Apparatus

Abstract

A motor 200 for an aircraft, comprising: a stator 210 comprising a stator iron maintained, in use, at an ambient temperature and motor coils maintained, in use, at a cryogenic temperature by a cryogen

Description

Technical Field The present invention is concerned with thermal management for motors. Specifically, the present invention is concerned with arrangements wherein the iron is preferably maintained close to ambient temperature while the coils, which are proximal to the iron, are maintained at low temperatures. This arrangement may benefit from careful planning, construction and maintenance to enable two proximal elements to be maintained at rather different temperatures. The present invention is envisaged for use in aircraft. In particular, modern aircraft do not use systems that are overly environmentally friendly due to the high suitability for air flight of combustion fuels such as kerosene. Kerosene provides advantageous energy density and power provision during varying power need portions of the flight envelope. As such, kerosene is the overwhelmingly preferred option for powering air travel. The current status quo therefore means that high power electrical motors are not used, such that considerations in relation to high power electrical motors are not often encountered in aircraft. The present invention provides an improvement in propulsion systems. The presently disclosed system is highly advantageous in aerospace applications. The presently disclosed system has an improved performance and is more easily constructed and maintained and therefore more economically viable than present solutions. 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 motor for an aircraft, comprising: a stator iron maintained, in use, at an ambient temperature; a plurality of motor coils maintained, in use, at a cryogenic temperature by a cryogenic material supplied by a cryogenic material store; an outer composite arrangement arranged externally to the stator iron and the plurality of motor coils, the arrangement comprising: a vacuum arrangement arranged to maintain the stator iron and plurality of motor coils in a vacuum; a compressive element arranged to provide compressive force to the stator iron; and, a cooling arrangement arranged to provide thermal energy transfer from the motor to an external environment, wherein the vacuum arrangement is arranged internally to the cooling arrangement. The present arrangement provides a system that is able to sustain extremely high electrical powers. The present arrangement provides a greener motor for use in aircraft than presently feasible for large scale aircraft. In particular, the present arrangement provides an outer composite arrangement capable of providing cooling to a motor using high electrical power (and therefore that may suffer from high thermal energy generation) while also improving the maintenance of that cooling via use of a vacuum. The present arrangement is a superior arrangement to previous structures noting that maintenance of the integrity of the vacuum does not impact the ease of cooling within the system. The present arrangement is therefore easier to build and assemble and is more efficient than conventional structures. In examples, the cooling arrangement is a passive cooling arrangement. Passive as used herein relates to a cooling system that operates without alteration from external actors. A passive arrangement may operate without impact or control via a user or internal controller or the like. A passive cooling arrangement may not vary the level of cooling provided during use. Such an arrangement is straightforward to construct and maintain. In examples, the cooling arrangement is an active cooling arrangement. The active system may be a cooling system that provides an operation that may alter or change during use. Such operation may be that the cooling in controlled or in some way affected by a user or a controller arrangement. The active cooling arrangement may vary the level of cooling provided during use. This may be based on a requirement for cooling or the like. Such an arrangement is highly responsive and reactive to system need. In examples, the cooling arrangement comprises a fluid for use in thermal energy transfer from the motor to an external environment. Fluids are beneficial for use in cooling as they can be transported through conduits or the like to locations where thermal transfer can occur. In particular, the arrangement is such that the thermal energy from the motor is transferred to an external environment where the thermal energy may be dispersed or used in further heat exchange. Such a system is advantageous in terms of removing thermal energy from a location of thermal energy generation. In examples, the fluid may be any of oil, antifreeze or water or the like. In examples, the fluid is water. Water is particularly effective noting the high heat capacity of water. Water is therefore a compact solution for the arrangement which is advantageous when installing in an aircraft or the like where small sizing is advantageous. In examples, the motor further comprises comprising at least one channel arranged in the outer composite arrangement to receive a fluid of the cooling arrangement. Use of channels allows for greater control over the fluid used in the cooling arrangement. In this way, the cooling from the fluid can be better controlled and therefore better delivered to the motor. In examples, the at least one channel is arranged on an outer surface of the outer composite arrangement. This arrangement is particularly compact. There is no additional elements by which the channels are provided. A compact solution is highly advantageous when installing in an aircraft or the like where small sizing is advantageous. The channels can also be formed integrally with the outer composite which improves design and manufacture of this element as the impact of the channels can be appreciated during the design phase of the motor. In examples, the compressive element comprises a compression ring. The