Fuel system having a coke filtration system

A fuel system including a fuel metering unit, a heat exchanger, a plurality of fuel nozzles, and a coke filtration system. The fuel metering unit is configured to meter a flow of a hydrocarbon fuel. The heat exchanger is fluidly connected to the fuel metering unit. The heat exchanger is configured to heat the hydrocarbon fuel to improve engine performance or efficiency. The plurality of fuel nozzles is fluidly connected to the heat exchanger downstream of the heat exchanger to receive the hydrocarbon fuel heated by the heat exchanger. The coke filtration system includes at least one filter to remove coke particles in the heated fuel. The coke filtration system is located upstream of the plurality of fuel nozzles and directly downstream of the heat exchanger.

TECHNICAL FIELD

The present disclosure relates to fuel systems, particularly, fuel systems for gas turbine engines for aircraft. In more detail, the present disclosure relates to a fuel system for a gas turbine engine, the fuel system having a coke filtration system.

BACKGROUND

Gas turbine engines include surfaces that contact hydrocarbon fluids, such as fuels and lubricating oils. Carbonaceous deposits (also known as coke) may form on these surfaces when exposed to the hydrocarbon fluids at elevated temperatures, resulting in carbon becoming attached and building up as deposits on surfaces contacted by a fuel or oil.

DETAILED DESCRIPTION

Features, advantages, and embodiments of the present disclosure are set forth or apparent from a consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that the following detailed description is exemplary and intended to provide further explanation without limiting the scope of the disclosure as claimed.

The terms “directly upstream” or “directly downstream,” when used to describe the relative placement of components in a fluid pathway, refer to components that are placed next to each other in the fluid pathway without any intervening components between them other than an appropriate fluid coupling, such as a pipe, tube, valve, or the like, to fluidly couple the components. Such components may be spaced apart from each other with intervening components that are not in the fluid pathway.

The terms “coupled,” “fixed,” “attached,” “connected,” and the like, refer to both direct coupling, fixing, attaching, or connecting as well as indirect coupling, fixing, attaching, or connecting through one or more intermediate components or features, unless otherwise specified herein.

As noted above, coke deposition may occur on surfaces of a gas turbine engine that are exposed to hydrocarbon fluids, such as fuels and lubricating oils, at elevated temperatures. As the deposits collect, they can become sufficiently large to reduce or even to obstruct fluid flow. In the case of a fuel circuit, such carbon deposition can lead to degraded engine performance, reduced heat transfer efficiencies, increased pressure drops, and increased rates of material corrosion and erosion, all of which can necessitate the use of expensive de-coking procedures and even replacement of fuel nozzles. The formation of these carbonaceous deposits is accelerated at elevated temperatures, such as temperatures between four hundred degrees Fahrenheit and eight hundred degrees Fahrenheit. Heating fuel to such temperatures just prior to being injected into a combustion chamber of a gas turbine engine may be beneficial for performance reasons. To avoid coke deposition in the fuel nozzles leading to frequent replacement of the fuel nozzles, the fuel system of preferred embodiments discussed herein use a filtration system between a heat exchanger used to heat the fuel and the fuel nozzles to remove coke before the coke reaches the fuel nozzles.

The fuel system discussed herein is particularly suitable for use in engines, such as a gas turbine engine used on an aircraft.FIG.1is a perspective view of an aircraft10that may implement various preferred embodiments. The aircraft10includes a fuselage12, wings14attached to the fuselage12, and an empennage16. The aircraft10also includes a propulsion system that produces a propulsive thrust required to propel the aircraft10in flight, during taxiing operations, and the like. The propulsion system for the aircraft10shown inFIG.1includes a pair of engines100. In this embodiment, each engine100is attached to one of the wings14by a pylon18in an under-wing configuration. Although the engines100are shown attached to the wing14in an under-wing configuration inFIG.1, in other embodiments, the engine100may have alternative configurations and be coupled to other portions of the aircraft10. For example, the engine100may additionally or alternatively include one or more aspects coupled to other parts of the aircraft10, such as, for example, the empennage16, and the fuselage12.

As will be described further below with reference toFIG.2, the engines100shown inFIG.1are gas turbine engines that are each capable of selectively generating a propulsive thrust for the aircraft10. The amount of propulsive thrust may be controlled at least in part based on a volume of fuel provided to the gas turbine engines100via a fuel system200(seeFIG.3). An aviation turbine fuel in the embodiments discussed herein is a combustible hydrocarbon liquid fuel, such as a kerosene-type fuel, having a desired carbon number, a synthetic aviation fuel, a biofuel, a biodiesel, an ethanol, a bioalcohol, and the like. The fuel is stored in a fuel tank210of the fuel system200. As shown inFIG.1, at least a portion of the fuel tank210is located in each wing14and a portion of the fuel tank210is located in the fuselage12between the wings14. The fuel tank210, however, may be located at other suitable locations in the fuselage12or the wing14. The fuel tank210may also be located entirely within the fuselage12or the wing14. The fuel tank210may also be separate tanks instead of a single, unitary body, such as, for example, two tanks each located within a corresponding wing14.

