This application is based upon and claims the benefit of priority from British Patent Application No. GB 1708050.8, filed on 19 Mar. 2017, the entire contents of which are hereby incorporated by reference.
The present disclosure concerns a stator arrangement. In particular, the present disclosure concerns a stator arrangement for use in a gas turbine engine.
During operation of a gas turbine engine, it is common for an amount of noise to be produced. Noise may be produced in several areas of a gas turbine engine including, for example, one or more of the fan, compressor, combustor, and turbine sections. In particular, the compressor system may comprise a low pressure (LP) system. The LP system may comprise a rotor and a number of vanes, known singularly as an outlet guide vane (OGV) or collectively as outlet guide vanes (OGVs). OGVs are commonly located at an outlet of the fan and within a bypass duct. In this way, the OGVs can direct air travelling within the bypass duct in a required direction of airflow.
Noise generated within the LP system can be broadly divided in two parts: tone noise and broadband noise. Gas turbine engines are commonly affected by tone noise and broadband noise. Tone noise is a steady and deterministic phenomenon that strongly depends on the ratio between the number of fan blades and the number of OGVs.
Conversely, broadband noise has an unsteady and chaotic character, mainly caused by the turbulent wakes shredded at the rotor trailing edges impinging on the leading edges of the OGVs. Because of their characters, tone noise is a phenomenon that is concentrated at specific frequencies, namely the blade passing frequency and its harmonics. Broadband noise expresses itself as a “carpet” of noise affecting all frequencies.
Due to the need to reduce the noise created during operation of a gas turbine engine, it would be advantageous to provide an attenuation solution that aids in for the reduction of broadband noise. In particular, it would be advantageous to provide an attenuation solution that aids in the reduction of both tonal noise and broadband noise created during operation of a gas turbine engine.
According to a first aspect there is provided A stator arrangement for use in a gas turbine engine, the arrangement comprising an inner outlet guide wall having a central axis, the inner outlet guide wall comprising a first aerofoil extending radially relative to the central axis; the an inner outlet guide wall further comprising a second aerofoil extending radially relative to the central axis, the second aerofoil being relatively displaceable between a first position and a second position; the first aerofoil combining with the second aerofoil to form a combined aerofoil when the second aerofoil is in the first position, and separating to form two or more aerofoils when the second aerofoil is relatively displaced, in use, from the first position towards the second position; wherein one or more of a profile, shape or configuration of the second aerofoil, when in the second position, are substantially identical to that of the first aerofoil.
Advantageously, the stator arrangement allows for the OGV to fan blade ratio to be manipulated depending on the operating condition during flight or according to operating conditions. This allows a reduction of both tonal and broadband noise using a single stator arrangement. The arrangement also negates the requirement for designers to compromise in optimising the OGV for one of tonal or broadband noise. Thus, designers are able to optimise a system with more OGVs for reduced tonal noise, and a system with fewer OGVs for reduced broadband noise. In this way, the arrangement provides the possibility for splitting the OGVs into two equal vanes, so increasing the number of vanes. The inner outlet guide wall and the sliding ring may be either or both of axially displaceable and relatively rotatable between a first position and a second position. This allows the arrangement to cut-off more tones. Additionally or alternatively, the arrangement provides the possibility for combining two OGVs into a single OGV to reduce the number of distinct vanes. This allows the arrangement to reduce the number of wake-leading edges interactions.
It will be appreciated that the arrangement may comprise one or more such sliding rings. Each sliding ring may be coaxially configured around the inner outlet guide wall. Each sliding ring may comprise a second aerofoil extending radially relative to the central axis. Each sliding ring may be relatively displaceable between a first position and a second position. Each sliding ring may be either or both of axially displaceable and relatively rotatable between a first position and a second position. Each sliding ring may be connected to a second aerofoil. Each sliding ring may be connected to a portion of a second aerofoil.
