Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Patent
1996-05-24
1999-08-24
Thorpe, Timothy S.
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
602261, 244 54, B64D 2908
Patent
active
059410612
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to propulsive power units for aircraft and is particularly although not exclusively concerned with a power unit comprising a ducted fan turbine (turbofan) engine and a nacelle which houses the engine.
The function of the nacelle for a turbofan engine is generally twofold. Firstly, the nacelle must provide an air intake flow to the fan of minimal disturbance for a variety of flight conditions which include high incidence, gusts and the like. Secondly, the exterior profile of the nacelle should be such as to minimise aerodynamic drag, subject to constraints imposed by major engine components such as the accessories gearbox.
Considering the exterior profile, the skin friction component of the overall profile drag is directly affected by the discontinuities on the outer surface. While the ideal would be for a smooth, uninterrupted outer surface, this ideal is compromised in nacelles hitherto proposed by the various breaks in the outer skin which arise due to the doors and panels which are required to gain access to the equipment housed within.
A typical conventional nacelle is shown in FIG. 1 of the drawings, which is a schematic perspective view of an underwing pylon mounted turbofan power unit. The main structural components of the nacelle are the inlet cowl 11, the fan cowl doors 12, the thrust reverser unit 13 and the nozzle 14. The inlet cowl 11 is a single unit, comprising a leading edge lipskin structure 15, an outer main skin 16, an air intake acoustic barrel 17 which serves to attenuate engine noise, and various internal stiffening members and bulkheads. The inlet cowl 11 generally attaches, via a flange at the rear of the acoustic barrel 17, to a front flange of the engine fan case. The fan cowl doors 12 are generally hinged at the pylon 18, and are latched together at the bottom centre line. The thrust reverser unit 13 may take a variety of forms but is typically mounted from the engine casing. The nozzle 14 may be attached in a variety of ways depending upon the exhaust philosophy adopted, i.e., mixed or separate fan stream exhaust and core exhaust. The forms which the thrust reverser and nozzle take only marginally affect the benefits derived from a propulsive power unit according to the present invention and as hereinafter to be described, as will become apparent.
Various inspection doors and removable panels (not shown) are provided in the exterior skin 16 of the inlet cowl 11 of the nacelle shown in FIG. 1 in order to gain access to equipment housed within the cowl 11. The presence of joints occurring between the main exterior inlet cowl skin and such inspection doors and removable panels reduces the aerodynamic efficiency of the exterior surface of the nacelle.
According to the present invention, there is provided an aircraft propulsive power unit comprising an engine, a nacelle structure which houses the engine and which includes a displaceable nacelle portion which forms a forward part of the nacelle structure and which takes up an operational position in which a forward end thereof forms part of an intake opening leading to an intake barrel located upstream of the engine for the supply of intake air to the engine, wherein the intake barrel is secured to a forward component of the engine, wherein the displaceable nacelle portion includes a leading edge profile formed by a lipskin structure at the forward end thereof which has rearwardly extending outer and inner lipskin edge portions, wherein the displaceable nacelle portion further includes an outer main skin which extends rearwardly from the outer lipskin edge portion, wherein the inner lipskin edge portion in the operational position of the displaceable nacelle portion adjoins the forward end of the intake barrel and wherein the power unit includes support means to support the displaceable portion while permitting it to be moved radially outwardly on the support means from its operational position to a displaced position in which it is supported by the support means and in which it is spaced radially outwardl
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patent: 4043522 (1977-08-01), Vetter
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patent: 5603471 (1997-02-01), Armstrong
patent: 5609313 (1997-03-01), Cole et al.
Johnson Kenneth Henry
Sherry Philip David
Welsh Robert
Kim Ted
Short Brothers PLC
Thorpe Timothy S.
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