Environmental control system utilizing a motor assist and an enhanced compressor

A system includes a first inlet providing a medium from a source and a compressing device arranged in communication with the first inlet. The compressing device includes a compressor configured to receive the medium and a turbine located downstream from the compressor. The system additionally includes at least one heat exchanger and an electric motor operably coupled to the compressor. The system is powered by mechanical power from the medium and by electrical power from the electric motor. The input power of the electric motor is less than or equal to 0.5 kilowatts per pounds per minute of medium compressed.

BACKGROUND

In general, with respect to present air conditioning systems of aircraft, cabin pressurization and cooling is powered by engine bleed pressures at cruise. For example, pressurized air from an engine of the aircraft is provided to a cabin through a series of systems that alter the temperatures and pressures of the pressurized air. To power this preparation of the pressurized air, the only source of energy is the pressure of the air itself. As a result, the present air conditioning systems have always required relatively high pressures at cruise. Unfortunately, in view of an overarching trend in the aerospace industry towards more efficient aircraft, the relatively high pressures provide limited efficiency with respect to engine fuel burn.

SUMMARY

According to one embodiment, a system is provided. The system includes a first inlet providing a medium from a source; a compressing device in communication with the first inlet; and at least one heat exchanger. The compressing device includes a compressor that receives the medium and a turbine downstream of the compressor. The system is powered by mechanical power from the medium and by electrical power through a motor. The motor input power is less than or equal to 0.5 kilowatt per pounds per minute of the medium compressed.

Additional features and advantages are realized through the techniques of the embodiments herein. Other embodiments and aspects thereof are described in detail herein and are considered a part of the claims. For a better understanding of the embodiments with the advantages and the features, refer to the description and to the drawings.

DETAILED DESCRIPTION

Embodiments herein provide an environmental control system that utilizes bleed pressures to power the environmental control system and to provide cabin pressurization and cooling at a high engine fuel burn efficiency, along with including a motor to assist with compression operations of the environmental control system.

In general, embodiments of the environmental control system may include one or more heat exchangers and a compressing device. A medium, bled from a low-pressure location of an engine, flows through the one or more heat exchangers into a chamber. Turning now toFIG. 1, a system100that receives a medium from an inlet101and provides a conditioned form of the medium to a chamber102is illustrated. The system100comprises a compressing device120and a heat exchanger130. The elements of the system are connected via valves, tubes, pipes, and the like. Valves 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 system100. Valves can be operated by actuators, such that flow rates of the medium in any portion of the system100can be regulated to a desired value.

As shown inFIG. 1, a medium can flow from an inlet101through the system100to a chamber102, as indicated by solid-lined arrows A, B. In the system100, the medium can flow through the compressing device120, through the heat exchanger130, from the compressing device120to the heat exchanger130, from the heat exchanger130to the compressing device120, etc.

The medium, in general, can be air, while other examples include gases, liquids, fluidized solids, or slurries. When the medium is being provided by an engine connected to the system100, such as from the inlet101, the medium can be referred to herein as bleed air. With respect to bleed air, a low-pressure location of the engine (or an auxiliary power unit) can be utilized to provide the medium at an initial pressure level near a pressure of the medium once it is in the chamber102(e.g., chamber pressure).

For instance, continuing with the aircraft example above, air can be supplied to the environmental control system by being “bled” from a compressor stage of a turbine engine. The temperature, humidity, and pressure of this bleed air varies widely depending upon a compressor stage and a revolutions per minute of the turbine engine. Since a low-pressure location of the engine is utilized, the medium may be slightly above or slightly below the pressure in the chamber102. Bleeding the medium at such a low pressure from the low-pressure location causes less of a fuel burn than bleeding air from a higher pressure location. Yet, because the medium is starting at this relatively low initial pressure level and because a drop in pressure occurs over the one or more heat exchangers, the medium may drop below the chamber pressure while the medium is flowing through the heat exchanger130. When the pressure of the medium is below the chamber pressure, the medium will not flow into the chamber to provide pressurization and temperature conditioning.

To achieve the desired pressure, the bleed-air can be compressed as it is passed through the compressing device120. The compressing device120is a mechanical device that controls and manipulates the medium (e.g., increasing the pressure of bleed air). Examples of a compressing device120include an air cycle machine, a three-wheel machine, a four wheel-machine, etc. The compressing can include a compressor, such as a centrifugal, a diagonal or mixed-flow, axial-flow, reciprocating, ionic liquid piston, rotary screw, rotary vane, scroll, diaphragm, air bubble compressors, etc. Further, compressors can be driven by a motor or the medium (e.g., bleed air, chamber discharge air, and/or recirculation air) via a turbine.

