A turbine with porous material

Abstract

The invention regards a turbine (2) for transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy,of a fluid into rotational kinematic energy of a rotatable section, the turbine comprising a rotatable section (4) rotatable around an axis of rotation (102), the rotatable section comprising a periphery surrounding the rotatable section, a rotatable section inlet (52) configured to receive a fluid under pressure, a rotatable section outlet (12) configured to emit the fluid, and a conduit connecting the rotatable section inlet and the rotatable section outlet, wherein the conduit accommodates porous material (160, 162, 164), and wherein the conduit forms at least a part of a loop around the axis of rotation.

Description

[0001] A Turbine with porous material

[0002] Field of invention

[0003] The invention relates to a turbine for transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a fluid into rotational kinematic energy of a rotatable section.

[0004] Background of the Disclosure

[0005] Within the field of turbines, where fluid energy of a fluid is transformed into kinematic or kinetic energy of the turbine, there is a desire to extract as much fluid energy as possible from the fluid.

[0006] GB408690A discloses turbine wheels and turbines comprising pervious material.

[0007] Summary of the Disclosure

[0008] Considering the prior art described above, it is an object of the present disclosure to provide a turbine with an improved efficiency rate.

[0009] In a first aspect of the disclosure, the object can be achieved by means of a turbine that transforms fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a fluid into rotational kinematic or kinetic energy of a rotatable section. The turbine comprises a rotatable section rotatable around an axis of rotation. The rotatable section may comprise a periphery surrounding the rotatable section. The rotatable section comprises a rotatable section inlet configured to receive a fluid under pressure and / or a fluid having a velocity, a rotatable section outlet configured to emit the fluid, and a conduit connecting the rotatable section inlet and the rotatable section outlet. The invention is advantageously applicable in power plants, vessels, buses, and in hybrid vehicles, for example as a range extender. However, these are just illustrative applications, and the turbine may be employed in other systems where conversion of fluid energy into rotational energy is desired.

[0010] The conduit accommodates porous material and forms at least a part of a loop around the axis of rotation, preferably more than one loop, such as two, three or four loops, preferably five or more loops, more preferably ten or more loops, more preferably 15 or more loops, and even more preferably twenty or more loops. The number of loops may be selected as a compromise between manufacturing cost and efficiency. For example, a smaller number of loops may be chosen if the turbine is to be used in a car to reduce cost, whereas in power plants a larger number of loops may be used to maximise energy efficiency.

[0011] One advantage of providing a higher number of loops may also be that the temperature drop per loop is reduced, which in turn limits heat exchange between adjacent loops. As a result, the outflow fluid from the rotatable section can be maintained at a lower temperature, thus reducing waste heat and improving the overall efficiency of the turbine. However, a similar effect can also be achieved with a lower number of loops if the conduit walls provide a higher thermal resistance. For example, if the conduit walls are relatively thick and / or made of a material with low thermal conductivity, heat transfer from the conduit to the surrounding environment may be reduced.

[0012] Within the scope of the present application a porous material and a pervious material may be understood interchangeably. The porous material may be a material that has a porosity or a void fraction. The porous material may be an open-cell foam having interconnected pores. The porous material may be a material that has a porosity or a void fraction, where a fluid is able to penetrate through the porous material from one side of the porous material to another side of the porous material. The porous material may be a foamed metal or a foamed ceramic or a sponge. The porous material may be wire wool, perforated plates, radial wires, or an open honeycomb material.

[0013] The porous material may be a material where the void fraction is between 0.1 and 0.9, preferably between 0.2 and 0.7, such as between 0.3 and 0.6, where 0 is no porosity and 1 is nothing but void. High porosities can be advantageous when the conduit forms many loops, since the increased openness of the porous material facilitates flow through the conduit and may reduce the shear stress acting on the turbine.

[0014] A porous material within the context of the present application may be a material that has a permeability or an absolute permeability of between 10-14m2and 10-7m2, or between 10-14m2and 10-8m2, preferably between 10-13m2and 10-9m2, most preferably between 10-12m2and 10-1° m2. Below a permeability or an absolute permeability of 10-14m2the material may be considered impervious. Preferably, the porous material is an isotropic porous material, where the porosity is similar in all directions. The isotropic property helps to ensure that the pressure is equalised in a direction transverse to the fluid flow. Additionally, or alternatively, in some embodiments, the porous material may comprise one or more voids, such as slits or holes, which may extend substantially perpendicular to the direction of fluid flow. Each void may be defined as an empty space within the porous material whose length extends across at least a fraction of the distance between opposite conduit walls in a cross-section of the conduit, measured in a direction transverse to the fluid flow. The length of the void may correspond to at least 1 %, such as at least 5%, such as at least 10%, such as at least 15%, such as at least 25%, such as at least 50%, such as at least 75% of said distance. By providing such voids, pressure equalisation across the porous material can be achieved more effectively, thereby reducing non-uniform expansion of the working fluid as it flows through the conduit of the turbine. Preferably, at least one void, such as two or more voids, is provided per loop, each void preferably being arranged at different positions along the lengthwise extent of the conduit. Preferably, the voids extend in a direction parallel to the axial length of the conduit.

[0015] Alternatively, the voids may extend in a direction perpendicular to the axial length of the conduit, i.e. in a radial direction relative to the axis of rotation.

[0016] One reason why such radial voids or slits may be advantageous is in connection with increasing the capacity of the turbine. Increasing turbine capacity may be achieved by enlarging the conduit, either by increasing the axial length of the conduit or by increasing the diameter of a cross-section of one or more loops of the conduit. In certain applications, however, the axial length of the conduit cannot easily be increased due to limitations of space. Simply increasing the cross-sectional diameter of the loops can lead to small ratios between the inner radius and the outer radius of a loop, the radius being measured from the axis of rotation. In such cases, the working fluid tends to preferentially flow along the shorter flow path closer to the inner radius, which results in poor utilisation of the porous material at the outer radius of any loop of the conduit. To address this problem, radial voids or slits may be provided in the porous material, thus allowing the working fluid to redistribute fluid radially outward towards the outer radius of a loop.

[0017] That the rotatable section inlet is configured to receive a fluid under pressure means that the rotatable section inlet is designed to connect to a pipe and / or a container in a fluid tight connection, where the pipe and / or the container accommodates fluid under pressure.

[0018] The periphery may be a shell such as a cylindrical shell surrounding the rotatable section. The periphery may be a boundary e.g. defined by the conduit.

[0019] The turbine disclosed herein is efficient and well-suited for transforming various types of fluid energy, including thermal energy, pressure energy, and fluid velocity, into rotational energy or rotational kinematic or kinetic energy or mechanical work to be used for driving e.g. a vehicle e.g. mechanically or by driving an electrical generator located in the vehicle, where the electrical generator drives the vehicle. The rotational energy or rotational kinematic or kinetic energy or mechanical work may also be used for driving e.g. a power plant or a pump. By incorporating a conduit with porous material, the turbine ensures optimized fluid flow and energy transformation, leading to improved overall performance. The porous material enables a conduit to provide a higher pressure difference between an inlet, such as the rotatable section inlet, and an outlet, such as the rotatable section outlet, than a conduit without porous material, so that the pressure of the fluid after passing through the conduit with the porous material is lower than after passing through a conduit without porous material. The conduit with the porous material will therefore provide a possibility to extract more work from the turbine than without the porous material.

[0020] As the fluid flows through the turbine, the fluid will act on the porous material accommodated in the conduit. Since the conduit forms at least a part of a loop or more than one loop around an axis of rotation, the force from the fluid acting on the porous material will cause the turbine to rotate. At the same time the pressure will drop and, for compressible fluids there will also be a non-negligible temperature drop. The turbine can be used for providing mechanical work that can drive a vehicle, a generator for generating electricity, a pump for pumping a fluid.

[0021] The at least part of the loop around the axis of rotation provides an angular momentum, or torque, around the axis of rotation of the fluid that through the interaction between the fluid and the porous material that can be transferred to, or can do work on, the conduit and the turbine. By increasing the number of loops to one, two three, or more loops around the axis of rotation, more fluid energy may be transferred to the turbine. This extended interaction between the fluid and the porous material ensures maximum extraction of energy from the fluid, resulting in a higher energy yield compared to conventional turbines.

[0022] In an embodiment, the conduit may comprise a wall accommodating the porous material, wherein the wall is impermeable to the fluid. The benefit of this embodiment is that by ensuring the wall is impermeable to the fluid, leakage is prevented, and the pressure and flow characteristics of the fluid are maintained. This leads to more efficient energy conversion and ensures the structural integrity of the system under varying operating conditions.

[0023] In an embodiment, the conduit may form at least a whole loop around the axis of rotation, preferably at least two loops, more preferably at least three loops, and most preferably at least four loops. The advantage of this embodiment is that the looping design increases the length of the conduit and / or the residence time of the fluid within the conduit. This extended interaction increases the quotient between pressure of the fluid entering the turbine and pressure of the fluid leaving the turbine, so that also energy extraction can be enhanced, resulting in improved energy conversion efficiency. This extended interaction also decreases the quotient between temperature of the fluid leaving the turbine and temperature of the fluid entering the turbine, so that also energy extraction can be enhanced, resulting in improved energy conversion efficiency. Additionally, multiple loops allow for more space, longer conduits, and increased pressure difference over the turbine and lower temperature losses, so that the extracted mechanical work is improved.

[0024] In some embodiments, working fluid is transferred between successive loops through one or more slots or perforations in a conduit wall separating two distinct loops. In other embodiments, working fluid is transferred via one or more passages connecting successive loops, for example by routing the fluid to an axial end of the one loop and back into the next loop. Alternatively, in other embodiments, the loops may be arranged in a spiral geometry, wherein the radial distance of the conduit increases continuously along its lengthwise direction. This obviates the need for slots, perforations, or additional passages between successive loops. The rotational kinematic or kinetic energy provided by the rotatable section may drive a vehicle or an electric generator. The benefit of this embodiment is that it enables the turbine to serve as a power source for diverse applications, including transportation and electricity generation. By converting fluid energy into rotational energy, the turbine provides a sustainable and efficient energy solution for various systems.

