Gas turbine heat exchanger assembly and method for fabricating same

A method for assembling a gas turbine engine includes fabricating a heat exchanger that includes a first manifold including an inlet and an outlet, a first quantity of heat exchanger elements coupled in flow communication with the manifold inlet, a second quantity of heat exchanger elements coupled in flow communication with the manifold outlet, and a plurality of channels coupled in flow communication with the first and second quantity of heat exchanger elements to facilitate channeling compressor discharge air from the first quantity of heat exchanger elements to the second quantity of heat exchanger elements, and coupling the heat exchanger assembly to the gas turbine engine such that the heat exchanger is positioned substantially concentrically with respect to a gas turbine engine axis of rotation, and such that the heat exchanger is configured to receive compressor discharge air and channel the compressor discharge air to the combustor.

BACKGROUND OF THE INVENTION

This invention relates generally to gas turbine engines, and more particularly to heat exchangers used with gas turbine engines.

At least one known gas turbine engine uses a heat exchanger, generally referred to as a recuperator, to facilitate reducing specific fuel consumption. More specifically, pressurized air from the compressor section of the gas turbine engine is channeled from the gas turbine engine, and through the heat exchanger, such that the hot exhaust gases of the engine raise the operating temperature of the pressurized air prior to it being supplied into the combustor.

Known heat exchanger assemblies are positioned between the gas turbine engine exhaust gas box and the exhaust stack. At least some known heat exchanger assemblies include a pair of heat exchangers coupled in a parallel spaced relationship such that a space known as a bypass duct is defined therebetween. The bypass duct is closable by a butterfly valve. However, since known heat exchangers are typically physically large and rectangular-shaped, such heat exchangers are mounted externally to the gas turbine engine. Accordingly, the compressor discharge air and the engine exhaust gas is routed to and from the heat exchangers through a ducting which couples the heat exchangers to the gas turbine engine. As a result, known heat exchanger assemblies occupy a relatively large volume which is often larger than a volume occupied by the gas turbine engine itself. The resulting large and irregular heat exchanger assembly, coupled with the added weight and cost of the heat exchanger and ducting, generally makes regenerative engine systems unfeasible for aircraft applications.

In addition, although recuperated engines generally achieve a better low power specific fuel consumption than other known gas turbine engines, when such engines are operated with a heat exchanger assembly and at a higher operating power, gas-side total pressure losses of the hot exhaust gas stream may be relatively high through the exhaust system heat exchanger. The increased gas-side pressure losses caused by the heat exchanger assembly may result in an increased specific fuel consumption. Moreover, since the size of the heat exchanger is generally desired to be as small as possible, less space is available for a bypass system, which may result in high exhaust total pressure losses during high-power engine operating conditions.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method for assembling a gas turbine engine is provided. The method includes fabricating a heat exchanger that includes a first manifold including an inlet and an outlet, a first quantity of heat exchanger elements coupled in flow communication with the manifold inlet, a second quantity of heat exchanger elements coupled in flow communication with the manifold outlet, and a plurality of channels coupled in flow communication with the first and second quantity of heat exchanger elements to facilitate channeling compressor discharge air from the first quantity of heat exchanger elements to the second quantity of heat exchanger elements, and coupling the heat exchanger assembly to the gas turbine engine such that the heat exchanger is positioned substantially concentrically with respect to a gas turbine engine axis of rotation, and such that the heat exchanger is configured to receive compressor discharge air and channel the compressor discharge air to the combustor.

In another aspect, a heat exchanger assembly for a gas turbine engine is provided. The heat exchanger assembly includes an annular heat exchanger coupled in flow communication to a compressor. The heat exchanger includes a first manifold comprising an inlet and an outlet, wherein the manifold inlet comprises a cross-sectional area that is inversely proportional to a cross-sectional area of the manifold outlet, a first quantity of heat exchanger elements coupled in flow communication with the manifold inlet, a second quantity of heat exchanger elements coupled in flow communication with the manifold outlet, and a plurality of channels coupled in flow communication with the first and second quantity of heat exchanger elements to facilitate channeling compressor discharge air from the first quantity of heat exchanger elements to the second quantity of heat exchanger elements.

