Apparatus

Abstract

A thermal management system (TMS) 100 for an aircraft comprising an air inlet 310 which receives ambient air from an external environment, an air outlet (120, figure 1) providing fluid communication b

Description

Technical Field The present invention is concerned with thermal management systems and the configuration and arrangement of air provision and flow paths for propulsion systems within aircrafts. Thermal management systems (TMSs) and air delivery systems (ADSs) use air flow however modern systems use much less waste heat and air heat exchangers are often installed in the bypass stream of modern turbofan engines. Modern systems are often inclined in relation to the airflow and often located behind the propeller fan. Modern aircraft systems use standard propulsion arrangements (combustion via kerosene or the like) and have suitable air delivery mechanisms for thermal management. Alternative propulsion fuels are possible that are more environmentally friendly however use of such fuels leads to shortcomings in other aspects of the modern propulsion arrangements. Alternate fuel sources allow for alternate power sources. Fuel cells are an alternate power source that are able to generate power from fuel. A drawback with such alternate power sources are the resulting production of low grade waste heat. As such, there are different considerations for handling this low grade waste heat that are not present for systems that utilise standard power sources such as gas turbine engines. As used herein, low grade waste heat refers to heat released at low temperature. For example, where the temperature of the cooling air is significantly below the temperature of the coolant, this may be referred to as high grade waste heat as this has a high temperature differential and will lead to effective thermal energy transfer. With low grade waste heat, the temperature differential is low and therefore there is typically ineffective thermal energy transfer. The present invention provides a highly effective solution in particular for low grade waste heat conditions. Fuel cells also allow the use of cleaner fuels, though this is not a requirement of the present disclosure. Fuel cells allow the use of cryogenic fuels, though this is not a requirement of the present disclosure. The use of cryogenic fuel as the primary fuel source for an aircraft is an area of cutting-edge research; conventional fuel system architectures are not sufficient to deal with the new complexities involved. Cryogenic fuel in particular presents many advantages over contemporary fuels, not least that they are more environmentally-friendly. An example of a cleaner fuel that may be used with fuel cells is cryogenic hydrogen. The thermal management systems discussed herein provide great levels of cooling for 5 environmentally friendly fuel using propulsion arrangements. Therefore, the present disclosure renders more attractive partially electrically powered aircraft. The thermal management systems discussed herein may be used with any propulsive vehicle. Summary of the Invention Aspects of the invention are set out in the accompanying claims. In accordance with some embodiments described herein, there is provided a thermal management system for an aircraft comprising: an air inlet portion arranged to receive ambient air into the thermal management system from an external environment; an air outlet portion arranged to provide fluid communication between the thermal management system and an external environment; a flow path from the air inlet portion to the air outlet portion, wherein the flow path comprises at least one turn; an air manipulation portion arranged to provide controlled manipulation to an airflow in the flow path; a thermal exchanger arranged to provide thermal energy exchange with the airflow in the flow path; wherein the air manipulation portion is arranged to provide controlled turning of the airflow in the flow path around at least one turn of the flow path. The air manipulation portion may be arranged to provide enhanced flow of air at the inlet by entraining it with higher velocity jet. Examples are discussed and shown below. The present thermal management system provides excellent efficiency allowing for a reduced sized device providing the same effective cooling. Accordingly, a same sized device (as against modern solutions) would provide a greater amount of cooling. In aircraft design, size and weight have significant impacts on overall performance. Therefore, in turn, the present system may be used in a manner that is particularly advantageous when used in aircraft. This system reduces fuel use and therefore provides a lower impact on the environment. Furthermore, the present system allows for more efficient turning of the airflow into the radiator and away from the radiator. In this way, the system can be lighter as it requires less length of conduit in which to turn the air. In the present disclosure there may be an integration of the thermal management system (TMS) of an aircraft and the air delivery system (ADS). Existing TMS systems for fuel cell applications typically handle these two aspects separately. The inventors have devised a system that advantageously combines the requirements of both and utilises increased advantages from the combination. For example, both may use the same infrastructure for ambient air inlet and exhaust ducting. Controlled manipulation of the airflow through the system allows the airflow to be slowed. Slower airflow allows for an increase in the static pressure in the airflow before the airflow interacts with the heat exchanger. This increases the cooling achievable by the airflow and therefore improves the efficiency of the system overall. This also makes heat exchanger design easier because viscous effects are negligible. The viscous effects discussed herein refer primarily to the influence of the viscosity of the air causing friction and other related phenomena, including boundary layer formation, pressure drop, flow separation, increased temperature, each of which impacts the efficiency and operational stability of the heat exchanger. At higher flight Mach numbers, a thicker boundary layer can develop reducing rate of heat transfer. High Mach numbers also lead to increased pressure drops due to higher frictional forces in narrow passages. Flow can in such cases detach and disrupt optimal thermal contact between air and the tubes. At sufficiently high flight Mach numbers, the heat exchanger wall temperature may be considerably higher than free-stream air temperature even though no heat transfer takes place due to viscous dissipation effects which have adverse impact on heat exchanger performance. In examples, the air manipulation portion comprises a rotating element, the rotating element disposed at one of the at least one turn of the flow path. The rotating element will enact a force on the airflow within the system. This disclosure shows that the rotating element can be used to improve the overall heat transfer of the system and therefore improves the overall efficiency of the system. In particular, the rotating element may be used to improve the turning of the flow of air by reducing the flow separation. This action, in turn, improves the rate of cooling and therefore the efficiency of the thermal management system. This also reduces pressure drop brought about by the turn in the duct. This also assists in reducing flow separation. In examples, the rotating element comprises a cylinder, the cylinder being controllably rotatable to provide a controlled airflow around the one of the at least one turn of the flow path. A cylinder can be easily manufactured to specific size and weight requirements. Specifically, the size may correspond to the dimensions of the turn in the flow path or the dimension of the duct at that section of the flow