[0025] The rotatable section may rotate around the axis of rotation. This embodiment ensures efficient energy transfer by enabling the rotatable section to spin around a defined axis. The design optimizes the conversion of fluid energy into mechanical motion, reducing energy losses and enhancing turbine performance.

[0026] In an embodiment, the rotatable section inlet may be closer to the axis of rotation than to the periphery. The temperature of the fluid decreases when travelling through the conduit. The advantage of the rotatable section inlet being closer to the axis of rotation than to the periphery is that less heat from the fluid will be lost to the surroundings. Heat from the hot fluid at the rotatable section inlet will be transferred to fluid downstream the rotatable section inlet, so that temperature of the fluid downstream the rotatable section inlet will increase and more work can be extracted from the fluid energy. Such a turbine will have a higher efficiency. A further advantage of locating the rotatable section inlet closer to the axis of rotation is that it enables a more compact turbine design, which is particularly suitable for space-limited applications, such as in drones and smaller vehicles and appliances.

[0027] In an embodiment, the conduit may have an upstream part and a downstream part, wherein the downstream part may be positioned further away from the axis of rotation than the upstream part. The advantage of the downstream part being positioned further away from the axis of rotation than the upstream part is that heat from the fluid will not be lost to the surroundings. Heat from the hot fluid at the rotatable section inlet will be transferred to fluid downstream the rotatable section inlet, so that temperature of the fluid downstream the rotatable section inlet will increase and more work can be extracted from the fluid energy. Such a turbine will have a higher efficiency. The downstream part may be covering the upstream part, where the downstream part is positioned on a radius originating in the axis of rotation and passing through the upstream part. The downstream part may be positioned at a larger distance from the axis of rotation than the upstream part. Additionally, or alternatively, the upstream part of the conduit may extend radially from the axis of rotation to within 5% of the radial extent of the rotatable section, such as within 10%, or within 20% of said radial extent. The radial extent of the rotatable section may be defined as the distance from a first part of the rotatable section closest to the axis of rotation to a second part of the rotatable section that is the part of the rotation section farthest from the axis of rotation. By extending the upstream part of the conduit closer to the axis of rotation, the turbine can be designed to be more compact. In an embodiment, the rotatable section may be surrounded by heat insulating material. The inclusion of heat insulating material minimizes thermal losses to the surroundings. By maintaining the temperature of the fluid within the conduit, the turbine ensures efficient energy transfer, particularly in systems involving high-temperature fluids. Preferably, the turbine should be designed, so that the temperature and / or the pressure of the fluid when exiting the rotatable section is / are close to the ambient conditions regarding temperature and pressure. If the turbine has a cylindrical shape with circular ends, the circular ends of the cylinder may also be covered by heat insulating material.

[0028] In an embodiment, the heat insulating material may comprise mineral wool, phenolic foam, aerogel and / or refractory concrete, which provide excellent thermal insulation properties, ensuring minimal heat loss. These materials are lightweight, durable, and capable of withstanding extreme thermal environments, which enhances the operational performance of the turbine.

[0029] In an embodiment, the conduit may comprise a surface or coating for reducing heat transfer. This embodiment improves energy retention by minimizing heat dissipation through the conduit walls. The surface or coating ensures that the fluid maintains its temperature, thereby optimizing the efficiency of thermal energy conversion within the turbine.

[0030] In an embodiment, the porous material may be a porous metal (nickel foam, titanium foam, sintered stainless steel, or foam of Nb, Mo, Tc, Ru, Hf, Ta, W, Re, Os, Ir, Ti, V, Cr, Zr, or Rh), a porous alloy (such as porous superalloys, such as Hastelloy, Inconel, Waspaloy, Rene alloys, Incoloy, MP98T, TMS alloys, and CMSX single crystal alloys), carbon-based material (graphite, carbon fibre composites), ceramic (silicon carbide (SiC), alumina (AI2O3), zirconia (ZrO2)), silica-based material (silica aerogels, fused silica), calcium silicate board, refractory concrete (fire clay, silica), and / or cementbased materials ((Portland) cement with additives). This embodiment ensures material flexibility, allowing the turbine to be tailored for specific operational environments. The choice of material enhances the turbine's durability, thermal resistance, and structural performance under varying temperature and pressure conditions.

[0031] In an embodiment, the conduit may accommodate a second porous material in addition to the porous material, wherein the porous material and the second porous material are two different materials selected from the list above. Preferably, the conduit may comprise the porous material made of a ceramic or a superalloy for withstanding higher temperature, and the second porous material made of metal, where the second porous material is downstream the conduit compared to the porous material.

[0032] In an embodiment, the conduit may accommodate a second porous material in addition to the porous material, wherein the porous material may be configured to withstand a first temperature, T1 , and the second porous material may be configured to withstand a second temperature, T2, wherein T1 > T2. The benefit of this embodiment is the ability to handle extreme thermal gradients efficiently. Materials that can withstand high temperatures will generally be more expensive than material that does have that ability. The temperature in the conduit may vary along the length of the conduit. Where the conduit is hot, it may be necessary to have a porous material that can stand high temperatures, while the turbine may be more cost-efficient if the porous material is made of a material that does not need to withstand as high temperatures and is less costly.

[0033] In an embodiment, the second porous material may be accommodated downstream the conduit compared to the porous material. Since fluid at the rotatable section inlet will generally have a higher temperature than at the rotatable section outlet, the porous material near the rotatable section inlet may have to be of a material that can manage high temperatures, while closer to the rotatable section outlet the porous material may be made of foam of cost-effective materials that does not need to withstand as high temperatures.

[0034] In an embodiment, the turbine or the rotatable section may comprise an initial rotatable section or a rotatable inlet section comprising an initial rotatable section periphery rotatable around the axis of rotation, an initial rotatable section inlet configured to receive a fluid under pressure, and an initial rotatable section outlet configured to emit the fluid into the rotatable section inlet.

[0035] The initial rotatable section may provide a fast transfer of fluid to the rotatable section inlet, where the rotatable section inlet may be situated close to the axis of rotation, so that the hot fluid can be transferred to the inner part of the rotatable section and so that a minimum amount of energy is lost to the surroundings. The initial rotatable section inlet may be located on the initial rotatable section periphery, which may be a technically cost-effective solution, and the initial rotatable section may provide a fast transfer of fluid to the rotatable section inlet that will increase the efficiency of the turbine.

[0036] Before the fluid arrives at the rotatable section inlet, the fluid may pass through the initial rotatable section inlet and the initial rotatable section outlet. The initial rotatable section is typically the hottest part of the turbine, and heat can be lost both to the surroundings, e.g. from a lateral side facing away from the rotatable section and / or to the rotatable section. Losses to the rotatable section are particularly disadvantageous when they are transferred to low-temperature loops of the conduit. Preferably, such losses may be reduced by at least partially or fully enveloping the initial rotatable section with insulating material. The insulation may for example be applied on the side of the initial rotatable section facing away from the rotatable section and / or positioned on the side of the initial rotatable section facing toward the rotatable section.

[0037] The initial rotatable section may rotate synchronously or together with the rotatable section. The initial rotatable section may be attached to the rotatable section, so that the initial rotatable section and the rotatable section cannot rotate and / or move independently of each other. In an embodiment, the initial rotatable section may receive the fluid through the initial rotatable section inlet in an inlet direction that does not extend through the axis of rotation. Additionally, or alternatively, the fluid may have, when entering the initial rotatable section, at least one component, such as two components, of its velocity vector that is tangential to the axis of rotation. For example, if the axis of rotation is defined along the x-axis of a cartesian coordinate system, the velocity vector of the fluid may include at least one component, such as two components in a three-dimensional spatial axis system, in the y- and / or z-direction that is tangential to the x-axis. In other words, the velocity vector of the fluid may comprise a radial component directed towards or away from the axis of rotation, which ensures that the fluid imparts a larger amount of angular momentum to the rotatable section. Preferably, no component of the fluid’s velocity vector is directed along the axis of rotation, in order to maximise the transfer of angular momentum to the initial rotatable section and, consequently, to the turbine. It will be appreciated that reference to the x-, y- and z-directions of a Cartesian coordinate system is made for illustrative purposes only, and that other coordinate systems may equivalently be used to describe the relationship between the fluid velocity vector and the axis of rotation.

[0038] If the fluid is received in the inlet direction that does not extend through the axis of rotation, the fluid will provide an angular momentum to the combination of the turbine and the fluid, and the fluid will influence the initial rotatable section and the turbine as well in such a way that at least some of the energy or angular momentum of the fluid is transferred to the initial rotatable section as an angular momentum, which will cause the initial rotatable section to rotate. That the inlet direction that does not extend through the axis of rotation may mean that the fluid enters tangentially or offset from the axis of rotation. The controlled entry direction improves stability, energy efficiency, and turbine performance.

[0039] In an embodiment, the initial rotatable section may comprise (a) channel(s) and / or (a) blade(s), preferably (a) curved channel(s) or (a) curved blade(s), configured to guide the fluid from the initial rotatable section inlet towards the initial rotatable section outlet.

[0040] The channel(s) and / or the blades will direct the fluid, so that the fluid energy causes the initial rotatable section to rotate even more. This embodiment improves the efficiency of fluid energy conversion into mechanical motion.

[0041] In an embodiment, the channel(s) and / or blades may guide the fluid at least a part of a loop around the axis of rotation, preferably at least half a loop around the axis of rotation.

[0042] The initial rotatable section may be attached to and / or an extension of the rotatable section. The initial rotatable section may rotate independently of the rotatable section, wherein the fluid energy is also transformed into rotational kinematic or kinetic energy of the initial rotatable section, which may also drive the vehicle or the electric generator.

[0043] In an embodiment, the turbine or the rotatable section may comprise a final rotatable section or a rotatable outlet section comprising a final rotatable section periphery rotatable around the axis of rotation, a final rotatable section inlet configured to receive the fluid from the rotatable section outlet, and a final rotatable section outlet configured to emit the fluid. The final rotatable section may guide the fluid from the rotatable section outlet positioned at or close to the periphery of the turbine and / or the rotatable section towards a location at or close to the axis of rotation of the turbine and / or the rotatable section inlet. This transfer of fluid from the periphery inwards is advantageous because, in addition to allowing the remaining fluid energy to be extracted as rotational energy or mechanical work, it also may result in a transfer of angular momentum from the fluid to the rotatable section.

