Exhaust cone heat exchanger (HEX)

Abstract

An aircraft fuel heating arrangement includes an exhaust cone for a gas turbine engine, the exhaust cone having an outer body defining an inner cone cavity, the inner cone cavity including one or more conduits therethrough for passing fuel through the cavity, and wherein the one or more conduits are disposed in the outer body. The outer body of the exhaust cone includes at least one inlet and at least one outlet to allow exhaust gas to enter and exit the exhaust cone.

Description

Technical Field

[0001] The present invention relates to alternative aircraft propulsion systems including conventional fuels, and also to aircraft propulsion systems that can operate using non-conventional aviation fuels, such as cryogenic fuels. Background Art

[0002] Conventional gas turbine engines of the type used in commercial aircraft are designed to operate using kerosene-based fuels, which are combusted to produce engine thrust.Such engines are well known and understood in the art.

[0003] According to most estimates, air traffic is expected to double every fifteen years, resulting in a significant increase in pollutants produced by such conventional engines. In order to meet the emission reduction targets set by the International Air Transport Association, the use of alternative fuels has been identified as a possible avenue to explore. Alternative fuels include biofuels, synthetic kerosene, compressed gases and other fuels including cryogenic fuels.

[0004] With cryogenic fuels, the fuel is stored at extremely low temperatures and is heated before combustion in the engine. This heat can be generated in a variety of ways, such as by electrical heating and / or direct heating from the engine airflow. Engine heating advantageously provides a convenient steady-state arrangement in which the heat from the combustion heats the fuel from the cryogenic fuel tank, which can then be burned, thereby generating heat to continue the cycle. This is a very convenient way to operate a modified gas turbine engine using cryogenic fuels.

[0005] However, the inventors have established an improved arrangement for heat recovery which can be conveniently used and which protects the heat exchanger from any debris that may leave the engine due to malfunction or foreign object ingestion. The invention described herein also minimizes any performance loss that may be caused by recovering heat from the engine. Thus, an alternative fuel system and associated engine architecture have been achieved.

[0006] The invention described herein is particularly advantageously applied to aircraft engine designs used with unconventional fuels, such as fuels that are stored at cryogenic temperatures and must be heated in order to burn efficiently. Most notably, the invention described herein is advantageous for gas turbine engines configured to operate using cryogenic fuels, such as liquid hydrogen. Summary of the invention

[0007] Various aspects of the invention are set out in the accompanying claims.

[0008] Viewed from a first aspect, there is provided an aircraft fluid heating arrangement comprising an exhaust cone for a gas turbine engine, the exhaust cone having an outer body defining an inner cone cavity, the inner cone cavity including one or more conduits therethrough for conveying fluid through the cavity, and wherein the outer body of the exhaust cone includes at least one inlet and at least one outlet for allowing exhaust gas to enter, pass through and exit the exhaust cone.

[0009] Thus, according to the arrangement described herein, hot exhaust gases normally leaving a gas turbine engine may instead be used to heat a fluid using heat recovery in a heat exchanger.Unconventionally, a portion of the exhaust cone is used to house such a heat exchange arrangement at the rear of the engine to recover heat that would otherwise be lost.

[0010] Advantageously, the fluid may be a fuel, such as, in one example, a subcooled cryogenic fuel, which in turn may be used as a fuel for the engine.

[0011] For example, liquid hydrogen can be used in cryogenic form. Also, liquid methane or LNG or liquid ammonia can be used according to the invention described herein.

[0012] The fluid inlet and fluid outlet may be provided at suitable locations on the conduit, allowing fluid to be transferred to and from the conduit within the cavity. The inlet may be in communication with a fuel tank, and the outlet may be in communication with a fuel or fluid delivery system of the engine.

[0013] The one or more conduits may be arranged so that the fluid fuel flows in a generally alternating direction between the front and rear of the cone (front and rear sides) in the direction of exhaust gas flow. This advantageously maximizes the fluid path length and increases the heat transfer capacity of the conduit by heat transfer through the conduit wall.

[0014] The one or more conduits may be in the form of a generally cylindrical heat exchanger having a plurality of conduits extending between the front and rear of the cavity and defining one or more fuel fluid flow paths within the cavity. Such a cross section advantageously fits within the cone of the engine and optimizes space usage and thereby efficiency.

[0015] The volume of exhaust gas flowing through the exhaust cone and over the duct may be predetermined, and one or more inlets and / or one or more outlets selected to allow a predetermined percentage or volume of exhaust gas to pass through the cone. The predetermined volume of gas may be established, for example, to optimize heat transfer for a given engine at cruising speed and altitude.

[0016] Alternatively, the volume may be selectively controlled (to control the exhaust flow volume), such as by a controllable orifice / door / movable vane, etc., thereby controlling the heating effect of the exhaust gas passing through the cone by controlling the volume of exhaust gas directed through the cone from the exhaust port. Controlling the volume of exhaust gas passing through the cone allows fine control and adjustment of heat transfer to the duct under different flight / glide and operating conditions. This may avoid excessively high and low fluid or fuel temperatures. For example, a suitable control feedback arrangement may be provided to control the exhaust volume flow rate in response to the fluid / fuel temperature.

[0017] The spacing between adjacent one or more conduits may increase towards the central axis of the heating arrangement. Thus, the density of conduits towards the central axis of the arrangement decreases. Specifically, the matrix should be dense at the outer radius and more sparse towards the center. This will limit the flow rate and pressure drop towards the center of the heat exchanger.

[0018] The conduit may be arranged parallel to the axis of the heating arrangement. Advantageously, the conduit or duct will extend helically from the interior (cold fuel or fluid and cold exhaust gas) to the exterior (hot fuel and hot exhaust gas).

[0019] The conduits may advantageously be divided into a plurality of discrete groups, each group forming a subset or module of the main body of the heating arrangement. In practice, the heating arrangement may be divided into cylindrical segments, each segment being similar or identical. Advantageously, the modules may each be axially positioned into the heating arrangement and removable for maintenance etc. In practice, each module may be selectively removable from the heating arrangement.

