Apparatus for operating gas turbine engines

A method facilitates assembling a gas turbine engine assembly. The method comprises providing at least one propelling gas turbine engine that includes a core engine including at least one turbine, coupling an auxiliary engine to the propelling gas turbine engine such that during operation of the propelling gas turbine engine, such that at least a portion of the airflow entering the propelling gas turbine engine is extracted from the propelling gas and channeled to the auxiliary engine for generating power, and coupling a modulating valve in flow communication to the propelling gas turbine engine to control the flow of airflow from the propelling gas turbine engine to the auxiliary engine, wherein the modulating valve is selectively operable to control an extraction point of airflow from the propelling gas turbine engine.

BACKGROUND OF THE INVENTION

This invention relates generally to the gas turbine engines, and, more particularly, to methods and apparatus for operating gas turbine engines used for aircraft propulsion and auxiliary power.

Gas turbine engines typically include a compressor for compressing air. The compressed air is mixed with a fuel and channeled to a combustor, wherein the fuel/air mixture is ignited within a combustion chamber to generate hot combustion gases. The combustion gasses are channeled to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work. The exhaust gases are then discharged through an exhaust nozzle, thus producing a reactive, propelling force.

Modern aircraft have increased hydraulic and electrical loads. An electrical load demanded of gas turbine engines increases as flight computers, communication equipment, navigation equipment, radars, environmental control systems, advanced weapon systems, and defensive systems are coupled to aircraft. A hydraulic load demanded of gas turbine engines increases as flight controls, pumps, actuators, and other accessories are coupled to the aircraft. Within at least some known aircraft, mechanical shaft power is used to power hydraulic pumps, electrical generators and alternators. More specifically, electrical and hydraulic equipment are typically coupled to an accessory gearbox that is driven by a shaft coupled to the turbine. When additional electrical power or hydraulic power is required, additional fuel is added to the combustor until a predefined maximum temperature and/or power operating level is reached.

Because the density of air decreases as the altitude is increased, when the aircraft is operated at higher altitudes, the engine must work harder to produce the same shaft power that the engine is capable of producing at lower altitudes. As a result of the increased work, the turbine may operate with increased operating temperatures, such that the shaft power must be limited or reduced to prevent exceeding the engine predefined operating limits.

Within at least some known gas turbine engines, electrical power and hydraulic power is also generated by an auxiliary power unit (APU). An APU is a small turbo-shaft engine that is operated independently from the gas turbine engines that supply thrust for the aircraft. More specifically, because APU operation is also impacted by the air density and is also operationally limited by predefined temperature and performance limits, APUs are typically only operated when the aircraft is on the ground, or in emergency situations while the aircraft is in flight.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method for assembling a gas turbine engine assembly is provided. The method comprises providing at least one propelling gas turbine engine that includes a core engine including at least one turbine, coupling an auxiliary engine to the propelling gas turbine engine such that during operation of the propelling gas turbine engine, such that at least a portion of the airflow entering the propelling gas turbine engine is extracted from the propelling gas and channeled to the auxiliary engine for generating power, and coupling a modulating valve in flow communication to the propelling gas turbine engine to control the flow of airflow from the propelling gas turbine engine to the auxiliary engine, wherein the modulating valve is selectively operable to control an extraction point of airflow from the propelling gas turbine engine.

In another aspect, a gas turbine engine assembly is provided. The gas turbine engine assembly includes at least one propelling gas turbine engine, a modulating valve, and an auxiliary engine used for generating power. The propelling gas turbine engine includes a fan, a core engine downstream from the fan, and a plurality of extraction points. The modulating valve is coupled in flow communication to each propelling gas turbine engine. The auxiliary engine includes at least one turbine and an inlet. The inlet is coupled in flow communication with the modulating valve, such that a portion of airflow entering the propelling engine is extracted for use by the auxiliary engine and such that the modulating valve controls the flow of airflow from the propelling engine to the auxiliary engine. The modulating valve is selectively operable to extract airflow from at least two of the plurality of extraction points.

In a further aspect, an aircraft gas turbine engine assembly including a propelling gas turbine engine, a modulating valve, and at least one auxiliary engine is provided. The propelling gas turbine engine includes a core engine and an exhaust. The core engine includes at least one turbine, and the propelling gas turbine engine is used for generating thrust for the aircraft. The modulating valve is coupled in flow communication with at least one of a plurality of airflow extraction sources defined within the propelling gas turbine engine. The auxiliary engine includes an inlet, at least one turbine, and an exhaust. The inlet is coupled in flow communication with the modulating valve such that a portion of airflow flowing through the propelling engine is selectively extractable from the at least one propelling engine and is channeled to the auxiliary engine for generating power.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an exemplary schematic view of a gas turbine engine assembly10including a propelling gas turbine engine11and an auxiliary power unit or auxiliary power engine12that are coupled together, as described in more detail below, in a combined cycle. More specifically, gas turbine engine assembly10, as described in more detail below, facilitates producing shaft power and propelling force for an aircraft (not shown).

