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> relates to an environmental control system for an aircraft.

An environmental control system of an aircraft according to claim <NUM> is provided. Preferred embodiments are provided in the dependent claims.

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 the figures, various schematic diagrams of a portion of an environment control system (ECS) <NUM>, such as an air conditioning unit or pack for example, is depicted according to non-limiting embodiments. As shown in the figures, the system <NUM> can receive a first medium A1 at a first inlet <NUM>. The first medium A1 is 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 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. 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> including 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 ram air 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>. 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.

A fan <NUM> is a mechanical device that can force via push or pull methods a medium, such as ram air for example, through the shell <NUM> across the one or more ram heat exchangers <NUM>, <NUM> at a variable cooling flow rate to control temperatures. As shown, the fan <NUM> is a separate component driven by any suitable means. Examples of such a fan include an electrically driven fan, a tip turbine fan, or a fan that is part of a simple cycle machine. However, in other embodiments, the fan <NUM> may part of a compression device <NUM> to be described in more detail below.

The system <NUM> additionally includes a compression device <NUM>. In the illustrated, non-limiting embodiment, the compression device <NUM> is a mechanical device that includes 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 a compression 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 environmental control systems of <FIG>, the compression device <NUM> is a four-wheel air cycle machine including a compressor <NUM> and a plurality of turbines. The compressor <NUM> is a mechanical device configured to raise 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 <NUM> is configured to receive and pressurize the second medium A2.

In the illustrated example, the compression device <NUM> includes a turbine <NUM>, such as a fresh air turbine, a bleed turbine <NUM>, and a power turbine <NUM> operably coupled to each other and the compressor <NUM> via a shaft <NUM>. The turbines <NUM>, <NUM>, and <NUM> are mechanical devices that expand a medium and extract work therefrom (also referred to as extracting energy) to drive the compressor <NUM> via the shaft <NUM>. The turbines <NUM>, <NUM>, and <NUM> are operable independently or in combination, to drive the compressor <NUM> via the shaft <NUM>.

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> may be 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 non-limiting embodiment of <FIG>, <FIG>, and <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.

In the non-limiting embodiments of <FIG>, <FIG>, and <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, and then through a second, downstream portion of the heat exchanger, which forms the condenser. In such embodiments, although the entire heat exchanger is arranged within the ram air shell <NUM>, a divider <NUM> wall extends 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> is positioned to draw ram air through only 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>. In such a configuration, the ram air arranged within the first region <NUM> and the fluid flow provided to the second region <NUM> do not mix within the ram air shell <NUM>.

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 compression device <NUM> 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 <NUM> of the compression device <NUM> and operation of a fifth valve V5 may be configured to allow a portion of the second medium A2 output from the dehumidification system to bypass the turbine <NUM> of the compression device <NUM>. 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 <NUM> overboard or into the ram air circuit <NUM> to prevent a compressor surge. In an embodiment, a seventh valve V7 is configured to control a supply of a medium, such as the first medium A1 for example, to the fan <NUM>, to drive operation of the fan <NUM>. A valve V8 may be configured to control a supply of the third medium A3 to the system <NUM>,.

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.

In the first, low altitude mode, valve V1 and V7 are 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> and to the fan <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 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 embodiments, best shown in <FIG>, the heat exchanger <NUM> may be integrally formed with the heat exchanger that functions as 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 bleed turbine <NUM>. The high pressure first medium A1 is expanded across the bleed turbine <NUM> and work is extracted therefrom. The first medium A1 output from the bleed turbine <NUM> has a reduced temperature and pressure relative to the first medium A1 provided to the inlet of the bleed turbine <NUM>. The first medium A1 at the outlet of the bleed turbine <NUM> 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 A1 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 from the first medium A1 within heat exchanger <NUM>, the first medium A1 may be exhausted overboard or outside the aircraft, or to a portion of the ram air circuit <NUM>, such as downstream from all of the heat exchangers arranged 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 compressing device <NUM> 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 bleed turbine <NUM>, drives the compressor <NUM>, 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 <NUM>. The act of compressing the second medium A2, heats the second medium A2 and increases the pressure of the second medium A2.

In some embodiments, the compressed second medium A2 output from the compressor <NUM> 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. In the illustrated, non-limiting embodiment, the first medium A1 and the second medium A2 are configured to flow through the primary and second heat exchangers <NUM>, <NUM>, respectively, in the same direction relative to the ram air flow. However, embodiments where the first and second medium flow in different directions are also within the scope of the disclosure.

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 bleed turbine <NUM>. 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 <NUM> where work is extracted from the second medium A2 and used to drive the compressor <NUM>. The second medium output from the turbine <NUM> is then sent to one or more loads of the aircraft, such as to condition the pressurized 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 bleed turbine <NUM>. As a result, the work extracted from the first medium A1 within the bleed turbine <NUM> 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 third medium A3, such as an exhaust of cabin air for example, is recirculated to the system <NUM> from the pressurized volume <NUM>, through valve V8. The flow of the third medium A3 may be provided directly to an inlet of the power turbine <NUM>. The additional work extracted from the third medium A3 in the power turbine <NUM>, is used in combination with the work extracted from the first medium A1 to drive the compressor <NUM>. As shown, the third medium A3 may be mixed at a mixing point MP1 with the first medium A1. In the illustrated, non-limiting embodiment, the mixing point is located downstream from an outlet of the bleed turbine <NUM> and the power turbine <NUM>. In the high altitude mode of operation, this mixture of first medium and third medium A1+A3 may be used to cool the second medium A2 within the condenser <NUM>, and/or to cool the first medium A1 within the heat exchanger <NUM>, and then dumped overboard or into the ram air circuit <NUM>.

