Patent Description:
Gas turbine engines may typically include a fan, a compressor, a combustor, and a turbine, with an annular flow path extending axially through each. Initially, the fan, which is powered by the turbine, draws ambient air into the engine. Part of the air flows through the compressor where it is compressed or pressurized. The combustor then mixes and ignites the compressed air with fuel, generating hot combustion gases. These hot combustion gases are then directed from the combustor to the turbine where power is extracted from the hot gases by causing blades of the turbine to rotate. This flow path may be referred to as a core flow path. The other part of the airflow from the fan, which may be referred to as a bypass flow path, is used to generate forward thrust.

Gas turbine engines operate at extremely high temperatures. These temperatures may exceed the temperature limits of some of the materials of the engine components. Therefore, cooling air may be supplied to the engine components in order to cool the hot components. For example, cooling air may be extracted from the compressor section and directed to certain components of the turbine section.

Furthermore, in some cases, the cooling air extracted from the compressor section may have to be further cooled by fan air from the bypass flow path before being delivered to the turbine components. This air may be referred to as cooled cooling air (CCA). CCA may be supplied continuously throughout engine operation. However, there may be situations when CCA is not required, which results in pressure loss for a specific thrust requirement, thereby reducing fuel burn.

Accordingly, there exists a need for a system and method that adequately provides CCA to turbine components while minimizing pressure loss.

<CIT> and <CIT> disclose cooling systems for gas turbine engines. In <CIT> a heat exchanger is located in a bypass duct and receives and cools core airflow. The heat exchanger receives a second airflow from the bypass duct and discharges this to a third air stream.

<CIT> discloses a heat exchanger system with a valve arrangement. <CIT> discloses a fan bleed duct for bleeding fan air from a fan bypass duct through a control valve.

Viewed from one aspect there is provided a heat exchanger for a gas turbine engine according to claim <NUM>.

According to one embodiment, a heat exchanger system for a gas turbine engine is disclosed. The heat exchanger system comprises a first structure at least partially defining a first plenum configured to receive a first air stream, a second structure at least partially defining a second plenum configured to receive a second air stream having lower pressure than the first air stream, a third structure at least partially defining a third plenum configured to receive a third air stream having lower pressure than the second air stream, and a heat exchanger configured for operative communication with the first air stream, the second air stream, and the third air stream while disposed between the second air stream and the third air stream. The heat exchanger is configured to transfer heat from a portion of the first air stream to a portion of the second air stream at the heat exchanger, the portion of the second air stream flowing to the third air stream. The heat exchanger includes a flow metering device configured to control flow through the heat exchanger, and a scoop integrated into the flow metering device, the scoop configured to capture and direct maximum airflow into the heat exchanger at an elevated pressure. The heat exchanger is disposed within a second duct surrounding the second air stream between the second air stream and the third air stream.

In a refinement, the second duct includes aerodynamic surfaces surrounding the heat exchanger.

In another refinement, the first air stream may comprise a core flow path, and each of the second air stream and the third air stream may be comprised of a bypass flow path.

In another refinement, the heat exchanger may include: a first inlet associated with the first air stream, a first exit associated with a cooling air, a plurality of first passages extending from the first inlet to the first exit, a second inlet associated with the second air stream, a second exit associated with the third air stream, and a plurality of second passages extending from the second inlet to the second exit. A portion of the first air stream may flow into the first inlet through the plurality of first passages and out of the first exit. A portion of the second air stream may flow into the second inlet through the plurality of second passages and out of the second exit. The heat exchanger may transfer heat between the portion of the first air stream in the plurality of first passages and the portion of the second air stream in the plurality of second passages.

In another refinement, the cooling air exiting from the first exit of the heat exchanger may be used to cool components of the gas turbine engine.

In another refinement, the flow metering device may be positioned proximate a forward side of the heat exchanger.

In another refinement, the flow metering device may be positioned proximate an inlet of the heat exchanger.

Viewed from another aspect there is provided a method for cooling components of a gas turbine engine according to claim <NUM>.

