METHOD FOR INCREASING AN ENTROPY FLOW IN A TURBOMACHINE

Description

[0001] The invention relates to a method for increasing the efficiency of a turbomachine, wherein a fluid guided through the turbomachine transfers kinetic energy to the turbomachine.

[0002] Thermodynamic cycles are used in many different ways in technology for energy conversion. In the most important processes for public energy supply, the majority of the energy used is still supplied by fossil energy sources that have been built up on Earth over millions of years through photosynthesis. This is becoming increasingly problematic with the increasing energy demand of humanity, as these energy resources cannot be replaced in the same quantities. Furthermore, the use of these energy forms causes significant environmental pollution. Therefore, these energy forms must increasingly be replaced by renewable energy forms. However, this is associated with a number of problems.

[0003] The two primary, virtually unlimited energy sources are nuclear fusion in the sun and nuclear fission in the Earth's interior (geothermal energy). They drive all energy cycles on Earth. This energy can then also be used secondarily, for example, as wind power, hydropower, or geothermal energy. The amounts of primary energy released annually are more than sufficient to meet human energy needs. However, they are not available everywhere and at all times. Furthermore, the development of renewable energy sources is often associated with high costs. The long energy payback time and the low harvest factor are one reason for the continued heavy use of fossil energy sources.

[0004] Energy conversion and storage processes, and their respective efficiencies, therefore play a crucial role. Currently, only chemical energy (e.g., methane or hydrogen) is suitable for storing large amounts of energy over extended periods (> 6 months). Although battery storage systems offer good efficiencies, their high costs and the rare materials required make them an alternative only for mobile devices or daily storage. Pumped-storage power plants can only be used in areas with large elevation differences. Thermal energy storage systems theoretically offer a high energy storage capacity per volume. However, converting this energy into other forms of energy requires large temperature differences. This also increases thermal losses. Thermal storage systems are therefore suitable for compensating for daily fluctuations in heat supply.They have little significance for the conversion into other forms of energy, as the efficiency of energy conversion is low.

[0005] Thermodynamic processes are primarily used for industrial energy supply, although the optimization potential of gas or steam power plants is limited. The maximum efficiency is limited by the maximum temperature achievable with the materials used and the ambient temperature. The problems associated with energy conversion using thermodynamic processes are particularly evident in compressed air storage power plants, which have not yet achieved commercial significance. When the air is compressed, the thermal energy is increased. Since the underground storage facilities used cannot be thermally insulated, this energy is lost to the environment. When energy is released, the compressed air expands again, leading to significant cooling and icing. In this case, the energy released during compression is missing and must be replaced, for example, by the combustion of natural gas.Since expansion is always required to release volume work, a high temperature difference is sought in all thermodynamic processes.

[0006] In thermodynamic processes, a distinction is made between clockwise (transfer of volume work, heat engine) and counterclockwise (refrigeration machines, heat pumps) processes.

[0007] In essence, thermal energy is the sum of the effects of various kinetic energy forms. The (internal) energy of a thermodynamic microstate consists of three essential components: the energy of translational motion E trans , the vibrational energy E vib , and the rotational energy E rot . Thus, each energy form can be assigned a corresponding share of the total entropy ( S ges = S vib + S red + S trans ) .

[0008] E vib is relatively small in gases and can usually be neglected. In monatomic gases, E trans dominates. In the liquid state, E trans = 0 and E rot dominate. In the solid state, rotation of the molecules is also not possible, and the total energy is determined by E vib. In polyatomic gases or at the interfaces between gases, liquids, and solids, these different kinetic energy forms interact. This results in a dynamic equilibrium between the kinetic energy forms.

[0009] Only the translational component (E trans ) of the internal energy can be directly used to perform volume work. However, if the translational momentum (p trans ) decreases, the energy and entropy of the vibration and rotation are transferred to the translational movement. The translational energy and entropy increase again and the vibration and rotation components decrease. The momentum determines the direction of the thermal energy flow. It correlates with the temperature. In clockwise thermodynamic processes, thermal energy is added and mechanical energy is released when the translational momentum of the molecules is high (high temperature). When the momentum is low (low temperature), thermal energy is removed and mechanical energy is added. Because of the energy-momentum relationship, more mechanical energy is released than is added. In a heat pump (counterclockwise), the process is inverse. This means that mechanical work must be added to the overall process.The ratio of the pulse intensity therefore also determines the efficiency.

[0010] The conversion of thermal energy into directed mechanical energy can occur with an isentropic change of state. However, the operating principles of a piston and a turbomachine are different. The force acting on a piston results from the average momentum of the molecules and the number of pulses (pressure). The molecules hit the piston at an average speed that corresponds approximately to the speed of sound. The average momentum is thus determined from the molecular mass and the speed of sound ( p = m * vs ) .When the piston moves during expansion, the relative speed drops below the speed of sound. Thus, the average effective momentum is always slightly below the momentum at the speed of sound. During compression, however, it is slightly above the momentum at the speed of sound, because the piston moves in the opposite direction.