A pressure profile of the second aerofoil, when in the second position, may be substantially identical to that of the first aerofoil. Thus, the arrangement may be optimised for either or both of tone noise levels by providing a relatively higher number of aerofoils generating a substantially equivalent frequency or tone; and broadband noise levels by providing a relatively lower number of aerofoils. Thus, the arrangement provides a first configuration in a first position configured for broadband noise control, and a second configuration in a second position configured for tonal noise control. Thus, in the first position, the arrangement comprises a lower number of OGVs relative to the number of fan blades, which reduces the number of wake-leading edge interactions. In the second position, the arrangement comprises a higher number of OGVs relative to the number of fan blades, which cuts the first tone at the blade passing frequency, which in turn, is related to the rotational speed of the fan.
In some examples, when configured in the second position, the first aerofoil and the second aerofoil may comprise substantially identical aerodynamic profiles. In further examples, when configured in the second position, one or more of the profile, shape or configuration of the second aerofoil, may be substantially identical to that of the first aerofoil, or vice versa. In yet further examples, when configured in the second position, the pressure profile of the second aerofoil may be substantially identical to that of the first aerofoil. The pressure profile may be visualised using computational fluid dynamics (CFD) or any such further model or tool for assessing aerodynamic performance. When configured in the second position, a substantially identical pressure profile may be achieved by the first aerofoil and the second aerofoil comprising one or more of a substantially identical angle of attack, thickness, chord line length, chord line profile, camber line length, or camber line profile. In further examples, when configured in the second position, a substantially identical pressure profile may be achieved by the first aerofoil and the second aerofoil comprising a substantially identical cross-sectional shape or profile. Thus, in yet further examples, when configured in the second position, the cross-sectional profile of the second aerofoil may be substantially identical to that of the first aerofoil. When configured in the second position, the second aerofoil may be substantially identical in size to the first aerofoil. In further examples, when configured in the second position, the second aerofoil may be a different size to the first aerofoil.
The arrangement may comprise an outer outlet guide wall configured around and radially displaced from the inner outlet guide wall. The inner guide wall may be annular. The inner guide wall may be annularly arranged around the axis. The outer guide wall may be annular. The outer guide wall may be annularly arranged around the axis. The inner guide wall and the outer guide wall may be coaxial.
Either or both of the first and second aerofoil may extend between the inner outlet guide wall and the outer outlet guide wall. The first aerofoil may comprise a pressure surface. The first aerofoil may comprise a suction surface. The first aerofoil may comprise one or more pressure neutral surfaces. The second aerofoil may comprise a pressure surface. The second aerofoil may comprise a suction surface. The second aerofoil may comprise one or more pressure neutral surfaces. The first aerofoil may be attached to either or both of the inner outlet guide wall and the outer outlet guide wall. The second aerofoil may be attached to either or both of an inner sliding ring wall and an outer sliding ring wall.
Either or both of the inner outlet guide wall and outer outlet guide wall may comprise two or more segments. Each segment may comprise 1 or more first aerofoils. Each segment may comprise 2 or more first aerofoils. Each segment may comprise 4 or more first aerofoils. Either or both of the inner sliding ring wall and outer sliding ring wall may be comprised of two or more segments. Each segment may comprise 1 or more second aerofoils. Each segment may comprise 2 or more second aerofoils. Each segment may comprise 4 or more second aerofoils.
The sliding ring may be slidably engaged with the inner outlet guide wall. The sliding ring may be slidably engaged with the inner outlet guide wall via an inner sliding ring wall. The sliding ring may be located in a location feature within the inner outlet guide wall. The sliding ring may be located about the inner outlet guide wall via a retaining mechanism. The inner outlet guide wall and sliding ring may together form a smooth gas flow surface. The inner outlet guide wall and sliding ring may together form a rough or textured gas flow surface.
The sliding ring may be slidably engaged with the outer outlet guide wall. The sliding ring may be slidably engaged with the outer outlet guide wall via an outer sliding ring wall. The sliding ring may be located in a location feature within the outer outlet guide wall. The sliding ring may be located about the outer outlet guide wall via a retaining mechanism. The outer outlet guide wall and sliding ring may together form a smooth gas flow surface. The outer outlet guide wall and sliding ring may together form a rough or textured gas flow surface.
The first aerofoil and the second aerofoil may be relatively displaced between the first position and the second position when the first aerofoil and the second aerofoil are relatively rotated, in use, about the central axis. The first aerofoil and the second aerofoil may be relatively rotated from the first position towards the second position through relative displacement between the sliding ring and the inner outlet guide wall.