[0020] One, a subset or all of the modules may be fluidly interconnected to adjacent modules at one or both ends of the module. Thus, selective flow lengths may be provided, or alternatively, the longest flow length path may be created by interconnecting the modules.

[0021] Hot exhaust gas can be delivered to the heating arrangement in various ways (i.e. directed from an engine exhaust port). For example, at least one inlet may be in the form of one or more annular circumferentially extending inlets arranged to deliver exhaust gas from an associated engine exhaust port into the cavity in use. Thus, gas may be conveniently received uniformly around the heating arrangement and uniformly distributed therein.

[0022] The outlet of the cavity may be axially located relative to the axis of rotation of the exhaust cone to allow gases to exit the cone and the engine along the axis of travel of the engine.

[0023] The cavity itself may include a plurality of duct supports / baffles extending across a portion of the cross-sectional area of ​​the exhaust cone and including a plurality of apertures arranged to receive and support the associated ducts. Thus, the ducts may be supported to provide mechanical strength during flight and operation. The baffles may advantageously allow for thermal expansion of the ducts.

[0024] The supports / baffles may, for example, be spaced apart along the length of the cavity from the exhaust inlet to the exhaust outlet. In addition, the supports / baffles may have an outer radius that increases toward the exhaust outlet. Increasing the outer radius of successive baffles allows for providing airflow control, specifically, the exhaust gas may be divided into a plurality of channels, each channel having exhaust gas collected by a baffle.

[0025] The support members / baffles may each have a generally frustoconical shape and include a central open end for conveying exhaust gas toward an exhaust port of the tail cone. In addition, each generally frustoconical side may include a concave curved profile when viewed in cross section. Such a profile advantageously optimizes airflow over the duct toward the outlet.

[0026] The pipes or conduits described herein can be assembled into multiple individual modules, each module containing one or more tube groups for fluid or fuel, wherein each group consists of a series of tubes, each tube positioned at a specific radius from the inner radius to the outer radius of the heat exchanger. The above groups can be arranged so that the tubes are connected together by U-shaped bends at either end to form a continuous path for the fluid or fuel. The radial positioning of corresponding tubes in adjacent modules can be replicated to provide a uniform heat exchange arrangement with multiple modules.

[0027] The groups or modules may each be arranged in a generally segment or wedge shape when viewed along the axis of rotation of the engine.

[0028] The heating arrangement may be configured as a pair of heat exchangers with a main heat exchanger that transfers heat to the fuel for consumption in the engine. The main heat exchanger may receive fuel from a fuel tank or container and transfer the fuel to the engine. This may be located within the engine cowling, within the aircraft fuselage, or near the fuel tank.

[0029] The heat exchange arrangement within the cone may then act as a secondary heat exchanger, with the fluid flowing through the secondary heat exchanger to the primary heat exchanger.

[0030] Thus, the fuel can advantageously be heated by the heat received from the one or more conduits passing through the exhaust cone. The fluid circulates through the secondary heat exchanger and collects heat from the exhaust gas. The fluid then circulates through the primary heat exchanger, at which time the heat from the fluid is exchanged to the fuel and the fuel is then delivered to the engine.

[0031] Advantageously, in this arrangement, the fuel itself is not conveyed through the duct in the exhaust cone, but circulates through the main heat exchanger. This arrangement reduces the risk of fuel leakage within the exhaust cone. The fluid within the duct of the exhaust cone may advantageously be any suitable inert fluid, such as, but not limited to, liquid metal, helium, nitrogen, water or carbon dioxide.

[0032] Such an arrangement further reduces the risk of ice formation in the heat exchange conduits and prevents fire or hazards if the conduits are damaged.

[0033] From another aspect, a cryogenic fuel or fluid heating arrangement for a gas turbine engine is provided, the arrangement comprising a heat exchange device contained within an exhaust tail cone of the gas turbine engine, the exhaust tail cone having an outer body defining an inner cone cavity, the inner cone cavity comprising a heat exchanger in fluid communication with a cryogenic fuel tank or a fluid fuel tank and an engine fuel or fluid system, wherein the outer body of the exhaust cone comprises at least one inlet and at least one outlet to allow engine exhaust to pass through the heat exchange device, thereby transferring energy from the exhaust gas to the cryogenic fuel.

[0034] Advantageously, the volume of the exhaust gas flow may be selectively controlled in response to a control signal from the control device.Thereby, heat transfer control may be provided.

[0035] The cryogenic fuel fluid may be a variety of fuels including, for example, liquid hydrogen.

[0036] Viewed from a further aspect, there is provided a method of heating fuel or fluid for a gas turbine engine, the engine comprising a fuel or fluid heating arrangement, the fuel or fluid heating arrangement comprising an exhaust cone for a gas turbine engine, the exhaust cone having an outer body defining an inner cone cavity, the inner cone cavity including one or more conduits therethrough for conveying fuel or fluid through the cavity, and wherein the outer body of the exhaust cone includes at least one inlet and at least one outlet for allowing exhaust gas to enter, pass through and exit the exhaust cone, the method comprising the steps of:

[0037] (a) passing fuel or fluid from a fuel or fluid source into the conduit;

[0038] (b) passing exhaust gas from the engine through the exhaust cone and around the conduit to transfer heat to the fuel or fluid contained therein; and

[0039] (c) delivering the heated fuel or fluid to the gas turbine engine.

[0040] From another perspective, it provides:

[0041] • An aircraft engine comprising a fuel or fluid heating arrangement or a cryogenic fuel or fluid heating arrangement as described herein.

