Patent Description:
Aircraft need to have their internal environment controlled. In general, contemporary air conditioning systems are supplied a pressure at cruise that is approximately <NUM> psig to <NUM> psig (<NUM> kPa - <NUM> kPa). The trend in the aerospace industry today is towards systems with higher efficiency. One approach to improve efficiency of an aircraft environmental control system is to eliminate the bleed air entirely and use electrical power to compress outside air. A second approach is to use lower engine pressure. The third approach is to use the energy in the cabin outflow air to compress outside air and bring it into the cabin. Each of these approaches provides a reduction in airplane fuel burn.

<CIT> discloses an air conditioning of a cooling system. <CIT> discloses an environmental control system of an aircraft.

According to a first aspect, an environmental control system of an aircraft is provided according to claim <NUM>.

In addition to one or more of the features described above, in further embodiments comprising a dehumidification system arranged in fluid communication with the ram air circuit, wherein the first medium output from the at least one turbine is used as a heat sink within the dehumidification system.

In addition to one or more of the features described above, in further embodiments a portion of the dehumidification system is arranged within the ram air shell.

In addition to one or more of the features described above, in further embodiments comprising another compressing device arranged in fluid communication with and downstream from the compressing device.

In addition to one or more of the features described above, in further embodiments the another compressing device includes another compressor, and an outlet of the first compressor and an outlet of the second compressor are fluidly connected to an inlet of the another compressor.

In addition to one or more of the features described above, in further embodiments comprising a heat exchanger arranged between the outlet of the first compressor, the outlet of the second compressor and the inlet of the another compressor and the compressor, wherein the second medium is cooled within the heat exchanger.

In addition to one or more of the features described above, in further embodiments the plurality of mediums further includes a third medium, the second medium being cooled by the third medium within the heat exchanger.

In addition to one or more of the features described above, in further embodiments the second medium is fresh air and the third medium is cabin discharge air.

In addition to one or more of the features described above, in further embodiments comprising a dehumidification system arranged in fluid communication with the ram air circuit.

In addition to one or more of the features described above, in further embodiments a portion of the dehumidification system is arranged within the ram air circuit.

In addition to one or more of the features described above, in further embodiments comprising a divider arranged within the ram air shell to separate the ram air shell into a first region and a second region, the at least one ram air heat exchanger being arranged within the first region and the portion of the dehumidification system being arranged within the second region.

In addition to one or more of the features described above, in further embodiments the at least one ram air heat exchanger is a separate component from the portion of the dehumidification system arranged within the second region.

In addition to one or more of the features described above, in further embodiments the at least one ram air heat exchanger and the portion of the dehumidification system arranged within the second region are integrally formed.

In addition to one or more of the features described above, in further embodiments the portion of the dehumidification system within the ram air circuit is the another component.

Embodiments herein provide an environmental control system of an aircraft that mixes mediums from different sources to power the environmental control system and to provide cabin pressurization and cooling at a high fuel burn efficiency. The medium can generally be air, while other examples include gases, liquids, fluidized solids, or slurries.

With reference now to <FIG>, a schematic diagram of a portion of an environment control system (ECS) <NUM>, such as an air conditioning unit or pack for example, is depicted not according to the claims. Although the environmental control system <NUM> is described with reference to an aircraft, alternative applications are also within the scope of the disclosure. As shown in the FIGS. , the system <NUM> can receive a first medium A1 at a first inlet <NUM>. In embodiments where the environmental control system <NUM> is used in an aircraft application, the first medium A1 may be bleed air, which is pressurized air originating from i.e. being "bled" from, an engine or auxiliary power unit of the aircraft. It shall be understood that one or more of the temperature, humidity, and pressure of the bleed air can vary based upon the compressor stage and revolutions per minute of the engine or auxiliary power unit from which the air is drawn.

