Heat exchanger capacity for one or more heat exchangers associated with accessory gearbox of turbofan engine

Abstract

A turbofan engine is provided. The turbofan engine includes a low pressure spool; a fan mechanically coupled with the low voltage spool; a high-voltage wire shaft; the accessory gear box is mechanically connected with the high-voltage wire shaft; a hydraulic pump mechanically coupled with the accessory gearbox; and one or more heat exchangers connected to the accessory gearbox, the one or more heat exchangers having a heat exchange capacity defined by a power of half of a product determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a thermal conductivity coefficient, the thermal conductivity is related to an accessory gearbox thermal load, a hydraulic pump power of the hydraulic pump, a fan diameter of the fan, an engine length of the turbofan engine, and a total pressure ratio of the turbofan engine.

Description

Technical Field

[0001] The present disclosure is directed to a turbofan engine having one or more heat exchangers associated with an accessory gearbox. Background Art

[0002] A turbofan engine may include an accessory gearbox that is mechanically coupled to a spool of the turbofan engine. The accessory gearbox may drive various engine accessories, such as a fuel pump, a hydraulic pump, and one or more generators. The accessory gearbox may generate a significant amount of heat during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] A full and enabling disclosure of the present disclosure, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0004] Figure 1 A schematic cross-sectional view of a turbofan engine according to an example embodiment of the present disclosure is provided;

[0005] Figure 2 Provided Figure 1 A perspective view of a heat exchanger of a turbofan engine;

[0006] Figure 3 Provided Figure 2 A perspective view of an exchanger unit of a heat exchanger;

[0007] Figure 4 Provides along Figure 3 A cross-sectional view of the core of the exchanger unit taken along line 4-4;

[0008] Figure 5 A schematic diagram of a heat exchanger coupled to an accessory gearbox of a turbofan engine is provided;

[0009] Figure 6 Various relationships between heat exchanger characteristics and operational and architectural characteristics of a turbofan engine according to an example embodiment of the present disclosure are listed;

[0010] Figure 7 graphically illustrates heat exchanger capacity of one or more heat exchangers connected to an accessory gearbox of a turbofan engine as a function of rotational speed of a high voltage spool of the turbofan engine according to an example embodiment of the present disclosure;

[0011] Figure 8 A table is provided that lists values ​​for different example turbofan engines according to example embodiments of the present disclosure; and

[0012] Fig. 9A flow chart of a method of operating a turbofan engine having one or more heat exchangers connected to an accessory gearbox is provided according to an example embodiment of the present disclosure. DETAILED DESCRIPTION

[0013] Reference will now be made in detail to the present embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter references to refer to features in the drawings. Like or similar reference numbers in the drawings and the specification have been used to refer to like or similar parts of the present disclosure.

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

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

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

[0017] In a context such as “at least one of A, B, and C,” the term “at least one of” 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 combined and interchanged, and unless context or language indicates otherwise, such ranges are identified and include all sub-ranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0019] As used herein, a heat exchanger is considered to be "connected" to the accessory gearbox, wherein the heat exchanger is configured to handle at least a portion of the heat load of the accessory gearbox.

[0020] A turbofan engine may include an accessory gearbox that is mechanically coupled to a spool of the turbofan engine, such as a high-voltage spool. The accessory gearbox may act as a speed reducer between the high-voltage spool and one or more engine accessories that are mechanically coupled to the accessory gearbox. Example engine accessories include, but are not limited to, a fuel pump, a hydraulic pump, and one or more generators. During operation, the accessory gearbox generates a large amount of heat. Therefore, the turbofan engine may include one or more heat exchangers for handling the heat load generated by the accessory gearbox. Designing a gas turbine engine with one or more heat exchangers connected to the accessory gearbox may present certain challenges. For example, there are certain challenges in designing a gas turbine engine with one or more heat exchangers that are both compact and capable of effectively handling the heat load of the accessory gearbox.

[0021] The inventors of the present disclosure have developed an architecture for a turbofan engine having one or more heat exchangers connected to an accessory gearbox, wherein the one or more heat exchangers are both compact and capable of efficiently handling the heat load. In particular, in the context of including the following references Figure 1 During the design of several different types of gas turbine engines of the described turbofan engine, the inventors set out to design a turbofan engine having a given fan, length, total pressure ratio, characteristics of the accessory gearbox and engine accessories, and characteristics of one or more heat exchangers connected to the accessory gearbox; to examine the compactness and efficiency of the one or more heat exchangers given the fan, length, total pressure ratio, characteristics of the accessory gearbox and engine accessories, and characteristics of the one or more heat exchangers; to redesign the turbofan engine, the accessory gearbox, the engine accessories, and / or the one or more heat exchangers by changing the fan diameter, the speed ratio of the accessory gearbox, the power, length and total pressure ratio of the hydraulic pump, and the area and / or volume of the passages of the one or more heat exchangers; to re-examine the compactness and efficiency of the one or more heat exchangers given the fan, length, total pressure ratio, characteristics of the accessory gearbox and engine accessories, and characteristics of the one or more heat exchangers; and so on.

[0022] In the practice of studying / evaluating various fan architectures, speed ratios of accessory gearboxes, power ratings of hydraulic pumps, lengths, total pressure ratios, and heat exchanger characteristics that were considered feasible and best met mission requirements, an unexpected relationship was discovered between the compactness of one or more heat exchangers and the ease with which the heat load is distributed to the one or more heat exchangers connected to the accessory gearbox. This relationship is represented by the heat exchanger capacity. Given the architectural arrangement of a turbofan engine and an accessory gearbox, the heat exchanger capacity can be considered an indicator of the compactness and effectiveness of one or more heat exchangers connected to the accessory gearbox to handle the heat load of the accessory gearbox. The inventors have discovered that a turbofan engine having one or more heat exchangers having a heat exchanger capacity within the range specified herein makes the one or more heat exchangers ideally compact and effective in handling the heat load associated with the accessory gearbox.

[0023] Now referring to the accompanying drawings, Figure 1 A schematic cross-sectional view of a turbofan engine 100 is provided in accordance with an example embodiment of the present disclosure. Figure 1 In the illustrated embodiment, the turbofan engine 100 is an aviation high bypass turbofan engine that is configured to be mounted on an aircraft, such as in an underwing configuration. As shown, the turbofan engine 100 defines an axial direction A, a radial direction R, and a circumferential direction C. The axial direction A extends parallel to or coaxially with a longitudinal centerline 102 defined by the turbofan engine 100.

[0024] The turbofan engine 100 includes a fan section 104 and an engine core 106 disposed downstream of the fan section 104. The engine core 106 includes an engine cowling 108 that defines an annular core inlet 110. The engine cowling 108 surrounds a compressor section 112 in series flow relationship, the compressor section 112 including a first supercharger or LP compressor 114 and a second HP compressor 116; a combustion section 118; a turbine section 120 including a first HP turbine 122 and a second LP turbine 124; and an exhaust section 126. The compressor section 112, the combustion section 118, the turbine section 120, and the exhaust section 126 together define a core air flow path 132 through the engine core 106.