[0042] • an aircraft comprising one or more engines comprising a fluid or fuel heating arrangement or a cryogenic fuel or fluid heating arrangement as described herein; and

[0043] • A vehicle or power generation apparatus comprising a fuel or fluid heating arrangement or a cryogenic fuel or fluid heating arrangement as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Various aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0045] Figure 1 A conventional tail cone of a gas turbine engine is shown;

[0046] Figure 2 A cross section through a conventional gas turbine engine is shown showing the location of the exhaust cone and associated exhaust nozzles;

[0047] Figure 3 shows a cross section through an arrangement described herein;

[0048] Figure 4 shows a cross section through an arrangement described herein having exhaust gas flow and exhaust gas inlet ports;

[0049] Figure 5 shows a cross section through a cone as described herein, showing exhaust gas flow;

[0050] Fig. 6A and Figure 6B An alternative baffle arrangement is shown;

[0051] Figure 7A to Fig. 7E shows the arrangement of conduits within the conical cavity forming the heat exchange device;

[0052] FIG. 8A to FIG. 8E shows a support or baffle positioned with an exhaust cone of the arrangement described herein;

[0053] Figure 9A and Fig. 9B Conduit assignments and end connections are shown; and

[0054] FIG. 10A to FIG. 10D A catheter module arrangement is shown.

[0055] Although the present invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are described in detail herein. However, it should be understood that the drawings and the accompanying detailed description are not intended to limit the invention to the particular forms disclosed, but are intended to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention.

[0056] Any reference to prior art documents in this specification should not be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the art. As used in this specification, the words "comprise", "comprising" and similar words should not be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including but not limited to". The present invention is further described with reference to the following examples. It should be understood that the claimed invention is not intended to be limited by these embodiments in any way. It will also be appreciated that the present invention covers not only individual embodiments but also combinations of the embodiments described herein.

[0057] The various embodiments described herein are presented only to help understand and teach the claimed features. These embodiments are provided only as representative samples of embodiments and are not exhaustive and / or exclusive. It should be understood that the advantages, embodiments, examples, functions, features, structures and / or other aspects described herein should not be considered as limitations on the scope of the invention defined by the claims or limitations on the equivalents of the claims, and other embodiments may be utilized and may be modified without departing from the spirit and scope of the claimed invention. In addition to those specifically described herein, various embodiments of the present invention may appropriately include appropriate combinations of disclosed elements, components, features, parts, steps, devices, etc., and may be composed of or substantially composed of appropriate combinations of disclosed elements, components, features, parts, steps, devices, etc. In addition, the present disclosure may include other inventions that are not currently claimed but may be claimed in the future.

[0058] It will be appreciated that features of the various aspects of the invention described herein may be used advantageously and interchangeably in any appropriate combination. DETAILED DESCRIPTION

[0059] Figure 1 There is shown a general view of a gas turbine engine 1 looking forwards (ie towards the direction of flight) from the rear of the engine. The rear of the engine comprises a tapered exhaust cone 2 which provides an aerodynamic final profile to the tail or rear end of the engine.

[0060] The engine core exhaust flows out of the annular outlet 3 of the engine to combine with the fan airflow exhaust 4 to produce engine thrust. The engine exhaust cone 2 serves primarily as an aerodynamic component of the engine.

[0061] Figure 2 A cross section of an example gas turbine engine is shown. As shown, the exhaust cone 2 is located at the rear (rear) of the engine and is surrounded by an annular core exhaust 3. This flow is the exhaust leaving the combustor. Radially outward of the core exhaust 3 is the annular fan airflow exhaust 4.

[0062] Gas turbine inlet, compressor and combustor (such as Figure 2 The function of the exhaust cone (shown in cross section in FIG. 1 ) will be well understood by those skilled in the art and will not be discussed in detail. The invention described herein relates to an exhaust cone and a novel fuel management system.

[0063] Figure 2 The general flow is shown around the exhaust cone, which is smooth and tapered to reduce drag and vortices propagating from the rear of the engine. The exhaust cone thus presents a smooth and aerodynamic outer surface. The exhaust cone is usually sealed so as not to cause any drag, but may incorporate a small outlet to allow gases to escape from the main shaft bearing 5 located along the axis of the engine.

[0064] As shown, the exhaust cone is located at the rear end of the engine and therefore it is desirable to minimize the weight of the cone in order to reduce overall engine weight and reduce the moments or turning forces that the weight at the rear of the engine may induce on the engine and engine mounts.

[0065] Figure 3 A cross section of the exhaust cone is shown. The cone 2 is mechanically coupled to the turbine exhaust casing (TEC) which is a structural part of the engine. Also attached to the TEC is the core exhaust nozzle 3 which is an annular and circumferentially positioned ring around the engine which allows the exhaust gas to be accelerated rearwardly as will be understood in the art.

[0066] The cone can be coupled to the TEC in a variety of ways. For example, the first baffle or left wall of the heat exchanger compartment can be connected to the rear inner flange of the TEC. The cone can then be attached to the baffle using radial struts extending outward from the first baffle. The other baffles can then be attached with similar radial struts extending inward from the cone to each baffle. The tubes are then suspended from the baffles, but there can be some axial relative movement at least at some of the baffle / tube intersections to limit the buildup of thermal stresses.

[0067] An alternative is to provide a split flow path for the TEC, i.e., place a cylinder (concentric with the engine axis) somewhere between the hub and the tip of the TEC struts, dividing them into inner and outer parts. This splitter can then extend rearward from the TEC struts, and the cone can be fixed directly to this strut. For the previous solution, radial struts from the cone can be used to suspend the baffle and indirectly the heat exchanger.

[0068] Yet another alternative is to suspend the cone by radial struts from the outer nozzle. This effectively creates a second TEC with some associated weight and pressure drop, and may not be preferred. Unless the nozzle is made longer with no or minimal acceleration at the front, the pressure drop can be significant as the gas accelerates rapidly in the nozzle.

[0069] As shown, the exhaust tail cone extends rearwardly from the TEC and defines a smooth outer aerodynamic surface against which exhaust gas may flow and which is adapted to enclose a heat exchanger.

[0070] like Figure 3 As shown in cross-section in FIG, the outer surface of the exhaust cone defines the outer geometry of the cone and encloses an inner volume or cavity 6.

[0071] According to the non-conventional exhaust tail cone arrangement described herein, the duct arrangement is located within the volume or cavity 6 as described below.

[0072] like Figure 3 As shown, a heat exchange conduit 7 is located within the cavity 6 according to an embodiment of the invention described herein. As described below, the conduit 7 can be in a variety of different configurations. One or more heat exchange conduits are configured to be received within the cavity 6.