A method for cooling components of a gas turbine engine is disclosed comprising installing a heat exchanger between two air streams having different air pressures, providing the heat exchanger with a flow metering device configured to modulate flow through the heat exchanger, using the heat exchanger to cool air from a core flow path of the gas turbine engine, and supplying the cooled air from the heat exchanger to components of the gas turbine engine. A scoop is integrated into the flow metering device, the scoop configured to capture and direct maximum airflow into the heat exchanger at an elevated pressure.

In another refinement, the method may further comprise selectively allowing flow through the heat exchanger using the flow metering device.

In another refinement, the method may further comprise opening the flow metering device to allow flow through the heat exchanger when cooling air is required.

In another refinement, the method may further comprise closing the flow metering device to stop flow through the heat exchanger when cooling air is not required.

In another refinement, the method may further comprise providing the flow metering device proximate an inlet of the heat exchanger.

According to yet another embodiment of the present disclosure, a gas turbine engine is disclosed. The gas turbine engine comprises a first air duct surrounding a first air stream, a second air duct surrounding a second air stream, a third air duct surrounding a third air stream, and a heat exchanger disposed within the second air duct. The second air stream may surround the first air duct and have a lower pressure than the first air stream. The third air stream may surround the second air duct and have a lower pressure than the second air stream.

In a refinement, air flow from a combustor may mix with a cooling air from the heat exchanger for delivery to hot components.

In another refinement, the second air duct may include fairing members surrounding the heat exchanger.

These and other aspects and features of the disclosure will become more readily apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings. Although various features are disclosed in relation to specific exemplary embodiments of the invention, it is understood that the various features may be combined with each other, or used alone, with any of the various exemplary embodiments of the invention without departing from the scope of the invention as defined in the appended claims.

While the present disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof, will be shown and described below in detail. It should be understood, however, that there is no intention to be limited to the specific embodiments disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the scope of the present invention as defined in the appended claims.

Referring now to the drawings, and with specific reference to <FIG>, in accordance with the teachings of the disclosure, an exemplary gas turbine engine <NUM> is shown. The gas turbine engine <NUM> may generally comprise a fan section <NUM> which draws ambient air into the engine <NUM>, a compressor section <NUM> where part of the air flow from the fan section is pressurized, a combustor section <NUM> downstream of the compressor section which mixes and ignites the compressed air with fuel and thereby generates hot combustion gases, a turbine section <NUM> downstream of the combustor section <NUM> for extracting power from the hot combustion gases, and a first air stream <NUM> extending axially through each. The other part of the air flow from the fan section <NUM> may comprise a bypass flow path <NUM> used to generate forward thrust.

Gas turbine engine <NUM> may be used on an aircraft for generating thrust or power, or in land-based operations for generating power as well. It is understood that gas turbine engine <NUM> may include fewer or additional sections than fan section <NUM>, compressor section <NUM>, combustor section <NUM>, and turbine section <NUM>.

The first air stream <NUM> may flow along an annular core flow path of the gas turbine engine. An engine casing or first air duct <NUM> may enclose compressor section <NUM>, combustor section <NUM>, turbine section <NUM>, and first air stream <NUM>. Generally, the fan section <NUM> may drive air along the bypass flow path <NUM>, and the compressor section <NUM> may drive air along the core flow path or first air stream <NUM>.

Referring now to <FIG>, with continued reference to <FIG>, a first plenum <NUM> is configured to receive the first air stream <NUM>, a second plenum <NUM> is configured to receive a second air stream <NUM>, and a third plenum <NUM> is configured to receive a third air stream <NUM> within the gas turbine engine <NUM>. Structures <NUM> at least partially define the first plenum <NUM>. Structures <NUM> at least partially define the second plenum <NUM>, and structures <NUM> at least partially define the third plenum <NUM>.

The second air stream <NUM> may surround the first air duct <NUM>, and a second air duct <NUM> may enclose the second air stream <NUM>. The third air stream <NUM> may surround the second air duct <NUM>, and a third air duct <NUM> may enclose the third air stream <NUM>. Each of the second air stream <NUM> and the third air stream <NUM> may be comprised of bypass flow paths from the fan section <NUM>, e.g., a first fan stream and a second fan stream. The first air stream <NUM> may have a higher air pressure/temperature than the second air stream <NUM>, and the second air stream <NUM> may have a higher air pressure/temperature than the third air stream <NUM>.

