Gas Turbine Engine Cooling System Control

Abstract

A method for operating a gas turbine engine is provided. The method includes: determining data representative of operation of a cooling system of the gas turbine engine during shutdown of the gas turbine engine, after shutdown of the gas turbine engine, or both; and modifying a start schedule of the gas turbine engine in response to the determined data representative of operation of the cooling system of the gas turbine engine.

Description

Technical Field

[0001] The present disclosure relates to a gas turbine engine having a cooling system (such as a reverse exhaust system) and a method of operating the same. Background Art

[0002] During normal operation, the temperature of gas turbine engine components is maintained within allowable limits by a plurality of cooling processes that transfer heat from the components to one or more radiators. When the engine is shut down, most cooling systems cease operation. Residual heat (i.e., "soakback") in certain engine components can raise the temperature of other engine components above allowable limits and further may unevenly heat other components, sometimes creating a "bow" in the components, also known as a "bow rotor".

[0003] Of particular concern is that carbon (or "coke") deposits can form in fuel-bearing components (including fuel nozzles) when hydrocarbon fuel (liquid or gas) is exposed to high temperatures in the presence of oxygen. Some known methods of mitigating coking include rotating the rotor after the engine is shut down (i.e., "motor driven") or purging the engine with forced air provided by an auxiliary power unit ("APU"), a ground power unit ("GPU"), or an air conditioning unit after shutdown.

[0004] Similarly, the problem of a bowed rotor is premature wear of seals and clearances, for example within the compressor section of a gas turbine engine, resulting in lower efficiency and more frequent maintenance. Some known methods of repairing a bowed rotor include relatively slowly driving the engine for a longer period of time before restarting the engine to redistribute heat and / or cool components.

[0005] One problem with these methods is that they require resources such as electricity, fuel, external equipment, and / or logistical support that may not be available or practical and may also increase the startup time of the gas turbine engine. Summary of the Invention

[0006] Aspects and advantages of the present invention will be set forth in part in the following description, or may be obvious from the description, or may be learned by practice of the present invention.

[0007] In one exemplary aspect of the present disclosure, a method for operating a gas turbine engine is provided. The method includes: determining data representing operation of a cooling system of the gas turbine engine during, after, or both during and after shutdown of the gas turbine engine; and modifying a startup schedule of the gas turbine engine in response to the determined data representing operation of the cooling system of the gas turbine engine.

[0008] With reference to the following description and the appended claims, these and other features, aspects, and advantages of the present invention will become better understood. The drawings incorporated in and forming a part of this specification illustrate various aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A complete and enabling disclosure of the present disclosure, including the best mode thereof, to one of ordinary skill in the art, is set forth in the specification, which makes reference to the drawings, in which:

[0010] Figure 1 is a cross-sectional schematic view of a gas turbine engine in accordance with an exemplary aspect of the present disclosure, including a reverse exhaust system in accordance with an exemplary aspect of the present disclosure.

[0011] Figure 2 is applicable to Figure 1 a schematic close-up cross-sectional view of an exemplary reverse exhaust system within a gas turbine engine.

[0012] Figure 3 is a schematic perspective view of a Figure 1 gas turbine engine mounted to an aircraft.

[0013] Figure 4 is a flow chart of a method for operating a gas turbine engine in accordance with the present disclosure.

[0014] Figure 5 is in accordance with Figure 4 a graph of certain parameters of an engine operated by the method.

[0015] Figure 6 is a control scheme in accordance with the present disclosure. DETAILED DESCRIPTION

[0016] Reference will now be made in detail to the present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar numerals in the drawings and the description refer to like or similar parts of the invention.

[0017] As used herein, the term "exemplary" is used to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, unless specifically stated otherwise, all embodiments described herein should be considered exemplary.

[0018] As used herein, the terms "first," "second," and "third" may be used interchangeably to distinguish one component from another and are not intended to denote the position or importance of a single component.

[0019] The terms "front" and "rear" refer to relative positions within a gas turbine engine or a vehicle, and refer to the normal operating attitude of the gas turbine engine or the vehicle. For example, for a gas turbine engine, "front" refers to a position closer to the engine inlet, and "rear" refers to a position closer to the engine nozzle or exhaust port.

[0020] The terms "upstream" and "downstream" refer to the relative direction with respect to the fluid flow in a fluid flow path. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows.

[0021] The terms "coupled", "fixed", "attached", etc. refer to direct coupling, fixing or attachment, as well as indirect coupling, fixing or attachment through one or more intermediate components or features, unless otherwise specified herein.

[0022] Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural references.

[0023] The approximating language used in this specification and the claims is used to modify any quantitative representation that can permit variation without resulting in a change in the basic function associated therewith. Thus, values modified by one or more terms, such as "about", "approximately", and "substantially", are not limited to the precise values specified. In at least some instances, the approximating language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to construct or manufacture the components and / or systems. For example, the approximating language may refer to within a margin of 1, 2, 4, 10, 15, or 20%. These approximating margins may be applied to a single value defining an endpoint of a numerical range and / or to the margin of the range between the endpoints.

[0024] Here and throughout the specification and claims, range limitations are combined and interchanged, and these ranges are identified and include all subranges subsumed therein, unless the context or language indicates otherwise. For example, all ranges disclosed herein include the endpoints, and the endpoints can be combined independently of each other.

[0025] In an exemplary aspect of the present disclosure, a method for operating a gas turbine engine is provided, whereby when operating an air cooling system after the gas turbine engine is shut down, specific data related to the operation of the air cooling system for the gas turbine engine is determined. The air cooling system can be a reverse exhaust system and can be configured to reduce or minimize coke formation, such as in the fuel nozzles of the burners of the engine, and can further be configured to reduce or minimize rotor bowing conditions within the engine. The determined data can be based on sensed data stored in the non-volatile memory of the engine controller prior to the shutdown of the engine controller. The determined data can indicate whether the air cooling system is operating normally, whether it has shut down prematurely, etc.

[0026] In certain aspects of the present disclosure, the method of the present disclosure may modify the start sequence of a subsequent start operation of a gas turbine engine based on data determined in relation to the operation of an air cooling system. For example, if the data indicates normal operation of the air cooling system, the modification may be to shorten the drive of the engine before accelerating the engine to the ignition rotational speed, which may indicate that the engine is being cooled normally and is not experiencing rotor bowing. In contrast, if the data indicates abnormal operation of the air cooling system, the modification may be to extend the drive of the engine before accelerating the engine to the ignition rotational speed, which may indicate that the engine is being cooled incorrectly and may be experiencing rotor bowing.

[0027] Referring now to the drawings, in which like numerals represent like elements throughout the several views, Figure 1 an exemplary gas turbine engine 10 is depicted that defines an axial direction A (and centerline axis 11) and a radial direction R. Although the example shown is a high bypass turbofan engine, the principles of the present invention also apply to other types of engines, such as low bypass turbofan engines, turbojet engines, turboprop engines, ducted fan engines, or open rotor engines, etc., and engines having any number of compressor turbine rotors.

[0028] The engine 10 includes a fan 12, a low pressure compressor (“LPC”) or booster 14, a high pressure compressor or “HPC” 16, a combustion section or burner 18, a high pressure turbine or “HPT” 20, and a low pressure turbine or “LPT” 22 arranged in a series flow relationship. The fan 12, LPC 14, and LPT 22 together define the low pressure system or low pressure spool of the engine 10. The HPC 16 and HPT 20 together define the high pressure spool of the engine 10. The high pressure spool and the burner 18 may be referred to as the “core” or “core engine”.

