Thermal management system for engine

Abstract

The thermal management system includes a thermal circuit having a thermal transfer bus through which a thermal fluid flows. The heat transfer bus includes first and second bus segments. The first and second thermal loads are located on the first and second bus segments, respectively, and have different first and second inlet temperature requirements. The thermal management system includes a plurality of heat exchangers in thermal communication with first and second thermal loads. The heat exchangers include a first heat exchanger and one or more second heat exchangers. A first heat exchanger is located on one of the first or second bus segments for discharging heat into the engine fuel. The hot fluid is diverted between each of the first and second bus segments such that only a portion of the hot fluid flows through the first heat exchanger to accommodate different first and second inlet temperature requirements.

Description

Technical Field

[0001] The present disclosure relates generally to gas turbine engines and, more particularly, to thermal management systems for gas turbine engines. Background Art

[0002] A gas turbine engine typically includes an inlet, a fan, one or more compressors, a combustor, and at least one turbine. The compressor compresses air, which is directed to the combustor where it is mixed with fuel. The mixture is then ignited to produce hot combustion gases. The combustion gases are directed to the turbine, which extracts energy from the combustion gases to drive the compressor and to produce useful work to propel an aircraft in flight or to power a load (e.g., a generator).

[0003] During operation of a gas turbine engine, various systems may generate relatively large amounts of heat. A thermal management system for a gas turbine engine may collect heat from one or more of these systems to maintain the temperature of these systems within an acceptable operating range. The thermal management system may remove or reject this heat via one or more heat exchangers. In at least some embodiments, at least one heat exchanger may be integrated into one or more components exposed to the bypass airflow passage, such as one or more struts extending between the turbine and the outer nacelle. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] A full and enabling disclosure of the present invention, including the best mode thereof, is set forth in the specification with reference to the accompanying drawings, to which one of ordinary skill in the art will appreciate:

[0005] Figure 1 is a cross-sectional view of a gas turbine engine according to an exemplary aspect of the present disclosure.

[0006] Figure 2 is a simplified schematic diagram of a thermal management system according to an exemplary embodiment of the present disclosure.

[0007] Figure 3 is a simplified schematic diagram of a thermal management system according to another exemplary embodiment of the present disclosure.

[0008] Figure 4 is a simplified schematic diagram of a thermal management system according to another exemplary embodiment of the present disclosure.

[0009] Figure 5 is a simplified schematic diagram of a thermal management system according to another exemplary embodiment of the present disclosure.

[0010] Figure 6 is a simplified schematic diagram of a thermal management system according to another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0011] Reference will now be made in detail to the present embodiments of the present disclosure, one or more examples of which are shown in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. The same or similar designations in the drawings and description have been used to refer to the same or similar parts of the present disclosure.

[0012] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, unless expressly stated otherwise, all embodiments described herein should be considered exemplary.

[0013] The terms "upstream" and "downstream" refer to relative directions relative to the flow of a fluid in a fluid path. For example, "upstream" refers to the direction from which the fluid is flowing, while "downstream" refers to the direction to which the fluid is flowing.

[0014] As used herein, the terms “first”, “second”, etc. may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of each component.

[0015] The terms "coupled" and the like refer to both direct coupling, securing, or attachment as well as indirect coupling, securing, or attachment through one or more intermediate components or features, unless otherwise specified herein.

[0016] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0017] For example, in the context of “at least one of A, B, and C,” the term “at least one” means only A, only B, only C, or any combination of A, B, and C.

[0018] Here and throughout the specification and claims, range limitations are combinable and interchangeable, and these ranges are identified and include all subranges contained therein unless context or language dictates otherwise. For example, all ranges disclosed herein include the endpoints, and the endpoints are independently combinable with each other.

[0019] The term "turbomachine" or "turbomachinery" refers to a machine that transfers power between a fluid and a rotating shaft, such as a compressor or pump that transfers work from a shaft to a fluid, or a turbine that extracts power from a fluid to turn a shaft.

[0020] The term "gas turbine engine" refers to an engine that uses a turbine as all or part of its power source. Examples of gas turbine engines include turbofan engines, turboprop engines, turbojets, turboshaft engines, etc., as well as hybrid versions of one or more of these engines.

[0021] The term "combustion section" refers to any heat addition system for a turbomachine. For example, the term combustion section may refer to a section that includes one or more of a deflagration combustion assembly, a rotating detonation combustion assembly, a pulse detonation combustion assembly, or other suitable heat addition assemblies. In certain exemplary embodiments, the combustion section may include an annular combustor, a can combustor, an annular can combustor, a trapped vortex combustor (TVC), or other suitable combustion systems, or combinations thereof.