The first aerofoil and the second aerofoil may be relatively displaced between the first position and the second position when the first aerofoil and the second aerofoil are circumferentially displaced, in use, about the central axis. The second aerofoil may be circumferentially displaced about the central axis when displaced towards the second position.
A leading edge of the first aerofoil may be axially displaced from a leading edge of the second aerofoil when displaced, in use, between the first position and the second position. The first aerofoil and the second aerofoil may axially overlap when in the first and second positions.
At least a portion of the first aerofoil may be circumferentially aligned with at least a portion of the second aerofoil when in a first position.
The first aerofoil may be circumferentially adjacent to the second aerofoil when in a first position. The first aerofoil and the second aerofoil may abut when in the first position. A portion of the suction surface of the first aerofoil may abut against a portion of the pressure surface of the second aerofoil when in the first position. A portion of the pressure surface of the first aerofoil may abut against a portion of the suction surface of the second aerofoil when in the first position.
The first aerofoil may be axially adjacent to the second aerofoil when in a first position. A portion of the trailing edge of the first aerofoil may abut against a portion of the leading edge of the second aerofoil when in the first position. A portion of leading edge of the first aerofoil may abut against a portion of the trailing edge of the second aerofoil when in the first position. A portion of the trailing edge of the first aerofoil may be axially aligned with a portion of the leading edge of the second aerofoil when in the first position. A portion of leading edge of the first aerofoil may be axially aligned with a portion of the trailing edge of the second aerofoil when in the first position. The first and second aerofoils may form a substantially smooth pressure and suction face when in the first position. The first and second aerofoils may form a substantially smooth aerofoil when in the first position.
Either or both of the first aerofoil and second aerofoil may be rotatable about an axis comprising a radial component relative to the central axis. The axis comprising a radial component may be substantially perpendicular to the central axis. The axis comprising a radial component relative to the central axis may comprise an axial component. The axis comprising a radial component may be canted from an axis perpendicular to the central axis.
The stator arrangement may be an outlet guide vane for incorporation within a gas turbine engine. The stator arrangement may be an inlet guide vane for incorporation within a gas turbine engine. The stator arrangement may be a variable vane for incorporation within a gas turbine engine.
The stator arrangement may be incorporated within an outlet guide vane stage for incorporation within a gas turbine engine. The stator arrangement may be controlled by a controller. The controller may be linked to an engine management system. Either or both of the engine management system or the controller may vary the displacement of the inner outlet guide wall relative to the sliding ring according to a process condition. Either or both of the engine management system or the controller may vary the displacement of the inner outlet guide wall relative to the sliding ring according to an engine operating condition or an environmental condition. Either or both of the engine management system or the controller may comprise a sensor for sensing an engine operating condition or an environmental condition.
According to a second aspect, there is provided a stator arrangement for use in a gas turbine engine, the arrangement comprising an inner outlet guide wall having a central axis, the inner outlet guide wall comprising a first aerofoil extending radially relative to the central axis; a sliding ring coaxially configured around the inner outlet guide wall, the sliding ring comprising a second aerofoil extending radially relative to the central axis, the inner outlet guide wall and the sliding ring being relatively displaceable between a first position and a second position; the first aerofoil combining with the second aerofoil to form a combined aerofoil when the inner outlet guide wall and the sliding ring are in the first position, and separating to form two or more aerofoils when the inner outlet guide wall and the sliding ring are relatively displaced, in use, from the first position towards the second position; wherein one or more of a profile, shape or configuration of the second aerofoil, when in the second position, are substantially identical to that of the first aerofoil.
A pressure profile of the second aerofoil, when in the second position, may be substantially identical to that of the first aerofoil.
A cross-sectional profile of the second aerofoil, when in the second position, may be substantially identical to that of the first aerofoil.
According to a third aspect, there is provided a gas turbine comprising the stator arrangement previously described. Alternatively, the stator arrangement previously described may be incorporated within a rotating machine.
The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.
