Propulsion system

Details Propulsion system Propulsion system

1999-05-05

2001-04-10

Thorpe, Timothy S. (Department: 3746)

Power plants

Combustion products used as motive fluid

Rotating combustion products generator and turbine

Reexamination Certificate

active

06212874

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a propulsion system for an aircraft or the like and more particularly to a tip mounted gas turbine engine for a helicopter.
BACKGROUND FOR THE INVENTION
Rotary winged aircraft or helicopters as they are more common known typically include a plurality of wings or blades commonly referred to as rotors which rotate about a shaft or mast. Such aircraft also include propulsion means such as a jet engine for rotating the rotors.
Helicopters have also been powered by the thrust of ram jets which are located at the tips of rotors or blades. For example, a Hiller Model H-J Hornet, a small two-place ram jet powered helicopter became the first ram jet powered unit to be certified in the United States and also the first C.A.A. approved tip mounted power plant for helicopters.
However, the use of tip mounted ram jets has not proven to be very useful because the ram jets are inefficient at the speeds that can be achieved at the tip of the rotor or blade. Both from a strength standpoint and from a shock wave standpoint, the speed is limited. The problem is that the ram compressor is less than the impact pressure because the airflow is not stopped (as it would be on impact), but instead can only be slowed down to the velocity needed to support the flame and exhaust velocity that gives thrust to the jet.
Another approach to a turbine engine which is mounted at the tip ends of helicopter rotor blades is disclosed in the U.S. patent of R. K. Grove No. 2,843,210. As disclosed therein, an angle mounted tip engine for aircraft sustaining rotors includes a vertical shafted power mechanism. The axis of th e vertical power shaft inclines slightly forward in terms of its translatory direction of orbital motion. The angle mounted tip engine also includes vertically spaced apart compressor and turbine members wherein the turbine member includes hollow stator vanes which are cooled by a stream of air conducted by a U-shaped conduit which bleeds off compressed air from the compressor member.
A more recent development is disclosed in my allowed copending application Ser. No. 08/939,715 entitled Helicopter Rotor Tip Jet. In that application, a helicopter includes a rotary wing and a ram jet engine mounted at the outer tip of the rotor for propelling the rotor a round the mast. The rotor or rotary wing also includes air inlet means at a distance from its tip and means for directing a flow of air which is subjected to centrifugal force through the rotor and into the ram jet engine to thereby increase the thrust of the ram jet engine.
It is presently believed that there may be a commercial market for an improved propulsion system in accordance with the present invention. There may be a commercial demand for such systems for use as a tip mounted gas turbine engine for a helicopter. The engine in accordance with the present invention are believed to be of relatively compact size with a relatively shallow aerodynamic design.
In addition, the propulsion system or engine in accordance with the present invention incorporates a vertically shafted power mechanism with one or more coaxial compressors and turbine sections and are constructed and arranged in a manner which should minimize any twisting moment on the rotor blade.
BRIEF SUMMARY OF THE INVENTION
In essence, the present invention contemplates a propulsion system or aircraft engine which is particularly applicable for use on the tip of a helicopter rotor. The system or engine includes an aerodynamic pod or housing with a forward and rear portion and a longitudinal axis. A forwardly facing inlet in the forward portion of the pod is adapted to receive a flow of ram air and to direct the ram air into and through the engine. In a preferred embodiment of the invention, the ram air flows along the longitudinal or horizontal axis as it passes through the inlet. The engine also includes an exhaust outlet in a rear portion thereof which in the preferred embodiment lies on or near its longitudinal axis. A generally vertical shaft is disposed within the housing transversely of the longitudinal axis. One or more gas turbine assemblies are disposed on the vertical shaft for rotation thereabout. Each of the gas turbine assemblies or units include a coaxial compressor and turbine rotor which are formed on a single disk or wheel. For example, in a preferred embodiment of the invention each turbine assembly includes a single disk or wheel having a compressor rotor or section including a plurality of blades with a first pitch on an inner portion thereof and a turbine rotor or section with a plurality of blades with a reverse pitch on an outer portion of the disk. The system also includes a combustion chamber downstream from the compressor, and means for injecting fuel into the combustion chamber. Means for igniting the fuel air mixture are also provided within the combustion chamber in a conventional manner. Means such as an inner housing are also provided for redirecting the ram air through a turn of about 90° and through the compressor rotor and into the combustion chamber. Additional means are provided for directing gases from the ignited fuel air mixture through the turbine rotor and through a nozzle and out of the outlet.


REFERENCES:
patent: 2843210 (1958-07-01), Grove
patent: 3240018 (1966-03-01), Bar

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