[0022] Conventional thermal management systems cool the oil in the system to the minimum required temperature and do not maximize the heat rejection of the oil to the fuel flow. Therefore, conventional thermal management systems typically include oversized air-cooled oil heat exchangers, which increase fan duct pressure losses. Therefore, the present disclosure is directed to an improved fuel-oil thermal management system for a gas turbine engine. In an embodiment, for example, the fuel-oil thermal management system includes a thermal circuit having a heat transfer bus through which a hot fluid flows. The heat transfer bus includes a plurality of bus segments, such as at least a first bus segment and a second bus segment. Therefore, the fuel-oil thermal management system improves cooling by branching the system between the plurality of bus segments to different air-cooled oil heat exchangers and fuel-cooled oil heat exchangers to effectively meet the different oil temperature inlet requirements of various engine components (e.g., engine bearings and reduction gearboxes). In an embodiment, the fuel-oil thermal management system is also configured to actively adjust the oil flow to maximize the use of the fuel radiator (also referred to herein as a fuel-cooled heat exchanger) throughout the mission and reduce the total airflow required for the air-cooled oil heat exchanger.

[0023] Referring now to the drawings, wherein like numerals refer to like elements throughout, Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary embodiment of the present disclosure. More specifically, Figure 1 In the embodiment of the present invention, the gas turbine engine is a high bypass turbofan jet engine, referred to herein as "turbofan engine 10". Figure 1 As shown, the turbofan engine 10 defines an axial direction A (extending parallel to a longitudinal centerline 12 provided for reference) and a radial direction R. Generally, the turbofan engine 10 includes a fan section 14 and a turbine 16 located downstream of the fan section 14 .

[0024] In addition, the illustrated turbomachine 16 generally includes a generally tubular outer casing 18 defining an annular inlet 20. The outer casing 18 encloses, in series flow relationship: a compressor section including a supercharger or low pressure (LP) compressor 22 and a high pressure (HP) compressor 24; a combustion section 26; a turbine section including a high pressure (HP) turbine 28 and a low pressure (LP) turbine 30; and an ejection exhaust nozzle section 32. A high pressure (HP) shaft 34 drivingly connects the HP turbine 28 to the HP compressor 24. A low pressure (LP) shaft 36 drivingly connects the LP turbine 30 to the LP compressor 22.

[0025] For the illustrated embodiment, the fan section 14 includes a variable pitch fan 38 having a plurality of fan blades 40 coupled to a disk 42 in a spaced apart manner. As shown, the fan blades 40 extend outwardly from the disk 42 generally in a radial direction R. Each fan blade 40 is rotatable about a pitch axis P relative to the disk 42 by virtue of the fan blades 40 being operably coupled to an appropriate actuation member 44 that is configured to collectively and uniformly change the pitch of the fan blades 40. The fan blades 40, disk 42, and actuation members 44 are rotatable together about the longitudinal centerline 12 via the LP shaft 36 across a power gearbox 46. The power gearbox 46 includes a plurality of gears for reducing the rotational speed of the LP shaft 36 to a more efficient fan speed.

[0026] Still refer to Figure 1 , disk 42 is covered by a rotor spinner 48 having an aerodynamic profile to facilitate airflow through the plurality of fan blades 40. In addition, fan section 14 includes an annular fan casing or outer nacelle 50 that circumferentially surrounds at least a portion of fan 38 or turbine 16. Outer nacelle 50 is supported relative to turbine 16 by a plurality of circumferentially spaced outlet guide vanes 52. Furthermore, outer nacelle 50 extends over an outer portion of turbine 16 to define a bypass airflow passage 56 therebetween.

[0027] During operation of the turbofan engine 10, a volume of air 58 enters the turbofan engine 10 through the outer nacelle 50 or the associated inlet 60 of the fan section 14. As the volume of air 58 passes through the fan blades 40, a first portion of the air 58, as indicated by arrow 62, is directed or directed into the bypass airflow passage 56, while a second portion of the air 58, as indicated by arrow 64, is directed or directed into the LP compressor 22. The ratio between the first portion 62 of air and the second portion 64 of air is generally referred to as a bypass ratio. The pressure of the second portion 64 of air is then increased as it is directed through the high pressure (HP) compressor 24 and into the combustion section 26, where it is mixed with fuel and combusted to provide combustion gases 66. The combustion gases 66 are then directed through the HP turbine 28 and the LP turbine 30, where a portion of the heat or kinetic energy is extracted from the combustion gases 66.