[0044] After the fluid leaves the rotatable section inlet or outlet, the fluid may pass through the final rotatable section inlet.

[0045] The final rotatable section may rotate synchronously or together with the rotatable section. The final rotatable section may be attached to the rotatable section, so that the final rotatable section and the rotatable section cannot rotate and / or move independently of each other.

[0046] In an embodiment, the final rotatable section may comprise channel(s) and / or blades, preferably curved channels or curved blades, configured to guide the fluid from the final rotatable section inlet towards the final rotatable section outlet. This configuration optimizes the flow path of the fluid, reducing turbulence and energy losses. The curved design of the channels or blades ensures a smooth transition of fluid energy into rotational kinematic or kinetic energy, improving the efficiency of the final energy extraction stage. Additionally, or alternatively, the turbine may comprise a final rotatable section in the form of a channel, such as a pipe. The fluid may be received in the final rotatable section from the rotatable section outlet and may flow through the final rotatable section from a radially outer position toward a radially inner position, for example closer to a shaft of the turbine, thereby giving up additional angular momentum as the fluid moves inward and thus further increasing the efficiency of the turbine. The channel, such as the pipe, may not comprise any porous material. Without porous material in the channel, the fluid can be transported through the final rotatable section without significant pressure or temperature drop. A further advantage of not comprising any porous material is that the final rotatable section has a simpler construction, since it may be formed as a conventional pipe or duct. The fluid exiting the final rotatable section may then be directed through the shaft and out of the turbine, such as to a condenser.

[0047] In an embodiment, the rotatable section and / or the turbine may be surrounded by heat insulating material. If the rotatable section and / or the turbine has a cylindrical shape with a lateral surface and end surfaces, both the lateral surface and the end surfaces may be surrounded by heat insulating material. In an embodiment, the end surface close to the rotatable section inlet is covered by heat insulating material. In an embodiment, the end surface close to the rotatable section inlet and the lateral surface are covered by heat insulating material. The inclusion of heat insulating material minimizes thermal losses to the surroundings. By maintaining the temperature of the fluid within the conduit, the turbine ensures efficient energy transfer, particularly in systems involving high-temperature fluids.

[0048] In an embodiment, the conduit may comprise an anti-corrosion coating and / or anticorrosion surface. The benefit of this embodiment is that the anti-corrosion coating or the anti-corrosion surface protects the conduit from fluid-induced corrosion, thereby extending the lifespan of the turbine. The anti-corrosion coating or the anti-corrosion surface ensures reliable performance in harsh operating environments where corrosive fluids may be present.

[0049] In an embodiment, the turbine may comprise a first stationary part and a second stationary part, wherein the rotatable section may be suspended by rotary bearings between the first stationary part and the second stationary part.

[0050] The initial rotatable section, the rotatable section, and the final rotatable section may be suspended by rotary bearings between the first stationary part and the second stationary part. In an embodiment, the turbine may comprise a second rotatable section comprising the axis of rotation, a second periphery rotatable around the axis of rotation, a second rotatable section inlet configured to receive the fluid under pressure, a second rotatable section outlet configured to emit the fluid, and a second conduit connecting the second rotatable section inlet and the second rotatable section outlet, wherein the second conduit may accommodate porous material, and wherein the second conduit may form at least a part of a second loop around the axis of rotation.

[0051] The second rotatable section preferably also rotates around the same axis of rotation as the rotatable section, so that the second rotatable section may be more or less a mirror of the rotatable section mirrored in a plane perpendicular to the axis of rotation, preferably situated at the rotatable section inlet or at the first stationary part.

[0052] Since the fluid entering the turbine may be hot, less heat from the fluid may escape from the turbine having the second rotatable section, so that the efficiency of the turbine may be improved. The reason is that the rotatable section inlet and the second rotatable section inlet, where the hot fluid will enter, may be surrounded by the rotatable section on the one side and the second rotatable section on the other side.

[0053] The second rotatable section may be attached to and / or an extension of the rotatable section. The second rotatable section may rotate independently of the rotatable section, wherein the fluid energy is also transformed into rotational kinematic or kinetic energy of the initial rotatable section, which may also drive the vehicle or the electric generator. The second rotatable section may rotate synchronously or together with the rotatable section. The second rotatable section may be attached to the rotatable section, so that the second rotatable section and the rotatable section cannot rotate and / or move independently of each other.

[0054] In an embodiment, the turbine may comprise a third stationary part, wherein the second rotatable section may be suspended by second rotary bearings between the first stationary part and the third stationary part.

[0055] With the third stationary part, the first stationary part may be positioned between the rotatable section and the second rotatable section, where the rotatable section and the second rotatable section may be suspended by the rotary bearings, providing extra stability to the turbine.

[0056] In an embodiment, the first stationary part may comprise a first stationary part inlet and a first stationary part outlet, wherein the first stationary part outlet and the rotatable section inlet may be positioned opposite each other, so that fluid may be transferable from the first stationary part to the rotatable section at least once a revolution of the rotatable section.

[0057] If the first stationary part comprises the first stationary part inlet and the first stationary part outlet, the fluid may pass through the first stationary part before entering the rotatable section.

[0058] In an embodiment, the first stationary part outlet and the rotatable section inlet may be positioned at or surrounding the axis of rotation.

[0059] If the first stationary part outlet and the rotatable section inlet are positioned at or surrounding the axis of rotation, the fluid may flow from the first stationary part to the rotatable section without interruptions.

[0060] In an embodiment, the first stationary part inlet may be positioned on a first stationary part periphery.

[0061] If the first stationary part inlet is positioned on a first stationary part periphery of the first stationary part, the fluid may be introduced into the first stationary part, so that the fluid may be given an angular momentum around the axis of rotation.

[0062] In an embodiment, the first stationary part inlet may be configured to guide the fluid in a tangential direction when entering the stationary part or so that a fluid velocity vector of the fluid when entering the stationary part may comprise an angular component around the axis of rotation. If the turbine and / or the rotatable section has a cylindrical shape with a lateral surface, the first stationary part inlet may be configured to guide the fluid in a tangential direction of the lateral surface. When the fluid enters the stationary part in a tangential direction or so that a fluid velocity vector of the fluid when entering the stationary part comprises an angular component around the axis of rotation, the fluid may enter the stationary part with an angular momentum around the axis of rotation. Since angular momentum is conserved, the fluid may transfer the angular momentum to the rotatable section, causing it to rotate.

[0063] The inflow fluid velocity vector x a first stationary part inlet vector situated on the axis of rotation and perpendicular to the axis of rotation, where x is the cross product, is not zero, where the direction of inflow is the direction of the fluid entering the first stationary part. This way, the fluid will be given angular momentum around the axis of rotation that will be transferred to the rotatable section, since the angular momentum is kept constant.

[0064] In an embodiment, the first stationary part may comprise channels or blades, preferably curved channels or curved blades, configured to guide the fluid from the first stationary part inlet towards the first stationary part outlet, so that the fluid may have or may be given an angular momentum around the axis of rotation.

[0065] With the channels or the blades configured to guide the fluid from the first stationary part inlet towards the first stationary part outlet, the angular momentum of the fluid will be transferred to the rotatable section and the turbine, which will start rotating, since the angular momentum is conserved, so that the system comprising the fluid and the turbine will keep the angular momentum.

[0066] In an embodiment, the second stationary part may comprise a second stationary part inlet and a second stationary part outlet, wherein the second stationary part inlet and the rotatable section outlet may be positioned opposite each other, so that fluid may be transferable from the rotatable section to the second stationary part at least once a revolution of the rotatable section.

[0067] In an embodiment, the second stationary part inlet may be positioned closer to a second stationary part periphery than the axis of rotation. In an embodiment, the second stationary part outlet may be positioned at or surrounding the axis of rotation.

[0068] In an embodiment, an initial cross-sectional area of the conduit at the rotatable section inlet may be smaller than a final cross-sectional area of the conduit at the rotatable section outlet.

[0069] As the fluid flows through the rotatable section from the rotatable section inlet to the rotatable section outlet, the fluid may expand. To be able to extract more work from the fluid in the turbine, the cross-sectional area at the end of the conduit in the rotatable section may be larger than at the beginning of the rotatable section. The cross- sectional area of the conduit may increase, e.g. substantially evenly, in the rotatable section downstream the conduit.

[0070] The cross-sectional area from the initial cross-sectional area to the final cross-sectional area may increase, e.g. increase substantially evenly.

[0071] In another embodiment, the cross-sectional area of the conduit may decrease, e.g. evenly, in the rotatable section downstream the conduit. In another embodiment, the cross-sectional area of the conduit may be constant.

[0072] In one embodiment, the conduit may have two or more different porosities - a first porosity and a second porosity - where the fluid may flow with more or with less resistance through the first porosity than through the second porosity.

[0073] In an embodiment, the conduit at the rotatable section inlet may have a lower porosity than at the rotatable section outlet.

[0074] As the fluid flows through the rotatable section from the rotatable section inlet to the rotatable section outlet, the fluid may expand. To be able to extract more work from the fluid in the turbine, the porosity at the end of the conduit in the rotatable section may be higher than at the beginning of the rotatable section, increasing the turbine's efficiency.

[0075] Preferably, the porosity increases step-wise from one loop to the next loop of the conduit. For example, a first porosity in a first loop, a second porosity in a subsequent loop, and a third porosity in a further loop, so that the effective porosity increases from the upstream region toward the downstream region of the conduit. In other embodiments, the porosity may vary continuously, for example increasing substantially evenly from the rotatable section inlet to the rotatable section outlet. Alternatively, the porosity from the initial cross-sectional area to the final cross-sectional area may decrease substantially evenly.

[0076] In an embodiment, the turbine may be a heat engine for transforming pressure energy, and preferably thermal energy, of a fluid into rotational kinematic or kinetic energy of a rotatable section.

[0077] In an embodiment, the heat engine may be a Carnot engine.

[0078] In an embodiment, the conduit may accommodate porous material and comprise two or more layers of porous material, each layer being bounded by conduit walls that form the boundary of an axial lengthwise section of the conduit. For example, each layer of porous material may be arranged or confined between two adjacent conduit walls, such that the walls define the boundary of that axial lengthwise section of the conduit.

