Abstract
A fan outlet assembly comprises a fan discharge nozzle having a radially inner platform, a radially outer platform arranged coaxially and in radial alignment with the radially inner platform and a circumferential array of outlet guide vanes (110) spanning an annulus defined by the radially inner platform and radially outer platform. An annular duct extends downstream from the circumferential array, the duct having a radially outer wall (112) contiguous with the radially outer platform and a radially inner wall (111) contiguous with the radially inner platform. In a region extending downstream from the circumferential array, the radially inner and outer platforms and/or the radially inner and outer walls having a non-axisymmetric surface bounding the duct. A non-axisymmetric surface may be applied to either or both of the radially outer and radially inner contiguous surfaces and may extend upstream as well as downstream of the circumferential array of outlet guide vanes.
Claims
1. A fan outlet assembly comprising; a fan discharge nozzle having a radially inner platform, a radially outer platform arranged coaxially and in radial alignment with the radially inner platform and a circumferential array of outlet guide vanes spanning an annulus defined by the radially inner platform and radially outer platform and an annular duct extending downstream from the circumferential array, the annular duct having a radially outer wall contiguous with the radially outer platform and a radially inner wall contiguous with the radially inner platform, wherein, in a region extending downstream from the circumferential array the radially inner and outer platforms and/or the radially inner and outer walls have a non-axisymmetric surface bounding the annular duct.
2. A fan outlet assembly as claimed in claim 1, further comprising one or more bifurcations spanning the annular duct and spaced axially from the circumferential array of outlet guide vanes.
3. A fan outlet assembly as claimed in claim 2, wherein the non-axisymmetric surface bounding the annular duct extends at least between the circumferential array of outlet guide vanes and an axially adjacent end of the bifurcation.
4. A fan outlet assembly as claimed in claim 2, further comprising a fairing panel arranged across an axial separation between a trailing edge of the outlet guide vane and an upstream end of the bifurcation.
5. A fan outlet assembly as claimed in claim 4, wherein the fairing panel is configured and arranged to blend walls of the outlet guide vane into walls of the bifurcation.
6. A fan outlet assembly as claimed in claim 1, wherein the non-axisymmetric surfaces incorporate circumferentially extending undulations.
7. A fan outlet assembly as claimed in claim 1, wherein the non-axisymmetric surfaces incorporate axially extending undulations.
8. A fan outlet assembly as claimed in claim 6, wherein the undulations are defined by waveforms.
9. A fan outlet assembly as claimed in claim 8, wherein the waveforms are correlated to the engine order of a gas turbine engine of which the fan outlet assembly comprises a part.
10. A fan outlet assembly as claimed in claim 9, wherein the waveforms are also correlated to a mean annulus line of the annular duct.
11. A fan outlet assembly as claimed in claim 1, wherein the non-axisymmetric surfaces are defined by a series of sinusoidal shapes.
12. A fan outlet assembly as claimed in claim 1, wherein the non-axisymmetric surfaces are defined mathematically using the equations; Where: x represents an axis of the annulus; radius.sub.inner is a radius of the radially inner wall of the annular duct at a given position on axis x and azimuthal position ; radius.sub.outer is a radius of the radially outer wall of the annular duct at a given position on axis x and azimuthal position ; ND is the engine order of an engine of which the duct forms part and is an integer varying from 0 up to a maximum value n; is the azimuthal angle relative to a reference plane; f.sub.0(x) and g.sub.0(x) respectively represent mean (axisymmetric) lines at the radially inner and radially outer walls of the annular duct; fs.sub.ND(x,), fc.sub.ND(x,), gs.sub.ND(x,), gc.sub.ND(x,) are amplitude multiplying factors a.sub.ND are real numbers.
13. A fan outlet assembly as claimed in claim 12, wherein fs.sub.ND(x,), fc.sub.ND(x,), gs.sub.ND(x,), gc.sub.ND(x,) have values which fall within a range from 15% to +15% of the duct height g.sub.0(x)f.sub.0(x).