[0028] The combustion gases 66 are then directed through the jet exhaust nozzle section 32 of the turbine 16 to provide propulsive thrust. At the same time, the pressure of the first portion of air 62 is significantly increased as it is directed through the bypass airflow passage 56 before being discharged from the fan nozzle exhaust section 76 of the turbofan engine 10, also providing propulsive thrust.

[0029] In addition, as schematically shown, the turbofan engine 10 also includes various accessory systems to assist the operation of the turbofan engine 10 or an aircraft including the turbofan engine 10. For example, the turbofan engine 10 includes a main lubrication system 78, which is configured to provide lubricant to various bearings and gear meshes in the compressor section (including the LP compressor 22 and the HP compressor 24), the turbine section (including the HP turbine 28 and the LP turbine 30), the HP shaft 34, the LP shaft 36, and the power gearbox 46. The lubricant provided by the main lubrication system 78 can increase the service life of these components and can remove a certain amount of heat from these components. In addition, the turbofan engine 10 can include a cooled cooling air (CCA) system 80 for providing air from one or both of the HP compressor 24 or the LP compressor 22 to one or both of the HP turbine 28 or the LP turbine 30. In addition, the turbofan engine 10 can include an active thermal clearance control (ACC) system 82 for cooling the casing of the turbine section to maintain the clearance between various turbine rotor blades 40 and the turbine casing within a desired range under various engine operating conditions. In addition, the turbofan engine 10 includes a generator lubrication system 84 for providing lubrication for the generator and cooling / dissipating heat for the generator. The generator can provide electrical power to, for example, a starter motor of the turbofan engine 10 or various other electrical components of the turbofan engine 10 or an aircraft including the turbofan engine 10.

[0030] As shown in the schematic diagram, the turbofan engine 10 drives or enables various other accessory systems, such as for an aircraft that includes the turbofan engine 10. For example, the turbofan engine 10 can provide compressed air from the compressor section to an environmental control system (ECS) 86. The ECS 86 can provide an air supply to the cabin of the aircraft for pressurization and thermal control. In addition, air from the turbofan engine 10 can be provided to an electronic cooling system 88 to maintain the temperature of certain electronic components of the turbofan engine 10 or the aircraft within a desired range.

[0031] However, it should be recognized that Figure 1 The turbofan engine 10 shown in is only an example, and in other exemplary embodiments, aspects of the present disclosure may be applied additionally or alternatively to any other suitable gas turbine engine. For example, in other exemplary embodiments, the turbofan engine 10 may be any other suitable aviation gas turbine engine, such as a turbojet engine, a turboshaft engine, a turboprop engine, etc. In addition, in other exemplary embodiments, the turbofan engine 10 may include or be operably connected to any other suitable accessory system. In addition, or alternatively, the turbofan engine 10 may not include or be operably connected to one or more of the above-mentioned accessory systems.

[0032] Reference now Figure 1-3 The turbofan engine 10 also includes a thermal management system 100 for transferring heat from some or all of such accessory systems to more efficiently remove such heat or utilize such heat. More specifically, Figure 2 and 3 A schematic diagram of an embodiment of a thermal management system 100 according to the present disclosure is shown for at least partial incorporation into the turbofan engine 10 described herein.

[0033] like Figure 2 and 3 As shown, the thermal management system 100 generally includes a thermal circuit 102 having a heat transfer bus 103, a thermal fluid tank 105 for storing a thermal fluid 104, and a pump 106 for circulating the thermal fluid 104 to and from the thermal fluid tank 105 through the thermal circuit 102. Therefore, in an embodiment, the thermal management system 100 is a fuel-oil thermal management system, and the thermal fluid 104 is an oil-based lubricant. In addition, in an embodiment, the heat transfer bus 103 can be formed by one or more suitable fluid conduits.

[0034] The pump 106 is in fluid communication with the thermal fluid 104 in the heat transfer bus 103 for generating a flow of the thermal fluid 104 in or through the heat transfer bus 103. Figure 2 and 3As shown, pump 106 can generate a flow of thermal fluid 104 through heat transfer bus 103 in a generally clockwise direction. Pump 106 can be a rotary pump including an impeller, or can be any other suitable fluid pump. In addition, pump 106 can be driven by an electric motor, or can be mechanically connected to and driven by HP shaft 34 or LP shaft 36 of turbofan engine 10. In other embodiments, pump 106 can be driven by an auxiliary turbine, which in turn can be driven by bleed air from a compressor section of a gas turbine engine, in which thermal management system 100 is incorporated.