The compressed second medium A2 output from the compressor <NUM> may follow the same flow path with respect to the secondary heat exchanger <NUM> and condenser <NUM>, water collector <NUM>, and turbine <NUM> as previously described for the low altitude mode of operation. However, 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 <NUM> of the compression device.

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 <NUM> 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> and <FIG>, another configuration of the system <NUM> is illustrated. The system <NUM> is similar to the configuration of <FIG> and <FIG>; however, in the illustrated, non-limiting embodiment, the compression device <NUM> includes a second bleed turbine 46b in place of the power turbine <NUM>. Accordingly, during both the low altitude and high-altitude modes of operation, the first medium A1 is provided to the first bleed turbine 46a then to the second bleed turbine 46b sequentially. The work extracted from the first medium A1 in both bleed turbines 46a, 46b is used to drive the compressor. Further, the first medium A1 output from the second bleed turbine 46b is used to cool the flows of medium within the condenser <NUM> and/or the heat exchanger <NUM>. As previously described, in a high-altitude mode of operation, the third medium A3 is additionally provided to the system <NUM> and work is extracted therefrom. As shown, the third medium A3 is mixed at a mixing point MP2 with the first medium A1. In the illustrated, non-limiting embodiment, the mixing point MP2 is located downstream from an outlet of the first bleed turbine 46a and upstream from an inlet of the second bleed turbine 46b. By mixing the plurality of mediums within the air cycle machine, the complexity of the housing of the compressing device 40a is reduced since only a single outlet for both the first medium and the third medium is formed therein.

In an embodiment, the pressure ratio of one or more of the turbines of the compressing device <NUM> 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 46a, 46b 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.

Yet another configuration of the system <NUM> is illustrated in the environmental control systems of <FIG> and <FIG>. As shown, the system <NUM> is substantially similar to the previous configurations. However, the compression device <NUM> of the system <NUM> of <FIG> and <FIG> includes a dual entry turbine <NUM> in place of the power turbine or the second bleed turbine. As shown, the dual entry turbine <NUM> is configured to receive flows of different mediums. A dual entry turbine typically has multiple nozzles, each of which is configured to receive a distinct flow of medium at a different entry point, such that multiple flows can be received simultaneously. For example, the turbine <NUM> can include a plurality of inlet flow paths, such as an inner flow path and an outer flow path, to enable mixing of the medium flows at the exit of the turbine <NUM>. The inner flow path can be a first diameter, and the outer flow path can be a second diameter. Further, the inner flow path can align with one of the first or second nozzles, and the outer flow path can align with the other of the first or second nozzles.

In an embodiment, one of the inlets or nozzles of the dual entry turbine <NUM> is arranged downstream from and in series with an outlet of the bleed turbine <NUM>. Accordingly, during both the low altitude and high-altitude modes of operation, the first medium A1 is provided to bleed turbine <NUM> then to the dual entry turbine <NUM> sequentially. The work extracted from the first medium A1 in both the bleed turbine <NUM> and the dual entry turbine <NUM> is used to drive the compressor. Further, the first medium A1 output from the second bleed turbine 46b is used to cool the flows of medium within the condenser <NUM> and/or the heat exchanger <NUM>. As previously described, in a high-altitude mode of operation, the third medium A3 is additionally provided to the system <NUM> and work is extracted therefrom. As shown, the third medium A3 may be provided to a second inlet or nozzle of the dual entry turbine <NUM>. In such embodiments, the mixing point MP3 of the third medium A3 and the first medium A1 can be at the dual entry turbine <NUM>, such as at an outlet of the turbine <NUM> for example, or alternatively, may be downstream therefrom.

Claim 1:
An environmental control system of an aircraft comprising:
a ram air circuit (<NUM>) including:
a ram air shell (<NUM>) having at least one heat exchanger (<NUM>, <NUM>) positioned therein;
a divider (<NUM>) arranged within the ram air shell to separate the ram air shell into a first region (<NUM>) and a second region (<NUM>), the at least one heat exchanger being arranged within both the first region and the second region, wherein the system is configured such that ram air flows through the first region and such that in a low altitude mode of operation a first medium (A1) and in a high altitude mode of operation a combination of the first medium (A1) and a third medium (A3) flows through the second region;
a dehumidification system (<NUM>, <NUM>) arranged in fluid communication with the ram air circuit; and
a compression device (<NUM>) arranged in fluid communication with the ram air circuit and the dehumidification system, the compression device including a compressor (<NUM>) and a turbine (<NUM>);
wherein the system is configured such that the first medium or the combination of the first and third media that flow through the second region is exhausted from the turbine of the compression device;
wherein the at least one heat exchanger (<NUM>, <NUM>) includes a first portion arranged within the first region (<NUM>) and a second portion arranged within the second region (<NUM>), the second portion of the at least one heat exchanger is integrally formed with the first portion; and
wherein the system is configured such that the first medium or the combination of the first medium and the third medium that flow through the second region flows across the second portion of the at least one heat exchanger.