Although the aircraft10shown inFIG.1is an airplane, the embodiments described herein may also be applicable to other aircraft, including, for example, helicopters and unmanned aerial vehicles (UAV). Preferably, the aircraft discussed herein are fixed-wing aircraft or rotor aircraft that generate lift by aerodynamic forces acting on, for example, a fixed wing (e.g., wing14) or a rotary wing (e.g., rotor of a helicopter), and are heavier-than-air aircraft, as opposed to lighter-than-air aircraft (such as a dirigible). Further, although not depicted herein, in other embodiments, the gas turbine engine may be any other suitable type of gas turbine engine, such as an industrial gas turbine engine incorporated into a power generation system, a nautical gas turbine engine, etc.

FIG.2is a schematic, cross-sectional view of one of the engines100used in the propulsion system for the aircraft10shown inFIG.1. The cross-sectional view ofFIG.2is taken along line2-2inFIG.1. For the embodiment depicted inFIG.2, the engine100is a high bypass turbofan engine. The engine100may also be referred to as a turbofan engine100herein. The turbofan engine100has an axial direction A (extending parallel to a longitudinal centerline101, shown for reference inFIG.2), a radial direction R (extending perpendicular to the longitudinal centerline101, shown for reference inFIG.2), and a circumferential direction. The circumferential direction (not depicted inFIG.2) extends in a direction rotating about the axial direction A. The turbofan engine100includes a fan section102and a turbomachine104disposed downstream from the fan section102.

The turbomachine104depicted inFIG.2includes a tubular outer casing106(also referred to as a housing or nacelle) that defines an inlet108. In this embodiment, the inlet108is annular. The outer casing106encases an engine core that includes, in a serial flow relationship, a compressor section including a booster or low-pressure (LP) compressor110and a high-pressure (HP) compressor112, a combustion section150(also referred to herein as a combustor150), a turbine section including a high-pressure (HP) turbine116and a low-pressure (LP) turbine118, and a jet exhaust nozzle section120. The compressor section, the combustion section150, and the turbine section together define at least in part a core air flowpath121extending from the inlet108to the jet exhaust nozzle section120. The turbofan engine further includes one or more drive shafts. More specifically, the turbofan engine includes a high-pressure (HP) shaft or spool122drivingly connecting the HP turbine116to the HP compressor112, and a low-pressure (LP) shaft or spool124drivingly connecting the LP turbine118to the LP compressor110.

The fan section102shown inFIG.2includes a fan126having a plurality of fan blades128coupled to a disk130. The fan blades128and the disk130are rotatable, together, about the longitudinal centerline (axis)101by the LP shaft124. The LP compressor110may also be directly driven by the LP shaft124, as depicted inFIG.2. The disk130is covered by a rotatable front hub132aerodynamically contoured to promote an airflow through the plurality of fan blades128. Further, an annular fan casing or outer nacelle134is provided, circumferentially surrounding the fan126and/or at least a portion of the turbomachine104. The nacelle134is supported relative to the turbomachine104by a plurality of circumferentially spaced outlet guide vanes136. A downstream section138of the nacelle134extends over an outer portion of the turbomachine104so as to define a bypass airflow passage140therebetween.

The turbofan engine100is operable with the fuel system200and receives a flow of fuel from the fuel system200. As will be described further below, the fuel system200includes a fuel delivery assembly202providing the fuel flow from the fuel tank210to the turbofan engine100, and, more specifically, to a plurality of fuel nozzles152that inject fuel into a combustion chamber154of the combustor150.

As discussed above, the compressor section, the combustion section (combustor)150, and the turbine section form, at least in part, the core air flowpath121extending from the inlet108to the jet exhaust nozzle section120. Air entering through the inlet108is compressed by blades of a plurality of fans of the LP compressor110and the HP compressor112. At least a portion of the compressed air enters (as primary air) the forward end of the combustion chamber154of the combustor150. Fuel is injected by the fuel nozzles152into compressed air and mixed with the compressed, primary air. The fuel nozzles152of this embodiment are part of a swirler/fuel nozzle assembly. The swirler/fuel nozzle assembly includes a swirler (not shown) that is used to generate turbulence in the primary air. The fuel nozzle152injects fuel into the turbulent airflow of the primary air and the turbulence promotes rapid mixing of the fuel with the primary air. The mixture of fuel and compressed air is combusted in the combustion chamber154, generating combustion gases (combustion products), which accelerate as the combustion gases leave the combustion chamber154. The products of combustion are accelerated as the products are expelled through the outlet of the combustion chamber154to drive the engine100. More specifically, the combusted fuel air mixture is accelerated through the outlet to turn the turbines (e.g., drive the turbine blades) of the HP turbine116and the LP turbine118. As discussed above, the HP turbine116and the LP turbine118, among other things, drive the LP compressor110and the HP compressor112.