[0035] Still refer to Figure 2 and Figure 3 , the heat transfer bus 103 also includes a plurality of bus segments. Specifically, as shown in the figure, the plurality of bus segments may include at least a first bus segment 110 and a second bus segment 112. In addition, as shown in the figure, Figure 2 and Figure 3 The first bus segment 110 and the second bus segment 112 of the illustrated embodiment are bus branches that provide flow splitting of the thermal fluid 104. In certain embodiments, the flow is physically split between the bus branches, for example, based on the respective flow resistance within each bus branch. Specifically, the first and second bus branches each define a tube that can be sized and / or can include restrictions (e.g., orifice plates, etc.) to control resistance and meter flow between the different bus branches to provide the desired flow splitting.

[0036] In addition, as shown, the thermal circuit 102 includes a first heat load 114 on the first bus segment 110, which has a first inlet temperature requirement. In addition, as shown, the thermal circuit 102 includes a second heat load 116 on the second bus segment 112, which has a second inlet temperature requirement. Therefore, in an embodiment, the first and second inlet temperature requirements are different. For example, in an embodiment, the first inlet temperature requirement of the first heat load 114 is higher than the second inlet temperature requirement of the second heat load 116. In a specific embodiment, for example, the first inlet temperature requirement is at least 5 degrees Fahrenheit (°F) higher than the second inlet temperature, such as at least 10°F, such as at least 20°F. In addition, in an embodiment, the second heat load 116 is at least 60% of the first heat load 114. In addition, in an embodiment, the second heat load 116 is at least 40% of the total oil-based lubricant heat load.

[0037] Thus, in certain embodiments, the first heat load 114 may be a reduction gearbox, a variable frequency generator, one or more reservoirs, an accessory gearbox, or an oil-to-oil heat exchanger. Additionally, in embodiments, the second heat load 116 may be a different one of a reduction gearbox, a variable frequency generator, one or more reservoirs, an accessory gearbox, or an oil-to-oil heat exchanger. In certain embodiments, for example, the reservoir described herein may be part of a main lubrication system 78 for providing lubrication to components of the turbofan engine 10. For example, in embodiments, the component may be a compressor section or a turbine section of the turbofan engine 10. Thus, in an exemplary embodiment, the first heat load 114 may be a reservoir of the main lubrication system 78, and the second heat load 116 may be a reduction gearbox.

[0038] Still refer to Figure 2 and 3 , the thermal management system 100 includes one or more heat exchangers 108 that are thermally connected to the thermal fluid 104 in the heat transfer bus 103 and the first and second heat loads 114, 116. Specifically, the thermal circuit 102 shown includes a plurality of heat exchangers 108. More specifically, for the illustrated embodiment, there are three heat exchangers 108. However, in other exemplary embodiments, any other suitable number of heat exchangers 108 may be included, and one or more heat exchangers 108 may be arranged in a series flow or parallel flow sequence along the heat transfer bus 103. For example, in other embodiments, there may be at least four heat exchangers 108, at least five heat exchangers 108, or at least six heat exchangers 108 that are thermally connected to the thermal fluid 104 in the heat transfer bus 103.

[0039] The plurality of heat exchangers 108 are configured to transfer heat from one or more accessory systems of the turbofan engine 10 (or in operative communication with the turbofan engine 10) to the thermal fluid 104 in the heat transfer bus 103. For example, in certain embodiments, the plurality of heat exchangers 108 may include one or more of: an air-cooled oil cooler for transferring oil heat to an air flow, a fuel-cooled oil cooler for transferring oil heat to a fuel flow, an oil-cooled oil cooler for transferring oil heat from one oil flow to a lower temperature oil flow, or the like, or a combination thereof.

[0040] More specifically, if Figure 2 and Figure 3As shown, the plurality of heat exchangers 108 may include a first heat exchanger 118 and one or more second heat exchangers 120. For example, in an embodiment, the first heat exchanger 118 is a fuel-cooled heat exchanger, such as a fuel-cooled oil cooler, and the second heat exchanger 120 is an air-cooled heat exchanger, such as an air-cooled oil cooler. In a particular embodiment, as shown, the second heat exchanger 120 includes a first air-cooled heat exchanger 122 and a second air-cooled heat exchanger 124. Thus, in an embodiment, the hot fluid 104 flows to each of the first and second bus segments 110, 112 such that only a portion of the hot fluid 104 flows through the first heat exchanger 118.