The system <NUM> is also configured to receive a second medium A2 at an inlet <NUM> and may provide a conditioned form of at least one of the first medium A1 and the second medium A2 to a volume <NUM>. In an embodiment, the second medium A2 is fresh air, such as outside air for example. The outside air can be procured via one or more scooping mechanisms, such as an impact scoop or a flush scoop for example. Thus, the inlet <NUM> can be considered a fresh or outside air inlet. In an embodiment, the second medium A2 is ram air drawn from a portion of a ram air circuit to be described in more detail below. Generally, the second medium A2 described herein is at an ambient pressure equal to an air pressure outside of the aircraft when the aircraft is on the ground and is between an ambient pressure and a cabin pressure when the aircraft is in flight.

The system <NUM> can further receive a third medium A3 at an inlet <NUM>. In one embodiment, the inlet <NUM> is operably coupled to a volume <NUM>, such as the cabin of an aircraft, and the third medium A3 is cabin discharge air, which is air leaving the volume <NUM> and that would typically be discharged overboard. In some embodiments, the system <NUM> is configured to extract work from the third medium A3. In this manner, the pressurized air A3 of the volume <NUM> can be utilized by the system <NUM> to achieve certain operations.

The environmental control system <NUM> includes a RAM air circuit <NUM> having a shell or duct, illustrated schematically in broken lines at <NUM>, within which one or more heat exchangers are located. The shell <NUM> can receive and direct a medium, such as ram air for example, through a portion of the system <NUM>. The one or more heat exchangers are devices built for efficient heat transfer from one medium to another. Examples of the type of heat exchangers that may be used, include, but are not limited to, double pipe, shell and tube, plate, plate and shell, adiabatic shell, plate fin, pillow plate, and fluid heat exchangers.

The one or more heat exchangers arranged within the shell <NUM> may be referred to as ram heat exchangers. In the illustrated, non-limiting embodiment, the ram heat exchangers include a first or primary heat exchanger <NUM> and a second or secondary heat exchanger <NUM>. Although two heat exchangers are illustrated, it should be understood that embodiments including a single heat exchanger, or alternatively, embodiments including more than two heat exchangers are also contemplated herein. Within the heat exchangers <NUM>, <NUM>, ram air, such as outside air for example, acts as a heat sink to cool a medium passing there through, for example the first medium A1 and/or the second medium A2.

The system <NUM> additionally comprises at least one compressing device. In the illustrated, non-limiting embodiments, the system <NUM> includes a first compressing device 40a and a second compressing device 40b. However, embodiments including only a single compressing device, or alternatively, embodiments including more than two compressing devices are also within the scope of the disclosure. Further, as shown, at least a portion of the first compressing device 40a and the second compressing device 40b may be arranged in series relative to a flow of one or more of the mediums, such as the second medium A2 for example, through the system <NUM>. The first and second compressing devices 40a, 40b may, but need not have different configurations and components.

In the illustrated, non-limiting embodiment, the compressing devices 40a, 40b of the system <NUM> are mechanical devices that include components for performing thermodynamic work on a medium (e.g., extracts work from or applies work to the first medium A1, the second medium A2, and/or the third medium A3 by raising and/or lowering pressure and by raising and/or lowering temperature). Examples of each compressing device <NUM> include an air cycle machine, a two-wheel air cycle machine, a three-wheel air cycle machine, a four-wheel air cycle machine, etc..

In the examples not according to the claims of <FIG> and <FIG>, the first compressing device 40a is a two-wheel air cycle machine or turbo machine including a compressor 42a and a turbine 44a operably coupled to each other via a shaft 46a. The compressor 42a is a mechanical device that raises a pressure of a medium and can be driven by another mechanical device (e.g., a motor or a medium via a turbine). Examples of compressor types include centrifugal, diagonal or mixed-flow, axial-flow, reciprocating, ionic liquid piston, rotary screw, rotary vane, scroll, diaphragm, air bubble, etc. As shown, the compressor 42a is configured to receive and pressurize the second medium A2. The turbine 44a is a mechanical device that expands a medium and extracts work therefrom (also referred to as extracting energy) to drive the compressor 42a via the shaft 46a.