[0029] In operation, pressurized air leaving the HPC 16 is mixed with fuel in the combustor 18 and ignited, thereby generating combustion gases. The HPT 20 extracts some work from these gases and drives the HPC 16 via the high-pressure shaft 24. The combustion gases then flow into the LPT 22, which drives the fan 12 and the LPC 14 via the low-pressure shaft 26. As used herein, when fuel is supplied to the combustor and burned in the combustor, the engine 10 is considered to be "in operation", and the generated combustion gases drive at least the rotation of the core. As used herein, when fuel is not supplied to the combustor, the engine 10 is considered to be "off". It should be understood that "in operation" includes a variety of operating conditions with different rotor speeds and different thrust and / or power outputs. It should be understood that when no fuel is provided, one or more rotors of the engine 10 may rotate. This may occur, for example, because air flows through the engine 10 on the ground, relative wind flows through the engine during flight of the aircraft (i.e., "wind milling"), or due to rotation caused by torque applied from a starter or similar device. Rotating the engine 10 using a starter (pneumatic, hydraulic, electric, or other) or using an electric motor before igniting the engine 10 or before accelerating the engine to the ignition speed (to ignite the engine 10) may be referred to as "driving" the engine 10.

[0030] The HPC 16 includes multiple stages of rotating blades and stationary vanes, all surrounded by the compressor housing 28. The compressor housing 28 includes a compressor exhaust chamber 29 that is in fluid communication with the compressor flow path and in fluid communication with the exterior of the compressor housing 28 through at least one compressor exhaust port 30. The compressor exhaust chamber 29 may extend over the entire or a portion of the circumference of the compressor housing 28. It should be understood that different engines may include one or more exhaust ports, and a particular engine may or may not include an exhaust chamber of the type shown. As used herein, the term "compressor exhaust port" generally refers to a port, opening, plenum, or passage in the compressor housing 28 or other similar structure, such as a combustor housing (e.g., located downstream of the compressor and in direct or indirect fluid communication with the compressor flow path). The term "compressor exhaust port" may refer to an existing structure within the engine 10 or a newly added structure to accommodate the reverse exhaust system described herein.

[0031] One or more exhaust ducts 32 are connected to the compressor exhaust port 30 and are configured to direct the extracted air flow out of the HPC 16. The extracted air may be discharged for the purpose of controlling the compressor operating line, or may be specifically added for the purpose of introducing reverse exhaust cooling air, as described herein. Optionally, it may be used for purposes such as an environmental control system (“ECS”), pneumatic actuators, engine hot section cooling, and / or clearance control systems. The exhaust duct 32 may include an exhaust control valve 34 that is operable to move between an open and a closed position to control the flow through the compressor exhaust port 30.

[0032] The engine core is surrounded (i.e., contained) by a core cowl 36 or core nacelle that defines the inner boundary of a bypass flow path 38 through which fan bypass air flows. A ducted turbofan is shown that includes a fan 12 surrounded by a fan nacelle 37 that is spaced from the core cowl 36 and defines the outer boundary of the bypass flow path 38. In this example, the bypass flow path 38 may also be referred to as a “fan duct”.

[0033] However, it should be understood that in other exemplary embodiments, the engine 10 may not include a fan nacelle 37 and instead may be an “open rotor” turbofan engine (or other type of engine). With this configuration, the bypass flow path 38 will be defined only by the outer surface of the core cowl 36.

[0034] The space inside the core cowl 36 and outside the core air flow path is generally referred to as the “lower cowl space” 40. In practice, the lower cowl space 40 may be discharged to the external environment, for example, through a vent 41 (schematically shown in Figure 1 ). For the purposes of this disclosure, things referred to as being inside the engine are those located within the space surrounded by the fan nacelle 37 or the core cowl 36 (in the case of an open rotor engine, for example, where the fan nacelle 37 does not exist).

[0035] The engine 10 may optionally incorporate a variable bleed valve (“VBV”) system for controlling the LPC stall margin. The VBV system includes one or more variable bleed valves 42 mounted within the fan hub frame 44. The variable bleed valve 42 may be opened during low power operation of the engine 10, such as at idle, to discharge a portion of the compressed air. The variable bleed valve 42 is closed during high power operation of the engine 10, such as during cruise or takeoff, as the bleed is no longer required. When the variable bleed valve 42 is open, air flows from the LPC flow path through the fan hub frame 44 and into, for example, the bypass passage 38 or other bypass spaces outside the nacelle 37. In the example shown, the engine 10 includes at least one bypass duct 46 that defines an air flow path from the fan hub frame 44 to an exhaust vent 48 that communicates with the bypass flow path 38.

[0036] Still referring to Figure 2 ,a close-up view of, for example Figure 1 HPC 16 and burner 18 is provided, the burner 18 including a plurality of fuel nozzles 50 that are supplied with pressurized liquid fuel during engine operation. The fuel nozzles 50 are connected to a fuel system 52 that is operable to supply a pressurized liquid fuel stream at a varying flow rate according to operating requirements. As schematically depicted, the fuel system 52 supplies fuel through a fuel valve 54 coupled to a fuel conduit 56 that in turn couples to the fuel nozzles 50. In some embodiments, the fuel nozzles 50 and the fuel system 52 can implement more than one independent fuel flow circuit (e.g., a pilot circuit and a main circuit).

[0037] It should be understood that each fuel nozzle 50 can generally be a metal block including many small channels and orifices. When hydrocarbon fuel is exposed to high temperatures in the presence of oxygen, carbon (or “coke”) deposits can form on the fuel nozzle 50. This process is referred to as “coking” and depends, for example, on the oxygen content of the fuel, and coking can generally be a risk when the temperature exceeds about 170 degrees Celsius (350 degrees Fahrenheit).

[0038] During engine operation, fuel and compressed air flow through the fuel nozzle 50, and the fuel nozzle 50 is bathed in an external flow of relatively cold compressor discharge air. All of these flows carry heat away from the fuel nozzle 50, keeping the fuel temperature relatively low. More specifically, the relatively large volume of fuel passing through the fuel nozzle 50 mainly keeps the temperature of the fuel nozzle 50 at a relatively low temperature.

[0039] When engine operation stops, a certain volume of fuel can remain in the fuel nozzle 50 and can be heated to the coking temperature. A small amount of coke that disrupts the fuel flow through the orifices in the fuel nozzle 50 can make a large difference in fuel nozzle performance.

[0040] It should also be understood that when engine operation stops, the flow of compressor discharge air also stops. For example, after the engine is shut down (when engine operation stops), various turbine section components that are always exposed to relatively hot combustion gases may remain relatively hot. Heat from these relatively hot components can conduct along the high voltage spool and into the burner 18. Heat can also move generally upward. When the compressor discharge air is flowing, the air flow can maintain a relatively constant temperature in the circumferential direction of the engine. However, once the air flow stops, a thermal mismatch can form between the upper and lower portions of the spool (because the compressor discharge air no longer provides a constant circumferential temperature gradient), resulting in “bending” in the spool, also known as “rotor bending”.

[0041] The inventors' analysis and testing have shown that if an air stream of appropriate pressure and flow rate is supplied to the compressor section, the combustion section, or both (e.g., returned through the compressor exhaust port 30) after the engine 10 is shut down, this stream ("reverse exhaust") can preferentially flow downstream from the HPC 16 and provide cooling for the fuel nozzles 50, thereby reducing or preventing fuel nozzle coking. Additionally, such a stream can provide cooling for components vulnerable to rotor bowing to reduce the amount of rotor bowing in the engine 10. For example, at least a portion of this reverse exhaust can flow through the compressor section to reduce rotor bowing.