[0041] In addition, if Figure 2 and 3 As shown, the first heat exchanger 118 is located upstream of the second heat exchanger 120, so that heat is discharged from the first heat exchanger 118 to the engine fuel of the turbofan engine 10 before being cooled by the second heat exchanger 120. More specifically, in an embodiment, as shown in FIG. Figure 2 As shown, the first heat exchanger 118 is located on the first bus section 110 for discharging heat into the engine fuel of the turbofan engine 10. In such an embodiment, as shown, the first bus section 110 can correspond to the "hot" branch because the components on the hot branch (e.g., the storage tank) require or can use higher temperature lubricating oil and can be designated as higher temperature components. In addition, as shown, the second bus section 112 can correspond to the "cold" branch because the lower temperature components (e.g., the reduction gearbox) are located on the second bus section 112. Therefore, the first heat exchanger 118 located on the hot branch can maximize the heat of the fuel, thereby reducing the size of the first air-cooled heat exchanger 122. If the hot branch heat load (e.g., the first heat load 114) is greater than the cold branch heat load (e.g., the second heat load 116), such an embodiment may be beneficial.

[0042] In another embodiment, Figure 3 As shown, the first heat exchanger 118 is located on the second bus section 112 for rejecting heat to the engine fuel of the turbofan engine 10. In such an embodiment, the first heat exchanger 118 located on the cold branch minimizes the size of the second air-cooled heat exchanger 124. Such an embodiment may be beneficial if the cold branch heat load (e.g., the second heat load 116) is greater than the hot branch heat load (e.g., the first heat load 114).

[0043] Thus, the first heat exchanger 118 is configured to transfer heat from the hot fluid 104 in the heat transfer bus 103 to, for example, the atmosphere, fuel, fan flow, etc. For example, in certain embodiments, the first heat exchanger 118 may include at least one of a ram heat exchanger, a fuel heat exchanger, a fan flow heat exchanger, a bleed air heat exchanger, an engine intercooler, or a cold air output of an air circulation system. As used herein, a ram heat exchanger generally refers to a heat exchanger that uses forward motion to increase pressure to drive flow. Thus, in an embodiment, a ram heat exchanger may be a heat exchanger located in a duct, wherein the forward motion of the vehicle (e.g., flight speed) drives air to flow through the duct and the heat exchanger. The ram heat exchanger may be configured as an "air to hot fluid" heat exchanger, integrated into one or both of the turbofan engine 10 or an aircraft including the turbofan engine 10. During operation, the ram heat exchanger may remove heat from any of the hot fluids 104 therein by flowing a certain amount of ram air through the ram heat exchanger. Additionally, the first heat exchanger 118 may be a “fluid to hot fluid” heat exchanger, where heat from the hot fluid 104 is transferred to a liquid fuel stream of the turbofan engine 10. Additionally, a fan flow heat exchanger is typically an “air to hot fluid” heat exchanger, which flows, for example, bypass air through the hot fluid 104 to remove heat from the hot fluid 104. Additionally, a bleed air heat exchanger is typically an “air to hot fluid” heat exchanger, which flows, for example, bleed air from the LP compressor 22 through the hot fluid 104 to remove heat from the hot fluid 104. In another embodiment, the first heat exchanger 118 may be a “fan flow air” heat exchanger, which generally refers to a heat exchanger located in a fan flow or a heat exchanger that is cooled by extracting air from a fan flow and directing the air to a heat exchanger.

[0044] Reference now Figure 4 , where the same numbers represent Figure 2 and 3 , a schematic diagram of an embodiment of a thermal management system 100 according to the present disclosure is shown, for at least partial incorporation into the turbofan engine 10 described herein. Specifically, as shown, the first heat exchanger 118 is located downstream of the first heat load 114 (e.g., a high temperature load) on the first bus section 110 to maximize the heat rejection of the oil to the fuel. Therefore, in such an embodiment, Figure 4 The location of the first heat exchanger 118 in the middle reduces the return temperature to the hot fluid tank 105 and reduces the heat load of the second heat exchanger 120.

