AIRPLANE

Description

Field of the Disclosure

[0001] The present disclosure relates to an aircraft having a single engine air intake aperture and a single engine exhaust aperture for each engine and particularly, but not exclusively, to an aircraft having a single engine air intake aperture and a single engine exhaust aperture with an airframe heat exchanger positioned in the air intake aperture.Background to the Disclosure

[0002] A conventional turbofan gas turbine engine uses heat exchangers to cool a variety of fluids including inter alia air, fuel and oil. Typically, such heat exchangers use bypass air or an air offtake from the compressor as the cooling medium. The heat exchanger itself may be positioned in the bypass duct or externally to the engine with the corresponding ducting.

[0003] The use of bypass air or a compressor offtake stream as the cooling medium in a heat exchanger will adversely affect the performance of the engine, for example by reducing specific thrust or increasing specific fuel consumption. Alternatively, or additionally, such off takes can adversely affect engine performance, for example by reducing surge margin.

[0004] In a further alternative conventional arrangement, an airflow to provide the cooling medium in a heat exchanger may be drawn separately from the airflow through the gas turbine engine. For example, in an airframe application the airflow providing the cooling medium may be drawn from an air intake or duct separate from the engine.

[0005] European patent application EP 1 916 399 A2 discloses a heat exchanger assembly for a gas turbine engine, the assembly comprising a radially inner plate, a radially outer plate, and a heat exchanger coupled between the radially inner and outer plates. The heat exchanger assembly has a substantially arcuate shape and may be coupled to a fan casing of a gas turbine engine such that the heat exchanger is positioned upstream of the engine's the fan assembly. US patent application publication 2019 / 0145273 A1 and US patent 5,209,428 each disclose a respective aircraft in which two engine inlet apertures are coupled to the input of a gas turbine engine by a bifurcated inlet duct. US patent application publication 2017 / 0030266 A1 discloses a cooling system for a gas turbine engine, the cooling system comprising multiple heat source exchangers arranged to transfer heat from multiple accessory systems of an engine to a heat exchange fluid within a thermal transport bus, and multiple heat sink exchangers coupled to the thermal transport bus downstream of the heat source exchangers, the heat sink exchangers being arranged to transfer heat from the heat exchange fluid within the thermal transport bus to the atmosphere or to the fuel supply or fan stream of the engine.

[0006] As used herein, a range "from value X to value Y" or "between value X and value Y", or the likes, denotes an inclusive range; including the bounding values of X and Y. As used herein, the term "axial plane" denotes a plane extending along the length of an engine, parallel to and containing an axial centreline of the engine, and the term "radial plane" denotes a plane extending perpendicular to the axial centreline of the engine, so including all radial lines at the axial position of the radial plane. Axial planes may also be referred to as longitudinal planes, as they extend along the length of the engine. A radial distance or an axial distance is therefore a distance in a radial or axial plane, respectively.Statements of Disclosure

[0007] According to a first aspect of the present disclosure, there is provided an aircraft comprising a machine body, a single cooling fluid-to-air heat exchanger, a turbofan gas turbine engine and a plurality of ancillary systems, the machine body enclosing the plurality of ancillary systems and, in axial flow sequence, the cooling fluid-to-air heat exchanger and the gas turbine engine, the turbofan gas turbine engine comprising, in axial flow sequence, a fan module, a compressor module, a combustor module, a turbine module, and an exhaust module; wherein the machine body has either one or two fluid inlet apertures only, the or each fluid inlet aperture being configured to allow an air flow to enter the machine body and to pass through the cooling fluid-to-air heat exchanger, the cooling fluid-to-air heat exchanger being configured to transfer a waste heat load from the turbofan gas turbine engine and the ancillary systems to the air flow prior to entry thereof into the fan module and wherein the machine body has a single fluid exhaust aperture configured to channel fluid flow from the exhaust module out of the machine body and the machine body is otherwise free of fluid inlet and exhaust apertures.

[0008] By performing all aircraft cooling through the inlet air stream that feeds the turbofan gas turbine engine, other air intakes and scoops to provide cooling air flows to the airframe can be eliminated. Minimising the quantity of apertures on the airframe will reduce the aerodynamic drag on the airframe and so improve the aerodynamic efficiency of the airframe.

[0009] The use of 'cool' inlet air to absorb waste heat load maximises the heat exchanger efficiency. Reducing the temperature of the heat energy absorbing fluid in the heat exchanger will increase the efficiency of the heat exchanger by increasing the temperature differential between the primary and secondary fluids in the heat exchanger.

[0010] In this arrangement, all the active heat rejection (from the gas turbine engine and the ancillary systems) is rejected into the fluid flow entering the gas turbine engine. It will be understood that there may be some passive heat rejection through the surface of the machine body.