Embodiments will now be described by way of example only, with reference to the Figures, in which:
With reference to
The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow 24 into the intermediate pressure compressor 14 and a second air flow 25 which passes through a bypass duct 22 to provide propulsive thrust. Within the bypass duct 22, the second air flow 25 is directed towards the rear of the gas turbine engine by one or more outlet guide vane (OGV) stages 28, each stage comprising a plurality of outlet stator vanes 29. Concurrently, the first air flow 24 is fed into the intermediate pressure compressor 14 which compresses the air flow and delivers it to the high pressure compressor 15, where further compression takes place. The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16, where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.
Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.
It is common for an amount of noise to be created by interaction of the first air flow 24 and second air flow 25 travelling through the engine with constituent components of the gas turbine engine assembly. In particular, it is common for an amount of noise to be created by the second air flow 25 interacting with one or more guide vane (GV) stages 28. To address noise levels, current gas turbine engines are designed to reduce tonal noise by tuning the number of vanes 29 of a particular GV stage 28 to rotor blades 13, according to a design rule derived from the Tyler-Sofrin rule:
(no. of OGVs)>(2*no. of rotor blades)+4
However, using this rule increases the broadband noise created by the gas turbine engine 10 due to an increased number of GVs 29 and thus turbulent wakes impinging on the leading edges of the GVs 29. This is particularly pertinent for future engine programmes where reduced rotational fan speeds and alternate fan blade designs may create a different loading and/or more powerful and energetic wake energy content. Such modifications may lead to a “rise” in the broadband noise carpet and attenuated tones in the frequency spectrum. Thus, it is recognised that in addition to tonal noise levels, the levels of broadband noise must be addressed and reduced accordingly.
In contradiction of the Tyler-Sofrin rule outlined to reduce tonal noise, the current method to reduce broadband noise is to reduce the number of wake-blade interactions by reducing the number of GVs 29. Due to contradicting methods for the reduction of respective tonal and broadband noise types, future engine programmes require a new design rule or solution for the reduction of both tonal and broadband noise.
In the example shown, the aerofoils 30 are formed as separate components which are subsequently fastened or joined together around the inner 32 and outer 33 guide walls. In this way, the OGVs 29 are annularly arranged and secured to the one or more fairings as part of a support structure (not shown) to form the OGV stage 28. In some examples, the OGV 29 can be produced as a single ring. For example, the ring could be manufactured by casting or forging to net-shape, or to near net-shape, before finishing by a suitable traditional or non-traditional machining process. The OGV 29 structure could be produced in its entirety as a single component.
In
The second OGV 129b is shown to comprise a sliding ring 142 coaxially configured around the inner outlet guide wall 132. The sliding ring 142 comprises an inner sliding ring guide wall 144. The sliding ring 142 comprises a second aerofoil 131 extending radially relative to the central axis 111. In some examples, the sliding ring 142 comprises one or more second aerofoils 131 extending radially relative to the central axis 111. In some examples, the inner outlet guide wall 132 can comprise an annular arrangement of two or more second aerofoils 131. In further examples, the sliding ring 142 is slidably engaged with a radially outer surface of the inner outlet guide wall 132. The second aerofoil 131 extends between the inner sliding ring guide wall 144 and a receiving portion in the outer outlet guide wall 133. In further examples, the second aerofoil 131 extends between the inner sliding ring guide wall 144 and an outer sliding ring guide wall (not shown). In further examples, the sliding ring 142 is slidably engaged with a radially inner surface of the outer outlet guide wall 133. In this way, the inner outlet guide wall 132 and the sliding ring 142 are relatively rotatable between a first position and a second position.