In an embodiment, the second compressing device 40b is a four-wheel air cycle machine including a compressor 42b, a turbine 44b, power turbine <NUM>, and a fan <NUM> operably coupled to each other via a shaft 46b. The first turbine 44b and the power turbine <NUM> are operable, independently or in combination, to drive the compressor 42b and the fan <NUM> via the shaft 46b. The fan <NUM> is a mechanical device that can force via push or pull methods a medium (e.g., ram air) through the shell <NUM> across the one or more ram heat exchangers <NUM>, <NUM> and at a variable cooling flow rate to control temperatures. Although the fan <NUM> is illustrated as being part of the four-wheel air cycle machine that forms the second compressing device 40b, in other embodiments, the fan <NUM> may be separate from the compressing device 40b and driven by another suitable means. In such instances, the fan <NUM> may be electrically driven, may be a tip turbine fan, or may be part of a simply cycle machine.

The system <NUM> additionally includes a dehumidification system. In the illustrated, not claimed example of <FIG>, the dehumidification system includes a condenser <NUM> and a water extractor or collector <NUM> arranged downstream from the condenser <NUM>. The condenser <NUM> and the water collector <NUM> are arranged in fluid communication with the second medium A2. The condenser <NUM> is a particular type of heat exchanger and the water collector <NUM> is a mechanical device that performs a process of removing water from a medium. In the not claimed example of <FIG>, the condenser <NUM> of the dehumidification system is illustrated as a separate heat exchanger located downstream from and arranged in fluid communication with an outlet of the second heat exchanger <NUM>. However, the configuration of the at least one dehumidification system may vary.

For example, in the not claimed examples of <FIG> and the embodiment of <FIG>, the condenser <NUM> is formed integrally with the secondary heat exchanger <NUM>. For example, the second medium A2 is configured to flow through a first portion of the heat exchanger that forms the secondary heat exchanger <NUM>, and then through a second, downstream portion of the heat exchange, which forms the condenser <NUM>. In such embodiments, although the entire heat exchanger is arranged within the ram air shell <NUM>, a divider <NUM> wall may extend parallel to the flow of ram air through the shell <NUM> at the interface between the first and second portions of the heat exchanger to separate the ram air shell <NUM> into a distinct first region <NUM> and second region <NUM>. Accordingly, the fan <NUM> of the second compressing device 40b is operable to draw ram air through the first region <NUM>, across the primary heat exchanger <NUM> and the first portion that forms a secondary heat exchanger <NUM>. A fluid flow, distinct from the ram air flow to be described in more detail below, is configured to flow through the second region <NUM>, across the second portion of the heat exchanger that forms the condenser <NUM>. However, it should be understood that embodiments where the secondary heat exchanger <NUM> is arranged within the first region <NUM>, and a condenser <NUM>, separate from and arranged in fluid communication with an outlet of the secondary heat exchanger <NUM>, is arranged within the second region <NUM> are also within the scope of the disclosure.

The elements of the system <NUM> are connected via valves, tubes, pipes, and the like. Valves (e.g., flow regulation device or mass flow valve) are devices that regulate, direct, and/or control a flow of a medium by opening, closing, or partially obstructing various passageways within the tubes, pipes, etc. of the system. Valves can be operated by actuators, such that flow rates of the medium in any portion of the system <NUM> can be regulated to a desired value. For instance, a first valve V1 may be configured to control a supply of the first medium A1 to the system <NUM>, and a second valve may be operable to allow a portion of a medium, such as the first medium A1, to bypass the ram air circuit <NUM>. As a result, operation of the second valve V2 may be used to add heat to the system <NUM> and to drive the compressing device 40a when needed. A third valve V3 may be operable in the event of a pack failure, such as where the system <NUM> does not have a sufficient flow of the second medium A2 to meet the demands of the cabin or other loads. In such instances, operation of valve V3 may be used to supplement the flow of second medium A2 with first medium A1, such as at a location upstream from the dehumidification system for example, to meet the demands of the aircraft.

