Patent Application
20170089298
The application relates generally to gas turbine engines and, more particularly, to turbine exhaust cases, fan ducts, or tabs nozzle therefor.
The exhaust jet of a gas turbine engine is a significant noise source, particularly at high power conditions, which may drive the overall aircraft noise affecting communities surrounding airport and the cabin noise. Chevrons located at the trailing edge of nozzles have emerged as an effective means of reduction of jet noise for mid-to-high bypass ratio turbo-fan engines. The chevrons are typically shaped as saw-tooth patterns on the trailing edges of jet engine nozzles. The chevron nozzles induce additional mixing mechanisms altering the shear layer thereby promoting a rapid plume decay and resulting in noise reduction. This may however be accompanied by an increased drag which results in a deterioration of the performance of the gas turbine engine.
In one aspect, there is provided a deployment mechanism for inflatable surface-increasing features a gas turbine exhaust case comprising: a plurality of inflatable surface-increasing features adapted to be circumferentially distributed within the gas turbine exhaust case at a trailing edge thereof, the inflatable surface-increasing features being inflatable from a stowed configuration in which the inflatable surface-increasing features are substantially concealed fore of the trailing edge, to a deployed configuration in which the inflatable surface-increasing features extend beyond the trailing edge; and a pressurizing system in fluid communication with the plurality of chevrons to inflate and deflate the inflatable surface-increasing features.
In a second aspect, there is provided a gas turbine engine comprising: a turbine case defining an annular cavity; a plurality of inflatable surface-increasing features circumferentially distributed within the annular cavity at a trailing edge thereof, the inflatable surface-increasing features being inflatable from a stowed configuration in which the inflatable surface-increasing features are substantially concealed within the turbine case, to a deployed configuration in which the inflatable surface-increasing features extend outside the turbine case at the trailing edge, and a pressurizing system in fluid communication with the plurality of inflatable surface-increasing features to inflate and deflate the inflatable surface-increasing features between the stowed configuration and the deployed configuration.
In a third aspect, there is provided a method for deploying chevrons at a trailing edge of a gas turbine exhaust case of an aircraft, comprising: directing pressurized fluid to a plurality of inflatable surface-increasing features at the trailing edge of the exhaust case; and inflating the plurality of inflatable surface-increasing features to a deployed configuration in which the inflatable surface-increasing features are inflated to extend beyond the trailing edge of the exhaust case.
Further details of these and other aspects of the present invention will be apparent from the detailed description and figures included below.
Reference is now made to the accompanying figures, in which:
Referring to
A chevron deployment mechanism is generally shown at 30, and is mostly concealed in the inner cavity 22. The mechanism 30 has chevrons 31 that may be inflated to a deployed configuration, as shown concurrently by
The chevrons 31 are inflatable members made using inflatable metals, such as inflatable steel, aluminum and/or copper based alloys that have the property of expanding (increasing in volume and showing an increased surface) when subjected to an inner pressure, and contract to an original shape upon pressure release, for instance by the presence of a plurality of folds enabling expansion and contraction. According to another embodiment non-metal chevrons 31 (e.g. rubber), provided such materials can sustain temperatures and pressures at tail ends of gas turbine engines. The expression “chevron” is used as inflatable members described below perform the same function as the sawtooth pattern chevrons integral with the outer skin of gas turbine engine cases. However, other expressions may be used to qualify such chevrons, such as silencers, flaps, tabs, sound-suppressing means, etc, all of which are encompassed by the present disclosure. The chevrons 31 may also include air-through chevrons, also known as hollow tabs. For simplicity, the expression chevron is used throughout the specification, but encompasses these other types of devices as well, and the expression “inflatable surface-increasing features” is used in the claims to cover the multiple possible embodiments described above.
The chevrons 31 may have any appropriate shape, although a trapezoidal or truncated triangular shape may be considered for noise reduction effectiveness such that the chevrons 31 flare beyond the trailing edge of the case to create increased singularities within the flow causing an enhancement of stream-wise vortices which may result in sharper plume decay and hence a noise reduction. The number of chevrons 31 may vary in number, in size and/or in disposition. Moreover, the chevrons need not all have the same shape and size.