path. Furthermore, the cylinder may be arranged to rotate at a speed that corresponds to a desirable airflow speed. As such, an element of the rotating element may be a cylinder and advantageously provide air turning onto the airflow. In examples, the air manipulation portion comprises a Magnus effect device. The Magnus effect may be used advantageously to drag the fluid around the air manipulation portion (specifically the Magnus effect device). The Magnus effect device can be used to generate a differential in pressure: the side where the fluid is moving in the same direction as the ambient flow experiences a reduction in pressure. In use in the present thermal management system, this pressure differential may result in a force perpendicular to the flow direction, this results in flow turning with minimal flow separation. As noted above, minimal flow separation is preferable to reduce the pressure drop and drag of the system. In contrast, where there is greater flow separation, there is a higher pressure drop which in turn leads to a heavier system with increased drag. In examples, the air manipulation portion comprises an airflow provider for providing an airflow into the flow path, wherein the airflow from the airflow provider is provided at one of the at least one turn of the flow path. By providing airflow into the air flow path around the turn, the flow of turning air encourages the air in the airflow path to turn alongside it. The airflow provider, in effect, provides a disproportionately greater amount of air turning by virtue of providing air at or near a turn in the thermal management system. The air provider may provide air into the airflow path. The same effect can be achieved by an air flow remover, removing air from the airflow path at or near the turn. In examples, the airflow provider comprises at least one of: a compressor; a fan; and, a pump arranged to provide airflow substantially tangentially to one of the at least one turn of the flow path. Providing air at a tangent to a turn will result in the airflow following the contours of the turn even if the surface curves away from the jet’s initial trajectory. This phenomenon is largely driven by the viscosity of the fluid and the momentum exchange between the fast moving jet (from the airflow provider) and the ambient fluid around it, causing a pressure differential that pulls the jet towards the surface. As above, this arrangement generates a turning airflow close to the turn in the system which accordingly impacts the remaining airflow. The impact is greater turning in the airflow with less separation as is desirable for the reasons discussed above. In examples, the air manipulation portion comprises a Coanda effect device. The Coanda effect is a fluid dynamic principle where a moving fluid jet will tend to adhere to a nearby surface. In the context of airflow pathways, the Coanda effect can be strategically harnessed to guide and turn airflow without a requirement for physical vanes. In examples, the heat exchanger comprises a planar liquid-to-air heat exchanger. The thermal management system (TMS) is benefitted by including a liquid-to-air heat exchanger to dissipate heat from the liquid to the airflow through the TMS. Planar heat exchangers are simple to construct and easy to install in the present arrangement of the TMS. As such, this reduces the manufacturing complexity alongside the cost of producing the TMS discussed herein. In examples, the planar liquid-to-air heat exchanger is arranged at a location in the flow path and at an angle to a longitudinal axis of the flow path at the location. Thermal exchange is improved by extending the surface area over which the airflow can interact with the heat exchanger. By arranging the heat exchanger at an incline to the airflow path the surface area available for interaction with airflow is increased and therefore the heat exchanger is more efficient and effective. Performance of the TMS is therefore improved. In examples, the planar liquid-to-air heat exchanger is arranged an angle to a longitudinal axis of the flow path at the location of between 45° to 135°. In examples, the planar liquid-to-air heat exchanger is arranged an angle to a longitudinal axis of the flow path at the location of between 0° to 90°. Arranging the planar liquid-to-air heat exchanger at an angle to the longitudinal axis of the flow path provides advantages in terms of packaging and installation as the frontal area of the exchanger is reduced. This provides an advantage that the duct can be made shorter and the frontal footprint of the installation is smaller which improves the installation and packaging ease. Indeed, the inventors of the system disclosed herein have found than angles of from 75 to 105° are particularly effective at improving heat transfer while not impeding fluid flow through the TMS. The more significant the angle, the more force on the heat exchanger from the incident flow and therefore the greater risk of damage. Furthermore, there is an increase in pressure drop which leads to a reduced cooling capacity due to increased flow reversals and stagnation areas. As such, the angle chosen is a balance between these factors. It is preferable for the air flow to be perpendicular to the heat exchanger and therefore systems herein may preferably turn the air to encounter the thermal exchanger at or around 90°. The turning of the duct and the inclination of the heat exchanger can be arranged to achieve this relative orientation. To improve ease of installation and to have a smaller spatial impact, the heat exchanger may be inclined to the airflow to decouple the inlet duct flow area and the heat exchanger frontal area. Inclination allows for efficient packaging and becomes increasingly more important as the levels of waste heat load increase to multiple megawatt scale in, for example, hydrogen fuel cell aircraft. In examples, the heat exchanger comprises a plurality of cooling conduits heat exchangers. The cooling conduits may be of any size or shape. It may be advantageous for the cooling conduits to be small to increase the externally facing surface area of the cooling conduits. Increase the surface area of a cooling conduit improves the thermal transfer of the cooling conduit. These are particularly effective for use in a heat exchanger. The cooling conduits can be manufactured and arranged with varying tube diameters to benefit different flow turning configurations. This arrangement therefore offers unique design flexibility to blend aerodynamic and thermal properties to achieve highly effective performance from the TMS. The cooling conduits may be flexible, the cooling conduits may be formed of flexible materials or the like. In examples, the plurality of cooling conduits may be or may be part of heat exchangers. The cooling conduits heat exchangers are arranged in a non-equally distributed arrangement. The cooling conduits may be arranged in a non-equally distributed manner, to assist flow turning. A specific example of a “non-equally distributed” manner would be a Fibonacci sequence. In examples, the plurality of cooling conduits heat exchangers are arranged according to Fibonacci sequence. This is a particularly effective arrangement for thermal exchange. The benefit of such an arrangement is the resulting creation of controlled vortices or swirls in the airflow, leveraging the naturally harmonious spacing the Fibonacci sequence provides. This leads to more efficient momentum transfer and pressure gradients within the duct, allowing for smooth flow turning. The inherent design reduces turbulence and results in a more energyefficient flow redirection, especially when low pressure drop turning is used. In examples, the air inlet portion comprises a diffuser and the air outlet portion comprises an outlet nozzle. The diffuser advantageously gradually decelerates