[0045] In addition, as shown, the thermal management system 100 includes at least one sensor 126 that is in thermal communication with the engine fuel flowing through the first heat exchanger 118. For example, as shown, the engine fuel 132 (e.g., from the boost pump) enters the first heat exchanger 118 at a first temperature and leaves the first heat exchanger 118 at a second temperature (e.g., to the main fuel pump, the fuel management unit (FMU), the combustion section 26, etc.). In such an embodiment, the sensor 126 is configured to measure the temperature of the engine fuel 132. In addition, as shown, the plurality of bus segments of the thermal management system 100 may also include a third bus segment 130 that bypasses the first heat exchanger 118 and has a flow control valve 128 for regulating the flow rate of the thermal fluid 104 entering the first heat exchanger 118 based on the temperature of the engine fuel 132. It should also be understood that any suitable number of bus segments may be included in the thermal circuit 102 to support any number of thermal loads.

[0046] Reference now Figure 5 and 6 , shows a schematic diagram of an embodiment of a thermal management system 100 according to the present disclosure, for at least partial incorporation into the turbofan engine 10 described herein. Specifically, as shown and as previously described, the thermal management system 100 generally includes a thermal loop 102 having a heat transfer bus 103, a thermal fluid tank 105 for storing a thermal fluid 104, and a pump 106 for circulating the thermal fluid 104 to and from the thermal fluid tank 105 through the thermal loop 102. Therefore, in an embodiment, the thermal management system 100 is a fuel-oil thermal management system, and the thermal fluid 104 is an oil-based lubricant. Furthermore, in an embodiment, the heat transfer bus 103 can be formed by one or more suitable fluid conduits.

[0047] Still refer to Figure 5 and Figure 6 , the heat transfer bus 103 also includes a plurality of segments, such as a first bus segment 110, a second bus segment 112, and a third bus segment 130. In addition, as shown, the first heat load 114 is on the first bus segment 110, and the second heat load 116 is on the second bus segment 112. However, Figure 2 and Figure 3 Compared with the embodiment, Figure 5 and Figure 6 The first and second bus segments 110 , 112 are arranged in a series flow arrangement.

[0048] In addition, if Figure 5 and Figure 6As shown, the thermal management system 100 includes a plurality of heat exchangers 108 in thermal communication with first and second heat loads 114, 116. More specifically, as shown, the plurality of heat exchangers 108 includes a first heat exchanger 118, such as a fuel-cooled heat exchanger, and a second heat exchanger 120, such as a first air-cooled heat exchanger 122 and a second air-cooled heat exchanger 124.

[0049] In addition, if Figure 5 and 6 As shown, the first heat exchanger 118 is positioned between the first and second bus sections 110, 112 for rejecting heat to the engine fuel of the turbofan engine 10. In addition, as shown, the third bus section 130 bypasses the first heat exchanger 118. Figure 5 and 6 As shown, and with Figure 4 Similar to the embodiment of the present invention, the thermal management system 100 includes a flow control valve 128 in the third bus section 130 for adjusting the flow rate of the thermal fluid 104 entering the first heat exchanger 118. In an embodiment, as Figure 5 As shown, the third bus segment 130 is positioned downstream of the second heat load 116 and upstream of the first air-cooled heat exchanger 122. Figure 5 Embodiments of the invention require only a single sensor to be placed on the fuel stream to control the burner delivery temperature. Alternatively, Figure 6 As shown, the third bus section 130 is positioned downstream of the second air-cooled heat exchanger 124 and upstream of the first air-cooled heat exchanger 122. Figure 6 Embodiments are configured to act as a single actively controlled bypass valve to regulate low temperature load flow.

[0050] Therefore, in an embodiment, as shown, the thermal management system 100 may also include at least one sensor 126 that is in thermal communication with the engine fuel flowing through the first heat exchanger 118. Therefore, as described above, the sensor 126 is configured to measure the temperature of the engine fuel. In such an embodiment, as an example, the flow control valve 128 is configured to adjust the flow rate of the hot fluid 104 entering the first heat exchanger 118 based on the temperature of the engine fuel measured by the sensor 126.

[0051] Therefore, in such an embodiment, Figure 5 and Figure 6Embodiments are identified to increase the temperature of the hot fluid 104 (e.g., oil temperature) entering the first heat exchanger 118 to obtain a larger driving temperature difference, thereby maximizing the heat rejection rate of the engine fuel 132. In addition, in embodiments, an oil flow control valve that bypasses a portion of the first heat exchanger 118 maximizes oil circuit heat rejection without exceeding the fuel temperature limit. In addition, in embodiments, regulating the oil flow instead of the fuel flow eliminates additional hysteresis in the fuel flow controller.