arrangement is benefitted from external stress being implemented the outer composite. In the present system, this may be provided advantageously by a compression ring. In examples, the motor further comprises a vacuum bore tube arranged inwardly of the stator iron. In accordance with some embodiments described herein, there is provided an aircraft comprising the motor of any of the above embodiments or examples. In examples, the aircraft is at least partially electrically powered. The motor of the present disclosure is highly advantageous for use in an electrically powered aircraft. As noted, the sizing of the present motor is compact relative to its power which is advantageous in aircraft production and use. In examples, the aircraft further comprises a cryogenic material store for storing cryogenic material for provision to the plurality of motor coils. The motor coils of the motor may be cooled via a cryogenic material such as low temperature hydrogen or low temperature helium. The hydrogen may be additionally used in power generation from e.g. fuel cells or the like. In accordance with some embodiments described herein, there is provided a method performed by the motor of any of the above examples or embodiments, or the aircraft of any of the above examples or embodiments, the method comprising: maintaining the stator iron at an ambient temperature; maintaining the plurality of motor coils at a cryogenic temperature; applying a vacuum via the vacuum arrangement; compressing the stator iron by the compressive element; and, cooling the vacuum arrangement via the cooling arrangement. 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 motor for an aircraft; Figure 2 shows a schematic view of a motor for an aircraft according to examples of the present disclosure; Figure 3 shows a schematic view of a motor for an aircraft; and, Figure 4 shows a schematic view of a motor for an aircraft according to examples 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 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 The present invention relates to a motor for an aircraft. The motor of an aircraft may be formed from various elements that operate best at specific temperatures. Certain motors may have certain elements that have very different preferable temperatures but that need to be proximal to one another. As such, such motors can benefit from structural rearrangement. The motor herein provides an excellent arrangement for both handling high electrical power and for ease of manufacture and maintenance. The present arrangement is more robust as it overcome shortcomings of previous designs in terms of safety of use and in terms of total mass of motor. Referring to Figure 1, there is shown an example of a motor 100. The motor 100 has an outer vacuum jacket 102, an outer vacuum gap 104, and a water jacket 106 arranged inwardly of the vacuum gap 104. The motor 100 further has a compression ring 108 arranged inwardly of the water jacket 106. The compression ring 108 applies inward force to the station iron 110. The innermost element is the vacuum bore tube 112. This motor 100 is effective however is improved upon in the present disclosure. In particular, the motor 100 has a series of concentric elements that are to be arranged with respect to one another and, if one fails (e.g. the compression ring 108) the motor 100 needs to deconstructed in a piecemeal manner to reveal the compression ring 108 level prior to maintenance. The motor of the present disclosure provides advantages over this motor 100 as will be discussed. Referring now to Figure 2, there is shown an example of the present disclosure. In particular, Figure 2 shows an schematic of a motor 200. As per the example of Figure 1, the motor 200 of Figure 2 has a stator iron 210. The motor 200 has a plurality of motor coils (not shown). In contrast to the arrangement of Figure 1, the motor 200 has an outer composite arrangement 220. The example of Figure 2 also illustrates an internal vacuum bore tube 212. The stator iron 210 is maintained in use at an ambient temperature. The plurality of motor coils are maintained in use at a cryogenic temperature by a cryogenic material supplied by a cryogenic material store. The outer composite arrangement 220 is arranged externally to the stator iron 210 and the motor coils. The outer composite arrangement 220 comprises a vacuum arrangement, a compressive element and a cooling arrangement. The vacuum arrangement is arranged to maintain the stator iron and plurality of motor coils in a vacuum. This is advantageous for maintaining the elements (stator iron and coils) at their preferred (and notably rather different) temperatures. The compressive element is arranged to provide compressive force to the stator iron 210. The cooling arrangement is arranged to provide thermal energy transfer from the motor 200 to an external environment. The vacuum arrangement is arranged internally to the cooling arrangement. The outer composite arrangement 220 is an integral arrangement that provides the function of multiple elements from modern motors (see Figure 1). Notably, in the arrangement of Figure 1, the compression ring was shrunk onto the iron. The ring had optional water cooling incorporated. The vacuum vessel enclosed the arrangement. In contrast, in Figure 2, the present arrangement has a single component combining the functions of the multiple elements of the arrangement of Figure 1. In the arrangement of Figure 2 therefore, the stator iron may be cooled by cooling from the single composite arrangement 220. Advantageously, the cooling fluid need not enter the vacuum space. This therefore is an improvement via reducing the risk of fluid leaks (particularly so in the case of water than can cause significant issues within the motor). The stator iron may preferably be maintained within a temperature range of around -50 to 180 °C. The coils are wrapped around teeth of the stator iron (but do not touch). The coils may be cryogenically cooled. The coils may be maintained within a temperature range of around 20 to 