Aeronautics and astronautics – Aircraft power plants – High altitude
Reexamination Certificate
1999-11-04
2001-09-04
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft power plants
High altitude
C454S071000
Reexamination Certificate
active
06283410
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a secondary power system for pressurized aircraft.
BACKGROUND OF THE INVENTION
Aircraft operating at altitudes above approximately 10,000 ft. are conventionally pressurized to avoid any need for supplemental oxygen for crew and passengers. Typically, the cabin pressure is maintained constant at about the atmospheric pressure typically found at an altitude of 10,000 ft. Moreover, the cabin air must be changed constantly, typically at the rate of 1 lb. per minute per passenger and crew member for passenger and crew comfort and well-being.
In the usual case, the air for pressurizing the cabin is drawn as bleed air from the main propulsion engines of the aircraft. It is then conditioned for temperature and humidity and distributed within the cabin. Ultimately, the air is discarded overboard through a cabin pressure vent/control valve.
The bleed air for cabin pressurization drawn from the main engines increases the fuel consumption of the main engines. The increased fuel burn is not insubstantial and as a consequence, poses constraints on aircraft range, particularly for large aircraft cruising at high altitudes for long periods of time and increases operating costs.
The current practice of discarding cabin air overboard from cabin pressure to ambient static pressure in such a way as to contribute to the thrust of the main engines is simple. However, it is an inefficient way to recover the energy in the cabin airstream. Needless to say, an improvement in energy recovery from cabin air provides an opportunity for fuel cost savings and/or an extension of aircraft range. Moreover, the ducting required to convey bleed air from the main engines not only adds weight to the airframe, but contributes somewhat to the complexity thereof and accordingly, to the capital cost of the aircraft. If such ducting can be eliminated, lower capital costs and lower fuel costs can be obtained. At the same time, it remains necessary to provide for cabin pressurization and cabin air change. To obtain the efficiencies of lesser capital costs and lower fuel costs, a more efficient system of cabin pressurization is highly desirable.
SUMMARY OF THE INVENTION
It is the principal object of the invention to provide a new and improved secondary power system for pressurized aircraft. More specifically, it is an object of the invention to provide such a system that makes more efficient use of cabin air to be discarded. It is also an object of the invention to provide such a system with the capabilities conventionally associated with an auxiliary power unit and to integrate such a system with an auxiliary power unit.
One exemplary and preferred embodiment of the invention envisions a turbo machine including a rotary compressor connected by a shaft to a rotary turbine wheel and a combustor connected to an outlet of the compressor, connected to a source of fuel to be combusted to provide gases of combustion, and connected to an inlet to the turbine wheel so that the gases of combustion may drive the turbine wheel to, in turn, drive the compressor. An inlet is provided to the compressor and ducting is adapted to be connected to an aircraft cabin and to the compressor inlet to provide air from the cabin to the compressor to be compressed thereby and delivered to the combustor to combust fuel therein. A load to be driven is connected to the turbo machine and a source of air under pressure is adapted to be connected to an aircraft cabin.
As a consequence of the foregoing, pressurized cabin air to be discarded is utilized to support combustion for the secondary power source. The cabin air, when the aircraft is cruising at altitude, will be at a higher pressure than the ambient so less work is required to raise the combustion air to the required pressure required to run the turbo machine. As a consequence, the requirement for less work lowers the quantity of fuel required to operate the secondary system.
In a preferred embodiment, the source of air under pressure is a turbo machine. In one embodiment, the source of air under pressure is the turbo machine forming part of the secondary system.
More specifically, the invention, in a highly preferred embodiment, contemplates that the source of air under pressure include a second rotary compressor coupled by a second shaft to a second rotary turbine wheel.
In an even more preferred embodiment, the second compressor, the second shaft and the second turbine wheel form part of the first mentioned turbo machine and the shafts are coaxial.
A preferred embodiment ofthe invention also contemplates the providing of an aircraft cabin. A low pressure rotary turbo machine is provided and includes a rotary load compressor connected by a first shaft to a rotary, low pressure turbine wheel. Also included is a high pressure rotary turbo machine which includes a rotary cycle compressor connected by a second shaft to a rotary high pressure turbine wheel.
A combustor such as mentioned previously is connected to an outlet of the cycle compressor and to a source of fuel for combusting the fuel as mentioned previously. The combustor directs the combustion gases to the high pressure turbine wheel to cause rotation of the same.
An ambient air inlet is provided for the load compressor and first ducting connects an outlet of the load compressor to the cabin to provide compressed air to pressurize the cabin. Second ducting connects the cabin to an inlet of the cycle compressor and third ducting connects an outlet of the high pressure turbine wheel to an inlet for the low pressure turbine wheel.
Again, the shafts may be coaxial. In a highly preferred embodiment, the first shaft is rotatable within the second shaft.
In one embodiment, at least one heat exchanger is provided in the first ducting and includes a coolant flow path in exchange relation with the first ducting.
In this embodiment of the invention, the coolant flow path preferably includes an inlet connected to receive ambient air.
Alternatively, the coolant flow path includes an inlet connected to the cabin to receive cabin air.
A highly preferred embodiment ofthe invention calls for the first ducting to include an environmental control system (ECS) rotary turbo machine which includes an ECS rotary compressor connected to an ECS turbine wheel. The one heat exchanger is located in the first ducting between the load compressor outlet and the ECS turbo machine and is connected to an inlet of the ECS compressor. Also included is a further heat exchanger that has a first flow path interconnecting an outlet of the ECS compressor to an inlet of the ECS turbine wheel. The first ducting further interconnects an outlet of the ECS turbine wheel to the cabin and the further heat exchanger also includes a second flow path for coolant which is in heat exchange relation with its first flow path.
According to a preferred embodiment of the invention as discussed immediately preceding, the second flow path has an inlet connected to receive ambient air. Alternatively, the second flow path has an inlet connected to the cabin to receive cabin air.
As mentioned previously, a load to be driven is connected to the turbine machine, and specifically, to the first shaft thereof.
One embodiment of the invention alternatively includes an ambient air inlet for the cycle compressor. A check valve may be located in the inlet to the cycle compressor so that the same may receive ambient air when the ambient air pressure is higher than that of the cabin air.
In a preferred embodiment of the invention, an inlet to the cycle compressor includes an inlet area varying device at the point of connection of the cycle compressor in the second ducting. In a highly preferred embodiment, the inlet air varying device comprises variable inlet guide vanes.
Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings.
REFERENCES:
patent: 4091613 (1978-05-01), Young
patent: 4261416 (1981-04-01), Hamamoto
patent: 4419926 (1983-12-01), Cronin et al.
patent: 4494372 (1985-01-01
Hamilton Sundstrand Corporation
Jordan Charles T.
Steele George L.
Wood Phillips VanSanten Clark & Mortimer
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