Aeronautics and astronautics – Retarding and restraining devices – Friction brakes
Reexamination Certificate
2001-10-09
2003-12-16
Poon, Peter M (Department: 3643)
Aeronautics and astronautics
Retarding and restraining devices
Friction brakes
C060S226200
Reexamination Certificate
active
06663042
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to aircraft propulsive power units and is particularly concerned with an aircraft propulsive power unit comprising an efflux duct in which gaseous fluid is conducted in a predetermined first flow path for discharge from an exit end of the duct in the production of forward thrust, and a thrust reversing arrangement which in an operative disposition redirects gaseous fluid flowing in the first flow path into a second flow path to produce reverse thrust.
Prior GB 2314818A discloses a thrust reversing arrangement having a flow redirecting structure which includes a redirecting downstream wall against which fluid flow in the first flow path impinges to turn the flow into the second flow path and an upstream wall round which the fluid flow turns and which is so formed as to generate vortices which prevent or delay separation of the boundary layer from the boundary surface.
The propulsive power unit disclosed in GB2314818A is a turbofan power unit which includes a nacelle having a cowl structure to support ambient flow thereover and which in the operative disposition of the redirecting structure occupies a position in which it presents a cowl opening in the cowl structure to allow flow in the second flow path. A cascade assembly extends rearwardly across the cowl opening from a forward end on which it is cantilevered and is so mounted as to extend across the second flow path. It is received within a cavity formed in the redirecting structure when the latter is moved to its inoperative disposition.
SUMMARY OF THE INVENTION
When the redirecting structure is moved into its operative disposition in the reversing arrangement disclosed in GB2314818A, the radially outer edge of the downstream wall takes up a position adjacent the rearward end of the cascade assembly to redirect fluid flow directly into and through the cascade assembly.
In the reversing arrangement disclosed in GB2314818A means are provided on the upstream wall to improve the effectiveness of the upstream wall, thus promoting improved flow turning. Although the proposals put forward in regard to the upstream wall can be regarded as an improvement, the relative dispositions of the cascade assembly and the configuration of the downstream wall are not regarded as satisfactory for producing optimum reverse flow conditions.
It is an object of the present invention to provide a flow redirecting structure having one or more features taken individually or in combination which lead to an improved structure and improved reverse flow characteristics.
According to a first aspect of the present invention there is provided an aircraft propulsive power unit comprising an efflux duct in which gaseous fluid is conducted in a predetermined first flow path for discharge from an exit end of the duct in the production of forward thrust, and a thrust reversing arrangement which in an operative disposition redirects gaseous fluid flowing in the first flow path into a second flow path to produce reverse thrust, wherein the reversing arrangement has a flow redirecting structure which is displaceable between an operative disposition and an inoperative disposition and which comprises a flow redirecting zone which intercepts fluid flow in the first flow path and redirects it into the second flow path when the redirecting structure moves to the operative disposition, characterised in that the flow redirecting zone includes a cavity which so forms part of the flow redirecting zone and is so dimensioned as to generate a back pressure which supports redirection of flow.
In an embodiment of the invention according to its first aspect and as hereinafter to be described the flow redirecting zone includes a redirecting wall portion which supports redirection of flow. The redirecting wall portion is so dimensioned and configured as to provide optimisation of back pressure generated by the cavity for predetermined efflux duct flow conditions.
In embodiments of the invention according to its first aspect and as hereinafter to be described the propulsive power unit is a turbofan power unit including a fan duct and the efflux duct is the fan duct of the turbofan unit. The turbofan unit includes a nacelle having a cowl structure to support ambient flow thereover and the flow redirecting structure includes a cowl portion which in the inoperative disposition of the redirecting structure forms part of the cowl structure and supports ambient flow thereover and in the operative disposition of the redirecting structure occupies a position in which it presents a cowl opening in the cowl structure to allow flow in the second flow path.
In an embodiment of the invention according to its first aspect and as hereinafter to be described the thrust reversing arrangement includes a cascade assembly which is so mounted as to extend across the second flow path and which is received within the cavity formed in the flow redirecting zone when the redirecting structure is moved from its operative disposition to its inoperative disposition. The redirecting structure in the inoperative disposition takes up a forward disposition with a leading edge of the cowl portion abutting a trailing edge of an adjacent cowl portion and in the operative disposition takes up a rearward disposition with the leading edge of the cowl portion spaced from the trailing edge of the adjacent cowl portion to provide the cowl opening. The cascade assembly extends rearwardly across the cowl opening from a forward end from which it is cantilevered and terminates at a rearward end at a position in which it is forwardly spaced from the leading edge of the cowl portion when the redirecting structure is in the operative disposition thereby to provide in the second flow path a flow control slot between the rearward end of the cascade assembly and the leading edge of the cowl portion, with the control slot being so dimensioned as to optimise reverse thrust for predetermined fan duct flow conditions.
According to a second aspect of the present invention there is provided an aircraft propulsive power unit comprising an efflux duct in which gaseous fluid is conducted in a predetermined first flow path for discharge from an exit end of the duct in the production of forward thrust, and a thrust reversing arrangement which in an operative disposition redirects gaseous fluid flowing in the first flow path into a second flow path to produce reverse thrust, wherein the reversing arrangement has a flow redirecting structure which is displaceable between an operative disposition and an inoperative disposition and which comprises a flow redirecting zone which intercepts fluid flow in the first flow path and redirects it into the second flow path when the redirecting structure moves to the operative disposition, wherein the propulsive power unit is a turbofan power unit including a fan duct, wherein the efflux duct is the fan duct of the turbofan unit, wherein the turbofan unit includes a nacelle having a cowl structure to support ambient flow thereover, wherein the flow redirecting structure includes a cowl portion which in the inoperative disposition of the redirecting structure forms part of the cowl structure to support ambient flow and in the operative disposition of the redirecting structure occupies a position in which it presents a cowl opening in the cowl structure to allow flow in the second flow path, wherein the redirecting structure in the inoperative disposition takes up a forward disposition with a leading edge of the cowl portion abutting a trailing edge of an adjacent cowl portion and in the operative disposition takes up a rearward disposition with the leading edge of the cowl portion spaced from the trailing edge of the adjacent cowl portion to provide the cowl opening, and wherein a cascade assembly extends rearwardly across the cowl opening from a forward end from which it is cantilevered and the cascade assembly terminates at a rearward end at a position in which it is forwardly spaced from the leading edge of the cowl portion when the redirecting struc
Beattie William Edwin
Bennett Joel David
Campbell Hugh Keith
Hatrick Michael John
McEvoy Finbarr
Collins Timothy D
Fulbright & Jaworski L.L.P.
Poon Peter M
Short Brothers PLC
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