[0011] Turbomachines are well known from the state of the art. In these, a compressible working medium is first accelerated using a confuser (nozzle). Unlike many other forms of energy, thermal energy does not have a directional vector in space. It acts in all spatial directions simultaneously. The confuser converts this undirected translational energy into directed lateral flow energy. However, this only allows the flow to be accelerated up to the speed of sound, since above this speed no translational energy is available for conversion. A Laval nozzle offers a solution for acceleration beyond the speed of sound. Here, the flow cross-section is increased again after the speed of sound is reached. The volume work released in this process enables further lateral acceleration. One disadvantage is the reduction in entropy due to the cross-sectional expansion of the Laval nozzle.An alternative is described in DE 10 2014 004 237 A1. In this method, a mixture of gas and liquid is mixed and accelerated. By adding rotational and vibrational energy from the liquid, the multiphase flow can be accelerated beyond its speed of sound without expanding its cross-section. The higher speed is made possible by the energy equation. E = m / 2 * v 2< a higher amount of energy delivered and thus a higher efficiency compared to a piston engine. A similar process is described in DE 10 2012 108 222 A1. Here, too, a multiphase flow (air / water) is accelerated to supersonic speed. The water content increases the mass of the flow and compensates for the reduction in translational energy by supplying rotational and vibrational energy of the water molecules.

[0012] A less considered problem in fluid machines is the acceleration of molecules after the fluid machine. Fig. 1 The molecules move with the velocity v 1 in the flow channel (see Fig. 1 ). When they encounter the fluid machine (4), they transfer a large portion of their lateral kinetic energy to the fluid machine and continue to move at a speed v 2 . Since the speed v 2 is very low due to the energy transfer, the speed of sound (v S ) dominates the molecular motion. This also creates a force F 2 acting against the flow direction. This force is influenced by the intensity and number of molecular impulses against the flow direction and limits the efficiency of the fluid machine.

[0013] To reduce the force and increase efficiency, thermal energy is transferred to an external reservoir. This lowers the temperature and thus the intensity of the molecular momentum. However, to significantly reduce the intensity, a large amount of thermal energy and entropy must be transferred. In the Clausius-Rankine or Organic-Rankine process, the translational velocity is reduced to zero through condensation. However, the entire translational energy and, in the case of polyatomic molecules, a portion of the vibrational and rotational energy must be transferred.

[0014] DE 26 54 097 A1 describes the operation of a clockwise cycle below ambient temperature. However, this poses the problem of dissipating thermal energy to the environment. The author proposes a heat pump as a solution. However, he does not explain why this heat pump would require less drive energy than the additional energy released by the higher temperature difference in the clockwise cycle. Due to thermal and friction losses in the heat pump, additional thermal energy must be dissipated, which, according to the law of conservation of energy, reduces the useful energy of the overall system.

[0015] DE 10 2017 127 716 A1 describes a process for cooling by isothermal compression. The process utilizes gravitational force for isothermal compression. However, the turbomachine is not located in the flow channel of the multiphase flow, and the goal of the process is compression upstream of the turbomachine. Due to the low entropy flow at the turbomachine compared to the multiphase flow, the process is not intended for generating mechanical energy, but rather for cooling.

[0016] DE 195 33 249 C1 describes a turbomachine for generating mechanical work from thermal energy. It comprises, in a working chamber, a first section connected to a heat source as an evaporation section for evaporating a liquid working fluid, and a second section connected to a heat sink as a condensation section for condensing the evaporated working fluid. In a conversion device connecting the evaporation section and the condensation section, the kinetic energy of the vaporous working fluid flowing at high velocity from the evaporation section to the condensation section due to a high pressure gradient is converted into mechanical work. A recirculation device serves to recirculate the condensed working fluid from the condensation section to the evaporation section.

[0017] US Pat. No. 4,485,629 A discloses a method for storing mechanical or thermal energy in chemical form and recovering the stored energy in mechanical form. The device comprises chambers for containing a non-ideal solution of a vapor and a liquid, and chambers for containing liquefied vapors separated from the non-ideal solution. These chambers are in close thermal contact and their volumes are connected by conduits to a motor for recovering the stored energy during the recovery phase.

[0018] US 2019 / 128148 A1 discloses a method and a system for the efficient use of thermal energy to provide kinetic energy and / or electrical energy. The method uses at least two heat exchangers to heat the working medium: a heat engine and a condenser. The working medium consists of at least two substances. The working medium is partially condensed on the primary side of the first heat exchanger, whereby heat is transferred to the working medium flowing on the secondary side, and further condensation heat is subsequently released to a cooling circuit in a condensation heat exchanger on the primary side of the condensation heat exchanger. The working medium is then redirected to the secondary side of the first heat exchanger. Gaseous components of the working medium are separated in the primary-side condensation heat exchanger.

