Abstract:
A method for operating an air-conditioning system for an aircraft includes compressing ambient air with a compressor driven by a shaft in communication with a motor and a turbine. The method includes forwarding the compressed air to an aircraft cabin for circulation and removing circulated compressed air from the aircraft cabin. The method also includes forwarding the circulated compressed air to the turbine, depressurizing the circulated compressed air in the turbine and capturing energy created by depressurizing the circulated compressed air.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present disclosure relates to air conditioning and pressurizing systems for an aircraft, and more specifically, operations of the air conditioning and pressurizing systems for an aircraft. 
         [0002]    Aircraft air-conditioning systems may include compressors operated with ambient air. These systems receive ambient air from outside the aircraft and utilize the compressor to adjust the air pressure before sending the air into the cabin of the aircraft. The ambient air pressure, and other conditions, varies considerably depending on the flight altitude. Such variations can affect the performance and efficiency of the compressors. The large demanded operation range that results from the variance in operating conditions cannot be covered completely in an efficient manner by one compressor. 
         [0003]    Accordingly, aircraft air-conditioning systems have been developed that utilize more than one compressor. These multi-compressor aircraft air-conditioning systems include various operating modes in which various combinations of the various compressors are used. One drawback of these multi-compressor aircraft air-conditioning systems is that the systems place an increased power demand on the aircraft. In addition, currently available multi-compressor aircraft air-conditioning systems rely on external conditions, such as the ambient air pressure, to determine the operating mode of the aircraft air-conditioning system. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one embodiment, a method for operating an air-conditioning system for an aircraft includes compressing ambient air with a compressor driven by a shaft in communication with a motor and a turbine. The method also includes forwarding the compressed air to an aircraft cabin for circulation and removing circulated compressed air from the aircraft cabin. The method further also includes forwarding the circulated compressed air to the turbine, depressurizing the circulated compressed air in the turbine and capturing energy created by depressurizing the circulated compressed air. 
         [0005]    In another embodiment, an air-conditioning system for an aircraft, includes a first compressed air source formed by a first compressor charged with ambient air and driven by a motor and a turbine and whose outlet is in direct or indirect communication with the aircraft cabin. The system also includes a discharge device operable for removing circulated compressed air from the aircraft cabin and a controller that controls the operation of first compressed air source and the discharge device. When an ambient air pressure is lower than a cabin air pressure, the controller instructs the discharge device to forward the circulated compressed air from the aircraft cabin to the turbine and when the ambient air pressure is equal to the cabin air pressure, the controller instructs the discharge device to forward the circulated compressed air from the aircraft cabin out of the aircraft. The turbine depressurizes circulated compressed air received from the aircraft cabin and captures energy created by depressurization. 
         [0006]    In yet another embodiment, an air-conditioning system for an aircraft includes a first compressed air source formed by a first compressor charged with ambient air and driven by a motor and a turbine and whose outlet is in direct or indirect communication with the aircraft cabin. The system also includes a discharge device operable for removing circulated compressed air from the aircraft cabin and a controller that controls the operation of first compressed air source and the discharge device. When a difference between an ambient air pressure and a cabin air pressure exceeds a threshold value, the controller instructs the discharge device to forward the circulated compressed air from the aircraft cabin to the turbine and when the difference is below the threshold value, the controller instructs the discharge device to forward the circulated compressed air from the aircraft cabin out of the aircraft. The turbine depressurizes circulated compressed air received from the aircraft cabin and captures energy created by depressurization. 
         [0007]    Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a block diagram of an aircraft air-conditioning system in accordance with one embodiment of the present disclosure; 
           [0010]      FIG. 2  is a schematic representation of an aircraft air-conditioning system in accordance with another embodiment of the present disclosure; and 
           [0011]      FIG. 3  is a block diagram of an aircraft air-conditioning system including a pressure recovery system in accordance with an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to  FIG. 1 , a block diagram of an aircraft air-conditioning system  10  is shown. The aircraft air-conditioning system  10  includes a first compressed air source  12  that can be connected directly or indirectly to the aircraft cabin  20 . The first compressed air source  12  includes a compressor  14 , a motor  16  and a turbine  18 . The compressor  14 , motor  16  and turbine  18  are in communication with one another via a shaft  28 . The shaft  28  can be unitary or formed of multiple pieces. The compressor  14  receives ambient air  15  and using power provided from either or both of the motor  16  and the turbine  18  compresses the ambient air and forwards compressed ambient air to the aircraft cabin  20 . The aircraft air-conditioning system  10  also includes a secondary compressed air source  22 , which may also include one or more motors and compressors, which can be connected directly or indirectly to the aircraft cabin  20 . The compressors used in the aircraft air-conditioning system  10  may, for example, be a single-stage or also multistage compressors. The compressors used by the first and second compressed air sources  12 ,  22  require substantial power to operate. 