The turbofan engine100also includes various accessory systems to aid in the operation of the turbofan engine100and/or an aircraft, including the turbofan engine100. For example, the turbofan engine100may include a main lubrication system162, a compressor cooling air (CCA) system164, an active thermal clearance control (ATCC) system166, and generator lubrication system168, each of which is depicted schematically inFIG.2. The main lubrication system162is configured to provide a lubricant to, for example, various bearings and gear meshes in the compressor section, the turbine section, the HP shaft122, and the LP shaft124. The lubricant provided by the main lubrication system162may increase the useful life of such components and may remove a certain amount of heat from such components through the use of one or more heat exchangers. The compressor cooling air (CCA) system164provides air from one or both of the HP compressor112or the LP compressor110to one or both of the HP turbine116or the LP turbine118. The active thermal clearance control (ATCC) system166acts to minimize a clearance between tips of turbine blades and casing walls as casing temperatures vary during a flight mission. The generator lubrication system168provides lubrication to an electronic generator (not shown), as well as cooling/heat removal for the electronic generator. The electronic generator may provide electrical power to, for example, a startup electrical motor for the turbofan engine100and/or various other electronic components of the turbofan engine100and/or an aircraft including the turbofan engine100. The lubrication systems for the engine100(e.g., the main lubrication system162and the generator lubrication system168) may use hydrocarbon fluids, such as oil, for lubrication, in which the oil circulates through inner surfaces of oil scavenge lines.

It will be appreciated, however, that the turbofan engine100discussed herein is provided by way of example only. In other embodiments, any other suitable engine may be utilized with aspects of the present disclosure. For example, in other embodiments, the engine may be any other suitable gas turbine engine, such as a turboshaft engine, a turboprop engine, a turbojet engine, an unducted single fan engine, and the like. In such a manner, it will further be appreciated that, in other embodiments, the gas turbine engine may have other suitable configurations, such as other suitable numbers or arrangements of shafts, compressors, turbines, fans, etc. Further, although the turbofan engine100is shown as a direct drive, fixed-pitch turbofan engine100, in other embodiments, a gas turbine engine may be a geared gas turbine engine (i.e., including a gearbox between the fan126and shaft driving the fan126, such as the LP shaft124), may be a variable pitch gas turbine engine (i.e., including a fan126having a plurality of fan blades128rotatable about their respective pitch axes), etc. Further, still, in alternative embodiments, aspects of the present disclosure may be incorporated into, or otherwise utilized with any other type of engine, such as reciprocating engines. Additionally, in still other exemplary embodiments, the exemplary turbofan engine100may include or be operably connected to any other suitable accessory systems. Additionally, or alternatively, the exemplary turbofan engine100may not include or be operably connected to one or more of the accessory systems162,164,166,168, discussed above.

FIG.3is a schematic view of the fuel system200according to an embodiment of the present disclosure that is configured to store the hydrocarbon fuel for the engine100in the fuel tank210and to deliver the hydrocarbon fuel to the engine100via the fuel delivery assembly202. In the following discussion, various components are described as being fluidly connected to the fuel delivery assembly202or in fluid connection to the fuel delivery assembly202. These components are also fluidly connected or coupled to each other by, for example, the fuel delivery assembly202. Various components are also described as being positioned downstream or upstream from other components. A component positioned downstream from another component is configured to receive fuel from the other component, and, likewise, a component positioned upstream of another component is configured to provide fuel to the other component.

The fuel delivery assembly202includes tubes, pipes, conduits, and the like, to fluidly connect the various components of the fuel system200to the engine100. As noted above, the fuel tank210is configured to store the hydrocarbon fuel, and the hydrocarbon fuel is supplied from the fuel tank210to the fuel delivery assembly202. The fuel delivery assembly202is configured to carry the hydrocarbon fuel between the fuel tank210and the engine100and, thus, provides a flow path (fluid pathway) of the hydrocarbon fuel from the fuel tank210to the engine100. As noted above, the terms “downstream” and “upstream,” as used herein, may be used to describe the position of components relative to the direction of flow of the hydrocarbon fuel in the flow path of the fuel delivery assembly202. The fuel delivery assembly202may also include various valves and other components to deliver the hydrocarbon fuel to the engine100that are not shown inFIG.3.