[0011] In contrast, the engine offtake flow used in a conventional turbofan engine (for example from a compressor stage or from the bypass flow) for providing a cooling feed flow to a heat exchanger will have a considerably higher temperature than the intake air flow entering the turbofan engine. This in turn limits the temperature at which heat can be rejected to the heat exchanger to temperatures that are greater than that of the corresponding engine offtake flow. Such a prior art arrangement will also require a larger and less efficient heat exchanger than that of the present invention for the same quantity of heat rejection. In addition, such conventional arrangements result in a loss of propulsive flow and a consequent reduction in overall engine efficiency.

[0012] In an aircraft according to the present disclosure, the location of the heat exchanger in an inlet duct upstream of the fan assembly means that the engine is able to use all of the intake air that is used by the heat exchanger module to dissipate waste energy to subsequently provide propulsive thrust. This means that an aircraft according to the present disclosure can be more efficient than a conventional aircraft while providing the same level of heat exchanger capacity.

[0013] The positioning of the heat exchanger upstream of the fan assembly means that the cooling air flow entering the heat exchanger has a temperature that is lower than any engine offtake flow, for example a bleed flow from a compressor stage or the bypass flow. Consequently, in a turbofan engine according to the present disclosure it becomes possible to reject heat to the heat exchanger flow at a lower temperature than can be achieved with any prior art arrangement described above. This makes the turbofan engine according to the present disclosure more versatile than conventional turbofan engines.

[0014] The machine body may comprise two fluid inlet apertures only, each being configured to allow a respective air flow to enter the machine body, the machine body being configured such that the two air flows are blended together prior to entry of a resulting blended fluid flow into the cooling fluid-to-air heat exchanger.

[0015] The single blended intake air flow to the turbofan gas turbine engine passes through the cooling fluid-to-air heat exchanger prior to entry into the fan module.

[0016] The use of a single exhaust aperture minimises the aerodynamic drag associated with an exhaust stream from the turbofan gas turbine engine (or engines) leaving the aircraft. Optionally, the fan assembly comprises a plurality of fan blades defining a fan diameter (D), and the fan diameter D is within the range of 0.3m to 2.0m, preferably within the range 0.4m to 1.5m, and more preferably in the range of 0.7m to 1.0m.Brief Description of the Drawings

[0017] There now follows a description of an embodiment of the disclosure, by way of non-limiting example, with reference being made to the accompanying drawings in which: Figure 1 shows a schematic perspective view of an aircraft according to a first embodiment of the disclosure; Figure 2 shows a schematic sectional view of the aircraft of Figure 1; Figure 3 shows a schematic view of the heat exchanger module and fan module of the turbofan gas turbine engine of the aircraft of Figure 1; Figure 4 shows a schematic sectional view of the heat exchanger module and fan module of the turbofan gas turbine engine of the aircraft of Figure 1; and Figure 5 shows an alternative arrangement of the heat exchanger module and fan module shown in Figure 4.

[0018] It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.Detailed Description

[0019] Referring to Figures 1 and 2, an aircraft according to a first embodiment of the disclosure is designated generally by the reference numeral 100. The aircraft 100 comprises a machine body 102 in the form of a fuselage with wings and a tail plane. The machine body 102 encloses a turbofan gas turbine engine 110, together with a plurality of ancillary systems 104.

[0020] Within the machine body 102 there is a cockpit volume 106, a payload volume 108, and a plurality of ancillary systems 104.

[0021] The turbofan gas turbine engine 110 comprises, in axial flow sequence, a heat exchanger module 120, a fan module 130, a compressor module 140, a combustor module 150, a turbine module 160, and an exhaust module 170. The turbofan gas turbine engine 110 further comprises a second heat transfer element 124. The second heat transfer element 124 takes the form of a heat exchanger that uses the engine's fuel as a cooling medium.

[0022] The fan module 130, compressor module 140, combustor module 150, turbine module 160, and exhaust module 170, together forming the core engine, are enclosed within an outer casing 180. An annular bypass duct 182 is defined between the core engine and the outer casing 180.

[0023] The heat exchanger module 120 comprises a plurality of first heat exchanger elements 122. In the present arrangement, illustrated in Figure 3, the first heat exchanger elements 122 are arranged as a circumferential array of radially extending vanes 122. The inlet air flow 101 passes over the surface of the first heat exchanger elements 122 as the air flow passes through the heat exchanger module 120.

[0024] The heat exchanger module 120 has a total heat rejection capacity. The total heat rejection capacity is the amount of waste heat energy that can be dissipated into an air flow passing through the heat exchanger module 120.

