Flow outlet

Abstract

A bleed flow discharge device for discharging bleed flow into a main fluid flow. The bleed flow discharge device has an outlet panel that comprises distinct first and second regions, both of which have bleed flow exit passages. The first region is at the downstream end of the bleed flow outlet panel relative to the main flow. The exit passages in the first region are closely aligned to a major axis of the outlet panel, whereas the exit passages in the second region have a component that points towards a perimeter edge of the exit panel. This arrangement results in good mixing of the bleed flow with the bypass flow, delayed attachment of the bleed flow onto the bypass duct surfaces, and low noise.

Claims

1. A bleed flow outlet panel for discharging bleed flow taken from a main flow through a gas turbine engine, the bleed flow outlet panel comprising: a perimeter edge formed around a major axis of the bleed flow outlet panel and defining its planform shape; and a plurality of exit passages, the exit passages being formed in at least two distinct regions of the bleed flow outlet panel, each region comprising a plurality of adjacent exit passages and at least two offset walls that are offset from the perimeter edge, wherein the exit passages in a first region are arranged to direct the bleed flow, in use, in a direction that has a greater component in the direction of the major axis than do the exit passages in a second region and each exit passage is defined at least in part by adjacent offset walls or by the perimeter edge and the offset wall immediately adjacent the perimeter edge.

2. The bleed flow outlet panel according to claim 1, wherein the first region is defined by a first angular segment of the bleed flow outlet panel, and the second region is defined by a second angular segment of the bleed flow outlet panel.

3. The bleed flow outlet panel according to claim 1, wherein all of the exit passages of the bleed flow outlet panel are formed in either the first region or the second region.

4. The bleed flow outlet panel according to claim 1, wherein the exit passages in the second region are arranged to direct the bleed flow, in use, in a direction that has a major component in the direction of the major axis of the bleed flow outlet panel.

5. The bleed flow outlet panel according to claim 1, wherein the bleed flow outlet panel comprises two walls that are spaced apart from each other and separate the first region from the second region.

6. The bleed flow outlet panel according to claim 1, wherein the perimeter edge of the bleed flow outlet panel comprises: a first curved portion that, in use, is positioned at a downstream end of the panel relative to a main flow into which the bleed flow exits; and a second curved portion that, in use, is positioned at an upstream end of the panel relative to a main flow into which the bleed flow exits, wherein the first region is defined at least in part by the first curved portion.

7. The bleed flow outlet panel according to claim 6, wherein: the perimeter edge of the bleed flow outlet panel is an elongate shape, having the first and second curved portions joined together by a first side edge and a second side edge; and the first region is defined by at least a part of the first curved portion and first and second dividing walls extending into the bleed flow outlet panel from first and second points on the first curved portion.

8. The bleed flow outlet panel according to claim 7, wherein the first and second dividing walls extend in a direction that is substantially perpendicular to the local perimeter edge.

9. The bleed flow outlet panel according to claim 1 having a generally planar shape defined perpendicular to the major axis.

10. The bleed flow outlet according to claim 1, wherein the total flow area of the exit passages in the second region is greater than the total flow area of the exit passages in the first region.

11. The bleed flow outlet panel according to claim 1, wherein the exit passages of the first region are arranged to direct the bleed flow within 5 degrees of the major axis of the bleed flow outlet panel.

12. The bleed flow outlet panel according to claim 1, wherein the exit passages in the second region are arranged to direct the bleed flow at an angle in the range of from 5 degrees to 40 degrees from the major axis of the bleed flow outlet.

13. The bleed flow outlet panel according to claim 1, wherein each exit passage in the second region is arranged to direct the bleed flow at substantially the same angle from the major axis as the other exit passages in the second region.

14. A bleed flow discharge device for a turbofan gas turbine engine for bleeding flow from a core flow through the gas turbine engine into a bypass flow of the gas turbine engine, the bleed flow discharge device comprising: a bleed flow duct through which, in use, the bleed flow taken from the core flow passes; and the bleed flow outlet panel according to claim 1 positioned at the exit of the bleed flow duct, through which, in use, the bleed flow passes from the bleed flow discharge device into the bypass flow.

15. The bleed flow discharge device for a turbofan gas turbine engine according to claim 14, wherein the second region of the bleed flow outlet panel is generally downstream of the first region relative to the direction of the bypass flow in use.

16. The bleed flow discharge device according to claim 14, further comprising a pressure reducing element in the bleed flow duct, the pressure reducing element comprising at least one flow contraction region and at least one flow expansion region arranged to reduce the total pressure of the bleed flow in the duct in use.