Gas turbine engine11includes a core engine13and a fan assembly14and a low pressure turbine assembly20. Core engine13includes a high-pressure compressor16, a combustor (not shown), and a high-pressure turbine18. Fan assembly14and turbine20are coupled by a first shaft22, and compressor16and turbine18are coupled by a second shaft23. Gas turbine engine11also includes an inlet side24and an exhaust side26. In one embodiment, engine11is a F118-GE-100 turbofan engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio.

In operation, inlet air, represented by arrow30, enters fan assembly14, wherein the air is compressed and is discharged downstream, represented by arrow31, at an increased pressure and temperature towards core engine13and more specifically, towards high-pressure compressor16. In one embodiment, engine11includes a bypass duct (not shown) such that a portion of air31discharged from fan assembly14is also channeled into the bypass duct rather than entering core engine13.

Highly compressed air35is delivered to a combustor (not shown) wherein it is mixed with fuel and ignited. Combustion gases propel turbines18and20, which drive compressor16and fan assembly14, respectively. In the exemplary embodiment, core engine exhaust32is discharged from engine to generate a propelling force from gas turbine engine assembly10. In the exemplary embodiment, core engine exhaust32is channeled to a variable area bypass injector82that is coupled in flow communication with core engine exhaust32and auxiliary engine exhaust80. In an alternative embodiment, core engine exhaust32is channeled to a mixing damper (not shown) that is coupled in flow communication with core engine exhaust32. In another alternative embodiment, core engine exhaust flow and fan air are discharged separately from auxiliary engine exhaust80to produce thrust.

Auxiliary power engine12is coupled in flow communication to engine11, as described in more detail below, and includes a compressor42, a high-pressure turbine44, and a low-pressure turbine46. Compressor42and high-pressure turbine44are connected by a first shaft43such that as combustion gases propel turbine44, turbine44drives compressor42. Auxiliary engine12also includes a second shaft48coupled to low-pressure turbine46which provides shaft power output, represented by arrow49, for use in the aircraft. Power output49may be used to drive equipment, such as, but not limited to alternators, generators, and/or hydraulic pumps. In one embodiment, auxiliary power engine12is a turbo-shaft engine, such as a T700-GE-701 engine that is commercially available from General Electric Company, Cincinnati, Ohio, and that has been modified in accordance with the present invention.

Auxiliary ducting (not shown) couples auxiliary power engine12to engine11to enable a portion of air31channeled towards core engine13to be directed to auxiliary power engine12. More specifically, auxiliary airflow, represented by arrow52is extracted from core engine13at a location upstream from core engine turbine18. In the exemplary embodiment, airflow52is bled from high-pressure compressor16and is routed towards auxiliary engine compressor42. In an alternative embodiment, auxiliary power engine12is coupled in flow communication to a pair of engines11and receives high pressure airflow54from each engine11. In another alternative embodiment, a pair of auxiliary power engines12are coupled in flow communication to a single engine11and both receive high pressure airflow54from engine11. More specifically, in the exemplary embodiment, compressor16is a multi-staged compressor and air52may be extracted at any compressor stage based on pressure, temperature, and flow requirements of auxiliary engine12. In another embodiment, air52is extracted downstream from compressor16. In a further alternative embodiment, air52is extracted upstream from compressor16. In one embodiment, approximately up to 10%, or more, of air flowing into compressor16is extracted for use by auxiliary engine12. In a further embodiment, air52is extracted from any of, but is not limited to being extracted from, a booster interstage, a booster discharge, a fan interstage, a fan discharge, a compressor inlet, a compressor interstage, or a compressor discharge bleed port. In another embodiment, approximately up to 10% or more, of air flowing into fan14is extracted for used by auxiliary engine12.

In an alternative embodiment, engine11supplies pressurized or compressed air to auxiliary power engine12. For example, in one embodiment, compressed air supplied to an aircraft cabin is routed to auxiliary power engine12after being used within the aircraft environmental control system. In a further embodiment, auxiliary power engine12receives a mixture of airflow from engine11and ambient airflow.

Auxiliary airflow54directed towards auxiliary engine12is at a higher pressure and temperature than airflow30entering gas turbine engine assembly10. Moreover, because the auxiliary airflow30is at an increased pressure and temperature than that entering gas turbine engine assembly10, a density of airflow54is substantially similar to the density of airflow that enters auxiliary engine12at lower altitudes. Accordingly, because the power output of auxiliary engine12is proportional to the density of the inlet air, during operation of core engine13, auxiliary engine12is operable at higher altitudes with substantially the same operating and performance characteristics that are available at lower altitudes by auxiliary engine12. For example, when used with the F110/F118 family of engines, auxiliary engine12produces approximately the same horsepower and operating characteristics at an altitude of 30-40,000 feet, as would be obtainable if auxiliary engine12was operating at sea level independently. Accordingly, at mission altitude, a relatively small amount of high-pressure air taken from core engine13will enable auxiliary power engine12to output power levels similar to those similar from auxiliary power engine12at sea level operation.

