Patent Description:
Aircraft, such as commercial airliners, typically include multiple gas turbine engines configured to generate thrust. The gas turbine engines include a compressor section that compresses air, a combustor section that mixes the air with a fuel and ignites the mixture, and a turbine section across which the resultant combustion products are expanded.

As the compressor section draws in atmospheric air and compresses it, the air from the compressor section is suitable for provision to the environmental control system (ECS) of the aircraft. The ECS system supplies air for various applications on the aircraft. As an example, it supplies conditioned cabin air for the passenger cabin and the cockpit. As such, it must be a particular pressure and temperature.

In existing ECS configurations, air is bled from the compressor section at a temperature and a pressure in excess of the temperature and pressure required by the ECS and is conditioned to reduced temperature using a pre-cooler and to reduced pressure using a pressure regulating valve. In this manner, pressure in excess of that required by the ECS is dumped across the pressure regulating valve. The excess pressure dump results in an overall efficiency loss to the engine.

As part of the typical ECS system, the air downstream of the gas turbine engine is passed through an air cycle machine. In an air cycle machine, the compressed air tapped from the engine compressor is typically cooled by ram air, compressed to high pressure and temperature, cooled to low temperature and high pressure again by ram air, and expanded across a turbine (which drives the air cycle compressor) to create cold air at cabin pressure. Thus the air cycle machine requires only a moderate pressure to operate (as air is further compressed in the machine), while the engine bleed pressure can be well in excess of moderate pressure in many operation points.

Of course, during operation of a gas turbine engine during flight condition, the power supplied by the engine changes dramatically. In prior art systems, operating at high power, the air is at an undesirably high pressure. On the other hand, at certain low power conditions, the air from any one tap might be at an undesirably low pressure.

As such, the prior art has not been efficient.

It is well known that fuel efficiency is a driving force in modem aircraft engine design. The increase of even a small percent of fuel burn efficiency is a very valuable goal.

<CIT> discloses a prior art environmental control system supply precooler bypass.

<CIT> discloses a prior art engine bleed supply with a low pressure environmental control system.

According to an aspect of the invention, there is provided a system for use on a turbine engine powered aircraft to provide conditioned air to an environmental control system, as claimed in claim <NUM>. Embodiments of this aspect of the invention are as claimed in the dependent claims thereof.

These and other features can be best understood from the following specification and drawings, of which the following is a brief description.

In one disclosed embodiment, the engine <NUM> bypass ratio is greater than about ten (<NUM>:<NUM>), the fan diameter is significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> has a pressure ratio that is greater than about five (<NUM>:<NUM>). The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>.

The fan section <NUM> of the engine <NUM> is designed for a particular flight condition -- typically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM> meters). The flight condition of <NUM> Mach and <NUM>,<NUM> ft (<NUM>), with the engine at its best fuel consumption - also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')" - is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. "Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]^<NUM>. The "Low corrected fan tip speed" as disclosed herein according to one non-limiting embodiment is less than about <NUM> ft / second (<NUM>/s).

In order to provide air from the compressor section <NUM> to the aircraft environmental control system (ECS), multiple bleeds are incorporated in the compressor section <NUM> (illustrated schematically in <FIG>). Each of the bleeds withdraws air from the compressor section <NUM> at a given compressor stage according to known aircraft bleed techniques and using known bleed apparatuses. Contemporary aircraft systems for providing air to an ECS bleed air from a stage sufficiently pressurized to meet a required flow rate of the ECS. Bleeding at these stages, however, necessitates bleeding air at a pressure that is in excess of a maximum allowable temperature for the ECS. In order to reduce the temperature, a pre-cooler heat exchanger is positioned in the air circuit and reduces the temperature of the bleed air before the bleed air is provided to the ECS. Upstream of the ECS, the excess pressure is dumped such as by a pressure regulating valve, resulting in air provided that meets the temperature, pressure and flow requirements. Pressurization of the air passing through the compressor section <NUM> requires energy, and the provision of excess pressure to the ECS constitutes waste, and decreases the efficiency at which the engine <NUM> can be operated.