[0019] AT 506 353 A1 describes a jet compressor heat engine in which a jet compressor is arranged in a heat engine circuit, with the help of whose propulsion jet a medium emerging from an expansion machine can be sucked in and compressed and collected in a collecting vessel, from which a line leads to a pump and another line can lead to the jet compressor.US 3 972 195 A relates to a two-phase energy source comprising a rotor, a nozzle having an outlet directed to deliver a two-phase jet impinging on the rotor to rotate it, the nozzle having means for dividing the flow therein and means for supplying a heated first fluid in a liquid state to the nozzle for a divided flow therein towards the outlet and for supplying a second and vaporizable fluid in a liquid state to the nozzle to absorb heat from the first fluid therein, causing the second fluid to vaporize in the nozzle and mix with the first fluid in a substantially liquid state to produce the outgoing jet.

[0020] The object of the invention is to increase the efficiency of a turbomachine. This object is achieved according to the invention with a method having the features of claim 1. Advantageous embodiments of the method are set forth in claims 2 to 5.

[0021] The method according to the invention provides that a flow of a compressible fluid is fed to a turbomachine. At the turbomachine, kinetic energy of the fluid is transferred to the turbomachine. After a polytropic expansion at the turbomachine, the flow velocity of the fluid downstream of the turbomachine, which was reduced at the turbomachine during the transfer of kinetic energy, is increased by a force FB generated by a force field and acting in the direction of flow by converting potential energy of the fluid into kinetic energy of the fluid to such an extent that the pressure of the fluid reduced at the turbomachine is increased again to at least 0.1 times the pressure of the fluid upstream of the turbomachine. Technically, the increase in the pressure of the fluid downstream of the turbomachine is of course limited to the pressure of the fluid upstream of the turbomachine.The force FB in the flow direction is generated by a force field, such as a gravitational field, a centrifugal field, a magnetic field, or an electric field. The change in the position of the molecules along the flow direction converts the potential energy of the field into kinetic energy.

[0022] In the method according to claim 1, the force FB acts in the direction of flow, partially or completely compensating for a thermodynamic force F 2 acting against the direction of flow. The increase in the flow velocity of the fluid downstream of the turbomachine by the force FB causes the pressure of the fluid to increase further in the flow downstream of the turbomachine. The resulting reduction in pressure in the fluid directly downstream of the turbomachine increases the efficiency of the polytropic expansion at the turbomachine. The molecules of the fluid are accelerated by the force FB to a velocity v 2. If the fluid is a gas, for example, the velocity v 2 should be at least 0.3 times the speed of sound of the fluid. FB is therefore on the order of magnitude of F 2 .For a mixture of two gases, the velocity v 2 should be at least 0.3 times the weighted average of the speeds of sound of the two gases. The acceleration of the fluid molecules downstream of the turbomachine has a significant influence on its efficiency. The goal of the acceleration is to reduce the pressure and thus the force against the flow direction directly downstream of the turbomachine. The higher the acceleration downstream of the turbomachine, the greater the influence of the inventive method on the efficiency of the turbomachine, although the increase in the flow velocity downstream of the turbomachine is naturally limited to the flow velocity upstream of the turbomachine.Compared to a flow velocity of 0.3 times the speed of sound of the fluid, higher efficiencies are achieved for the efficiency of the turbomachine if the flow velocity after the turbomachine is accelerated, for example, to 0.5 times or 0.6 times or 0.8 times or simply the speed of sound of the fluid, whereby the flow velocity before the turbomachine is then at least approximately 0.51 times or 0.61 times or 0.81 times or 1.01 times the speed of sound of the fluid.

[0023] If, on the other hand, the fluid is formed from a gas and a liquid, the velocity v 2 should be so high that the translational velocity of the molecules of the gas (compressible fluid portion) is at least 0.3 times the speed of sound of the gas.

[0024] In prior art processes, flow acceleration is achieved by dissipating thermal energy and entropy to the environment. In the process according to the invention, the dissipation of thermal energy required for acceleration is to be eliminated entirely or at least significantly reduced by generating the acceleration of the fluid molecules with the force FB acting in the direction of flow through a force field. The force FB is independent of the molecule's state of motion and can thus accelerate even molecules with high kinetic energy. Higher kinetic energy and the associated higher kinetic momentum of the molecules enable the dissipation of thermal energy to an external reservoir (energy sink) with higher intensity (temperature) after acceleration.

[0025] According to the invention, the compressible fluid is accelerated by a nozzle (confuser) upstream of the turbomachine in the flow direction. A diffuser is located downstream of the turbomachine in the flow direction.

