Method and system for fuel nozzle cleaning during engine operation

Abstract

A method (1000) and system for cleaning a fuel nozzle (60) during operation of an engine (15) is provided. The step (1020) or operation includes operating a compressor section (42) to provide an oxidant (22) flow to a combustion chamber (72), operating a fuel system (90) under a first fuel flow condition (410), wherein the first fuel flow condition (410) provides a fuel-oxidant ratio (403) at the combustion chamber (72), operating the fuel system (90) under a second fuel flow condition (420), wherein the second fuel flow condition (420) provides an equal fuel-oxidant ratio (403) at the combustion chamber (72) under the first fuel flow condition (410) and the second fuel flow condition (420), and after operating the fuel system (90) under the second fuel flow condition (420), operating the fuel system (90) under a third fuel flow condition (430).

Description

Technical Field

[0001] The present subject matter generally relates to methods and systems for fuel nozzle cleaning during operation of a heat engine. Specific aspects of the present subject matter relate to methods and systems for fuel nozzle cleaning during operation of a gas turbine engine. Still other specific aspects of the present subject matter relate to fuel nozzle cleaning during in-flight operation of a propulsion system. Background Art

[0002] Heat engines, such as gas turbine engines, can experience fuel coking within the fuel nozzles when the fuel within the fuel nozzles is exposed to high temperatures during engine operation. Fuel coking can occur particularly under low fuel flow conditions and when exposed to high temperatures during operation. Fuel coking within the fuel nozzles can also occur after an engine shutdown, for example, due to heat soaking of the fuel nozzles and residual fuel within the fuel nozzles after shutdown.

[0003] Fuel coke accumulation may adversely affect fuel nozzle performance, as well as overall engine performance, durability, or operability, for example, by undesirably restricting or blocking fuel flow through a fuel nozzle. Such restricted fuel flow may typically result in an uneven spray pattern, which may accelerate degradation of components of the combustion section and / or turbine section. Component degradation may be due to increased circumferential or radial thermal gradients, or hot spots, or damage caused by increased combustion dynamics, such as pressure oscillations, acoustic or other uneven wear and damage. Such restricted fuel flow may also result in pressure buildup at the fuel system, such as reaching the fuel system pressure limit, which may result in loss of engine thrust control.

[0004] Therefore, there is a need for improved cleaning systems and methods that address these problems. Summary of the invention

[0005] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0006] Aspects of the present disclosure are directed to a heat engine, including a compressor section configured to provide an oxidant flow to a combustion chamber. The heat engine includes a fuel nozzle, including a first injector and a second injector, wherein the fuel nozzle is configured to provide a first fuel flow to the combustion chamber through the first injector and provide a second fuel flow to the combustion chamber through the second injector. The heat engine includes a fuel system having a first conduit in fluid communication with the first injector and a second conduit in fluid communication with the second injector, wherein the fuel system is configured to variably provide the first fuel flow and be separated from the second fuel flow. The heat engine includes a controller configured to perform an operation, the operation including operating the compressor section to provide an oxidant flow to the combustion chamber under a first oxidant flow condition; operating the fuel system under a first fuel flow condition, wherein the first fuel flow condition includes a first fuel flow rate A of the first fuel flow through the first injector and a first fuel flow rate B of the second fuel flow through the second injector, and wherein the first fuel flow condition provides a fuel-oxidant ratio at the combustion chamber including the first fuel flow and the second fuel flow. Operating the fuel system under a second fuel flow condition, wherein the second fuel flow condition includes a second fuel flow rate A of the first fuel flow through the first injector and a second fuel flow rate B of the second fuel flow through the second injector, wherein the second fuel flow condition provides an equal fuel-oxidizer ratio at the combustion chamber between the first fuel flow condition and the second fuel flow condition; and after operating the fuel system under the second fuel flow condition, operating the fuel system under a third fuel flow condition, wherein the third fuel flow condition includes a third fuel flow rate A of the first fuel flow through the first injector and a third fuel flow rate B of the second fuel flow through the second injector.

[0007] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the specification with reference to the accompanying drawings, a full and enabling disclosure of the present invention, including the best mode thereof, is made to one of ordinary skill in the art, wherein:

[0009] Figure 1 is a perspective view of an embodiment of an aircraft according to an aspect of the present disclosure;

[0010] Figure 2 is a schematic cross-sectional view of an embodiment of a heat engine according to aspects of the present disclosure, the heat engine comprising a controller configured to perform the steps of the method;

[0011] Figure 3is a schematic diagram of an exemplary combustion and fuel system according to an aspect of the present disclosure;

[0012] Figure 4 is an exemplary chart describing a portion of a method of fuel nozzle cleaning during engine operation according to aspects of the present disclosure; and

[0013] 5 is a flow chart outlining the steps of a method of fuel nozzle cleaning during engine operation according to aspects of the present disclosure;

[0014] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the invention. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the invention. For example, features shown or described as part of one embodiment may be used together with another embodiment to produce a further embodiment. Therefore, it is an object of the present invention to encompass such modifications and variations within the scope of the appended claims and their equivalents.

[0016] As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of each component.

[0017] The terms "upstream" and "downstream" refer to the relative directions of fluid flow in a fluid path. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction to which the fluid is flowing.

[0018] The present invention provides an embodiment of a method and system for cleaning a fuel nozzle during engine operation. The embodiment of the method and system provides thermal decomposition of deposits (e.g., fuel coke) in a fuel nozzle during engine operation. The thermally decomposed deposits can be decomposed into lighter and / or smaller particles, thereby allowing them to be discharged from the fuel nozzle. In certain embodiments, the method and system provided herein allow the fuel nozzle to be cleaned during flight operation of an engine as an aircraft propulsion system. The embodiment of the method and system described and described herein includes the steps of operating a fuel system to thermally decompose deposits at a fuel nozzle and determining the conditions for performing a cleaning step. For example, by reducing or eliminating uneven fuel nozzle injection patterns, reducing circumferential and / or radial thermal gradient variations (e.g., reducing hot spots), or reducing other conditions that may cause uneven or increased wear or deterioration of certain combustion sections or turbine section components, the embodiments of the method and system provided herein can improve the life, durability, maintenance, and / or performance of other combustion sections and / or turbine section components.

[0019] Referring now to the accompanying drawings, Figure 1 In the present invention, an exemplary embodiment of an aircraft 100 including a propulsion system 10, a fuel nozzle 60, a fuel system 90 and a controller 210 according to an aspect of the present disclosure is provided. The aircraft 100 includes an aircraft structure or airframe 105. The airframe 105 includes a fuselage 110, to which wings 120 and a tail 130 are attached. The propulsion system 10 according to various aspects of the present disclosure is attached to one or more parts of the airframe. In various embodiments, according to various aspects of the disclosure provided herein, the propulsion system 10 can generally be configured as any suitable propulsion system or power generation system, which includes a fuel nozzle and a fuel system, and the fuel nozzle and the fuel system are configured to provide fuel to a combustion chamber or a detonation chamber. In some cases, the propulsion system 10 is configured as a turbofan, a turbopropeller, a turbojet or a turboshaft engine, or a ramjet or a scramjet engine, or a hybrid engine, or a combination thereof. In some cases, the propulsion system 10 is attached to the rear portion of the fuselage 110. In some other cases, propulsion system 10 is attached below, above, or through wing 120 and / or a portion of tail 130 .

[0020] As further described in detail herein, the aircraft 100 including the propulsion system 10 is configured to perform operations or maneuvers in ground operations, takeoff, and flight. Aircraft and engine operations or maneuvers may include operations or maneuvers associated with a landing-takeoff (LTO) cycle. The LTO cycle includes idling, takeoff, climb, and approach. The LTO cycle may generally include certain thrust output settings from the engine 15. However, in various embodiments, the operations or maneuvers of the aircraft 100 and the propulsion system 10 may include other or additional steps, providing changes in engine thrust output or power generation, altitude or attitude, or a combination thereof, resulting in changes in environmental and inlet parameters at the propulsion system 10 or the aircraft 100. Portions of the LTO cycle may also be associated with certain emissions or noise restrictions, such as, but not limited to, restrictions on emissions of nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), unburned hydrocarbons (UHC), or smoke or perceived acoustic noise from the propulsion system 10.