[0079] Preferably, the layers of porous material and the conduit walls may be arranged around the axis of rotation, such as concentrically and / or cylindrically, so as to form two or more loops of the conduit around the axis of rotation. Each loop may represent a respective axial lengthwise section of the conduit and may comprise at least one, such as two or more, layers of porous material. In this way, the turbine comprises conduit loops, each loop confining porous material between the walls of the conduit, the loops together forming the conduit extending from the rotatable section inlet to the rotatable section outlet. The turbine may further comprise openings to permit the working fluid to flow from one conduit section to an adjacent or next conduit loop, in order that the fluid can flow the full lengthwise extent of the conduit from the rotatable section inlet to the rotatable section outlet.

[0080] Additionally, or alternatively, the turbine may comprise at least one, such as two or more, sub-walls within at least one, such as two or more, such as all of, the conduit sections. The sub-walls may extend partially or fully along the lengthwise extent of the respective conduit loop. The sub-walls may create a sub-division of the porous material accommodated within that loop, so that the loop comprises two or more layers of porous material, the two or more layers being separated on either side of the sub-wall. Since sub-walls separate porous sub-layers within the same loop, where the working fluid pressure is substantially equal, they primarily serve to relieve shear stresses within that loop rather than to withstand pressure differences between separate loops of the conduit. However, in other embodiments, the sub-walls may be of the same or greater thickness than the conduit walls. Accordingly, the sub-walls can advantageously be made thinner than the conduit walls. The sub-walls may be formed of the same material as, or a different material from, the conduit walls, and / or may be of the same or different thickness and / or the same or different strength compared to the conduit walls.

[0081] Additionally, or alternatively, the sub-walls may comprise apertures, such as perforations, openings, or slits, that allow pressure equalisation at a given lengthwise position along the conduit section between the different layers of porous material separated by the sub-walls. Such apertures are particularly advantageous because the division of a conduit section by sub-walls causes the working fluid in different layers to travel different distances, which could lead to pressure imbalances if no equalisation were provided.

[0082] If the pressure drop through the turbine is increased, for example due to a desire by the operator to increase the output of the turbine, the porous material may be subjected to increased shear stresses. By dividing the conduit into multiple conduit sections or loops, and preferably further sub-dividing each section with sub-walls, the effect of such shear stresses can be mitigated, as the increased stress is more effectively distributed. In this way, the turbine can sustain higher pressure drops.

[0083] The example with a concentric and / or cylindrical arrangement of sections of the conduit is provided only for illustrative purposes. Any geometrical arrangement, including for example a spiral design, may be used without deviating from the general design principles discussed herein.

[0084] Additionally, or alternatively, one or more stabilisation elements may be incorporated inside the conduit to relieve shear stresses arising from fluid flow through the porous material. For example, the stabilisation elements may include one or more wires extending through the porous material. The additional walls may extend radially, i.e. outward from the axis of rotation, while the wires may extend lengthwise through the conduit and the porous material accommodated therein, and may be connected to the wall of the conduit by one or more connecting elements. The connecting elements may comprise bars or wires that connect the one or more lengthwise wires with the conduit wall. Stabilisation elements extending through the porous material can help to transfer shear stresses away from the porous material.

[0085] In some embodiments, the porous material may comprise one or more of aluminium, stainless steel, titanium, nickel, copper, bronze, zinc, magnesium, zirconium, cobalt, silver, lead, tantalum, and bismuth. Additionally, or alternatively, the porous material may comprise an alloy of one or more of these metals.

[0086] Preferably, the turbine may be configured to operate with a working fluid selected from one or more of xenon (Xe), ethane (C2H6), trifluoromethane (CHF3), fluoroform (CH3F), hexafluoroethane (CF3CF3), difluoromethane (CH2F2), R-410a, propane, perfluoropropane (CF3CF2CF3), ammonia (NH3), dimethyl ether (CH3OCH3), methyl trifluoromethyl ether (E143a), isobutane, sulfur dioxide (SO2), perfluorodimethylamine ((CF3)2NF), carbon dioxide (CO2), sulfur hexafluoride (SF6), and nitrogen dioxide (NO2).

[0087] Preferably, the turbine may be configured such that the pressure of the working fluid is always equal to or greater than the ambient pressure, thus preventing leakage of ambient air into the system. Advantageously, this requirement may be met by selecting working fluids whose boiling point at ambient pressure is lower than the temperature outside of the turbine, so that the vapour pressure of the working fluid remains above ambient pressure.

[0088] Additionally, or alternatively, the turbine may be operated such that the working fluid passes through the turbine, for example through the rotatable section of the turbine, in the vapour phase and / or above the triple point of the fluid during at least part or the entirety of its passage through the turbine. Alternatively, the turbine may be operated such that the working fluid passes through the turbine, for example through the rotatable section of the turbine, in the supercritical phase and / or above the critical point of the fluid during at least part or the entirety of its passage through the turbine. For example, the turbine may be part of a system comprising a heater, an evaporator, and a condenser, and may be positioned along the flow path of the working fluid between the evaporator and the condenser. In such a system, the working fluid enters the turbine in the vapour phase, such as in a superheated state, and / or above the triple point and passes in and / or through the turbine before being routed to the condenser. Providing the working fluid in a superheated state avoids condensation into liquid droplets inside the turbine and thereby improves turbine performance.

[0089] Alternatively, in a transcritical cycle, the turbine may be positioned along the flow path of the working fluid between a heater and a cooler, wherein the working fluid passes through the turbine in the supercritical phase and / or above the critical point before being cooled by the cooler.

[0090] Preferably, the working fluid is selected such that its critical temperature is greater than a specified reference temperature. The reference temperature preferably corresponds to an expected maximum ambient operating temperature for the area in which the turbine is intended to be used. In some embodiments, the critical temperature of the working fluid exceeds the reference temperature by a margin AT, for example at least 5 °C, more preferably at least 10 °C, and even more preferably at least 15 °C.

[0091] In some embodiments, two or more working fluids may be mixed to obtain properties that are more suitable than those of the individual fluids. For example, mixtures can be tailored to achieve a desired critical temperature and / or boiling point. Advantageously, such mixtures may be selected based on the climate in which the turbine is to operate.

[0092] In an embodiment, the upstream part of the conduit, such as an upstream part of a wall of the conduit, may be made of a first material and the downstream part of the conduit, such as a downstream part of a wall of the conduit, may be made of a second material, the first material having a higher melting and / or sintering temperature than the second material.

[0093] In an embodiment, at least a part of the conduit configured to come into contact with a working fluid, such as one or more walls of the conduit and / or a porous material of the conduit, may have a melting and / or sintering temperature of 300 °C or more, such as 400 °C or more, such as 500 °C or more, such as 600 °C or more, such as 700 °C or more, such as 800 °C or more, such as 900 °C or more, such as 1000 °C or more, such as 1100 °C or more. By employing materials capable of withstanding higher temperatures, the turbine can be operated with a working fluid at elevated temperatures, thereby enabling improved efficiency of the turbine cycle.

[0094] In an embodiment, each wall, which may for example be cylindrical or of another suitable shape configured to confine a layer of porous material, forming a boundary of at least one layer of porous material may be made of a material having a different melting and / or sintering temperature. Preferably, a wall bounding a layer closer to the rotatable section inlet is made of a material with a higher melting and / or sintering temperature than a wall bounding a layer further downstream. More preferably, the melting and / or sintering temperature of successive walls decreases with increasing distance from the rotatable section inlet. By using different materials for the walls depending on their distance from the rotatable section inlet, the turbine can be optimised in terms of cost. Walls located closer to the inlet are exposed to the highest temperatures of the working fluid and can therefore be made from materials with higher melting and / or sintering temperatures. Conversely, walls located farther from the inlet are exposed to lower temperatures and may be made of less temperature-resistant and more economical materials. However, in other embodiments, the same material may be used for all the walls of the conduit. This may help to simplify manufacturing, thereby lowering production costs. Additionally, or alternatively, the material used to form a wall of the conduit may also differ from the material used to form the porous material accommodated within the conduit, such as within a particular loop of the conduit.

[0095] In an embodiment, a first loop of the conduit may accommodate a first porous material and a second loop of the conduit may accommodate a second porous material, the first porous material having a higher melting and / or sintering temperature than the second porous material. In another embodiment, each porous material accommodated in a loop located further from the rotatable section inlet may have a lower melting and / or sintering temperature than an adjacent porous material accommodated in a loop located closer to the rotatable section inlet. Alternatively, the same porous material may be used throughout the conduit, namely within all loops of the conduit. This may simplify manufacturing, reduce complexity, and lower manufacturing cost. In an embodiment, adjacent walls and / or porous materials accommodated within adjacent loops may be made of materials having melting and / or sintering temperatures differing by 1 K or more, such as 2 K or more, such as 5 K or more, such as 10 K or more, such as 20 K or more, such as 40 K or more, such as 50 K or more, such as 100 K or more, such as 200 K or more, such as 300 K or more, such as 500 K or more, such as 1000 K or more. With a higher temperature gradient, the turbine can achieve a given level of efficiency with a shorter conduit length, which allows for a more compact turbine design.

[0096] For example, a wall or porous material accommodated within a loop closer to the rotatable section inlet, where the working fluid is at its highest temperature, may be made of a high-temperature resistant material such as tungsten (melting point -3400 °C), tantalum (-3000 °C), or titanium (-1800 °C). A subsequent, more downstream wall or porous material exposed to lower fluid temperatures may instead be formed of stainless steel (-1500 °C) or Inconel (-1400 °C), while further downstream walls or porous materials may be made of still lower-temperature materials such as copper (-1080 °C), brass (-930 °C), or aluminium (-660 °C). In this way, the material selection across successive loops and / or layers follows the decreasing temperature profile of the working fluid, enabling high efficiency while reducing cost, since the expensive, high- temperature materials are used only where necessary.

[0097] These are merely examples, and the choice of materials will depend on the temperature and mechanical load experienced in each layer. Common materials may include, for example, aluminium alloys (melting point -400-700 °C), aluminium (-660 °C), brass (-930 °C), copper (-1080 °C), cast iron (-1200 °C), Hastelloy (-1330 °C), Inconel (-1400 °C), stainless steel (-1500 °C), titanium (-1800 °C), tantalum (-3000 °C), and tungsten (-3400 °C).