<FIG> schematically illustrates an aircraft <NUM>, including an electro-pneumatic ECS air circuit <NUM> that reduces the inefficiencies associated with providing air from the engine compressor to an ECS. The electro-pneumatic ECS air circuit <NUM> includes multiple bleeds <NUM>, <NUM>, <NUM>, <NUM> within a compressor section <NUM> of an engine <NUM>. Each of the bleeds <NUM>, <NUM>, <NUM>, <NUM> is connected to an intercooler <NUM> via a selection valve <NUM>. The intercooler <NUM> operates as a heat exchanger to cool the bleed air. In the exemplary illustration, the bleeds <NUM>, <NUM>, <NUM>, <NUM> are positioned at an inter-compressor stage between a low pressure compressor 122a, and a high pressure compressor 122b (bleed <NUM>), and at a high pressure compressor 122b third stage (bleed <NUM>), <NUM>th stage (bleed <NUM>), and <NUM>th stage (bleed <NUM>). In alternative example engines, the bleed locations can be positioned at, or between, alternative compressor stages, depending on the specific flow, temperature, and pressure requirements of the aircraft incorporating the engine <NUM>. In yet further alternative example engines <NUM>, alternative numbers of bleeds can be utilized depending on the specific requirements of the aircraft.

An aircraft controller <NUM> controls a selection valve <NUM> such that, at any given time, air is provided from a bleed <NUM>, <NUM>, <NUM>, <NUM> having the appropriate flow requirements of the ECS at the current operating conditions of the aircraft. While the bleed <NUM>, <NUM>, <NUM>, <NUM> selected by the controller <NUM> provides air at acceptable flow levels, the bleed <NUM>, <NUM>, <NUM>, <NUM> is selected to provide air that is under pressured. In other words, the pressure of the air provided by the selected bleed <NUM>, <NUM>, <NUM>, <NUM> is below the pressure required by the ECS. Further, the air selected generally exceeds the temperature requirements of the ECS.

After passing through the selection valve <NUM>, the air is passed to the intercooler <NUM>. The intercooler <NUM> is a heat exchanger that cools the bleed air prior to providing the air to the ECS. The exemplary intercooler <NUM> utilizes fan air, provided from the bypass flowpath of the engine <NUM>, to cool the air in an air to air heat exchanger format.

Cooled air from the intercooler <NUM> is provided to a second valve <NUM>. The second valve <NUM> is controlled by the aircraft controller <NUM> and provides air to a first auxiliary compressor <NUM>, a second auxiliary compressor <NUM>, or both the first and second auxiliary compressor <NUM>, <NUM>. Each of the auxiliary compressors <NUM>, <NUM> is driven by a corresponding electric motor <NUM>, <NUM> and raises the pressure of the air to a required pressure level for provision to the ECS. Also, the controller <NUM> is shown controlling both motors <NUM>/<NUM>. In alternative examples, one or both of the electric motors <NUM>, <NUM> can be replaced or supplemented by a mechanical motor.

Once pressurized via the auxiliary compressors <NUM>, <NUM> the air is provided to the ECS. In alternative examples, a single auxiliary compressor <NUM> can be used in place of the first and second auxiliary compressors <NUM>, <NUM>. In yet further alternative examples, three or more auxiliary compressors can be included, with the controller <NUM> rotating between the auxiliary compressors as necessary.

By cooling the bleed air prior to providing the bleed air to auxiliary compressors <NUM>, <NUM>, the amount of work required to compress the air at the auxiliary compressor <NUM>, <NUM> is reduced, thereby achieving a fuel efficiency savings relative to not cooling the air before the auxiliary compressors.

