Patent Publication Number: US-11661197-B2

Title: Cabin outflow air energy optimized cabin pressurizing system

Description:
This application is a continuation of U.S. patent application Ser. No. 15/824,650, filed Nov. 28, 2017, which claims the benefit of U.S. Provisional Patent Application No. 62/539,614, filed Aug. 1, 2017, the entire content of each of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to environmental control systems and, more particularly, to apparatus and methods for pressurizing an occupant environment of a vehicle. 
     In aircraft, traditional pneumatic systems use main engine bleed air to pressurize and condition the cabin. This approach can be compact and elegant. 
     However, the cabin pressurization function consumes the largest amount of power at altitude even when the bleed condition (pressure) matches the environmental control system (ECS) demand. The energy used to generate bleed air is only partially used, and a good portion of the energy is wasted due to the mismatch between the main engine (ME) operating conditions and cabin pressurization and air conditioning needs through various flight segments. 
     Recent movement towards More Electric Aircraft (MEA) uses cabin air compressors to pressurize ambient air to match the cabin pressure and air conditioning so little energy is wasted, but the cabin air compressor (CAC) is less efficient than the main engine compressor, and the operation is not at peak efficiency. 
     Also, the electrically driven CAC involves heavy motors and power electronics, demand for high electric power generation from ME and APU generators, and insatiable cooling requirement for its continuous safe operation. Failure mode conditions and redundancy requirements make the system even more complex and heavy. 
     As can be seen, there is a need for improved apparatus and methods to reduce power consumption for pressurizing the vehicle. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a pressurization system comprises a first compressor that receives a ram air, a fan air, and a bleed air; a first turbine that is on a common shaft with the first compressor and wherein the first turbine receives the bleed air; a main heat exchanger (hot side) downstream of the first compressor and the first turbine; an internal environment suitable for human occupants downstream of the main heat exchanger (hot side); a second turbine that is on a common shaft with the first compressor and first turbine downstream of the internal environment; and the main heat exchanger (cold side) is downstream of the second turbine. 
     In another aspect of the present invention, a pressurization system comprises a first compressor that receives a ram air, a fan air, and a bleed air; a first turbine that is on a common shaft with the first compressor and wherein the first turbine receives the bleed air; a main heat exchanger (hot side) downstream of the first compressor and the first turbine; an internal environment suitable for human occupants downstream of the main heat exchanger (hot side); a second turbine downstream of the internal environment; the main heat exchanger (cold side) is downstream of the second turbine; a generator that is on a common shaft with the second turbine; and a motor, that is on the common electric circuit, is on the common shaft with the first compressor and the first turbine. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a pressurization system according to an embodiment of the present invention; 
         FIG.  2    is a schematic diagram of a pressurization system according to a further embodiment of the present invention; 
         FIG.  3    is a graph of system power versus vehicle operating condition according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
     Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below. 
     Broadly, the present invention provides a pressurization system that can use, in the context of an aircraft for example, engine fan air boosted by a boost compressor, which is powered by a cabin outflow air turbine (COT), and then cooled by the COT exhaust. This invention can provide cabin pressurization without additional power draw from the aircraft, or ram air (drag) for cooling, resulting in ˜2% mission fuel burn savings. 
     The fan air of the present invention can take only about ⅕ to ⅓ of the power needed in comparison to when engine bleed air is used. And since the pressure boosted fan air may stay well below 400° F., a pre-cooler, which would be used with engine bleed air, is not needed. 
     Above altitude (e.g., 12,000 feet) where the fan air pressure is too low for cabin pressurization, the energy already “stored” in the cabin can be reclaimed for both mechanical power to boost the fresh fan air, and the COT exhaust air provides a heat sink to chill the boosted fan air as cabin fresh air intake. The power recovered from an outflow air stream follows the inverse profile of that needed for cabin pressurization. 
     Since the fresh air cooled by subfreezing expanded cabin air is cool enough to provide air conditioning function during cruise, ram air for the environmental control system (ECS) cooling of the interior environment will not be needed, and the eliminated ram drag about offsets the lost thrust recovery from an outflow valve. Thus, this invention can provide cabin pressurization without additional power draw from the aircraft, or ram air (drag) for cooling, resulting in ˜2% mission fuel burn savings. 
     The complete cabin pressurization cycle is powered by the dynamic head of the free stream air (ram air) plus the elevated total pressure by the engine fan, which are sufficient to offset the invention system losses (compressor/turbine efficiencies, ducting, and leakage). 