The fuel system200includes at least one fuel pump, and, in the embodiment shown inFIG.3, a plurality of fuel pumps, fluidly connected to the fuel delivery assembly202to induce the flow of the fuel through the fuel delivery assembly202to the engine100. One such pump is a main fuel pump212. The main fuel pump212is a high-pressure pump that is the primary source of pressure rise in the fuel delivery assembly202between the fuel tank210and the engine100. The main fuel pump212may be configured to increase a pressure in the fuel delivery assembly202to a pressure greater than a pressure within the combustion chamber154of the combustor150.

The fuel system200may also include other supplementary pumps, such as an inlet pump214. The inlet pump214is a low-pressure pump that is configured to provide an initial pressurization to induce a flow of the hydrocarbon fuel through the fuel delivery assembly202. The inlet pump214may be configured to provide less of a pressure rise within the fuel delivery assembly202than the main fuel pump212. The inlet pump214may be configured to provide less than 80% of the pressure rise of the main fuel pump212, such as less than 70%, such as less than 60%, such as less than 50%, such as less than 40%, such as less than 30%, such as less than 20%, such as at least 5% of the pressure rise of the main fuel pump212.

In the embodiment shown inFIG.3, the inlet pump214is downstream of the fuel tank210and upstream of the main fuel pump212. Although the inlet pump214is shown as being located within the engine100, the inlet pump214may also be suitably located in other portions of the aircraft10such as the fuselage12, the wing14, or the pylon18. The inlet pump214induces the flow of fuel from the fuel tank210, and, then, the fuel is heated by a preheater216.

The preheater216is in fluid communication with the fuel delivery assembly202and may be any suitable heater, such as an electrical resistance heater, a catalytic heater, or a burner. In some embodiments, such as the one depicted inFIG.3, the preheater216may be a heat exchanger that is in thermal communication with any suitable heat source, such as any suitable engine and/or aircraft heat source. Such engine heat source may include, for example, the main lubrication system162, and the preheater216may be a fuel-oil heat exchanger (HX) fluidly connected to the main lubrication system162and configured to extract heat from the oil of the main lubrication system162and to heat the hydrocarbon fuel flowing through the preheater216. The preheater216is preferably configured to heat the fuel to temperatures that avoid the formation of ice in the fuel and to cool the oil of the main lubrication system162. The preheater216may be configured to heat the fuel, as measured at the outlet of the preheater216, to temperatures preferably from zero degrees Fahrenheit to two-hundred degrees Fahrenheit. Although, the preheater216is shown as being located within the engine100, the preheater216may also be suitably located in other portions of the aircraft10such as the fuselage12, the wing14, or the pylon18.

The fuel system200also includes a main filter218in fluid communication with the fuel delivery assembly202. The main filter218is configured to remove contaminates that may be present in the fuel supply and is, thus, preferably positioned close to the fuel tank210and upstream of many of the major components of the fuel system200, such as, for example, the main fuel pump212, a fuel metering unit220, a de-oxygenation system224, and a servo system228. In the embodiment depicted inFIG.3, the main filter218is positioned downstream of the fuel tank210, the inlet pump214, and the preheater216. Although the main filter218is shown as being located within the engine100, the main filter218may also be suitably located in other portions of the aircraft10such as the fuselage12, the wing14, or the pylon18. The main filter218may be any suitable filter including, for example, a mesh filter. The main filter218preferably may have a nominal micron rating from ten microns to fifty microns to remove potential contaminants.

The fuel system200also includes a fuel metering unit220in fluid communication with the fuel delivery assembly202. Any suitable fuel metering unit220may be used including, for example, a metering valve. The fuel metering unit220is positioned downstream of the main fuel pump212and upstream of a fuel manifold156configured to distribute fuel to the fuel nozzles152. The fuel system200is configured to provide fuel to the fuel metering unit220, and the fuel metering unit220is configured to receive fuel from the fuel tank210. The fuel metering unit220is further configured to provide the flow of fuel to the engine100in a desired manner. More specifically, the fuel metering unit220is configured to meter the fuel and to provide a desired volume of fuel, at, for example, a desired flow rate, to the fuel manifold156of the engine100. The fuel manifold156is fluidly connected to the fuel nozzles152and distributes (provides) the fuel received to the plurality of fuel nozzles152, where, as discussed above, the fuel is injected into the combustion chamber154and combusted. Adjusting the fuel metering unit220changes the volume of fuel provided to the combustion chamber154and, thus, changes the amount of propulsive thrust produced by the engine100to propel the aircraft10.