[0021] Reference now Figure 2 , an embodiment of a heat engine 15 is provided. Figure 1 The propulsion system 10 may include Figure 2 The engine 15 provided in the embodiment of the present invention is a turbomachine 15. In various embodiments, the engine 15 can be configured as a propulsion system, a power generation system, a hybrid electric engine or other thermal engine equipment, which includes a fuel system 90, and according to aspects of the present disclosure, the fuel system 90 is configured to provide liquid and / or gaseous fuel to the fuel nozzle 60. The engine 15 can generally be configured as a turbomachine, such as a gas turbine engine including a compressor section 42, a combustion section 44 and a turbine section 46 arranged in a serial flow. The engine 15 of certain embodiments is configured as a turbofan or turbojet engine, which includes a fan assembly 14 operably connected to the core engine 40. There are also various embodiments that can define the engine 15 as an open rotor, a propfan engine or a Brayton cycle machine. Further, certain embodiments may include a power gear assembly operably connected to the fan assembly 14 and at least a portion of the turbine section 46. The core engine 40 and the fan assembly 14 are positioned in a serial flow arrangement.

[0022] The engine 15 includes an inlet 18 through which an oxidant flow, schematically depicted by arrows 22, enters the engine 15. In particular, the oxidant flow 22 enters the core engine 40. The oxidant flow 22 is compressed by the compressor section 42 before entering the downstream combustion section 44. The combustion section 44 includes a compressor according to the present disclosure. Figure 3The fuel nozzle 60 of the described embodiment. The fuel system 90 provides a first fuel flow and a second fuel flow to the fuel nozzle 60. During certain operations of the engine 15 according to the disclosed aspects provided herein, the first fuel flow and / or the second fuel flow mix with the oxidant flow 22 and burn or explode to produce combustion gases. The combustion gases release energy to drive the turbine section 46, which drives the compressor section 42.

[0023] Reference now Figure 3 , an exemplary embodiment of a combustion section 44 including a fuel nozzle 60 and a fuel system 90 according to an aspect of the present disclosure is provided. The combustion section 44 can be configured as any suitable type of burner, such as, but not limited to, a flame arrester, an initiation burner (e.g., pulse initiation, rotation initiation, etc.), a vortex burner, a can burner, a can ring burner, an annular burner, a vortex burner, or a combination thereof. The combustion section 44 includes an initiation chamber or combustion chamber 72, in which a liquid and / or gas fuel is combusted with an oxidant 22, as described herein. The fuel nozzle 60 is configured as any suitable type of fuel nozzle, which includes a first injector 61 and a second injector 62. The first injector 61 is configured to receive a first fuel flow from the fuel system 90, schematically depicted by arrow 91. The second injector 62 is configured to receive a second fuel flow from the fuel system 90, schematically depicted by arrow 92. The first injector 61 is configured to provide the first fuel flow 91 to the combustion chamber 72. The fuel nozzle 60 includes a plurality of fuel injection ports through which respective fuel flows are provided from the fuel nozzle 60 to the combustion chamber 72. The plurality of fuel injection ports include a first opening 67 corresponding to the first injector 61 and a second opening 68 corresponding to the second injector 62.

[0024] In certain embodiments, the combustion section 44 includes, for example, a plurality of fuel nozzles 60 in a circumferential arrangement or other suitable arrangement. In certain embodiments, the fuel nozzle 60 is configured as a rich-burn, lean-burn or other suitable type of fuel nozzle. In a specific embodiment, the fuel nozzle 60 includes one or more first injectors 61 and one or more second injectors 62. In certain embodiments, the first injector 61 is configured as a main fuel injector, and the second injector 62 is configured as a pilot fuel injector. During nominal operation of the engine 15, the fuel system 90 and the fuel nozzle 60, the main fuel injector can be configured to provide a larger fuel flow to the combustion chamber 72 than the pilot fuel injector. For example, under certain operating conditions of the engine (e.g., starting or low power), approximately 100% of the fuel to the combustion chamber 72 can be discharged by the pilot fuel injector. In other cases, under certain operating conditions of the engine (e.g., greater than low power, such as medium power or high power conditions), most of the fuel can be discharged by the main fuel injector. However, under certain conditions, such as those provided herein, the fuel flow through the respective injectors 61, 62 will desirably be altered or adjusted away from nominal conditions. It should be appreciated that in various embodiments, the first injector 61 may be configured as a pilot fuel injector and the second injector 62 may be configured as a main fuel injector.

[0025] The fuel system 90 is configured to variably provide a first fuel flow 91 to the first injector 61 and to be separated from a second fuel flow 92 and the second injector 62. In certain embodiments, the fuel system 90 includes a first conduit 95 in fluid communication with the first injector 61 of the fuel nozzle 60 and a second conduit 96 in fluid communication with the second injector 62 of the fuel nozzle 60. The fuel system 90 is configured to desirably allow and restrict the first fuel flow 91 and the second fuel flow 92 to be discharged to the fuel nozzle 60 separately from each other, as described herein. In one embodiment, the fuel system 90 includes a first valve 93 positioned at the first conduit 95 and a second valve 94 positioned at the second conduit 96, thereby allowing, for example, based on one or more steps of the method provided herein, the respective first fuel flow 91 and the second fuel flow 92 to be selectively discharged and restricted to the fuel nozzle 60.

[0026] In various embodiments, the combustion section 44 includes a plurality of combustor components that generally define a combustion chamber 72 or other portion exposed to the hottest portion of the combustion section 44. Such combustor components may include a liner assembly 70, a heat shield assembly 74, a swirler 76, or a fuel nozzle 60. As further described herein, embodiments of the method may include health parameters corresponding to temperatures or thermal gradients at one or more combustor components. In certain embodiments, health parameters corresponding to combustor components or turbine sections are associated with limiting undesirable temperature differences or gradients along individual components or relative to multiple components (e.g., multiple components circumferentially or radially, such as an annular combustor). The health parameters may correspond to desired limitations associated with mitigating the formation of hot spots at the combustion section 44 or turbine section 46.

[0027] In various other embodiments, the health parameter may correspond to a life, durability, or other structural integrity parameter associated with a combustor component, such as an expected structural life or coating retention period, based on combustor stability. In still other embodiments, the health parameter may correspond to an emission or noise parameter at the combustion section 44, such as, but not limited to, an expected or required emission output range or a perceived noise range during operation of the engine 15. In some embodiments, the expected or required emission or perceived noise output range is a function of engine or aircraft operation. For example, the expected or required emission or perceived noise output range may correspond to an emission limit corresponding to an LTO cycle, a local emission requirement, or other regulatory requirement.

[0028] Reference now Figure 4 , an exemplary graph 400 is provided describing a portion of a method for fuel nozzle cleaning during engine operation (hereinafter referred to as "method 1000"). Referring also to FIG. 5, a flowchart outlining the steps of method 1000 is generally provided. Graph 400 depicts a graph of a fuel parameter over time. In various cases, the fuel parameter corresponds to a fuel flow to a combustion chamber. In certain embodiments, the fuel parameter is a fuel flow (e.g., W fuel ), or the fuel pressure corresponding to the fuel flow through the fuel system and the fuel nozzle to the combustion chamber (e.g., P fuel ). It should be appreciated that in various embodiments, any suitable parameter indicative of fuel flow to the combustion chamber may be utilized.