100 K. The coils may be advantageously maintained within a temperature range of around 25 to 40 K. The coils may be cooled by any of hydrogen, helium and nitrogen or the like. The temperature difference is therefore significant and is managed advantageously by the present motor arrangement. The elements may be proximal but separated by a distance on a mm scale. This distance may be a distance of around 4 mm or so. The stator iron is preferably maintained at the temperature noted above as colder temperatures have been found to drop resistivity of the iron. This, in turn, leads to greater eddy current losses and an overall less effective machine. As such, the present system provides a stator iron at a temperature range that is different to the coils. This provides a highly efficient system that is assisted by the construction, and use of, the outer composite arrangement. In particular, this arrangement is benefitted by the provision of the cooling arrangement being located radially outer from the vacuum space (unlike modern systems). The coils may be formed of hyperconductive or superconductive materials. The coils may be high-purity metals, such as aluminium or copper. The stator iron may be magnetic iron or steel or the like. The outer composite arrangement may be formed of a metal alloy. The outer composite may be formed of an aluminium alloy or the like. This is advantegeous as the coefficient of thermal expansion of such materials helps with shrink-fitting. The composite may be formed of other metals or alloys such stainless steel or titanium. The cooling arrangement may be passive for ease of construction and maintenance, and also to reduce the cost of the arrangement. A passive system as used herein may refer to a system that does not alter or cannot alter the cooling provided by the arrangement. For example, a cooling arrangement that is passive may be a jacket of fluid that provides cooling. In a specific example, the cooling arrangement may be a water jacket. The cooling arrangement may be active for improved reactivity and improved responsiveness to operational changes. This may be a system that can and does alter cooling provided by the arrangement either via a user input or via the action of a controller. A cooling arrangement may comprise a pumped source of fluid that can vary the delivery of the fluid to the motor to adjust the cooling provided. This is advantageous when accounting for shifts in temperature during use. The cooling arrangement may use at least one of oil, antifreeze and water or the like. The cooling arrangement is arranged to receive thermal energy from thermally energetic portions of the motor and transport this thermal energy to away from the motor. In use, this may be transferral from the motor to an external environment which may be any of an environment away from the motor for waste heat or may be a heat sink that may benefit from excess thermal energy. This heat sink may be cryogenic fuel that is preferably warmed prior to use in fuel cells or the like. This provides a highly energy efficient arrangement as otherwise waste heat may be reused to increase overall aircraft efficiency. In an example, the cooling system is active, uses water as the fluid for transferral of thermal energy and carries thermal energy away from the motor. Such a solution is compact and highly effective. Referring now to Figure 3, there is shown an example of a motor 300. The motor 300 may have similar features to the features of motor 100 of Figure 1. The view of the Figure illustrates a perspective view of the motor 300. The motor 300 has an outer vacuum jacket 302 that can be seen. The outer vacuum jacket 302 surrounds the motor 300 and is the outermost element. The cooling elements are arranged within the jacket 302 and this can be intricate to manufacture and can be prone to failure. Failure events of the cooling system may cause more damage due to being located within the motor. In contrast, the present solution is shown in Figure 4 in perspective view. Figure 4 shows an example of a motor 400 according to the present disclosure. The motor 400 has an outer composite arrangement 420. The outer composite arrangement 420 has a series of grooves 422 in the outer surface 424 of the arrangement 420. The grooves 422 may be channels or the like. The grooves 422 may hold conduits or the like providing cooling. In the example of Figure 4, then, the cooling fluid need not enter the vacuum of the motor 400 (in contrast to Figures 1 and 3). Use of channels improves the control over the cooling provided by the cooling arrangement. The channels are arranged on an outer side of the outer composite arrangement. In the example shown, this is on an externally-facing outer side. The present arrangement therefore provides cooling outside of the vacuum portion which effectively provides cooling to the motor and reduces risks associated with previous designs. Furthermore, the compression ring and vacuum jacket of Figure 1 are provide by a single composite element such that there is no torque transfer between the elements. This is advantageous for the motor 400 in use. Additionally as the compressive element may be an integral part of the vacuum arrangement, there is a reduced total mass over the motor shown in Figure 1 where the two elements are separate elements. In short, the present system has a reduced cost and complexity alongside improved reliability and reduced risk of failure. Also described are methods of use of the motor and aircraft disclosed herein. Uses of these have associated advantages as noted herein. The present system may be used advantageously in aircraft. Electrically powered aircraft are. In particular, expected to benefit from the presently disclosed motor arrangement. In particular, where the aircraft comprises fuel cells or the like for electrical power generation and cryogenic material may be used to providing cooling for motor elements and as a fuel for the fuel cells. Efficiencies are expected when the present disclosed motor arrangement is implemented in such aircraft.