         [0013]    In one embodiment, the aircraft air-conditioning system  10  is designed to be operated in various modes depending upon the available power in the aircraft. The aircraft air-conditioning system  10  can include a controller  24  which receives a signal  25  from the aircraft control system (not shown) that is indicative of the available power in the aircraft. The controller  24  controls the operation of the first and second compressed air sources  12 ,  22  based upon the available power in the aircraft indicated by signal  25 . 
         [0014]    In a first operating mode, when the available power in the aircraft is below a threshold value the air supplied to the aircraft cabin  20  is provided only from the first compressed air source  12 . This first compressed air source  12  is designed to be able to provide the required pressurization, temperature control and fresh air supply of the cabin during ground operation of the aircraft. In a second operating mode, when the available power in the aircraft is above a threshold value the air supplied to the aircraft cabin  20  is provided from both the first and second compressed air sources  12 ,  22 . In one embodiment, the two compressed air sources can be mixed and then the mixed air can be further treated, such as cooling, humidification or dehumidification before being forwarded to the aircraft cabin. In another embodiment, more than two compressed air sources may be utilized when the available power in the aircraft is above a second threshold value the air supplied to the aircraft cabin  20  can be provided from the first, second and third compressed air sources. 
         [0015]    In one embodiment, the compressed air is cooled prior to the entry into the aircraft cabin  20 . The cooling may be done by a ram air heat exchanger (not shown) located in a ram air duct of the aircraft and/or by the turbine  18 . In the first operating mode, the cooling can be done by both the ram air heat exchanger and by the turbine  18  integrated in the cooling process, with the turbine  18  being coupled on a shaft to the compressor  14  and to the motor  16 . One or more turbines  18  can be located on the shaft  28  with the compressor  14 . 
         [0016]      FIG. 2  shows a schematic representation of an aircraft air-conditioning system  100  in accordance with an embodiment of the present disclosure. The air-conditioning system  100  includes a first compressed air source  101  that includes a compressor  102  charged with ambient air. The compressor  102  is in communication with a motor  104  and a turbine  106  on a shaft  108 . The aircraft air-conditioning system  100  also includes a second compressed air source  103  that can be switched on depending on the operating mode in which the system is operated. In one embodiment, the second compressed air source  103  can be switched on or off or also partially switched on by a modulating valve  110 . In another embodiment, a check valve can also be arranged instead of the modulating valve  110 . The second compressed air source can, for example, be a second motorized compressor  128  charged with ambient air and/or bleed air from the control system of the aircraft. The outlet line of the compressor  102  has a check valve  112  which ensures that the flow through this outlet line does not lead toward the compressor  102 . 
         [0017]    The system of  FIG. 2  can be operated in at least two operating modes based upon the available power in the aircraft. In a first operating mode, the total air supply for the cabin is provided by the compressor  102 . The power from the turbine  106 , together with the power from the motor  104 , the drive of the compressor  102 . The compressor  102  is designed to be able to meet the air supply demands of the cabin with respect to pressurization, temperature regulation and fresh air supply. The air output from the compressor  102  is cooled in the ram air duct heat exchanger  114  after passing through the mixing chamber  116 . This air subsequently flows through a water extraction circuit and is then subjected to a second cooling in the turbine  106 . The water extraction circuit may include a water extractor  118 , a reheater  138  and a condenser  120 . The water separated in the water extractor  118  may be supplied to the ram air duct via a water injector WI. 
         [0018]    In a second operating mode, the valve modulating valve  110 , or check valve, is opened and the air provided to the cabin is now formed by the outlet air of the compressor  102  and by the outlet air of the compressor  128 . In the second operating mode, the mixed air flow flows through the same components as the outlet air of the compressor  102  in the first operating mode. 
         [0019]    Due to the high demanded pressure ratio of the individual compressor stages based on single-stage compression, these compressor stages only achieve a limited operating range for the corrected mass flow. To be able to deliver the corrected mass flow, additional compressor stages or compressed air sources may be switched in parallel. The number of ambient air compressors utilized is not fixed in this connection, with a parallel connection of at least two compressed air sources per air-conditioning system taking place to cover the total application area. 
         [0020]    As shown in  FIG. 2 , the second compressed air source  103  can be used with an open valve  122  to operate the jet pump  124 . This has the result that a coolant air flow is also ensured in the first operating mode via the ram air heat exchanger or exchangers. The compressor outlet air of the compressor  102  can also be supplied to the jet pump  124  via a valve  126 . Such a procedure may ensure a safe/stable operation of the compressor  102 . The additional mass flow is thereby directed via the jet pump  124  into the ram air duct or is alternatively supplied to further consumers. A ram air duct inlet valve may be located at the inlet side of the ram air duct and can be controlled by the ram air inlet actuator (RAIA). 