A heat exchanger system <NUM> may be installed in the gas turbine engine <NUM> in order to supply cooled cooling air (CCA) to engine components. According to an embodiment of the present disclosure, the heat exchanger system <NUM> comprises a heat exchanger <NUM> positioned between the second air stream <NUM> and the third air stream <NUM>. The heat exchanger <NUM> is disposed within the second air duct <NUM>. Aerodynamic contouring may be applied to the heat exchanger system <NUM> in order to minimize pressure loss. For instance, the second air duct <NUM> may include aerodynamic surfaces <NUM> surrounding the heat exchanger <NUM>. Aerodynamic surfaces <NUM> may comprise fairings designed to increase streamlining and reduce drag around the heat exchanger system <NUM>. It is to be understood that the gas turbine engine <NUM> may include a plurality of heat exchanger systems <NUM> and a plurality of heat exchangers <NUM>.

In operative communication with the first air stream <NUM>, the second air stream <NUM>, and the third air stream <NUM>, heat exchanger <NUM> may be configured to transfer heat from one air stream to another in order to provide CCA to hot components of the gas turbine engine <NUM>. For example, heat exchanger <NUM> may comprise a plate heat exchanger, although other types of heat exchangers are certainly possible. Heat exchanger <NUM> may include a first inlet <NUM> associated with the first air stream <NUM>, a second inlet <NUM> associated with the second air stream <NUM>, a first exit <NUM> associated with a cooling air or CCA <NUM>, and a second exit <NUM> associated with the third air stream <NUM>. The inlets <NUM>, <NUM> and exits <NUM>, <NUM> may comprise openings, apertures, pipes, tubes, or any other structure which provides communication of the heat exchanger <NUM> with the different air streams <NUM>, <NUM>, <NUM>. A plurality of first parallel flow passages <NUM> may extend from the first inlet <NUM> to the first exit <NUM>, and a plurality of second parallel flow passages <NUM> may extend from the second inlet <NUM> to the second exit <NUM>.

A portion <NUM> of the first air stream <NUM> may be extracted from the compressor section <NUM>, such as, from a low or high compressor, in order to be cooled for the supply of CCA to hot components of the gas turbine engine <NUM>. Since the second air stream <NUM> has a lower temperature than the first air stream <NUM>, a portion <NUM> of the second air stream <NUM> may be used to cool the portion <NUM> of the first air stream <NUM> via heat exchanger <NUM>. The portion <NUM> of the first air stream <NUM> enters the first inlet <NUM> and flows through the plurality of first passages <NUM> of the heat exchanger <NUM>, while the portion <NUM> of the second air stream <NUM> enters the second inlet <NUM> and flows through the plurality of second passages <NUM> of the heat exchanger <NUM>. While flowing through the plurality of first and second passages <NUM>, <NUM> of the heat exchanger <NUM>, heat is transferred from the portion <NUM> of the first air stream <NUM> to the portion of <NUM> of the second air stream <NUM>.

Due to the heat transfer via heat exchanger <NUM>, the portion <NUM> of the first air stream <NUM> is cooled and comprises the CCA <NUM>, which flows out of the first exit <NUM> and onto the components of the gas turbine engine <NUM> that need cooling. For example, CCA <NUM> may be directed to the compressor section <NUM> and the turbine section <NUM>, such as to blades <NUM> and rim cavities <NUM> of a high pressure compressor <NUM> and/or a high pressure turbine <NUM>. CCA <NUM> may certainly be used to cool blades and rim cavities of a low pressure compressor and/or a low pressure turbine, and other hot components of the gas turbine engine <NUM> as well. Furthermore, air flow <NUM> from a combustor <NUM> of the gas turbine engine <NUM> may be used to mix with the CCA <NUM> from the heat exchanger <NUM> in order to increase air pressure of the CCA <NUM> for delivery to the hot components (e.g., blades <NUM> and rim cavities <NUM>).

In addition, since the second air stream <NUM> has a higher pressure than the third air stream <NUM>, the portion <NUM> of the second air stream <NUM> (which has a higher temperature after heat transfer via heat exchanger <NUM>) flows out of the second exit <NUM> and into the third air stream <NUM>.