[0029] Graph 400 depicts a plurality of fuel flows corresponding to a plurality of fuel injection ports at a fuel nozzle (e.g., a first fuel flow corresponding to a fuel flow rate A, a second fuel flow corresponding to a fuel flow rate B, etc.). The method 1000 may be performed with an engine, a controller, a fuel system, and a fuel nozzle to allow independent or separate variability in controlling fuel flows through two or more conduits and fuel injection ports at a fuel nozzle.

[0030] Generally speaking, a fuel nozzle includes a first injector and a second injector, as shown in FIG. Figure 3 The fuel nozzle is configured to provide a first fuel flow to the combustion chamber through a first injector and a second fuel flow to the combustion chamber through a second injector. The fuel system includes a first conduit in fluid communication with the first injector at the fuel nozzle, and a second conduit in fluid communication with the second injector at the fuel nozzle. The fuel system is configured to provide a first fuel flow to the combustion chamber through a fuel injection port of the fuel nozzle, and the first fuel flow is independent or separately variable from a second fuel flow to the combustion chamber through a second fuel injection port of the fuel nozzle. In certain embodiments, the fuel conduit, the fuel injection port, or both correspond to one or more main fuel injectors separated from one or more pilot fuel injectors at the fuel nozzle, as described elsewhere herein.

[0031] Referring back to chart 400, according to an embodiment of the method provided herein, method 1000 includes multiple fuel flow conditions. As further described herein, some or all of the steps of method 1000 provided herein may be stored and executed by a controller (e.g., controller 210) or other computing system. Although certain steps provided herein may be performed in one or more specific orders, it should be understood that various embodiments of the method may rearrange, reorder, omit, include, or iterate certain steps or combinations of steps within the scope of the present disclosure.

[0032] Referring now to the flow chart of FIG. 5 , in conjunction with chart 400 , the method 1000 includes operating a compressor section at 1010 to generate or provide an oxidant flow to a combustion chamber at a first oxidant flow condition. The first oxidant flow condition may generally include environmental parameters corresponding to a range within which the oxidant flow allows for purging of the fuel nozzle while operating the engine at a desired fuel-oxidant ratio. In certain embodiments, the desired fuel-oxidant ratio includes maintaining the desired fuel-oxidant ratio across more than two fuel flow conditions, as described herein.

[0033] In certain other embodiments, at 1010, the environmental parameters of the first oxidant flow conditions may generally correspond to a temperature range and a pressure range of the oxidant flow at the combustion section and from the compressor section. In one embodiment, the environmental parameters correspond to the first oxidant flow downstream of the compressor section and upstream of the combustion chamber. For example, the environmental parameters may correspond to the oxidant temperature (e.g., T3) and the oxidant pressure (e.g., P3) at station 3 at the heat engine.

[0034] In various embodiments, the environmental parameters correspond to conditions under which the oxidant flow allows thermal decomposition of fuel deposits in the fuel nozzle. The first oxidant flow condition may correspond in particular to temperature and pressure conditions at the fuel nozzle, which allow thermal decomposition of deposits of fuel or other substances (e.g., carbon accumulation in the first and second injectors, fuel coke, etc.). The environmental parameters may further correspond to pressure conditions under which the fuel nozzle and / or the fuel system may allow thermally decomposed deposits to be purged from the fuel nozzle into the combustion chamber. In certain other embodiments, the environmental parameters correspond to conditions under which combustion is sustained or sustainable to provide an oxidant flow to the combustion chamber above a first temperature threshold and a first pressure threshold. The environmental parameters may also correspond to conditions that maintain the desired combustion stability or performance, or mitigate certain combustion acoustics, pressure oscillations or fluctuations, lean flameouts, emissions, or other adverse conditions. In various embodiments, the environmental parameters may correspond to one or emission or noise limits corresponding to certain portions of the LTO cycle.

[0035] It should be understood that the environmental parameters include one or more specific ranges of temperature and / or pressure of the oxidant flow downstream of the compressor section (e.g., at the fuel nozzle, or at the combustion chamber). The specific ranges of environmental parameters provided here may be critical with respect to one or more steps of the method 1000 provided here, such as allowing the fuel nozzle to be cleaned during engine operation according to one or more embodiments provided here. The various ranges provided here may particularly allow for purging or otherwise removing fuel char or debris from the fuel nozzle during engine operation. In certain embodiments, the environmental parameters include a temperature range between about 550 degrees Fahrenheit and about 1250 degrees Fahrenheit (between about 287 degrees Celsius and about 680 degrees Celsius). In another embodiment, the environmental parameters correspond to a temperature range between about 600F and about 1100F (between about 315°C and about 595°C). In certain other embodiments, the environmental parameters include a pressure range between about 135 pounds per square inch (psia) and about 315psia (between about 930 kilopascals (kPa) and about 2172kPa). In another embodiment, the environmental parameter corresponds to a pressure range between about 150 psia and about 300 psia (between about 1034 kPa and about 2069 kPa). In yet another embodiment, the environmental parameter corresponds to a pressure range between about 175 psia and about 275 psia (between about 1205 kPa and about 1900 kPa).

[0036] At 1020, method 1000 includes operating the fuel system at a first fuel flow condition, such as depicted at 410 on graph 400. First fuel flow condition 410 includes a first fuel flow rate A depicted at line 401, corresponding to a flow rate of 100% by Figure 3The first fuel flow 91 of the first injector 61 of the fuel nozzle 60 is depicted in FIG. The first fuel flow condition 410 also includes a first fuel flow rate B depicted at line 402, corresponding to the first fuel flow rate B through Figure 3 4. The second fuel flow 92 of the second injector 62 of the fuel nozzle 60 is depicted in FIG. The first fuel flow condition 410 provides a fuel-oxidant ratio depicted at line 403 at the combustion chamber including the first fuel flow and the second fuel flow.

[0037] It should be appreciated that fuel flow rate A and fuel flow rate B may generally correspond to one or more of the fuel flow rates of the respective fuel flows. However, in other embodiments, fuel flow rate A and fuel flow rate B may each correspond to any suitable parameter indicating the volumetric and / or mass rate or other quantity of fuel passing through the fuel nozzle from the fuel system.

[0038] It should be further appreciated that the fuel-oxidant ratio 403 generally corresponds to the total fuel flow provided to the combustion chamber through the plurality of fuel nozzles (e.g., Figure 4 The sum of the fuel flow rate A 401 and the fuel flow rate B 402 in, or Figure 3 The total fuel-oxidant ratio of the first fuel stream 91 and the second fuel stream 92 in the combustion chamber (the sum of the first fuel stream 91 and the second fuel stream 92 in the combustion chamber) to the oxidant stream provided to the combustion chamber for mixing with the total fuel stream and burning. The fuel-oxidant ratio can be calculated based on one or more known methods, or otherwise corresponds to a fuel-oxidant ratio or a fuel-air ratio. In some cases, the fuel-oxidant ratio can correspond to a fuel-air equivalence ratio, an air-fuel equivalence ratio, or other suitable parameters, which corresponds to the total number, mass, or volume, or flow rate of liquid and / or gaseous fuels mixed with the total number, mass, or volume, or flow rate of the oxidant and burned or detonated in the combustion chamber.

[0039] At 1030, the method 1000 includes operating the fuel system at a second fuel flow condition, such as depicted at 420 on the graph 400. The second fuel flow condition 420 includes a second fuel flow rate A corresponding to the first fuel flow through the first injector of the fuel nozzle. The second fuel flow condition 420 also includes a second fuel flow rate B corresponding to the second fuel flow through the second injector of the fuel nozzle. The second fuel flow condition 420 provides an equal fuel-oxidizer ratio at the combustion chamber under the first fuel flow condition 410 and the second fuel flow condition 420. In other words, the total amount or mass of fuel provided to the combustion chamber under the first fuel flow condition 410 is equal to the total amount or mass of fuel provided to the combustion chamber under the second fuel flow condition 420. However, as can be understood by the description in the graph 400, the first fuel flow rate A under the first fuel flow condition 410 is different from the second fuel flow rate A under the second fuel flow condition 420, and the first fuel flow rate B under the first fuel flow condition 410 is different from the second fuel flow rate B under the second fuel flow condition 420.