The surfaces of the inner outlet guide wall 132, outer outlet guide wall 133, first and second aerofoils 131,132 and respective sliding rings together define one or more flow passages for the first air flow 24 to flow from from a forward position towards an aft position. In some examples, the sliding ring 142 may be located in a recess within the inner outlet guide wall 132. In this way, the sliding ring 142 and inner outlet guide wall 132 may together form a combined smooth gas-washed surface over which the first air flow 24 may pass. Thus, an outer sliding ring may be located in a recess within the outer outlet guide wall 133. In this way, the outer sliding ring and outer outlet guide wall 133 may together form a combined smooth gas-washed surface over which the first air flow 24 may pass. In further examples, the sliding ring 142 may abut against the inner outlet guide wall 132. Thus, the sliding ring 142 may radially project from either or both of the inner outlet guide wall 132 and outer outlet guide wall 133 and may together form a roughened or textured gas-washed surface over which the second air flow may pass. In some examples, the arrangements described in relation to the inner annulus, including the arrangement of the inner outlet guide wall 132 and sliding ring 142, may be replicated in the arrangements for the outer annulus and sliding ring 142. Alternatively, any one or more of the described arrangements for the inner outlet guide wall 132 and sliding ring 142 may be used for the outer annulus in conjunction with the described arrangements for the inner annulus shown in
For one or more of the inner outlet guide wall 132 and the outer outlet guide wall 133, rotation of the sliding ring 142 may be provided by an internal or external structure, such as a mechanical linkage arrangement or a mechanical drive such as a motor, arranged radially inwards of the inner outlet guide wall 132 or radially outwards of the outer outlet guide wall 133. Such an arrangement may cause a rotation of the sliding ring 142 relative to both the inner outlet guide wall 132 and the outer outlet guide wall 133. Such arrangements may be similar to those currently known for use with variable inlet guide vanes (VIGVs). Such arrangements may also include one or more of a bearing race or lubrication to reduce the frictional force between the inner outlet guide wall 132 and the outer outlet guide wall 133. Such arrangements may also include a slot or shaped section in either or both of the inner outlet guide wall 132 and the outer outlet guide wall 133 for location of the sliding ring 142 therein.
To provide relative displacement between the first and second positions, the first aerofoil 130 is provided on the inner outlet guide wall 132 at a first axial location. The second aerofoil 131 is provided on the sliding ring 142 at a second axial location. The first 130 and second aerofoils 131 have an approximately equal radial displacement relative to the central axis 111. The inner outlet guide wall 132 and the sliding ring 142 are configured to be relatively rotatable about the central axis 111, allowing circumferential displacement between the inner outlet guide wall 132 and the sliding ring 142. In this way, relative displacement between the inner outlet guide wall 132 and the sliding ring 142 provides a corresponding displacement between the first OGV 129a and the second OGV 129b. Thus, in some examples, relative displacement between the first OGV 129a and the second OGV 129b provides a corresponding displacement between the first 130 and second aerofoils 131.
When the first OGV 129a and the second OGV 129b are configured in a first position, shown in
By the first 130 and second 131 aerofoils combining to form a single component 134, the number of separated aerofoils 130,131 within the OGV stage 128 when in the first position is reduced relative to the number of separated aerofoils 130,131 within the OGV stage 128 when in the second position. This reduces the wake-leading edge interactions within the second airflow 25 of the gas turbine engine 100. Thus, the combined broadband noise is reduced.
In
The entirety of either or both of the first 130 and second aerofoils 131 may be circumferentially displaced from the first position towards the second position. Alternatively, a portion of either or both of the first 130 and second 131 aerofoils may be circumferentially displaced from the first position towards the second position. Thus, one or more portions of either or both of the first 130 and second 131 aerofoils may remain static.
As shown in
Referring now to
As described in relation to
In further examples, the number of second aerofoils comprised in the second OGV 129b may exceed the number of aerofoils comprised in the first OGV 129a. Thus, in some examples, the number of separated aerofoils 130,131 within the OGV stage 128 is increased, when displaced towards the second positon, by the number of second aerofoils 131 comprised in the first OGV 129a.
As shown in
In further examples, both the first aerofoil 130 and the second aerofoil 131 may comprise a fulcrum, further to the arrangement shown in
A portion of the trailing edge 140 body of the second aerofoil 131 is configured to be received between the pressure 135b and suction 136b surfaces of the second aerofoil 131. Thus, a recess is provided between the pressure 135b and suction 136b surfaces of the second aerofoil 131 into which at least a portion of the trailing edge 140 body may retract via a slot 150b. During this action, a sliding of the fourth ring 154 relative to the third ring 153 will cause the portion of the trailing edge body 140 to be circumferentially displaced about the aft fulcrum arrangement 149 and the slot 150b. Thus, the trailing edge body 140 is caused to be radially and circumferentially displaced relative to the pressure 135b and suction 136b surfaces via the slot 150b.