In the exemplary embodiment, auxiliary airflow52is channeled through an intercooler60prior to being supplied to auxiliary engine compressor42. Intercooler60has two airflows (not shown) in thermal communication with each other and is designed to exchange a substantial amount of energy as heat, with minimum pressure losses. In the exemplary embodiment, auxiliary airflow52is the heat source and a second airflow is used as a heat sink. In one embodiment, the second airflow is fan discharge airflow. In another embodiment, the second airflow is ambient airflow routed through an engine nacelle and passing through intercooler60prior to being discharged overboard. More specifically, the operating temperature of auxiliary airflow54is facilitated to be reduced within intercooler60as the transfer of heat increases the temperature of the other airflow channeled through intercooler60. In an alternative embodiment, turbine engine assembly10does not include intercooler60.

Intercooler60facilitates increasing an amount of power per pound of bleed air54supplied to auxiliary power engine12without increasing flow rates or changing existing turbine hardware. A control system62is coupled to a generator control system (not shown) and facilitates regulating the operating speed of auxiliary power engine12. In one embodiment, control system62throttles inlet air52supplied to engine12by control of a variable flow area throttle valve61and/or controls engine backpressure by control of a variable flow area exit nozzle63or a variable area bypass injector82to facilitate controlling the operation of auxiliary power engine12.

Exhaust airflow80from auxiliary power engine12is channeled towards core engine exhaust32at a discharge pressure that is substantially the same as a discharge pressure of exhaust flow32discharged from core engine13. Specifically, in the exemplary embodiment, auxiliary engine exhaust airflow80is routed through a variable area bypass injector82which facilitates mixing exhaust flow32exiting core engine13with auxiliary engine exhaust airflow80. More specifically, in the exemplary embodiment, exhaust airflow80is reintroduced to core engine exhaust flow32upstream from a propelling core engine nozzle (not shown). The mixed exhaust flow86is then discharged through an engine nozzle (not shown). In an alternative embodiment, exhaust airflow80is not mixed with core engine exhaust flow32, but rather is discharged independently from exhaust flow32.

Accordingly, when operated, auxiliary power engine12facilitates providing increased shaft power production for use within the aircraft. More specifically, because auxiliary power engine12is selectively operable for shaft power production, auxiliary power engine12may be used only when needed, thus facilitating fuel conservation for the aircraft. In addition, the design of gas turbine assembly10enables auxiliary power engine12to be operated independently of propelling engine11, such that an operating speed auxiliary power engine12is independent of an operating speed of core engine13. As such, auxiliary power engine12may operated during non-operational periods of core engine13, and moreover, may be used to provide power necessary to start operation of engine11.

Operation of auxiliary power engine12facilitates improving surge margin of engine11by bleeding airflow52as needed, such that altitude, installation, or distortion effects may be overcome. Moreover, by removing high pressure extraction, auxiliary power engine12also facilitates improving an operating performance of core engine13while generating significant power. Additionally the hydro mechanical or digital controls of propelling engine11and auxiliary power engine12are arranged to mutually exchange operational status and performance parameter values (pressure, temperature, RPM, etc) from one to the other.

FIG. 2is a partial schematic view of an alternative embodiment of gas turbine engine assembly10. Specifically, the engine assembly shown inFIG. 2is the same engine assembly shown inFIG. 1, with the exception of a few component changes, described in more detail below. As such, components shown inFIG. 2that are identical to components illustrated inFIG. 1are identified inFIG. 4using the same reference numerals used inFIG. 1. More specifically, in the embodiment illustrated inFIG. 2, engine assembly10includes a control valve assembly100that facilitates controlling airflow54channeled towards auxiliary power engine12.

In the exemplary embodiment, control valve assembly100includes a pair of modulating or control valves102and104that are operatively coupled to control system62. Specifically, in the exemplary embodiment, control valve102is known as a low pressure source control valve, and control valve104is known as a high pressure source control valve. Valves102and104work in cooperation, as described in more detail below, to facilitate controlling a temperature, density, and/or pressure of auxiliary airflow54channeled to auxiliary power engine12.

Control valve assembly100is coupled in flow communication between propelling engine11and auxiliary power engine12such that airflow54channeled to power engine12is routed through valve assembly100. In the exemplary embodiment, a back-flow control device106is coupled between propelling engine11and low pressure source control valve102to facilitate preventing back flow from control valve assembly100towards propelling engine11. In the exemplary embodiment, control device106is, but is not limited to being, a check valve assembly. Moreover, in the exemplary embodiment, control valve assembly100is coupled in flow communication with propelling engine11such that intercooler60is coupled in flow communication between propelling engine11and control valve104.