     Fresh air temperature entering the cabin is able to be maintained due to the temperature difference between the extremely cold ambient air and cabin air that offsets the thermal cycle efficiency losses (compressor/turbine efficiencies, heat exchanger). 
     Cabin air conditioning can be achieved by a vapor cycle subsystem with a consistently higher coefficient of performance on the ground and in low altitude flight, independent of cabin pressurization. 
     Although the present invention is described below in the context of an aircraft, the present invention is not so limited and may be implemented in other vehicles. 
     Herein, the term “direct” or “directly” is intended to mean that two components of the system are immediately upstream or downstream with one another and without a third component therebetween other than ducting or wiring between the two components. 
       FIG.  1    is a schematic diagram of an exemplary embodiment of a pressurization system  100  according to the present invention. The system  100  may include an engine compressor  103  that may produce a high pressure engine air  133 . In embodiments, an engine  101  may be a main engine and/or an auxiliary power unit (APU). If the system  100  is implemented in an aircraft, the engine air  133  may be an engine bleed air, such as from a compressor(s) of the main engine. 
     The system  100  may also include a fan  102 , such as when the system  100  is implemented for an aircraft. The fan  102  may use an outside (ambient) air to produce a fan air  132 . As contemplated by the present invention. The fan air  132  is from outside air boosted by the fan  102 . 
     From the fan  102 , the fan air  132  may flow to a downstream boost compressor (BC)  104 . On a common shaft with the boost compressor  104  may be a boost turbine (BT)  105 . The boost compressor  104  can be driven by either the boost turbine  105  or a cabin outflow turbine  108 . Accordingly, while the boost compressor  104  receives the fan air  132 , the boost compressor  104  may optionally receive, via an idling valve  123 , the engine air  133 . The boost turbine  105  may receive, via a bleed air valve  124 , the engine air  133 . 
     Air from the boost compressor  104  and/or the boost turbine  105  may flow to the hot side of a directly downstream main heat exchanger (MHEX)  106 . From the hot side of the heat exchanger  106 , pressurized or conditioned air may flow to a directly downstream interior occupant environment  107 , such as a cabin of an aircraft. 
     A cabin outflow air  134  may exit the environment  107  and, via a valve  125 , go overboard. Alternatively, or in addition, the cabin outflow air  134  may flow to a downstream outflow turbine  108 , such as a cabin outflow turbine (COT), via a variable geometry nozzle  126 . The outflow turbine  108  may drive the boost compressor  104  that is on the common shaft. 
     Also from the outflow turbine  108 , the cabin outflow air  134  may flow into the downstream cold side of the main heat exchanger  106 , and then discharged overboard, as shown by reference number  135  in  FIG.  1   . 
     In embodiments, a ram air (i.e., outside air)  131  can feed into the boost compressor  104  via a ram air valve  121 . In this arrangement, either the ram air  131  or the fan air  132  can flow into the boost compressor  104 , depending on the condition and section of the flight. For example, in hot days and low altitude (say less than 8,000 feet), ram air is selected; whereas in a cold day and low altitude, the warmer fan air is selected. 
     The provision of the ram air  131 , the fan air  132 , the engine air  133 , the ram air valve  121 , a fan air valve  122 , and the idling valve  123  provides for flexibility and matching of the conditioned air needs of the environment  107 , the phase of operation of the vehicle (e.g., aircraft), and energy savings. At a given phase of vehicle operation, one or more of the ram air  131 , the fan air  132 , and the engine air  133 , can be employed to pressurize the system  100 . 
     For example, in one phase of vehicle operation (e.g., when an aircraft is from sea level up to 8,000 feet in altitude), the system  100  may only employ the ram air  131  as the sole source of fresh air to pressurize the environment  107 . In a further phase of vehicle operation (e.g., when the aircraft is between 8,000 feet and cruise altitude), the system  100  may employ the fan air  132  as the fresh air source to pressurize the environment  107 . In another phase of vehicle operation (e.g., when the engine is idling as the aircraft is descending), the system  100  may only employ the engine air  133  which may be main engine air and/or APU bleed air. And in situations when the power from the cabin outflow turbine  108  is insufficient to drive the pressurization of the cabin  107 , the engine air  133  may be employed to drive the boost turbine  105  to supplement the power needed. 