In a further aspect, a gas turbine engine is provided. The gas turbine engine includes a compressor, a combustor downstream from the compressor, a turbine coupled in flow communication with the combustor, and a heat exchanger assembly. The heat exchanger assembly includes an annular heat exchanger coupled in flow communication to a compressor. The heat exchanger includes a first manifold comprising an inlet and an outlet, wherein the manifold inlet comprises a cross-sectional area that is inversely proportional to a cross-sectional area of the manifold outlet, a first quantity of heat exchanger elements coupled in flow communication with the manifold inlet, a second quantity of heat exchanger elements coupled in flow communication with the manifold outlet, and a plurality of channels coupled in flow communication with the first and second quantity of heat exchanger elements to facilitate channeling compressor discharge air from the first quantity of heat exchanger elements to the second quantity of heat exchanger elements.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a perspective view of an exemplary gas turbine engine10including a heat exchanger assembly50.FIG. 2is a block diagram of gas turbine engine10(shown inFIG. 1). Gas turbine engine10includes, in serial flow relationship, a low pressure compressor or booster14, a high pressure compressor16, a combustor18, a high pressure turbine20, a low pressure, or intermediate turbine22, and a power turbine or free turbine24. Low pressure compressor or booster14has an inlet26and an outlet28, and high pressure compressor16includes an inlet30and an outlet32. Combustor18has an inlet34that is substantially coincident with high pressure compressor outlet32, and an outlet36. In one embodiment, combustor18is an annular combustor. In another embodiment, combustor18is a dry low emissions (DLE) combustor.

High pressure turbine20is coupled to high pressure compressor16with a first rotor shaft40, and low pressure turbine22is coupled to low pressure compressor14with a second rotor shaft42. Rotor shafts40and42are each substantially coaxially aligned with respect to a longitudinal centerline axis of rotation43of engine10. Engine10may be used to drive a load (not shown) which may be coupled to a power turbine shaft44. Alternatively, the load may be coupled to a forward extension (not shown) of rotor shaft42.

In operation, ambient air, drawn into low pressure compressor inlet26, is compressed and channeled downstream to high pressure compressor16. High pressure compressor16further compresses the air and delivers high pressure air to combustor18where it is mixed with fuel, and the mixture is ignited to generate high temperature combustion gases. The combustion gases are channeled from combustor18to drive turbines20,22, and24.

The power output of engine10is at least partially related to operating temperatures of the gas flow at various locations along the gas flow path. More specifically, in the exemplary embodiment, an operating temperature of the gas flow at high-pressure compressor outlet32, and an operating temperature of the gas flow at combustor outlet36are closely monitored during the operation of engine10. Increasing an operating temperature of the gas flow entering combustor18facilitates increasing the specific fuel consumption of engine10.

FIG. 3is a side view of heat exchanger assembly50shown inFIG. 1.FIG. 4is an end view of heat exchanger assembly50.FIG. 5is a plan view of a first manifold.FIG. 6is a plan view of a second manifold. In the exemplary embodiment, heat exchanger assembly50is removably coupled to a gas turbine rear frame52of gas turbine engine10and includes an outer casing54, a first manifold56, a second manifold58, and a heat exchanger60coupled to outer casing54and in flow communication with first and second manifolds56and58.

In one embodiment, first manifold56and a second manifold58are formed unitarily together. In another embodiment, first manifold56and a second manifold58are fabricated as separate components and are coupled together prior to being coupled to outer casing54. In another embodiment, first manifold56and a second manifold58are formed unitarily with outer casing54.

As described herein, first and second manifolds56and58extend 360 degrees around an outer surface of outer casing54. In the exemplary embodiment, first and second manifolds56and58each extend approximately 180 degrees around an outer surface of outer casing54. First manifold56includes an inlet70and an outlet72, and second manifold58includes an inlet74and an outlet76.

Heat exchanger60includes a plurality of heat exchangers elements, or struts80, that extend substantially circumferentially around an engine inside diameter between an outer periphery of a fixed plug nozzle82and an inner periphery of each respective manifold56,58. More specifically, heat exchanger60includes a first quantity of heat exchanger elements84and a second quantity of heat exchanger elements86that are interleaved with first quantity of heat exchangers elements84, such that at least one heat exchanger element84is positioned between at least two adjacent heat exchanger elements86.

In the exemplary embodiment, each heat exchanger element84includes an opening90such that each heat exchanger element84is in flow communication with manifold inlets70and74respectively, and each heat exchanger element86includes an opening92such that each heat exchanger element86is in flow communication with manifold outlets72and76respectively.