[0042] In particular, for the depicted exemplary embodiment, the gas turbine engine further includes an air cooling system that is selectively in fluid communication with the compressor section, the combustion section, or both, for providing a cooling air stream over the fuel nozzles 50 during certain operations, such as during or after the engine 10 is shut down. For the illustrated embodiment, the air cooling system is in fluid communication with an exhaust component (specifically, the compressor exhaust port 30 of the illustrated embodiment), and thus can be referred to as a reverse exhaust system 60.

[0043] However, it should be understood that in other embodiments, the air cooling system can be any other suitable air cooling system for generating a cooling air stream that enters or passes through the compressor section, the combustion section, or both to reduce coking and / or rotor bowing.

[0044] More specifically, as Figure 2 shown, the reverse exhaust system 60 can be used to provide a cooling air stream or reverse exhaust stream over the fuel nozzles 50 during or after the shutdown of the engine 10.

[0045] The reverse exhaust system 60 includes a cooling duct 62 disposed within the engine 10. It can be installed, for example, entirely or partially within the lower cowl space 40. In particular, for the illustrated embodiment, it is fully installed within the lower cowl space 40, "inside" the lower cowl space 40. The cooling duct 62 defines an inlet 64 that is in fluid communication with a cooling air source and an outlet 66 that is in fluid communication with the compressor section (such as the HPC 16), the burner, or both. In particular, for the illustrated embodiment, the cooling duct 62 is in fluid communication with the HPC 16 and the burner 18 via the compressor exhaust port 30. The complete cooling duct 62 can be constructed from, for example, tubes, connectors, fittings, and the like.

[0046] In Figure 2 the embodiment, the inlet 64 is fluidly connected in communication with the bypass duct 46. In Figure 2 the embodiment, the outlet 66 is connected to an existing exhaust duct 32, and the existing exhaust duct 32 in turn is connected to the compressor exhaust port 30.

[0047] However, in other embodiments, the cooling duct 62 can be configured in any other suitable manner to provide a reverse exhaust flow over the fuel nozzle 50. For example, the cooling duct 62 can be directly connected to a dedicated opening in the fairing 36, can receive ambient air within the lower fairing space 40, etc. For example, as shown in dashed lines, the cooling duct 62 may not extend into the bypass duct 46, but rather the cooling duct 62 can simply lead to the lower fairing space 40, allowing air from the lower fairing space 40 to be directly drawn into the valve assembly 68 rather than from the bypass duct 46. With this configuration, the inlet 64 can be correspondingly exposed to the lower fairing space 40.

[0048] Still referring to Figure 2 , the cooling duct 62 incorporates a valve assembly 68 that includes one or more valves operable to control the airflow between the inlet 64 and the outlet 66. Two or more valves can be used to provide redundancy, and / or to monitor or control the airflow through the duct 62. In this example, a first valve 70 and a second valve 72 are used in series, with the first valve 70 closest to the outlet 66. In other words, the first valve 70 and the second valve 72 are in a "series fluid communication" manner, which means that the fluid flow passes through one valve before encountering the other valve. "Serial fluid communication" is contrasted with "parallel fluid communication".

[0049] In the example shown, the first valve 70 is a check valve that can be biased passively towards the open position by, for example, a spring, stored fluid pressure, weight, or other suitable mechanism and is arranged to allow airflow in the direction from the inlet 64 towards the outlet 66, but to block airflow in the opposite direction. It should be understood that even in the closed position, the valve may exhibit some fluid leakage. Thus, in addition to the inherent leakage, the valve operating in the closed position to prevent airflow can be described as "substantially preventing flow".

[0050] In the example shown, the second valve 72 is a control valve having a flow control element (e.g., a gate, a baffle, a ball, etc.) movable between an open and a closed position. In the open position, the second valve 72 allows airflow between the inlet 64 and the outlet 66. In the closed position, the second valve 72 blocks airflow between the inlet 64 and the outlet 66.

[0051] A variety of types of control valves can be used. In one example, the control valve can be combined with or coupled to an actuator 74 that provides power to the flow control element of the valve. Examples of suitable types of actuators include pneumatic, hydraulic, or electric devices.

[0052] In one example, the control valve can be of a type where a spring or similar element biases the control valve towards an open position, and fluid pressure acts against the spring to move the valve towards a closed position. Suitable fluids can include, for example, compressed air, pressurized oil, or pressurized fuel. In one example, the control valve can be coupled to the fuel system 52 described above (see Figure 1 ), such that the pressurized fuel can be supplied to the valve during engine operation. Thus, when the engine 10 is operating, the fuel pressure tends to keep the valve closed. This type of valve can be referred to as a fluid pressure responsive passive valve, such as a "passive fuel valve".

[0053] In this specific example where one of the first valve 70 and the second valve 72 is a check valve and the other of the first valve 70 and the second valve 72 is a control valve, either valve can be placed in an upstream or downstream position relative to the other valve. However, check valves tend to close more reliably when subjected to a greater pressure differential. The first valve 70 will inherently be exposed to a higher air pressure, closer to the compressor discharge port 30. Thus, the first valve 70 can be a check valve.

[0054] The cooling duct 62 includes a cooling blower 76 between the valve assembly 68 and the inlet 64. The cooling blower 76 can be any device operable to blow, pump, or move a cooling air stream from the inlet 64 towards, to, or to the outlet 66. In the example shown, the cooling blower 76 includes a rotor 78 with a plurality of fan blades. Optionally, the blower 76 can be located at the inlet 64, within the inlet 64, or close to the inlet 64, and away from the valves 72, 70.

[0055] The power source for operating the cooling blower 76 can be mechanical, hydraulic, pneumatic, or electric. In the example shown, the rotor 78 of the blower is coupled to an electric motor 80. In one example, the electric motor 80 can be an alternating current induction motor or a direct current motor.

[0056] The cooling blower 76 can be sized to provide sufficient exhaust pressure and flow rate for the cooling process described in more detail below. As an example, the cooling blower 76 can be sized to produce an air flow on the order of about 0.05 kg / s (0.1 lb / s) to about 0.23 kg / s (0.5 lb / s) at about 0.69 kPa (0.1 psi) to about 6.9 kPa (1 psi). In one exemplary end use, the cooling blower 76 can be sized to produce an air flow on the order of about 0.12 kg / s (0.25 lb / s) at about 3.4 kPa (0.5 psi).

[0057] The operation of the reverse exhaust system 60 is generally as follows. When the engine 10 is running, the reverse exhaust system 60 is not in operation. A portion of the cooling air duct 62 will be pressurized by the hot air from the compressor exhaust port 30. The valve assembly 68 will block most of the flow from the outlet 66 to the inlet 64. As described above, some valve leakage is expected to occur. Any leakage will pass through the cooling blower 76, the inlet 64, and in Figure 2 the example of, through the bypass duct 46 and the vent 48.

[0058] After the engine is shut down, backflow may occur, which may heat the fuel nozzle 50 to an unacceptable temperature, and some other components of the engine 10 may experience rotor bowing. The reverse exhaust system 60 can be used to direct the cooling air flow from the inlet 64 through the cooling duct 62, through the outlet 66, and into the compressor exhaust port 30. Subsequently, the cooling air can pass through the fuel nozzle 50 and other components of the core to reduce their respective temperatures and reduce or prevent coking, and reduce or prevent rotor bowing. Basically, during or after the time when the engine 10 is shut down, the reverse exhaust system 60 is applied by (1) operating the cooling blower 76 and (2) opening one or more valves of the valve assembly 68. For example, the reverse exhaust system 60 can be operated after the engine 10 is shut down and before the engine 10 is subsequently started.