Fuel after fuel metering unit220may be heated further to improve gas turbine efficiency, performance, and durability. Fuel may be used as a cooling source to improve aircraft or engine components durability or used to extract heat from core air flowpath121or the CCA system164to improve engine thermodynamic efficiency. The fuel system200of this embodiment further includes a heat exchanger222, which may be referred to as performance heat exchanger (HX) herein. The performance heat exchanger222may be configured to heat the fuel to temperatures greater than three hundred fifty degrees Fahrenheit, more preferably, from four hundred degrees Fahrenheit to nine hundred degrees Fahrenheit. The performance heat exchanger222is positioned upstream of the fuel nozzles152and, more specifically, upstream of the fuel manifold156. With the high temperature fuel produced using the performance heat exchanger222, the performance heat exchanger222is preferably located close to the fuel manifold156, minimizing the number of intervening components in the fuel system200between the performance heat exchanger222and the fuel nozzles152. The performance heat exchanger222is located downstream of the fuel metering unit220and, more specifically, directly downstream of the fuel metering unit220.

The performance heat exchanger222may be a heat exchanger that is in thermal communication with any suitable heat source, such as any suitable engine and/or aircraft heat source. The heat exchanger may be in thermal communication with a hot gas path of an engine100. Such engine heat source may include, for example, a flow path of heated air through the engine100, such as the core air flowpath121. The performance heat exchanger222also may be fluidly connected to, for example, the CCA system164to cool the HP turbine116. The performance heat exchanger222may be thermally connected to other portions of the core air flowpath121(FIG.2), including the jet exhaust nozzle section120(FIG.2). Additionally, or alternatively, in other embodiments, the performance heat exchanger222may be thermally coupled to an intermediate thermal transfer system169, which is in turn thermally coupled to one or more systems of the engine100, or a flowpath for air through the engine100. The performance heat exchanger222may be thermally coupled to the intermediate thermal transfer system169to receive heat from these heat sources.

The performance heat exchanger222elevates the temperature of the hydrocarbon fuel to temperatures that, as discussed above, promote coke formation and deposition on, for example, the fuel nozzles152. To lengthen the life of the fuel nozzles152, the fuel system200of this embodiment also includes a coke filtration system230in fluid communication with the fuel delivery assembly202. The coke filtration system230is configured to collect coke before the coke deposits on other components, such as the fuel nozzles152, and will be referred to herein as a coke filtration system. In this embodiment, the coke filtration system230is positioned downstream of the performance heat exchanger222, and more specifically, directly downstream of the performance heat exchanger222, thus, collecting the coke before the coke deposits on other components. The coke filtration system230is positioned upstream of the fuel manifold156and the combustion chamber154(FIG.2). As noted above, the performance heat exchanger222is positioned close to the fuel manifold156and, in this embodiment, the coke filtration system230is positioned directly upstream of the fuel manifold156placing only the coke filtration system230between the performance heat exchanger222and the fuel manifold156.

FIG.4is a schematic of the coke filtration system230. The coke filtration system230is configured to collect the coke and may include at least one filter configured to collect the coke. In some embodiments, only a single filter may be used, but, with a single filter sized to collect fine particles of coke, the lifetime (time on wing) may be limited as particles may collect rapidly. In this embodiment, the coke filtration system230includes a plurality of filters, and, more specifically, a coarse filter232, a medium filter234, and a fine filter236. The filters232,234,236are arranged in series, with the micron rating of the filters being progressively lower corresponding to the direction of the flow of the fuel, such that the coarse filter232has a micron rating greater than the medium filter234and the medium filter234has a micron rating greater than the fine filter236. Accordingly, the coarse filter232has a micron rating larger than the fine filter236. As is known in the art and as will be used herein, micron rating describes the size of particles that a filter can capture. Larger particles in the fuel, including larger particles of coke, are first collected by the coarse filter232. The medium filter234collects some particles that pass through the coarse filter232, and the fine filter236collects the small particles of coke that pass through both the coarse filter232and the medium filter234. By such an arrangement, a fine level of filtration can be obtained, but the life of the fine filter236can be extended relative to a single filter arrangement. In some embodiments, the coarse filter232may preferably have a nominal micron rating from thirty microns to eighty microns. The medium filter234may preferably have a nominal micron rating from fifteen microns to sixty microns. As noted above, the fine filter236is preferably sized to collect small particles of coke, and the fine filter236preferably has a nominal micron rating from a half micron to forty microns.