[0025] The HP shaft 128 drivingly connects the HP turbine 122 to the HP compressor 116. The LP shaft 130 drivingly connects the LP turbine 124 to the LP compressor 114. The HP shaft 128, the rotating components of the HP compressor 116 mechanically coupled to the HP shaft 128, and the rotating components of the HP turbine 122 mechanically coupled to the HP shaft 128 collectively form a high-pressure spool 131 or the HP spool. The LP shaft 130, the rotating components of the LP compressor 114 mechanically coupled to the LP shaft 130, and the rotating components of the LP turbine 124 mechanically coupled to the LP shaft 130 collectively form a low-pressure spool 133 or the LP spool.

[0026] The fan section 104 includes a fan assembly 138 having a fan 134 mechanically coupled to a fan rotor 140. The fan 134 has a plurality of fan blades 136 spaced circumferentially from each other. As shown, the fan blades 136 generally extend outwardly from the fan rotor 140 in a radial direction R. A power gearbox 142 mechanically couples the LP spool 133 and the fan rotor 140. The power gearbox 142 may also be referred to as a main gearbox. The power gearbox 142 includes a plurality of gears for reducing the rotational speed of the LP shaft 130 to provide a more efficient fan speed of the fan 134. In other example embodiments, the fan blades 136 of the fan 134 may be mechanically coupled to an appropriate actuating member configured to pitch the fan blades 136 around a corresponding pitch axis (e.g., in unison). In other example embodiments, the turbofan engine 100 may have a direct drive configuration in which the LP spool 133 directly drives the fan 134 without using a power gearbox.

[0027] Still reference Figure 1 , the hub of the fan rotor 140 and the fan blades 136 is covered by a rotatable spinner 144 having an aerodynamic profile to facilitate airflow through the plurality of fan blades 136. In addition, the fan section 104 includes an annular fan case or outer nacelle 146 that circumferentially surrounds the fan 134 and / or at least a portion of the engine core 106. The nacelle 146 is supported relative to the engine core 106 by a plurality of circumferentially spaced outlet guide vanes 148. A downstream section 150 of the nacelle 146 extends over an outer portion of the engine core 106 so as to define a bypass passage 152 therebetween.

[0028] Turbofan engine 100 also includes an accessory gearbox 145. For this embodiment, accessory gearbox 145 is mechanically coupled to HP spool 131, or more specifically, to HP shaft 128. However, in other embodiments, accessory gearbox 145 may be mechanically coupled to LP spool 133 or some other spool (e.g., an intermediate pressure spool in embodiments where the turbofan includes three (3) spools). Accessory gearbox 145 is mechanically coupled to various engine accessories, such as a fuel pump 147, a hydraulic pump 149, one or more generators 151 ( Figure 1 Only one is shown), one or more motors, etc. For example, the accessory gearbox 145 can be mechanically coupled to various engine accessories via one or more shafts. Typically, the accessory gearbox 145 is configured to drive the engine accessories mechanically coupled thereto. The accessory gearbox 145 includes a plurality of gears for reducing the rotational speed of the HP spool 131 to provide a more efficient rotational speed for the engine accessories. In this manner, it can be understood that the accessory gearbox 145 defines a speed ratio with various accessories, which speed ratio refers to the ratio of the rotational speed output to the corresponding accessory to the rotational speed of the input shaft. For example, the accessory gearbox 145 defines a speed ratio with the hydraulic pump 149 that is equal to the ratio of the rotational speed of the output of the accessory gearbox 145 driving the hydraulic pump 149 to the rotational speed of the input shaft of the accessory gearbox 45 (driven by the HP spool 131 in the illustrated embodiment). This speed ratio is referred to herein as the speed ratio n of the hydraulic pump 149. Speed Ratio .

[0029] During operation of the turbofan engine 100, a volume of air 154 enters the turbofan engine 100 through the nacelle 146 and / or the associated inlet 156 of the fan section 104. As the volume of air 154 passes through the fan blades 136, a first portion of air 158 is directed or directed into the bypass passage 152, and a second portion of air 160 is directed or directed into the core inlet 110. The pressure of the second portion of air 160 gradually increases as it flows downstream through the LP compressor 114 and the HP compressor 116. In particular, the LP compressor 114 includes sequential stages of LP compressor stator blades 182 and LP compressor blades 184 that progressively compress the second portion of air 160. The LP compressor blades 184 are mechanically coupled to the LP shaft 130. Similarly, the HP compressor 116 includes sequential stages of HP compressor stator blades 186 and HP compressor blades 188 that further progressively compress the second portion of air 160. The HP compressor blades 188 are mechanically coupled to the HP shaft 128. The compressed second portion of air 160 is then discharged from the compressor section 112 into the combustion section 118 .

[0030] The compressed second portion of air 160 discharged from the compressor section 112 is mixed with fuel and combusted within the combustor of the combustion section 118 to provide combustion gases 162. The combustion gases 162 are directed from the combustion section 118 along a hot gas path 174 of the core air flow path 132 through the HP turbine 122, wherein a portion of the thermal and / or kinetic energy from the combustion gases 162 is extracted via sequential stages of HP turbine stator vanes 164 and HP turbine blades 166. The HP turbine blades 166 are mechanically coupled to the HP shaft 128. Thus, as the HP turbine blades 166 extract energy from the combustion gases 162, the HP shaft 128 rotates, thereby supporting the operation of the HP compressor 116. The combustion gases 162 are directed through the LP turbine 124, wherein a second portion of the thermal and kinetic energy is extracted from the combustion gases 162 via sequential stages of LP turbine stator vanes 168 and LP turbine blades 170. The LP turbine blades 170 are coupled to the LP shaft 130. Thus, as LP turbine blades 170 extract energy from combustion gases 162 , LP shaft 130 rotates, thereby supporting operation of LP compressor 114 and, via power gearbox 142 , fan 134 .

[0031] The combustion gases 162 are then directed through the exhaust section 126 of the engine core 106 to provide propulsive thrust. At the same time, the pressure of the first portion of air 158 is significantly increased as it is directed through the bypass passage 152 before being discharged from the fan nozzle exhaust section 172 of the turbofan engine 100, which also provides propulsive thrust. The HP turbine 122, the LP turbine 124, and the exhaust section 126 at least partially define a hot gas path 174 for directing the combustion gases 162 through the engine core 106.

[0032] Still reference Figure 1 It should be understood that the turbofan engine 10 defines an engine length L. As used herein, the engine length L refers to the length between the forwardmost end of the rotatable spinner 144 and the rear flange 143 of the turbofan engine 100 along the axial direction A. The rear flange 143 refers to a circumferential flange near the rear end of the turbofan engine 100 for coupling the tail cone 141 to the rest of the turbofan engine 100.

[0033] Furthermore, it should be understood that the turbofan engine 100 defines an overall pressure ratio OPR. As used herein, the term overall pressure ratio OPR refers to the pressure of the airflow at the compressor section outlet (e.g., at a location immediately downstream of the most downstream stage of the compressor rotor blades of the HP compressor 116) and the pressure of the airflow provided to the turbine (e.g., at Figure 1 The ratio of the air flow pressures at the inlet 110 in the embodiments of FIG. 1 , each being the case when the high voltage spool is operated at 100% capacity or at maximum rotational speed.