Operation of a fourth valve V4 may be used to allow a portion of the second medium A2 to bypass the dehumidification system and the turbine 44b of the second compressing device 40b and operation of a fifth valve V5 may be configured to allow a portion of the second medium A2 to bypass the turbine 44b of the second compressing device 40b. In an embodiment, a sixth valve V6 is a surge control valve, operable to exhaust a portion of the second medium A2 output from the compressor 42b of the second compressing device 40b overboard or into the ram air circuit <NUM> to prevent a compressor surge. A seventh valve V7 may be configured to control a supply of a third medium A3 provided to the power turbine <NUM> of the second compressing device 40b.

With continued reference to <FIG> and <FIG>, the system <NUM> is operable in a plurality of modes, selectable based on a flight condition of the aircraft. For example, the system <NUM> may be operable in a first, low altitude mode or a second, high altitude mode. The first, low altitude mode is typically used for ground and low altitude flight conditions, such as ground idle, taxi, take-off, and hold conditions, and the second, high altitude mode may be used at high altitude cruise, climb, and descent flight conditions. During normal operation in both the low altitude mode and the high-altitude mode, only the second medium is provided to one or more loads of the aircraft, including the cabin <NUM>.

In the first, low altitude mode, valve V1 is open, and a high pressure first medium A1, such as bleed air drawn from an engine or APU, is provided to the primary heat exchanger <NUM>. Within the first heat exchanger <NUM>, the first medium A1 is cooled via a flow of ram air, driven by the fan <NUM>. As shown in <FIG>, the cool first medium A1 passes sequentially from the first heat exchanger <NUM> to another heat exchanger <NUM>, where the first medium A1 is further cooled by another medium, distinct from the ram air. In other embodiments, best shown in <FIG>, the heat exchanger <NUM> may be integrally formed with the primary heat exchanger <NUM> and is positioned within the second region <NUM> of the ram air circuit <NUM>.

From the heat exchanger <NUM>, the further cooled first medium A1 is provided to the inlet of the turbine 44a of the first compressing device 40a. The high pressure first medium A1 is expanded across the turbine 44a and work is extracted therefrom. The first medium A1 output from the turbine 44a has a reduced temperature and pressure relative to the first medium A1 provided to the inlet of the turbine 44a. The first medium A1 at the outlet of the turbine 44a may be used to cool the second medium A2 within the condenser <NUM>, to be described in more detail below, and/or to cool the first medium within the heat exchanger <NUM>. This cooling may occur separately from (<FIG>) or within the second region <NUM> of the ram air circuit <NUM> (<FIG>). After receiving heat within heat exchanger <NUM>, the first medium A1 is exhausted overboard. After receiving heat within heat exchanger <NUM>, the first medium A1 may also be exhausted outside the aircraft or may be dumped into a portion of the ram air circuit <NUM>, for example downstream from the heat exchangers therein. In an embodiment, best shown in <FIG>, a wall or barrier <NUM> may be arranged at an upstream end of the second region <NUM> to prevent another medium, separate from the medium output from the first compressing device 40a from passing through the second region <NUM>. Although such a barrier <NUM> is illustrated in <FIG>, it should be understood that any of the embodiments of the ram air system including a separate first and second region <NUM>, <NUM> may include such a barrier <NUM>.

The work extracted form the first medium A1 in the turbine 44a drives the compressor 42a, which is used to compress a second medium A2 provided from an aircraft inlet <NUM>. As shown, the second medium A2, such as fresh air for example, is drawn from an upstream end of the ram air circuit <NUM> or from another source and provided to an inlet of the compressor 42a. The act of compressing the second medium A2 heats the second medium A2 and increases the pressure of the second medium A2. In an embodiment, a configuration of the compressor 42a is selected to increase the pressure of the second medium A2 to less than double its starting pressure.