[0073] Also like Figure 3 As shown, the cavity includes an inlet 8 and an outlet 9. The inlet 8 may be an annular inlet in communication with the exhaust nozzle to allow exhaust gas from the exhaust nozzle to enter the cavity 6 through the inlet 8. Alternatively, it may be a plurality of discrete inlets positioned around the periphery of the cone or a single annular inlet that allows exhaust gas to enter the cone. In each configuration, the purpose of the one or more inlets is to allow exhaust gas discharged from the nozzle to enter the cavity of the exhaust cone.

[0074] The one or more ducts can be arranged in the cavity 6 in any suitable configuration. In one arrangement, the one or more ducts are arranged to receive fuel (or fluid) for the gas turbine engine and allow heat from the exhaust gas circulating around or through the cavity to be transferred from the exhaust gas to the fuel through the walls of the one or more ducts. In practice, the exhaust gas heat exchanger is disposed within the exhaust tail cone of the gas turbine engine.

[0075] Thus, the fuel or another fluid may be heated to a temperature T 1 enters the conduit / heat exchanger and at a second elevated temperature T 2 Next exit conduit / heat exchanger, where T 2 >T 1Thus, in an arrangement where a cryogenic fuel is to be used to fuel a gas turbine, the cold cryogenic fuel may be raised in temperature by means of the tail cone heating arrangement described herein. The fuel may be delivered from the cryogenic fuel tank to a duct in the exhaust tail cone. Heat from the exhaust gas that would normally be exhausted from the engine to the atmosphere may be recycled and used to raise the temperature of the cryogenic fuel. Specifically, engine cycle performance may be improved by recovering heat from the exhaust gas, which will provide lower specific fuel consumption.

[0076] As described herein, the fuel may be conveyed through a conduit or fluid, which in turn may be used to transfer heat to the fuel, for example, through a second heat exchanger as described herein.

[0077] The fuel or other fluid may be a variety of fuels including but not limited to (compressed) air, water, steam, another inert gas or fluid such as helium, nitrogen, oxygen-depleted air, refrigerant, carbon dioxide or silicone oil at cryogenic or higher temperatures depending on storage and preheating in another heat exchanger. The inert medium may be used to indirectly heat the fuel or to be used in a power generation cycle, separate from or interconnected to the main engine.

[0078] This feature will be particularly useful if other fuels are used that are not based on hydrocarbons (or intermediate fluids). Using hydrogen as jet fuel will most likely be in a cryogenic state, which will reduce the size of the fuel tank and enable pumps to be used to transport the fuel. Since hydrogen can be heated without forming deposits, recovering heat from the exhaust will improve cycle performance, which will reduce the fuel consumption of the engine.

[0079] Advantageously positioning the ducts forming the heat exchange arrangement within the tail cone protects the ducts from any debris, particles, ice or (in extreme cases) engine components passing through the engine. In addition, the normally unused volume of the cone can conveniently accommodate the heat exchanger described herein.

[0080] Also like Figure 3 As shown, the plurality of ducts may be arranged as a group of tube bundles extending along a cone substantially parallel to the axis of the engine and alternating back and forth with U-shaped flex joints at either end. This maximizes the length of the duct, thereby also maximizing the area for heat transfer by increasing the "wetted" surface (i.e., the surface that the hot exhaust will contact and impinge on). Any suitable configuration of ducts may be used, depending on the desired heat transfer capacity, exhaust temperature, tail cone length, required temperature difference between the duct inlet and outlet, and other factors.

[0081] As shown, the outlet 9 is positioned at the rear of the tail cone along the central axis of the engine. This thereby minimises turbulence as the gases leave the exhaust cone to mix with other exhaust and ambient gases.

[0082] Thus, exhaust gas may enter the exhaust cone through inlet 8, thermally interact with the conduit, transferring heat thereto, and then exit the cone through outlet 9. The contents of the conduit (e.g., fuel or a heat transfer fluid) may similarly enter the conduit from a fuel reservoir / tank, thermally interact with the exhaust gas and increase in temperature, and then be delivered to the engine.

[0083] Figure 4 The general flow of exhaust gas in one embodiment of the invention described herein is shown.

[0084] The inventors have determined that improving engine cycle efficiency by recovering heat from the exhaust gas has a performance penalty in terms of pressure losses caused by the heat exchanger. Since the total heat flow in the exhaust gas is several orders of magnitude higher than the energy recovered by the heat exchange arrangement 7, only a portion of the core flow needs to be used as a heat source in the heat exchange arrangement. In addition, the amount of heat required to heat the fuel by a desired amount can vary depending on the operating and ambient temperature.

[0085] Therefore, only a portion of the core flow will experience performance losses from the heat transfer process.The problem of excessive pressure drop can be solved by introducing a flow splitter to divert a portion of the core flow.

[0086] It has been determined that this is particularly useful when liquid hydrogen is used as a fuel. Since this fluid will be stored at cryogenic temperatures, it is necessary to heat the fluid to mitigate the risks associated with condensation and ice formation on the exterior of the fuel system, as it is impossible to predict the extent or form of the ice volume produced.

[0087] Thus, the exhaust flow through the heat exchange or heat transfer arrangement can advantageously be controlled or throttled to allow desired heat transfer conditions within the tail cone cavity. Flow into and out of the cavity can be achieved by controlling the inlet via a suitable valve arrangement or similarly controlling the outlet via a suitable outlet valve arrangement. A combination of the two can also be used. Suitable valve arrangements are not described herein, but will be understood by those skilled in the art.

[0088] In such an arrangement, suitable temperature sensors sensing the temperature of the fuel and / or exhaust gas may be used in conjunction with a suitable control arrangement to control valves and fuel flow to achieve the desired fuel temperature prior to supply to the engine. The recirculation flow may also be used to recirculate the fuel to achieve a higher temperature and avoid ice formation. This may be achieved by any suitable fluid control arrangement.