[0025] The machine body 102 comprises only one fluid inlet aperture 112. The fluid inlet aperture 112 is configured to allow an intake air flow 101 to enter the machine body 102. In other words, there is only one inlet aperture 112 on the machine body 102 through which an air flow 101 can enter the machine body 102.

[0026] The intake air flow 101 passes through the heat exchanger module 120 and subsequently passes through the fan module 130. Once through the fan module, the air flow divides into a first flow (not shown) and a second flow (not shown). The first flow (the 'core' flow) passes sequentially through the core engine, i.e. sequentially through compressor module 140, the combustor module 150, the turbine module 160, and the exhaust module 170. The second flow (the 'bypass' flow) exits the fan module 130 and passes through the annular bypass duct 182 to the exhaust module 170.

[0027] The machine body 102 further comprises only one fluid exhaust aperture 104. The air flow from the exhaust module 170 exits the machine body 102 through the single fluid exhaust aperture 104. In other words, there is only one exhaust aperture 104 in the machine body 102 through which an air flow 101 can exit the machine body 102.

[0028] As outlined above, the machine body 102 of present disclosure includes only two apertures 112,114 in its outer surface; an inlet aperture 112 allowing an air flow into the machine body and an exhaust aperture 114 allowing the air flow to exhaust from the machine body. The presence of apertures in the machine body 102 causes parasitic aerodynamic drag on the machine body 102. As in the present arrangement, the use of only two apertures 112,114 in the machine body 102 minimises this parasitic aerodynamic drag.

[0029] In the present arrangement, the fan assembly 130 comprises two fan stages (not shown), with each fan stage comprising a plurality of fan blades (not shown). In the present arrangement each fan stage has the same fan diameter 132, with the respective plurality of fan blades defining a fan diameter of 0.9m. In an alternative arrangement, the two fan stages may have different fan diameters 132 each defined by the corresponding plurality of fan blades. As previously mentioned, the fan diameter (D) 132 is defined by a circle circumscribed by the leading edges of the respective plurality of fan blades.

[0030] In use, both the turbofan gas turbine engine 110 and the ancillary systems 104 generate waste heat energy that is required to be dissipated to ensure the safe operation of the turbofan engine 110 and the ancillary systems 104.

[0031] As shown in Figure 3, the heat exchanger module 120 has a flow area (A HEX ) 126. The heat exchanger module flow area 126 is the cross-sectional area of the heat exchanger module 120 through which an inlet air flow 101 passes before being ingested by the fan module 130. In the present arrangement, the heat exchanger module flow area 126 has an annular cross-section and corresponds directly to the shape of the air flow passing through the heat exchanger module 120.

[0032] The fan module 130 has a corresponding flow area (A FAN ) 134. The fan module flow area 134 is the cross-sectional area of the fan module 130 through which an inlet air flow 101 passes before separating into the core engine flow and the bypass flow. The fan assembly flow area 134 has an annular shape since it corresponds to the annular area swept by the fan blades 131.

[0033] In the present arrangement (illustrated in Figure 4) the heat exchanger module flow area 126 is equal to the fan module flow area 134, and the corresponding ratio of A HEX / A FAN is equal to 1.0.

[0034] The heat exchanger module 120 has a flow diameter (E) 128, which is the diameter of the air flow passing through the heat exchanger module 120. In the present arrangement, shown in Figure 4, the heat exchanger module flow diameter 128 is equal to the fan diameter 132. In an alternative arrangement (see Figure 5) the heat exchanger module flow diameter 228 is greater than the fan diameter 132.

[0035] The heat exchanger module 120 is configured to transfer a waste heat load from the gas turbine engine 110 and the ancillary systems 104 to the fluid flow 101 prior to the entry of the fluid flow 101 into the fan module 130. A first fluid 116, which in this embodiment is a synthetic oil, is circulated through hot portions of the turbofan engine 110 and the ancillary systems 104 to collect waste heat energy.

[0036] As outlined above, once the air flow 101 has passed through the fan module 130, the air flow 101 divides into two flow portions, a first portion being the so-called 'core flow', and a second portion being the so-called 'bypass flow'. The core flow enters the compressor module 140 and continues sequentially through the combustor module 150, turbine module 160, and exhaust module 170. The bypass flow passes through the annular bypass duct 182 into the exhaust module 170. The core flow and the bypass flow join in the exhaust module 170 and are exhausted from the machine body 102 through the exhaust aperture 114.

[0037] The core flow can be characterised by the parameter B COMB which represents the proportion of the fluid flow 101 entering the machine body 102 that subsequently passes sequentially through the compressor, combustor, turbine and exhaust modules 140,150,160,170. In the present arrangement, the turbofan engine 110 has a bypass ratio of 2. In this arrangement, the turbofan engine 110 can be characterised by a B COMB parameter of 0.29.