[0059] As a possible alternative, the reverse exhaust system 60 can be used to direct the cooling air flow from a downstream portion of the engine 10, through the compressor exhaust port 30, through the outlet 66, through the cooling duct 62, and out through the inlet 64. In this sense, the so-called "reverse exhaust" system 60 will be used to cause the direction of air movement through the exhaust port to be the same as the direction of the air flow through the exhaust port during flight. This can be achieved as described above by ensuring that all valves are open or otherwise configured to allow flow in that direction and operating the cooling blower 76 to move air in the opposite direction. In other words, the cooling blower 76 can be used to "draw in" air from the engine 10 rather than "blow" it into the engine 10.

[0060] However, it should be understood that in other exemplary embodiments, the engine 10 may include any other suitable air cooling system for providing a cooling air flow over the fuel nozzle 50 or otherwise capable of cooling the fuel nozzle 50 and other components vulnerable to rotor bowing. For example, the air cooling system may be configured to provide cooling air from any suitable location (e.g., ambient, lower cowl 40, compressor section, dedicated cooling air flow source, etc.). Additionally or alternatively, the air cooling system may be configured to utilize the cooling air flow to reduce the temperature of the fuel nozzle 50 or other components prone to coking due to backflow (e.g., certain fuel lines), components causing a bowed rotor, etc., in any other suitable manner. For example, the air cooling system may be configured to provide a cooling air flow directly over the component, may be configured to cool the component through an intermediate component (e.g., a cooling component thermally coupled to the component to be cooled), etc. Additionally or alternatively, the air cooling system may be located in any other suitable location to perform the functions described herein.

[0061] Moreover, many arrangements are possible for the control and operation of the air cooling system / reverse exhaust system 60. In particular, also returning to Figure 1 , the exemplary gas turbine engine 10 further includes an engine controller 82, such as a full authority digital engine control (“FADEC”) controller or an electronic engine controller (“EEC”). The engine controller 82 is configured to receive data sensed from one or more sensors and make control decisions, for example, based on the received data. In the depicted embodiment, the engine 10 includes sensors for sensing data representative of engine speed, engine temperature, etc. In particular, the illustrated exemplary engine 10 includes a first sensor 84 for sensing data representative of the rotational speed of the low speed spool, a second sensor 86 for sensing data representative of the rotational speed of the high speed spool, a third sensor 88 for sensing data representative of the engine temperature (especially the turbine inlet temperature), and a fourth sensor 90 for sensing data representative of another engine temperature (especially the exhaust temperature). It should be understood that each of these sensors may be a single sensor or a sensor array, may be any suitable type of sensor for sensing data representative of a parameter, and may further be located at any suitable location for sensing data representative of a parameter.

[0062] With particular reference to the operation of controller 82, in at least some embodiments, controller 82 may include one or more computing devices 92. The computing device 92 may include one or more processors 92A and one or more memory devices 92B. The one or more processors 92A may include any suitable processing device, such as a microprocessor, a microcontroller, an integrated circuit, a logic device, and / or other suitable processing devices. The one or more memory devices 92B may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, hard disk drives, flash drives, and / or other memory devices.

[0063] The one or more memory devices 92B may store information accessible by the one or more processors 92A, including computer-readable instructions 92C executable by the one or more processors 92A. The instructions 92C may be any set of instructions that, when executed by the one or more processors 92A, cause the one or more processors 92A to perform operations. In some embodiments, the instructions 92C may be executed by the one or more processors 92A to cause the one or more processors 92A to perform operations, such as any of the operations and functions for which controller 82 and / or computing device 92 are configured, such as the operations for operating gas turbine engine 10 and / or cooling system / reverse exhaust system 60 as described herein (e.g., method 300), and / or any other operations or functions of the one or more computing devices 92. The instructions 92C may be software written in any suitable programming language or may be implemented in hardware. Additionally, and / or optionally, the instructions 92C may be executed in logically and / or virtually separate threads on processor 92A. The memory device 92B further stores data 92D accessible by processor 92A. For example, the data 92D may include data representing power flow, data representing engine / aircraft operating conditions, and / or any other data and / or information described herein.

[0064] The computing device 92 may further include a network interface 92E for communicating, for example, with other components of gas turbine engine 10, an aircraft including the gas turbine engine, and the like. For example, in the depicted embodiment, as described above, gas turbine engine 10 includes one or more sensors 84, 86, 88, 90 for sensing data representing one or more parameters of the gas turbine engine. The controller 82 is operatively coupled to the one or more sensors, such as via network interface 92E, such that the controller 82 may receive data representing various operating parameters sensed by the one or more sensors during operation. Additionally, for the illustrated embodiment, the controller 82 is operatively coupled to, for example, an air cooling system / reverse exhaust system 60. In this manner, the controller 82 may be configured to operate the reverse exhaust system 60 in response to, for example, data sensed by the one or more sensors.

[0065] The network interface 92E may include any suitable components for interfacing with one or more networks, including, for example, transmitters, receivers, ports, controllers, antennas, and / or other suitable components.

[0066] The techniques discussed herein refer to computer-based systems and to operations performed by computer-based systems and information transmitted and received by computer-based systems. Those of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for many possible configurations, combinations, and divisions of tasks and functions among components and between components. For example, the processes discussed herein may be implemented using a single computing device or a combination of multiple computing devices. Databases, memories, instructions, and applications may be implemented on a single system or distributed across multiple systems. Distributed components may operate sequentially or in parallel.

[0067] Now briefly referring to Figure 3 aircraft 100, a perspective view of aircraft 100 is provided. Aircraft 100 may incorporate the exemplary engine 10 and reverse exhaust system 60 described above. Engine 10 in combination with reverse exhaust system 60 may be installed in an aircraft 100 having at least one power source such as a battery and inverter 102, an auxiliary power unit 104, a connection to a ground power unit 106 or other ground-based power source, or another engine 10 having a generator.

[0068] In one example, aircraft 100 includes an electronic aircraft controller 108 in data communication with the engine controller 82 described above (see Figure 1 ), and also includes a controllable power connection 110 to an air cooling system / reverse exhaust system 60, including, for example, a cooling blower 76. Aircraft controller 108 may have connections to various inputs such as cockpit switch positions and / or sensors such as an outside air temperature (OAT) probe 112 or a wheel-on weight sensor 114. Aircraft controller 108 may be configured in a manner similar to the exemplary engine controller 82 shown above with reference to Figure 1 .

[0069] Reference is now made below to Figure 4 describe various control methods according to exemplary aspects of the present disclosure.

[0070] In particular, reference is now made to Figure 4 , a method 200 for operating a gas turbine engine is provided. In certain exemplary aspects, method 200 may be associated with the above reference to Figures 1 to 3One or more of the described exemplary aircraft, engines, air cooling systems (e.g., reverse exhaust systems), etc. may be used together. However, in other exemplary aspects, the exemplary method 200 may be used with any other suitable aircraft, engine, air cooling system, etc.

[0071] For Figure 4 an exemplary aspect of the method 200 depicted in, the method 200 generally includes: at (202), determining data representative of the operation of an air cooling system of a gas turbine engine during, after, or both during and after shutdown of the gas turbine engine; and at (204), modifying a startup schedule of the gas turbine engine in response to the determined data representative of the operation of the air cooling system of the gas turbine engine.

[0072] The term "startup schedule" generally refers to the process of starting up a gas turbine engine, and in some exemplary aspects, refers to the amount of time to rotate the engine with a starter or other electric motor before increasing the rotational speed of the engine to a light-off rotational speed.

[0073] In particular, for Figure 4 an exemplary aspect of the method 200 depicted in, the air cooling system can be any suitable air cooling system for providing a cooling air flow to components of the gas turbine engine that are configured to contain fuel during or after engine shutdown, one or more components vulnerable to rotor bowing, or both. More specifically, for Figure 4 an exemplary aspect of the method 200 depicted in, the air cooling system is a reverse exhaust system configured to provide a cooling air flow over components of the burner of the gas turbine engine during operation of the reverse exhaust system. For example, the reverse exhaust system can be configured to provide a cooling air flow over one or more fuel nozzles of the burner of the gas turbine engine during operation of the reverse exhaust system.