[0034] like Figure 1 As further shown, the turbofan engine 100 includes a cooling system 190 for cooling various components, such as the accessory gearbox 145. The cooling system 190 includes one or more heat exchangers 192. For this embodiment, the one or more heat exchangers 192 include four (4) heat exchangers, including a first heat exchanger 192A, a second heat exchanger 192B, a third heat exchanger 192C, and a fourth heat exchanger 192D. Each of the heat exchangers 192 can be any suitable type of heat exchanger, such as, but not limited to, a fuel-oil heat exchanger, an air-oil heat exchanger, or an oil-oil heat exchanger. In this regard, the one or more heat exchangers 192 can include one or more of a fuel-oil heat exchanger, an air-oil heat exchanger, an oil-oil heat exchanger, some combination thereof, and the like.

[0035] The one or more heat exchangers 192 are configured to be connected to the heat exchanger 192, for example, via one or more fluid supply conduits 194 ( Figure 1 The one or more heat exchangers 192 receive one or more first fluids F1 from the accessory gearbox 1452 (only one is shown). The one or more first fluids F1 received from the accessory gearbox 145 may be, for example, oil, one or more other transmission fluids, one or more lubrication fluids, some combination thereof, or the like. The one or more heat exchangers 192 are also configured to receive one or more second fluids F2 from other sources of the turbofan engine 100 or the aircraft on which the turbofan engine 100 is installed. For example, the one or more second fluids F2 may include fuel received from a fuel tank, cooling oil received from a return tank, air exhausted from the bypass passage 152 and / or the core air flow path 132, or the like. The one or more second fluids F2 may be used by the one or more heat exchangers 192 to cool the one or more first fluids F1. The one or more first fluids F1 may be, for example, returned to the heat exchanger 192 via one or more fluid return conduits 195 ( Figure 1 Only one is shown) is recirculated back to the accessory gearbox 145.

[0036] It should be understood that Figure 1 The turbofan engine 100 shown in FIG. 1 is provided as an example only, and in other example embodiments, the turbofan engine 100 may have any other suitable configuration. Additionally or alternatively, aspects of the present disclosure may be used with other suitable aviation turbofan engines, such as turboshaft engines, turboprop engines, turbojet engines, etc.

[0037] Figure 2 Provided Figure 1 1 is a perspective view of one of the one or more heat exchangers of turbofan engine 100. In particular, first heat exchanger 192A is shown. Figure 1The second heat exchanger 192B, the third heat exchanger 192C, and the fourth heat exchanger 192D can be configured in the same or similar manner as the first heat exchanger 192A. For example, each of the heat exchangers 192B, 192C, 192D can include a plurality of exchanger units, each exchanger unit having a core defining a first channel and a second channel, as described below.

[0038] like Figure 2 As shown, the first heat exchanger 192A defines a vertical direction V, a lateral direction L, and a transverse direction T that are orthogonal to each other. The first heat exchanger 192A includes a plurality of exchanger units 210. The exchanger units 210 can be compactly arranged in any suitable configuration. For this embodiment, the first heat exchanger 192A includes twenty (20) exchanger units 210, including ten right exchanger units 211-220 stacked on each other along the vertical direction V and ten left exchanger units 221-230 stacked on each other along the vertical direction V. Although Figure 2 The first heat exchanger 192A has twenty exchanger units 210, but in other example embodiments, the first heat exchanger 192A may include any suitable number of exchanger units, such as one exchanger unit, eight exchanger units, fifty exchanger units, etc. In addition, in other embodiments, the exchanger units 210 may be placed side by side instead of stacked on each other.

[0039] Reference now Figure 2 , 3 , 4, Figure 3 Provided Figure 2 1 is a perspective view of the first exchanger unit 211 of the first heat exchanger 192A. Figure 4 Provided along Figure 3 4-4 of the cross-sectional view of the core of the first exchanger unit 211. Typically, each exchanger unit 210 of the first heat exchanger 192A has a core and two manifolds. The core of each exchanger unit defines a first channel and a second channel. The first channel can receive a first fluid and the second channel can receive a second fluid. The core of one or more exchanger units 210 can be formed by a plurality of unit cells that are arranged in flow communication with each other. Alternatively, the core of one or more exchanger units 210 can be formed as a monolithic block.

[0040] For example, as shown in the figure, the first switch unit 211 includes a core 240, which defines a first channel 241 (in Figure 4 ) and a second channel 242 (outlined with a dotted line in Figure 4241 can receive the first fluid F1, and the second channel 242 can receive the second fluid F2. The first fluid F1 and the second fluid F2 can be any suitable fluid. The first fluid F1 flowing through the first channel 241 can be hotter than the second fluid F2 flowing through the second channel 242. In this way, as the first fluid F1 and the second fluid F2 flow through the first exchanger unit 211, heat energy can be exchanged between the first fluid F1 and the second fluid F2. For this embodiment, the first fluid F1 (such as Figure 4 The outflow page represented by the "circle point" in FIG. 2 is relative to the second fluid F2 flowing through the second channel 242 (such as Figure 4 The inflow page (represented by the "circle X" in the figure) is in the cross-flow direction.

[0041] Although the core 240 of the first switch unit 211 is Figure 3 Although shown as a straight channel configuration, the core 240 of the first switch unit 210 (as well as the cores of the other switch units 210) may have other suitable configurations, such as a double U-bend channel configuration, a single U-bend configuration, etc.

[0042] The first exchanger unit 211 includes a first manifold 244 and a second manifold 246. Typically, the first manifold 244 distributes the second fluid F2 to the second channel 242 and receives the first fluid F1 from the first channel 241. The first manifold 244 can be arranged to keep the first fluid F1 and the second fluid F2 fluidly separated. Similarly, the second manifold 246 distributes the first fluid F1 to the first channel 241 and receives the second fluid F2 from the second channel 242. The second manifold 246 can be arranged to keep the first fluid F1 and the second fluid F2 fluidly separated. The first manifold 244 and / or the second manifold 246 can be connected to the manifold flow of the adjacent exchanger unit so that the first fluid F1 and / or the second fluid F2 can flow between the exchanger units 210 of the first heat exchanger 192A.

[0043] Each exchanger unit 210 of the first heat exchanger 192A can be configured in the same or similar manner as the first exchanger unit 211 provided above. In this way, each exchanger unit 210 of the first heat exchanger 192A can have a core arranged in the same or similar manner as the core 240 of the first exchanger unit 211 and two manifolds arranged in the same or similar manner as the first manifold 244 and the second manifold 246 of the first exchanger unit 211. The core of each exchanger unit 210 defines a first channel and a second channel, just as the core 240 defines a first channel 241 and a second channel 242.

[0044] Reference now Figure 5, provides a schematic diagram of a heat exchanger 300 according to an exemplary aspect of the present disclosure. The heat exchanger 300 can be similar to the one described above with reference to Figures 1 to 4 The exemplary heat exchanger(s) 192 are configured in a similar manner.