[0038] In use, at a cruise condition the aircraft 100 is capable of maintaining a sustained airspeed V (in metres per second, m / s). A definition for the cruise condition has been provided earlier in the disclosure. At this sustained airspeed V, the heat exchanger module 120 transfers a total waste heat energy load H (in Watts, W) to the fluid flow 101.

[0039] In use, when the sustained airspeed V of the aircraft 100 is less than Mach 1.0 (i.e. the aircraft 100 is in subsonic flight) the first fluid 116 is circulated through the first heat exchanger elements 122 to dissipate the waste heat energy contained in the first fluid 116 to the inlet fluid flow 101.

[0040] When the sustained airspeed V of the aircraft 100 exceeds, for example, Mach 1.0 (i.e. supersonic flight conditions) the temperature of the inlet fluid flow (T A ) 101 increases. This temperature increase will significantly reduce the efficiency of the transfer of the waste heat energy from the first fluid 116 to the inlet fluid flow 101. Continued increase in the sustained airspeed V of the aircraft 100 will cause a continued rise in the temperature of the inlet fluid flow 101. Once this temperature T A reaches the temperature of the first fluid (T F ) 116 it will not be possible to dissipate waste heat energy to the inlet fluid flow101 via the first heat transfer elements 122.

[0041] Consequently, in the arrangement of the present invention, when the airflow temperature T A is equal to or greater than the first fluid temperature T F , the flow of the first fluid 116 is routed through the second heat transfer element 124. The second heat transfer element 124 uses the fuel supply to the turbofan engine 110 as the cooling medium.

[0042] While the temperature of the inlet fluid flow T A 101 will increase at and above a sustained airspeed of, for example, M1.0, the temperature of the engine's fuel will remain substantially constant. By routing the first fluid 116 through the second heat transfer element 124 it becomes possible to continue to dissipate the waste heat energy from the turbofan engine 110 and the ancillary systems 104 even when the temperature of the inlet fluid flow 101 is greater than the temperature of the first fluid 116.

[0043] Note that the terms "low-pressure turbine" and "low-pressure compressor" as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan 23) respectively and / or the turbine and compressor stages that are connected together by the interconnecting shaft 26 with the lowest rotational speed in the engine. In some literature, the "low-pressure turbine" and "low-pressure compressor" referred to herein may alternatively be known as the "intermediate-pressure turbine" and "intermediate-pressure compressor". Where such alternative nomenclature is used, the fan 23 may be referred to as a first, or lowest pressure, compression stage.

[0044] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and / or turbines and / or an alternative number of interconnecting shafts. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example.

[0045] The geometry of the gas turbine engine 10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in Figure 1), and a circumferential direction (perpendicular to the page in the Figure 1 view). The axial, radial and circumferential directions are mutually perpendicular.

[0046] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein. Apart from these theoretical considerations, it should be noted that the scope of the claimed invention is defined in the appended claims.

Claims

1. An aircraft (100) comprising a machine body (102), a single cooling fluid-to-air heat exchanger (120), a turbofan gas turbine engine (110) and a plurality of ancillary systems (104), the machine body enclosing the plurality of ancillary systems and, in axial flow sequence, the cooling fluid-to-air heat exchanger and the turbofan gas turbine engine, the turbofan gas turbine engine comprising, in axial flow sequence, a fan module (130), a compressor module (140), a combustor module (150), a turbine module (160), and an exhaust module (170); wherein the machine body has either one or two fluid inlet apertures (112) only, the or each fluid inlet aperture being configured to allow an air flow (101) to enter the machine body and to pass through the cooling fluid-to-air heat exchanger, the cooling fluid-to-air heat exchanger being configured to transfer a waste heat load from the turbofan gas turbine engine and the ancillary systems to the air flow prior to entry thereof into the fan module and wherein the machine body has a single fluid exhaust aperture configured to channel fluid flow from the exhaust module out of the machine body and the machine body is otherwise free of fluid inlet and exhaust apertures.

2. An aircraft according to Claim 1, wherein the machine body comprises two fluid inlet apertures only, each of which is configured to allow a respective air flow to enter the machine body, the machine body being configured such that the two air flows are blended together prior to entry of a resulting blended fluid flow into the cooling fluid-to-air heat exchanger.

3. An aircraft (100) according to claim 1 or claim 2, wherein the fan assembly comprises a plurality of fan blades (131) defining a fan diameter (132), and wherein the fan diameter (132) is within the range of 0.3m to 2.0m, preferably within the range 0.4m to 1.5m, and more preferably in the range of 0.7m to 1.0m.