[0074] More specifically, it should be understood that prior to determining data representative of the operation of the air cooling system / reverse exhaust system at (202) and modifying the startup schedule at (204), in the exemplary aspect of the method 200 depicted in Figure 4 the method 200 additionally includes at (206), after shutdown of the gas turbine engine, starting operation of the reverse exhaust system. Starting operation of the reverse exhaust system at (206) can be at least partially in response to one or more ambient / surrounding environmental condition parameters and engine parameters, and further can be a command from an engine controller.

[0075] For example, for the depicted exemplary aspect, method 200 further includes, at (208), determining data representative of a bleed-back temperature indicator parameter. The bleed-back temperature indicator parameter can be any suitable parameter for indicating that the expected temperature of one or more components configured to hold fuel after engine shutdown will exceed a predetermined threshold. The predetermined threshold can be a temperature threshold at which any fuel in the component may be coked. For example, the bleed-back temperature indicator parameter can be an ambient condition parameter, such as an ambient temperature parameter, an ambient altitude parameter, etc. Additionally or alternatively, the bleed-back temperature indicator parameter can be an engine temperature parameter, such as an exhaust temperature, a compressor outlet temperature, a turbine inlet temperature, etc. The bleed-back temperature indicator parameter can be additionally or alternatively based on a software heat transfer model utilizing one or more of the above parameters and / or other data, etc.

[0076] For the depicted exemplary aspect, starting operation of the reverse exhaust system at (206) further includes, at (210), starting operation of the reverse exhaust system after the gas turbine engine is shut down in response to data representative of the bleed-back temperature indicator parameter determined at (208). For example, the data determined at (208) can include data representative of the bleed-back temperature indicator parameter exceeding a predetermined threshold, and method 200 can start operation of the reverse exhaust system in response to such data.

[0077] Also by way of example, for the depicted exemplary aspect, method 200 further includes, at (212), determining data representative of engine operating parameters. The engine operating parameters can be any suitable parameters for indicating that the engine and / or the aircraft containing the engine is in a desired operating condition for starting the reverse exhaust system. For example, the data representative of the engine operating parameters can be data representative of the engine being on or off (e.g., from a user / operator switch within the aircraft cockpit, or an electronic signal), the rotational speed of one or more components of the engine, a wheel-on weight sensor reading (e.g., from wheel-on weight sensor 114 to ensure shutdown is not an in-flight shutdown), etc. Additionally or alternatively, the data representative of the engine operating parameters can include data representative of various other conditions of the engine's systems (such as an open / closed indicator on the engine's reverse exhaust valve).

[0078] In one exemplary aspect of method 200, as will be described in more detail below with reference to, for example Figure 5 In certain exemplary aspects, the data representative of the engine operating parameters can include data representative of the rotational speed of a shaft of the engine, such as the high-pressure shaft of the engine. The data representative of the engine operating parameters can include data representative of the decay rate of the rotational speed of a shaft of the engine and / or data representative of the rotational speed being below a predetermined threshold (e.g., 10% of the engine rated rotational speed, such as 5% of the engine rated rotational speed).

[0079] Utilizing such exemplary aspects, it should be understood that initiating operation of the reverse exhaust system at (206) further includes, at (214), initiating operation of the reverse exhaust system after the gas turbine engine is shut down in response to data representative of engine operating parameters determined at (212). For example, in some exemplary aspects, such as where the data representative of engine operating parameters can include data representative of the decay rate of the rotational speed of the engine's shaft and data representative of the rotational speed being below a predetermined threshold, initiating operation of the reverse exhaust system at (214) can include initiating operation of the reverse exhaust system after a determined amount of time after the engine falls below the predetermined threshold. The determined amount of time can be a preset time (e.g., a predetermined amount of time), or alternatively, can be based on the decay rate of the rotational speed of the shaft.

[0080] After initiating operation of the reverse exhaust system at (206), method 200 further includes, at (216), operating the reverse exhaust system for a certain amount of time. Operating the reverse exhaust system at (216) can include operating the reverse exhaust system for a determined amount of time (e.g., based on one or more sensed parameters, based on a bleed temperature indicator parameter (e.g., high ambient temperature, longer operation; higher engine temperature, longer operation; higher altitude, longer operation), etc.), or alternatively, can include operating the reverse exhaust system for a predetermined amount of time (e.g., 30 minutes, 60 minutes, 90 minutes, etc.). Operating the reverse exhaust system at (216) includes providing, at (217), a cooling air flow through the high-pressure compressor of the gas turbine engine, the combustion section of the gas turbine engine, or both.

[0081] For example, in some aspects, providing the cooling air flow at (217) can include providing a cooling air flow through the high-pressure compressor, the combustion section, or both, and over one or more components of the gas turbine engine configured to hold fuel after the gas turbine engine is shut down.

[0082] However, alternatively, providing the cooling air flow at (217) can include extracting air from the high-pressure compressor, the combustion section, or both to create a cooling air flow over one or more components of the gas turbine engine configured to hold fuel after the gas turbine engine is shut down. For example, the one or more components can be one or more fuel nozzles of the combustion section of the gas turbine engine.

[0083] It should be noted that, in certain exemplary aspects of method 200, method 200 may further include terminating the operation of the reverse exhaust system before determining a time amount or before a predetermined time amount. Due to restarting the gas turbine engine, disconnecting the gas turbine engine from a power source (such as a ground power source), instructions for maintenance operations to terminate, etc., the reverse exhaust system may be terminated before determining a time amount or before a predetermined time amount. For such exemplary aspects, method 200 may save data representing the time amount of the operation of the reverse exhaust system, which may represent the operation of the reverse exhaust system (and, for example, be used at step (202)).

[0084] It should be understood that, in at least some exemplary aspects, the engine controller of an engine including a reverse bleed air system may be configured to power down after a certain time amount after the engine is shut down. In certain exemplary aspects, this time amount may be less than the time amount required to operate the reverse exhaust system. In this way, it should be understood that for the exemplary aspects of method 200 described, operating the reverse exhaust system for a certain time amount at (216) further includes, at (218), powering the reverse exhaust system with a power source external to the gas turbine engine. For example, in certain exemplary aspects, the power source external to the gas turbine engine may be an electrical energy storage unit of the aircraft (such as a battery pack), a ground power system, an auxiliary power unit of the aircraft, another engine coupled to the aircraft, or an electric motor driven by another engine of the aircraft, etc.

[0085] More specifically, for Figure 4 the exemplary aspects of method 200 depicted in, it should be understood that method 200 further includes, at (220), after the gas turbine engine is shut down and after the operation of the reverse exhaust system starts at (206), shutting down the engine controller of the gas turbine engine after a first time amount. For such exemplary aspects, operating the reverse exhaust system for a certain time amount at (216) further includes, at (222), operating the reverse exhaust system for a second time amount after the gas turbine engine is shut down, where the second time amount is greater than the first time amount. For example, the second time amount may be at least 50% greater than the first time amount (such as at least 100% greater than the first time amount, such as five times greater, such as 100 times greater).

[0086] As simply noted above, method 200 further includes, at (202), determining data representing the operation of the gas turbine engine during and / or after the gas turbine engine is shut down. In certain exemplary aspects, the data representing the operation of the reverse exhaust system determined at (202) may include data representing the correct operation of the reverse exhaust system.