17. A method of manufacturing the bleed flow outlet panel according to claim 1 using additive layer manufacturing.

18. A method of manufacturing the bleed flow discharge device according to claim 14 using additive layer manufacturing.

19. A gas turbine engine comprising: an engine core through which core flow passes in use; a bypass duct arranged around the engine core and through which bypass flow passes in use; a bleed valve in communication with the core flow and arranged to be selectively openable to allow bleed flow to be bled from the core flow; and a bleed flow discharge device in communication with the bleed valve and arranged to discharge the bleed flow into the bypass flow, the bleed flow discharge device comprising: a bleed flow duct through which, in use, the bleed flow taken from the core flow through the bleed valve passes; and a bleed flow outlet panel through which, in use, the bleed flow passes from the bleed flow discharge device into the bypass flow, the bleed flow outlet panel comprising: a perimeter edge formed around a major axis of the bleed flow outlet panel and defining its planform shape; and a plurality of exit passages, the exit passages being formed in at least two distinct regions of the bleed flow outlet panel, each region comprising a plurality of adjacent exit passages, wherein the exit passages in a first region are arranged to direct the bleed flow, in use, in a direction that has a greater component in the direction of the major axis than do the exit passages in a second region, each region comprises at least two offset walls that are offset from the perimeter edge, and each exit passage is defined at least in part by adjacent offset walls or by the perimeter edge and the offset wall immediately adjacent the perimeter edge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings, in which:

(2) FIG. 1 is a schematic sectional view of a gas turbine engine;

(3) FIG. 2 is a schematic view of a bleed flow discharge device of the engine of FIG. 1;

(4) FIG. 3 is a schematic view of a bleed flow discharge device comprising a bleed flow outlet panel in accordance with an example of the invention;

(5) FIG. 4 is a schematic view of a bleed flow outlet panel in accordance with an example of the invention;

(6) FIG. 5 is a different schematic view of the bleed flow outlet panel shown in FIG. 4;

(7) FIG. 6 is a cross-sectional view through part of a bleed flow discharge device according to an example of the invention, including a bleed flow outlet panel in accordance with an example of the invention;

(8) FIG. 7 is a cross-sectional schematic showing the path of a bleed flow plume in the bypass duct of a gas turbine engine after it is discharged through a bleed flow discharge device and bleed flow outlet panel in accordance with an example of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) FIG. 3 shows a bleed flow discharge device 100 according to an example of the invention for use with a gas turbine engine. The bleed flow discharge device 100 may be used, for example, to bleed flow from a compressor at certain operating conditions as described in more detail above in relation to the bleed assembly 30 shown in FIGS. 1 and 2. Indeed, the bleed flow discharge device 100 described herein in relation to FIGS. 3 to 7 may be used with any gas turbine engine, such as the gas turbine engine 10 shown in FIG. 1. Accordingly, the bleed flow discharge devices/bleed flow assemblies shown by way of example in FIG. 1 are labelled 30/100, to indicate that the gas turbine engine 10 of FIG. 1 may comprise a bleed flow discharge device 100 in accordance with the invention, and thus may itself be in accordance with the invention.

(10) The bleed flow discharge device 100 shown in FIG. 3 may be used with a bleed valve (not shown in FIG. 3) to form a bleed assembly, which may itself be in accordance with the invention. The bleed flow discharge device 100 may be coupled at an upstream end (with respect to the bleed flow) to a bleed valve, for example at a mounting face 110 such as that shown in FIG. 3. Such a bleed valve may be in communication at one end with a respective compressor 14, 15 (as shown in FIG. 1) and with the bleed flow discharge device 100 at its other end. Also as described above in relation to FIGS. 1 and 2, in operation of the engine, part of the core engine air flow may be diverted through the bleed flow discharge device 100 by opening the bleed valve so that the bleed air flow passes from the respective compressors 14, 15 to be discharged into the bypass duct 22. By way of example, a bleed valve for use with the bleed flow discharge device 100 may be substantially the same as the bleed valve 34 described above in relation to FIG. 2.

(11) The bleed flow discharge device 100 comprises a bleed flow duct 120 and a bleed flow outlet panel 200. In use, the bleed flow passes through the bleed flow duct 120 and is discharged from the bleed flow discharge device 100 through the bleed flow outlet panel 200, for example into the bypass flow B of a gas turbine engine 10. In the example shown in FIG. 3, the bleed flow duct 120 is shown as comprising two parts coupled together at a joint. However, it will be appreciated that the bleed flow duct 120, and indeed the bleed flow discharge device 100 as a whole, may be manufactured in any desired number of parts, including as a single piece.