The second medium A2 output from the compressor 42a of the first compressing device 40a is provided to the compressor 42b of the second compressing device 40b. Within the compressor 42b, the second medium A2 is further heated and pressurized. Accordingly, the second medium A2 is configured to flow through the compressor 42a of the first compressing device 40a and the compressor 42b of the second compressing device 40b in series.

In some embodiments, the compressed second medium A2 output from the compressor 42b is provided to an ozone removal heat exchanger <NUM>, before being provided to the secondary heat exchanger <NUM> where it is cooled by ram air. The second medium A2 exiting the secondary heat exchanger <NUM> is then provided to the condenser <NUM>, where the second medium A2 is further cooled by the first medium A1 output from the turbine 44a of the first compressing device 40a. From the condenser <NUM>, the second medium A2 is provided to the water collector <NUM> where any free moisture is removed, to produce cool medium pressure air. This cool pressurized second medium A2 then enters the turbine 44a where work is extracted from the second medium A2 and used to drive the compressor 42b and the fan <NUM>. The second medium A2 output from the turbine 44b is then sent to one or more loads of the aircraft, such as to condition the volume or cabin <NUM>.

The high-altitude mode of operation is similar to the low altitude mode of operation. However, in some embodiments, valve V2 may be open to allow at least a portion of the first medium A1 to bypass the primary heat exchanger <NUM> and heat exchanger <NUM>. Valve V2 may be operated to control, and in some embodiments, maximize the temperature of the first medium A1 provided to the turbine 44a of the first compressing device. In an embodiment, the pressure ratio across the turbine is less than a conventional turbine. As a result, the work extracted from the first medium A1 within the turbine 44a may be optimized while exhausting the first medium A1 therefrom with a temperature suitable to function as a heat sink with respect to the condenser <NUM> and/or heat exchanger <NUM>.

In the high-altitude mode of operation, the compressor 42a of the first compressing device 40a may be operate to increases the pressure of the second medium A2 up to four times its initial pressure. In addition, the second medium A2 is cooled between the compressor 42a of the first compressing device 40a and the compressor 42b of the second compressing device 40b. Accordingly, the system <NUM> may additionally include at least one outflow heat exchanger <NUM>, such as arranged directly downstream from the outlet of the compressor 42a. The third medium A3, such as exhaust of cabin air for example, is recirculated to the system <NUM> from the pressurized volume or cabin <NUM>, through a valve V7. Within the outflow heat exchanger <NUM>, heat is transferred to the third medium A3 via a heat exchange relationship with the second medium A2, before both mediums are provided to a component of the second compressing device 40b.

In the illustrated, non-limiting embodiment, the third medium A3 output from outflow heat exchanger <NUM> is provided to the power turbine <NUM> of the second compressing device 40b. Within the power turbine <NUM>, the work extracted from the third medium A3 is used to drive the fan <NUM>, and therefore move a flow of ram air through the ram air circuit <NUM>, via rotation of the shaft 46b. In an embodiment, the pressure ratio across the power turbine <NUM> is at least <NUM>:<NUM>. The third medium A3 output from the power turbine <NUM> may be dumped into the ram air circuit <NUM>, downstream from all heat exchangers, or alternatively, may be dumped overboard.

The second medium A2 output from the outflow heat exchanger <NUM> is provided to the compressor 42b of the second compressing device 40b and from there may follow the same flow path with respect to the secondary heat exchanger <NUM> and condenser <NUM> as previously described for the low altitude mode of operation. In an embodiment, valve V5 is open in the high-altitude mode. As a result, at least a portion of the second medium A2 output from the condenser <NUM> bypasses the turbine 44b of the second compressing device 40b.