14. A fan outlet assembly as claimed in claim 1, arranged co-axially with an engine core and downstream of a fan.
15. A gas turbine engine as claimed in claim 14, wherein additional radially inner and radially outer walls extend upstream from a leading edge of the circumferential array to a trailing edge of the fan and one or both of the additional radially inner and radially outer walls have a non-axisymmetric surface.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0034] Embodiments of the disclosure will now be further described with reference to the accompanying Figures in which;
[0035] FIG. 1 shows a first fan outlet assembly of a gas turbine engine known from the prior art;
[0036] FIG. 2 shows a second fan outlet assembly of a gas turbine engine known from the prior art;
[0037] FIG. 3 shows a representative top view of the assemblies of FIGS. 1 and 2;
[0038] FIG. 4 shows a third fan outlet assembly of a gas turbine engine known from the prior art;
[0039] FIG. 5 shows a representative top view of the assembly of FIG. 4;
[0040] FIG. 6 shows a representative axial section of the arrangement of FIGS. 4 and 5;
[0041] FIG. 7 shows a representative axial section of a first embodiment of the disclosure;
[0042] FIG. 8 shows a representative axial section of a second embodiment of the disclosure;
[0043] FIG. 9 shows a representative axial section of a third embodiment of the disclosure;
[0044] FIG. 10 shows a representative axial section of a fourth embodiment of the disclosure;
[0045] FIG. 11 shows a representative side view of a fifth embodiment of the disclosure;
[0046] FIG. 12 shows a representative side view of a sixth embodiment of the disclosure;
[0047] FIG. 13 shows a representative side view of a seventh embodiment of the disclosure; and
[0048] FIG. 14 shows a representative side view of an eighth embodiment of the disclosure.
DETAILED DESCRIPTION OF DRAWINGS
[0049] As can be seen in FIG. 1, the fan outlet assembly comprises an outlet guide vane 1 which is one of a circumferential array of outlet guide vanes spanning an annulus, the array is bounded by a radially outer platform 2 and a radially inner platform 3. The radially outer platform is contiguous with a radially outer wall 4 of an engine bypass duct which extends axially downstream (with respect to the direction of flow of air through the fan) from the array. The radially inner platform is 3 is contiguous with a radially inner wall 5 of the bypass duct.
[0050] Spanning the bypass duct at a location downstream of the array is a bifurcation 6. The bifurcation may define a radially extending duct enclosing structural, mechanical, electrical and/or hydraulic operating components of the engine. The walls of the bifurcation are shaped to guide flow around such components aerodynamically. The radially inner wall 5 extends downstream to define the after body cone 7. The vane has a trailing edge 8 and there is an axial separation between the trailing edge 8 and an upstream end 9 of the bifurcation 6. The contiguous radially outer platform 2 and wall 4 together provide a substantially continuous surface.
[0051] As can be seen, the assembly of FIG. 2 is broadly similar to FIG. 1 and comprises an outlet guide vane 21 which is one of a circumferential array of outlet guide vanes spanning an annulus, the array is bounded by a radially outer platform 22 and a radially inner platform 23. The radially outer platform is contiguous with a radially outer wall 24 of an engine bypass duct which extends axially downstream (with respect to the direction of flow of air through the fan) from the array. The radially inner platform is 23 is contiguous with a radially inner wall 25 of the bypass duct.
[0052] Spanning the bypass duct at a location downstream of the array is a bifurcation 26. The bifurcation may define a radially extending duct enclosing structural, mechanical, electrical and/or hydraulic operating components of the engine. The walls of the bifurcation are shaped to guide flow around such components aerodynamically. The radially inner wall 25 extends downstream to define the after body cone 27. The vane has a trailing edge 28 and there is an axial separation between the trailing edge 28 and an upstream end 29 of the bifurcation 26. The contiguous radially outer platform 22 and wall 24 together provide a substantially continuous surface.
[0053] In contrast to FIG. 1, the trailing edge 28, upstream end 29 and a leading edge 20 of the vane are each curved rather than straight as shown in FIG. 1.
[0054] FIG. 3 shows a representative view looking down at the arrangements of FIG. 1 and FIG. 2. It will be appreciated that the curvature of the upstream end 29 and leading and trailing edges 20, 28 will not be visible in this view.
[0055] As shown in FIGS. 4 and 5 a vane 41 forming one of circumferential array of vanes 41 has a leading edge 40 and is integrally formed with a bifurcation 46. The integrally formed component extends continuously axially and radially between a radially outer wall 44 and a radially inner wall 45. Radially inner wall 45 continues to form the after body cone 47.
[0056] As can be seen in FIG. 6, in axial section, the duct bounded by radially outer wall 44 and radially inner wall 45 is axi-symmetric, that is the walls 44, 45 form two concentric circles arranged with an axis X at their centre.
[0057] As is apparent from FIGS. 1 to 6, a fan outlet assembly and more particularly a bypass duct of such an assembly can be defined in three dimensions with reference to the shown Cartesian coordinates defined by mutually orthogonal axes X, Y and Z and a cylindrical coordinate system defined by X, radius r and azimuth angle .
[0058] The three dimensional shape of the radially inner and radially outer wall surfaces can be applied to the circumferential portion or to the entire duct along a given axial extent at the inner (x inner) and the outer (x outer) as illustrated in the FIGS. 7 to 14 which show some embodiments of the disclosure. The maximum extent of x inner and x outer can go from the trailing edge of an upstream fan blade at an upstream extreme and to the exit of the bypass duct at a downstream extreme. The non-axisymmetric wall shaping may extend for any portion of this maximum extent and may be present on one or both of the radially inner and radially outer walls.