(12) An example of the a bleed flow outlet panel 200 is shown in greater detail in FIG. 4. The bleed flow outlet panel of FIG. 4 is a substantially planar structure having its major plane perpendicular to a major axis Y-Y. When in use, the major axis Y-Y may be substantially aligned with the radial axis of a gas turbine engine 10, although this need not necessarily be the case.

(13) The bleed flow outlet panel 200 comprises a first region 210 and a second region 220. The first region 210 and the second region 220 are separated from each other by a first wall 230 and a second wall 240. Each of the first wall 230 and the second wall 240 extends from a perimeter edge (which may be referred to as a perimeter edge wall) 250 to a centre (or centre region) 260 of the bleed flow outlet panel 200.

(14) The first region 210 comprises exit passages 212 and the second region 220 comprises exit passages 222 (not all of the exit passages 222 of the second region 220 are labelled in FIG. 4 simply to improve the clarity of the Figure). In use, the bleed flow exits the bleed flow discharge device 100 through the exit passages 212, 222 in the bleed flow outlet panel 200.

(15) The exit passages 212 of the first region 210 point in a direction P that is substantially parallel to the major axis Y-Y of the bleed flow outlet panel 200. As such, the bleed flow is discharged through the exit passages 212 of the bleed flow outlet panel 200 in a direction that is substantially parallel to the major axis Y-Y.

(16) The exit passages 222 in the second region point in directions Q (Q1, Q2, Q3) that have a component that points towards the perimeter edge 250 (that is, the closest point on the perimeter edge 250 to the respective exit passage 222), and a component that points in the direction of the major axis Y-Y. As such, the bleed flow is discharged through the exit passages 222 of the bleed flow outlet panel 200 in directions Q that have a component that points towards the perimeter edge 250, and a component that points in the direction of the major axis Y-Y.

(17) In FIG. 4, the flow through the exit passages 222 of the second region 220 is represented by arrows Q1, Q2, Q3. As illustrated in the FIG. 4 example, absolute direction Q1, Q2, Q3 of the flow passing through the exit passages 222 in the second region 220 may be different for different exit passages 222 depending on, for example, the direction to the closest point on the perimeter edge 250. Similarly, the absolute direction of the flow passing through an individual exit passage 222 of the second region 220 may be different at different points within that exit passage 222, for example if the individual exit passage has a curved shape in planview (that is, a curved shape when viewed from a direction aligned with the major axis Y-Y).

(18) By way of illustration, the flow represented by the arrow Q1 in FIG. 4 is shown resolved into two mutually perpendicular components: a first component Q1 that is parallel to the major axis Y-Y of the bleed flow outlet panel 200; and a second component Q1 that points towards the locally closest point on the perimeter edge 250. The flow Q through the exit passages 222 of the second region 220 may be resolved entirely into these two mutually perpendicular directions, for example with no other components of the flow.

(19) Any desired angle between the direction Q of the bleed flow exiting through the exit passages 222 of the second region 220 and the direction of the major axis Y-Y may be selected. For example, the angle may be in the range of from 5 degrees to 40 degrees, for example 10 degrees to 35 degrees, for example 15 degrees to 30 degrees, for example 20 degrees to 25 degrees. The precise angle may be chosen to suit a particular application.

(20) A smaller angle may provide reduced blockage (i.e. a larger effective flow area). This may be beneficial in reducing the total area of the bleed flow outlet panel 200, and thus reducing the total area of the opening in the inner surface of the bypass duct required to house the bleed flow outlet panel 200. Thus may have aerodynamic and/or weight and/or structural benefits. Additionally or alternatively, a larger effective area may mean that the flow velocity is reduced for a given bleed flow mass flow rate. This may be advantageous in reducing the noise generated from the flow exiting from the bleed flow outlet panel 200 into the bypass flow B.

(21) In some cases, having a larger angle (i.e. a larger component in the direction pointing towards the closest point on the perimeter edge 250) may result in better mixing of the bleed flow with the bypass flow B, although again this may be dependent on the geometry and/or application.

(22) In some arrangements, the direction P of the bleed flow through the exit passages 212 of the first region 210 is not precisely parallel to the major axis Y-Y of the bleed flow outlet panel 200. For example, the direction P may be in the range of from +/5 degrees of the direction of the major axis Y-Y.