The heat exchanger130is a device built for efficient heat transfer from one medium to another. Examples of heat exchangers include double pipe, shell and tube, plate, plate and shell, adiabatic wheel, plate fin, pillow plate, and fluid heat exchangers. In an embodiment, air forced by a fan (e.g., via push or pull methods) can be blown across the heat exchanger at a variable cooling airflow to control a final air temperature of the bleed air.

The system100ofFIG. 1will now be described with reference toFIG. 2, in view of the aircraft example.FIG. 2depicts a schematic of a system200(e.g., an embodiment of system100) with a motor assist as it could be installed on an aircraft. The system200is an example of an environmental control system of an aircraft that provides air supply, thermal control, and cabin pressurization for the crew and passengers of the aircraft. The system200can be driven by a medium, e.g., by receiving bleed air at a bleed pressure at approximately 40 psia on the ground and as low as 2 psia below cabin pressure at the compressor inlet at cruise.

The system200illustrates the bleed air flowing in at inlet201(e.g., off an engine of an aircraft or auxiliary power unit at an initial flow rate, pressure, temperature, and humidity), which in turn is provided to a chamber202(e.g., cabin, flight deck, etc.) at a final flow rate, pressure, temperature, and humidity. The system includes a shell210for receiving and directing ram air through the system200. Note that based on the embodiment, an exhaust from the system200can be sent to an outlet (e.g., releases to ambient air through the shell210). Note also that the system200is designed to work with bleed pressures near a pressure of the chamber202(e.g., cabin pressure or chamber pressure) during cruise.

The system200further illustrates valves V1-V3, at least one heat exchanger220, an air cycle machine240(that includes a turbine243, a compressor244, a motor247, a fan248, and a shaft249), a reheater250, a condenser260, and a water extractor270, each of which is connected via tubes, pipes, and the like. Note that the at least one heat exchanger220is an example of the heat exchanger130as described above. Further, in an embodiment, the at least one heat exchanger can be a secondary heat exchanger downstream of a primary heat exchanger (not shown). Note also that the air cycle machine240is an example of the compressing device120as described above.

The air cycle machine240controls/regulates a temperature, a humidity, and a pressure of a medium (e.g., increasing the pressure of a bleed air). The turbine243is a mechanical device that drives the compressor244and the fan248via the shaft249. The compressor244is a mechanical device that raises the pressure of the bleed-air received from the first heat exchanger.

The motor247is a mechanical/electrical device that can also drive the compressor244and the fan248via the shaft249. The motor247can be mounted on an air cycle machine (or the air cycle machine includes an additional electrical motor driven compressor). Note that in a conventional environmental control system, an electrical motor can be used to boost the pressure when the bleed pressure entering the conventional environmental control system is less a cabin pressure (e.g., as much as 5 psi below the cabin pressure). The amount of power utilized by this electrical motor of the conventional environmental control system is significant, since the air entering the pressurization system can be as low as 5 psi below cabin pressure. In contrast to the electrical motor of the conventional environmental control system, the247motor is significantly lower in power. The motor247provides assistance as needed, due to the system200being configured to receive the medium at equal to or within 2.5 psi of the chamber pressure at an inlet of the compressor240. In this way, the system200avoids the above noted power challenges, along with challenges pertaining to liquid cooling of high power motor drives not discussed herein, of the conventional environmental control system. Further, the system200can utilize an electrical sub-system at a constant or a variable frequency to power the motor247.

The fan248is a mechanical device that can force via push or pull methods air through the shell210across the secondary heat exchanger220at a variable cooling airflow. Thus, the turbine243, the compressor244, and the fan248together illustrate, for example, that the air cycle machine240may operate as a three-wheel air cycle machine that utilizes air recirculated from the chamber202.

The reheater250and the condenser260are particular types of heat exchanger. The water extractor270is a mechanical device that performs a process of taking water from any source, such as bleed-air, either temporarily or permanently. Together, reheater250, the condenser260, and/or the water extractor270can combine to be a high pressure water separator.