[0089] Also like Figure 4As shown, the airflow itself can be subdivided within the cavity to evenly distribute the flow in the heat exchanger matrix in order to minimize pressure drop and maximize heat transfer. As shown, the airflow can be divided into 3 separate flows FL1, FL2 and FL3. However, any suitable number of flows can be provided. For example, too much division leads to higher weight and pressure drop, while too little division leads to more uneven flow and higher pressure drop. The number is optimized for the engine operating conditions.

[0090] The exhaust flows generally radially inwards and then axially outwards from the cone through outlet 9. Three exhaust flows FL1, FL2 and FL3 are formed by splitting the main exhaust flow into three separate flows from inlet 8. This is achieved by sub-apertures A1, A2 and A3 associated with FL1, FL2 and FL3 respectively.

[0091] Sub-apertures A1, A2 and A3 may be annular openings that allow exhaust gas from inlet 8 to be conveniently captured and directed through flow directions FL1, FL2 and FL3 and over the heat transfer conduits. Figure 4 As shown, the sub-apertures may each be radially staggered to evenly distribute or share the inlet exhaust gas from the inlet 8 .

[0092] Figure 5 The total airflow through the exhaust cone fuel heating arrangement is shown. As shown, the exhaust leaves the combustor and approaches the exhaust cone. A portion of the exhaust is then exhausted at a fixed volume or selectively in response to the desired heating within the exhaust cone. For example, at takeoff or engine start, it may be desirable to have a larger proportion of the heat go into the cone. Similarly, in extremely cold conditions, it may be desirable to increase the amount of cone heating. Conversely, in hot conditions or in cruise conditions, it may be desirable to control the exhaust flow into the cavity.

[0093] like Figure 5 As shown, the gas is divided into multiple streams passing through the heat exchanger, such as Figure 5 As shown in the figure, each flow path is controlled by upstream and downstream baffles to direct the airflow through the heat exchanger and out the back of the cone. The baffles are used to control the airflow and then restore the axial airflow from the back of the cone, as shown by the airflow arrows.

[0094] Therefore, a feedback control arrangement may be provided to accurately manage the engine fuel inlet temperature by selectively:

[0095] (a) controlling the amount of exhaust gas flowing into and out of the exhaust cone; and / or

[0096] (b) Optionally, recirculating the flow to increase the temperature of the conduit.

[0097] like Figure 5As shown, according to one embodiment of the invention described herein, exhaust gas passes through the exhaust cone and exits the cone axially at the rear of the engine.

[0098] Fig. 6A and Figure 6B An alternative configuration of the heat exchanger and in particular the air flow control is shown.

[0099] Fig. 6A An inlet 66 is included for the exhaust gas flow from the engine. The inlet air flow is then divided into 2 flows: a first boundary layer flow 67 and a second main flow 68 of the exhaust gas passing along the surface of the engine outlet. Fig. 6A The arrows shown in illustratively show how the two streams pass through the heat exchanger.

[0100] First stream 66 is directed quickly toward the center of heat exchange and toward the outlet of heat exchanger. On the contrary, main stream 68 is divided into multiple streams, and each stream flows through different longitudinal parts of heat exchanger. As shown in the figure, these streams are separated and controlled by the relative radial range of orifice.

[0101] Fig. 6A Also shown is a flow guide 69 which acts as a discharge diffuser to direct the gas toward the far end and final orifice of the heat exchanger. The discharge diffuser has the effect of reducing velocity, but provides significant flow losses due to the lost kinetic energy creating turbulence and then heat, rather than being available as more valuable mechanical energy. In addition, the discharge diffuser can provide uniform distribution between the heat exchanger sections. Although it may incur a small loss in performance, it advantageously ensures uniform distribution between sections.

[0102] Figure 6B A similar configuration is shown including a flow guide 69, but in this example the duct is inclined relative to the axis of rotation of the engine.

[0103] Advantageously, this arrangement may provide additional advantages, including:

[0104] • Minor diversion of flow into and out of the heat exchanger;

[0105] •More space centrally towards the right where flow increases (supplied by all sections of the heat exchanger);

[0106] •Reduction of velocity / flow losses;

[0107] • Increase the radial space in the outer space towards the left end (where the flow is larger); and

[0108] • Increased center space available for heat exchanger tubes toward the left end (and increase in heat transfer capacity).

[0109] In addition, as the flow leaves the heat exchanger matrix, the flow area in the center of the flow increases. As more gas from different sections joins the flow in the center, the flow area is advantageously increased to keep the velocity low. This achieves a more favorable flow angle with the tubes without having to turn the flow inwards 90°.

[0110] It will be appreciated that the invention described herein is not limited to purely axial arrangements of tubes or to a precisely cylindrical heat exchanger matrix.

[0111] Figure 7A to Fig. 7E One configuration of a heat transfer arrangement contained within an exhaust cone cavity according to the invention described herein is shown.

[0112] FIG7A shows an end view and a side view of an exhaust cone containing a plurality of heat transfer conduits or pipes. End 10 shows the upstream end of the heat transfer arrangement, i.e., from Figure 4 The inlet 8 shown in FIG. 1 receives the exhaust gas, and the end 11 shows the downstream end of the heat transfer arrangement, that is, the exhaust gas is discharged to Figure 4 The end of the outlet 9 is shown in FIG.

[0113] As shown, the tubes are bundled to form a closely packed heat exchange matrix within the cone cavity. Fig. 7E It will be appreciated that the various conduits are spaced apart from one another to allow exhaust gas to circulate around their surfaces, thereby allowing heat transfer.

[0114] As shown in Figure 7A to Fig. 7E As shown, importantly, the conduits are closely aligned in order to (a) reduce the overall size of the heat exchange arrangement, and (b) reduce the overall weight distribution of the heat exchange arrangement.

[0115] Specifically, one embodiment described herein includes a Fig. 7E The duct arrangement of the tube design shown, wherein the tube has a high heat transfer coefficient. This advantageously minimizes weight and size while meeting the performance goals of the desired heat transfer.