Controller <NUM> may include memory storing instructions configured to cause the controller to connect a bleed having a required flowrate and pressure for an ECS operating requirement, and wherein the connected bleed has a pressure requirement below a pressure requirement of the ECS inlet.

It should be understood the controller is programmed to achieve a desired pressure and temperature which may vary with the demand for the ECS system, and which may also vary based upon the operating condition of the gas turbine engine. The controller is operable to control valve <NUM>, valve <NUM>, and the compressor <NUM>/<NUM>. In addition, an optional variable speed transmission <NUM> may be provided such that the speed of the auxiliary compressor <NUM> can be controlled to achieve the desired conditions.

The controller is scheduled to understand the pressure required at the ECS inlet for various flight conditions. It selects the appropriate bleed port that supplies the highest pressure that is below the ECS required pressure. Power is supplied to the compressor such that the resultant pressure meets requirements. In some operating modes (descent or failure modes), the controller may select a pressure in excess of the ECS demand and use a regulating valve to reduce the pressure. This would not be a normal operating mode as it is contrary to the system goal (not to waste energy), but may be used to provide fail safe operation for failure conditions, or conditions like descent where very little fuel is burned (and thus there is not much of an opportunity for fuel burn reduction). Such operation will simplify the system design without compromising typical mission fuel burn reduction.

The aircraft <NUM> could be said to include a gas turbine engine having a compressor section including at least one compressor bleed. An environment control system (ECS) has an air input configured to receive pressurized cabin air. An intercooler has an input and an output. A selection valve is configured to selectively connect the bleed to the intercooler input. At least one auxiliary compressor is connected to the intercooler output. An output of the at least one auxiliary compressor is connected to the ECS air input. A controller is configured to receive contemporaneous operational data, calculate minimum configuration requirements to satisfy environmental demands, and transmit calculated configuration requirements to at least the selection valve to achieve a desired pressure and temperature for the air downstream of the auxiliary compressor.

The operational data may include engine performance demands and/or atmospheric data, as well as other conditions as appropriate. The environmental demands may be as known in the aircraft art.

While the circuit <NUM> is illustrated in <FIG> with a single engine <NUM>, a similar circuit can be utilized with multiple engines <NUM>, with the air from the bleeds <NUM>, <NUM>, <NUM>, <NUM> of each engine <NUM>, being mixed after being cooled in a corresponding intercooler <NUM>. Alternatively, the air from each engine <NUM> can be mixed at alternate positions in the ECS air circuit <NUM> prior to provision to auxiliary compressors <NUM>, <NUM>.

In the exemplary circuit <NUM> only one of the auxiliary compressors <NUM>, <NUM> may be required to provide sufficient pressurization to the ECS during standard operating conditions. As such, only a single auxiliary compressor <NUM>, <NUM> is typically operated during a flight. In order to even out wear between the auxiliary compressors <NUM>, <NUM> the primary operating auxiliary compressor <NUM>, <NUM> is alternated between flights on a per flight basis. Alternating between auxiliary compressors <NUM>, <NUM> further allows earlier detection, and correction, of a damaged or inoperable second auxiliary compressor <NUM>.

The controller may also include memory storing instructions configured to cause the controller to alternate auxiliary compressors operating as a primary compressor on a per flight basis.

During flight, should one engine <NUM> shut down, either due to mechanical failure, or for any other reason, the air provided from the bleeds <NUM>, <NUM>, <NUM>, <NUM>, is reduced. By way of example, if there are two engines <NUM>, and one shuts down, the air provided to the auxiliary compressors <NUM>, <NUM> is cut by <NUM>/<NUM> of the normal flow. In order to remedy this, in the exemplary system when one engine <NUM> shuts down, the currently inactive auxiliary compressor <NUM>, <NUM> begins operating simultaneously with the currently operating auxiliary compressor <NUM>, <NUM>. The simultaneous operations ensure that any lost pressure due to the loss of an engine is compensated for using air from the operating engine or engines. In aircraft having more than two auxiliary compressors <NUM>, <NUM>, the controller <NUM> can apply a proportional control to one or more of the auxiliary compressors to ensure that adequate pressure is maintained at the ECS in proportion to the pressure lost due to the lack of operation of the engine. Again, the controller <NUM> is programmed to achieve this control.