the incoming high-speed air, effectively increasing the static pressure of the air before it interacts with the heat exchanger. This in turn leads to a greater efficiency and stability of thermal exchange. The diffuser promotes uniform airflow distribution and reduces potential flow separation. The outlet nozzle is arranged to improve delivery of airflow from the TMS. The nozzle also provides control over the release pressure of the airflow from the TMS. In particular, the nozzle can be used to control exit of airflow and in turn this can be used to control choking or un-choking conditions at the exit of the flow path. Therefore, a certain margin of pressure is preserved to ensure continuous airflow, this can be controlled in part by the nozzle. As the heat exchanger operates efficiently at a predetermined pressure, the nozzle is used to improve the overall efficiency of the heat exchanger. In examples, at least one turn has a turn angle of between 45° to 135°. In use, airflow at the air inlet portion has a speed of around 0.4 Mach to about 0.9 Mach during flight. Airflow at the air inlet portion has a speed of around 0.2 Mach at take off. Airflow at the heat exchanger has a speed of around 0.2 Mach and the deceleration from the air inlet to the air at the heat exchanger (where required) may be provided by a diffuser. The diffuser may be rated for use during cruise where airspeed is greater at the air inlet portion. In examples, the system further comprises a controller arrangement arranged to control an output of the air manipulation portion, the controller arrangement arranged to receive a signal corresponding to a predetermined temperature, wherein the controller is arranged to control output of air of the air manipulation portion in response to receiving the signal corresponding to a predetermined temperature. The system may be arranged to provide an output of air in response to signals relating to temperatures. In use, this may take the form that when greater cooling is required from the integrated TMS, the controller arrangement activates the flow turning to improve the flow of air and therefore improve the cooling provided by the system. In examples, the air turning may be activated when predetermined conditions are met. This may take the form that, during take off or the like the air turning is provided while during cruise air turning is not provided. This allows for a highly efficient and reactive system that provides suitable performance based on the condition of the aircraft. In examples, the air turning may be provided based on a detected stage of flight or the like. In accordance with some embodiments described herein, there is provided an aircraft comprising any of the above examples of a thermal management system, the aircraft further comprising: a propulsion source for providing propulsion to the aircraft; and, a fuselage, the propulsion source located within the fuselage. The present TMS is particularly effective when installed on an aircraft. The TMS uses airflow that may be relative airflow from an external environment to the aircraft. This TMS may be used to provide thermal exchange with components of the aircraft that may increase in temperature during use, but that are preferentially maintained at low temperatures. This may be the propulsion source or the like. Electrical efficiencies at least can be obtained by cooling electronics that may otherwise increase in temperature during use. The TMS disclosed herein is particularly advantageous within an aircraft, however the TMS may be used in any vehicle. In examples, the propulsion source comprises an electrical power source. As noted above, electrical efficiencies at least can be obtained by cooling electronics that may otherwise increase in temperature during use. Electrical power sources may also be more environmentally friendly than standard combustible fuels (such as kerosene). In examples, the propulsion source comprises a plurality of fuel cells. Fuel cells are highly environmentally friendly in the generation of electrical energy for use in propulsion of an aircraft. In examples, the thermal management system is disposed proximally to the plurality of fuel cells. In particular, fuel cells benefit from incoming airflow for use in the production of electrical energy. Fuel cells also generate heat and therefore there is a proximity benefit to having the TMS located proximal to the fuel cells in terms of removal of this generated heat. Such an arrangement also allows for reduced TMS mass and size by removing a need for coolant and pipe mass and size to deliver coolant to distally located fuel cells. In use, there are spatial benefits to having an air delivery system (ADS) installed towards the rear of the fuselage alongside the fuel cells installed towards the rear of the fuselage. This provides lesser distance between the air delivery and the fuel cells which advantageously receive a portion of airflow for use in the production of electrical energy. Similarly, the fuselage of aircraft is an advantageous destination to locate these elements for a variety of reasons. In examples, the propulsion source further comprising a plurality of electrical bus bars arranged to carry electrical energy from the electrical power source, the thermal management system arranged to provide thermal management for each of the plurality of electrical bus bars. 5 Electrical efficiencies can be gained via the provision of cooling to the electrical conduits in the system. The aircraft is therefore improved overall from an efficiency viewpoint via provision of cooling to the electrical bus bars. The TMS may be modular and therefore be able to provide cooling over a distributed network of elements (such as the fuel cells and the bus bars etc). 10 In examples, the thermal management system is disposed towards a rear section of the fuselage. Brief Description of the Drawings One or more embodiments of the invention will now be described, by way of example only, and with reference to the following figures in which: Figure 1 shows a schematic view of a thermal management system according to an example of the present disclosure; Figure 2 shows a schematic view of a thermal management system according to an example of the present disclosure; Figure 3 shows a schematic view of a thermal management system according to an example of the present disclosure; Figure 4 shows a schematic view of a thermal management system according to an example of the present disclosure; Figure 5 shows a schematic view of a thermal management system according to an example of the present disclosure; Figure 6 shows a schematic view of a thermal management system according to an example of the present disclosure; Figure 7a shows a schematic view of an aircraft according to an example of the present disclosure; Figure 7b shows a schematic view of a thermal management system according to an example of the present disclosure; and, Figure 8 shows a schematic view of a thermal management system according to an example of the present disclosure. Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”. The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. It will also be recognised that the invention covers not only individual embodiments but also combination of the embodiments described herein. The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and / or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or 5 consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future. Detailed Description An invention described herein relates to thermal management systems for aircraft. A particular use for this invention may be in an aircraft that is in some way electrically powered. This may be an aircraft with an electrically drivable motor or a drivable motor that is at least partially electrically driven. Aircraft propulsion systems generate heat and can be more efficient if that heat can be removed from the system. As such, the present thermal management system provides improved control over the thermal energy generated in the aircraft and therefore can provide great efficiencies for the aircraft and aircraft systems and components, such as electrical propulsion elements. Figure 1 shows a simple schematic view of a thermal management system 100. The thermal management system 100 may be for an aircraft. The thermal management system 100 may be for an electrically powered aircraft. The system 100 comprises an air inlet portion 110 and an air outlet portion 120 and a flow path 130 from the air inlet portion 110 to the air outlet 120 portion. The air inlet portion 110 is arranged to receive ambient air into the thermal management system 100 from an external environment (denoted by arrow 1000 broadly indicating an area outside of the confines of the TMS 100). The air outlet portion 120 is arranged to provide fluid communication between the thermal management system 100 and an external environment 1000 (as above, arrow 1000 broadly indicates an area outside of the confines of the TMS 100). The TMS 100 includes a flow path (shown by arrow 130) from the inlet 110 to the outlet 120. The flow path 130 includes at least one turn 132. Turns are advantageous in controlling the airflow and therefore constraining the path within the TMS. Turning the airflow can be used to improve the spatial constraints of the TMS when installed. The airflow path 130 can be seen to turn in the direction broadly indicated by arrow A. This occurs and provide a turn 132 in the flow path 130. The TMS 100 comprises an air manipulation portion 140 arranged to provide controlled manipulation to an airflow in the flow path 130. In this way, the air manipulation portion 140 is a controllable element that can provide control over the airflow in the airflow path 130. In examples below, we will discuss how the airflow manipulation portion 140 may be used to improve transit of the airflow around the turn 132 in the flow path. The turn 132 being present in the airflow provides an increased pressure drop. The airflow manipulation portion 140 is arranged to achieve the flow turn with a smaller pressure drop than otherwise would be achieved. As noted above, controlled turning of the air is advantageous for the improved performance of the TMS due to airflow-heat exchanger interactions. The air manipulation portion 140 is arranged to provide controlled turning of the airflow in the flow path 130 around at least one turn 132 of the flow path 130. The TMS 100 comprises a thermal exchanger 150 which is arranged to provide thermal energy exchange with the airflow in the flow path 130. The thermal exchanger 150 is shown to receive incident airflow through the airflow path 130 from the air inlet portion 110. The thermal exchanger 150 may be an air cooled thermal exchanger 150. The thermal exchanger 150 may be a planar liquid-to-air heat exchanger 150 or may be a different form. The thermal exchanger 150 is shown in Figure 1 at an angle to the flow path 130 at the position within the system 100. In examples, the planar liquid-to-air heat exchanger 150 may be arranged at a location in the flow path 130 and at an angle to a longitudinal axis of the flow path 130 at the location. In particular, the thermal exchanger 150 may be at any angle to the flow path 130. In examples, the thermal exchanger 150 may arranged at 0-90° to a longitudinal axis of the flow path 130 at the position of the thermal exchanger 150. In examples, the thermal exchanger 150 may be arranged at 45-135° to a longitudinal axis of the flow path 130 at the position of the thermal exchanger 150. It example, the airflow arrives at the heat exchanger 150 and is flowing in a direction broadly perpendicular to the long axis of the heat exchanger 150. The frontal area of the heat exchanger 150 may be approximately the same as the fuselage cross section to provide highly effective thermal exchange. In particular, the angle © shown in Figure 1 indicates the angle 0 at which the thermal exchanger 150 is to the direction of the flow path 130. This angle 0 may preferably be around 90 degrees for highly effective thermal exchange, however the angle O may be between 45 to 135 degrees or the like. In use, airflow is received via inlet 110 and travels to the outlet 120 along a flow path 130. The flow path 130 includes a turn 132. The airflow may separate around the turn 132 and this is mitigated against by the air manipulation portion 140. The air manipulation portion 140 controls turning of the air around a direction indicated by arrow A. This reduces the likelihood of separation and therefore reduces the static pressure. This controlled airflow is then incident on a heat exchanger 150 and provides high efficiency cooling via the heat exchanger 150. In use, the air manipulation portion 140 creates a low static pressure region around the air manipulation portion 140 of the flow path 130. This in turn pulls flow into the area of the turn 132 located near the air manipulation portion 140. The result is that the separation of the airflow through the flow path 130 at the turn 132 is reduced. Referring now to Figure 2, there is shown a schematic view of a thermal management system 200 according to an example of the present disclosure. Figure 2 shows an example of an arrangement similar to that of Figure 1. The air manipulation portion 240 of the example of Figure 2 is shown adjacent to a portion of the turn in the airflow path. The air manipulation portion 240 assists airflow in the direction shown by the series of arrows B. The arrows B can be seen to remain close to the edge of the turn in the airflow path. In particular, this fluid behaviour is used advantageously herein to generate additional rotational flow in the remaining airflow in the path. In this way, a small amount of controlled airflow (from the portion 240) can provide a great level of output on the air flow in the airflow path. As noted above, this may lead to a greater efficiency experienced by the system from an increased performance of the thermal exchanger (not shown in Figure 2 for simplicity). Referring now to Figure 3, there is shown a schematic view of a thermal management system 300 according to an example of the present disclosure. The system 300 has an air inlet portion 310, a turn in the airflow path along which airflow turns through a direction indicated by arrow C, an air manipulation portion 340 and a thermal exchanger 350. In particular, the air manipulation portion 340 illustrates a Coanda effect device. Air provided from the device 340 stays preferentially on the surface due to the curved nature of the surface. The air manipulation portion 340 may therefore comprise an airflow provider for providing an airflow into the flow path. Specifically, an air jet from a compressor or the like in the portion 340 stays attached to the curved surface when applied tangentially to the convex surface. In this way, airflow is encouraged to follow the turn of the airflow path without significant separation in the flow. The airflow turns along arrow C and is incident on the thermal exchanger 350. The thermal exchanger 350 may take the form of a planar liquid-to-air heat exchanger. In the example shown in Figure 3, the thermal exchanger 350 may comprise a planar heat exchanger. In examples, the thermal exchanger 350 may comprise a plurality of cooling conduits heat exchangers. As mentioned above, these may be relatively small cooling conduits. The conduits may be small bore cooling conduits to increase the surface area of the cooling conduit and in turn improve thermal transfer. The heat exchanger(s) achieves high heat transfer and allows for a low pressure drop. In this way, a thermal exchanger 350 comprising one or more heat exchangers leads to significant efficiency