Further to the leading and trailing edge bodies 139,140, a portion of the pressure 135b and suction 136b surfaces of the second aerofoil 131 are fixedly attached to the second ring 152. In this way, the leading edge 139 and trailing edge 140 bodies, other than the fore and an aft fulcrum arrangements 148,149, are radially displaced from the first 151, third 153 and fourth 154 rings to allow relative movement between the respective rings 151,152,153,154 and the second aerofoil 131. In this way, circumferential displacement of the fourth ring 154 relative to the second ring 152 and results in a displacement of at least a portion of the second aerofoil 131, relative to the portion of the pressure and suction 135b,136b surface fixedly attached to the second ring 152. Such displacement is about the slot 150b.
Referring now to
The first aerofoil 130 is fixedly attached to a single fixed ring 153 only over the axial width of the third ring 153, limiting adjustment of the camber of the aerofoil 130. The remainder parts 137,138 of the first aerofoil 130 are radially displaced from the first 151, second 152 and fourth 154 rings to allow relative movement between the rings 151, 152,154 and the first aerofoil 130.
As described in relation to
According to some examples, when configured in the second position, one or more of the profile, shape or configuration of the second aerofoil 131, are substantially identical to that of the first aerofoil 130, or vice versa. According to further examples, as shown in
Any one or more of the aerodynamic profile, profile, shape, configuration, and pressure profile may be visualised using computational fluid dynamics (CFD) or any such further model or tool for assessing aerodynamic performance. In particular, the pressure profile distribution over either or both of the first aerofoil 130 and the second aerofoil 131 may be quantified numerically by using, for example, by using simple CFD codes to calculate the pressure profile on each section of a 3D blade to take into account the twisted shape of the blade. Furthermore, the pressure profile distribution over either or both of the first aerofoil 130 and the second aerofoil 131 may be quantified empirically by using, for example, velocity field measurement techniques such as particle image velocimetry (PIV), or laser Doppler velocimetry (LDV).
When configured in the second position, a substantially identical pressure profile may be achieved by the first aerofoil 130 and the second aerofoil 131 comprising one or more of a substantially identical angle of attack, thickness, chord line length, chord line profile, camber line length or camber line profile. In further examples, when configured in the second position, a substantially identical pressure profile may be achieved by the first aerofoil 130 and the second aerofoil 131 comprising a substantially identical cross-sectional shape or profile. In some examples, as shown in
By virtue of the second aerofoil 131, when in the second position, comprising a substantially identical profile, shape or configuration to that of the first aerofoil 130, the arrangement provides the ability to apply the Tyler-Sofrin rule without any further modification. Thus, second airflow 25 flowing towards the OGV stage 128 from the fan 13 observes the same pressure profile at the first 130 and second 131 aerofoil, which reduces the potential for the formation of multiple tones. Thus, the potential for increased tonal noise is reduced. In further examples, when configured in the second position, the gap between the first aerofoil 130 and the second aerofoil 131 may be controlled in accordance with predetermined conditions, parameters or requirements. With regards to broadband noise, a single tone resulting from the second aerofoil 131, when in the second position, comprising a substantially identical profile, shape or configuration to that of the first aerofoil 130, provides a singular acoustic response resulting from the wakes impinging on the first 130 and second 131 aerofoils. Thus, second airflow 25 flowing towards the first 130 and second 131 aerofoils from the fan 13 observes the same pressure profile at the first 130 and second 131 aerofoil, which reduces the potential for the formation of multiple “broadband” signatures, and the potential for increased broadband noise as a result.