[0026] The compressible fluid is thus initially accelerated at the confuser, whereby translational kinetic energy of the molecules (E trans ) is converted into lateral kinetic energy (E lat ) and vibration and rotation energy (E vib , E rot ) of the fluid molecules is converted into translational energy (E trans ), whereby the fluid flow is accelerated to a velocity (v 1 ). This also increases the translational entropy component (S trans ). Energy and momentum are released at the turbomachine, so that the velocity of the fluid flow is again significantly reduced. The force FB in the flow channel then accelerates the molecules of the fluid downstream of the turbomachine to a velocity v 2 . In the diffuser and / or compressor, the volume-effective energy and entropy component (E trans , S trans ) then decreases through conversion into vibration and rotation energy. This component does not have to be dissipated externally.Complete compensation of F 2 would require accelerating the molecules to the speed of sound. A significant increase in the efficiency of the turbomachine is achieved for a velocity v 2 of 0.3 times the fluid's speed of sound. Upon acceleration to one-times the speed of sound, a vacuum is created directly behind the turbomachine. In the diffuser, part of the lateral kinetic energy is converted back into undirected thermodynamic motion, with an increase in temperature and pressure. This means less or no thermal energy needs to be dissipated to the environment, which reduces global warming caused by thermodynamic processes. The flow then continues at a low lateral velocity (v 3 ).

[0027] The lateral velocity (v 1 ) of the molecules in front of the flow machine should be higher than the speed of sound. At higher speeds, E= m / 2 * v2< more energy is released than is required to accelerate the molecules with FB to the speed of sound. Fundamentally, acceleration above the speed of sound is based on the principle of relativity. In the confuser, the translational motion of the molecules is converted into lateral motion in the direction of flow. However, the average speed compared to an observer outside the flow remains constant. This means that, despite the reduced temperature, no additional energy can be supplied from outside. However, with regard to the vibrational and rotational energy carried in the flow, the intensity of the translational motion of the molecules decreases. This results in an energy transfer from the vibrational and rotational energy to the translational energy, which can then be used in addition to the lateral acceleration.The lateral velocity can thus be higher than the average translational velocity (speed of sound) at the entrance of the confuser. This allows energy to be supplied at a lower intensity (momentum, temperature). This increases the efficiency and energy efficiency of the process.

[0028] With negative acceleration in the diffuser, the energy flow acts in the opposite direction. The lateral kinetic energy is converted into a disordered translational movement of the molecules, increasing their intensity. This allows a portion of the translational energy to be converted into vibrational and rotational energy. If thermal energy is dissipated to the environment, the vibrational and rotational energy must also be dissipated. However, if the flow is further accelerated beforehand by the external force FB, the proportion of volume-independent vibrational and rotational energy increases. Therefore, more energy can be stored in the flow and released again upon further acceleration.

[0029] The ratio of vibrational and rotational energy to translational energy is described by the isentropic coefficient. Therefore, the fluid should have at least one fluid component with an isentropic coefficient of less than or equal to 1.4 in the operating temperature range. Higher efficiency is achieved with a fluid whose at least one fluid component has an isentropic coefficient of less than or equal to 1.2. The efficiency is even higher with an isentropic coefficient of less than or equal to 1.1.

[0030] The fluid can be a gas or a multiphase flow, whereby in the context of the application, multiphase flow is understood to include both gas mixtures and mixtures of gas and liquids. In a multiphase flow, substances with a high isentropic coefficient (cp / c V ) should be mixed with substances with a low isentropic coefficient (e.g. helium / n-butane). The non-volume-dependent portion of the thermal energy (vibrational and rotational energy) should have a high heat capacity in relation to the translational energy. In principle, it is also possible to calculate an isentropic coefficient (cp / c V ) for liquids. This is approximately 1. The advantage of gas mixtures is the better energy exchange due to the larger effective surface area of the individual molecules. For pure substances (fluid consisting of a gas), the proportion of vibrational and rotational energy is determined by the molecular structure.Therefore, gases with a very low isentropic coefficient and high molecular mass should be used. Multiphase flow consisting of a gaseous and a liquid fluid component can also be used, whereby, to generate the pressure reduction downstream of the turbomachine, the velocity v 2 should be so high that the translational velocity of the gas molecules (compressible fluid component) is at least 0.3 times the speed of sound of the gas.

[0031] In a further development of the process, a fluid mixture is used as the working medium. A fluid with a high vapor pressure is combined with a fluid with a low vapor pressure. The pressure at the inlet of the confuser is selected so that both fluids are liquid (vibrational and rotational energy). If the pressure drops during acceleration in the confuser, the fluid with the higher vapor pressure reaches its boiling point. By transferring vibrational and rotational energy from the fluid with the low vapor pressure, the fluid with the high vapor pressure is completely evaporated. The described physical effect of evaporation is also the basis of cavitation, which is usually to be avoided in turbomachines. In the process according to the invention, however, this effect is deliberately amplified in order to achieve a high acceleration of the flow.The now compressible fluid (with translational energy) is strongly accelerated in the flow channel due to the increase in volume, transferring energy and momentum to the turbomachine. Due to the pressure increase in the diffuser and / or compressor, the condensation point is reached, and the compressible portion of the fluid transfers its translational energy to the incompressible portion of the fluid (vibrational and rotational energy).