[0087] For example, in some exemplary aspects, the data determined at (202) representative of the operation of the reverse exhaust system can include data representative of the engine temperature at a first time after starting the reverse exhaust system at (206), and data representative of the engine temperature at a second time after starting the reverse exhaust system at (206). The second time can be after the first time. Further, the first time can be a relatively short period of time after starting the reverse exhaust system at (206), and the second time can be a relatively short period of time before turning off the engine controller at (220). "Relatively short period of time" can refer to an amount of time less than or equal to about three minutes (such as less than or equal to about one minute, such as less than or equal to about 30 seconds, such as less than or equal to about 10 seconds).

[0088] For such exemplary aspects, the data determined at (202) representative of the operation of the reverse exhaust system can further include data representative of the difference between the engine temperature at the first time and the engine temperature at the second time. For example, when determining the data representative of the operation of the reverse exhaust system at (202), the method can determine the slope between the engine temperature at the first time and the engine temperature at the second time to determine whether the engine temperature is increasing or decreasing. If the engine temperature is increasing, this can indicate abnormal operation of the reverse exhaust system, while if the engine temperature is decreasing, this can indicate normal operation of the reverse exhaust system. The engine temperature can be, for example, the exhaust temperature, the turbine inlet temperature, the compressor outlet temperature, etc.

[0089] Also as described above, method 200 further includes, at (204), modifying the start schedule of the gas turbine engine in response to the data determined at (202) representative of the operation of the reverse exhaust system of the gas turbine engine. For the depicted exemplary aspects, modifying the start schedule of the gas turbine engine at (204) further includes reducing the drive time of the gas turbine engine at (224).

[0090] It should be understood that when the engine experiences rotor bowing, it may be necessary to "drive" the engine for a certain amount of time before starting the remaining start sequence of the gas turbine engine. In this way, it should be understood that driving generally refers to rotating one or more components of the engine, such as with a starter or other electric motor, to allow the bowed components to dissipate heat, thereby reducing component bowing. The time consumed during the driving process depends on the degree of rotor bowing. However, if it is determined that the reverse exhaust system has operated normally, this may indicate that the components are not "bowed" or will not be bowed as much as in other cases, which can reduce the drive time of the engine before starting the remainder of the start sequence of the gas turbine engine.

[0091] It should be understood that, in other exemplary aspects, method 200 may additionally or optionally determine, at (202), data indicating that the reverse exhaust system is not operating correctly or is not operating at 100% effectiveness. For such exemplary aspects, modifying the startup schedule of the gas turbine engine at (204) may additionally or optionally include increasing the drive time of the gas turbine engine within the startup sequence.

[0092] However, it should be understood that the exemplary aspects of method 200 described above are only examples. Figure 4 In other exemplary aspects, any other suitable air cooling system may be used in place of the reverse exhaust system discussed, and further, in other exemplary aspects, the air cooling system may be configured to provide a cooling air flow to additional or optional components of the gas turbine engine. For example, in other exemplary aspects, the air cooling system may be a system for providing a forced air flow through the main air flow path of the engine, for example, through an inlet of the engine (e.g., a separate fan located at the front end of the gas turbine engine, at the rear end of the gas turbine engine, or both). Also as an example, in other exemplary aspects, the components cooled by the air cooling system may be any other suitable components configured to hold fuel after the gas turbine engine is shut down, for example, one or more fuel lines, auxiliary combustion devices, or burners, etc.

[0093] Now referring to Figure 5 , a graph 300 is provided that depicts the rotational speed of the gas turbine engine and the engine temperature of the gas turbine engine during a period of time from when the gas turbine engine is shut down to a subsequent startup of the gas turbine engine. An exemplary operation of method 300 is described below with reference to graph 300 of Figure 5 .

[0094] It should be understood that graph 300 generally includes a Y-axis representing rotational speed (Y-axis 302 on the left side of graph 300) and a Y-axis representing engine temperature (Y-axis 304 on the right side of graph 300) and an X-axis 306 depicting time. The first line 308 shown represents the rotational speed of the engine during that period of time, and the second line 310 shown represents the engine temperature during the same period of time. The rotational speed may be the shaft speed of the gas turbine engine, such as the high-pressure shaft speed or the low-pressure shaft speed. The engine temperature may be the exhaust temperature, the turbine inlet temperature, the compressor outlet temperature, etc.

[0095] At T0, the gas turbine engine is shut down. Shutting down the engine can include, for example, an operator of the gas turbine engine / aircraft including the gas turbine engine operating a switch or other control mechanism within the engine cockpit. Further, shutting down the engine can include closing the fuel flow to the burners of the gas turbine engine. After the gas turbine engine is shut down, the rotational speed of the gas turbine engine decreases. The engine temperature will initially decrease similarly, but may start to climb due to the heat stored within the various components of the gas turbine engine, assuming the thermal mass of these components is relatively high and considering that the engine speed is slowing and the airflow through the gas turbine engine is correspondingly reduced.

[0096] At or around shutdown / T0, the aircraft controller, the engine controller, or both can provide a command to the air cooling system to activate the air cooling system / reverse exhaust system. In particular, for the illustrated embodiment, the air cooling system can be a reverse exhaust system. In particular, for the various aspects shown, this command to activate the reverse exhaust system can initially be a fail-safe launch command from the engine controller or the aircraft controller to start the operation of the reverse exhaust system after a predetermined amount of time, if the reverse exhaust system is not already operating.

[0097] More specifically, for Figure 5 the illustrated graph 300, the engine controller can further determine when the rotational speed of the gas turbine engine reaches a predetermined level, as shown at T1, which can be, for example, 10% or less of the rated speed of the gas turbine engine, such as 5% or less of the rated speed of the gas turbine engine. This predetermined level is equal to or higher than the level at which the sensor or other mechanism that determines the rotational speed typically cuts off.

[0098] After determining that the engine has reached the predetermined level, the engine controller can wait a certain amount of time before starting the operation of the reverse exhaust system at T2. In particular, the engine controller can send a command to the aircraft controller to provide power to the cooling system for, for example, a determined amount of time or a predetermined amount of time. In response, the aircraft controller can be programmed to provide power to the reverse exhaust system for the specified amount of time and then turn off the power.

[0099] The amount of time between T1 and T2 can be based on the decay rate of the rotational speed of the gas turbine engine and / or one or more known configurations of the gas turbine engine. For example, if the gas turbine engine includes, for example, a hydraulic pump or other accessory system coupled to the high-pressure spool, these components may increase the amount of resistance on the high-pressure spool (resulting in a faster decrease in rotational speed). In such a case, the amount of time between T1 and T2 can be reduced. The amount of time between T1 and T2 can be, for example, less than or equal to five minutes (such as less than or equal to three minutes, such as less than or equal to two minutes, such as less than one minute, such as less than or equal to 30 seconds, such as greater than or equal to 5 seconds).

[0100] During typical operation, the reverse exhaust system can operate for a certain amount of time after starting operation at T2. In particular, for the illustrated embodiment, the reverse exhaust system is configured to operate from T2 to T6. It is noted that the engine controller is typically configured to be off for a certain amount of time after shutting down the gas turbine engine at T0, and this amount of time is less than the time from T0 to T6. In Figure 5 the graph 300 depicted in, the engine controller is configured to be off at T5. As described above, it will thus be understood that operating the reverse exhaust system can include providing power from a power source external to the gas turbine engine.

[0101] To determine whether the reverse exhaust system is operating properly / has operated properly, the engine controller is configured to determine the engine temperature at a first time shortly after starting operation of the reverse exhaust system, and is further configured to determine the engine temperature at a second time shortly before shutting down the engine controller. The first time shortly after starting operation of the reverse exhaust system is shown at T3, and the second time shortly before shutting down the engine controller is shown at T4. The terms "shortly after" and "shortly before" are just terms used for convenience and do not require any inherent limitations. In some exemplary aspects, these time periods can be between, for example, two seconds and 30 seconds.