[0040] In certain embodiments, the second fuel flow condition 420 includes a second fuel flow rate A that is greater than the first fuel flow rate A at the first fuel flow condition 410. In still other embodiments, the second fuel flow condition 420 includes a second fuel flow rate B that is less than the first fuel flow rate B at the first fuel flow condition 410. In one embodiment, the method 1000 includes, at 1025, transitioning from the first fuel flow condition 410 to the second fuel flow condition 420, as depicted at 419 in the graph 400. In various embodiments, the method 1000 occurs at 1025 while maintaining a fuel-oxidant ratio at the combustion chamber approximately equal or unchanged during the transition from the first fuel flow condition 410 to the second fuel flow condition 420.

[0041] In a particular embodiment, at the second fuel flow condition 420, the second fuel flow rate B is zero. In one embodiment, the second fuel flow is shut off or diverted from the second injector flowing through the fuel nozzle. In yet other special embodiments, the second fuel flow is typically shut off or diverted from flowing through the fuel nozzle. In various embodiments, method 1000 includes shutting off or diverting the second fuel flow from the fuel nozzle and allowing a non-fuel fluid medium to occupy the second injector of the fuel nozzle. The non-fuel fluid medium may include an oxidant, such as a portion of the oxidant flow corresponding to the above-mentioned environmental parameters at the second injector. In certain embodiments, operating the fuel system under the second fuel flow condition 420 includes operating the fuel system under conditions where thermal decomposition of deposits occurs in the second injector.

[0042] At 1040, the method 1000 includes operating the fuel system at a third fuel flow condition, such as depicted at 430 in the graph 400, after operating the fuel system at the second fuel flow condition at 1030. The third fuel flow condition 430 includes a third fuel flow rate A of the first fuel flow through the first injector of the fuel nozzle and a third fuel flow rate B of the second fuel flow through the second injector of the fuel nozzle. In various embodiments, the method 1000 includes transitioning from the second fuel flow condition 420 to the third fuel flow condition 430, such as depicted at 429 in the graph 400, at 1035. In various embodiments, the method 1000 occurs at 1035 while maintaining a substantially equal or unchanged fuel-oxidant ratio at the combustion chamber during the transition from the first fuel flow condition 410 to the second fuel flow condition 420.

[0043] In some cases, the third fuel flow condition 430 is substantially similar to the first fuel flow condition 410. For example, the third fuel flow condition 430 may include setting or returning the second fuel flow through the second injector at a condition that is substantially similar or equal to the second fuel flow corresponding to the first fuel flow condition 410. In addition, the third fuel flow condition 430 may include setting or returning the first fuel flow through the first injector at a fuel parameter that is substantially similar or equal to the first fuel flow corresponding to the first fuel flow condition 410.

[0044] However, in other embodiments, it should be understood that since the thermally decomposed deposits should be removed as the fuel flow through the second injector increases from the second fuel flow condition 420 to the third fuel flow condition 430, the third fuel flow condition 430 may generally differ in pressure, flow, or another fuel parameter due to an increase in the efficiency of the fuel system, fuel nozzle, combustion section, and / or engine. In various embodiments, the first fuel flow condition 410 includes a first pre-cleaning pressure parameter at the second injector. The third fuel flow condition 430 includes a first post-cleaning pressure parameter at the second injector. The first post-cleaning pressure parameter is less than the pre-cleaning pressure parameter. In some cases, the pre-cleaning pressure parameter and the post-cleaning pressure parameter correspond to a delta pressure (dP) between the outlet of the fuel nozzle (e.g., the pressure of the combustion chamber) and, for example, the upstream fuel pressure at the fuel system. A decrease in dP may indicate a cleaned fuel injector. However, in some embodiments, method 1000 may include returning from step 1040 to step 1030, or from step 1040 to step 1020 and then step 1030, or from step 1040 to step 1020, step 1025, step 1030, and then back to 1035, thereby repeating the cleaning process at a second injector, for example.

[0045] In still other various embodiments, the first fuel flow condition 410 including the pre-purge pressure parameter and the third fuel flow condition 430 including the post-purge pressure parameter together include substantially equal pre-purge fuel flow rates relative to the post-purge fuel flow rates.

[0046] In various embodiments, the method 1000 includes operating the fuel system at a fourth fuel flow condition at 1050, such as depicted at 440 in the graph 400. The fourth fuel flow condition 440 includes a fourth fuel flow rate A of the first fuel flow through the first injector and a fourth fuel flow rate B of the second fuel flow through the second injector. The fourth fuel flow rate A is less than the first fuel flow rate A, while the fourth fuel flow rate B is greater than the first fuel flow rate B. The fuel-oxidant ratio at the combustion chamber is approximately equal between the first fuel flow rate condition 410 and the fourth fuel flow rate condition 440. In various embodiments, the fuel-oxidant ratio at the combustion chamber is equal between the first fuel flow condition 410 and the fourth fuel flow condition 440, such as described with respect to the method 1000 at 1020, 1030, or 1040.

[0047] In certain embodiments of the method 1000 at 1050, the fourth fuel flow rate A is zero. In still certain cases, the fourth fuel flow rate B is approximately equal to the total fuel flow at the combustion chamber corresponding to the fuel-oxidant ratio at the combustion chamber, such as described with respect to the method 1000 at 1020, 1030, or 1040. In one embodiment, the method 1000 also includes transitioning from the third fuel flow condition 430 to the fourth fuel flow condition 440 at 1045, such as described at 439 in the graph 400. In various embodiments, the method 1000 occurs at 1045 while maintaining the fuel-oxidant ratio at the combustion chamber approximately equal or unchanged during the transition from the third fuel flow condition 430 to the fourth fuel flow condition 440. In various embodiments, the execution of the method 1000 at 1045 is similar to the description of step 1025 or 1035.

[0048] In still other certain embodiments, the method 1000 includes, at 1060, operating the fuel system at a fifth fuel flow condition, such as depicted at 450 in the graph 400. The method 1000 may include operating the fuel system at a fifth fuel flow condition 450 after operating the fuel system at the fourth fuel flow condition 440. The fifth fuel flow condition 450 includes a fifth fuel flow rate A of the first fuel flow through the first injector and a fifth fuel flow rate B of the second fuel flow through the second injector. In some cases, the fifth fuel flow condition 450 may be substantially equal to one or more of the first fuel flow condition 410 or the third fuel flow condition 430.

[0049] However, in other embodiments, such as for the reasons described with respect to the first fuel flow condition 410 and the third fuel flow condition 430, it should be understood that since the thermally decomposed deposits should be removed as the fuel flow through the first injector increases from the fourth fuel flow condition 440 to the fifth fuel flow condition 450, the fifth fuel flow condition 450 may generally differ in pressure, flow, or another fuel parameter due to an increase in efficiency of the fuel system, fuel nozzle, combustion section, and / or engine. In various embodiments, the first fuel flow condition 410 includes a second pre-cleaning pressure parameter relative to the first injector. The fifth fuel flow condition 450 includes a second post-cleaning pressure parameter relative to the first injector. The second post-cleaning pressure parameter at the first injector is less than the second pre-cleaning pressure parameter at the first injector. In certain embodiments, the pre-cleaning pressure parameter and the post-cleaning pressure parameter correspond to a delta pressure (dP) between the outlet of the fuel nozzle (e.g., the pressure of the combustion chamber) and the upstream fuel pressure (e.g., the pressure of the fuel system). A decrease in dP may indicate a cleaned fuel injector. However, in some embodiments, method 1000 may include returning from step 1060 to step 1050, or returning from step 1060 to step 1040 and then to step 1050, or returning from step 1060 to step 1040, step 1045 and then to step 1050, for example, repeating the cleaning process at the first injector.