A disclosed system for use on a turbine engine powered aircraft provides conditioned air to an environmental control system. A heat exchanger has an input and an output. A selection valve is configured to selectively connect the heat exchanger input to at least one bleed of a compressor of the turbine engine. At least one auxiliary compressor is connected to the heat exchanger output. An output of the at least one auxiliary compressor is connected to an input of the environmental control system. A controller is configured to receive contemporaneous operational data, calculate minimum configuration requirements to satisfy environmental demands, and transmit calculated configuration requirements to at least the selection valve to achieve a desired pressure and temperature for the air downstream of the auxiliary compressor.

A method for supplying engine air to an environmental control system (ECS) includes selecting a compressor bleed from a plurality of compressor bleeds, the selected compressor bleed providing air at a higher temperature than a required ECS inlet air temperature maximum and at a lower pressure than a required ECS inlet air pressure, cooling the bleed air from the selected bleed using an intercooler such that the bleed air is below the required ECS inlet air temperature maximum, including the bleed air using at least one auxiliary compressor such that the bleed air is at least the required ECS inlet air pressure, and providing the cooled compressed bleed air to an ECS air inlet.

While certain drive connections are disclosed above for the auxiliary compressor <NUM>/<NUM>, it should also be understood that a hydraulic drive may be utilized.

It should be understood that the embodiments shown in <FIG> can be utilized in an engine as disclosed in <FIG>.

One example auxiliary compressor <NUM> is illustrated in <FIG>. As shown, a centrifugal compressor may be utilized having an inlet <NUM>, and an outlet <NUM>. Optional intermediate offtakes or taps <NUM> may be provided to achieve intermediate temperature and pressure requirements. The intermediate offtake <NUM> is provided with a valve <NUM>, shown schematically. The controller <NUM> may control the valve <NUM> such that this intermediate air can be directed to the ECS system under certain conditions. This is one method for tuning the compressor pressure to provide just what is needed by the air cycle machine. The compressor motor power and speed can also be controlled to provide the desired pressure. Again, the controller may be programmed to be able to identify when such an option might be valuable.

<FIG> shows an embodiment <NUM> of an engine similar to that shown in <FIG>. A fan rotor <NUM> is driven by a gear reduction <NUM>. A low pressure compressor <NUM> is driven by a shaft <NUM> driven by a fan drive turbine <NUM>. The fan drive turbine <NUM> drives the compressor at a common speed, and drives the fan rotor <NUM> at a reduced speed due to the gear reduction <NUM>.

A high pressure compressor <NUM> is driven by a high pressure turbine <NUM>. A combustor <NUM> is intermediate the two.

A bypass duct <NUM> is shown. As known, the fan rotor delivers air into the bypass duct <NUM> as bypass air B and also into a core engine as core air flow C. The core engine is defined by a core engine housing <NUM>. A fan case <NUM> sits outwardly of the fan rotor <NUM>.

In the embodiment of <FIG>, a low speed spool defined by the shaft <NUM> and fan drive turbine <NUM> drives a generator <NUM> to create electrical power to power the auxiliary compressor(s) <NUM> for the ECS system.

In an alternative embodiment shown in <FIG>, a takeoff shaft <NUM> is mechanically driven by the low spool (low spool includes turbine <NUM>, shaft <NUM>, and compressor <NUM>). The takeoff shaft <NUM> in turn may be utilized to power the auxiliary compressor <NUM> for the ECS system, as through appropriate gear connections.