FIG.5Ais a schematic, cross-sectional view of a filter assembly240that may be used in the coke filtration system230ofFIGS.3and4. The filter assembly240includes a filter element242that collects the small particles of coke in the fuel. The filter element242is located within a filter housing244of the filter assembly240. In the embodiment shown inFIG.5A, the filter element242and the filter housing244are cylindrical having a longitudinal direction that is in and out of the page, a radial direction orthogonal to the longitudinal direction, and a circumferential direction. The filter element242is also annular having a filter bore246in the center of the filter element242. In this embodiment, the filter bore246is circular having a longitudinal axis coincident with a longitudinal axis of the filter element242. In this embodiment, fuel flows into the filter assembly240within the filter housing244and then flows radially inward through the filter element242into the filter bore246. The filter element242has an upstream surface248, which in the embodiment shown inFIG.5A, is the circumferential surface of the filter element242that faces radially outward toward the filter housing244. Each of the filters232,234,236(FIG.4) is preferably designed to have a large surface area to maximize the lifetime of the filter, and although, in some embodiments, the filter assembly240could be designed to have fuel flow in a radially outward direction, the fuel flows in a radially inward direction to increase the surface area of the upstream surface248. In some embodiments, the upstream surface248(or even the entire filter element242) may be pleated to further increase the surface area for a given volume, as shown inFIG.5A.

As noted above with regard toFIG.4, the filters232,234,236are preferably arranged in series. In some embodiments, each of the filters232,234,236may have separate filter assemblies240. For example, the fuel may flow through an inlet of the coarse filter232, radially inward through the filter element242of the coarse filter232to the filter bore246of the coarse filter232, and then to an outlet of the coarse filter232before preceding sequentially in a similar manner through the medium filter234and the fine filter236. In other embodiments, the filter elements242of each of the coarse filter232, the medium filter234, and the fine filter236may be radially nested with each other.FIG.5Bshows such an arrangement, andFIG.5Bis a detail view showing detail5B inFIG.5A. In the arrangement illustrated byFIG.5B, the filter assembly240includes a plurality of filter elements242nested with each other. With the fuel flowing in the radially inward direction, a filter element242aof the coarse filter232(coarse filter element242a) is the outward most filter element242. A filter element242bof the medium filter234(medium filter element242b) is positioned radially inward of the coarse filter element242a, and a filter element242cof the fine filter236(fine filter element242c) is positioned radially inward of both the coarse filter element242aand the medium filter element242b. The medium filter element242bis located between the coarse filter element242aand the fine filter element242c. In this embodiment, as the fuel flows in the radially inward direction, the fuel flows sequentially through each of the coarse filter232, the medium filter234, and the fine filter236, and more specifically sequentially through each of the coarse filter element242a, the medium filter element242b, and the fine filter element242c, and then through the filter bore246of the fine filter236to the outlet of the filter assembly240.

The filter element242may have any suitable construction such as, for example, as being a mesh filter, a sintered metal filter, or a fiber metal filter. The filter element242for each of the filters232,234,236need not be the same, but instead may have different constructions. For example, the filter element242for the coarse filter232may be a mesh filter, but the filter element242for the fine filter236may be a fiber metal filter. As noted above, the filters232,234,236are exposed to high temperatures and the filter element242of each filter232,234,236is preferably made of materials suitable to withstand such an environment. When a metal is used in constructing filter element242, the metal is preferably corrosion resistant in the high temperature fuel environment, and, more specifically, has good corrosion resistance to sulfur and to sulfur compounds. Materials such as stainless steel may be avoided because of the susceptibility to corrosion at high temperatures. Suitable materials may include, for example, nickel-based alloys and more preferably nickel-chromium-based alloys, such as Inconel® alloys, for example.

As shown inFIG.3, the fuel system200also may include the de-oxygenation system224that is configured to reduce the amount of oxygen in the fuel. Oxygen in the fuel may be a contributor to thermal oxidation of the fuel and the generation of coke, particularly, at temperatures greater than three hundred degrees Fahrenheit. In this embodiment, the de-oxygenation system224is in fluid communication with the fuel delivery assembly202at a position upstream of the performance heat exchanger222such that the de-oxygenation system224reduces the oxygen content of the fuel supplied to the performance heat exchanger222. As shown inFIG.3, the de-oxygenation system224also is upstream of the fuel metering unit220and the main fuel pump212. The de-oxygenation system224is downstream of the main filter218, and, more specifically, directly downstream of the main filter218. A suitable de-oxygenation system224is the fuel oxygen reduction units shown and described in U.S. Patent Application Publication No. 2020/0140114, the disclosure of which is incorporated by reference herein in its entirety. The fuel provided by the de-oxygenation system224may have an oxygen content of less than five parts per million (“ppm”), such as less than three ppm, such as less than two ppm, such as less than one ppm, and such as less than a half ppm.

In the embodiment depicted inFIG.3, a bypass valve226is positioned in fluid communication with the fuel delivery assembly202between (downstream of) the main fuel pump212and (upstream of) the fuel metering unit220. The bypass valve226includes a bypass fluid connection that connects the bypass valve226with a position upstream of the main fuel pump212such that fuel in the fuel delivery assembly202can bypass the fuel nozzles152and other components downstream of the bypass valve226and recirculate the fuel back to the main fuel pump212.