By virtue of the first aerofoil 130 and second aerofoil 131 comprising a substantially identical profile, shape or configuration when in the second position, such that the pressure profile of the second aerofoil 131 is substantially identical to that of the first aerofoil 130, the first aerofoil 130 and second aerofoil 131 are capable of exerting an equivalent straightening effect on the second airflow 25. To modify the straightening effect, one or more of the profile, shape or configuration of either or both of the first aerofoil 130 and second aerofoil 131 may be altered as required, as shown in
As previously described in relation to
As shown in
The first aerofoil 130 comprises a leading edge 137 and a trailing edge 138, a suction 136a surface and a pressure surface 135a. The first aerofoil 130 is shown to be attached to the inner outlet guide wall 132. At least a portion of the first aerofoil 130 is shown to extend axially from the inner outlet guide wall 132 to a location aft of the inner outlet guide wall 132. When in the first position, a portion of the trailing edge 138 of the first aerofoil 130 extends axially over a portion of the sliding ring 142. Thus, the portion of the first aerofoil 130 which extends axially from the inner outlet guide wall 132 is radially displaced from the sliding ring 142 to allow relative movement of the first aerofoil 130 and the sliding ring 142.
The second aerofoil 131 comprises a leading edge 139 and a trailing edge 140, a suction surface 136b and a pressure surface 135b. The second aerofoil 131 is shown to be attached to the sliding ring 142. At least a portion of the second aerofoil 131 is shown to extend axially from the sliding ring 142 to a location forward of the sliding ring 142. When in the first position, a portion of the leading edge 139 of the second aerofoil 131 extends axially over a portion of the inner outlet guide wall 132. Thus, the portion of the second aerofoil 131 which extends axially from the sliding ring 142 is radially displaced from the inner outlet guide wall 132 to allow relative movement of the second aerofoil 131 and the inner outlet guide wall 132.
In accordance with the described arrangement, the portion of the inner outlet guide wall 132 comprising the first aerofoil 130 is shown to be forward of the sliding ring 142. In some examples, the portion of the inner outlet guide wall 132 comprising the first aerofoil 130 may be to be forward of the sliding ring 142, with corresponding changes in the design and mating geometry of the first 130 and second aerofoils 131 as required. In either case, the first 130 and second aerofoils 131 are axially displaced relative to one another in both a first and a second position. Thus, when the first OGV 129a and the second OGV 129b are configured in a first position, shown in
In some examples, the component, when the first 130 and second aerofoils 131 are in the first position, comprises a substantially smooth aerofoil-like profile. By the first 130 and second aerofoils 131 combining to form a single component 134, the number of separated aerofoils 130,131 when in the first position is reduced relative to the number of separated aerofoils 130,131 within the OGV stage 128 when in the second position.
As shown in
When the first OGV 129a and the second OGV 129b are configured in a second position, shown in
In
Thus, in accordance with the examples shown in
In some examples, the arrangement shown in
In addition to the Figures shown, in further examples, the aerofoils may be provided in one or more segments. Each segment may comprise one or more aerofoils 130,131. Each segment may alternatively include two or more aerofoils 130,131. Such segments may be provided at one or more positions of the annular arrangement of the OGV stage 128. Thus, only a portion of the OGV stage 128 may comprise the described stator arrangement. Alternatively, two or more segments may be provided at two or more positions of the annular arrangement of the OGV stage 128. The segments may be equally spaced. The segments may be disparately spaced.
In further examples, the leading edge 137,139 of either or both of the first 130 and second aerofoils 131 may comprise a leading edge feature to re-energize the boundary layer and instigate a reattachment of the boundary layer on the respective aerofoil. The feature may comprise a slot or a slat. The feature may induce a disturbance in the flow over the leading edge 137,139 of either or both of the first 130 and second aerofoils 131.
In some examples, one or more of the first aerofoil 130, second aerofoil 131, inner outlet guide wall 132, outer outlet guide wall 133, and rings 142,151,152,153,154, according to
Such metallic materials may comprise nickel. Such metallic materials may comprise a nickel alloy. Such metallic materials may comprise a nickel-based super alloy. Such metallic materials may comprise an aluminium alloy. Such metallic materials may comprise a steel or an iron-based alloy.
In addition to the described structures or arrangements for rotating of one or more of the sliding rings 142,151,152,153,154, according to
Additionally or alternatively, the trailing edge 138,140 of either or both of the first 130 and second aerofoils 131 may comprise a feature to modify the loading characteristics of the respective aerofoils and enhance their aerodynamic performance. The feature may comprise a flap or a protrusion. The trailing edge feature may change the loading of the respective aerofoils and enhance their aerodynamic performance.
It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. 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.
Number | Date | Country | Kind |
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1708050.8 | May 2017 | GB | national |