gains in the TMS 300. Such an arrangement of thermal exchanger 350 may be used in any of the examples herein. With a carefully designed duct surface and by introducing air at a predetermined velocity and angle, the air flow adheres to the curved surface, effectively directing the flow along a desired path. Relevant details include the velocity of the compressed air preferably being higher than the velocity of the air stream already present in the duct. In examples, it may be advantageous to have a flow around 3 to 5 times higher than the mainstream flow velocity to control the air flow overcoming the momentum of the separating flow and encouraging that flow to follow the curvature of the surface. The relationship between the radius of the curvature and the height of the jet nozzle may also be relevant. A smaller ratio (e.g. larger curvature relative to the jet height) tends to enhance the Coanda effect as the jet remains attached to the surface more easily. We note a preferable ratio may be in the region of less than 5:1. In the context of ductwork, the Coanda effect can be strategically harnessed to guide and turn airflow without use of physical vanes. In turn, this advantageously provides a reduced pressure drop in the duct and therefore corresponding reductions in the overall TMS mass and size. The arrangement of Figure 3 provides airflow into the flow path via air manipulation portion 340. Providing the airflow close to a turn in the flow path leads to improved air turning as noted above. Providing airflow into a flow path, at a speed greater than the incoming airflow, has a further benefit of pulling air into the flow path from behind. This is by virtue of the high velocity airflow entraining further air flow in the flow path (the duct). The output from the air manipulation portion 340 may be from a compressor or, for example, from a cathode exhaust, and this high velocity air flow downstream within the air flow path leads to a drawing effect on air upstream in the flow path. More air is therefore pulled into the duct and the improved flow rate further enhances the performance of the thermal exchanger 350. Referring now to Figure 4, there is shown a schematic view of a thermal management system 400 according to an example of the present disclosure. The system 400 has an air inlet portion 410, a turn in the airflow path along which airflow turns through a direction indicated by arrow D, an air manipulation portion 440 and a thermal exchanger 450. In particular, the air manipulation portion 440 comprises a Magnus effect device. The device is arranged at or near a turn in the airflow path. The device rotates and airflow around the surface of the Magnus device also rotates. This induces a greater turning effect in the overall airflow while simultaneously reducing separation in the airflow. Specifically, by having an element such as a rotating cylinder, the airflow around the surface of the cylinder is turned, which in turn induces greater turning with limited separation in the overall airflow. The airflow is turned in the direction shown by the arrow D. In this way, airflow is encouraged to follow the turn of the airflow path without significant separation in the flow. As noted above, this is highly advantageous once the airflow interacts with the heat exchanger 450. The heat exchanger 450 in the example shown in Figure 4 may comprise a planar heat exchanger. The heat exchanger 450 may comprise a series of cooling conduits heat exchangers. As noted above for the example of Figure 3, this arrangement may lead to significant efficiency gains in the TMS 400. By utilising a Magnus effect in the ductwork, the airflow can be turned without inclusion of physical vanes or other intrusive components. By introducing a rotating element into the air manipulation portion 440, the flow can be deflected in the desired direction. However, leveraging the Magnus effect for turning flows in the duct requires energy to maintain the rotation of the element within the air manipulation portion 440. As noted above for the arrangement of Figure 3, a turning airflow is provided in Figure 4 by the air manipulation portion 440. The turning airflow of Figure 4 may be at a high velocity (this may be related to the rotating speed of the element 442, which may be a rotating cylinder or the like. Providing airflow turning close to a turn in the flow path leads to improved air turning of the main air flow as noted above. Providing air flow into a flow path, at a speed greater than the incoming airflow, has a further benefit of pulling air into the flow path from behind. This is by virtue of the high velocity airflow entraining further air flow in the flow path (the duct) as noted above. The impact of the air manipulation portion 440 and the rotating element 442 may provide a high velocity air flow which provides a drawing effect on air upstream in the flow path (a similar effect is experienced in the device of Figure 3). A greater amount of air is therefore pulled into the duct and the improved flow rate further enhances the performance of the thermal exchanger 450. Referring now to Figure 5, there is shown a schematic view of a thermal management system 500 according to an example of the present disclosure. The system 500 has an air inlet portion 510, a turn in the airflow path along which airflow turns, an air manipulation portion 540 and a thermal exchanger arrangement 550. The arrangement of Figure 5 has a Magnus effect device in the form of a rotating element. The rotating element may be a rotating cylinder. The cylinder may rotate in such a way as to generate a Magnus effect in the TMS 500. This cylinder may act in the same manner or a similar manner to the rotating element of the example of Figure 4. Figure 5 also comprises a thermal exchanger arrangement 550. The thermal exchanger arrangement 550 may comprise a series of cooling conduits as per earlier examples. The thermal exchanger arrangement 550 may comprise a tube-fin heat exchanger. The heat exchangers may be relatively small to increase the heat transfer area and to improve the pressure drop. These are highly efficient in perform the heat exchange desired with the airflow. The arrangement of Figure 5 differs by the arrangement of the thermal exchangers within the flow path. In particular, as can be seen, there are a series of thermal exchangers. There are thermal exchangers arranged broadly in rows. These rows may be arced. In the example shown in Figure 5, there are nine arced rows of thermal exchangers within the thermal exchanger arrangement 550. The thermal exchangers may be arranged as a series of nested sections 552. In more detail, the coolant in the heat exchangers of the heat exchanger arrangement 550 may be arranged to flow into, and out of, the page. The dotted lines connecting the individual elements within the nested sections 552 represent a header from which a coolant may be delivered to the individual elements (shown by circles). Therefore, in the specific example of Figure 5, there are nine headers (nested sections 552). Each header connects to a series of tubes through which coolant flows into the page. The thermal exchangers may be arranged in a sequence. In particular, the thermal exchangers may be arranged in a non-equally distributed arrangement. Non-equally distributed arrangements are desirable for assisting in air turning. A specific example of a non-equally distributed arrangement would be a Fibonacci sequence. The arrangement (or sequence) of the thermal exchangers may be used to provide additional turning to the airflow while also providing high heat transfer from the heat exchangers to the air. The sequence may be used to maintain low pressure drop alongside the other advantages already noted. The arrangement 540 contains a turning cylinder 542. The cylinder 542 may turn in the direction of the arrow shown