[0098] In a second aspect of the disclosure, there is provided a method of transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a working fluid into rotational kinematic or kinetic energy. The method comprises the steps of providing a turbine according to the first aspect of the disclosure and supplying the fluid to the rotatable section inlet and passing the fluid through the conduit so as to rotate the rotatable section about the axis of rotation and extract rotational kinematic or kinetic energy as the fluid flows through the porous material from the inlet to the outlet.

[0099] Preferably, the turbine is operated as part of a Rankine cycle, such as a transcritical or ultra-supercritical Rankine cycle, which is advantageous for achieving high efficiency.

[0100] In another embodiment, the turbine may be operated as part of a Brayton cycle, such as an open or closed Brayton cycle, or as part of a combined cycle comprising both a Brayton cycle and a Rankine cycle, which is particularly suitable for use within power plants to achieve higher efficiency.

[0101] In an embodiment, the turbine may be operated with a fuel burner supplied with an above-stoichiometric quantity of air. Supplying more air than stoichiometrically required dilutes the exhaust gases and lowers the combustion temperature compared with using a stoichiometric quantity of air. Operating at reduced exhaust gas temperatures allows the use of less costly materials not only for the turbine components, such as the porous material or conduit walls, but also for a heat exchanger used to transfer heat between an exhaust gas and the working fluid. This lowers the overall cost of any system using the turbine according to the present disclosure. This may be particularly advantageous for applications such as automotive powertrains, where cost is a critical factor, and can make the turbine commercially viable for widespread use in vehicles.

[0102] In some embodiments, the turbine may be operated as a pump or compressor, in which case the rotatable section inlet is configured to receive a fluid at a lower pressure and the rotatable section outlet is configured to emit the fluid at a higher pressure.

[0103] In an embodiment, the turbine may be operated in a cycle in which the lowest pressure of the working fluid is 20 bar (absolute) or less, such as 10 bar (absolute) or less, such as 8 bar (absolute) or less, such as 6 bar (absolute) or less, such as 4 bar (absolute) or less. This enables the use of more economical materials for those parts of the conduit, such as those parts closer to the rotatable section outlet, that are exposed only to the low-pressure region of the cycle. For example, the porous material in these regions may be made from lower-cost materials, such as foam (for example, a metallic foam, such as aluminium foam), as these regions do not need to withstand relatively high mechanical stresses. This reduces material costs and makes the turbine particularly attractive for cost-sensitive applications, such as in low-cost vehicles. In a third aspect of the disclosure, there is provided the use of a turbine according to the first aspect of the disclosure, or a method according to the second aspect of the disclosure, for converting fluid energy into useful work for driving a vehicle, generating electricity, operating a power plant, driving a pump, or powering an aircraft.

[0104] Description of the drawings

[0105] The disclosure will in the following be described in greater detail with reference to the accompanying drawings:

[0106] Fig. 1 a a schematic view of a turbine

[0107] Fig. 1 b a schematic view of a rotatable section

[0108] Fig. 2 a schematic view of a cross-section of an inlet section and a rotatable inlet section

[0109] Fig. 3 a schematic view of a first cross-section of the rotatable section

[0110] Fig. 4 a schematic view of a second cross-section of the rotatable section

[0111] Fig. 5 a schematic view of a cross-section of a rotatable outlet section

[0112] Fig. 6 a schematic view of a cross-section of a first insulation layer

[0113] Fig. 7 a schematic view of a toroidal turbine

[0114] Detailed description of the invention

[0115] The turbine 2 according to the present disclosure may have a cylindrical shape as Fig. 1 a shows. The turbine may have a rotatable section 4 with a shaft 6 that rotates together with the cylindrical section. The shaft 6 may extend at both ends of turbine, or the shaft may extend at one end of the turbine. In both cases the rotational movement of the shaft can rotate or drive an external unit (not shown). The turbine will have an inlet section 8 with an inlet pipe 10 for receiving fluid having an inlet pressure, which is above the ambient pressure, and / or an inlet velocity. The inlet section 8 may be in a proximal end of the turbine.

[0116] The turbine 2 may have a rotatable outlet section 12 or a final rotatable section 12 with an outlet (not shown) for disposing of the fluid when a fluid energy has been extracted and transformed to a work energy such as rotational energy of the shaft 6. The turbine 2 may not have a rotatable outlet section, and the outlet (not shown) for disposing of the fluid may be located at the rotatable section 4. The outlet section 12 may be in a distal end of the turbine.

[0117] The turbine may be rotationally suspended at one end by the inlet section 8. The turbine may also be suspended at the other end (not shown).

[0118] In Fig. 1 b, the inlet section 8 shown in Fig. 1 a is removed. The turbine comprises the rotatable section 4 and may also comprise a rotatable inlet section 52 or an initial rotatable section 52 configured to receive a fluid under pressure or a fluid having a velocity from the inlet section (not shown) through openings 54 between walls 56 as shown in Fig. 1 b. The turbine may have the rotatable outlet section 12 configured to emit the fluid as shown in Fig. 1 b. The shaft 6 may be attached to the rotatable inlet section 52 and / or the rotatable section 4 and / or the rotatable outlet section 12.

[0119] The turbine may have a first insulation layer 58 at the proximal end of the turbine. The rotatable section 4 may have a second insulation layer 60 as a lateral surface surrounding the rotatable section.

[0120] To better show the parts of the turbine 2, sectional views of the turbine are shown in Figs. 2-6.

[0121] Fig. 2 shows the sectional view of the rotatable inlet section 52 with curved impellers 100 and the inlet section 8 along the dashed line II - II in Fig. 1 a. The fluid may enter the inlet section 8 through the inlet pipe 10 in a tangential direction to the circumference of the rotatable inlet section 52 as Fig. 2 shows. In this way, the fluid enters the rotatable inlet section 52 with an angular momentum in relation to an axis of rotation 102, which is coaxial with the shaft (not shown). The inlet pipe 10 may have a curved inlet pipe end 104 around the rotatable inlet section 52 as Fig. 2 shows. The curved inlet pipe end 104 may have a decreasing height around the rotatable inlet section 52, so that a first height 106a in the curved inlet pipe end 104 is larger than a second height 106b downstream in the curved inlet pipe end 104 as Fig. 2 shows. The curved inlet pipe end 104 and / or the decreasing height provide(s) an even distribution of fluid around the rotatable inlet section 52 and to all the impellers 100. Within the context of the present disclosure “longitudinal direction” may be understood as the longitudinal direction of the turbine from the rotatable inlet section 52 to the rotatable outlet section 12 or along the axis of rotation.

[0122] The impellers 100 will guide the fluid towards a rotatable inlet section exit 108, where the fluid will exit the rotatable inlet section and enter the rotatable section (not shown). As the fluid flows between the impellers 100, the fluid will rotate the impellers and the rotatable inlet section 52. Alternatively, the impellers 100 and the rotatable inlet section 52 may be stationary and not rotating, but cause the fluid to rotate and whirl through the rotatable inlet section exit 108. In one alternative there is no impellers in the rotatable inlet section 52. If the rotatable inlet section 52 is stationary, the shaft shown in Figs. 1 a and 1 b will extend through the stationary rotatable inlet section 52 and have perforations and be hollow for allowing the fluid to pass from between the impellers 100 through the perforations and out through the rotatable inlet section exit 108.

[0123] Alternatively, instead of the reducing height of the curved inlet pipe end 104 around the rotatable inlet section 52 along the length, the height may be constant. Instead of the curved inlet pipe end 104 stretching all around the rotatable inlet section 52, the curved inlet pipe end 104 may only or at least cover the distance between two neighbouring walls 56.

[0124] Fig. 3 shows the sectional view of the rotatable section 4 along the dashed line III - III in Fig. 1 b. The rotatable section 4 may have a first cylindrical wall 150, surrounded by a second cylindrical wall 152, surrounded by a third cylindrical wall 154, surrounded by a fourth cylindrical wall 156 as Fig. 3 shows. Within the first cylindrical wall 150, there may be a centre cylinder 158 that is empty, between the first cylindrical wall 150 and the second cylindrical wall 152, there may be a first cylindrical layer 159 comprising a first porous material 160, between the second cylindrical wall 152 and the third cylindrical wall 154, there may be a second cylindrical layer 161 comprising a second porous material 162, between the third cylindrical wall 154 and the fourth cylindrical wall 156, there may be a third cylindrical layer 163 comprising a third porous material 164, as Fig. 3 shows. The centre cylinder 158 may be tapered with a wider part closer to the inlet section 8 or the rotatable inlet section 52 and a pointed end closer to the rotatable outlet section 12, so that the fluid will be more spread out along all the length of the centre cylinder 158 for an improved rate in transforming the fluid energy to kinetic energy of the turbine. The first porous material 160, the second porous material 162, and the third porous material 164 may be the same porous material, may be different porous materials differing by the porosity and / or permeability and / or ability to handle hot fluid.

[0125] In general, the first porous material 160 may have to withstand a higher temperature than the second porous material 162, and the second porous material 162 may have to withstand a higher temperature than the third porous material 164. To that end, preferably, the porous material of a cylindrical layer further from the rotatable section inlet may be made of a material having a lower melting and / or sintering temperature than an adjacent porous material of a cylindrical layer closer to the rotatable section inlet.

[0126] Since the porous material closer to the rotatable section inlet is exposed to higher temperatures of the incoming working fluid, it is advantageously made from a material with a higher melting and / or sintering temperature. In contrast, porous material located farther from the inlet is subjected to lower working fluid temperatures and can therefore be formed from materials with lower melting and / or sintering temperatures. By tailoring the choice of material to the temperature profile along the conduit, the turbine can operate reliably without risk of material decomposition while also reducing costs. Materials with higher melting and / or sintering temperatures are typically more expensive per unit volume than materials with lower thresholds. Accordingly, the use of different porous materials enables the costly high-temperature resistant material to be applied only where necessary within the conduit, while more economical materials can be used downstream from the rotatable inlet section where temperatures are lower.