[0045] Figure 5 The exemplary heat exchanger 300 includes a first fluid path defining a first fluid inlet and a first fluid outlet and a second fluid path defining a second fluid inlet and a second fluid outlet. The first fluid path is a "hot" fluid path 302 and the second fluid path is a "cold" fluid path 304. In this manner, the first fluid inlet may be a hot fluid inlet 306, the first fluid outlet may be a hot fluid outlet 308, the second fluid inlet may be a cold fluid inlet 310, and the second fluid outlet may be a cold fluid outlet 312. As used herein, the hot fluid path 302 refers to a fluid path for a fluid that provides heat transfer to a fluid provided through the cold fluid path 304, while as used herein, the cold fluid path 304 refers to a fluid path for a fluid that receives heat transfer from a fluid through the hot fluid path 302.

[0046] During operation of the heat exchanger 300, particularly during operation of the heat exchanger 300 when the turbofan engine 100 incorporating the heat exchanger 300 operates the high voltage spool at 100% capacity or at maximum speed, the heat exchanger 300 defines: a temperature difference θ, in degrees Celsius (C), between the fluid provided through the hot fluid inlet 306 and the fluid provided through the cold fluid inlet 310; a temperature difference β, in degrees Celsius, between the fluid provided through the cold fluid outlet 312 and the fluid provided through the cold fluid inlet 310; a mass flow rate m of the fluid provided through the cold fluid inlet 310 in the heat exchanger 300; c , in kilograms per second (kg / s); the mass flow rate m of the fluid provided through the hot fluid inlet 306 in the heat exchanger 300 h , in kg / s; the specific heat capacity cp of the fluid provided through the cold fluid inlet 310 in the heat exchanger 300 c , in units of joules per kilogram Kelvin (J / kg-K); and the specific heat capacity cp of the fluid provided in the heat exchanger 300 through the hot fluid inlet 306 h , in J / kg-K. These parameters can be used to characterize the effectiveness of heat exchanger 300, as described elsewhere herein.

[0047] As previously mentioned, the inventors unexpectedly discovered during the engine design process that there is a relationship between the compactness of one or more heat exchangers connected to the accessory gearbox of a turbofan engine and the ease with which the heat load is distributed to the one or more heat exchangers connected to the accessory gearbox. This relationship is expressed in terms of heat exchanger capacity. The inventors have discovered that one or more heat exchangers having a heat exchanger capacity within the ranges specified herein provide one or more heat exchangers that are ideally compact and effective in handling the heat loads associated with the accessory gearbox of a turbofan engine.

[0048] Heat exchanger capacity is a dimensionless quantity that is related to the average effectiveness and thermal conductivity associated with one or more heat exchangers, the thermal conductivity being related to certain operational and architectural characteristics of the accessory gearbox, the hydraulic pump mechanically coupled to the accessory gearbox, and the turbofan engine. In particular, heat exchanger capacity captures the relationship between the average effectiveness of one or more heat exchangers connected to the accessory gearbox and the thermal conductivity being related to the accessory gearbox heat load or heat generation, the hydraulic pump power, the fan diameter, length, and the overall pressure ratio of the turbofan engine. Thus, heat exchanger capacity is a function of the average effectiveness and thermal conductivity of one or more heat exchangers connected to the accessory gearbox of the turbofan engine.

[0049] The average effectiveness of the one or more heat exchangers measures how effectively the one or more heat exchangers exchange heat between the respective streams based in part on expected characteristics of the respective streams. The average effectiveness of the one or more heat exchangers is determined by adding the effectiveness of each of the one or more heat exchangers connected to the accessory gearbox and dividing the sum by the number of the one or more heat exchangers. The effectiveness of each of the one or more heat exchangers is determined by correlating various temperature differences, mass flow rates, and heat capacities of the streams passing through the respective heat exchangers.

[0050] As described above, the thermal conductivity is related to the accessory gearbox heat load associated with the accessory gearbox, the hydraulic pump power of the hydraulic pump, the fan diameter, the engine length, and the overall pressure ratio of the turbofan engine. In this regard, the thermal conductivity is based on the architecture of the accessory gearbox and the turbofan engine. Generally, the greater the accessory gearbox heat load and / or the larger the fan diameter, the greater the thermal conductivity. The greater the engine length, the overall pressure ratio, and / or the hydraulic pump power, the smaller the thermal conductivity. A greater average effectiveness and / or thermal conductivity results in an increased heat exchanger capacity, which results in a higher likelihood of handling more heat load associated with the accessory gearbox.

[0051] The range of heat exchanger capacities provided herein for one or more heat exchangers connected to an accessory gearbox captures a specific subset of the configurations of the one or more heat exchangers, the accessory gearbox, and the turbofan engine, taking into account the various pros and cons of selecting one configuration architecture over another for the one or more heat exchangers and / or the turbofan engine. In this regard, as discovered by the inventors, the range of heat exchanger capacities provided herein balances the compactness and weight of the one or more heat exchangers connected to the accessory gearbox, the ability of the one or more heat exchangers to handle the thermal load of the accessory gearbox, the susceptibility of the passages of the one or more heat exchangers to becoming plugged or contaminated, the manufacturability of the one or more heat exchangers, the manufacturability of the accessory gearbox, the gearbox efficiency, speed ratio, and torque output, the power of a hydraulic pump mechanically coupled to the accessory gearbox, the manufacturability of the turbofan engine, and the thrust and speed output of the turbofan engine.

[0052] In addition to discovering the heat exchanger capacity, the inventors have also discovered a relationship between the heat exchanger capacity of one or more heat exchangers connected to an accessory gearbox of a turbofan engine and the rotational speed of a high-voltage spool at one hundred percent capacity (100%), wherein the high-voltage spool is mechanically coupled to the accessory gearbox. The inventors have observed that as the maximum rotational speed of the high-voltage spool of a given turbofan increases, the heat exchanger capacity decreases exponentially. This discovered relationship can be advantageously used to design a turbofan engine and its associated accessory gearbox and heat exchanger because the relationship takes into account the operating characteristics of the engine that affect the heat exchanger capacity. It is noteworthy that, as used herein, operating a high-voltage spool at 100% capacity or at maximum speed refers to an operating condition of a gas turbine engine, wherein the high-voltage spool of the gas turbine engine operates at a rotational speed corresponding to its 100% spool speed capacity. 100% spool speed capacity is a spool operating condition that may occur during takeoff operating conditions, maximum power cruise operating conditions, or other high power operating conditions. In some configurations, the 100% spool speed operating condition may be less than the redline operating speed of the spool.

[0053] In addition, using the heat exchanger capacity, the inventors found that the number of suitable or feasible engine and / or heat exchanger designs that allow the heat exchanger to meet the compactness, weight and heat load requirements can be greatly reduced, thereby helping to more quickly select the design to be considered when developing a turbofan engine with one or more heat exchangers connected to the accessory gearbox. This benefit can provide a deeper understanding of the requirements of a given turbofan engine before specific technology, integration and system requirements are fully developed. It may also prevent late redesign. For example, the selection of the average effectiveness of the heat exchanger can be promoted by utilizing the heat exchanger capacity within the range provided herein, which can help determine the required temperature difference, mass flow rate and thermal capacity of the corresponding flow provided to the heat exchanger. In addition, the use of the heat exchanger capacity within the range provided herein can eliminate or otherwise reduce the implementation of the heat exchanger with too low average effectiveness, making it impractical to merge. Higher average effectiveness values ​​can allow the required amount of heat to be transferred from the heat exchanger without the need for an overly large heat exchanger. In addition, the use of the heat exchanger capacity within the range provided herein can promote the elimination or reduction of bulky heat exchangers.