[0052] Further aspects are provided by the subject matter of the following clauses:

[0053] A thermal management system for a gas turbine engine, the thermal management system comprising: a thermal circuit, the thermal circuit comprising: a heat transfer bus, through which a thermal fluid flows, the heat transfer bus comprising a first bus segment and a second bus segment; a first heat load on the first bus segment and having a first inlet temperature requirement; a second heat load on the second bus segment and having a second inlet temperature requirement, the first inlet temperature requirement and the second inlet temperature requirement being different; and a plurality of heat exchangers, the plurality of heat exchangers being thermally connected to the first heat load and the second heat load, the plurality of heat exchangers comprising a first heat exchanger and one or more second heat exchangers, the first heat exchanger being located on one of the first bus segment or the second bus segment for rejecting heat to an engine fuel of the engine, wherein the thermal fluid is divided between each of the first bus segment and the second bus segment so that only a portion of the thermal fluid flows through the first heat exchanger to accommodate the different first inlet temperature requirements and the second inlet temperature requirements.

[0054] A thermal management system as described in any preceding clause, wherein the first heat exchanger is located upstream of the one or more second heat exchangers so that heat is rejected by the first heat exchanger to the engine fuel of the engine before being cooled by the one or more second heat exchangers.

[0055] A thermal management system as in any preceding clause, wherein the first inlet temperature requirement of the first heat load is higher than the second inlet temperature requirement of the second heat load.

[0056] A thermal management system according to any preceding clause, wherein the first heat exchanger is located downstream of the first heat load on the first bus segment, the thermal management system further comprising at least one sensor, the at least one sensor being thermally connected to the engine fuel flowing through the first heat exchanger, the at least one sensor being configured to measure a temperature of the engine fuel.

[0057] A thermal management system as described in any preceding clause, further comprising a flow control valve for regulating a flow rate of the thermal fluid entering the first heat exchanger based on a temperature of the engine fuel.

[0058] A thermal management system as in any preceding clause, wherein the first inlet temperature requirement is at least five (5) degrees Fahrenheit (°F) higher than the second inlet temperature requirement.

[0059] The thermal management system of any preceding clause, wherein the first heat exchanger is a fuel-cooled heat exchanger and the one or more second heat exchangers are air-cooled heat exchangers.

[0060] A thermal management system as in any preceding clause, wherein the first thermal load is one of a reduction gearbox, a variable frequency generator, one or more reservoirs, an accessory gearbox, or an oil-to-oil heat exchanger.

[0061] A thermal management system as in any preceding clause, wherein the second heat load is one of the reduction gearbox, the variable frequency generator, the one or more reservoirs, the accessory gearbox, or the oil-to-oil heat exchanger that is different from the first heat load.

[0062] A thermal management system as described in any preceding clause, wherein the one or more reservoirs are part of a primary lubrication system for providing lubrication to a component of the engine, wherein the component is at least one compressor section or turbine section of the engine.

[0063] A thermal management system as recited in any preceding clause, wherein the first thermal load is the one or more reservoirs of the primary lubrication system and the second thermal load is the reduction gearbox.

[0064] A thermal management system as described in any preceding clause, further comprising a thermal fluid tank and a pump for circulating the thermal fluid to and from the thermal fluid tank through the thermal loop.

[0065] A thermal management system as described in any preceding clause, wherein the thermal management system is a fuel-oil thermal management system and the thermal fluid is an oil-based lubricant.

[0066] A thermal management system as in any preceding clause, wherein at least one of the following parameters is true: the second heat load is at least 60% of the first heat load or the second heat load is at least 40% of the total oil-based lubricant heat load.

[0067] A thermal management system for a gas turbine engine, the thermal management system comprising: a thermal circuit, the thermal circuit comprising: a heat transfer bus through which a thermal fluid flows, the heat transfer bus comprising a first bus segment, a second bus segment, and a third bus segment, the first bus segment and the second bus segment being arranged in a series flow arrangement; a first heat load on the first bus segment and having a first inlet temperature requirement; a second heat load on the second bus segment and having a second inlet temperature requirement, the first inlet temperature requirement and the second inlet temperature requirement being different; a plurality of heat exchangers, the plurality of heat exchangers being in thermal communication with the first heat load and the second heat load, the plurality of heat exchangers comprising a first heat exchanger and one or more second heat exchangers, the first heat exchanger being positioned between the first bus segment and the second bus segment for rejecting heat to an engine fuel of the engine, the third bus segment bypassing the first heat exchanger; and a flow control valve, the flow control valve being in the third bus segment for regulating a flow rate of the thermal fluid entering the first heat exchanger to accommodate the different first inlet temperature requirements and the second inlet temperature requirements.