The chevron deployment mechanism 30 also has pressurizing line or duct 32 that can convey a hydraulic fluid or pneumatic pressure, so as to fill up the inflatable chevrons 31 to transition from the stowed configuration of
Hydraulic pressurization can be achieved through existing sources of hydraulic pressure on an engine, e.g. the actuation lines for the thrust-reversers can be modified appropriately for inflating the chevrons 31, with the pressurizing line 32 being pipe(s), conduit(s) to control the flow of fluid to the chevrons 31. Similarly, results can be achieved by using existing sources of hydraulic pressure on an aircraft, or using a separate stand-alone source (e.g., pump, reservoir, conduits, valves, etc). Similarly, pneumatic actuation can be achieved by using high pressure air available from the engine, for instance via a pressurizing duct feeding the pressurizing line 32, and/or a stand-alone source located on the engine or aircraft.
The chevron deployment mechanism 30 further comprises a depressurization portion controllable by valve 33 to release the pressure and thus cause a contraction of the chevrons 31 to the stowed configuration of
The inflatable chevrons 31 lie between the outer skin 20 and inner skin 21. The chevrons 31 may be anchored to the surfaces of inner cavity 22, based on their contracted shape, to ensure that the chevrons 31 are concealed in the inner cavity 22 (i.e., they are substantially fore of the trailing edge 20A of the case) when contracted to the stowed configuration, so as not to hinder the flow around the outer and inner skins 20 and 21.
The inflatable chevrons 31 may be connected to an end frame 40 in different ways, which may include radially positioned in radial or axial directions or a combination thereof, as illustrated in
In another embodiment, shown in
In another embodiment, the inflatable chevrons 31 may be rigidly mounted on slave sub-structures within the end frame 40 such that chevrons 31 undergo a translational movement to reach the trailing edge of the end frame 40 before being inflated to a deployed configuration.
In another embodiment, the end frame 40 may feature separate constructional details along different circumferential sectors, to allow for installation of the inflatable chevrons only along a specific sector of the end frame 40.
When the skins 20 and 21 are part of a thrust reverser, the pressurizing line 32 may have flexible portions at a pivoting location of the thrust reverser, so as not to hamper the pivoting movement, yet remain connected to a pressure source upstream of the thrust reverser. The line 32 used for conveying the fluid for pressurizing and depressurizing the inflatable chevrons 31 may be constituted of completely flexible lines or a combination of rigid and flexible pipelines packaged between the outer skin 20 and the inner skin 21 of the thrust reverser.
Referring to
In the deployed configuration, the pressurizing line 32 conveys the hydraulic/pneumatic pressure to the chevrons 31, inflating them past the trailing edges of skins 20 and 21. As observed from
The chevron deployment mechanism 30 may be designed to operate in a ‘FAIL-CLOSE’ mode wherein the inflatable chevrons 31 continuously stay in the stowed configuration, so as to minimize the hydraulic/pneumatic load under the failure condition.
Therefore, a method for deploying the chevrons 31 at a trailing edge 20A of the case comprises directing pressurized fluid to the plurality of chevrons 31 at the of the case, and inflating the plurality of chevrons 31 to a deployed configuration in which the chevrons 31 extend beyond the trailing edge 20A of the gas turbine engine. The chevrons 31 are then deflated to a stowed configuration in which the chevrons 31 are substantially fore of the trailing edge 20A of the case. The inflating of the chevrons 31 may occur when the aircraft is in at least one of a take-off and landing maneuver, and may comprise inflating the chevrons to flare away from the trailing edge. Fluid may be directed from a hydraulic source of the aircraft to the chevrons, or may be directed in a duct 32 formed between the inner skin 21 and the outer skin 20 of the aircraft to the chevrons 31. The portion of the case enclosing the chevrons 31 may be deployed in a thrust reverser configuration when the chevrons 31 are in their stowed configuration.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