[0054] Reference now Figure 1 , 2 , 3, 4, 5 and 6, Figure 6 Various relationships between heat exchanger characteristics and operational and architectural characteristics of the turbofan engine are listed and described below. It is noteworthy that the turbofan engine 100 and the one or more heat exchangers 192 are arranged so that the one or more heat exchangers 192 connected to the accessory gearbox 145 have a heat exchanger capacity HEC. Generally, the heat exchanger capacity HEC measures the heat load capacity on the heat exchanger 192 connected to the accessory gearbox 145 of the turbofan engine 100. The heat exchanger 192 is connected to the accessory gearbox 145 because the one or more heat exchangers 192 are configured to handle at least a portion of the heat load of the accessory gearbox 145. The heat exchanger capacity HEC is a dimensionless quantity that is related to the average effectiveness ε of the one or more heat exchangers 192 connected to the accessory gearbox 145. HX_avg Related to the thermal conductivity HCF.

[0055] As will be explained more fully below, the average effectiveness ε HX_avg is a function of various flow characteristics to and from one or more heat exchangers 192 connected to the accessory gearbox 145. The thermal conductivity HCF is a function of certain aspects of the one or more heat exchangers 192 and the turbofan engine 100. Specifically, the thermal conductivity HCF is related to the accessory gearbox heat load Q associated with the one or more heat exchangers 192. GB , the hydraulic pump power P of the hydraulic pump 149 at one hundred percent capacity (100%)H-Pump , fan diameter D of fan 134 FAN , the engine length L of the turbofan engine 100 and the overall pressure ratio OPR of the turbofan engine 100 are related.

[0056] The heat exchanger capacity HEC is defined as one-half the product of the average effectiveness ε of the one or more heat exchangers 192 multiplied by HX_avg It is determined by multiplying it by the thermal conductivity HCF. In other words, the heat exchanger capacity HEC is the average effectiveness ε HX_avg The product of the heat exchanger capacity HEC and the thermal conductivity HCF, the product being raised to the power of half (1 / 2). The heat exchanger capacity HEC is defined by the inventors as follows:

[0057] HEC= (ε HX_avg *HCF) 1 / 2 (1)

[0058] The average effectiveness ε of (1) HX_avg provides a measure of the effectiveness of one or more heat exchangers 192 connected to the accessory gearbox 145. Average effectiveness ε HX_avg is a dimensionless value (ie, has no unit of measure). The average effectiveness ε of the one or more heat exchangers 192 HX_avg Determined by summing the effectiveness of each of N heat exchangers in the one or more heat exchangers and dividing the sum by N, as defined according to (2). In (2), N refers to the total number of heat exchangers connected to the accessory gearbox 145.

[0059]

[0060] For example, for Figure 1 In the illustrated embodiment, there are four (4) heat exchangers 192 connected to the accessory gearbox 145. Therefore, the number of heat exchangers N is four (4). Therefore, the average effectiveness ε of one or more heat exchangers 192 is HX_avg = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε = ε HXN Divide the sum of by 4. Figure 1 In the embodiment, (2) can be rewritten as (2.1) described below:

[0061]

[0062] Wherein the first heat exchanger 192A corresponds to HX1, the second heat exchanger 192B corresponds to HX2, the third heat exchanger 192C corresponds to HX3, and the fourth heat exchanger 192D corresponds to HX4. The effectiveness of a given heat exchanger ε HXProvides a measure of how effectively a heat exchanger transfers heat between two fluids. Given the effectiveness of a heat exchanger, ε HX is a function of: the temperature difference θ between the fluid supplied through the hot fluid inlet and the fluid supplied through the cold fluid inlet, in degrees Celsius (C); the temperature difference β between the fluid supplied through the cold fluid outlet and the fluid supplied through the cold fluid inlet, in degrees Celsius; the mass flow rate m of the fluid supplied through the cold fluid inlet in the heat exchanger c , in kilograms per second (kg / s); the mass flow rate of the fluid provided through the hot fluid inlet in the heat exchanger m h , in kg / s; the specific heat capacity cp of the fluid provided through the cold fluid inlet in the heat exchanger c , expressed in joules per kilogram Kelvin (J / kg-K); and the specific heat capacity cp of the fluid provided through the hot fluid inlet in the heat exchanger h , in J / kg-K. In particular, given the effectiveness of a heat exchanger, ε HX is equal to the mass flow rate m of the fluid supplied through the cold fluid inlet c (Unit: kg / s), specific heat capacity cp of the fluid provided through the cold fluid inlet c The product of the temperature difference β (unit: Celsius) between the fluid supplied through the cold fluid outlet and the fluid supplied through the cold fluid inlet, divided by the temperature difference θ (unit: Celsius) between the fluid supplied through the hot fluid inlet and the fluid supplied through the cold fluid inlet, and the minimum value of the product, which is the mass flow rate m of the fluid supplied through the hot fluid inlet h (Unit: kg / s) and the specific heat capacity cp of the fluid provided through the hot fluid inlet h (in J / kg-K) multiplied by the mass flow rate m of the fluid supplied through the cold fluid inlet c (Unit: kg / s) and the specific heat capacity cp of the fluid provided through the cold fluid inlet c (in J / kg-K). It is worth noting that each of these parameters refers to the value when the high-voltage spool is operated at 100% capacity or at maximum speed. In this way, the inventors have given the effectiveness of the heat exchanger ε HX The definition is as follows:

[0063]

[0064] For example, the effectiveness ε of each heat exchanger of the one or more heat exchangers 192 HX The average effectiveness ε of one or more heat exchangers 192 can be calculated according to (3). HX_avg It can be calculated according to (2). In particular, for Figure 1In the exemplary embodiment of FIG. 1 , as described above, there are four (4) heat exchangers 192 connected to the accessory gearbox 145. Therefore, the effectiveness ε of each of the four heat exchangers 192A, 192B, 192C, 192D is HXN The average effectiveness ε of one or more heat exchangers 192 can be calculated according to (3): HX_avg It can be calculated according to (2.1).

[0065] The average effectiveness ε of one or more heat exchangers 192 HX_avg It is a dimensionless unit of measurement.

[0066] (1) The thermal conductivity HCF describes the thermal load Q of the accessory gearbox. GB , hydraulic pump power P H-Pump 、Fan diameter D FAN , engine length L and overall pressure ratio OPR to transfer heat energy from the accessory gearbox 145 to the one or more heat exchangers 192. In other words, the thermal conductivity HCF represents the ease with which the heat load is distributed to the one or more heat exchangers 192 connected to the accessory gearbox 145. Larger fan diameters and lower overall pressure ratios and engine lengths may provide higher heat transfer potential. Higher accessory gearbox heat loads and lower hydraulic pumping power mean higher availability of heat loads to be handled by the one or more heat exchangers 192.