[0127] The first cylindrical wall 150 may also advantageously be made of a material having a higher melting and / or sintering temperature than the second cylindrical wall 152, which in turn may have a higher melting and / or sintering temperature than the third cylindrical wall 154, and so on, such that each cylindrical wall further from the rotatable section inlet is made of a material having a lower melting and / or sintering temperature than an adjacent cylindrical wall closer to the rotatable section inlet. The same advantages as described above for the porous materials apply here, i.e. that walls located closer to the rotatable section inlet can withstand the higher temperatures of the incoming working fluid, while walls farther from the inlet are exposed to lower temperatures and can be made of materials with lower melting and / or sintering temperatures. The permeability of the fluid through the porous material may increase for each cylindrical layer in a direction away from the axis of rotation 102 or downstream the conduit. The permeability of the fluid through the porous material may decrease for each cylindrical layer in a direction away from the axis of rotation 102. There may be more or fewer cylindrical walls and cylindrical layers with porous material than is shown in Fig. 3. The third cylindrical layer 163 may in addition to the third porous material 164 also comprise a void 165 extending along the length or the whole length of the third cylindrical layer 163 in the longitudinal direction. Preferably the void is free of porous material. At the distal end of the void 165, there is a rotatable section exit 166, where the fluid may exit the void 165 and the rotatable section 4. The void may have a tapered shape, where the void is pointed at the proximal end and has larger crosssection in the distal end, so that the fluid in the proximal end of the third cylindrical layer 163 can as easily leave the void and pass through the rotatable section exit 166 as fluid in the distal end of the third cylindrical layer.

[0128] The first porous material 160, the second porous material 162, and / or the third porous material 164 may have an empty slot perpendicular to the fluid flow, where the empty slot may extend from the proximal end to the distal end of the porous material, for providing a more even distribution of the fluid in the porous material. That will increase the rate of transforming the fluid energy to kinematic or kinetic energy of the turbine.

[0129] As the fluid flows through the first porous material 160, the second porous material 162, and the third porous material, the fluid energy will be transformed to rotational kinematic or kinetic energy of the rotatable section 4, so that the temperature and the pressure of the fluid will decrease and so that the fluid will pass through the rotatable section exit 166 with pressure and temperature at or close to the ambient pressure and temperature.

[0130] As the fluid flows through the rotatable section 4, the temperature of the fluid will decrease. Since the fluid enters the rotatable section 4 at the centre, the heat of the fluid cannot dissipate to the surroundings but will be transferred to the fluid in the first cylindrical layer 159, so that more of the fluid energy can be transformed to kinematic or kinetic energy of the turbine. The first cylindrical wall 150 may have a first slot 167 preferably along the length or the whole length of the first cylindrical wall 150 in the longitudinal direction for connecting the centre cylinder 158 and the first cylindrical layer 159, the second cylindrical wall 152 may have a second slot 168 preferably along the length or the whole length of the second cylindrical wall 152 in the longitudinal direction for connecting the first cylindrical layer 159 and the second cylindrical layer 161 , the third cylindrical wall 154 may have a third slot 170 preferably along the length or the whole length of the third cylindrical wall 154 in the longitudinal direction for connecting the second cylindrical layer 161 and the third cylindrical layer 163, as Fig. 3 shows.

[0131] A first intermediate wall 172 may connect the first cylindrical wall 150 and the second cylindrical wall 152 for guiding the fluid from the first cylindrical layer 159 to the second cylindrical layer 161 through the second slot 168, just before the fluid completes a whole revolution in the first cylindrical layer 159, a second intermediate wall 174 may connect the second cylindrical wall 152 and the third cylindrical wall 154 for guiding the fluid from the second cylindrical layer 161 to the third cylindrical layer 163 through the third slot 170, just before the fluid completes a whole revolution in the second cylindrical layer 161 , and a third intermediate wall 176 may connect the third cylindrical wall 154 and the fourth cylindrical wall 156 for guiding the fluid from the third cylindrical layer 163 out through the rotatable section exit 166 and out of the rotatable section 4, just before the fluid completes a whole revolution in the third cylindrical layer 163.

[0132] Fig. 4 shows the sectional view of the rotatable section 4 along the dashed line IV - IV in Fig. 1 b. Fig. 4 shows the first cylindrical wall 150, the second cylindrical wall 152, the third cylindrical wall 154, the fourth cylindrical wall 156, the centre cylinder 158, the first cylindrical layer 159, the first porous material 160, the second cylindrical layer 161 , the second porous material 162, the third cylindrical layer 163, and the third porous material 164.

[0133] The fluid may enter the centre cylinder 158 from the rotatable inlet section (not shown) through the rotatable inlet section exit 108 and a rotatable section inlet 200, as Fig. 4 shows. For handling high pressure of the fluid, the centre cylinder 158 may have a centre cylinder end 202 with a half cylindrical cross-section, as Fig. 4 shows. The first cylindrical layer 159, the second cylindrical layer 161 , the third cylindrical layer 163 may also have cylindrical layer ends 204 with half cylindrical cross-sections, as Fig. 4 shows.

[0134] The height and / or the cross-section area of the first cylindrical layer 159 may be smaller than the height and / or the cross-section area of the second cylindrical layer 161 , and the height and / or the cross-section area of the second cylindrical layer 161 maybe smaller than the height and / or the cross-section area of the third cylindrical layer 163 for converting more fluid energy to kinematic or kinetic energy of the turbine, and for better handling an increasing fluid volume flow as the fluid expands through the first cylindrical layer 159, the second cylindrical layer 161 , and / or the third cylindrical layer 163.

[0135] Fig. 5 shows the sectional view of the rotatable outlet section 12 along the dashed line V - V in Fig. 1 b.

[0136] The rotatable outlet section 12 may receive fluid from the rotatable section exit (not shown) of the rotatable section (not shown) through the rotatable outlet section inlet 250. The rotatable outlet section inlet 250 may be positioned just opposite the rotatable section exit (not shown) of the rotatable section (not shown), and the rotatable outlet section 12 and the rotatable section (not shown) may be attached to each other and / or rotate together. From the rotatable outlet section inlet 250, the rotatable outlet section 12 may comprise a channel 252 for guiding fluid towards a rotatable outlet section centre 254 around the axis of rotation 102, as Fig. 5 shows. From the rotatable outlet section centre 254, the fluid will exit the rotatable outlet section 12 and the turbine in the distal direction. By leaving the turbine along the axis of rotation 102, the fluid will transfer even more of the angular momentum to the turbine, thus improving the efficiency rate of the turbine even more.

[0137] Fig. 6 shows the sectional view of the first insulation layer 58 along the dashed line VI - VI in Fig. 1 b. Fig. 6 also shows the shaft 6. The first insulation layer 58 insulating the proximal short end of the rotatable inlet section (not shown) insulates the part of the turbine, where the fluid has the highest temperature.

[0138] In an alternative embodiment of the disclosure, where a toroidal turbine 2’ comprises a toroidal rotatable section 4’ having the shape of a toroid, as Fig. 7 shows. Features described above, which have the same function, are given the same reference numbers in Fig. 7.

[0139] The toroidal turbine 2’ may be connected to the shaft 6 by a plate or by spokes 300 for transferring the rotational movement of the toroidal turbine 2’ to the shaft 6 rotatable around an axis of rotation 102.

[0140] The fluid will enter the toroidal rotatable section 4’ through an inlet section 8’ that is stationary. The fluid may enter the toroidal rotatable section 4’ through the inlet section 8’ tangentially to the toroidal rotatable section 4’. The inlet section 8’ has an inlet pipe (not shown), where the fluid under pressure and / or with a velocity enters the inlet section. The inlet section 8’ may wrap around the toroidal rotatable section 4’, as Fig. 7 shows, where the fluid may be guided by the impellers or channels 100’, preferably curved impellers or channels, towards a centre toroid 158’. The impellers or channels 100’ may stretch all the way around the toroidal rotatable section 4’. The impellers or channels 100’ may be stationary. The toroidal rotatable section 4’ and the inlet section 8’ are tightened against each other for preventing leakage of fluid at the connection between the toroidal rotatable section 4’ and the inlet section 8’. The tightening may be achieved by rubber seals on each side, where the toroidal rotatable section 4’ is in contact with the inlet section 8’.

[0141] The fluid flowing in the inlet section 8’ may experience a decreasing cross-section area as the fluid flows further away from the inlet pipe, as Fig. 7 shows, for providing an even distribution of fluid to the toroidal rotatable section 4’ independent on the angular position of the toroidal rotatable section 4’.

[0142] The toroidal rotatable section 4’ may comprise a first toroidal wall 150’ surrounding the centre toroid 158’. The toroidal rotatable section 4’ may comprise a second toroidal wall 152’ forming with the first toroidal wall 150’ with a first toroidal layer 159’ with a first porous material 160, a third toroidal wall 154’ forming with the second toroidal wall 152’ with a second toroidal layer 161 ’ with a second porous material 162, and a fourth toroidal wall 156’ forming with the third toroidal wall 154’ with a third toroidal layer 163’ with a third porous material 164, as Fig. 7 shows. The first toroidal wall 150’ has a first opening (not shown) connecting the centre toroid 158’ and the first toroidal layer 159’. The second toroidal wall 152’ has a second opening (not shown) connecting the first toroidal layer 159’ and the second toroidal layer 161 ’. The third toroidal wall 154’ has a third opening (not shown) connecting the second toroidal layer 161 ’ and the third toroidal layer 163’. The fourth toroidal wall 156’ has a fourth opening (not shown) connecting the third toroidal layer 163’ with a rotatable toroidal outlet section 12’ and a stationary outlet section 12”. The stationary outlet section 12” has an exit (not shown) for exiting the fluid from the toroidal turbine 2’.

[0143] A first intermediate wall (not shown) may block the centre toroid 158’ just after the first opening (not shown) for guiding the fluid from centre toroid 158’ to the first toroidal layer 159’ through the first opening. A second intermediate wall (not shown) may block the first toroidal layer 159’ just after the second opening (not shown) for guiding the fluid from the first toroidal layer 159’ to the second toroidal layer 161 ’ through the second opening, just before the fluid completes a whole revolution in the first cylindrical layer 159’. A third intermediate wall (not shown) may block the second toroidal layer 161 ’ just after the third opening (not shown) for guiding the fluid from the second toroidal layer 161 ’ to the third toroidal layer 163’ through the third opening, just before the fluid completes a whole revolution in the second cylindrical layer 161 ’. A fourth intermediate wall (not shown) may block the third toroidal layer 163’ just after the fourth opening (not shown) for guiding the fluid from the third toroidal layer 163’ out of the toroidal rotatable section 4’ to the rotatable toroidal outlet section 12’ and the stationary outlet section 12”.