As described above, control valve assembly100is operatively coupled to control system62such that valve assembly100, and more specifically, valves102and/or104, are selectively operable to control airflow54channeled to auxiliary power engine12. Moreover, as described in more detail below, during engine operation control system62facilitates controlling the extraction location of airflow54, and thus facilitates controlling the pressure, density, and airflow54channeled to auxiliary power engine12. As such, control valve assembly100can be selectively adjusted to facilitate optimizing supply pressure, temperature, and density of airflow54, thus facilitating minimizing performance penalties associated with engine12and maximizing power output49.

For example, during operation at low altitudes, control system62is operable to ensure that auxiliary power engine12receives airflow54from a low-pressure extraction source, such as, but not limited to fan discharge31, such that airflow54flows through check valve106and low pressure control valve102prior to being introduced to engine12. During operation at high altitudes, control valve assembly100is adjusted to ensure that auxiliary power engine12receives airflow54from a high-pressure extraction source, such as, but not limited to compressor discharge35, such that airflow54flows through intercooler60and high pressure control valve104prior to being introduced to engine12. During operation at intermediate altitudes, auxiliary power engine12receives airflow54at an intermediate pressure such that airflow is blended from high- and low-pressure extraction sources through valves102and104.

Control system62facilitates controlling control valve assembly100to enable auxiliary power engine12to receive a low pressure/low temperature/low density airflow, a high pressure/high temperature/high density airflow, or an intermediate pressure/intermediate temperature/intermediate density airflow, based on several factors and/or engine operating characteristics. In one embodiment, such factors may include, but are not limited to including, auxiliary engine operability, demand for auxiliary engine power, propelling engine operability, and/or propelling engine efficiency.

When it is desired to operate auxiliary power engine12with a source of low pressure/low temperature/low density airflow, such airflow122may be extracted from a plurality of different extraction points within propelling engine11. For example, fan14is a multi-staged compressor and fan interstage bleed air124may be extracted from any fan stage based on pressure, temperature, and flow requirements of auxiliary engine12. Moreover, such airflow may be extracted from any location downstream from fan14as booster discharge air, booster inter-stage bleed air, or core drive fan discharge air. Other alternative extraction sources for such airflow may include, but are not limited to including, fan discharge air31or fan inter-stage bleed air124. Furthermore, in another alternative embodiment, ambient air30may be used as a source of low pressure/low temperature/low density airflow.

When it is desired to operate auxiliary power engine12with a source of high pressure/high temperature/high density airflow, such airflow52may be extracted from a plurality of different extraction points within propelling engine11. For example, as previously described, compressor interstage bleed air120may be extracted from any compressor stage based on pressure, temperature, and flow requirements of auxiliary engine12. Moreover, such airflow may be extracted at any location upstream from compressor16as booster discharge air, booster inter-stage bleed air, or core drive fan discharge air.

Control valve assembly100increases an operating flexibility of auxiliary power engine12and an overall efficiency of gas turbine engine assembly11. Specifically, control valve assembly100enables auxiliary power engine12to be operated independently of propelling engine11. Moreover, because valves102and104are selectively operable, airflow to auxiliary power engine12may be adjusted to facilitate optimizing supply pressure, temperature, and density, thus minimizing performance penalties and maximizing power output49. In addition, the selective operation of control valve assembly100enables low pressure air, at a lower performance penalty, to be used at low altitudes or when a reduced amount of auxiliary power output49is required, and enables high pressure air to be used at higher altitudes or when increased power output49is demanded. Furthermore, auxiliary engine air supply can also be selectively adjusted in cooperation with propelling engine inlet guide vanes, variable geometry, and a variable bypass injector82, to facilitate increasing stall margin, improving operability, and to facilitate reducing performance penalties and fuel burns.

The above-described modulating control valve assembly is cost-effective and facilitates increases shaft power production and turbine engine operating efficiency. The control valve assembly is coupled in flow communication between the propelling engine and the auxiliary engine to facilitate enhanced operation and control of airflow channeled to the auxiliary power engine. As such, the control valve assembly may be selectively adjusted to facilitate a small amount of high-pressure air taken from the main engine to enable a smaller engine to output power levels similar to those of sea level operation. As a result, the increased control of airflow directed to the auxiliary engine facilitates increased turbine power production from the auxiliary engine in a cost-effective and reliable manner.

Exemplary embodiments of gas turbine assemblies are described above in detail. The assemblies are not limited to the specific embodiments described herein, but rather, components of each assembly may be utilized independently and separately from other components described herein. For example, each turbine component and/or auxiliary turbine engine component can also be used in combination with other core engine and auxiliary turbine engine components.