[0067] The thermal conductivity HCF is defined by the inventors as the product determined by multiplying the first quotient by the second quotient. The first quotient is determined by multiplying the accessory gearbox heat load Q GB Divided by the hydraulic pump power P of the hydraulic pump 149 at one hundred percent capacity (100%) H-Pump The second quotient is determined by dividing the fan diameter D of the fan 134 by FAN The thermal conductivity HCF is determined by dividing the product of the engine length L and the overall pressure ratio OPR of the turbofan engine 100. In this regard, the thermal conductivity HCF is related to the accessory gearbox heat load Q associated with the one or more heat exchangers 192. GB , the hydraulic pump power P of the hydraulic pump 149 at one hundred percent capacity (100%) H-Pump , fan diameter D of fan 134 FAN , the engine length L and the overall pressure ratio OPR of the turbofan engine 100. The thermal conductivity HCF is a dimensionless unit of measurement. The thermal conductivity HCF is defined by the inventors as follows:

[0068] HCF=(Q GB / P H-Pump )*(D FAN / (L×OPR)) (4)

[0069] The accessory gearbox heat load Q associated with the first quotient of (4) is GB is defined as the maximum continuous thrust T associated with the turbofan engine 100 Max.Cont. Multiply by one (1) minus the accessory gearbox efficiency η GB and multiplied by the maximum continuous cruising speed V associated with the turbofan engine 100 Cruise The maximum continuous thrust T Max.Cont. is the maximum continuous thrust that can be generated by the turbofan engine 100, or more precisely, the maximum thrust that the turbofan engine 100 can generate continuously. The maximum continuous cruising speed V Cruise It is the maximum continuous speed at which the turbofan engine 100 can operate during cruise flight, or more precisely, it is the maximum speed that the turbofan engine 100 can continuously achieve during cruise flight. As used herein, cruise flight refers to the flight stage in which the aircraft remains horizontal in altitude after the climb phase and before descending to the approach phase. In various examples, cruise flight can be carried out at a cruise altitude of up to about 65,000ft. In some examples, the cruise altitude is between about 28,000ft and about 45,000ft. In other examples, based on the standard air pressure at sea level, the cruise altitude is represented by a flight altitude (FL), wherein the cruise flight is between FL280 and FL650. In another example, the cruise flight is between FL280 and FL450. In yet other examples, the cruise altitude is defined at least based on atmospheric pressure, wherein the cruise altitude is between about 4.85psia and about 0.82psia based on a sea level pressure of about 14.70psia and a sea level temperature of about 59 degrees Fahrenheit. In another example, the cruising altitude is between about 4.85 psia and about 2.14 psia.It should be appreciated that in certain examples, the range of cruising altitudes defined by pressure may be adjusted based on a different reference sea level pressure and / or sea level temperature.

[0070] Due to the thermal load Q GB Based on the maximum continuous thrust T associated with the turbofan engine 100 Max.Cont. and maximum continuous cruising speed V Cruise , so the accessory gearbox heat load Q GB It may be considered the maximum continuous heat load, or more precisely, the maximum heat load that the accessory gearbox 145 can continuously generate. It should be noted that the maximum continuous heat load is different from the absolute maximum heat load that the accessory gearbox 145 can generate, for example, during takeoff.

[0071] In some embodiments, the accessory gearbox efficiency η of the accessory gearbox 145 is GBFor example, in some embodiments, the accessory gearbox efficiency η of the accessory gearbox 145 is between 99.2 and 99.8. GB It can be between 97 and 99.8, for example between 99.5 and 99.8. Maximum continuous thrust T Max.Cont. The unit of measurement is kilonewton (kN). Maximum cruising speed V Cruise The unit of measurement is meter per second (m / s). Accessory gearbox efficiency η GB Is a dimensionless quantity. Accessory gearbox heat load Q GB Defined by the inventors as follows:

[0072] Q GB =T Max. Cont. *(1-η GB )* V Cruise (5)

[0073] The hydraulic pump power P of the hydraulic pump 149 associated with the first quotient (4) H-Pump is defined as the hydraulic pump continuous torque τ associated with the hydraulic pump 149 H-Pump Multiply by the speed ratio n of the hydraulic pump 149 Speed Ratio The product is then multiplied by the rotational speed N2 of the high pressure spool or HP spool 131 at one hundred percent capacity (100%). H-Pump The unit of measurement is kilowatt (kW). Hydraulic pump continuous torque τ H-Pump The unit of measurement is Newton meter (Nm). Speed ​​ratio n Speed Ratio is a dimensionless quantity. The unit of measurement of the rotational speed N2 of the high-voltage spool 131 is revolutions per minute (RPM) at one hundred percent (100%) capacity. In some embodiments, the hydraulic pump continuous torque τ associated with the hydraulic pump 149 H-Pump The speed ratio of the hydraulic pump 149 can be between 20 Nm and 350 Nm. Speed Ratio It can be between 0.05 and 0.75. Hydraulic pump power P H-Pump Defined by the inventors as follows:

[0074] P H-Pump = τ H-Pump *n Speed Ratio *N2 (6)

[0075] The fan diameter D associated with the second quotient (4) FAN is defined as the distance across the leading edge tip of one fan blade 136 to the leading edge tip of the diametrically opposite fan blade 136. In other words, the fan diameter D FANDefined as the fan radius R FAN Multiply by two, or in other words, defined as D FAN =R FAN *2, where the fan radius R FAN Spanning from longitudinal centerline 102 to the leading edge tip of one of fan blades 136. Fan diameter D FAN The unit of measurement is meter (m). In some exemplary embodiments, the fan diameter D of the fan 134 of the turbofan engine 100 is FAN The fan diameter D of the fan 134 of the turbofan engine 100 is between 0.5 m and 5 m, for example, between 0.7 m and 3.5 m. FAN In the case where the fan section 104 includes a plurality of fan stages, the fan diameter D FAN Will be determined based on the fan with the largest fan diameter.

[0076] The inventors define the engine length L associated with the second quotient of (4) as the length from the front tip of the rotatable rotor to the rear flange of the turbofan engine 100 along the axial direction A of the turbofan engine 100. In some embodiments, the engine length L may be between 3 meters and 10 meters.

[0077] The overall pressure ratio OPR refers to the pressure of the gas flow at the outlet of the compressor section (e.g., at a location immediately downstream of the most downstream stage of the compressor rotor blades of the HP compressor 116) and the pressure of the gas flow provided to the turbine (e.g., Figure 1 In some embodiments, the overall pressure ratio OPR may be between 10 and 80.

[0078] In some embodiments, for a rotational speed N2 of the high voltage spool 131 between 7,500 and 35,000 revolutions per minute (RPM) at one hundred percent (100%) capacity and for an accessory gearbox efficiency η between 97% and 99.8%. GB , the heat exchanger capacity HEC is between 0.055 and 0.514. In other embodiments, for a rotation speed N2 of the high voltage spool 131 between 7,500 and 35,000 revolutions per minute (RPM) at one hundred percent (100%) capacity and for an accessory gearbox efficiency η between 98% and 99.8%. GB , the heat exchanger capacity HEC is between 0.055 and 0.313. Figure 7 The heat exchanger capacity HEC of these example embodiments is graphically depicted as a function of the rotational speed N2 of the high voltage spool 131 .