[0050] In still other specific embodiments, the fifth fuel flow condition 450 may correspond to a new or changed nominal fuel flow condition that is different from another nominal fuel flow condition (e.g., at the first fuel flow condition 410). For example, when the fifth fuel flow condition 450 follows one or two purge steps (e.g., at the second fuel flow condition 420 and the fourth fuel flow condition 440), the fifth fuel flow condition 450 may correspond to a condition when the engine 15, propulsion system 10, or aircraft 100 may be operating normally, or a condition after the engine 15, propulsion system 10, or aircraft 100 may be operating normally.

[0051] In one embodiment, the method 1000 also includes transitioning from the fourth fuel flow condition 440 to the fifth fuel flow condition 450 at 1055, as depicted at 449 in the graph 400. In various embodiments, the method 1000 occurs at 1055 while maintaining the fuel-oxidant ratio at the combustion chamber approximately equal or unchanged during the transition from the fourth fuel flow condition 440 to the fifth fuel flow condition 450. In various embodiments, the execution of the method 1000 at 1055 is similar to that described with respect to steps 1025, 1035, or 1045.

[0052] It should be appreciated that in various embodiments, the method 1000 includes substantially simultaneously adjusting the fuel flow rate A and the fuel flow rate B to maintain a substantially stable fuel-oxidant ratio at the combustion chamber when transitioning between fuel flow conditions as described herein. It should be further appreciated that simultaneously adjusting or transitioning may include changing the fuel flow rates at different absolute rates of increase or decrease to allow for a substantially uniform or steady-state fuel-oxidant ratio at the combustion chamber.

[0053] Various embodiments of method 1000 described with respect to one or more of steps 1020, 1025, 1030, 1035, 1040, 1045, or 1050, or other steps that may be described herein, may include operating a compressor section to generate and provide an oxidant flow defining a first oxidant flow condition, as described with respect to step 1010. In certain embodiments, the first oxidant flow condition corresponds to a steady-state inlet condition of the oxidant entering the compressor section. The steady-state inlet condition of the oxidant entering the compressor section may correspond to a steady-state inlet condition of the oxidant entering the compressor section (e.g., at or near inlet 18, or generally at Figure 2 One or more of a substantially stable or unchanging ambient temperature, pressure, density, humidity, or other ambient environmental parameter of the oxidant (e.g., ambient air) in front of or upstream of the compressor section 42 and / or fan assembly 14 described in .

[0054] In some embodiments, the substantially steady-state condition may generally correspond to substantially level flight or a constant altitude or attitude. In one embodiment, the steady-state inlet condition corresponds to a cruise condition of an aircraft including an engine configured to perform the steps of method 1000. In other embodiments, the steady-state inlet condition may correspond to an idle operating condition, such as during ground operation of the aircraft or engine, or during in-flight or high-altitude low-power operation of the engine. However, in still other embodiments, the steady-state inlet condition may correspond to a partial power operating condition (e.g., climb, descent, approach, etc., or generally less than 100% power) or a full power operating condition (e.g., takeoff power).

[0055] In another embodiment, method 1000 may include operating the compressor section to generate or provide an oxidant flow at an initial oxidant flow condition at 1005, wherein the initial oxidant flow condition precedes the first oxidant flow condition. In certain embodiments, the initial oxidant flow condition corresponds to a transient inlet condition of the oxidant entering the compressor section. For example, the transient inlet condition of the oxidant may correspond to a change in the ambient oxidant condition entering the compressor section. The transient inlet condition may correspond to a change in the temperature, pressure, density, humidity, or other ambient environmental parameter of the oxidant (e.g., ambient air) entering the compressor section. The transient inlet condition may correspond to a change in the attitude altitude of an aircraft including an engine configured to perform the steps of method 1000.

[0056] Referring back to chart 400, certain embodiments of method 1000 include operating the fuel system and the compressor section within a time period corresponding to one or more operating modes described herein. In various embodiments, a time period may be applied to each respective fuel flow condition, such as depicted with respect to 410, 420, 430, 440, 450. The time period may include a predetermined time period at one or more respective steps 1030, 1050, during which a thermal decomposition of the fuel or other substance in the respective fuel injector may be formed. In certain other embodiments, the time period is defined by a time threshold corresponding to a health parameter of one or more components of the combustion section and / or a downstream component (e.g., a turbine section). In various embodiments, the health parameter of one or more components corresponds to an expected life or retention parameter of a combustor heat shield, a combustor liner, a fuel nozzle, a turbine nozzle, a vane or blade, or a thermal barrier coating (TBC) or a low observable coating, or other applicable components at or downstream of the combustion section.

[0057] Various embodiments of the method 1000 include, at 1031, flowing a purge fluid through the second injector during the second flow condition at step 1030. In certain embodiments, the flowing purge fluid removes fuel remaining in the second injector after the second fuel flow is reduced to zero. In various other embodiments, the method 1000 includes, at 1051, flowing a purge fluid through the first injector during the fourth flow condition at step 1050. Accordingly, the flowing purge fluid removes fuel remaining in the first injector after the first fuel flow is reduced to zero. In certain other embodiments, the purge fluid is one or more flows of an inert gas, an oxidant, or other suitable fluid exhausted through the second fuel nozzle. In an exemplary embodiment, the purge fluid is provided from the fuel system 90, for example, via the first conduit 95 or the second conduit 96. The methods 1000 at 1031, 1051 can allow for substantial removal of liquid fluid from each injector, for example, to allow thermal decomposition of fuel deposits (e.g., fuel coke) for a period of time before reintroducing fuel through each injector.

[0058] In certain embodiments, method 1000 includes, at 1033, flowing a purge fluid through the second injector during or after the second fuel flow condition at step 1030. In still other embodiments, method 1000 includes, at 1053, flowing a purge fluid through the first injector during or after the fourth fuel flow condition at step 1050. In still other embodiments of method 1000, at 1033 or 1053, flowing a purge fluid through the fuel injector includes flowing a purge fluid continuously or intermittently through the respective fuel injector for a period of time before operating the fuel system at a next fuel flow condition. In still other embodiments, method 1000 at 1033 occurs for a period of time after the step at 1031. In other embodiments, method 1000 at 1053 occurs after a period of time after the step at 1051.

[0059] In various embodiments, the purge fluid is an oxidant stream comprising a first oxidant flow condition as described herein. In certain embodiments, the fuel nozzle comprises one or more features configured to create a local static pressure difference between a portion of the fuel injector proximal to the combustion chamber and a portion distal to the combustion chamber. Such features may be included at the fuel injector, such as a ramp, opening, groove, recess, channel, or conduit at or near a flow path of the fuel through the fuel injector.

[0060] In other embodiments, the purge fluid is a continuous or intermittent flow of liquid and / or gaseous fuel, such as to provide a relatively high pressure purge through each fuel injector when an increased or nominal level of fuel is reintroduced into the combustion chamber through the fuel injector. In some embodiments, the purge fluid includes one or more high pressure pulses of fuel through the fuel injector to remove thermally decomposed deposits from the fuel injector.

