Aeronautics and astronautics – Aircraft power plants
Patent
1994-03-23
1997-02-18
Barefoot, Galen L.
Aeronautics and astronautics
Aircraft power plants
244110B, 23926531, 415119, 602261, B64C 702
Patent
active
056034717
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a ducted fan turbine engine by which is meant a gas turbine engine in which a portion of the net energy is used to drive a ducted fan. The invention is particularly concerned with the outer discharge nozzle of a ducted fan turbine engine.
In the operation of a ducted fan turbine engine air enters the engine core where it is ignited to rotate a turbine at the rear region of the engine. Rotation of the turbine rotates a fan in the forward region of the engine thereby directing by-pass air to flow rearwardly over the outside of the engine core. The main air stream in the engine core leaves the engine through an inner discharge nozzle, and the by-pass air leaves the engine through an outer discharge nozzle surrounding the inner nozzle.
The outer discharge nozzle is required to withstand the operational pressure conditions, inertia, acoustic fatigue, and creep or other temperature/strength/time-related forms of degradation. The outer discharge nozzle is also required to be constructed to facilitate engine removal.
In order to meet the above-mentioned operational requirements, conventional outer discharge nozzles have been constructed of heat-resistant, high strength/stiffness materials such as titanium, steel and Inconels, and these outer nozzles have either been permanently attached to the engine turbine case, or supported off the aft end of the by-pass duct fixed structure.
The above-mentioned materials are considerably more expensive than, for example, aluminium alloys both to obtain and to work. In addition these materials are relatively heavy which means that outer discharge nozzles constructed of these materials are correspondingly heavy and require suitably robust mounting supports.
In a conventional ducted fan turbine engine the outer nozzle is supported on the inner or primary nozzle by several struts or vanes extending between the two nozzles. Because of the considerable differences in operational temperature between the inner and outer nozzles, and also because of the internal burst pressure effects, the supporting vanes or struts are subjected to high stresses which cause deformation of both the nozzles. These stresses and deformations have to be allowed for in the design of the engine.
It is an aim of the invention to alleviate the above-mentioned disadvantages, and according to the invention there is provided a ducted fan turbine engine nozzle assembly comprising an inner assembly including an inner discharge nozzle, and an outer assembly having a nacelle and an outer discharge nozzle surrounding the inner discharge nozzle, characterised by mounting means whereby the outer discharge nozzle is detachably mounted on the nacelle for transmission of flight loads through the nacelle.
The outer discharge nozzle may be detachably mounted on the nacelle by a plurality of load transmitting connectors. These connectors may comprise spigots and blades on the nacelle which are adopted to be retained by locators on the outer discharge nozzle.
The outer discharge nozzle may be made of any suitable lightweight material such as for example a material formed predominantly of aluminium alloys.
Two examples of suitable aluminum alloys have the following specifications:
1) DTD 5070 produced by the Royal Aircraft Establishment, Farnborough
2) 2219 which is a US specification produced in the USA by the Aluminium Association Inc.
One embodiment of the invention will now be described by way of example with reference to the accompanying illustrative drawings in which:
FIG. 1A is a perspective view of a ducted fan turbine engine mounted on an aircraft wing.
FIG. 1B is a perspective view of the engine of FIG. 1A with the by-pass air ducts in their open position.
FIG. 2A is a perspective view of the inner and outer discharge nozzles of a fan jet engine.
FIG. 2B is a diagrammatic sectional view of a forward part of FIG. 2A.
FIG. 2C is a side sectional view of FIG. 2B.
FIG. 2D is a diagrammatic view illustrating the mounting of the outer discharge nozzle of FIG. 2A.
FIG. 3 is a sectional view o
REFERENCES:
patent: 3824784 (1979-07-01), Kitson et al.
patent: 4772033 (1988-09-01), Nash
patent: 5136839 (1992-08-01), Armstrong
patent: 5157915 (1992-10-01), Bart
Barefoot Galen L.
Short Brothers PLC
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