[0116] FIG7B shows a bundle or matrix of heat exchange conduits. Advantageously, the bundle can be located in an exhaust cone in a single unit, thereby facilitating manufacturing and / or maintenance. As shown, the individual conduits forming the heat exchange arrangement are configured in a generally spiral shape, as shown in FIG7A and FIG7B.

[0117] The helical or spiral arrangement of the conduits of the matrix may provide a number of advantages, including:

[0118] (i) Multi-channel counter-cross flow heat exchangers for optimal heat transfer,

[0119] (ii) easy connection of pipe segments; and

[0120] (iii) enabling the pressure loss of the fluid to be heated to achieve a sufficiently high value, which is preferred to avoid misdistribution.

[0121] Figure 7A to Fig. 7E The advantage of the proposed solution shown in is the recovery of energy supplied to the fuel system. This will have a positive impact on the engine cycle efficiency.

[0122] The arrangement shown in Figures 7A to 7E is formed from a plurality of individual catheter bundles or units which together form a cylindrical matrix as shown in Figure 7B. Figure 7C As shown, the matrix is ​​formed by a plurality of individual groups. These groups extend in a curve as shown in the boxed area of ​​Figure 7A, where the conduit subgroup of 7C is located. As shown, the subgroup 7C is curved radially inwardly, which minimizes the overall size of the heat exchange arrangement.

[0123] Figure 7D shows the composition of a subset 7C in the form of a pair of curved and reciprocating conduits; each conduit in the form of a series of straight sections and U-shaped bent end sections forming a tube or conduit in a serpentine or "back and forth" configuration as shown in Figure 7D.

[0124] The straight section of the duct may be configured to extend generally toward the rear of the engine (ie, from the front to the rear of the tail cone). This may maximize the length of the duct within the cone cavity volume.

[0125] Advantageously, the duct may also be configured as a spiral or swirl from inlet to outlet. As the exhaust gas leaves the engine turbine, the exhaust gas passing through the tail cone will include a swirl or rotational component. Angling the duct to complement the rotation or swirl of the exhaust gas further prevents debris damage.

[0126] The conduits may be supported by a plurality of brackets or supports 12 (which may be baffles) that maintain spacing between adjacent conduits to allow exhaust gas flow. The supports may be configured to allow axial movement of the conduits to accommodate thermal expansion of the conduits during operation. This is particularly relevant to longer lengths of conduits, where thermal expansion may be more significant.

[0127] FIG. 7D shows Figure 7C A layer of catheter is shown in . Fig. 7E An enlarged end of this layer is shown. As shown in FIG7D , this particular arrangement of conduits is in the form of a single length of conduit with multiple U-shaped bends or 180 degree turns at either end. Their function is to change the direction of the fuel within the conduit, which in turn increases the length of the overall flow path of the fuel within the hot exhaust environment created within the tail cone cavity 6. Thus, heat transfer and fuel heating can be optimized.

[0128] The diameter of the tube is primarily chosen so that the area fits into a small volume. Therefore, smaller diameter tubes are better, but are limited by mechanical and manufacturing issues. For example, a 6 mm tube can be used in one example. A smaller diameter, such as a 3 mm diameter tube, can also be used.

[0129] like Fig. 7E As shown, a fluid such as hydrogen fuel is received from a fluid or fuel supply source (e.g., a cryogenic fuel tank) and delivered to one end of the conduit ( Fig. 7E H2 inlet), then Fig. 7E The other end of the conduit is received from the H2 outlet for delivery to the fuel delivery system of the aircraft engine.

[0130] The U-shaped flex sections may advantageously allow replacement of individual lengths or groups of conduits as part of general maintenance or repair.

[0131] FIG. 8A to FIG. 8E Another embodiment of the present invention described herein is shown. Specifically, FIG. 8A to FIG. 8E Duct support elements 13A, 13B, 13C and 13D are shown spaced axially along the exhaust cone cavity 6 .

[0132] Despite Fig. 8A and Figure 8B In the example shown in FIG. 4 , four support elements 13A to 13D are shown, but it will be appreciated that any suitable number of support elements may be used.

[0133] With a heat exchanger arranged and mounted in a tail cone as described herein, there is a need for structural support, adding damping to the system, and ensuring exhaust flow distribution so that as much area as possible is "active" in the heat exchanger.

[0134] This design element will provide structural support, enabling vibration damping. It will also simplify the assembly process as well as serve to direct the flow in the heat exchanger so that there are no ineffective "dead zones" in the heat exchanger.

[0135] In the example shown, the support or baffle elements 13A to 13D are designed to accommodate the helical arrangement of the conduits (eg Fig. 8E Thus, each conduit is secured by each baffle while allowing for thermal expansion.

[0136] Baffles can prevent tube vibrations which represent a durability problem. Flow rates in heat exchangers can be relatively low (e.g. 30 m / s). Tube vibrations lead to fatigue of the tubes and supporting elements and should therefore be avoided. Conventional tubular heat exchangers have wires or metal laths passing through the tube rows to ensure a constant distance between the tubes and reduce vibrations.

[0137] Each support or baffle 13A to 13D serves to direct the exhaust gas so as to flow evenly through the duct or tube bundle. An even flow distribution will result in a heat exchanger with minimum weight and highest compactness (minimum geometric envelope required). Compactness is necessary to eliminate / minimize impact on other components of the engine system which would otherwise require significant design changes to the nacelle (tail cone).

[0138] The baffle design will also provide (among other benefits):

[0139] Structural support for the spiral conduit of the heat exchanger;

[0140] Damping of spiral heat exchanger components;

[0141] Simplify the assembly process; and

[0142] Enables prefabrication of integral pipe sections (e.g., bends and other features).

[0143] 8C and 8D show a curved support member 14, which is formed as follows. Fig. 8E The generally curved or spiral form shown in the end view in Figure 1 holds the conduits in place. As shown, the spacing of the conduits is achieved by incrementally increasing the thickness of the support member from t1 to t2.

[0144] Fig. 8E A single support is shown with dotted lines indicating the location of the corresponding conduits.It will be appreciated that the spiral configuration maximises the density of conduits for a given cross-sectional area whilst maintaining spacing between conduits to allow for exhaust gas circulation.