<FIG> shows an engine embodiment wherein the heat exchanger <NUM> is mounted within the fan case <NUM>. As shown, a tap <NUM> would bring in air from the bypass duct, and an outlet <NUM> delivers the bypass air outwardly of the fan case <NUM>, after it has cooled the air in the heat exchanger <NUM>. As shown, connections <NUM> will connect the compressor taps to the heat exchanger <NUM>. Line <NUM> connects the tapped air to the upstream portions of a system such as shown in <FIG>.

<FIG> shows yet another embodiment. In this embodiment, the heat exchanger <NUM> is mounted within the bypass duct <NUM>. Again, it will be cooled by the fan air in the bypass duct <NUM>.

<FIG> shows yet another embodiment wherein the heat exchanger <NUM> is mounted within the core engine housing <NUM>. As shown, bypass air is tapped at <NUM> into the housing to cool the heat exchanger <NUM>. The air is shown exiting at point <NUM> and point <NUM>, which are optional exits. At point <NUM>, it will provide some propulsion. At point <NUM>, it may allow some reduction in the size of the engine.

Finally, the heat exchanger may be mounted externally from the engine, closer to the location of the auxiliary compressors, using either cooling air bled from the engine fan duct, or ram air.

<FIG> shows an embodiment <NUM> wherein the heat exchanger is located in either an upper bifurcation location 301u or a lower bifurcation location <NUM>. In this embodiment, the bifurcations <NUM> and <NUM> are shown schematically.

<FIG> shows the bifurcations 301u/L. The fan case <NUM> and the inner core housing <NUM> pivot about pivot points <NUM> to allow access to internal components. The bifurcations <NUM> and <NUM> are essentially a space provided by the two halves 300A and 300B of the embodiment which pivot away from each other.

<FIG> is a view showing the location <NUM> in a bifurcation between the sides 300A and 300B. A fan air inlet <NUM> is shown, as is a fan air exit <NUM>.

<FIG> is a view perpendicular to the <FIG> location and shows the similar structure. As shown, connections <NUM> and <NUM> provide the tapped air to the heat exchanger <NUM>, and take away the cooled air. It should be appreciated that the structure showing <FIG> can be in either the upper or lower bifurcation.

Claim 1:
A system for use on a turbine engine powered aircraft to provide conditioned air to an environmental control system (ECS), comprising:
a heat exchanger (<NUM>, <NUM>, <NUM>, <NUM>) having an input and an output;
a selection valve (<NUM>) configured to selectively connect said heat exchanger input to at least one of a plurality of bleeds (<NUM>, <NUM>, <NUM>, <NUM>) of a compressor (<NUM>, <NUM>) of the turbine engine (<NUM>, <NUM>); and
at least one auxiliary compressor (<NUM>, <NUM>, <NUM>, <NUM>) connected to said heat exchanger output, wherein an output of the at least one auxiliary compressor (<NUM>, <NUM>, <NUM>, <NUM>) is connected to an input of the environmental control system (ECS); and
a controller (<NUM>) configured to receive contemporaneous operational data, calculate minimum configuration requirements to satisfy environmental demands, and transmit calculated configuration requirements to at least said selection valve (<NUM>) to achieve a desired pressure and temperature for the air downstream of said at least one auxiliary compressor (<NUM>, <NUM>, <NUM>, <NUM>);
said selection valve (<NUM>) selectively connects at least one of said plurality of bleeds to provide air to said heat exchanger at a pressure below a desired pressure of said ECS air input;
at least one of said at least one auxiliary compressors (<NUM>, <NUM>, <NUM>, <NUM>) includes an electric motor (<NUM>, <NUM>) configured to drive rotation of the corresponding auxiliary compressor (<NUM>, <NUM>, <NUM>, <NUM>); and
said controller (<NUM>) is configured to control the electric motor (<NUM>, <NUM>) and the selection valve (<NUM>) to achieve the desired pressure and temperature for the air downstream of said at least one auxiliary compressor (<NUM>, <NUM>, <NUM>, <NUM>).