[0144] The fluid is flowing in the first toroidal layer 159’, the second toroidal layer 161 ’, and the third toroidal layer 163’ in the same direction around the axis of rotation, so that the fluid energy can be transferred to a rotational kinetic energy of the toroidal rotatable section 4’ that will rotate the shaft 6 for driving e.g. a power plant, a pump, or a vehicle.

[0145] Items

[0146] 1 . A turbine for transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a fluid into rotational kinematic or kinetic energy of the turbine or a rotatable section of the turbine, the turbine comprising a rotatable section rotatable around an axis of rotation, the rotatable section comprising

[0147] - a periphery surrounding the rotatable section,

[0148] - a rotatable section inlet configured to receive a fluid under pressure,

[0149] - a rotatable section outlet configured to emit the fluid, and

[0150] - a conduit connecting the rotatable section inlet and the rotatable section outlet, wherein the conduit accommodates porous material, and wherein the conduit forms at least a part of a loop, such as at least a quarter of a loop or at least half a loop, or more than a loop, such as more than one and a quarter of a loop or more than one and a half of a loop, around the axis of rotation. The turbine according to item 1 , wherein the rotatable section inlet is closer to the axis of rotation than to the periphery, such as from a radial point of view or in a radial direction. The turbine according to any of the preceding items, wherein the conduit has an upstream part and a downstream part, wherein the downstream part is positioned further away from the axis of rotation than the upstream part, such as from a radial point of view or in a radial direction. The turbine according to any of the preceding items, wherein the porous material is

[0151] - a porous metal or a porous alloy,

[0152] - carbon-based material,

[0153] - ceramic,

[0154] - silica-based material,

[0155] - calcium silicate board,

[0156] - refractory concrete, and / or

[0157] - cement-based materials. The turbine according to any of the preceding items, wherein the conduit accommodates a second porous material in addition to the porous material, wherein the porous material is configured to withstand a first temperature, Ti, and the second porous material is configured to withstand a second temperature, T2, wherein Ti > T2.

[0158] 6. The turbine according to item 5, wherein the second porous material is accommodated downstream the conduit compared to the porous material.

[0159] 7. The turbine according to any of the preceding items, wherein the turbine comprises an initial rotatable section comprising

[0160] - an initial rotatable section periphery rotatable around the axis of rotation,

[0161] - an initial rotatable section inlet configured to receive a fluid under pressure, and

[0162] - an initial rotatable section outlet configured to emit the fluid into the rotatable section inlet.

[0163] 8. The turbine according to item 7, wherein the initial rotatable section is configured to receive the fluid through the initial rotatable section inlet in an inlet direction that does not extend through the axis of rotation.

[0164] 9. The turbine according to item 7 or 8, wherein the initial rotatable section comprises (a) channel(s) and / or (a) blade(s), preferably curved channels or curved blades, configured to guide the fluid from the initial rotatable section inlet towards the initial rotatable section outlet.

[0165] 10. The turbine according to item 9, wherein the channel(s) and / or blades is / are configured to guide the fluid at least a part of a loop around the axis of rotation, preferably at least half a loop around the axis of rotation.

[0166] 11 . The turbine according to any of the preceding items, wherein the turbine comprises a final rotatable section comprising

[0167] - a final rotatable section periphery rotatable around the axis of rotation,

[0168] - a final rotatable section inlet configured to receive the fluid from the rotatable section outlet, and

[0169] - a final rotatable section outlet configured to emit the fluid. 12. The turbine according to any of the preceding items, wherein the turbine comprises a first stationary part and a second stationary part, wherein the rotatable section is suspended by rotary bearings between the first stationary part and the second stationary part.

[0170] 13. The turbine according to item 12, wherein the turbine comprises a second rotatable section comprising the axis of rotation,

[0171] - a second periphery rotatable around the axis of rotation,

[0172] - a second rotatable section inlet configured to receive the fluid under pressure,

[0173] - a second rotatable section outlet configured to emit the fluid, and

[0174] - a second conduit connecting the second rotatable section inlet and the second rotatable section outlet, wherein the second conduit accommodates porous material, and wherein the second conduit forms at least a part of a second loop around the axis of rotation.

[0175] 14. The turbine according to item 13, wherein the turbine comprises a third stationary part, wherein the second rotatable section is suspended by second rotary bearings between the first stationary part and the third stationary part.

[0176] 15. The turbine according to any of the items 12 - 14, wherein the first stationary part comprises a first stationary part inlet and a first stationary part outlet, wherein the first stationary part outlet and the rotatable section inlet are positioned opposite each other, so that fluid is transferable from the first stationary part to the rotatable section, at least once a revolution of the rotatable section.

[0177] 16. The turbine according to item 15, wherein the first stationary part outlet and the rotatable section inlet are positioned at or surrounding the axis of rotation.

[0178] 17. The turbine according to item 15 or 16, wherein the first stationary part inlet is positioned on a first stationary part periphery. 18. The turbine according to any of the items 12 - 17, wherein the first stationary part inlet is configured to guide the fluid in a tangential direction when entering the stationary part or so that a fluid velocity vector of the fluid when entering the stationary part comprises an angular component around the axis of rotation.

[0179] 19. The turbine according to any of the items 12 -18, wherein the first stationary part comprises channels or blades, preferably curved channels or curved blades, configured to guide the fluid from the first stationary part inlet towards the first stationary part outlet, so that the fluid has or is given an angular momentum around the axis of rotation.

[0180] 20. The turbine according to any of the items 12 - 19, wherein the second stationary part comprises a second stationary part inlet and a second stationary part outlet, wherein the second stationary part inlet and the rotatable section outlet are positioned opposite each other, so that fluid is transferable from the rotatable section to the second stationary part, at least once a revolution of the rotatable section.

[0181] 21 . The turbine according to item 20, wherein the second stationary part inlet is positioned closer to a second stationary part periphery than the axis of rotation.

[0182] 22. The turbine according to item 20 or 21 , wherein the second stationary part outlet is positioned at or surrounding the axis of rotation.

[0183] 23. The turbine according to any of the preceding items, wherein an initial crosssection area of the conduit at the rotatable section inlet is smaller than a final cross-section area of the conduit at the rotatable section outlet.

[0184] 24. The turbine according to any of the preceding items, wherein the conduit has two, a first porosity and a second porosity, or more different porosities, where the fluid may flow with more or with less resistance through the first porosity than through the second porosity.

[0185] 25. The turbine according to any of the preceding items, wherein the conduit at the rotatable section inlet has a lower porosity than at the rotatable section outlet. 26. The turbine according to any of the preceding items, wherein the turbine is a heat engine for transforming pressure energy, and preferably thermal energy, of a fluid into rotational kinematic or kinetic energy of a rotatable section.

[0186] 27. The turbine according to item 26, wherein the heat engine is a Carnot engine.

[0187] 28. The turbine according to any of the preceding items, wherein the conduit comprises two or more loops around the axis of rotation, preferably at least one of the loops being arranged at a different radial distance from the axis of rotation than another of the loop(s).

[0188] 29. The turbine according to any of the preceding items, wherein the conduit accommodates porous material and comprises two or more layers of porous material, each arranged respectively between at least two adjacent conduit walls.

[0189] 30. The turbine according to item 29, wherein the layers and conduit walls are arranged around the axis of rotation, such as concentrically and / or cylindrically, to form two or more loops around the axis of rotation.

[0190] 31 . The turbine according to any of the preceding items, wherein the porous material comprises one or more of aluminium, stainless steel, titanium, nickel, copper, bronze, zinc, magnesium, zirconium, cobalt, silver, lead, tantalum, and bismuth.

[0191] 32. The turbine according to any of the preceding items, wherein the porous material comprises an alloy of one or more of aluminium, titanium, nickel, copper, bronze, zinc, magnesium, zirconium, cobalt, silver, lead, tantalum, and bismuth.

[0192] 33. The turbine according to any of the preceding items, wherein the turbine is configured to operate with a working fluid selected from one or more of: xenon (Xe), ethane (C2H6), trifluoromethane (CHF3), fluoroform (CH3F), hexafluoroethane (CF3CF3), difluoromethane (CH2F2), R-410a, propane, perfluoropropane (CF3CF2CF3), ammonia (NH3), dimethyl ether (CH3OCH3), methyl trifluoromethyl ether (E143a), isobutane, sulfur dioxide (SO2), perfluorodimethylamine ((CF3)2NF), carbon dioxide (CO2), sulfur hexafluoride (SF6), and nitrogen dioxide (NO2). The turbine according to any one of items 3 to 33, wherein the upstream part of the conduit, such as an upstream part of a wall of the conduit, is made of a first material and the downstream part of the conduit, such as a downstream part of a wall of the conduit, is made of a second material, the first material having a higher melting and / or sintering point than the second material. The turbine according to any of the preceding items, wherein at least a part of the conduit configured to come into contact with a working fluid, such as one or more walls of the conduit, and / or a porous material of the conduit, has a melting and / or sintering temperature of 300 °C or more, such as 400 °C or more, such as 500 °C or more, such as 600 °C or more, such as 700 °C or more, such as 800 °C or more, such as 900 °C or more, such as 1000 °C or more, such as 1100 °C or more. The turbine according to item 29 or any item depending thereon, wherein each wall forming a boundary of at least one layer of porous material is made of a material having a different melting and / or sintering temperature.. The turbine according to item 29 or any item depending thereon, wherein a wall bounding a layer closer to the rotatable section inlet is made of a material having a higher melting and / or sintering temperature than a wall bounding a layer further downstream. The turbine according to item 29 or any item depending thereon, wherein the melting and / or sintering temperature of successive walls decreases with increasing distance from the rotatable section inlet. The turbine according to item 29 or any item depending thereon, wherein a first loop of the conduit accommodates a first porous material and a second loop of the conduit accommodates a second porous material, the first porous material having a higher melting and / or sintering temperature than the second porous material. 40. The turbine according to item 39, wherein porous material accommodated in a loop located further from the rotatable section inlet has a lower melting and / or sintering temperature than porous material accommodated in a loop located closer to the rotatable section inlet.