     During the low altitude phase of operation, when neither the cabin outflow turbine  108  nor the boost compressor  104  are needed, the cabin outflow valve  125  is modulating to maintain the appropriate cabin  107  pressure. As the altitude increases, power is needed from the cabin outflow turbine  108  to drive the boost compressor  104 . The balancing of the power between the pair is accomplished by modulating the variable geometry nozzle  126  of the cabin outflow turbine  108 , and the cabin outflow valve  125  will be modulating down to complete shut off. 
       FIG.  2    is a schematic diagram of another exemplary embodiment of a pressurization system  200  according to the present invention. The system  200  is similar to the system  100  of  FIG.  1   . In the latter, the boost compressor  104 , boost turbine  105 , and outflow turbine  108  are connected by a common shaft. In most cases, however, it is not practical or possible to connect these components with high rotational speed on a common shaft. Accordingly, the system  200  may include other components similar in design and function to the components of the system  100 . 
     In embodiments, the system  200  may include all components included in system  100 . For example, an engine  201  may be an example of engine  101 , a fan  202  may be an example of fan  102 , an engine compressor  203  may be an example of engine compressor  103 , a boost compressor  204  may be an example of boost compressor  104 , a boost turbine  205  may be an example of boost turbine  105 , heat exchanger  206  may be an example of heat exchanger  106 , an occupant environment  207  may be an example of occupant environment  107 , a cabin outflow turbine  208  may be an example of cabin outflow turbine  108 , a ram air valve  221  may be an example of ram air valve  121 , a fan air valve  222  may be an example of fan air valve  122 , an idling valve  223  may be an example of idling valve  123 , a bleed air valve  224  may be an example of bleed air valve  124 , a cabin outflow valve  225  may be an example of cabin outflow valve  125 , a variable geometry nozzle  226  may be an example of variable geometry nozzle  126 , ram air  231  may be an example of ram air  131 , fan air  232  may be an example fan air  132 , and cabin outflow air  234  may be an example of cabin outflow air  134 . In addition, system  200  may further include an electric motor (synchronous) (SM)  211  that is on common shaft with the boost compressor  204 , an electric generator (permanent magnet)  210  that is on common shaft with the cabin outflow turbine  208 , and a private electric bus  212  connecting the motor  211  and generator  210 . And the cabin outflow turbine  208  is not on the common shaft with the boost compressor  204  and boost turbine  205 . Similar to the description of  FIG.  1   , from the outflow turbine  208 , the cabin outflow air  234  may flow into the downstream cold side of the heat exchanger  206 , and then discharged overboard, as shown by reference number  235  in  FIG.  2   . 
     The electric generator  210 , which can be a permanent magnet or otherwise, is driven by the cabin outflow turbine  208 . The electrical power generated by the generator is transmitted, via the private bus  212 , directly to the motor  211 , which can be a synchronous, induction, or a combination of both, which in turn drives the boost compressor  204 . 
     Since the cabin outflow turbine  208  and boost compressor  204  run at a constant speed ratio, when connecting the pair with the private bus  212 , the need for motor and generator controllers are eliminated. 
     In an embodiment with a synchronous motor, the synchronization of the motor to the generator may be achieved by flowing engine air  233  into the boost turbine  205  to match its shaft speed to the private bus  212  frequency. 
       FIG.  3    is a graph of system power versus vehicle operating condition according to an exemplary embodiment of the present invention. In the context of an aircraft, the operating conditions may range from airport taxi out to airport approach and land. 
     In  FIG.  3   , a first line having diamond-shaped symbols thereon represents power recovered from the outflow turbine  108 . In  FIG.  3   , a second line having square-shaped symbols thereon represents the power required for cabin pressurization. In  FIG.  3   , a third line having triangle-shaped symbols thereon represents the gap or difference between the power recovered (the first line) and the power required (the second line). The gap or deficiency can be “filled” by the booster turbine  105 , as represented by, with reference to  FIG.  3   , a fourth line having x-shaped symbols thereon. 
     As can be appreciated, the present invention eliminates the need of ram air for traditional bleed air cooling (pre-cooler, primary, secondary), and otherwise remove the ram drag that can offset the thrust recovered by cabin outflow valves. This no bleed system also means that the APU can be all electric, which can then be operated on the ground, during takeoff and climb, and during descent, to maximize APU run time. This architecture also relieves the main engine of maintaining rotor speed for generators (frequency) and bleed pressure for the ECS, which allows the main engines to pull the throttle back further during descent, and save fuel during that half hour of the flight. 
     It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.