Heat exchanger60also includes a plurality of channels94that extend between plurality of struts80. More specifically, and in the exemplary embodiment, plurality of channels94extend between a heat exchanger element84and at least one adjacent heat exchanger element86such that air entering at least one heat exchanger element84is channeled through plurality of channels94and out at least one adjacent heat exchanger element86to facilitate heating the compressor discharge air.

In the exemplary embodiment, first manifold56includes a first cross-sectional area100and a second cross-sectional area102that is inversely proportional to first cross-sectional area100. More specifically, first manifold56is separated by a divider104such that heat exchanger elements84are coupled in flow communication with manifold inlet70, and heat exchanger elements86are coupled in flow communication with manifold outlet72.

Second manifold58includes a first cross-sectional area110and a second cross-sectional area112that is inversely proportional to first cross-sectional area110. More specifically, second manifold58is separated by a divider114such that heat exchanger elements84are coupled in flow communication with manifold inlet70, and heat exchanger element86are coupled in flow communication with manifold outlet76.

Heat exchanger assembly50also includes at least one compressor discharge pipe120, i.e., a cold pipe, and at least one combustor inlet pipe122, i.e., a hot pipe. In the exemplary embodiment, heat exchanger assembly50includes two compressor discharge pipes120, i.e., two cold pipes, and two combustor inlet pipes122, i.e., two hot pipes.

In the exemplary embodiment, heat exchanger60is an annular heat exchanger that is positioned within outer casing54. In another embodiment, heat exchanger60is at least one of a radial heat exchanger and/or a cross-flow heat exchanger that is positioned within outer casing54.

During installation of heat exchanger assembly50, heat exchanger assembly50is coupled to turbine rear frame52such that heat exchanger60is aligned substantially concentrically with respect to gas turbine engine axis of rotation43. A sealing apparatus (not shown) is positioned aft of the last stage of compressor16to facilitate channeling compressed air to heat exchanger elements84via first and second manifold inlets70and74respectively. More specifically, in the exemplary embodiment, a first end130of each respective compressor discharge pipe120is coupled in flow communication with compressor16, and a second end132of compressor discharge pipe120is coupled to first and second manifold inlets70and74respectively, such that compressor16is coupled in flow communication with manifolds56and58. Additionally, a first end134of each respective combustor inlet pipe122is coupled to combustor18, and a second end134of combustor inlet pipe122is coupled to first and second manifold outlets72and76respectively, such that combustor18is coupled in flow communication with manifolds56and58.

During operation, compressor discharge air from compressor16is channeled via compressor discharge pipe120to manifolds56and58respectively. More specifically, compressor discharge air from compressor16is channeled via compressor discharge pipes120to first and second manifold inlets70and74. The compressor discharge air is then channeled through opening90of each respective first quantity of heat exchangers84, and then through plurality of channels94wherein the relatively cool compressor discharge air is placed in heat exchange with the hot exhaust gases of gas turbine engine10. The heated compressor discharge air is then channeled through second quantity of heat exchangers86, through opening92, through first and second manifold outlets72and76, and returned to engine10, via combustor inlet pipes122, whereupon the heated compressed air is channeled to combustor section18.

The above-described heat exchanger assemblies provide a cost-effective and reliable means to facilitate increasing the specific fuel consumption of a gas turbine engine. More specifically, the heat exchanger assembly includes an annular heat exchanger that is coupled against the turbine rear frame. The annular heat exchanger is relatively small compared to known heat exchangers, thus enabling the heat exchanger to be coupled within the gas turbine engine outer casing aft of the gas turbine engine wherein known heat exchangers can not be used because of restricted space limitations.

FIG. 7is a side view of an alternative embodiment of a heat exchanger assembly200that can be used with gas turbine10(shown inFIG. 1). Heat exchanger assembly200is substantially similar to heat exchanger assembly50, (shown inFIGS. 3-6) and components of heat exchanger assembly200that are identical to components of heat exchanger assembly50are identified inFIG. 7using the same reference numerals used inFIGS. 3-6.

In the exemplary embodiment, heat exchanger assembly200is removably coupled to a gas turbine rear frame52of gas turbine engine10and includes an outer casing54, a first manifold56, a second manifold58, and a heat exchanger60coupled to outer casing54. In one embodiment, first manifold56and second manifold58are formed unitarily together. In another embodiment, first manifold56and second manifold58are fabricated as separate components and are coupled together prior to being coupled to outer casing54. In another embodiment, first manifold56and second manifold58are formed unitarily with outer casing54.