[0193] 41 . The turbine according to item 29 or any item depending thereon, wherein the same porous material is used within all loops of the conduit.

[0194] 42. The turbine according to item 29 or any item depending thereon, adjacent walls and / or porous materials accommodated within adjacent loops are made of materials having melting and / or sintering temperatures differing by 1 K or more, such as 2 K or more, such as 5 K or more, such as 10 K or more, such as 20 K or more, such as 40 K or more.

[0195] 43. The turbine according to any of the preceding items, wherein the conduit comprises one or more sub-walls within at least one conduit section, such as at least one loop of the conduit, the sub-walls extending partially or fully along the lengthwise extent of the conduit section and comprising apertures, such as perforations, openings, or slits, that allow pressure equalisation between layers of porous material separated by the sub-walls.

[0196] 44. A method of transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a working fluid into rotational kinematic or kinetic energy, the method comprising the steps of: a) providing a turbine according to any of the preceding items, and b) supplying the working fluid to the rotatable section inlet and passing the fluid through the conduit to cause the rotatable section to rotate about the axis of rotation and extract rotational kinematic or kinetic energy as the fluid flows through the porous material from the rotatable section inlet to the rotatable section outlet.

[0197] 45. The method according to item 44, wherein the turbine is operated as part of a Rankine cycle, preferably a transcritical or ultra-supercritical Rankine cycle.

[0198] 46. The method according to item 44, wherein the turbine is operated as part of a Brayton cycle, such as an open or closed Brayton cycle, or a combined cycle comprising a Brayton cycle and a Rankine cycle. 47. The method according to any one of items 44 to 46, wherein the working fluid has a critical temperature greater than ambient temperature.

[0199] 48. The method according to any of items 44 to 47, wherein the working fluid has a thermal decomposition temperature of 300 °C or more, such as 400 °C or more, such as 600 °C or more, such as 700 °C or more, such as 800 °C or more, such as 900 °C or more, such as 1000 °C or more, such as 1100 °C or more.

[0200] 49. The method according to any of items 44 to 48, wherein the turbine is operated in a cycle in which a pressure of the working fluid is always above ambient pressure, such as atmospheric pressure.

[0201] 50. The method according to any of items 44 to 49, wherein the turbine is operated at a maximum cycle temperature of 500 °C or less, such as 400 °C or less, such as 300 °C or less.

[0202] 51 . The method according to any of items 44 to 50, wherein the turbine is operated at a maximum cycle temperature of 300 °C or more, such as 500 °C or more, such as 700 °C or more, such as 900 °C or more.

[0203] 52. The method according to any of items 44 to 51 , wherein the turbine is operated at a cycle pressure of 20 bar or less, such as 10 bar or less, such as 5 bar or less.

[0204] 53. The method according to any of items 44 to 52, wherein the turbine is operated in a cycle in which the inlet temperature of the working fluid is higher than the critical temperature of the working fluid, such as at least 5% higher, such as at least 10% higher, such as at least 20% higher, such as at least 30% higher, such as at least 50% higher, such as at least 100% higher.

[0205] 54. The method according to any of items 44 to 53, wherein the turbine is operated in a cycle in which the inlet pressure of the working fluid is higher than the critical pressure of the working fluid, such as at least 50% higher, such as at least 100% higher, such as at least 150% higher, such as at least 200% higher.

[0206] 55. The method according to any of items 44 to 54, wherein the turbine is operated in a cycle in which the lowest pressure of the working fluid is 20 bar (absolute) or less, 10 bar (absolute) or less, such as 8 bar (absolute) or less, such as 6 bar (absolute) or less, such as 4 bar (absolute) or less. Use of a turbine according to any of items 1 to 44, or a method according to any of items 44 to 54, for converting energy stored in working fluid into useful work for driving a vehicle, generating electricity, operating a power plant, driving a pump, or powering an aircraft.

Claims

Claims1 . A turbine for transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a fluid into rotational kinematic energy of the turbine, the turbine comprising a rotatable section rotatable around an axis of rotation, the rotatable section comprising- a periphery surrounding the rotatable section,- a rotatable section inlet configured to receive a fluid under pressure,- a rotatable section outlet configured to emit the fluid, and- a conduit connecting the rotatable section inlet and the rotatable section outlet, wherein the conduit accommodates porous material and forms two or more loops around the axis of rotation.

2. The turbine according to claim 1 , wherein the rotatable section inlet is closer to the axis of rotation than to the periphery.

3. The turbine according to any of the preceding claims, wherein the conduit has an upstream part and a downstream part, wherein the downstream part is positioned further away from the axis of rotation than the upstream part.

4. The turbine according to any of the preceding claims, wherein the porous material is- a porous metal or a porous alloy,- carbon-based material,- ceramic,- silica-based material,- calcium silicate board,- refractory concrete, and / or- cement-based materials.

5. The turbine according to any of the preceding claims, wherein the conduit accommodates a second porous material in addition to the porous material, wherein the porous material is configured to withstand a first temperature, Ti,and the second porous material is configured to withstand a second temperature, T2, wherein Ti > T2.

6. The turbine according to claim 5, wherein the second porous material is accommodated downstream the conduit compared to the porous material.

7. The turbine according to any of the preceding claims, wherein the turbine comprises an initial rotatable section comprising- an initial rotatable section periphery rotatable around the axis of rotation,- an initial rotatable section inlet configured to receive a fluid under pressure, and- an initial rotatable section outlet configured to emit the fluid into the rotatable section inlet.

8. The turbine according to claim 7, wherein the initial rotatable section is configured to receive the fluid through the initial rotatable section inlet in an inlet direction that does not extend through the axis of rotation.

9. The turbine according to claim 7 or 8, wherein the initial rotatable section comprises (a) channel(s) and / or (a) blade(s), preferably curved channels or curved blades, configured to guide the fluid from the initial rotatable section inlet towards the initial rotatable section outlet.

10. The turbine according to claim 9, wherein the channel(s) and / or blades is / are configured to guide the fluid at least a part of a loop around the axis of rotation, preferably at least half a loop around the axis of rotation.11 . The turbine according to any of the preceding claims, wherein the turbine comprises a final rotatable section comprising- a final rotatable section periphery rotatable around the axis of rotation,- a final rotatable section inlet configured to receive the fluid from the rotatable section outlet, and- a final rotatable section outlet configured to emit the fluid.

12. The turbine according to any of the preceding claims, wherein the turbine comprises a first stationary part and a second stationary part, wherein the rotatable section is suspended by rotary bearings between the first stationary part and the second stationary part.

13. The turbine according to any of the preceding claims, wherein an initial crosssection area of the conduit at the rotatable section inlet is smaller than a final cross-section area of the conduit at the rotatable section outlet.

14. The turbine according to any of the preceding claims, wherein the conduit has two, a first porosity and a second porosity, or more different porosities, where the fluid may flow with more or with less resistance through the first porosity than through the second porosity.

15. The turbine according to any of the preceding claims, wherein the conduit at the rotatable section inlet has a lower porosity than at the rotatable section outlet.

16. The turbine according to any of the preceding claims, wherein the conduit comprises two or more layers of porous material, each arranged respectively between at least two adjacent conduit walls.

17. The turbine according to any of the preceding claims, wherein an upstream part of the conduit, such as an upstream part of a wall of the conduit, is made of a first material and a downstream part of the conduit, such as a downstream part of a wall of the conduit, is made of a second material, the first material having a higher melting and / or sintering point than the second material.

18. The turbine according to claim 16 or 17, wherein each wall forming a boundary of at least one layer of porous material is made of a material having a different melting and / or sintering temperature.

19. The turbine according to any of the preceding claims, wherein a wall bounding a layer closer to the rotatable section inlet is made of a material having a higher melting and / or sintering temperature than a wall bounding a layer further downstream.

20. The turbine according to any of the preceding claims, wherein a first loop of the conduit accommodates a first porous material and a second loop of the conduit accommodates a second porous material, the first porous material having a higher melting and / or sintering temperature than the second porous material.21 . The turbine according to any of the preceding claims, wherein the conduit comprises one or more sub-walls within at least one conduit section, such as at least one loop of the conduit, the sub-walls extending partially or fully along the lengthwise extent of the conduit section and comprising apertures, such as perforations, openings, or slits, that allow pressure equalisation between layers of porous material separated by the sub-walls.

22. A method of transforming fluid energy, such as pressure energy and / or fluid velocity and / or thermal energy, of a working fluid into rotational kinematic or kinetic energy, the method comprising the steps of: a) providing a turbine according to any of the preceding claims, and b) supplying the working fluid to the rotatable section inlet and passing the fluid through the conduit to cause the rotatable section to rotate about the axis of rotation and extract rotational kinematic or kinetic energy as the fluid flows through the porous material from the rotatable section inlet to the rotatable section outlet.

23. The method according to claim 22, wherein the turbine is operated as part of a Rankine cycle, preferably a transcritical or ultra-supercritical Rankine cycle.

24. The method according to claim 22 or 23, wherein the turbine is operated as part of a Brayton cycle, such as an open or closed Brayton cycle, or a combined cycle comprising a Brayton cycle and a Rankine cycle.

25. The method according to any one of claims 22 to 24, wherein the working fluid has a critical temperature greater than ambient temperature.

26. The method according to any of claims 22 to 25, wherein the working fluid has a thermal decomposition temperature of 300 °C or more, such as 400 °C or more, such as 600 °C or more, such as 700 °C or more, such as 800 °C or more, such as 900 °C or more, such as 1000 °C or more, such as 1100 °C or more.

27. The method according to any of claims 22 to 26 wherein the turbine is operated in a cycle in which a pressure of the working fluid is always above ambient pressure, such as atmospheric pressure.

28. The method according to any of items 22 to 27, wherein the turbine is operated in a cycle in which the inlet pressure of the working fluid is higher than the critical pressure of the working fluid, such as at least 50% higher, such as at least 100% higher, such as at least 150% higher, such as at least 200% higher.

29. Use of a turbine according to any of the preceding claims 1 to 21 for converting energy stored in working fluid into useful work for driving a vehicle, generating electricity, operating a power plant, driving a pump, or powering an aircraft.

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