[0079] Reference Figure 8 , various example turbofan engines are provided, each having one or more heat exchangers connected to an accessory gearbox. In each example, the accessory gearbox is mechanically coupled to a high-voltage spool of the corresponding turbofan engine. One or more engine accessories of the corresponding turbofan engine are mechanically coupled to the corresponding accessory gearbox. For example, a hydraulic pump of the corresponding turbofan engine can be mechanically coupled to the corresponding accessory gearbox.

[0080] Fig. 9 A flow chart is provided for a method 400 of operating a turbofan engine having one or more heat exchangers connected to an accessory gearbox of the turbofan engine.For example, the turbofan engine may be installed on an aircraft.

[0081] At 402, method 400 includes operating a turbofan engine having a low pressure spool, a fan mechanically coupled to the low pressure spool, a high pressure spool, an accessory gearbox mechanically coupled to the high pressure spool, a hydraulic pump mechanically coupled to the accessory gearbox, and one or more heat exchangers connected to the accessory gearbox, the one or more heat exchangers having a heat exchanger capacity defined by one-half power of a product determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a thermal conductivity related to an accessory gearbox heat load associated with the accessory gearbox, a hydraulic pump power of the hydraulic pump, a fan diameter of the fan, an engine length of the turbofan engine, and an overall pressure ratio of the turbofan engine, wherein for a rotational speed of the high pressure spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.514. The heat exchanger capacity according to this embodiment is between 0.055 and 0.514. Figure 7 Represented graphically in .

[0082] In some embodiments, the average effectiveness of the one or more heat exchangers is determined by adding the effectiveness of each of the one or more heat exchangers connected to the accessory gearbox and dividing the sum by the number of the one or more heat exchangers. The effectiveness of each of the one or more heat exchangers is determined by correlating various temperature differences, mass flow rates, and heat capacities of the flows through the respective heat exchangers.

[0083] Additionally, in some embodiments, the thermal conductivity is defined as a product determined by multiplying a first quotient determined by dividing the accessory gearbox heat load by the hydraulic pump power of the hydraulic pump at one hundred percent capacity by a second quotient determined by dividing the fan diameter of the fan by the engine length and the overall pressure ratio of the turbofan engine.

[0084] In some embodiments, the accessory gearbox heat load is defined as the product determined by multiplying the maximum continuous thrust associated with the turbofan engine by one minus the accessory gearbox efficiency of the accessory gearbox and multiplying by the maximum cruise speed associated with the turbofan engine.

[0085] In some embodiments, the hydraulic pump power of the hydraulic pump is defined as the product determined by multiplying the hydraulic pump continuous torque associated with the hydraulic pump by the speed ratio of the hydraulic pump by the rotational speed of the high pressure spool at one hundred percent (100%) capacity.

[0086] The fan diameter of the fan is defined as the distance across the leading edge tip of one fan blade of the fan to the leading edge tip of the diametrically opposite fan blade. In other words, the fan diameter is defined as the fan radius multiplied by two, where the fan radius spans from the longitudinal centerline of the turbofan engine to the leading edge tip of one of the fan blades. The bypass ratio of the turbofan engine is defined by the ratio of the mass flow rate of a first portion of air flowing through the bypass passage to the mass flow rate of a second portion of air entering the engine core through the core inlet.

[0087] In some embodiments, the one or more heat exchangers connected to the accessory gearbox include a fuel-oil heat exchanger, an air-oil heat exchanger, and an oil-oil heat exchanger. In some embodiments, the one or more heat exchangers connected to the accessory gearbox include at least one of each of a fuel-oil heat exchanger, an air-oil heat exchanger, and an oil-oil heat exchanger, and at least two of one of a fuel-oil heat exchanger, an air-oil heat exchanger, and an oil-oil heat exchanger.

[0088] In some embodiments, the one or more heat exchangers include at least four (4) heat exchangers. In some embodiments, the one or more heat exchangers include at least three (3) heat exchangers. In some embodiments, the one or more heat exchangers include at least two (2) heat exchangers. In some embodiments, the one or more heat exchangers include one (1) heat exchanger. In some embodiments, the one or more heat exchangers include between four (4) and ten (10) heat exchangers.

[0089] Although specific features of various embodiments may be shown in some drawings and not in other drawings, this is for convenience only. According to the principles of the present disclosure, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0090] This written description uses examples to disclose the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the present disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the present disclosure is defined by the claims, and may include other examples that occur to one skilled in the art. Such 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.

[0091] Further aspects are provided by the subject matter of the following clauses:

[0092] A turbofan engine comprising: a low pressure spool; a fan mechanically coupled to the low pressure spool; a high pressure spool; an accessory gearbox mechanically coupled to the high pressure spool; a hydraulic pump mechanically coupled to the accessory gearbox; and one or more heat exchangers connected to the accessory gearbox, the one or more heat exchangers having a heat exchanger capacity defined by one-half power of a product determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a thermal conductivity related to an accessory gearbox heat load, a hydraulic pump power of the hydraulic pump, a fan diameter of the fan, an engine length of the turbofan engine, and an overall pressure ratio of the turbofan engine, and wherein for a rotational speed of the high pressure spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.514.

[0093] A turbofan engine according to one or more of the preceding clauses, wherein the average heat exchanger effectiveness is determined by dividing the sum of the heat exchanger effectiveness of each of the one or more heat exchangers connected to the accessory gearbox by N, wherein N is the number of heat exchangers connected to the accessory gearbox.

[0094] A turbofan engine according to one or more of the preceding clauses, wherein the one or more heat exchangers each have one or more exchanger units, each exchanger unit having a core defining a plurality of channels.

[0095] The turbofan engine of claim 1, wherein the average heat exchanger effectiveness is between 0.25 and 0.95.

[0096] A turbofan engine according to one or more of the preceding clauses, wherein the thermal conductivity is defined as a product determined by multiplying a first quotient determined by dividing the accessory gearbox heat load by the hydraulic pump power of the hydraulic pump at one hundred percent capacity by a second quotient determined by dividing the fan diameter by the product of the engine length and the overall bypass ratio.

[0097] A turbofan engine according to one or more of the preceding clauses, wherein the accessory gearbox heat load is defined as the product determined by multiplying the maximum continuous thrust associated with the turbofan engine by one minus the accessory gearbox efficiency of the accessory gearbox and multiplying by the maximum cruise speed associated with the turbofan engine.

[0098] A turbofan engine according to one or more of the preceding clauses, wherein the accessory gearbox efficiency is between 97 and 99.8.

[0099] A turbofan engine according to one or more of the preceding clauses, wherein the hydraulic pump power of the hydraulic pump is defined as the product determined by multiplying the hydraulic pump continuous torque associated with the hydraulic pump by the speed ratio of the hydraulic pump by the rotational speed of the high pressure spool at one hundred percent capacity.