in the cylinder 542. Movement in this direction leads to a turning of the airflow as noted above. This arrangement is particularly effective and energy efficient. There is improved thermal energy transfer using the TMS 500 of the examples shown in Figure 5. Where the cooling conduits have a smaller diameter, or a smaller cross sectional area (the conduits need not be circular in cross section, the smaller diameter of the cooling conduits significantly increases the surface area relative to the volume. This is advantageous for the heat exchanger processes, as greater surface area promotes more effective and efficient heat transfer. Small bore cooling conduits, or other similar small size, high surface area heat exchangers, also benefit from a compact design. Such cooling conduits can be densely packed into given space, allowing for designing compact heat exchangers and flow control units. Alongside these, cooling conduits are advantageous from a flow perspective. Such cooling conduits can influence flow behaviour without causing significant disruptions or inducing high levels of turbulence. Furthermore, such cooling conduits can be designed and manufactured to any desirable shape. As a result, shapes can be designed to achieve both heat transfer and turning of the air flow at the same time. An example of such an arrangement is shown in Figure 5. Conventional fins are typically too rigid and manufacturing such fins to follow shapes is very difficult. As such, the cooling conduits as discussed herein have a synergistic advantage in terms of heat transfer and turning of the air flow over more common heat exchangers. Figure 5 shows an example of a TMS 500 including flow turning via Magnus effect alongside Fibonacci sequence. Integrating flow turning with heat exchange through cooling conduits organised in a Fibonacci sequence, allows the system to function as both flow directors and heat exchangers, effectively increasing the temperature of the air, reducing its density and finally increasing its velocity while achieving flow turning at the same time. This is therefore a highly effective and elegant solution. As noted above for the arrangement of Figure 4, a turning airflow is provided in Figure 5 by the air manipulation portion 540. The turning airflow of Figure 5 may be at a high velocity (this may be related to the rotating speed of the turning element 542. Providing airflow turning close to a turn in the flow path leads to improved air turning of the main air flow as noted above. Providing air flow into a flow path, at a speed greater than the incoming airflow, has a further benefit of pulling air into the flow path from behind. This is by virtue of the high velocity airflow entraining further air flow in the flow path (the duct) as noted above. The impact of the air manipulation portion 540 and the rotating element 542 may provide a high velocity air flow which provides a drawing effect on air upstream in the flow path (a similar effect is experienced in the device of Figure 4). A greater amount of air is therefore pulled into the duct and the improved flow rate further enhances the performance of the thermal exchanger arrangement 550. Referring now to the example of Figure 6, there is shown an example of a thermal management system 600 according to examples of the present disclosure. The TMS 600 of Figure 6 has an integrated air delivery system (ADS) air inlet 680 and exhaust 690. The ADS is a system that may provide air to power sources such as to fuel cell stacks. The TMS 600 includes an inlet 610, an outlet 620 and a thermal exchanger arrangement 650. These may be similar to or the same as the equivalent elements in earlier examples. The example of Figure 6 differs in part by the inclusion of an ADS exhaust 690 and an ADS air inlet 680. The inlet 680 includes a compressor and the compressor is used to suck air around the turning edge. The compressor improves the air turning and the flow by virtue of pulling air in a coordinated manner around the turn and into the heat exchanger arrangement 650. The arrangement of Figure 6, provides a thermal management system that includes, or has been combined with, an ADS. This may be advantageous for spatial efficiency in vehicles. In particular, in aircraft, both the TMS and ADS benefit from being located towards the rear fuselage in close proximity with the fuel cell stacks. As such, it may be highly spatially advantageous for the arrangement shown in Figure 6 to include both TMS and ADS. The inlet 680 for the ADS may be around 20% of the inlet 610 for the TMS. The ADS compressor may then elevate the air pressure to a level for use by the fuel cell stacks to around 2 bar. This 20% or so may be compressed and then provided to the fuel cells for use. The exhaust air from the fuel cell stacks may then be exhausted into the TMS duct system. In the arrangement of Figure 6, the ADS inlet 680 is arranged inside the TMS inlet 610. Such an arrangement provides a benefit of boundary layer ingestion. By installing the ducts in the fuselage, the TMS inlet 610 will be ingesting a boundary layer. By positioning the ADS inlet 680 near a boundary layer, it will accelerate the air flow closer the skin of the aircraft and thus improve uniformity at the inlet 610 to the duct. The ADS inlet 680 provides improved air turning by pulling air in the airflow path into the inlet 680. The ADS inlet 680 also results in further entraining of air into the airflow path by creating a faster moving airflow into the inlet 680. This generates a high velocity air flow which entrains air flow behind it (towards the inlet 610). As such, this pulls more air into the air flow path and therefore provides more airflow to pass the thermal exchanger 650. The improved flow rate then enhances the performance of the thermal exchanger 650. As such, the improvement of the inlet 680 on airflow in general in the ducting is in part related to two beneficial impacts of the inlet 680. The arrangement of Figure 6 provides a number of benefits. These benefits include reducing the size and complexity of the system by incorporating the ADS into the same duct as the TMS. It is beneficial to install the ADS intake into a boundary layer intake of the TMS as the ADS can accelerate this boundary layer and can improve flow turning into the exchanger. Integrating these systems also provides reduced drag as flow turning is achieved without a separate additional power source. The ADS inlet 680 can be used to suck the air flow around the turn to encourage flow turning into the heat exchanger 650. By doing so, a lower pressure drop in the flow path may enable use of a smaller heat exchanger 650 designed for larger pressure drop. The relationship between heat exchanger pressure drop and mass is exponential, thus attempts to design heat exchanger 650 for larger allowable pressure drop will accordingly exponentially reduce its mass. In the example of Figure 6, by assisting the flow turning with the ADS inlet 680, the arrangement achieves flow turning into the heat exchanger 650 with smaller pressure drop in the duct. In turn, this results in greater provision to allow for a higher pressure drop in the heat exchanger. In turn this allows for greater flexibility in the design of the heat exchanger, in that the higher pressure drop relaxes requirements on the design of the heat exchanger. The ADS exhaust duct 690 can be used to blow high velocity jet stream around the turn of the flow path to encourage flow turning away from the radiator 650 but also improve flow entrainment and increase air flow throughout the flow path. At cruise the ambient pressure may be around 0.3 bar while the ADS exhaust jet pressure may be around 2 bar. This leads to circa 6.6 pressure ratio, which is sufficient to benefit from Coanda effect to reduce flow separation and improve pressure losses in the exhaust turning of