[0102] From Figure 5 the engine temperature line 310 in the graph 300 of, it can be understood that if the reverse exhaust system is operating properly, the slope between the engine temperatures at the first time T3 and the second time T4 is a negative slope, indicating a decrease in engine temperature. Depicted in dashed lines is an optional engine temperature line 310' starting at T2, showing the engine temperature starting from T2 if the reverse exhaust system is not operating correctly. As shown, if the reverse exhaust system is not operating properly, the slope between the engine temperatures at the first time T3 and the second time T4 is a positive slope, indicating an increase in engine temperature.

[0103] Thus, once it is time to start a gas turbine engine, as shown at T7, if the reverse exhaust system is operating properly, the engine temperature will be relatively low. In contrast, if the reverse exhaust system is not operating properly, the engine temperature will be relatively high. If the engine temperature is relatively high, this may indicate, for example, that coking has occurred within the fuel nozzles, and further may indicate that the engine is experiencing a relatively high degree of rotor bow. If the engine is experiencing a relatively high degree of rotor bow, it will take a relatively long time to drive the gas turbine engine to allow the heat to redistribute and relieve the relatively high degree of rotor bow. In contrast, if the engine temperature is relatively low and the engine is experiencing a relatively small amount of rotor bow, then it may not be necessary to drive the engine for a long time before accelerating the engine to start.

[0104] For example, if the reverse exhaust system is operating properly after a previous shutdown, such as in the embodiment depicted in Figure 5 graph 300, then the period of time used to drive the gas turbine engine, as shown between T7 and T8, may be relatively low before accelerating the engine to start at T8. This may result in a relatively short amount of time between starting the start sequence at T7 and achieving the ignition rotational speed at T9. Conversely, if the reverse exhaust system is not operating properly after a previous shutdown, such as Figure 5 depicted by the dashed line in graph 300, then the period of time used to drive the gas turbine engine, as shown between T7 and T10 (via the dashed engine rotational speed line 308'), before accelerating the engine to start at T10, is relatively high. This may result in a relatively long amount of time between starting the start sequence at T7 and achieving the ignition rotational speed at T11.

[0105] In this manner, the engine controller, the aircraft controller, or both can determine data representative of the operation of the rotor bow system after a previous shutdown of the gas turbine engine and, in response, modify the start sequence for a subsequent start of the gas turbine engine. For example, in the case where the data representative of the operation of the rotor bow system indicates that the rotor bow system is operating properly, modifying the start sequence for a subsequent start of the gas turbine engine can include reducing the drive time of the gas turbine engine, saving time and energy for the subsequent start sequence.

[0106] Furthermore, it should be understood that in addition to the exemplary steps outlined above, an engine controller for an engine incorporating an air cooling system / reverse exhaust system, in accordance with one or more exemplary aspects of the present disclosure, can be further configured to perform additional functions. For example, now referring to Figure 6, a schematic diagram of a control system 400 in accordance with the present disclosure is provided. The control scheme 400 generally includes a controller 402, which may be an engine controller. The controller 402 may operate with an air cooling system / reverse exhaust system to control the operation of the system and receive data from the system and the engine including the system.

[0107] The control scheme 400 further includes a configuration block 404, whereby the controller 402 can confirm that the air cooling system / reverse exhaust system is installed. The configuration block 404 can check whether a specific wiring harness is connected and whether the correct software is installed.

[0108] The control scheme 400 further includes: an output data processing block at block 406, whereby the controller 402 can communicate data with, for example, an aircraft controller; and a communication protocol block at block 408, which provides a communication protocol between the engine controller and, for example, an aircraft controller.

[0109] Further, the control scheme 400 includes a menu mode block at block 410, allowing manual operation of the air cooling system / reverse exhaust system in response to, for example, one or more user inputs. The menu mode block can allow maintenance operations for the air cooling system / reverse exhaust system, an operability check of the air cooling system / reverse exhaust system, etc.

[0110] Further, the control scheme 400 includes an air cooling system / reverse exhaust system fault monitoring and handling block at block 412. Block 412 can allow storage and processing of additional information that can indicate that the air cooling system / reverse exhaust system is inoperative. Block 412 can include some persistence such that multiple faults must be shown before a repair or replacement of the air cooling system / reverse exhaust system is requested.

[0111] This written description uses examples to disclose aspects of the present invention, including the best mode, and also enables those skilled in the art to practice aspects of the present invention, including making and using any device or system and performing any combined method. The patentable scope of the present invention is defined by the claims, and may include other examples that occur to those skilled in the art. If these other examples include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, then these other examples are intended to be within the scope of the claims.

[0112] The subject matter of the following items provides further aspects:

[0113] A method for operating a gas turbine engine, comprising: determining data representative of operation of a cooling system of the gas turbine engine during shutdown of the gas turbine engine, after shutdown of the gas turbine engine, or both; and modifying a start schedule of the gas turbine engine in response to the determined data representative of operation of the cooling system of the gas turbine engine.

[0114] The method of one or more of these clauses, wherein the cooling system provides a cooling air flow to components of the gas turbine engine configured to contain fuel.

[0115] The method of one or more of these clauses, wherein the cooling system is a reverse exhaust system configured to provide an air flow over components of a burner of the gas turbine engine during operation of the reverse exhaust system.

[0116] The method of one or more of these clauses, wherein the cooling system includes a blower positioned within a lower cowl location of the gas turbine engine.

[0117] The method of one or more of these clauses, wherein the blower is configured to provide an air flow from a lower cowl location of the gas turbine engine or from a bypass valve.

[0118] The method of one or more of these clauses, wherein the cooling system defines an inlet exposed to a lower cowl location of the gas turbine engine.

[0119] The method of one or more of these clauses, wherein the cooling system is configured to provide an air flow through a compressor exhaust port using a blower located within a cowl of the gas turbine engine.

[0120] The method of one or more of these clauses, wherein modifying the start schedule of the gas turbine engine includes reducing a drive time of the gas turbine engine.

[0121] The method of one or more of these clauses, wherein the determined data representative of operation of the cooling system includes data representative of normal operation of the cooling system.

[0122] The method of one or more of these clauses, further comprising: starting operation of the cooling system after shutdown of the gas turbine engine, and wherein the determined data representative of operation of the cooling system includes data representative of an engine temperature at a first time after the operation of the cooling system has started and data representative of an engine temperature at a second time, wherein the second time is after the first time.

[0123] A method of one or more of these items, wherein the determined data representing the operation of the cooling system further includes data representing the difference between the engine temperature at a first time and the engine temperature at a second time.

[0124] A method of one or more of these items, further comprising: determining data representing a bleed temperature indicator parameter; and in response to the data representing the bleed temperature indicator parameter, starting the operation of the cooling system after the gas turbine engine is shut down.

[0125] A method of one or more of these items, further comprising: determining data representing engine operating parameters; and in response to the data representing the engine operating parameters, starting the operation of the cooling system after the gas turbine engine is shut down.

[0126] A method of one or more of these items, further comprising: starting the operation of the cooling system after the gas turbine engine is shut down; and operating the cooling system for a predetermined amount of time.

[0127] A method of one or more of these items, wherein operating the cooling system for a predetermined amount of time includes powering the cooling system using a power source external to the gas turbine engine.

[0128] A method of one or more of these items, further comprising: starting the operation of the cooling system after the gas turbine engine is shut down; after the gas turbine engine is shut down, after a first amount of time, shutting down the engine controller of the gas turbine engine; and after the gas turbine engine is shut down, operating the cooling system for a second amount of time, wherein the second amount of time is greater than the first amount of time.