(23) In some arrangements, the direction P of the bleed flow through the exit passages 212 of the first region 210 may be simply described as being more closely aligned with the major axis Y-Y than is the direction(s) Q of the bleed flow through the exit passages 222 of the second region 220. The direction P of the bleed flow through the exit passages 212 of the first region 210 may have a greater component in the direction of the major axis Y-Y than the component of the bleed flow through the exit passages 222 of the second region in the direction of the major axis Y-Y.

(24) Different exit passages 222 within the second region 220 may have the same or different angles between the flow direction Q and the direction of the major axis Y-Y. Accordingly, the bleed flow direction Q through a given exit passage 222 in the second region 220 may have the same or a different component pointing towards the locally closest point on the perimeter edge 250 to other exit passages 222 in the second region. For example, in certain applications, it may be desirable to have a different exit angle on opposite sides of the bleed flow exit panel 200 (thus, for example, in FIG. 4 the angles formed by the arrows Q1 and Q3 may be different) to avoid the relatively hot bleed flow impinging on a downstream feature in the bypass duct 22.

(25) As shown most clearly in FIGS. 4 and 6, the first region 210 (for example the centroid of the first region 210) may be downstream of the second region 220 (for example the centroid of the second region 220) relative to the bypass flow B into which the bleed flow is discharged through the exit passages 212, 222. As such, the bleed flow exiting in the direction P substantially parallel to (or more parallel to) the major axis Y-Y may be at the downstream side or region of the bleed flow outlet panel 200 relative to the bypass flow. This may reduce the likelihood of the bleed flow (for example a plume resulting from the bleed flow) attaching to the inner surface 27 of the bypass duct 22, thereby reducing the likelihood of thermal damage to the inner surface.

(26) In the example shown in FIGS. 4 to 7, the perimeter edge 250 (and thus the planform shape) of the bleed flow outlet panel 200 is a stadium, or racetrack shape, i.e. it has two offset straight edges 256, 258 joined together by curves 252, 254 which, in the example of FIGS. 4 to 7 are semicircles. However, the perimeter edge 250 could have any desired shape. Purely by way of non-limitative example, the perimeter edge 250 could be a rounded rectangle, circle, rectangle, ellipse, oval or any other suitable shape, such as any suitable elongate shape.

(27) In the example shown in FIGS. 4 and 5, the walls 240, 230 that separate the first region 210 from the second region 220 extend from points 232, 242 on the first semicircle 252 that joins the straight edges 256, 258. Again, the geometry of the bleed flow outlet panel 200 shown in FIGS. 4 to 6 is given by way of example only. Thus, for example, the dividing walls 230, 240 may extend from any desired position on the perimeter edge 250, for example any position on the first semicircle 252, including the endpoints thereof.

(28) In the example shown in FIGS. 4 and 5, the area of the second region 220 is greater than the area of the first region 210. As such, in use most of the bleed flow will pass through the exit passages 222 of the second region 220. However, in other examples this need not be the case, and the area of the first region 210 may be greater than the area of the second region 220.

(29) The second region 220 and/or the first region 210 may have one or more further walls extending from the perimeter edge 250 to the central region 260. A such, the second region 220 and/or the first region 210 may be said to be split into two or more sub-regions. In the example shown in FIGS. 4 and 5, the second region 220 is split into 5 sub-regions by four walls 272, 274, 276, 278. Such walls may at least in part define the exit passages 212, 222 and/or may provide rigidity to the bleed flow outlet panel 200.

(30) The exit passages 212, 222 may be formed in any suitable manner. In the example shown in FIGS. 4 and 5, each exit passage 212, 222 is formed by two of the walls 230, 240, 272, 274, 276, 278 together with two of the perimeter wall 250 and offset walls 282, 284, 286 (see FIG. 5). In the FIGS. 4 and 5 example, the offset walls 282, 284, 286 are directly offset from the perimeter wall 250 in planview (i.e. when looking along the major axis Y-Y). However, in general a bleed flow outlet panel 200 may comprise any number of interior walls that are arranged in any suitable manner to define the exit passages 212, 222 in the desired form. In some arrangements, the walls that at least in part define the exit passages 212, 222 may be (or may be referred to) as vanes.

(31) In some example, the bleed flow discharge device 100 may comprise one or more (for example one, two, three, four or more than four) pressure reducing elements. An example of such a pressure reducing element 300 is shown in cross-section in FIG. 6. A pressure reducing element 300 would typically be placed in bleed flow R upstream of the bleed flow outlet panel 200, as in the FIG. 6 example. The or each pressure reducing element 300 may be located between a bleed valve 34 and the bleed flow outlet panel 200. The or each pressure reducing element 300 is arranged to reduce the total pressure of the bleed flow R before it exits through the exit passages 212, 222. This reduction in total pressure means that the exit velocity through the exit passages 212, 222 into the bypass flow B is reduced, thereby reducing the noise generated by the bleed flow discharge device 100.