Fuel may be used to operate various components of the engine100. A servo system228may be used for such operation. In this embodiment, the servo system228is connected to the fuel delivery assembly202at a position upstream of the bypass valve226and the fuel metering unit220and downstream of the main filter218to receive the hydrocarbon fuel from the fuel distribution assembly. In this embodiment, the connection is between the main fuel pump212and the bypass valve226. By such a position, the bypass valve226may be positioned to recirculate the fuel, and the fuel is still provided to the servo system228. A fuel return from the servo system228is connected to the fuel delivery assembly202at a position upstream of the main fuel pump212. The fuel system200may also include other components and systems not specifically depicted inFIG.3.

FIG.6is a schematic view of a portion of a fuel system300according to another embodiment of the present disclosure. In some gas turbine engines100, a plurality of sets of fuel nozzles may be used with fuel being distributed to each set of fuel nozzles by a separate fuel manifold. In the fuel system300shown inFIG.6, for example, the gas turbine engine100includes a first set of fuel nozzles318and a second set of fuel nozzles328. The components of the fuel system300shown inFIG.6upstream of the fuel metering unit220, and including the fuel metering unit220, are the same as those shown and described inFIG.3and a detailed discussion of those components is omitted here. In addition, some of those components have been omitted fromFIG.6for clarity.

The fuel system300of this embodiment includes a first fuel manifold316and a second fuel manifold326. The first fuel manifold316and the second fuel manifold326operate in a manner similar to the fuel manifold156discussed above inFIG.3. The first fuel manifold316is configured to distribute fuel to the first set of fuel nozzles318, and the second fuel manifold326is configured to distribute fuel to the second set of fuel nozzles328.

The fuel system300of this embodiment also includes a plurality of performance first heat exchangers, a first heat exchanger312and a second heat exchanger322. The first heat exchanger312and the second heat exchanger322are performance heat exchangers that operate in the same manner as the performance heat exchanger222discussed above. The fuel metering unit220is configured to provide a desired volume of fuel, at, for example, a desired flow rate, to each of the first fuel manifold316and the second fuel manifold326via the first heat exchanger312and second heat exchanger322, respectively. In this configuration, the fuel system300also includes a plurality of coke filtration systems, a first coke filtration system314and a second coke filtration system324. Each of the first coke filtration system314and the second coke filtration system324is configured to operate like the coke filtration system230discussed above and to remove coke from the fuel after the first heat exchanger312and second heat exchanger322, and before fuel is distributed to the first set of fuel nozzles318and the second set of fuel nozzles328. In this embodiment, the first coke filtration system314is positioned downstream of the first heat exchanger312and, more specifically, directly downstream of the first heat exchanger312. The first coke filtration system314is also positioned upstream of the first fuel manifold316and, more specifically, directly upstream of the first fuel manifold316. Similarly, the second coke filtration system324is positioned downstream of the second heat exchanger322and, more specifically, directly downstream of the second heat exchanger322. The second coke filtration system324is also positioned upstream of the second fuel manifold326and, more specifically, directly upstream of the second fuel manifold326.

A fuel system includes a fuel metering unit, a heat exchanger, a plurality of fuel nozzles, and a coke filtration system. The fuel metering unit is configured to meter a flow of a hydrocarbon fuel. The heat exchanger is fluidly connected to the fuel metering unit downstream of the fuel metering unit to receive the flow of the hydrocarbon fuel. The heat exchanger is configured to heat the hydrocarbon fuel. The plurality of fuel nozzles is fluidly connected to the heat exchanger downstream of the heat exchanger to receive the hydrocarbon fuel heated by the heat exchanger. The coke filtration system includes at least one filter. The coke filtration system is located upstream of the plurality of fuel nozzles and directly downstream of the heat exchanger.

The fuel system of the preceding clause, including a fuel manifold fluidly connected to the heat exchanger downstream of the heat exchanger and configured to distribute the heated fuel to the plurality of fuel nozzles. The fuel manifold is downstream of the coke filtration system.

The fuel system of any preceding clause, wherein the heat exchanger is configured to heat the hydrocarbon fuel to a temperature from three hundred degrees Fahrenheit to nine hundred degrees Fahrenheit.

The fuel system of any preceding clause, wherein the heat exchanger is thermally coupled to an intermediate thermal transfer system to receive heat from a hot gas path of an engine.

The fuel system of any preceding clause, wherein the at least one filter is a sintered metal filter or a fiber metal filter.

The fuel system of any preceding clause, wherein the at least one filter includes a filter element that is a nickel-chromium-based alloy.