Heat exchanger assembly200also includes a variable plug nozzle drive assembly204that includes an electric motor drive assembly206coupled to a drive apparatus208. Variable plug nozzle202includes a nozzle210and a driving portion212coupled to nozzle210. In the exemplary embodiment, drive apparatus208is a worm gear and driving portion212is slidably coupled to drive apparatus208such that when motor assembly206is energized, drive apparatus208is rotated in either a first direction214or a second direction216. Rotating drive apparatus208in either first direction214or second direction216facilitates transitioning nozzle202in either a first axial direction218or a second axial direction220respectively.

During installation of heat exchanger assembly200, heat exchanger assembly200is coupled to turbine rear frame52such that heat exchanger60is aligned substantially concentrically with respect to gas turbine engine axis of rotation43. A sealing apparatus (not shown) is positioned aft of the last stage of compressor16to facilitate channeling compressed air to heat exchanger elements82via first and second manifold inlets70and74respectively. More specifically, in the exemplary embodiment, a first end130of each respective compressor discharge pipe120is coupled in flow communication with compressor16, and a second end132of compressor discharge pipe120is coupled to first and second manifold inlets70and74respectively, such that compressor16is coupled in flow communication with manifolds56and58. Additionally, a first end134of each respective combustor inlet pipe122is coupled to combustor18, and a second end134of combustor inlet pipe122is coupled to first and second manifold outlets72and76respectively, such that combustor18is coupled in flow communication with manifolds56and58.

In one embodiment, variable nozzle assembly202is transitioned from a first position222to a second position224by energizing motor drive assembly204. Energizing motor drive system204, i.e., motor206, rotates drive apparatus208in a second direction216. Since, driving portion212is coupled to both driving mechanism208and nozzle210, rotating driving mechanism208transitions nozzle210from a first direction218to a second direction220thus channeling a substantial portion of compressor discharge air through heat exchanger60to facilitate heating the compressor discharge air. Heating a substantial portion of the compressor discharge air, and channeling the heated air to combustor18, facilitates increasing the specific fuel consumption of gas turbine engine10.

In another embodiment, energizing motor drive assembly204causes variable nozzle assembly202to transition from a second position224to a first position222. Energizing motor drive system204, i.e. motor206, rotates drive apparatus208in a first direction214. Since, driving portion212is coupled to both driving mechanism208and nozzle210, rotating driving mechanism208causes nozzle210to transition from second direction220to first direction218thus channeling a substantial portion of the compressor discharge air around heat exchanger60and through the engine exhaust when heated combustor air is not desired.

The above-described heat exchanger assemblies provide a cost-effective and reliable means to facilitate increasing the specific fuel consumption of a gas turbine engine. More specifically, the heat exchanger assembly includes an annular heat exchanger that is coupled against the turbine rear frame. The annular heat exchanger is relatively small compared to known heat exchangers, thus enabling the heat exchanger to be coupled within the gas turbine engine outer casing aft of the gas turbine engine. The above-described heat exchanger can thus be used with a plurality of known gas turbine engines in a variety of different applications. For example, the above-described heat exchanger can be coupled to gas turbine engines used with airplanes, helicopters, and various marine applications. Moreover, the above-described heat exchanger can be used in a plurality of applications wherein known heat exchangers can not be used because of restricted space limitations.

The above-described heat exchanger assemblies can be pre-assembled prior to installing the heat exchanger assembly on the gas turbine engine. More specifically, the heat exchanger assembly can be provided as a kit that may be coupled to an existing engine. Thus, to install the heat exchanger assembly, the main components, i.e., the heat exchanger, the inlet and outlet manifolds, the nozzle, and the outer casing are pre-assembled. The main components are then coupled to the turbine rear frame, the compressor outlet pipe is coupled to the inlet manifold and the combustor inlet pipe is coupled to the outlet manifold to complete the installation on any known gas turbine engine.

Exemplary embodiments of a heat exchanger assembly are described above in detail. The heat exchanger assembly components illustrated are not limited to the specific embodiments described herein, but rather, components of each heat exchanger assembly may be utilized independently and separately from other components described herein. For example, the annular heat exchanger described above may also be used in combination with other engine combustion systems.