[0061] In certain embodiments, method 1000 includes determining, at 1015, whether operating the compressor section at the first oxidant flow condition at 1010 and operating the fuel system at one or more of the fuel flow conditions described with respect to steps 1020, 1025, 1030, 1035, 1040, 1045, 1050, 1055, or 1060 or other steps herein is within a purge envelope. In one embodiment, the purge envelope indicates that the oxidant flow is at the first oxidant flow condition as described herein, the first fuel flow is at a steady state condition for a predetermined period of time, and further includes a health parameter as described herein. In certain embodiments, the health parameter corresponds to a compressor section outlet temperature (e.g., T3) of the oxidant flow. oxidizer ), the compressor section outlet pressure of the oxidant stream (e.g., P3 oxidizer ), the compressor section outlet flow rate of the oxidant stream (e.g., W3 oxidizer ), the fuel-oxidant ratio at the combustion chamber, the first fuel flow conditions (e.g., W fuelA , P fuelA 、T fuelA etc., W fuelB , P fuelB 、T fuelB In certain embodiments, after determining that the first oxidant flow condition and the first fuel flow condition 410 are within the purge envelope, the fuel system is operated under the second fuel flow condition 420.

[0062] In still other certain embodiments, the purge envelope indicates that the engine 15 and / or aircraft 100 is in an operating condition or environmental condition that allows the steps of method 1000 to be performed within limitations associated with certain emissions or noise limits, as described herein. In various embodiments, the purge envelope provides a threshold at which adjustments to the operation of the engine, such as through different fuel flow conditions, can be performed while operating within desired emissions and / or noise limits. In certain embodiments, the purge envelope can limit the time period for which one or more fuel flow conditions are operated based on certain emissions and / or noise limits during engine or aircraft operation.

[0063] refer to Figure 1-3, the aircraft 100, the engine 15, and / or the fuel system 90 may include a controller 210 configured to perform one or more steps of the embodiments of the method 1000 provided herein. In various embodiments, the controller 210 may generally correspond to any suitable processor-based device, including one or more computing devices. For example, Figure 2 One embodiment of suitable components that may be included in controller 210 is shown. Figure 2 As shown, the controller 210 may include a processor 212 and associated memory 214 configured to perform various computer-implemented functions. In various embodiments, the controller 210 may be configured to operate the aircraft 100, the propulsion system 10, the engine 15, and / or the fuel system 90 including the fuel nozzle 60, as shown and described herein, and as per one or more steps of the method 1000.

[0064] As used herein, the term "processor" refers not only to what is referred to in the art community as an integrated circuit included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and other programmable circuits. In addition, the memory 214 may generally include memory elements, including but not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), compact disk read-only memory (CD-ROM), magneto-optical disk (MOD), digital versatile disk (DVD), and / or other suitable memory elements or combinations thereof. In various embodiments, the controller 210 may include one or more of a full authority digital engine controller (FADEC), a propeller control unit (PCU), an engine control unit (ECu), or an electronic engine control (EEC). In various other embodiments, the controller 210 may define a distributed network of controllers 210, or a distributed network of shared, dedicated, or grouped processors 212, or a storage network of memories 214 networked in a clustered manner at the aircraft 100, propulsion system 10, or engine 15, or at a location physically separated or remote therefrom (e.g., on the ground or at a satellite location).

[0065] As shown, the controller 210 may include control logic 216 stored in the memory 214. For example, the control logic 216 may define firmware configured to execute instructions for cleaning the fuel nozzles during operation of the engine, such as the instructions provided with respect to one or more steps of the method 1000. The control logic 216 may include instructions that, when executed by the one or more processors 212, cause the one or more processors 212 to perform operations, such as the steps of the method 1000 described and described herein.

[0066] In various embodiments, the controller 210 may include in the memory 214 predetermined tables, graphs, schedules, functions, steering or feedback functions, etc. of fuel flow conditions, transition rates or transition change rates between fuel flow conditions, fuel parameters, cleaning envelopes, environmental parameters, health parameters, or time periods for performing one or more steps of method 1000.

[0067] In addition, if Figure 2 As shown, the controller 210 may also include a communication interface module 230. In various embodiments, the communication interface module 230 may include relevant electronic circuits (e.g., interface circuits) for sending and receiving data. Therefore, the communication interface module 230 of the controller 210 may be used to receive data from the aircraft 100, the propulsion system 10, the engine 15, and / or the fuel system 90, such as, but not limited to, the compressor section outlet temperature of the oxidant flow (e.g., T3 oxidizer) , the compressor section outlet pressure of the oxidant stream (e.g., P3 oxidizer ), the compressor section outlet flow rate of the oxidant stream (e.g., W3 oxidizer ), the fuel-oxidant ratio of the combustion chamber, the first fuel flow conditions (e.g., W fuelA , P fuelA 、T fuelA etc., W fuelB , P fuelB 、T fuelB ), fuel parameters, cleaning envelopes, environmental parameters, health parameters, or timers associated with one or more time periods described herein, etc. The communication interface module 230 can send and receive data to the control logic 216 stored in the memory 214, among other things.

[0068] It should be understood that the communication interface module 230 can be any combination of suitable wired and / or wireless communication interfaces, and thus can be communicatively coupled via wired and / or wireless connections to one or more components of the aircraft 100, propulsion system 10, engine 15, or fuel system 90. Thus, the controller 210 can operate, modulate, control, adjust, change, or transform the operation of the aircraft 100, propulsion system 10, engine 15, fuel nozzle 60, and / or fuel system 90, for example, according to one or more steps of the method 1000 provided herein.

[0069] Various embodiments of the engine 15, fuel system 90, aircraft 100, controller 210 and method 1000 provided herein can provide advantageous improvements to engine operation by allowing fuel nozzle cleaning during engine operation. Improvements include allowing fuel nozzle cleaning without an external pressure system, an external cleaning system or an external cleaning medium, such as by thermally decomposing deposits or decomposing deposits into lighter volatile substances that can be discharged from the fuel nozzle. Embodiments of the method can be performed regularly during engine operation, such as within a predetermined time, to, for example, reduce the accumulation of carbon or other particulate matter at the fuel nozzle. In addition or alternatively, improvements include reducing or eliminating maintenance tasks related to removing or replacing fuel nozzles from the engine for cleaning. In addition, for example, by reducing or eliminating uneven fuel nozzle spray patterns, reducing circumferential and / or radial thermal gradient changes (such as reducing hot spots), or reducing other conditions that may cause uneven or increased wear or deterioration of certain combustion sections or turbine section components, embodiments of the systems and methods provided herein can improve the life, durability, maintenance and / or performance of other combustion section and / or turbine section components.

[0070] Although described with respect to a propulsion gas turbine engine, the systems and methods described and described herein may be generally applicable to turbines, gas turbines, Brayton cycle machines, or heat engines, which typically include a fuel nozzle having a first fuel circuit, conduit, or injector that is separately controllable from a second fuel circuit, conduit, or injector. In addition, or alternatively, embodiments of the systems and methods provided herein may be applied to non-propulsion engines, such as, but not limited to, industrial gas turbine engines, auxiliary power units, marine gas turbine engines, land-based gas turbine engines, etc. In this context, it should be understood that the emissions or noise limitations described herein with respect to aircraft (e.g., LTO cycles) may utilize other emissions or noise limitations, such as, but not limited to, limitations typically associated with greenhouse gases, local regulations, or other regulations.

[0071] However, while embodiments of the systems and methods provided herein may be applicable to non-propulsion engines, it should be understood that certain specific advantages provided herein may be applicable to propulsion systems during operation or during flight that may not be permitted or considered by non-propulsion engine wash systems or methods. Furthermore, it should be understood that engine operation during flight and methods thereof, including changes between transient inlet conditions and steady-state inlet conditions as described herein, present different complexities and potential issues than non-propulsion engines or non-aviation system engines.

[0072] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims.

[0073] Further aspects of the invention are provided by the subject matter of the following clauses.