         [0021]    In one embodiment, the second compressed air source  103  is formed by compressor  128  which is driven by a motor  130 . It will be appreciated by one of ordinary skill in the art that one or more of these units can also be provided in the system  100 . In one embodiment, recirculation lines which can be closed by anti-surge valves  132 ,  134  are drawn for the compressors  102  and  128 , respectively. Furthermore, a further compressor load valve  136  is provided in the line extending from the mixing chamber  116  to the ram air duct heat exchanger  114 . The recirculation air can be increased via the compressors  102 ,  128  by opening the valve anti-surge valves  132 ,  134 , whereby a stable operation of the compressors  102 ,  128  is enabled. As stated above, the increase in the compressor mass flow can also be realized via the jet pump modulating valves  122 ,  126 . The compressor load valve  136  can be used to restrict the compressors  102 ,  128  and increase the exit temperature of the compressors  102 ,  128 . 
         [0022]    Turning now to  FIG. 3 , a block diagram of an aircraft air-conditioning system  10  is shown. The aircraft air-conditioning system  10  includes a first compressed air source  12  that can be connected directly or indirectly to the aircraft cabin  20 . The first compressed air source  12  includes a compressor  14 , a motor  16  and a turbine  18 . The compressor  14 , motor  16  and turbine  18  are in communication with one another via a shaft  28 . The compressor  14  receives ambient air and using power provided from the motor  16  and turbine  18  compresses the ambient air and forwards the ambient air to the aircraft cabin  20 . The aircraft air-conditioning system  10  also includes a secondary air source  22 , which may also include one or more motors or compressors, which can be connected directly or indirectly to the aircraft cabin  20 . The controller  24  receives a signal from the aircraft control system that is indicative of the available power in the aircraft and responsively controls the operation of the first and second compressed air sources  12 ,  22  based upon the available power in the aircraft. 
         [0023]    In current aircraft air-conditioning systems, after being circulated through the cabin pressurized air is removed from the cabin and discarded (i.e., sent “overboard”). Depending upon the altitude of the aircraft, the air pressure outside of the aircraft can be significantly lower than the air being discarded. In one embodiment, the pressurized air being discarded from the cabin  20  is forwarded to the turbine  18 , which captures the energy created as the air is depressurized to the ambient air pressure. After passing through the turbine  18 , the depressurized air from the cabin is sent overboard. In one embodiment, the turbine  18  may provide the energy captured from the depressurization of the air being discarded from the cabin to the shaft  28  coupled to the motor  16  and the compressor  14 . This energy can be used to reduce the energy required from the aircraft to operate the aircraft air-conditioning system  10 . 
         [0024]    In one embodiment, the aircraft air-conditioning system  10  also includes a discharge device  26 , which may be located in the aircraft cabin  20 . The discharge device  26  may be controlled by the controller  24 , which can instruct the discharge device  26  to forward the circulated air from the aircraft cabin  20  to either the turbine  18  or out of the aircraft. In one embodiment, the controller  24  may instruct the discharge device  26  to forward the circulated air from the aircraft cabin  20  to the turbine  18  if the ambient air pressure is lower than the cabin air pressure and to forward the circulated air from the aircraft cabin  20  out of the aircraft if the ambient air pressure is equal to, or approximately equal to, the cabin air pressure. In another embodiment, the controller  24  may instruct the discharge device  26  to forward the circulated air from the aircraft cabin  20  to the turbine  18  if the difference in the ambient air pressure and the cabin air pressure exceeds a threshold value and to forward the circulated air from the aircraft cabin  20  out of the aircraft if the difference in the ambient air pressure and the cabin air pressure is below a threshold value. 
         [0025]    In one operating mode the aircraft may be in an environment with an ambient air pressure of approximately three Psi, or approximately 20.6 kPa, and have a cabin pressure of approximately twelve Psi, or approximately 82.7 kPa. The aircraft air-conditioning system  10  requires approximately one hundred kilowatts of power to pressurize the ambient air from 3 Psi to 12 Psi. In currently available aircraft air-conditioning systems, all of the power needed to pressurize the ambient air is provided from the motor  16 . In one embodiment, the turbine  18  captures the energy created by the depressurization of the air being discarded from the cabin and provides the power it creates to the motor  16  and the compressor  14 . In the operating mode with an ambient air pressure of approximately three Psi and a cabin pressure of approximately twelve psi, the turbine  18  may generate approximately twenty kilowatts of power. Accordingly, depending upon the operating conditions of the aircraft, capturing the energy created from the depressurization of the discarded air from the cabin can result in up to a twenty percent reduction in power consumption of the aircraft air-conditioning system. 
         [0026]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
         [0027]    The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated. 
         [0028]    While the preferred embodiment to the disclosure had been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.