Claims

1. A motor for an aircraft, comprising:a stator iron maintained, in use, at an ambient temperature;a plurality of motor coils maintained, in use, at a cryogenic temperature by a cryogenic material supplied by a cryogenic material store;an outer composite arrangement arranged externally to the stator iron and the plurality of motor coils, the arrangement comprising:a vacuum arrangement arranged to maintain the stator iron and plurality of motor coils in a vacuum;a compressive element arranged to provide compressive force to the stator iron; and,a cooling arrangement arranged to provide thermal energy transfer from the motor to an external environment,wherein the vacuum arrangement is arranged internally to the cooling arrangement.

2. A motor according to claim 1, wherein the cooling arrangement is a passive cooling arrangement.

3. A motor according to claim 1, wherein the cooling arrangement is an active cooling arrangement.

4. A motor according to any of claims 1-3, wherein the cooling arrangement comprises a fluid for use in thermal energy transfer from the motor to an external environment.

5. A motor according to claim 4, wherein the fluid is water.

6. A motor according to any of claims 1-5, further comprising at least one channel arranged in the outer composite arrangement to receive a fluid of the cooling arrangement.

7. A motor according to claim 6, wherein the at least one channel is arranged on an outer surface of the outer composite arrangement.

8. A motor according to any preceding claim, wherein the compressive element comprises a compression ring.

9. A motor according to any preceding claim, further comprising a vacuum bore tube arranged inwardly of the stator iron.

10. An aircraft comprising the motor of claims 1-9.

511. An aircraft according to claim 10, wherein the aircraft is at least partially electrically powered.

12. An aircraft according to claim 10 or 11, further comprising a cryogenic material store 10 for storing cryogenic material for provision to the plurality of motor coils.

13. A method performed by the motor of any of claims 1 to 9, or the aircraft of any of claims10 to 12, the method comprising:maintaining the stator iron at an ambient temperature;15 maintaining the plurality of motor coils at a cryogenic temperature;applying a vacuum via the vacuum arrangement;compressing the stator iron by the compressive element; and, cooling the vacuum arrangement via the cooling arrangement.

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