[0074] 1. A heat engine, the heat engine comprising a compressor section, the compressor section being configured to provide an oxidant flow to a combustion chamber; a fuel nozzle, the fuel nozzle comprising a first injector and a second injector, wherein the fuel nozzle is configured to provide a first fuel flow to the combustion chamber through the first injector and to provide a second fuel flow to the combustion chamber through the second injector; a fuel system, the fuel system comprising a first conduit in fluid communication with the first injector and a second conduit in fluid communication with the second injector, wherein the fuel system is configured to variably provide the first fuel flow and to be separated from the second fuel flow; and a controller, the controller being configured to perform operations, the operations comprising: operating the compressor section to provide the oxidant flow to the combustion chamber under a first oxidant flow condition; operating the fuel system under the first fuel flow condition, wherein the first fuel flow condition comprises a first fuel flow rate A of the first fuel flow through the first injector and a first fuel flow rate B of the second fuel flow through the second injector, and wherein the first fuel flow condition provides a fuel-oxidizer ratio at the combustion chamber including the first fuel flow and the second fuel flow; operating the fuel system under a second fuel flow condition, wherein the second fuel flow condition includes a second fuel flow rate A of the first fuel flow through the first injector and a second fuel flow rate B of the second fuel flow through the second injector, wherein the second fuel flow condition provides the fuel-oxidizer ratio at the combustion chamber that is equal under the first fuel flow condition and the second fuel flow condition; and after operating the fuel system under the second fuel flow condition, operating the fuel system under a third fuel flow condition, wherein the third fuel flow condition includes a third fuel flow rate A of the first fuel flow through the first injector and a third fuel flow rate B of the second fuel flow through the second injector.

[0075] 2. A thermal engine according to any provision of the present invention, wherein the second fuel flow rate A is greater than the first fuel flow rate A, and wherein the second fuel flow rate B is less than the first fuel flow rate B, and wherein under the first fuel flow condition and the second fuel flow condition, the fuel-oxidant ratio at the combustion chamber is approximately equal.

[0076] 3. A thermal engine according to any clause of the present invention, wherein the second fuel flow rate B is zero, and wherein the second fuel flow rate A is approximately equal to the total fuel flow at the combustion chamber, the total fuel flow corresponding to the fuel-oxidant ratio at the combustion chamber.

[0077] 4. A heat engine according to any clause herein, said operation comprising: flowing a purge fluid through said second injector during or after said second fuel flow condition.

[0078] 5. The heat engine according to any clause herein, wherein flowing the purge fluid through the second ejector comprises flowing the purge fluid through the second ejector continuously or intermittently.

[0079] 6. A heat engine according to any clause herein, wherein said first fuel flow condition and said first oxidant flow condition together correspond to a cruise operating condition.

[0080] 7. A heat engine according to any clause herein, wherein the first oxidant flow condition corresponds to a steady-state inlet condition of the oxidant entering the compressor section.

[0081] 8. A heat engine according to any clause herein, wherein the steady-state inlet condition corresponds to an idle operating condition, a part power operating condition or a full power operating condition.

[0082] 9. A heat engine according to any clause herein, wherein the operation comprises operating the compressor section to provide the oxidant flow under an initial oxidant flow condition, wherein the initial oxidant flow condition precedes the first oxidant flow condition.

[0083] 10. A heat engine according to any clause herein, wherein the initial oxidant flow conditions correspond to instantaneous inlet conditions of the oxidant entering the compressor section.

[0084] 11. A thermal engine according to any provision of the present invention, wherein the operation includes: operating the fuel system under a fourth fuel flow condition, wherein the fourth fuel flow condition includes a fourth fuel flow rate A of the first fuel flow through the first injector and a fourth fuel flow rate B of the second fuel flow through the second injector, and wherein the fourth fuel flow rate A is less than the first fuel flow rate A, and wherein the fourth fuel flow rate B is greater than the first fuel flow rate B, and wherein in the first fuel flow condition and the fourth fuel flow condition, the fuel-oxidant ratio at the combustion chamber is approximately equal.

[0085] 12. A thermal engine according to any clause of the present invention, wherein the fourth fuel flow rate A is zero and the fourth fuel flow rate B is approximately equal to the total fuel flow at the combustion chamber, the total fuel flow corresponding to the fuel-oxidant ratio at the combustion chamber.

[0086] 13. A heat engine according to any clause herein, wherein operation comprises flowing a purge fluid through the first injector during or after the fourth fuel flow condition.

[0087] 14. A heat engine according to any clause herein, wherein flowing the purge fluid through the first ejector comprises flowing the purge fluid through the first ejector continuously or intermittently.

[0088] 15. A thermal engine according to any provision of the present invention, wherein the operation includes: after operating the fuel system under the fourth fuel flow condition, operating the fuel system under a fifth fuel flow condition, wherein the fifth fuel flow condition includes a fifth fuel flow rate A of the first fuel flow through the first injector and a fifth fuel flow rate B of the second fuel flow through the second injector.

[0089] 16. A thermal engine according to any provision of the present invention, wherein the operation includes: transitioning from the first fuel flow condition to the second fuel flow condition, wherein the fuel-oxidant ratio at the combustion chamber is approximately equal during the transition from the first fuel flow condition to the second fuel flow condition.

[0090] 17. A thermal engine according to any provision of the present invention, wherein the operation includes: transitioning from the second fuel flow condition to the third fuel flow condition, wherein the fuel-oxidant ratio at the combustion chamber is approximately equal during the transition from the second fuel flow condition to the third fuel flow condition.

[0091] 18. A heat engine according to any clause herein, wherein the first fuel flow condition comprises a pre-purge pressure parameter, and wherein the third fuel flow condition comprises a post-purge pressure parameter, and wherein the post-purge pressure parameter is less than the pre-purge pressure parameter.

[0092] 19. A heat engine according to any clause herein, wherein the first fuel flow condition comprises a pre-purge flow rate and the third fuel flow condition comprises a post-purge flow rate, and wherein the pre-purge flow rate is equal to the post-purge flow rate.

[0093] 20. A heat engine according to any clause herein, wherein the first injector corresponds to one or more main fuel injectors, and wherein the second injector corresponds to one or more pilot fuel injectors.

[0094] 21. In a thermal engine according to any provision of the present invention, operation includes determining whether operating the compressor section under a first oxidant flow condition and operating the fuel system under a first fuel flow condition are within a purge envelope, wherein the purge envelope includes the compressor section outlet temperature of the oxidant flow, the compressor section outlet pressure of the oxidant flow, the ratio of the total fuel flow and the oxidant flow at the combustion chamber, or one or more of the first fuel flow conditions.

[0095] 22. A heat engine according to any clause herein, wherein after determining that the first oxidant flow condition and the first fuel flow condition are within the purge envelope, the fuel system is operated at a second fuel flow condition.

[0096] 23. A controller for a heat engine, the controller being configured to perform operations comprising operating the compressor section under a steady-state inlet condition of oxidant entering the compressor section to provide an oxidant flow to a combustion chamber under a first oxidant flow condition; operating the fuel system under a first fuel flow condition, wherein the first fuel flow condition comprises a first fuel flow rate A of a first fuel flow through a first injector at a fuel nozzle and a first fuel flow rate B of a second fuel flow through a second injector at the fuel nozzle, and wherein the first fuel flow condition provides a fuel-oxidant ratio at a combustion chamber comprising the first fuel flow and the second fuel flow; operating the fuel system under a second fuel flow condition A fuel system is provided wherein the compressor section is operated under a first oxidant flow condition while operating the compressor section under a first oxidant flow condition, wherein a second fuel flow condition includes a second fuel flow rate A of the first fuel flow through the first injector and a second fuel flow rate B of the second fuel flow through the second injector, wherein the second fuel flow condition provides an equal fuel-oxidant ratio between the first fuel flow condition and the second fuel flow condition at the combustion chamber; and after operating the fuel system under the second fuel flow condition, operating the fuel system under a third fuel flow condition, wherein the third fuel flow condition includes a third fuel flow rate A of the first fuel flow through the first injector and a third fuel flow rate B of the second fuel flow through the second injector.