Therefore, heat from the portion <NUM> of the first air stream <NUM> is ultimately transferred to the third air stream <NUM>. Since the heat exchanger <NUM> is located between the second air stream <NUM> and the third air stream <NUM>, the pressure difference between the second and third air streams <NUM>, <NUM>, provides efficient flow of the portion <NUM> of the second air stream <NUM> into the third air stream <NUM>. It is to be understood that although shown and described as being positioned between the second air stream <NUM> and the third air stream <NUM>, heat exchanger <NUM> may be positioned between any two air streams which have a pressure difference relative to each other.

Turning now to <FIG>, with continued reference to <FIG> and <FIG>, the heat exchanger system <NUM> further includes a flow metering device <NUM>. The flow metering device <NUM> is configured to control flow through the heat exchanger <NUM>. For example, when cooling or CCA is required during engine operation, the flow metering device <NUM> may allow flow (e.g. portions <NUM> of the first air stream <NUM>, portion <NUM> of the second air stream <NUM>, and CCA <NUM>) through the heat exchanger <NUM>. When cooling or CCA is not required, the flow metering device <NUM> may actuate to stop flow through the heat exchanger <NUM>, thereby reducing pressure loss incurred via flow through the heat exchanger <NUM>. In addition, the flow metering device <NUM> may have an aerodynamic design or shape configured to reduce pressure loss.

The flow metering device <NUM> may comprise, without limitation, a door, a valve, a butterfly valve, a gate valve, check valve, or any other modulating device that can regulate flow through the heat exchanger <NUM>. For example, as shown best in <FIG>, the flow metering device <NUM> may comprise a plurality of slats <NUM> in a louver style arrangement. It is to be understood that although the slats <NUM> are oriented horizontally in <FIG>, they may be arranged in a vertical or angled orientation as well. Furthermore, the flow metering device <NUM> may have a low pressure loss design in order to maximize the pressure available to the heat exchanger <NUM>. The flow metering device <NUM> may have an on or open position to allow flow through the heat exchanger <NUM> and an off or closed position to stop flow through the heat exchanger <NUM>. In addition, the flow metering device <NUM> may have positions between fully open and fully closed in order to modify the amount of flow through the heat exchanger <NUM>, such as, depending on specific CCA requirements.

Various methods may be used to the flow metering device <NUM>. For example, a sensor may be used to measure a pressure and/or temperature flow, or other condition, and the flow metering device <NUM> may be actuated to reach a certain set point or position based on the sensor feedback of the measured condition. The flow metering device <NUM> may also be independent of sensor feedback and may be actuated based on a set predetermined schedule, such as, based on flight conditions. In another example, the flow metering device <NUM> may be in communication with a controller, which may manage the flow metering device <NUM> according to a high fidelity control. The flow metering device <NUM> may be purely driven by the pressure difference between the second and third air streams <NUM>, <NUM> such that the flow metering device <NUM> opens as the pressure difference increases and closes as the pressure difference decreases. In yet another example, the flow metering device <NUM> may comprise a complex flow control device having aerodynamic bearings and a variety of flow metering orbises controlled by an engine computer controller.

As shown in <FIG>, the flow metering device <NUM> is positioned at a front or forward side <NUM> of the heat exchanger <NUM>. The flow metering device <NUM> is located on the second inlet <NUM> associated with the portion <NUM> of the second air stream <NUM>. Other arrangements not forming part of the invention are shown for explanatory purposes in <FIG>. In an arrangement shown in <FIG>, a flow metering device <NUM> may be positioned at a rear or aft side <NUM> of the heat exchanger <NUM>. As shown in <FIG>, a flow metering device <NUM> may be located on the first inlet <NUM> associated with the portion <NUM> of the first air stream <NUM>. As shown in <FIG>, a flow metering device <NUM> may also be located on the first exit <NUM> associated with the CCA <NUM>. As shown in <FIG>, a flow metering device <NUM> may be located on the second exit <NUM> associated with the third air stream <NUM>, as well.

It is to be understood that the heat exchanger system <NUM> may have more than one flow metering device <NUM>. For example, a first flow metering device may be positioned on the forward side <NUM> of the heat exchanger <NUM> and a second flow metering device may be positioned on the aft side <NUM> of the heat exchanger <NUM>, such as, on any of the inlets <NUM>, <NUM> and/or exits <NUM>, <NUM>.