[0145] Back to Fig. 8A , which shows how the main exhaust gas flow from the inlet 8 into the chamber 6 is subdivided or divided by supports or baffles 13A to 13D.

[0146] As shown, each baffle from 13A to 13D has a slightly larger outer diameter within the chamber, with 13A having the smallest outer diameter and defining an inlet radius 11. The last baffle 13D has the largest diameter and defines an inlet radius 14.

[0147] The intermediate baffles have correspondingly increased outer diameters and increased inlet radii I2 and I3, respectively. Thus, the inlet exhaust can be evenly distributed over the length of the heat exchanger to optimize efficiency.

[0148] from FIG. 8A to FIG. 8E It will be appreciated that the exhaust gas can be effectively introduced into the tail cone cavity and controlled to optimize flow along and around the ducts forming the heat exchanger. The exhaust gas can then conveniently exit the cavity in an axial direction through the outlet 9, thereby exiting the engine and mixing with the thrust and other exhaust gas exiting the rear of the engine.

[0149] Figure 9A and Fig. 9B The conduit interconnections at either end of the heat exchanger conduit assembly are shown. The heat exchanger tube is actually a continuous path for the fuel fluid flow to reciprocate in directions toward the rear and front of the heat exchanger. At either end, a 180 degree turn in the direction of fluid flow is required, which can be achieved by a U-shaped bend as shown in Figure 9A.

[0150] like Fig. 8E As shown, the tubes may be arranged in a generally helical configuration.

[0151] The conduit U-bends at either end of the assembly are configured to achieve optimal functionality of the tubes, i.e., the pipes or conduits are connected in series along a spiral. This is achieved by connecting the tube from the innermost tube to the spiral, then connecting the second to innermost tube, etc. to the outermost tube; the fluid or fuel flows back and forth along the corresponding tubes of the heat exchanger from the innermost tube to the outermost tube (or vice versa). This is accomplished by Fig. 9B The tubes in FIG. 1 are shown by dashed lines, which correspond to the arrangement structure in FIG. 9A .

[0152] However, all tubes with the same position along any spiral have the same function (temperature and flow direction) as the tubes on any other spiral. To make a more compact "module", it is therefore possible to connect, for example, tube 1 on spiral A to tube 2 on spiral B, which in turn is connected to tube 3 on spiral C, and so on. This refers to FIG. 10A to FIG. 10D In practice, a modular arrangement of heat exchanger tubes can be provided which has many advantages.

[0153] An advantage of compact modules is that they can be manufactured one by one and then assembled. In addition, the modules can be handled individually if inspection, testing and repair are required. Structural modules can be made stronger and more rigid by holding them together with more compact baffles.

[0154] according to FIG. 10A to FIG. 10D The modified arrangement in the embodiment of the invention can maintain the thermodynamic function of the arrangement and the efficiency (heat transfer, weight, pressure loss) remains unchanged. (Some tube bends have become slightly longer, but this has only a minor effect on weight and pressure loss).

[0155] Note that because each module is narrower at the inner radius, there are usually only one or two tubes connected along the spiral before stepping to the next. Near the outer radius, there are more tubes connected along the spiral before the buckling reaches the next one. (The number of connections along the spiral before stepping to the next is calculated based on the number of spirals, the number of tubes per spiral, the spacing between tubes, and the spiral angle).

[0156] Fig. 10A and Fig. 10BThe general way in which the tubes are connected at either end is shown, as well as how a straight length of tube extends between either U-shaped bend at the end of a heat exchanger module. As shown, the module is tapered with 5 straight pipe connections at the outermost point and a single connection at the radially innermost point.

[0157] Fig. 10C and Fig. 10D This is an end view of a pair of modules. Back Fig. 9B , showing the end plate of the heat exchanger, with the corresponding FIG. 10A to FIG. 10D Module.

[0158] By dividing the heat exchanger into multiple modules, the heat exchanger can be divided into sections of the circumference of the heat exchanger. Each module can be connected to an adjacent (or other) module at one or both ends using one or more connectors. It will be appreciated that creating a heat exchanger using the modular arrangement described herein provides a number of advantages as described below. Figures 10A to 10D The arrangement shown in provides the best functionality where the tubes need to be connected in series along a spiral.

[0159] Specifically, the innermost tube goes on the spiral, then the second tube to the innermost tube, and so on to the outermost tube. However, all tubes with the same position along any spiral have the same function (temperature and flow direction) as tubes on any other spiral. To make a more compact "module", it is therefore possible to connect, for example, tube 1 on spiral A to tube 2 on spiral B, which is then connected to tube 3 on spiral C, and so on.

[0160] The advantage of compact modules is that they can be manufactured one by one and then assembled. In addition, if inspection, testing and repair are required, the modules can be handled individually. Structural modules can be made by combining them with more compact baffles, such as Fig. 9B shown) together to make it stronger and more rigid.

[0161] Since the thermodynamic functions of the alternatives are the same, the efficiency (heat transfer, weight, pressure losses) is unchanged. Some tube bends may become slightly longer, but the effect is minor.

[0162] As mentioned above, each module is advantageously an identical sector.

[0163] Also like FIG. 10A to FIG. 10DAs shown, the spacing of adjacent tubes forming each module can vary. For example, the center-to-center spacing of tubes toward the inner radius of the module (measured from the central axis of the heat exchanger) can be greater than the center-to-center spacing of adjacent tubes toward the outer radius of the module. In fact, an uneven distribution of tube spacing can be provided. More specifically, the matrix should be dense at the outer radius and more sparse toward the center. This will limit the flow rate as well as the pressure drop toward the center of the heat exchanger.

[0164] Thus, each module, and thus the heat exchanger as a whole, can be optimized in terms of performance for a specific application.

Claims

1. An aircraft fluid heating arrangement comprising an exhaust cone for a gas turbine engine, the exhaust cone having an outer body defining an inner cone cavity, the inner cone cavity including one or more conduits passing through the inner cone cavity for conveying a fluid through the cavity, and wherein: The outer body of the exhaust cone includes at least one inlet and at least one outlet to allow exhaust gas to enter, pass through and exit the exhaust cone.