[0068] A thermal management system as in any preceding clause, wherein the first inlet temperature requirement of the first heat load is higher than the second inlet temperature requirement of the second heat load, and wherein the first heat exchanger comprises a fuel-cooled heat exchanger and the one or more second heat exchangers comprise first and second air-cooled heat exchangers.

[0069] A thermal management system as recited in any preceding clause, wherein the flow control valve is positioned downstream of the second heat load and upstream of the first air-cooled heat exchanger.

[0070] A thermal management system as recited in any preceding clause, wherein the flow control valve is positioned downstream of the second air-cooled heat exchanger and upstream of the first air-cooled heat exchanger.

[0071] The thermal management system of any preceding clause, further comprising at least one sensor thermally connected to the engine fuel flowing through the first heat exchanger, the at least one sensor configured to measure a temperature of the engine fuel, and wherein the flow control valve is configured to regulate a flow rate of the thermal fluid entering the first heat exchanger based on the temperature of the engine fuel.

[0072] A thermal management system as in any preceding clause, wherein the first thermal load is one or more reservoirs of a primary lubrication system and the second thermal load is a reduction gearbox.

[0073] This written description uses examples to disclose the present disclosure, including the best mode, and also to enable those skilled in the art to practice the present disclosure, including making and using any device or system. The patentable scope of the present disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. These other examples are intended to fall 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.

Claims

1. A thermal management system for an engine, characterized in that: The thermal management system comprises: A thermal circuit, the thermal circuit comprising: a heat transfer bus through which a thermal fluid flows, the heat transfer bus comprising a first bus segment and a second bus segment, the first bus segment comprising a first heat load having a first inlet temperature requirement, the second bus segment comprising a second heat load having a second inlet temperature requirement, the first inlet temperature requirement and the second inlet temperature requirement being different; and a plurality of heat exchangers in thermal communication with the first heat load and the second heat load, the plurality of heat exchangers comprising a first heat exchanger and one or more second heat exchangers, the first heat exchanger being located on one of the first bus segment or the second bus segment for rejecting heat to an engine fuel of the engine, The thermal fluid is divided between each of the first bus section and the second bus section so that only a portion of the thermal fluid flows through the first heat exchanger to accommodate different first inlet temperature requirements and second inlet temperature requirements.

2. The thermal management system according to claim 1, characterized in that: Wherein the first heat exchanger is located upstream of the one or more second heat exchangers such that the heat is rejected by the first heat exchanger to the engine fuel of the engine before being cooled by the one or more second heat exchangers.

3. The thermal management system according to claim 1, characterized in that: The first inlet temperature requirement of the first heat load is higher than the second inlet temperature requirement of the second heat load.

4. The thermal management system according to claim 1, characterized in that: Wherein the first heat exchanger is located downstream of the first heat load on the first bus segment, the thermal management system further includes at least one sensor, the at least one sensor is thermally connected to the engine fuel flowing through the first heat exchanger, and the at least one sensor is configured to measure the temperature of the engine fuel.

5. The thermal management system according to claim 4, characterized in that: Further included is a flow control valve for regulating a flow rate of the thermal fluid entering the first heat exchanger based on the temperature of the engine fuel.

6. The thermal management system according to claim 1, characterized in that: Wherein the first inlet temperature requirement is at least five (5) degrees Fahrenheit (°F) higher than the second inlet temperature requirement.

7. The thermal management system according to claim 1, characterized in that: Wherein the first heat exchanger is a fuel-cooled heat exchanger and the one or more second heat exchangers are air-cooled heat exchangers.

8. The thermal management system according to claim 1, characterized in that: Wherein the first heat load is one of a reduction gearbox, a variable frequency generator, one or more storage tanks, an accessory gearbox or an oil-to-oil heat exchanger.

9. The thermal management system according to claim 8, characterized in that: The second heat load is one of the reduction gearbox, the variable frequency generator, the one or more reservoirs, the accessory gearbox or the oil-to-oil heat exchanger that is different from the first heat load.

10. The thermal management system according to claim 9, characterized in that: The one or more reservoirs are part of a main lubrication system for providing lubrication to a component of the engine, wherein the component is at least one compressor section or a turbine section of the engine.

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