An operation of the system will now be described with respect to a high pressure mode. During the high pressure mode, high-pressure high-temperature air from the inlet201via the valve V1enters the compressor244of the air cycle machine240. The compressor244further pressurizes the air and in the process heats it. The air then enters the at least one exchanger220, where it is cooled by ram air to approximately ambient temperature to produce cool high pressure air. This cool high pressure air enters the high pressure water separator, where the air goes through the reheater250, where it is cooled; the condenser260, where it is cooled by air from the turbine243of the air cycle machine240; the water extractor270, where the moisture in the air is removed; and the reheater250, where the air is heated back to nearly the same temperature it started at when it entered the high pressure water separator. The warm high pressure and now dry air enters the turbine243, where it is expanded and work extracted. The work from the turbine243, drives both the compressor244and the fan248that is used to pull a ram air flow through the at least one exchanger220. After leaving the turbine243, the cold air, typically below freezing, cools the warm moist air in the condenser260. After the air leaves the condenser260, it is sent to condition the chamber202.

The high pressure mode of operation can be used at flight conditions when engine pressure is adequate to drive the cycle or when a temperature of the chamber202demands it. For example, conditions, such as ground idle, taxi, take-off, climb, descent, and hold conditions would have the air cycle machine240operating in the high pressure mode. In addition, extreme temperature high altitude cruise conditions could result in the air cycle machine240operating in the high pressure mode.

Note that when operating in the high pressure mode, it is possible for the air leaving the compressor244to exceed an auto-ignition temperature of fuel (e.g., 400 F for steady state and 450 F for transient). In this situation, air from the outlet of the heat exchanger220is ducted by the valve V2to the inlet of the compressor244. This lowers inlet temperature of the air entering the inlet of the compressor244and now, as a result, the air leaving the compressor244is below the auto-ignition temperature of fuel.

An operation of the system will now be described with respect to a low pressure mode. During the low pressure mode, the air from the inlet201via the valve V1enters the compressor244. The compressor244further pressurizes the air and in the process heats it. The air then enters the at least one exchanger220, where it is cooled by ram air to a temperature requested by the chamber202. The air then goes directly into the chamber202via valve V3.

The low pressure mode can be used at flight conditions where the pressure of the bleed air entering the air cycle machine240is greater than approximately 1 psi above the chamber pressure and/or where the pressure of the bleed air entering the air cycle machine240is as low as 2.5 psi below the chamber pressure (e.g., conditions at cruise where altitudes are above 30,000 ft. and conditions at or near standard ambient day types). In this mode the compressor244would have a pressure ratio of approximately 1.4 to 1. The system200capitalizes on the low pressure ratio be enabling a power utilized by the motor247to be significantly deceased. For example, the system can utilize a motor that utilize 0.5 kilowatts per pound per minute of air compressed, which is less than half the power required by the conventional environmental control system. By utilizing the motor247, the system200avoids a need for liquid cooling systems used to cool the high power electronics, such as the conventional electric motor.

In addition, the system200can further utilize an enhanced compressor as the compressor244to address compressor range concerns during operations of the system200. That is, the system200implements a corrected flow range that exceeds a corrected range flow of a centrifugal compressor of the conventional environmental control system. For instance, embodiments herein provide an environmental control system that utilizes bleed pressures to power the environmental control system and to provide cabin pressurization and cooling at a high engine fuel burn efficiency, along with including the enhanced compressor that has high efficiency over a much wider corrected flow and pressure ratio range than the conventional centrifugal compressor. The enhanced compressor can include one or more of a compressor with high rotor backsweep, shroud bleed, and a low solidity diffuser; a variable vaned diffuser, and a mixed flow compressor. The enhanced compressor will now be described with respect toFIGS. 3-6.

FIG. 3is a diagram of schematics of diffusers of a compressing device according to an embodiment.FIG. 3illustrates a plurality of diffusers, a schematic310of a low solidity diffuser, a schematic320of a curved channel diffusor, and a schematic330of a variable vaned diffuser. A diffuser converts the dynamic pressure of the medium flowing downstream of the rotor into static pressure rise by gradually slowing/diffusing a velocity of the medium (e.g., increases static pressure leaving the rotor). The diffuser can be vaneless, vaned or an alternating combination. As different diffuser types impact range and efficiency of the compressor244of the air cycle machine240, one these diffusers310,320, and330can be utilized within the compressor244(e.g., at position606described below with respect toFIG. 6). The low solidity diffuser has a smaller number of vanes and provides a wide operating range with a lower efficiency. The curved channel diffuser extends arches each of the vanes and provides a narrow operating range with a high efficiency. The variable vaned diffuser comprises a plurality of vanes, each of which is configured to rotate about a pin as an articulating member moves the plurality of vanes, and provides a very high operating range with a high efficiency. Further, a single diffuser that has a combination of two or more of the diffusers310,320, and330can also be utilized.