the airflow. The arrangement of Figure 6 provides airflow into the flow path via ADS exhaust duct 690. Providing the airflow close to a turn, and in the direction of the turn, in the flow path leads to improved air turning as noted above. Providing airflow into a flow path, at a speed greater than the incoming airflow, has a further benefit of pulling air into the flow path from behind. This is by virtue of the high velocity airflow entraining further air flow in the flow path (the duct). The output from the ADS exhaust duct 690 may be high velocity air flow from a cathode exhaust, or the like, downstream within the air flow path. This high velocity air output leads to a drawing effect on air upstream in the flow path. More air is therefore pulled into the duct and the improved flow rate further enhances the performance of the thermal exchanger 650. In part, this effect may be referred to as exhaust turning as the exhaust from the cathode can be used to provide improved turning within the duct. In use, air is taken into the ADS air inlet 680 and may be delivered to a compressor to raise the pressure and then provide the compressed air to fuel cell stacks. Humid air then exits the stacks and is passed to the ADS exhaust duct 690 where it is reintroduced into the airflow stream. The ADS inlet 680 removes the air from the air flow. It has been that found around 20% of the air flow can preferably be taken from the air flow and directed towards the fuel cell stacks where electrochemical reaction takes place with hydrogen. In contrast, Figure 3 (an arrangement using a Coanda device) shows an arrangement wherein the air manipulation portion 340 blows air into the TMS duct to encourage flow turning around a turn in the duct. In contrast, the arrangement of Figure 6 extracts airflow from the TMS duct to encourage flow turning around a turn in the duct. Both arrangements, however, improve air flow turning into the thermal exchanger. As such, the present system is highly compatible with Coanda effect devices discussed earlier. Installing ADS ducting within the TMS flow path removes a need for the ADS inlet duct elbow if the ADS inlet had a separate air inlet. In practice, therefore, the TMS ducting provides a suitably advantageous position in which to introduce a portion of the ADS system. As noted above, there are further advantages associated with not including additional power for air turning, which in turn reduces drag. The arrangements discussed herein may each include both TMS and ADS. The arrangement discussed herein may each use Coanda effect devices. The arrangements discussed herein may each include Magnus effect devices. The arrangements discussed herein may use any of the discussed heat exchangers and heat exchanger arrangements. The systems are highly synergistic in providing improved thermal transfer and therefore improved energy efficiency. Referring now to Figures 7a there is shown an aircraft 700 according to examples of the present disclosure. In particular, Figure 7a shows a rear portion of an aircraft 700. The rear portion indicates a suitable location for installation and packaging of both the TMS and the ADS. As shown herein it may be particularly effective for the TMS ducting to include an S bend or the like including a turn. This allows for air to be reduced in speed and systems have been provided herein that maintain low pressure drop in the flow path. This provides a resulting highly effective thermal transfer between the air and the thermal exchanger in the TMS. This also results in an improvement (a reduction) to both mass and drag of the TMS installation. The bend allows for a greater size of thermal exchanger and therefore a greater surface area (though other solutions such as cooling conduits and in particular small cross section cooling conduits are also discussed herein). The diffuser duct may be wrapped around the rear of the fuselage as there is sufficient space to enable modularity of the heat exchangers. The TMS may provide thermal exchanger for electrical bus bars connecting to a large number of fuel cell stacks. In this way, there may be a modular aspect to the heat exchangers. Proposed installation allows for an independent set of heat exchangers servicing each electrical bus to be installed in a modular way 701 as shown in Figure 7a. As an example, if the cooling capacity of the TMS is desired to be increased to service additional heat generating components such as electrical storage systems (ESS) or electrical machines and power electronics, additional heat exchanger modules can be installed circumferentially in a row around the fuselage, or behind in the second row of heat exchangers. The shape of the rear fuselage can also be altered accordingly to enable modular TMS installations with minimal penalty to overall aircraft aerodynamic performance. As such, this provides a solution that results in simple manufacturing and therefore lowers the cost of construction of the solution. The arrangement 705 of Figure 7b shows a TMS ducting route wherein the airflow bends and is passed through a series of heat exchangers prior to exiting the TMS via an outlet. The turn in the arrangement 705 of Figure 7b allows the use of a larger frontal area of heat exchanger. This may lead to larger pressure drops due to flow separation. However, any of the above arrangements for reducing flow separation can be employed in this arrangement and therefore reduce the pressure drop in the duct. As noted above the above arrangements are therefore highly effective for achieving minimum pressure drop in the inlet duct to maintain system efficiency and heat exchanger performance with minimum mass impact and optimal packaging geometries. The above system may be particularly advantageous in aircraft however may be used in any vehicles including automobiles and nautical vehicles. Referring now to the example of Figure 8, there is shown an example of a thermal management system 800 according to examples of the present disclosure. The TMS 800 of Figure 8 has an integrated air delivery system (ADS) air compressor 880 to provide an air jet to the air flow. The jet stays close to the curved surface when applied tangentially to the convex surface. The ADS is a system that may provide air to power sources such as to fuel cell stacks. This air jet therefore reduces separation around the turn in the airflow path from inlet 810 to outlet 820. The system 800 has a heat exchanger array 850 wherein the thermal exchangers are along the flow stream. The exchangers may be of any suitable type. The exchangers may be of any type discussed above. The exchangers may provide a large surface area for thermal exchanger to occur with the air flow through the system 800. Figure 8 shows an example of an arrangement of the heat exchanger array. This may be in any suitable arrangement though the example of Figure 8 provides a larger number of heat exchangers and therefore may improve the thermal exchange efficiency. As noted above for other arrangements, a turning airflow is provided in Figure 8 by the air manipulation portion 880. The turning airflow of Figure 8 may be at a high velocity from a compressor or the like. Providing airflow turning close to a turn in the flow path leads to improved air turning of the main air flow as noted above. Providing air flow into a flow path, at a speed greater than the incoming airflow, has a further benefit of pulling air into the flow path from behind. This is by virtue of the high velocity airflow entraining further air flow in the flow path (the duct) as noted above. The air output of the compressor 880 may provide a high velocity air flow which provides a drawing effect on air upstream in the flow path. A greater amount of air is therefore pulled into the duct and the improved flow rate further enhances the performance of the thermal exchanger array 850.