[0032] An alternative development can also be implemented using a reversible chemical process. A gas dissolved in a liquid is fed into the confuser. If the pressure in the confuser decreases during acceleration, the reaction equilibrium changes, and gas escapes from the solution. This provides translational energy for high acceleration. The compressible fluid transfers energy and momentum to the fluid machine. Due to the pressure increase in the diffuser and / or compressor, the reaction equilibrium changes again, and the gas dissolves in the liquid through the chemical reaction. Translational energy is converted into vibration and rotation energy.

[0033] The externally supplied energy for FB can be supplied, for example, by a gravitational force, a magnetic force, an electrical force, or a centrifugal force. Likewise, a mechanical force can be provided by another turbomachine powered by externally supplied energy, in which case this turbomachine is arranged downstream of the diffuser in the flow direction.

[0034] Table 1 shows a comparison of the acceleration times and distances due to the gravitational force on Earth (~9.81 m / s 2< ) in free fall from zero to the speed of sound (vs ) for different substances at normal pressure and temperature (1 bar; 300 K). Table 1 Material vs (m / s) t (s) s (m) helium 1020 104 53028 Nitrogen 353 36 6351 Carbon dioxide 269 27 3688 xenon 174 18 1543 Water / air mixture 10 1 10

[0035] The table shows that gravitational force is particularly suitable for media with very heavy molecules and for multiphase flows. Since acceleration of the fluid in the diffuser at 0.3 times the speed of sound increases the pressure and temperature, the process can also be operated below ambient temperature. At lower temperatures, shorter acceleration distances and acceleration times are possible due to the lower speed of sound. For a mixture of water and air with a high mass fraction of water, the water pressure increases from 0 bar to 1 bar at a drop height of 10 m. This also compresses the air molecules to this pressure and causes them to move at the speed of sound. The overall flow, in contrast, has a much lower speed of sound. A drop height of 10 m is therefore sufficient to create a vacuum behind the working machine.In a gravitational diffuser, the velocity of the molecules in or in front of the diffuser can therefore be increased. This reduces the lower pressure during isentropic expansion and increases the efficiency of the thermodynamic process.

[0036] Stronger forces than those caused by gravity can be generated using centrifugal force. This shortens the acceleration paths and thus the dimensions of the thermodynamic machine. For this purpose, the thermodynamic machine is constructed to be rotationally symmetrical and rotates about its axis of rotation. The rotation creates an inhomogeneous phase space. The expected value (set mean) increases with the distance from the axis of rotation and with it the pressure, temperature and density. If the tangential velocity is around the speed of sound, a near vacuum forms at the axis of rotation. The compressor compensates for process losses (e.g. friction) and does not have to perform a lot of volumetric work. It pushes the working fluid into the confuser where it is accelerated. Additional acceleration is caused by the thermodynamic force with the centrifugal force FZ decreasing in the direction of flow.In the turbomachine, kinetic energy is extracted from the molecules at high speed. The molecules are then accelerated in the flow direction by the FZ. In the diffuser, the pressure and temperature increase. Thermal energy (Q 2 ) can optionally be removed upstream of the compressor using a heat exchanger. Thermal energy (Q 1 ) is added downstream of the compressor. This reduces the volumetric work at the compressor. The thermal energy can be transported via the wall of the flow channel by heat conduction or by a fluid in a parallel flow channel.

[0037] A thermodynamic machine with a centrifugal condenser and centrifugal diffuser allows molecules to be accelerated laterally beyond the speed of sound by changing the centrifugal force. Homogeneous materials as well as multiphase flows can be used. Using multiphase flows with different isentropic coefficients reduces the temperature change, and a higher incompressible component (rotational and vibrational energy) can reduce the tangential velocity and thus the radius. The translational component of the entropy flow increases during acceleration, thus also leading to a higher lateral velocity at the fluid machine.

[0038] Depending on the application, the turbomachine can be a turbine or an MHD generator.

[0039] In principle, however, the method according to the invention is suitable for increasing the efficiency of any polytropic expansion. During expansion in a piston engine, the energy is extracted at the speed of sound, and the acceleration energy is supplied in the flow channel at relative velocities below the speed of sound. However, in turbomachines, a greater effect can be expected due to the higher achievable relative speed when releasing mechanical energy. Furthermore, due to the discontinuous operation of piston engines, several pistons must be operated in parallel and out of phase to create a continuous flow in the flow channel.