Depending on the temperature and humidity conditions of the day, the second medium output from the condenser <NUM> may be too cold to provide directly to the cabin <NUM>, via valve V5. In such instances, during the high altitude mode of operation, valve V4 is opened, thereby allowing a portion of the heated second medium A2 output from the compressor 42b of the second compressing device 40b to mix with the cold second medium A2 upstream from an outlet of the system <NUM>. Accordingly, valve V4 can be controlled to achieve a second medium A2 having a desired temperature for conditioning the cabin <NUM>.

With reference now to <FIG>, another configuration of the system <NUM> is illustrated. The system <NUM> is similar to the configuration of <FIG>; however, in the illustrated, non-limiting embodiment, the first compressing device 40a includes not only a compressor 42a and first turbine 44a, but also a second turbine 48a. Further, the flow of the first medium A1 output from the heat exchanger <NUM>, is configured to flow through the first turbine 44a and the second turbine 48a in series. By providing the first medium A1 to the first and second turbine 44a, 48a in series, the total amount of work extracted therefrom can be maximized while limiting the pressure ratios required at each turbine 44a, 48a. Similarly, by providing the first medium A1 to the first and second turbine 44a, 48a in parallel, the temperature and pressure of the first medium used as a heat sink for the condenser <NUM> and the heat exchanger <NUM> may be controlled. Alternatively, in embodiments where valve V8 is open, the first medium A1 output from the heat exchanger <NUM> may be configured to bypass the first turbine 44a. In such embodiments, substantially all of the first medium A1 output from the heat exchanger <NUM> is provided directly to the second turbine 48a.

In an embodiment, the pressure ratio of one or more of the turbines of the first compressing device 40a is reduced relative to existing turbines. As used herein, the term "pressure ratio" is intended to describe the ratio of the pressure of the medium provided to an inlet of the turbine and the pressure of the medium provided at the outlet of the turbine. In an embodiment, such as embodiments of the system <NUM> including a plurality of turbines 44a, <NUM> arranged in series relative to a flow of one or more mediums, the pressure ratio of each of the turbines may be reduced compared to conventional turbines. By using a plurality of turbines having a reduced pressure ratio in series, the energy extracted from the medium within the turbines may be maximized.

Yet another configuration of the system <NUM> is illustrated in the non-limiting embodiment of <FIG>. As shown, the system <NUM> is substantially similar to the configuration of the system illustrated and described with respect to <FIG>; however, the first compressing device 40a includes two compressors 42a1 and 42a2, arranged in parallel relative to a flow of the second medium A2 provided via the inlet <NUM>. In such embodiments, the first and second compressors 42a1, 42a2 may be substantially identical. By providing two compressors 42a1, 42a2 in parallel, the total volume of the second medium A2 to be compressed within each device is reduced.

Claim 1:
An environmental control system of an aircraft comprising:
a plurality of inlets (<NUM>, <NUM>, <NUM>) for receiving a plurality of mediums including a first medium (A1) and a second medium (A2);
an outlet for delivering a conditioned flow of the second medium to one or more loads of the aircraft;
a ram air circuit (<NUM>) including a ram air shell (<NUM>) having at least one ram air heat exchanger (<NUM>, <NUM>) positioned therein;
a compressing device (<NUM>) arranged in fluid communication with the ram air circuit and the outlet, the compressing device including a first compressor (40a), a second compressor (40b), and at least one turbine (<NUM>) operably coupled via a shaft (<NUM>), the first compressor and the second compressor being arranged in parallel with respect to a flow of the second medium and wherein the first medium output from the compressing device is used as a heat sink by another component within the environmental control system;
characterized in that the at least one turbine (<NUM>) includes a first turbine (44a) and a second turbine (48a) arranged in series relative to a flow of the first medium (A1); further in that the first medium output from the another component is exhausted overboard.