Turning now toFIGS. 4-5, the enhanced compressor will now be described with respect to the compressor244including a high rotor backsweep with shroud bleed and a low solidity diffuser.

FIG. 4is a diagram of schematics of a compressor rotor backsweep according to an embodiment.FIG. 4illustrates a first rotor400, with a plurality of blades402, according to an embodiment. As illustrated, a reference line404extends radially from a center of the rotor400. A dotted-line406tracks a direction of the rotor blade402, if the rotor blade402were to be extended from a circumferential edge of the rotor400. As shown, the direction of the rotor blade402(e.g., dotted-line406) is in parallel with the reference line404, which indicates no rotor backsweep.

FIG. 4also illustrates a high rotor backsweep450, with a plurality of blades452, according to an embodiment. As illustrated, a reference line454extends radially from a center of the rotor450. A dotted-line456tracks a direction of the rotor blade452, if the rotor blade452were to be extended from a circumferential edge of the rotor450. As shown, the direction of the rotor blade452(e.g., dotted-line456) is not in parallel with the reference line454, which indicates a rotor backsweep. The backsweep can be predetermined during manufacturing of the rotor, and can range from 0° to 90°. Embodiments of the backsweep include, but are not limited to, 0°, 30°, 42°, 45°, and 52°.

FIG. 5illustrates a shroud bleed placement diagram500, which includes a plurality of demarcations and lines overlaying a greyed-out view of a portion of a rotor, according to an embodiment. As shown, rotor blades or impeller blades502(e.g., impeller blades502.1and502.2) bound a flow path. From a shroud tip503of the impeller blade502.1(i.e., an impeller blade leading edge) to a shroud suction surface504of the impeller blade502.2a throat505of the flow path is formed. At a location where the throat505contacts the shroud suction surface504of the impeller blade502.2, a plane516is formed. The plane516is perpendicular to an axis of rotation517of the rotor itself. The plane516can be utilized to offset521a shroud bleed523. In an embodiment, the offset521can be selected from a range, such as a range from 0 to 0.90 inches.

The shroud bleed523can be an opening for allowing a portion of a medium in the flow path to bleed out of or into the flow path instead of exiting the rotor. The shroud bleed523can be a circumferentially located on a housing of the rotor. The shroud bleed523can comprise one or more openings, each of which can be segmented at fixed or varying intervals, lengths, and/or patterns, to accommodate different bleed rates. The shroud bleed523can be holes, slots, cuts, etc. The shroud bleed523can be defined by an area, such as a total open area that is a percentage, e.g., 0 to 50% of a total rotor inlet throat area524. The total rotor inlet throat area524is defined by the area524between each pair of impeller blades502.

FIG. 6is a diagram of schematics of a mixed flow channel according to an embodiment.FIG. 6illustrates a cross section view600of the compressor244. As shown in the cross section view600, the compressor244comprises an inlet602and an outlet604, which define a flow path. That is, the flow path between the inlet602and the outlet604is the mixed flow channel. The mixed flow channel can house a diffuser at position606and a rotor at position608. A shape of the mixed flow channel can be selected to be between a range of a channel610.1to a channel610.2. For instance, the channel610.1is a straight flow path, where a flow of a medium through the channel610.1is parallel to an axis of rotation of the rotor. Further, the channel610.2is a bent flow path, where the flow of the medium through the channel610.2begins at inlet602in parallel with the axis of rotation of the rotor and ends at outlet604perpendicular to the axis of rotation of the rotor.

In view of the above, embodiments herein can include a hybrid electric and bleed system for a vehicle or pressure vessel. The hybrid electric and bleed system can comprise an environmental control system having a pressurization circuit and a cooling circuit. The pressurization circuit provides air near cabin pressure. The cooling circuit rejects heat and water from air outside the pressure vessel. The environmental control system can be configured to be powered by mechanical power from pressurized bleed air and/or by electrical power through an electric motor. The environmental control system can include a compressor mechanically attached to a turbine, where the compressor has high rotor backsweep with shroud bleed and a low solidity diffuser, utilizes a variable vaned diffuser, and/or utilizes a mixed flow compressor.

Aspects of the embodiments are described herein with reference to flowchart illustrations, schematics, and/or block diagrams of methods, apparatus, and/or systems according to embodiments. Further, the descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments 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 described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

The flow diagrams depicted herein are just one example. There may be many variations to this diagram or the steps (or operations) described therein without departing from the spirit of embodiments herein. For instance, the steps may be performed in a differing order or steps may be added, deleted or modified. All of these variations are considered a part of the claims.