[0129] A method of one or more of these items, further comprising: after the gas turbine engine is shut down, starting the operation of the cooling system; and operating the cooling system, wherein operating the cooling system includes providing a cooling air flow through the high-pressure compressor of the gas turbine engine, the combustion section of the gas turbine engine, or both.

[0130] A method for operating a gas turbine engine, comprising: receiving data representing a bleed temperature indicator parameter; in response to the received data representing the bleed temperature indicator parameter, starting the operation of the cooling system of the gas turbine engine during, after, or both during and after the gas turbine engine is shut down; and operating the cooling system to provide a cooling air flow through the high-pressure compressor of the gas turbine engine, the combustion section of the gas turbine engine, or both.

[0131] A method of one or more of these items, wherein the data representing the bleed temperature indicator parameter includes data representing ambient conditions, data representing engine temperature parameters, or both.

[0132] A method of one or more of these items, wherein operating the cooling system comprises operating the cooling system for a certain amount of time based at least in part on a bleed temperature indicator parameter.

[0133] An aviation system comprising: a gas turbine engine including a compressor section, a combustion section, and a turbine section arranged in a series flow order, the gas turbine engine further including a cooling system in selective fluid communication with the compressor section, the combustion section, or both; and a control system operably communicating with the cooling system, the control system configured to: determine data representing the operation of the cooling system of the gas turbine engine during shutdown of the gas turbine engine, after shutdown of the gas turbine engine, or both; and modify a start schedule of the gas turbine engine in response to the determined data representing the operation of the cooling system of the gas turbine engine.

[0134] An aviation system of one or more of these items, wherein the cooling system provides a cooling air flow to components of the gas turbine engine configured to contain fuel.

[0135] An aviation system of one or more of these items, wherein the cooling system is a reverse exhaust system configured to provide an air flow over components of a burner of the gas turbine engine during operation of the reverse exhaust system.

[0136] An aviation system of one or more of these items, wherein modifying the start schedule of the gas turbine engine includes reducing a drive time of the gas turbine engine.

[0137] An aviation system of one or more of these items, wherein the determined data representing the operation of the cooling system includes data representing normal operation of the cooling system.

[0138] An aviation system of one or more of these items, wherein the controller is further configured to start operation of the cooling system after shutdown of the gas turbine engine, and wherein the determined data representing the operation of the cooling system includes data representing an engine temperature at a first time after start of operation of the cooling system and data representing an engine temperature at a second time after start of operation of the cooling system, wherein the second time is after the first time.

[0139] A controller for a gas turbine engine, the controller including one or more processors and a memory storing instructions that, when executed by the one or more processors, cause the gas turbine engine to: determine data representing the operation of the cooling system during shutdown of the gas turbine engine, after shutdown of the gas turbine engine, or both; and modify a start schedule of the gas turbine engine in response to the determined data representing the operation of the cooling system of the gas turbine engine.

Claims

1. A method for operating a gas turbine engine, characterized in that, comprising: determining data representing the operation of a cooling system of the gas turbine engine during, after, or both during and after shutdown of the gas turbine engine; and modifying a start schedule of the gas turbine engine in response to the determined data representing the operation of the cooling system of the gas turbine engine; wherein modifying the start schedule of the gas turbine engine includes reducing or increasing a drive time of the gas turbine engine, wherein the gas turbine engine further includes an exhaust component, wherein the cooling system is a reverse exhaust system configured to provide an air flow through the exhaust component and over components of a combustor of the gas turbine engine during operation of the reverse exhaust system.

2. The method according to claim 1, characterized in that, the cooling system provides a cooling air flow to components of the gas turbine engine configured to contain fuel.

3. The method according to claim 1, characterized in that, the cooling system includes a blower positioned within a lower cowl location of the gas turbine engine.

4. The method according to claim 1, characterized in that, modifying the start schedule of the gas turbine engine includes reducing the drive time of the gas turbine engine.

5. The method according to claim 1, characterized in that, the determined data representing the operation of the cooling system includes data representing normal operation of the cooling system.

6. The method according to claim 1, characterized in that, further comprising: starting operation of the cooling system after shutdown of the gas turbine engine, and wherein the determined data representing the operation of the cooling system includes data representing an engine temperature at a first time after the operation of the cooling system has started and data representing the engine temperature at a second time, wherein the second time is after the first time.

7. The method according to claim 6, characterized in that, the determined data representing the operation of the cooling system further includes data representing a difference between the engine temperature at the first time and the engine temperature at the second time.

8. The method according to claim 1, characterized in that, further comprising: determining data representing a bleed temperature indicator parameter; and starting operation of the cooling system after shutdown of the gas turbine engine in response to the data representing the bleed temperature indicator parameter.

9. The method according to claim 1, characterized in that, further comprising: determining data representing engine operating parameters; and starting operation of the cooling system after shutdown of the gas turbine engine in response to the data representing the engine operating parameters.

10. The method according to claim 1, characterized in that, further comprising: starting operation of the cooling system after shutdown of the gas turbine engine; and operating the cooling system for a predetermined amount of time.

11. The method according to claim 1, wherein, further comprising: after the gas turbine engine is shut down, starting the operation of the cooling system; after the gas turbine engine is shut down, after a first time period, shutting down the engine controller of the gas turbine engine; and after the gas turbine engine is shut down, operating the cooling system for a second time period, wherein the second time period is greater than the first time period.

12. The method according to claim 1, wherein, further comprising: after the gas turbine engine is shut down, starting the operation of the cooling system; and operating the cooling system, wherein operating the cooling system includes providing a cooling air flow through the high-pressure compressor of the gas turbine engine, the combustion section of the gas turbine engine, or both.

13. A method for operating a gas turbine engine, wherein, comprising: receiving data representing a bleed temperature indicator parameter; in response to the received data representing the bleed temperature indicator parameter, starting the operation of the cooling system of the gas turbine engine during the shutdown of the gas turbine engine, after the shutdown of the gas turbine engine, or both; and operating the cooling system to provide a cooling air flow for the exhaust components of the gas turbine engine and through the high-pressure compressor of the gas turbine engine, the combustion section of the gas turbine engine, or both; and modifying the start schedule of the gas turbine engine includes reducing or increasing the drive time of the gas turbine engine.

14. The method according to claim 13, wherein, the data representing the bleed temperature indicator parameter includes data representing ambient conditions, data representing engine temperature parameters, or both.

15. The method according to claim 13, wherein, operating the cooling system includes operating the cooling system for a certain time period at least partially based on the bleed temperature indicator parameter.

16. An aviation system, wherein, comprising: a gas turbine engine, the gas turbine engine including a compressor section, a combustion section, and a turbine section arranged in a series flow order, the gas turbine engine further including a cooling system selectively in fluid communication with the compressor section, the combustion section, or both; and a control system operably communicating with the cooling system, the control system configured to: determine data representing the operation of the cooling system of the gas turbine engine during the shutdown of the gas turbine engine, after the shutdown of the gas turbine engine, or both; and in response to the determined data representing the operation of the cooling system of the gas turbine engine, modifying the start schedule of the gas turbine engine; wherein modifying the start schedule of the gas turbine engine includes reducing or increasing the drive time of the gas turbine engine, Wherein the cooling system is a reverse exhaust system configured to provide an air flow through an exhaust component and over components of a combustor of the gas turbine engine during operation of the reverse exhaust system.

17. The aviation system according to claim 16, wherein, the cooling system provides a cooling air flow to components of the gas turbine engine configured to contain fuel.

18. The aviation system according to claim 16, wherein, modifying the start schedule of the gas turbine engine includes reducing a drive time of the gas turbine engine.

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