Furthermore, the heat exchanger system <NUM> includes a scoop <NUM> integrated into the flow metering device <NUM>, as shown best in <FIG>. The scoop <NUM> is designed to capture and direct maximum air flow into the heat exchanger <NUM> at an elevated pressure. In so doing, the scoop <NUM> minimizes pressure loss and reduces exit temperatures of the heat exchanger <NUM>. The integrated scoop <NUM> and flow metering device <NUM> enables flow capture and modulation of flow.

Referring now to <FIG>, with continued reference to <FIG>, a flowchart outlining a process <NUM> for cooling components of the gas turbine engine <NUM> is shown, according to another embodiment of the present disclosure. At a block <NUM>, the heat exchanger <NUM> may be installed between two air streams <NUM>, <NUM> having different air pressures. At a block <NUM>, the heat exchanger <NUM> may be used to cool air <NUM> from a core flow path <NUM> of the gas turbine engine <NUM>. The cooled air or CCA <NUM> from the heat exchanger <NUM> may be supplied to components of the gas turbine engine <NUM>.

From the foregoing, it can be seen that the teachings of this disclosure can find industrial application in any number of different situations, including but not limited to, gas turbine engines. Such engines may be used, for example, on aircraft for generating thrust, or in land, marine, or aircraft applications for generating power.

The present disclosure provides a heat exchanger system and process for cooling components of the gas turbine engine. In the disclosed system and method, the heat exchanger is installed in an aerodynamically contoured area between (cross-stream) two bypass air streams around the engine core. The pressure difference between the two bypass air streams provides a cold side flow, which is used to cool air from the engine core.

Furthermore, the flow metering device of the present disclosure may modulate flow between the two air streams depending on the cooling requirements. The flow metering device at the front of the heat exchanger is a simplified, low cost solution. Moreover, the integrated scoop increases flow through the heat exchanger, thereby minimizing pressure loss and reducing a cold side exit temperature. Positioning the flow metering device at the rear of the heat exchanger (e.g., CCA or hot side exit) may provide a desirable lower pressure and/or separated exhaust, while positioning the flow metering device on the engine core air stream (hot side) inlet may minimize pipe volume and protect the heat exchanger from large temperature excursions.

Compared to prior art heat exchangers which were typically installed in-line with an air stream flow, the aerodynamic contouring applied to the installed cross-stream heat exchanger incurs a smaller amount of pressure loss. In addition, since cooling is not required across the entire mission profile, the disclosed heat exchanger system with a flow metering device allows reduced pressure loss for a specific thrust requirement, which results in reduced fuel burn.

Claim 1:
A heat exchanger system (<NUM>) for a gas turbine engine (<NUM>), comprising:
a first structure (<NUM>) at least partially defining a first plenum (<NUM>) configured to receive a first air stream (<NUM>);
a second structure (<NUM>) at least partially defining a second plenum (<NUM>) configured to receive a second air stream (<NUM>) having lower pressure than the first air stream (<NUM>);
a third structure (<NUM>) at least partially defining a third plenum (<NUM>) configured to receive a third air stream (<NUM>) having lower pressure than the second air stream (<NUM>);
a second duct (<NUM>) surrounding the second air stream (<NUM>); and
a heat exchanger (<NUM>) configured for operative communication with the first air stream (<NUM>), the second air stream (<NUM>), and the third air stream (<NUM>) while disposed between the second air stream (<NUM>) and the third air stream (<NUM>), the heat exchanger (<NUM>) configured to transfer heat from a portion of the first air stream (<NUM>) to a portion of the second air stream (<NUM>) at the heat exchanger (<NUM>), the portion of the second air stream (<NUM>) flowing to the third air stream (<NUM>);
the heat exchanger system (<NUM>) being characterized in that
the heat exchanger (<NUM>) includes a flow metering device (<NUM>) configured to control flow through the heat exchanger (<NUM>); and
a scoop (<NUM>) integrated into the flow metering device (<NUM>), the scoop (<NUM>) configured to capture and direct maximum airflow into the heat exchanger (<NUM>) at an elevated pressure;
wherein the heat exchanger (<NUM>) is disposed within the second duct (<NUM>) between the second air stream (<NUM>) and the third air stream (<NUM>).