[0040] Exemplary embodiments of the invention are explained below with reference to the drawings. They show: Fig. 1 a flow of a fluid with a turbomachine according to the prior art Fig. 2 an arrangement for using the method according to the invention Fig. 3 another arrangement for using the method according to the invention Fig. 4 a thermodynamic cycle with a centrifugal confuser and a centrifugal diffuser Fig. 5 a gravitational diffuser Fig. 6 a thermodynamic cycle with MHD generator

[0041] Fig. 1shows a fluid flow with a turbomachine 1 according to the prior art. The turbomachine 1 is depicted as an impeller. The fluid flow transfers a portion of its kinetic energy to the turbomachine 1, where it is dissipated as work. The molecules M of the fluid move at a velocity v 1 in the flow channel and transfer a portion of their lateral kinetic energy to the turbomachine at the impellers of the turbomachine, then continue to move at a velocity v 2.

[0042] In the Fig. 2An arrangement for using the method according to the invention to increase an entropy flow in a turbomachine 1 is shown. For this purpose, a compressible fluid is polytropically expanded in the turbomachine 1, which is designed as a turbine. After the polytropic expansion, an additional force FB acts on the molecules M of the fluid in the direction of flow, so that the molecules M are accelerated in the direction of flow by this force. The force FB acting in the direction of flow is generated by a force field, whereby the potential energy of the fluid is converted into kinetic energy of the fluid.This force FB accelerates the molecules M of a fluid consisting of gas or a gas mixture downstream of the turbomachine to at least 0.3 times the speed of sound of the fluid, so that the pressure of the fluid reduced at the turbomachine is increased again to at least 0.1 times the pressure of the fluid upstream of the turbomachine, and thus the pressure reduction necessary to increase the efficiency of the turbomachine is achieved directly downstream of the turbomachine. In the embodiment shown, the force FB can be the gravitational force, for example. For a fluid consisting of a mixture of gas and liquid, the pressure reduction is achieved directly downstream of the turbomachine if the velocity v 2 of the fluid is at least high enough that the translational velocity of the molecules M of the gas (compressible fluid portion) is at least 0.3 times the speed of sound of the gas.

[0043] Fig. 3shows a further arrangement for utilizing the method according to the invention. A confuser 2 is arranged upstream of the polytropic expansion on the turbomachine 1, so that the compressible fluid is accelerated upstream of the turbomachine 1. A diffuser 3 is arranged downstream of the turbomachine 1 in the direction of flow. Depending on the desired increase in efficiency for the turbomachine, the acceleration at the confuser upstream of the turbomachine can, for example, be up to 0.31 times, 0.51 times, 0.61 times, 0.81 times, or 1.01 times the speed of sound of the fluid. Downstream of the turbomachine, the fluid is then accelerated again as close as possible to the flow velocity value upstream of the turbomachine (0.3 times, 0.5 times, 0.6 times, 0.8 times, or 1 time the speed of sound of the fluid). A compressor 5 is arranged downstream of the diffuser 3, although this is optional here.In a further embodiment not shown, the compressor 5 is provided instead of the diffuser 3. The fluid can be present as a pure substance (a gas), a gas mixture, or a mixture of gas and liquid, and the force FB can be, for example, the gravitational force.

[0044] Fig. 4a and Fig. 4bshow two arrangements for using the method according to the invention in a thermodynamic cycle with a centrifugal confuser and a centrifugal diffuser. A flow channel containing a fluid is set in rotation about a rotation axis 4. As a result, a centrifugal force FZ acts on the fluid and causes the density of the fluid to increase with the distance from the rotation axis 4. A compressor 5 is mounted at the location with the highest rotation speed. The turbomachine 1 is arranged on the rotation axis 4. The fluid is first accelerated in the confuser 2 and releases energy and momentum to the turbomachine 1. After the turbomachine 1, the fluid is accelerated by the increasing centrifugal force and the pressure in the diffuser 3 is increased again. Here, too, the molecules M of the fluid are accelerated to at least 0.3 times the speed of sound of the fluid. Thermal energy Q 1 can be supplied between the compressor 5 and the confuser 2.Optionally, thermal energy Q 2 is dissipated between diffuser 3 and compressor 2. In the design according to . Fig. 4a the turbomachine 1 is arranged radially to the rotation axis. In Fig. 4bIn an alternative embodiment, the turbomachine 1 is arranged axially to the rotation axis. Here, too, the fluid can be a pure substance (a gas), a gas mixture, or a mixture of gas and liquid. In the case of a fluid consisting of gas or a gas mixture, the fluid downstream of the turbomachine is accelerated to at least 0.3 times the speed of sound of the fluid, so that the pressure of the fluid reduced at the turbomachine is increased again to at least 0.1 times the pressure of the fluid upstream of the turbomachine, thus achieving the pressure reduction required to increase the efficiency of the turbomachine directly downstream of the turbomachine.In a fluid consisting of a mixture of gas and liquid, the pressure reduction is achieved directly after the turbomachine when the velocity v 2 of the fluid is at least high enough that the translational velocity of the molecules M of the gas (compressible fluid fraction) is at least 0.3 times the speed of sound of the gas.

