Abstract:
An environmental conditioning system has a compressor for compressor air in an air flow path. A turbine drives the compressor and is coupled to the compressor. An evaporator is in communication with the compressor. The evaporator is configured to cool air from the compressor.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an environmental conditioning system for a vehicle, such as an aircraft. 
     In flight, an aircraft may obtain conditioned air from a compressor of a turbine engine. Bleed air is output at a high temperature from the compressor and is passed through a heat exchanger to lower the air&#39;s temperature. The air eventually passes to the passenger compartment. This process of conditioning air from the compressor is known as an air cycle. 
     This method of conditioning air is inefficient. More energy than is necessary is used to condition the air because the pressure delivered by the engine compressor exceeds the pressure required for adequate conditioning at most operating points and is throttled away. Generating the unnecessary pressure is inefficient use of power. As a consequence of the inefficiency of the environmental conditioning system, the aircraft consumes more fuel than necessary. 
     A need therefore exists for more efficient environmental conditioning system for use on an aircraft. 
     SUMMARY OF THE INVENTION 
     An environmental conditioning system has a compressor for compressing air in an air flow path. A turbine drives the compressor. The turbine is coupled to the compressor. An evaporator is in communication with the compressor in the air flow path. The evaporator is configured to cool air from the compressor. 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic view of the inventive environmental conditioning system, including compressor, turbine and evaporator. 
         FIG. 2  illustrates the environmental conditioning system of  FIG. 1  with the addition of another evaporator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIG. 1 , there is shown a schematic view of an inventive environmental conditioning system  10  for a vehicle, such as an aircraft. As shown, there is air flow path  18 , through which air is obtained from air source  58  and conditioned for use in passenger compartment  54 . In air flow path  18  are compressor  11 , heat exchanger  30 , reheater  38 , evaporator  26 , water removal device  34  and turbine  22 . Compressor  11  is coupled to turbine  22  by shaft  12 . Compressor  11  is driven by turbine  22  and may also receive power from motor  42 . 
     Air from air source  58 , such as an outside air source or bleed air from another compressor (not shown), is communicated to compressor  11 . Compressor  11  pressurizes and thereby heats air in air flow path  18  and directs air to heat exchanger  30 . Heat exchanger  30 , which may be one heat exchanger or a series of heat exchangers, rejects heat to a heat sink and thereby reduces the temperature of air from compressor  11 . The heat sink may be cooled by ambient air. Air flow then moves from heat exchanger  30  to reheater  38  and then to first evaporator  26 . Air from the first evaporator  26  serves as the heat sink for the reheater  38  which reduces the heat transfer required by the evaporator  26 . 
     At first evaporator  24 , air in air flow path  18  can be significantly and efficiently reduced in temperature. First evaporator  24  is a vapor cycle evaporator with refrigerant. Refrigerant compressor and condenser are not shown but supply first evaporator  26  with refrigerant gas as known to cool first evaporator  26 . First evaporator  26  cools air in air flow path  18  causing moisture in air to condense. This moisture is then removed by water removal device  34 . Air is then passed through reheater  38  to be reheated. Turbine  22  then directs air along air flow path  18  to passenger compartment  54  and expands the air reducing the temperature and pressure of the air further. 
     Turbine  22  may receive power from the bleed air of a compressor (not shown) from a turbine engine. Motor  42  is attached to shaft  12  and can provide additional power to compressor  11  and turbine  22  when bleed air pressure from the turbine engine is inadequate. Motor  42  is controlled by control unit  46 , which operates to control the speed of rotation of shaft  12  thereby controlling the speed of rotation of compressor  11  and turbine  22 . In this way, the amount of air supplied to compartment  54  can be controlled. 
     Raising the speed of motor  42  and therefore compressor  11  and turbine  22  results in increasing air flow to passenger compartment  54  while decreasing motor speed decreases air flow to passenger compartment  54 . If there is excess power available to turbine  22  and compressor  11 , this additional power may be used to drive a ram air heat sink for heat exchanger  30 . 
     As a consequence of this design, the power required to condition air for passenger compartment  54  is optimized because the amount of heat removed by first evaporator  26  can be great without a substantial consumption of energy. By using an evaporator in conjunction with the heat exchanger, an efficient balance can be reached between conditioning by an air cycle and a vapor cycle. Furthermore, reheater  38  and first evaporator  26  can be designed so as to provide conditioned air at a desired supply temperature and relative humidity. 
     Also, with motor  42 , air source pressure can be used when it is most effective for cooling or can be augmented through power from motor  42  if it is not. In this way, air from compressor  11  need not be over-pressurized at off design conditions to meet the highest cooling requirements. The amount of air flow through environmental conditioning system  10  can be controlled by the power input from motor  42  to shaft  12 . 
     With reference to  FIG. 2  there is shown an additional evaporator, second evaporator  50 , which is added to the environmental conditioning system  10  of  FIG. 2 . Second evaporator  50  is also vapor cycle evaporator with refrigerant. As shown, second evaporator  50  obtains air from passenger compartment  54 . Excess heat in air from passenger compartment  54  is removed by second evaporator  50  through another vapor cycle evaporation process. In this way, recirculated air from passenger compartment  54  may be conditioned and mixed with fresh air from air source  58  into passenger compartment  54  providing an efficient combination of both fresh and recirculated air. A proportion of fresh air can be provided with recirculated air so that a high quality of air may be maintained in passenger compartment  54  without large energy consumption by environmental conditioning system  10 . 
     Refrigerant that exits second evaporator  50  is controlled to desired levels of superheat. Refrigerant is then communicated to first evaporator  26  through refrigerant flow path  86 , which is then passed to refrigerant compressor  70 , which is part of the vapor cycle of environmental conditioning system  10 . Refrigerant compressor  70  compresses refrigerant for first evaporator  26  and second evaporator  50 . Compressed refrigerant is then passed to refrigerant condenser  72 , or a subcooler, which then returns refrigerant either to second evaporator  50  or to first evaporator  26 . First valve  78  and second valve  82  are provided and controlled by valve control unit  90 , which determines what proportion of refrigerant from refrigerant condenser  72  to return to first evaporator  26  and to return to second evaporator  50 . In this way, the cooling demands between the two evaporators, first evaporator  26  and second evaporator  50 , can be balanced. Because first evaporator  26  and second evaporator  50  are in series along refrigerant flow path  86 , the total required refrigerant flow is minimized. Also, first evaporator  26  is typically exposed to higher temperature air and therefore can be used to impose substantial superheat into the system if desired. The superheat can be used to drive up the discharge temperature of vapor cycle compressor  70  and enable more efficient operation. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.