(32) Such a pressure reducing device 300 may take any suitable form, for example any form which causes at least one flow area reduction followed by at least one expansion. The expansion is typically a rapid expansion, resulting in flow separation and unsteady mixing, and thus a reduction in total pressure. Purely by way of example, the pressure reducing device may be a pepper pot, that is a plurality of holes formed in a sheet. By way of clarification, the form of the pressure reducing device 300 shown in FIG. 6 is merely schematic.

(33) Any method may be used to manufacture a bleed flow discharge device 100 and/or bleed flow outlet panel 200 according to the invention including, for example, casting or additive layer manufacture (ALM), such as direct laser deposition (DLD). Using ALM, it may be possible to generate the entire bleed flow outlet panel 200, or indeed the entire bleed flow discharge device (which may optionally include a pressure reducing element 300), as a single unit or part.

(34) FIG. 7 shows a schematic of a bleed flow plume Z being discharged into the bypass duct 22 during operation of a bleed flow discharge device 100 according to an example of the invention. As shown in the FIG. 7, the bleed flow P/Q exits the bleed blow discharge device 100 into the bypass flow B, and does not impinge on the inner wall 27 until a point 27A significantly downstream of the bleed flow discharge device 100, indicated by the distance 27B in FIG. 7. This means that the relatively hot bleed flow Z has significantly mixed and cooled before impinging on the inner wall 27 of the bypass duct 22, thereby reducing the possibility of thermal damage and/or reducing the need for expensive and/or heavy thermal protection.

(35) The distance 27B between the discharge of the bleed flow and impingement on the inner wall 27 may be increased over conventional arrangements at least in part due to the arrangement of the exit passages 212, 222 described and claimed herein. For example, the exit passages 222 in the second (downstream) region 220 may inhibit rapid attachment of the bleed flow P/Q onto the inner wall 27 by virtue of pointing the bleed flow in that region 220 substantially perpendicular to the bleed flow outlet panel 200, which may correspond to a direction that is substantially locally perpendicular to the inner wall 27 of the bypass duct 22 and/or to the bypass flow B.

(36) The arrangement of the exit passages 212, 222 described and claimed herein may also promote good mixing of the bleed flow P/Q (and the resulting bleed flow plume Z) with the bleed flow 22 into which it exits. For example, the exit passages 212 of the first region that point the bleed flow Q at least in part towards the perimeter edge 250 of the outlet panel 200 may result in very rapid turning of the bleed flow, generating high levels of turbulence in the resulting plume Z, which promotes rapid mixing (and thus cooling) with the bypass flow before impingement on the inner wall 27 at position 27A or impingement on the outer wall 26 at position 26A. This rapid mixing may also be advantageous in arrangements where the gas turbine engine 10 is provided with a thrust reverser unit (not shown in the Figures), and the bleed flow would be directed through the thrust reverser unit (for example through a thrust reverser unit vane cascade) when deployed. In this case, rapid mixing may be beneficial to prevent thermal damage to the thrust reverser unit (for example to the vane cascade thereof).

(37) Although the bleed flow outlet panel 200 and bleed flow discharge device 100 have been described herein in relation to discharging bleed flow into a bypass flow of a turbofan gas turbine engine, such a bleed flow outlet panel 200 and bleed flow discharge device 100 may also be used where a bleed flow exhausts overboard from an engine into an external flow. For example, in the case of a turboprop or open rotor engine a bleed flow may exhaust to atmospheric conditions external to the engine with the discharge device disclosed herein. Similarly, the present disclosure may be applied to a land based gas turbine, e.g. an aero-derivative or other gas turbine, for which a bypass duct may not be present and the bleed flow may be exhausted to atmospheric conditions. In other words, the discharge device of the present disclosure may exhaust into any flow field, including but not limited to discharge into a bypass duct.

(38) It will be appreciated that many designs and/or arrangements of features, such as (by way of example only) the precise arrangement of exit passages 212, 222, and the shape of the perimeter edge 250 other than those shown in and described in relation to the Figures and not explicitly described herein fall within the scope of the invention. Furthermore, any feature described and/or claimed herein may be combined with any other compatible feature described in relation to the same or another embodiment.