[0045] In the illustrated embodiment, the force FB is provided by the centrifugal force FZ. The described thermodynamic machine, with a centrifugal condenser and centrifugal diffuser, is therefore also suitable for use in locations with low gravity (e.g., in space).

[0046] In one embodiment, the arrangements according to Fig. 3 or Fig. 4a / 4ba multiphase flow is used which works with a phase change (evaporation / condensation) of a component or a reversible chemical reaction. If, for example, a mixture of water and isobutane is fed into confuser 2 at 4 bar and 300 K, both components are liquid. The acceleration in confuser 2 causes the pressure to drop and the isobutane reaches its boiling point. By adding rotational and vibrational energy (of the molecules M) to the liquid water, it can evaporate. The increase in volume accelerates the flow even further. Part of the kinetic energy is released at turbomachine 1. The flow is then accelerated laterally by gravitational force or centrifugal force. Due to the increased pressure in diffuser 3 and / or in the downstream compressor 5, the gas condenses with a significant reduction in volume.However, the energy released does not have to be dissipated externally, but is stored in the circuit in the form of volume-independent vibration and rotation energy.

[0047] When using a water-carbon dioxide mixture, the carbon dioxide dissolves in the water and reacts to form carbonic acid. When the pressure drops in confuser 2, the equilibrium of the solution decreases, and gaseous carbon dioxide escapes into the flow channel, accelerating the flow. Since a concentration equilibrium is established in the solution, a uniform gas discharge is to be expected. After the energy is released at the turbomachine and acceleration in the flow channel, the gas returns to solution due to the pressure increase in diffuser 3 and / or the downstream compressor 5, reducing the volume of the multiphase flow. Carbon dioxide then reacts with the water to form carbonic acid.

[0048] The selection of components significantly influences the operating pressure. For substances with low vapor pressure (e.g., isopropanol / water mixtures), the pressure upstream of confuser 2 can be less than 1 bar. This simplifies the design. Due to the high density of liquid water, the energy density and entropy flow are still very high. This allows for very high speed and energy output at the turbomachine with compact dimensions.

[0049] Fig. 5shows a gravitational diffuser as a further arrangement for utilizing the method according to the invention. A fluid is accelerated in the confuser 2 and fed to the turbomachine 1. The flow channel and diffuser 3 are arranged in the direction of gravity, whereby the gravitational force FG acts as force FB and accelerates the molecules M of the fluid by converting potential energy into kinetic energy. The machine is dimensioned such that the volume between compressor 5 and confuser 2 is larger than the volume between turbomachine 1 and compressor 5. Alternatively, a pressure equalization vessel 6 can be attached. The compressor 5 thus generates a negative pressure at the turbomachine 1, which increases the efficiency. Thermal energy Q 1 is supplied between the compressor 5 and the confuser 2. Optionally, thermal energy Q 2 can be dissipated between the diffuser 3 and the compressor 5.

[0050] Since in turbomachines 1 only the relative velocity of the flow is relevant for the energy supply, energy can be extracted in a narrow flow channel at high velocity with a turbomachine 1 and supplied in a wider flow channel at low velocity. E = m / 2 * v2< more energy is released at high speed than is supplied at low speed. The mechanical force (F m ) supplied by the compressor 5 acts like the gravitational force F g and reduces the pressure downstream of the turbo machine 1. For this purpose, the pressure equalization vessel 6 is installed between the compressor 5 and the confuser 2, which keeps the pressure at the inlet of the confuser 2 constant. With compressible media, pressure equalization can also be achieved by a large volume upstream of the confuser 2 compared to the volume between the diffuser 3 and the compressor 5. In open processes, the surrounding atmosphere can take over pressure equalization. If mechanical work is supplied to the compressor 5, the pressure at the outlet of the diffuser 3 drops. This allows the pressure at the outlet of the turbo machine 1 to drop to almost zero, which enables high flow velocities and therefore high efficiency.For this to happen, sufficient energy must be available for acceleration in confuser 2, which can be provided by a high proportion of vibration and rotation energy (in the case of complex molecules M or multiphase flows). This accelerates the fluid to supersonic speed even without a Laval nozzle. Since the thermal energy Q 1 does not have to be supplied at a high temperature, but is only transferred when the relative translational speed of the molecules M within the flow is reduced, the volume-effective heat capacity and thus the entropy flow IS at the working machine 1 increases. Because of . P = T * IS (P = power, T = temperature, entropy flow) the power P increases at constant input temperature.

