Aircraft power plant with two air intake fans

Aeronautics and astronautics – Aircraft power plants

Reexamination Certificate

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Details

C060S262000, C060S262000

Reexamination Certificate

active

06260800

ABSTRACT:

SUMMARY OF THE INVENTION
According to the present invention there is provided a power plant comprising a core engine having an axis and an air inlet located on the axis, fan means for supplying air to the air inlet of the engine, and nozzle means for selectively directing a proportion of the air from the fan means either axially of the engine or transversely of the axis in front of the engine, wherein the fan means comprises a first fan for supplying air to the nozzle means, and a second fan, positioned rearwardly of the first fan, for supplying air to the air inlet of the engine.
The invention also provides an aircraft power plant for vertical take-off and landing comprising a jet propulsion unit having an air inlet and an exhaust outlet and incorporating a combustion chamber, compressor means for supplying air from the air inlet to the combustion chamber, a fuel inlet for supplying fuel to the combustion chamber, and turbine means coupled to drive the compressor means and arranged to be driven by the exhaust gases passing from the combustion chamber to the exhaust outlet, fan means for supplying air, and front and rear nozzle means for selectively directing a proportion of the air from the fan means downwardly in front of the propulsion unit and for selectively directing at least a proportion of the exhaust gases from the exhaust outlet downwardly to the rear of the propulsion unit to effect lift on take-off or landing, wherein the fan means comprises a first fan for supplying air to the front nozzle means, and a second fan, positioned rearwardly of the first fan, for supplying air to the air inlet of the propulsion unit.
If it is assumed that 40% of the fan air is ingested by the high pressure compressor of the propulsion unit in the current Pegasus power plant, the front nozzles must therefore pass 60% of the fan air. Accordingly, by analogy, in use of the dual fan arrangement of the present invention, the first fan, which is provided for supplying air to the front nozzles, need pass only 60% of the air flow of the single fan of the Pegasus power plant, with the result that the first fan need have only 60% of the cross-sectional area of the fan used in the Pegasus power plant. Furthermore the first fan may be driven directly by a relatively small diameter shaft coupled to the hub of the second fan without requiring a gearbox, and with the length of the shaft being chosen to position the front nozzles sufficiently far forward to produce the moment required about the centre of gravity of the aircraft. Also the front nozzles can be located substantially further inwardly in relation to the centre line of the aircraft as compared with the Pegasus arrangement. The smaller tip diameter of the first fan, as compared with the fan of the Pegasus arrangement, additionally gives scope for higher rotational speeds and potentially reduced weight.
The first and second fans may be disposed coaxially with respect to the propulsion unit, and may be arranged to be driven by the turbine means. For example the first and second fans may be driven by a common drive shaft which is rotatable by the turbine means. Alternatively the first and second fans may be driven by separate coaxial shafts which are rotatable by the turbine means.
However the first fan may alternatively be axially offset from the propulsion unit, and may be arranged to be driven by the turbine means by means of a drive shaft extending externally of the propulsion unit.
Furthermore it is preferred that the front nozzle means is adjustable between a lift position in which the air is directed downwardly by the front nozzle means and a cruise position in which the air is directed substantially horizontally by the front nozzle means. The rear nozzle means may also be adjustable between a lift position in which the exhaust gases are directed downwardly and a cruise position in which the exhaust gases are directed substantially horizontally.
In one embodiment of the invention there is provided, upstream of the front nozzle means, diverter valve means adjustable, in the cruise position of the front nozzle means, between a stooge cruising position in which the air from the first fan is directed to the front nozzle means and a high thrust position in which the air from the first fan is directed to boost the supply of air to the air inlet of the propulsion unit. Preferably the diverter valve means is arranged to direct the air from the first fan towards the second fan in the high thrust position.
In an alternative embodiment of the invention there is provided, downstream of the front nozzle means, diverter duct means with which the front nozzle means is communicable in the cruise position so that the air from the first fan is directed by the diverter duct means to boost the supply of air to the air inlet of the propulsion unit. Preferably the diverter duct means is arranged to direct the air from the first fan towards the second fan when the front nozzle means is in the cruise position.
In a further development the diverter duct means is adjustable between a stooge cruising position in which the air from the front nozzle means is directed rearwardly externally of the air inlet of the propulsion unit and a high thrust position in which the air from the front nozzle means is directed to boost the supply of air to the air inlet of the propulsion unit. For example the diverter duct means may be adjustable by being rotated about a central axis.
In a further development a plenum chamber is provided intermediate the first and second fans for supplying air to the first fan in a forward direction and for supplying air to the second fan in a rearward direction.


REFERENCES:
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patent: 3033492 (1962-05-01), Rowe
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patent: 5383332 (1995-01-01), Angel
patent: 5996935 (1999-12-01), Snell
patent: 794768 (1958-05-01), None
patent: 935887 (1963-09-01), None
patent: 2 242 172 (1991-09-01), None
patent: WO 91/17083 (1991-11-01), None

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