The fuel system of any preceding clause, wherein the at least one filter includes a filter element having an upstream surface. The upstream surface of the filtering element is pleated.

The fuel system of any preceding clause, including a de-oxygenation system fluidly connected to the heat exchanger upstream of the fuel metering unit and configured to reduce the concentration of oxygen in the hydrocarbon fuel.

The fuel system of any preceding clause, wherein the coke filtration system includes a plurality of filters in series.

The fuel system of any preceding clause, wherein the coke filtration system includes a filter assembly and each of the plurality of filters includes an annular filter element. The filter element of a first filter being positioned radially outward from the filter element of a second filter.

The fuel system of any preceding clause, wherein the first filter is a coarse filter and the second filter is a fine filter having a micron rating less than the coarse filter, and wherein fuel is configured to flow through the filter element of each of the coarse filter and the fine filter in a radially inward direction.

The fuel system of any preceding clause, wherein the plurality of filters includes a coarse filter, a medium filter, and a fine filter. The coarse filter has a micron rating greater than the medium filter, the medium filter having a micron rating greater than the fine filter.

The fuel system of any preceding clause, wherein the coarse filter has a nominal micron rating from thirty microns to eighty microns.

The fuel system of any preceding clause, wherein the medium filter has a nominal micron rating from fifteen microns to sixty microns.

The fuel system of any preceding clause, wherein the fine filter has a nominal micron rating from a half micron to forty microns.

A fuel system includes a fuel metering unit, a first heat exchanger, a first set of fuel nozzles, a first coke filtration system, a second heat exchanger, a second set of fuel nozzles, and a second coke filtration system. The fuel metering is configured to meter a flow of a hydrocarbon fuel. The first heat exchanger is fluidly connected to the fuel metering unit downstream of the fuel metering unit to receive the flow of the hydrocarbon fuel. The first heat exchanger is configured to heat the hydrocarbon fuel. The first set of fuel nozzles is fluidly connected to the first heat exchanger downstream of the first heat exchanger to receive the hydrocarbon fuel heated by the first heat exchanger. The first coke filtration system includes at least one filter. The first coke filtration system is located upstream of the first set of fuel nozzles and directly downstream of the first heat exchanger. The second heat exchanger is fluidly connected to the fuel metering unit downstream of the fuel metering unit to receive the flow of the hydrocarbon fuel. The second heat exchanger is configured to heat the hydrocarbon fuel. The second set of fuel nozzles fluidly is connected to the second heat exchanger downstream of the second heat exchanger to receive the hydrocarbon fuel heated by the second heat exchanger. The second coke filtration system includes at least one filter. The second coke filtration system is located upstream of the second set of fuel nozzles and directly downstream of the second heat exchanger.

The fuel system of any preceding clause, wherein each of the first coke filtration system and the second coke filtration system include a plurality of filters in series.

The fuel system of any preceding clause, wherein the plurality of filters of each of the first coke filtration system and the second coke filtration system includes a coarse filter, a medium filter, and a fine filter. The coarse filter having a micron rating greater than the medium filter, the medium filter having a micron rating greater than the fine filter.

A gas turbine engine includes a lubrication system containing oil flowing therethrough and the fuel system of any preceding clause, wherein the fuel system further comprises a preheater, a main filter, and a fuel pump. The preheater is fluidly connected to the fuel metering unit upstream of the fuel metering unit. The preheater is configured to heat the hydrocarbon fuel. The preheater is a heat exchanger fluidly connected to the lubrication system to extract heat from the oil of the lubrication system and to heat the hydrocarbon fuel. The main filter is fluidly connected to the preheater downstream of the preheater to receive the hydrocarbon fuel heated by the preheater. The main filter is located upstream of the fuel metering unit. The fuel pump is fluidly connected to the fuel metering unit upstream of the fuel metering unit and downstream of the main filter.

A gas turbine engine including the fuel system of the preceding clause, a compressor section, a combustor, and a turbine section. The compressor section is configured to compress air. The combustor includes a combustion chamber. The plurality of fuel nozzles is configured to inject the hydrocarbon fuel into the combustion chamber. The combustor is configured to mix air with the hydrocarbon fuel to form a fuel and air mixture and to combust the fuel and air mixture forming combustion products. The turbine section is configured to receive the combustion products. The turbine section has at least one turbine configured to be driven by the combustion products. The heat exchanger is thermally connected to one of the compressor section, the combustor, or the turbine section to receive heat and heat the hydrocarbon fuel.

Although the foregoing description is directed to the preferred embodiments, other variations and modifications will be apparent to those skilled in the art and may be made without departing from the spirit or scope of the disclosure. Moreover, features described in connection with one embodiment may be used in conjunction with other embodiments, even if not explicitly stated above.