[0051] The compressor 5 should be located near the lowest point in the cycle. The energy W 2 required to operate the compressor 5 can be supplied partially or entirely by the mechanical energy W 1 released by the turbomachine 1.

[0052] The arrangement pursuant to Fig. 5The fluid used can be a pure substance (a gas), a gas mixture, or a mixture of gas and liquid. In the case of a fluid consisting of a gas or a gas mixture, the fluid downstream of the turbomachine is accelerated to at least 0.3 times the speed of sound of the fluid, so that the pressure of the fluid reduced at the turbomachine is increased again to at least 0.1 times the pressure of the fluid upstream of the turbomachine, and thus the pressure reduction necessary to increase the efficiency of the turbomachine is achieved directly downstream of the turbomachine. In the case of a fluid consisting of a mixture of gas and liquid, the pressure reduction is achieved directly downstream of the turbomachine when the velocity v2 of the fluid is at least high enough that the translational velocity of the molecules M of the gas (compressible fluid portion) is at least 0.3 times the speed of sound of the gas.

[0053] Fig. 6 shows a thermodynamic cycle with a turbomachine configured as an MHD generator as a further arrangement for utilizing the method according to the invention. A mixture of an electrolyte (e.g., ionized solution) and a compressible fluid is used as the working medium. The mixture is accelerated in the confuser 2 and flows through a magnetic field of the turbomachine 1 configured as an MHD generator. The charge carriers of the electrolyte are deflected to the left or right, and the electrical energy is dissipated via the electrodes. In the diffuser 3, the flow velocity is slowed, converting translational energy into vibration and rotational energy.

[0054] The fluid is compressed in compressor 5 and flows back to confuser 2. The volume between compressor 5 and confuser 2 must be larger than the volume between the MHD generator and compressor 5. Alternatively, a pressure equalization vessel 6 can be installed. This allows compressor 5 to generate a negative pressure behind the MHD generator, which accelerates the flow and increases efficiency. Thermal energy Q 1 is supplied upstream of confuser 2. Optionally, thermal energy Q 2 can be dissipated downstream of diffuser 3.

[0055] One advantage of this arrangement is the higher achievable magnetic field strength in the narrow flow channel compared to the expanded flow channel of a Laval nozzle. Furthermore, the charge carrier density of the electrolyte is high, allowing for compact machine dimensions. Unlike using an ionized gas, the process can also take place at ambient temperature, reducing material requirements and costs. List of reference symbols

[0056] MMolecule 1Fluid machine 1.1Housing 2Confusor 3Diffuser 4Rotation axis 5Compressor 5.1Compressor 5.2Compressor 6Expansion vessel

Claims

1. Method for operating a turbomachine (1), wherein a fluid guided through the turbomachine (1) transmits kinetic energy to the turbomachine (1), the fluid, or at least one fluid component of the fluid, is compressible, and the compressible fluid is accelerated upstream of the turbomachine (1) in the direction of flow in a convergent nozzle (2), and a divergent nozzle (3) is arranged downstream of the turbomachine in the direction of flow, and the flow velocity of the fluid, which is reduced in the turbomachine (1) during the transmission of the kinetic energy, is increased directly downstream of the turbomachine (1) by a force FB, generated by a force field and acting in the direction of flow, by converting potential energy of the fluid into kinetic energy of the fluid to such an extent that the pressure of the fluid, which is reduced in the turbomachine (1), is thereby increased again to at least 0.1 times the pressure of the fluid upstream of the turbomachine (1), wherein the force FB acting in the direction of flow is the gravitational force, a centrifugal force, a magnetic force, an electrical force or a mechanical force provided by a further turbomachine.

2. Method according to claim 1, wherein the fluid is a multiphase flow and at least one fluid component is gaseous and another fluid component of the fluid is liquid.

3. Method according to claim 1, wherein a fluid mixture consisting of a first fluid and a second fluid is used as the compressible fluid, and the first fluid has a lower vapour pressure than the second fluid, and the first fluid is liquid both during acceleration at the convergent nozzle (2) and downstream of the turbomachine (1), and the second fluid is at least partially gaseous during acceleration at the convergent nozzle (2) and liquid downstream of the divergent nozzle (3).

4. Method according to claim 1, wherein a fluid mixture consisting of a first medium and a second medium is used as the compressible fluid, wherein the first medium is a gas and the second medium is a liquid, and wherein the first medium and the second medium are selected in such a way that the first medium is dissolved in the second medium before acceleration at the convergent nozzle (2), and the first medium is released from the solution as a gas during acceleration of this solution at the convergent nozzle (2) as a result of a drop in the pressure in the convergent nozzle (2), and is dissolved again in the second medium downstream of the diffuser (3) as a result of an increase in pressure.

5. Method according to one of the preceding claims, wherein the turbomachine (1) is a turbine or a magnetohydrodynamic generator.