Refrigeration – Automatic control – Air compessor – cooler and expander
Reexamination Certificate
1999-10-05
2001-02-20
Capossela, Ronald (Department: 3744)
Refrigeration
Automatic control
Air compessor, cooler and expander
C062S402000
Reexamination Certificate
active
06189324
ABSTRACT:
TECHNICAL ART
The instant invention relates generally to air cooling systems and more specifically to an environmental control unit for supplying cool, dry air to an aircraft cabin.
BACKGROUND OF THE INVENTION
The instant invention relates generally to air cycle machines used to produce a cool air supply and more particularly to an environmental control unit integrated with a gas turbine engine to provide cabin ventilation and temperature and pressure control in a jet aircraft application. Ram air and/or bypass duct air are used to cool pressurized, compressed air bled from the engine compressor. The compressed air further cools as it expands through a turbine.
Prior art aircraft environmental control units utilize high pressure air bled from the compressor section of a turbine engine to supply working fluid to an air-cycle machine for production of pressurized cooling air to an aircraft cockpit/cabin. A basic bootstrap air-cycle machine comprises a small compressor driven by bleed air mechanically coupled to a turbine. The hot compressed air exiting the compressor is introduced to a heat exchanger where it is partially cooled by cooling air obtained from, for example, an air bypass duct used to exhaust a portion of “ram” air entering the engine. The partially cooled air is then directed to the turbine of the bootstrap cycle machine and is further cooled as it expands through the turbine prior to introduction to the aircraft cabin.
Many prior art environmental control systems employ ground air fans to introduce cooling air into the heat exchangers when the aircraft is stationary. This feature provides cooler cabin air when ram air or bypass duct air is unavailable. Combined simple/bootstrap cycle air machines incorporate a fan stage between the compressor and turbine thereby reducing the number of parts required to introduce cool air into the turbine and heat exchanger and improving cost and efficiency.
Environmental control units are often equipped with water separators to remove moisture from the air prior to introduction in to the cabin. Various air filtration systems are also employed to remove particulate matter and odors deleterious to passenger health and comfort. Digital electronic controls employed to monitor and actuate system components provide maximum efficiency of operation and passenger comfort.
The use of compressed air to drive the aforementioned air-cycle machines reduces the volume of air available for engine combustion, thereby reducing available power and fuel efficiency. Additionally, since not all cooling air produced by the environmental control units is required for cabin ventilation and cooling, some energy is always wasted. While the application of digital electronic controllers to monitor system operation and cabin demand has improved the operating efficiency of existing environmental control units, a great deal of energy is still exhausted from known in the art air-cycle turbine.
SUMMARY OF THE INVENTION
The instant invention overcomes the aforementioned problems by providing an environmental control unit to produce cooled air for an aircraft that utilizes multiple aircraft engine compressor bleed air ports to supply an air cycle cooling circuit with working fluid. A digital electronic control is employed to control a plurality of flow valves so that low pressure bleed air to supplies the air cycle cooling circuit when aircraft cooling requirements are minimal, and higher pressure bleed air is used when conditions so demand. The electronic control is used to monitor all environmental control unit temperatures, pressures, and rotational velocities and position all system control valves and dampers.
The air cycle cooling circuit employs a plurality of heat exchangers to cool the working fluid bled from the compressor prior to its entry into an air cycle turbine. As the working fluid expands through the turbine, it cools and effects rotation of the turbine. In order to utilize the energy that otherwise would be wasted by the expansion of the working fluid, the turbine drives an alternator to produce alternating current electrical power for the aircraft.
Additionally, the instant invention provides a heat exchanger disposed in an aircraft engine bypass duct to assist in cooling the working fluid. This arrangement is thermodynamically desirable since heat from the working fluid is added to the bypass fluid of the engine prior to exiting the engine, thereby increasing it's energy and it's ability to propel the aircraft.
In a preferred embodiment of the instant invention the electronic control is employed to synchronize the speed of the air cycle turbine alternator with the speed of the engine alternator, to produce electrical power at identical frequencies. This embodiment of the instant invention efficiently utilizes the energy bled from the compressor in the form of compressed air to produce usable electrical power for the aircraft without the need for ancillary power conditioning components. In an alternative embodiment of the instant invention the power output of the turbo-alternator is conditioned in a voltage rectifier to produce direct current power for the aircraft's direct current power bus. This embodiment of the instant invention obviates the need for precise sychronization of alternator speeds while allowing the power produced by the environmental control unit turbo-alternator to be available for use by the aircraft systems at all times.
In an alternative embodiment of the instant invention, the turbo-alternator is used to drive a compressor in a bootstrap cycle arrangement. This embodiment of the instant invention allows low pressure air to be bled from the engine compressor as a source of working fluid, and then compressed by the environmental control unit compressor thereby reducing the deleterious effect of compressor bleed on aircraft engine performance.
Therefore, one object of the instant invention is an environmental control unit to produce cooling air for an aircraft cabin that demands minimal energy from an aircraft engine.
A further object of the instant invention is an environmental control unit that produces electrical power to be used by an aircraft.
A yet further object of the instant invention is an environmental control unit that returns a portion of the heat energy bled from an aircraft engine to operate the control unit back into the propulsion stream thereof.
Additional objects, features, and advantages of the present invention will become apparent from the subsequent detailed description, taken in conjunction with the accompanying drawing figures.
REFERENCES:
patent: 4445342 (1984-05-01), Warner
patent: 5086622 (1992-02-01), Warner
patent: 5704218 (1998-01-01), Christians et al.
patent: 5860283 (1999-01-01), Coleman et al.
patent: 5934083 (1999-08-01), Scherer et al.
patent: 5956960 (1999-09-01), Niggeman
SAE Technical Paper Series 932057, “What's Next in Commercial Aircraft Environmental Control Systems?” By Kim Linnett and Robert Crabtree. Copyright 1993 Society of Automotive Engineers, Inc.
Jones John F.
Thompson Jr. Robert S.
Williams Samuel B.
Capossela Ronald
Lyon P.C.
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