[0100] A turbofan engine according to one or more of the preceding clauses, wherein for the rotational speed of the high voltage spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.313.

[0101] A turbofan engine according to one or more of the preceding clauses, wherein the accessory gearbox efficiency is between 98 and 99.8.

[0102] A turbofan engine according to one or more of the preceding clauses, wherein N is the number of heat exchangers connected to the accessory gearbox, wherein the average heat exchanger effectiveness is equal to the heat exchanger effectiveness of each of the heat exchangers connected to the accessory gearbox.

[0103] A turbofan engine according to one or more of the preceding clauses, wherein each of the heat exchangers connected to the accessory gearbox defines a heat exchanger, the heat exchanger defining: a hot fluid inlet, a hot fluid outlet, a cold fluid inlet, a cold fluid outlet, a temperature difference θ between a fluid provided through the hot fluid inlet and a fluid provided through the cold fluid inlet, in degrees Celsius (C); a temperature difference β between the fluid provided through the cold fluid outlet and the fluid provided through the cold fluid inlet, in degrees Celsius; a mass flow rate m of the fluid provided through the cold fluid inlet in the heat exchanger c , in kilograms per second (kg / s); the mass flow rate m of the fluid provided in the heat exchanger through the hot fluid inlet h , in kg / s; the specific heat capacity cp of the fluid provided in the heat exchanger through the cold fluid inlet c , in Joules per kilogram Kelvin (J / kg-K); and the specific heat capacity cp of the fluid provided in the heat exchanger through the hot fluid inlet h , in J / kg-K, and wherein the heat exchanger effectiveness of each of the heat exchangers connected to the accessory gearbox is equal to:

[0104]

[0105] A turbofan engine according to one or more of the preceding clauses, wherein the one or more heat exchangers include a fuel-oil heat exchanger, an air-oil heat exchanger and an oil-oil heat exchanger.

[0106] A turbofan engine according to one or more of the preceding clauses, wherein the one or more heat exchangers include at least four heat exchangers and at most ten heat exchangers.

[0107] A turbofan engine according to one or more of the preceding clauses, wherein the speed ratio of the hydraulic pump is between 0.05 and 0.75.

[0108] A turbofan engine according to one or more of the preceding clauses, wherein said continuous torque of said hydraulic pump is between 20 Nm and 350 Nm.

[0109] A method includes operating a turbofan engine having a low pressure spool, a fan mechanically coupled to the low pressure spool, a high pressure spool, an accessory gearbox mechanically coupled to the high pressure spool, a hydraulic pump mechanically coupled to the accessory gearbox, and one or more heat exchangers connected to the accessory gearbox, the one or more heat exchangers having a heat exchanger capacity defined by one-half power of a product determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a thermal conductivity related to an accessory gearbox heat load associated with the accessory gearbox, a hydraulic pump power of the hydraulic pump, a fan diameter of the fan, an engine length of the turbofan engine, and an overall pressure ratio of the turbofan engine, and wherein for a rotational speed of the high pressure spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.514.

[0110] A method as in one or more of the preceding clauses, wherein the accessory gearbox efficiency is between 97 and 99.8.

[0111] The method according to one or more of the preceding clauses, wherein for the rotational speed of the high voltage spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.313.

[0112] A method as in one or more of the preceding clauses, wherein the accessory gearbox efficiency is between 98 and 99.8.

[0113] A method according to one or more of the preceding clauses, wherein the average heat exchanger effectiveness is determined by dividing the sum of the heat exchanger effectiveness of each of the one or more heat exchangers connected to the accessory gearbox by N, wherein N is the number of heat exchangers connected to the accessory gearbox, and wherein the thermal conductivity is defined as a product determined by multiplying a first quotient determined by dividing the accessory gearbox heat load by the hydraulic pump power of the hydraulic pump at one hundred percent capacity by a second quotient determined by dividing the fan diameter by the product of the engine length and the overall bypass ratio.

[0114] The method according to one or more of the preceding clauses, wherein the fan diameter is between 0.5 meters (m) and 5 m.

[0115] A cooling system for a turbofan engine, comprising: one or more heat exchangers, the one or more heat exchangers being connected to an accessory gearbox of the turbofan engine, the one or more heat exchangers having a heat exchanger capacity, the heat exchanger capacity being defined by one-half power of a product determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a thermal conductivity, the thermal conductivity being related to an accessory gearbox heat load, a hydraulic pump power of the hydraulic pump, a fan diameter of a fan of the turbofan engine, an engine length of the turbofan engine, and an overall pressure ratio of the turbofan engine, and wherein for a rotational speed of the high pressure spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.514.

Claims

1. A turbofan engine, characterized in that: include: Low-voltage spools; a fan, the fan being mechanically coupled to the low-voltage spool; High voltage spools; an accessory gearbox mechanically coupled to the high voltage spool; a hydraulic pump mechanically coupled to the accessory gearbox; and one or more heat exchangers connected to the accessory gearbox, the one or more heat exchangers having a heat exchanger capacity defined by one-half of a product determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a thermal conductivity related to an accessory gearbox heat load, a hydraulic pump power of the hydraulic pump, a fan diameter of the fan, an engine length of the turbofan engine, and an overall pressure ratio of the turbofan engine, and Wherein for a rotational speed of the high voltage spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.

514.

2. The turbofan engine according to claim 1, characterized in that: The speed ratio of the hydraulic pump is between 0.05 and 0.

75.

3. The turbofan engine according to claim 1, characterized in that: The one or more heat exchangers each have one or more exchanger units, each exchanger unit having a core defining a plurality of channels.

4. The turbofan engine according to claim 1, characterized in that: Wherein the average heat exchanger effectiveness is between 0.25 and 0.

95.

5. The turbofan engine according to claim 1, characterized in that: wherein the thermal conductivity is defined as a product determined by multiplying a first quotient determined by dividing the accessory gearbox heat load by the hydraulic pump power of the hydraulic pump at one hundred percent capacity by a second quotient determined by dividing the fan diameter by the product of the engine length and the overall bypass ratio.

6. The turbofan engine according to claim 5, characterized in that: Wherein the accessory gearbox heat load is defined as a product determined by multiplying a maximum continuous thrust associated with the turbofan engine by one minus an accessory gearbox efficiency of the accessory gearbox and multiplying by a maximum cruise speed associated with the turbofan engine.

7. The turbofan engine according to claim 6, characterized in that: The accessory gearbox efficiency is between 97 and 99.8%.

8. The turbofan engine according to claim 5, characterized in that: The hydraulic pump power of the hydraulic pump is defined as the product determined by multiplying a hydraulic pump continuous torque associated with the hydraulic pump by a speed ratio of the hydraulic pump by a rotational speed of the high pressure spool at one hundred percent capacity.

9. The turbofan engine according to claim 1, characterized in that: Wherein for the rotational speed of the high voltage spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity, the heat exchanger capacity is between 0.055 and 0.

313.

10. The turbofan engine according to claim 9, characterized in that: The continuous torque of the hydraulic pump is between 20 Nm and 350 Nm.

Images