2. The fluid heating arrangement of claim 1 further comprising a fluid inlet and a fluid outlet, the fluid inlet and fluid outlet allowing fluid to be delivered to and from the conduit within the cavity.

3. The fluid heating arrangement according to claim 1 or 2, wherein: The one or more conduits are arranged to cause fluid to flow in a generally alternating direction between a front portion and a rear portion of the cone in the direction of exhaust gas flow.

4. A fluid heating arrangement according to any one of the preceding claims, wherein: The one or more conduits are in the form of a generally cylindrical heat exchanger having a plurality of tubes extending between the front and rear portions of the cavity and defining one or more fluid flow paths within the cavity.

5. A fluid heating arrangement according to any one of the preceding claims, wherein: The spacing between adjacent tubes increases towards the central axis of the heat exchanger.

6. A fluid heating arrangement according to any one of the preceding claims, wherein: The conduits are divided into discrete groups, each group forming a subset or module of the main body of the heating arrangement.

7. The fluid heating arrangement according to claim 6, wherein: Subsets or modules may be selectively removable from the heating arrangement.

8. A fluid heating arrangement according to claim 6 or 7, wherein: The modules are fluidly interconnected to adjacent modules at one or both ends of the module.

9. A fluid heating arrangement according to any one of the preceding claims, wherein: The at least one inlet is in the form of one or more annular circumferentially extending inlets arranged, in use, to pass exhaust gas from an exhaust port of an associated engine into the cavity.

10. A fluid heating arrangement according to any preceding claim, wherein: The outlet of the cavity is axially located relative to the axis of rotation of the exhaust cone.

11. A fluid heating arrangement according to any one of the preceding claims, wherein: The cavity includes a plurality of conduit supports / baffles extending across a portion of the cross-sectional area of ​​the exhaust cone and including a plurality of apertures arranged to receive and support associated conduits.

12. The fluid heating arrangement of claim 11, wherein: Supports / baffles are spaced along the length of the chamber from the exhaust inlet to the exhaust outlet.

13. A fluid heating arrangement according to any one of claims 11 or 12, wherein: The support / baffle has an outer radius that increases toward the exhaust outlet.

14. A fluid heating arrangement according to any one of claims 11 to 13, wherein: The support members / baffles each have a generally frusto-conical shape and include a central open end for channeling exhaust gas toward an exhaust port of the tail cone.

15. The fluid heating arrangement of claim 14, wherein: Each generally frustoconical side includes a concavely curved profile when viewed in cross-section.

16. A heating arrangement according to any one of the preceding claims, wherein: The fluid is a fuel.

17. A heating arrangement according to any preceding claim, further comprising a main heat exchanger arranged to exchange heat between fuel used in the engine and a fluid arranged, in use, to flow through the plurality of conduits within the exhaust cone.

18. The heating arrangement according to claim 17, wherein: The main heat exchanger is arranged, in use, to be in fluid communication with a cryogenic fuel source and a fuel delivery system of the engine, and the plurality of conduits are arranged, in use, to exchange heat from the exhaust gas to a fluid contained within the conduits.

19. A heating arrangement according to any one of the preceding claims, wherein: The volume of exhaust gas flowing through the exhaust cone and over the conduit is predetermined, and the inlet and / or outlet are configured to allow a predetermined percentage or volume of exhaust gas to pass through the cone.

20. A heating arrangement according to any one of the preceding claims, wherein: The volume of exhaust gas flowing through the exhaust cone and over the conduit may be selectively controllable by one or more exhaust control arrangements arranged, in use, to control the entry or exit of exhaust gas into or out of the cone.

21. A cryogenic fuel heating arrangement for a gas turbine engine, the arrangement comprising a heat exchange device contained within an exhaust tail cone of the gas turbine engine, the exhaust tail cone having an outer body defining an inner cone cavity, the inner cone cavity including a heat exchanger in fluid communication with a cryogenic fuel tank and an engine fuel system, wherein: The outer body of the exhaust cone includes at least one inlet and at least one outlet to allow engine exhaust to pass through the heat exchange device to transfer energy from the exhaust to the cryogenic fuel.

22. A low temperature fuel heating arrangement for a gas turbine engine according to claim 21, wherein: The volume of the exhaust flow is selectively controlled in response to a control signal from a control device.

23. A low temperature fuel heating arrangement for a gas turbine engine according to claim 21 or 22, wherein: The cryogenic fuel is liquid hydrogen.

24. A method of heating fuel or fluid for a gas turbine engine, the engine comprising a fuel or fluid heating arrangement, the fuel or fluid heating arrangement comprising an exhaust cone for a gas turbine engine, the exhaust cone having an outer body defining an inner cone cavity, the inner cone cavity comprising one or more conduits passing through the inner cone cavity for conveying fuel or fluid through the cavity, and wherein: The outer body of the exhaust cone comprises at least one inlet and at least one outlet to allow exhaust gas to enter, pass through and leave the exhaust cone, the method comprising the steps of: (a) passing fuel or fluid from a fuel or fluid source into the conduit; (b) passing exhaust gas from the engine through the exhaust cone and around the conduit to transfer heat to the fuel or fluid contained in the conduit; and (c) delivering the heated fuel or fluid to the gas turbine engine.

25. The method according to claim 24, wherein: The fuel or fluid is cryogenic liquid hydrogen fuel.

26. An aircraft engine comprising a fuel or fluid heating arrangement according to any one of claims 1 to 20 or a cryogenic fuel or fluid heating arrangement according to any one of claims 21 to 24.

27. An aircraft comprising one or more engines including a fluid heating arrangement according to any one of claims 1 to 20 or a cryogenic fuel or fluid heating arrangement according to any one of claims 21 to 24.

28. A vehicle or power plant comprising a fuel or fluid heating arrangement according to any one of claims 1 to 20 or a low temperature fuel or fluid heating arrangement according to any one of claims 21 to 24.

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