Claims

1. A thermal management system for an aircraft comprising:an air inlet portion arranged to receive ambient air into the thermal management system from an external environment;an air outlet portion arranged to provide fluid communication between the thermal management system and an external environment;a flow path from the air inlet portion to the air outlet portion, wherein the flow path comprises at least one turn;an air manipulation portion arranged to provide controlled manipulation to an airflow in the flow path;a thermal exchanger arranged to provide thermal energy exchange with the airflow in the flow path;wherein the air manipulation portion is arranged to provide controlled turning of the airflow in the flow path around at least one turn of the flow path.

2. A thermal management system according to claim 1, wherein the air manipulation portion comprises a rotating element, the rotating element disposed at one of the at least one turn of the flow path.

3. A thermal management system according to claim 2, wherein the rotating element comprises a cylinder, the cylinder being controllably rotatable to provide a controlled airflow around the one of the at least one turn of the flow path.

4. A thermal management system according to claim 2 or 3, wherein the air manipulation portion comprises a Magnus effect device.

5. A thermal management system according to any preceding claim, wherein the air manipulation portion comprises an airflow provider for providing an airflow into the flow path, wherein the airflow from the airflow provider is provided at one of the at least one turnof the flow path.

6. A thermal management system according to claim 5, wherein the airflow provider comprises at least one of: a compressor; a fan; and, a pumparranged to provide airflow substantially tangentially to one of the at least one turn of the flow path.

7. A thermal management system according to claim 5 or 6, wherein the air manipulation portion comprises a Coanda effect device.

8. A thermal management system according to any of claims 5-7, wherein the air manipulation portion further comprises an airflow remover for removing an airflow from the flow path,wherein the airflow remover is arranged upstream of the thermal exchanger, and wherein the airflow provider is arranged downstream of the thermal exchanger.

9. A thermal management system according to any preceding claim, wherein the heat exchanger comprises a planar liquid-to-air heat exchanger.

10. A thermal management system according to claim 9, wherein the planar liquid-to-air heat exchanger is arranged at a location in the flow path and at an angle to a longitudinal axis of the flow path at the location.

11. A thermal management system according to claim 10, wherein the planar liquid-to-air heat exchanger is arranged at an angle to a longitudinal axis of the flow path at the location of between 45° to 135°.

12. A thermal management system according to any preceding claim, wherein the heat exchanger comprises a plurality of cooling conduits heat exchangers.

13. A thermal management system according to claim 12, wherein the plurality of cooling conduits heat exchangers are arranged in a non-equally distributed arrangement.

14. A thermal management system according to claim 13, wherein the plurality of cooling conduits heat exchangers are arranged according to Fibonacci sequence.

15. A thermal management system according to any preceding claim, wherein the air inlet portion comprises a diffuser and the air outlet portion comprises an outlet nozzle.

16. A thermal management system according to any preceding claim, wherein at least one turn has a turn angle of between 45° to 135°.

17. A thermal management system according to any preceding claim, further comprising a controller arrangement arranged to control an output of the air manipulation portion,the controller arrangement arranged to receive a signal corresponding to a predetermined temperature,wherein the controller is arranged to control output of air of the air manipulation portion in response to receiving the signal corresponding to a predetermined temperature.

18. An aircraft comprising the thermal management system of any of claims 1-17, further comprising:a propulsion source for providing propulsion to the aircraft; and, a fuselage, the propulsion source located within the fuselage.

19. An aircraft according to claim 18, wherein the propulsion source comprises an electrical power source.

20. An aircraft according to claim 19, wherein the propulsion source comprises a plurality of fuel cells.

21. An aircraft according to claim 20, wherein the thermal management system is disposed proximally to the plurality of fuel cells.

22. An aircraft according to any of claims 19-21, the propulsion source further comprising a plurality of electrical bus bars arranged to carry electrical energy from the electrical power source,the thermal management system arranged to provide thermal management for each of the plurality of electrical bus bars.

23. An aircraft according to any of claims 18-22, wherein the thermal management system is disposed towards a rear section of the fuselage.Application No: GB2408486.5Examiner:Mr Sean O'ConnorClaims searched: 1-23Date of search: 9 December 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1, 5, 6, 9, 10, 12-15, 17-20. US 2020 / 271073 Al (BANHAM) See figure 5 and description thereof. X 1, 5, 6, 9, 10, 12-16, 18-20. US 2016 / 084165 Al (PACKARD) See figures 5 &6 and discussion thereof at paragraph [0031], X 1 at least. US 2017 / 036775 Al (JONES) See figure 3. X 1 at least. US 2022 / 356844 Al (AYOUB) See figures 2-4 and paragraphs [0031]-[0033], X 1 at least. US 2018 / 038243 Al (RAMBO) See figure 3, note turning vane 233 and ejector 230.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of before the filing date of this invention. same category. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP. WO &US patent documents classified in the following areas of the UKCX :Worldwide search of patent documents classified in the following areas of the IPC____________B64D; F02K; F28F________________________________________________The following online and other databases have been used in the preparation of this search reportSEARCH - PATENTInternational Classification:Subclass Subgroup Valid From B64D 0041 / 00 01 / 01 / 2006 B64D 0027 / 355 01 / 01 / 2024 F02K 0003 / 02 01 / 01 / 2006 F02K 0003 / 06 01 / 01 / 2006 F02K 0003 / 115 01 / 01 / 2006

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