[0059] FIG. 7, FIG. 8, FIG. 9 and FIG. 10 show possible axial section results of the radially inner and outer wall profiles. The profiles have been defined applying the Equations 1 and 2 as set out above. It is to be appreciated that these figures show a given axial location and the results can be different at another axial location along the X axis. For clarity, the bifurcation and vanes are not shown in the figures (though their positions are represented in FIG. 6).
[0060] In FIGS. 7 to 10, the dotted outlines represent mean (axisymmetric) lines at the radially inner 45 and radially outer 44 walls of the duct; alternatively these could be considered to be the walls of an axisymmetric annular duct before the shaping functions have been applied to the walls. The solid lines show the walls of a duct in accordance with a fan outlet assembly of the disclosure.
[0061] In the embodiment of FIG. 7, walls 71 and 72 are shifted out of phase with each other. The result is that, at the axial location shown, the duct is wider across one side D.sub.1 than it is in a diametrically opposite position D.sub.2.
[0062] In the embodiment of FIG. 8, the inner wall 81 is distorted into an oval form having a larger dimension in the Y axis than in the Z axis. Similarly the outer wall 82 is distorted into an oval form but is around 90 out of phase with the inner wall and has a larger dimension in the Z axis than in the Y axis. Consequently, the duct is wider in the Z direction than it is in the Y direction.
[0063] In the embodiment of FIG. 9 different order functions are applied to inner wall 91 and outer wall 92. The inner wall 91 presents an eight lobed profile and the outer wall 92 a four lobed profile, each centred on the X axis.
[0064] In the embodiment of FIG. 10 different order functions are applied to inner wall 101 and outer wall 102. The inner wall 101 presents a seven lobed profile and the outer wall 102 a ten lobed profile, each centred on the X axis.
[0065] In FIG. 11, FIG. 12, FIG. 13 and FIG. 14 show possible axial section results of the radially inner and outer wall profiles. The profiles have been defined applying the Equations 1 and 2 as set out above. It is to be appreciated that these figures show a given constant location and the results may be different at another location along the circumferential direction of the represented duct.
[0066] In FIGS. 11 to 14 the dotted outlines represent mean (axisymmetric) lines at the radially inner 45 and radially outer 44 walls of the duct; alternatively these could be considered to be the walls of an axisymmetric annular duct before the shaping functions have been applied to the walls. The solid lines show the walls of a duct in accordance with a fan outlet assembly of the disclosure.
[0067] In the outlet assembly of FIG. 11, a vane 110 of a circumferential array of vanes sits upstream from a bifurcation 116. A curvature is applied to each of the inner wall 111 and outer wall 112, the curvature in each case commencing upstream of the array and extending to a downstream end of the duct. It will be noted that the waveforms which define the curvature of the walls 111 and 112 are out of phase resulting in the width of the duct varying along the X axis. The waveforms have a similar pitch.
[0068] In the outlet assembly of FIG. 12 a vane 120 of a circumferential array of vanes sits upstream from a bifurcation 136. A curvature is applied to each of the inner wall 121 and outer wall 122, the curvature in each case commencing upstream of the array of vanes and extending to a downstream end of the duct. It will be noted that the waveforms which define the curvature of the walls 121 and 122 are out of phase resulting in the width of the duct varying along the X axis. The waveform applied to the inner wall 121 has a pitch approximately twice that of the pitch of the waveform of the outer wall 122.
[0069] In the outlet assembly of FIG. 13 a vane 130 of a circumferential array of vanes sits upstream from a bifurcation 136. A curvature is applied to each of the inner wall 131 and outer wall 132, the curvature in each case commencing upstream of the circumferential array of vanes and extending to a downstream end of the duct. It will be noted that the waveforms which define the curvature of the walls 131 and 132 are out of phase resulting in the width of the duct varying along the X axis. The waveform applied to the outer wall 132 has a pitch approximately thrice that of the pitch of the waveform of the inner wall 131.
[0070] In the outlet assembly of FIG. 14 an integrated vane and bifurcation component 146 extends from a circumferential array of vanes axially along a duct defined by inner wall 141 and outer wall 142. A curvature is applied to each of the inner wall 141 and outer wall 142, the curvature in each case commencing upstream of the component 146 and extending to a downstream end of the duct. It will be noted that the waveforms which define the curvature of the walls 141 and 142 are out of phase resulting in the width of the duct varying along the X axis. The waveform applied to the outer wall 142 has a pitch approximately thrice that of the pitch of the waveform of the inner wall 141.
[0071] It will be understood that the disclosure is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the disclosure as is defined by the appended claims. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.