[0097] 24. In a controller according to any provision of the present invention, operation includes determining whether operating the compressor section under a first oxidant flow condition and operating the fuel system under a first fuel flow condition are within a purge envelope, wherein the purge envelope includes a compressor section outlet temperature of the oxidant flow, a compressor section outlet pressure of the oxidant flow, a fuel-oxidant ratio at the combustion chamber, or one or more of the first fuel flow condition.

[0098] 25. A controller according to any clause herein, wherein after determining that the first oxidant flow condition and the first fuel flow condition are within the purge envelope, the fuel system is operated at the second fuel flow condition.

[0099] 26. In a controller according to any provision of the present invention, operation includes operating the fuel system under a fourth fuel flow condition while operating the compressor section under a first oxidant flow condition, wherein the fourth fuel flow condition includes a fourth fuel flow rate A of a first fuel flow provided to a first injector and a fourth fuel flow rate B of a second fuel flow through a second injector, wherein the fourth fuel flow condition provides a fuel-oxidizer ratio to the combustion chamber, and the fourth fuel flow rate A is less than the first fuel flow rate A, the fourth fuel flow rate B is greater than the first fuel flow rate B, and the fuel-oxidizer ratio of the combustion chamber is approximately equal under the first fuel flow condition and the fourth fuel flow condition.

[0100] 27. A controller according to any clause herein, operation comprising simultaneously adjusting fuel flow rate A and fuel flow rate B to maintain an approximately constant fuel-oxidant ratio in the combustion chamber when transitioning between two or more fuel flow conditions.

[0101] 28. A method for cleaning a fuel nozzle during engine operation, the method comprising one or more steps of the operations of any clause herein.

[0102] 29. A method for cleaning a fuel nozzle during aircraft flight operations, the method comprising one or more steps of the operations of any clause herein.

[0103] 30. An aircraft comprising a propulsion system comprising a heat engine as claimed in any clause herein.

[0104] 31. An aircraft comprising a heat engine, the heat engine comprising a controller as claimed in any clause herein.

[0105] 32. An aircraft comprising a controller as claimed in any clause herein.

[0106] 33. A propulsion system comprising a controller as claimed in any of the clauses herein.

Claims

1. A heat engine (15), characterized in that: The heat engine (15) comprises: a compressor section (42) configured to provide a flow of oxidant (22) to a combustion chamber (72); a fuel nozzle (60), the fuel nozzle (60) comprising a first injector (61) and a second injector (62), wherein the fuel nozzle (60) is configured to provide a first fuel flow (91) to the combustion chamber (72) through the first injector (61) and to provide a second fuel flow (92) to the combustion chamber (72) through the second injector (62); a fuel system (90) configured to provide a first fuel flow (91) to the first injector (61) and a second fuel flow (92) to the second injector (62), wherein the fuel system (90) is configured to variably provide the first fuel flow (91) to the first injector (61) and separate from the second fuel flow (92) to the second injector (62); and A controller (210), the controller (210) being configured to perform operations, the operations comprising: operating the compressor section (42) to provide the oxidant (22) flow to the combustion chamber (72) under a first oxidant (22) flow condition; operating the fuel system (90) under a first fuel flow condition (410), wherein the first fuel flow condition (410) includes a first fuel flow (91) rate A through the first injector (61) and a first fuel flow (91) rate B through the second injector (62), and wherein the first fuel flow condition (410) provides a fuel-oxidizer ratio (403) at the combustion chamber (72) including the first fuel flow (91), the second fuel flow (92), and an oxidizer flow (22), wherein the first fuel flow condition (410) and the first oxidizer (22) flow condition together correspond to a cruise operating condition; operating the fuel system (90) under a second fuel flow condition (420), wherein the second fuel flow condition (420) includes a second fuel flow (92) rate A of the first fuel flow (91) through the first injector (61) and a second fuel flow (92) rate B through the second injector (62), wherein the second fuel flow (92) rate A is greater than the first fuel flow (91) rate A and the second fuel flow (92) rate B is less than the first fuel flow (91) rate B, wherein the second fuel flow condition (420) provides the fuel-oxidizer ratio (403) at the combustion chamber (72), wherein the fuel-oxidizer ratio (403) under the first fuel flow condition (410) and the second fuel flow condition (420) are equal; and After operating the fuel system (90) under the second fuel flow condition (420), the fuel system (90) is operated under a third fuel flow condition (430), wherein the third fuel flow condition (430) includes a third fuel flow rate A of the first fuel flow (91) through the first injector (61) and a third fuel flow rate B of the second fuel flow (92) through the second injector (62).

2. The heat engine (15) according to claim 1, characterized in that wherein the second fuel flow (92) rate B is zero, and wherein the second fuel flow (92) rate A is approximately equal to the total fuel flow at the combustion chamber (72), the total fuel flow corresponding to the fuel-oxidant ratio (403) at the combustion chamber (72).

3. The heat engine (15) according to claim 2, characterized in that The operations include: During or after the second fuel flow condition (420), a purge fluid is flowed through the second injector (62).

4. The heat engine (15) according to claim 3, characterized in that in, Flowing the purge fluid through the second ejector (62) includes flowing the purge fluid through the second ejector (62) continuously or intermittently.

5. A heat engine (15) according to any one of claims 1 to 4, characterized in that: in, The first oxidant (22) flow conditions correspond to steady-state inlet (18) conditions of the oxidant (22) entering the compressor section (42).

6. The heat engine (15) according to claim 5, characterized in that The operations include: The fuel system (90) is operated under a fourth fuel flow condition (440), wherein the fourth fuel flow condition (440) includes a fourth fuel flow rate A of the first fuel flow (91) through the first injector (61) and a fourth fuel flow rate B of the second fuel flow (92) through the second injector (62), and wherein the fourth fuel flow rate A is less than the first fuel flow (91) rate A, and wherein the fourth fuel flow rate B is greater than the first fuel flow (91) rate B, and wherein in the first fuel flow condition (410) and the fourth fuel flow condition (440), the fuel-oxidizer ratio (403) at the combustion chamber (72) is approximately equal.

7. The heat engine (15) according to claim 6, characterized in that wherein the fourth fuel flow rate A is zero and the fourth fuel flow rate B is approximately equal to a total fuel flow at the combustion chamber (72), the total fuel flow corresponding to the fuel-oxidant ratio (403) at the combustion chamber (72).

8. The heat engine (15) according to claim 7, characterized in that in, The operations include: During or after the fourth fuel flow condition (440), a purge fluid is flowed through the first injector (61).

9. The heat engine (15) according to claim 8, characterized in that in, Flowing the purge fluid through the first ejector (61) includes flowing the purge fluid through the first ejector (61) continuously or intermittently.

10. The heat engine (15) according to claim 9, characterized in that The operations include: After operating the fuel system (90) under the fourth fuel flow condition (440), the fuel system (90) is operated under a fifth fuel flow condition (450), wherein the fifth fuel flow condition (450) includes a fifth fuel flow rate A of the first fuel flow (91) through the first injector (61) and a fifth fuel flow rate B of the second fuel flow (92) through the second injector (62).

11. The heat engine (15) according to claim 10, characterized in that The operations include: A transition is made from the first fuel flow condition (410) to the second fuel flow condition (420), wherein the fuel-oxidant ratio (403) at the combustion chamber (72) is approximately equal during the transition from the first fuel flow condition (410) to the second fuel flow condition (420).

12. The heat engine (15) according to claim 11, characterized in that The operations include: A transition is made from the second fuel flow condition (420) to the third fuel flow condition (430), wherein the fuel-oxidant ratio (403) at the combustion chamber (72) is approximately equal during the transition from the second fuel flow condition (420) to the third fuel flow condition (430).

13. The heat engine (15) according to claim 12, characterized in that wherein the first fuel flow condition (410) includes a pre-purge flow rate, and the third fuel flow condition (430) includes a post-purge flow rate, and wherein the pre-purge flow rate is equal to the post-purge flow rate.

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