flight mode, as shown in Figure 1, the flow is fully attached and parasitic drag characteristic for VVGs, is excluded. Thus, the projections 10 for changing the structure of the shock wave provide increased range of operating conditions and flight speed range or decreasing loads at high speed.

The second group of protrusions to change the structure of the shock wave somewhat offset relative to the first group, therefore, none of the projections 10 is to change the structure of the shock wave in the second group is not located directly behind any protrusion 3 to change the structure of the shock wave of the first group.

Figure 5 shows a side sectional view through the center of one of projections 10, and Figure 6 - a group of contour lines in the plane (equivalent to contour lines on a map) including a continuous contour line of the base, wherein the protrusion to change the structure of the shock wave merges with the upper surface of the wing, an intermediate contour line 25 and an upper contour line 24. The contour line comprises a flared base 20 and a nose tapering tail with concave opposite sides 22, 23 which intersect at a peak point 21 at the trailing edge of the projection. The tail portion of the intermediate contour line has two concave sides which become convex and meet at the trailing edge of the contour line 25. The protrusion 10 for changing the structure of the shock wave has lateral symmetry relative to its longitudinal center axis 26.

Details form each protrusion 10 for changing the structure of the shock wave can be selected in accordance with the shape shown in the drawing, so that in the normal mode of operation on the projection thread has been completely connected, as shown in Figure 1. In the higher Mach number or lift coefficient as shown in Figure 3, there will be a useful base change shock in addition to the formation of two longitudinal vortex flows.

This is expected to reduce the level of buffeting, the same level achieved by VVG. This concept can be applied to other aerodynamic structures, in particular to turbine blades, aircraft cabins, pylons, tail unit.

In the embodiment shown in Figure 1, the wing system includes projections to modify the structure of the shock wave includes a first group of projections 3 for changing the structure of the shock wave with an elliptical base and a second group of peaks 10 to change the structure of the shock wave, located behind the first group. However, the scope of the invention includes various other embodiments, including:

one nib to change the structure of the shock wave,

one group of peaks to modify the structure of the shock wave (ie, elliptical tabs to change the structure of the shock wave 3 excluded) located in the same "standard" position, and that the first group of protrusions 3 to change the structure of the shock wave in Figure 4 .

one group of peaks to modify the structure of the shock wave (ie, elliptical tabs to change the structure of the shock wave 3 excluded) located in the same "abnormal" position as the second group of projections 10 to change the structure of the shock wave in Figure 1 .

system to modify the structure of the projections shock, comprising two groups of peaks for changing the structure of the shock wave in the same positions as the projections 3 in Figure 1.

Figure 7 shows a plan view of the upper surface of an aircraft wing according to a second embodiment of the present invention. The embodiment shown in Figure 7 is identical to the embodiment of Figure 1, except that in this case, the first group comprises ten projections 3 for changing the structure of the shock wave and is provided only one rear protrusion 10 for changing the structure of the shock wave. Figure 7 shows the displacement of spikes 4, seal 11 along the wing. It can be seen that the jump four seals extend over a substantial part of the wing span, while the leap seal 11 is relatively short and therefore requires only a small number of rear protrusions to change the structure of the shock wave (in this case only one).

The present invention has been described with reference to one or more preferred embodiments, however, it should be understood that it is susceptible to various changes and modifications without departing from the scope of the invention defined by the appended claims.