METHOD FOR INCREASING AN ENTROPY FLOW IN A TURBOMACHINE

Abstract

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. The object of the invention is to increase the efficiency of a turbomachine. This object is achieved in that the fluid or at least one fluid component of the fluid is compressible, and that the flow velocity of the fluid reduced in the turbomachine (1) during the transfer of kinetic energy is increased directly downstream of the turbomachine (1) by a force F.sub.B generated by means of 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). (FIG. 2)

Claims

1. A method for increasing the efficiency of a turbomachine, wherein a fluid guided through the turbomachine transmits kinetic energy to the turbomachine, characterised in that the fluid or at least one fluid component of the fluid is compressible, and in that the flow velocity of the fluid, which is reduced in the turbomachine during the transmission of the kinetic energy, is increased directly downstream of the turbomachine 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, is thereby increased again to at least 0.1 times the pressure of the fluid upstream of the turbomachine.

2. A method for increasing the efficiency of a turbomachine, wherein a fluid guided through the turbomachine transmits kinetic energy to the turbomachine, characterized in that the fluid has two fluid components and at least one fluid component of the fluid is compressible, and in that, in the working temperature range, the ratio cp/cV of the second fluid component is at least 1.1 times the ratio cp/cV of the first fluid component, and in that the fluid components are separated downstream of the turbomachine in a separator, and in that the first fluid component is accelerated and/or compressed downstream of the separator in a first compressor and the second fluid component is accelerated in a second compressor downstream of the separator, and in that, downstream of the first and second compressors, the two fluid components are combined again in a mixer and in that the mass flows of the fluid components are dimensioned in such a way that an entropy flow IS1 of the first fluid component at the first compressor is greater than an entropy flow IS2 of the second fluid component at the second compressor and an entropy flow downstream of the mixer at the inlet of the turbomachine is the sum of IS1 and IS2.

3. The method of claim 1, wherein the compressible fluid is accelerated in a nozzle in the direction of flow upstream of the turbomachine.

4. The method of claim 1, wherein a divergent nozzle and/or a compressor is arranged downstream of the turbomachine in the direction of flow.

5. The method of 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.

6. The method of claim 1, wherein a fluid mixture consisting of a first fluid and a second fluid is used as the compressible fluid and that the first fluid has a lower vapour pressure than the second fluid, and that the first fluid is liquid both during acceleration at the convergent nozzle and downstream of the turbomachine, and that the second fluid is at least partially gaseous during acceleration at the convergent nozzle and liquid downstream of the divergent nozzle.

7. The method of claim 1, wherein a fluid mixture consisting of a first fluid and a second fluid is used as the compressible fluid, wherein the first fluid is a gas and the second fluid is a liquid, and in that the first fluid is dissolved in the second fluid before acceleration at the convergent nozzle, is released from the second fluid during acceleration at the convergent nozzle and is dissolved again in the second fluid downstream of the divergent nozzle.

8. The method of claim 1, wherein the force FB acting in the direction of flow is a gravitational force, a centrifugal force, a magnetic force, an electrical force or a mechanical force provided by a further turbomachine.

9. The method of claim 1, wherein the turbomachine is a turbine or an MHD generator.

10. The method of claim 2, wherein the compressible fluid is accelerated in a nozzle in the direction of flow upstream of the turbomachine.

11. The method of claim 2, wherein a divergent nozzle and/or a compressor is arranged downstream of the turbomachine in the direction of flow.

12. The method of claim 2, wherein the fluid is a multiphase flow and at least one fluid component is gaseous and another fluid component of the fluid is liquid.

13. The method of claim 2, wherein a fluid mixture consisting of a first fluid and a second fluid is used as the compressible fluid and that the first fluid has a lower vapour pressure than the second fluid, and that the first fluid is liquid both during acceleration at the convergent nozzle and downstream of the turbomachine, and that the second fluid is at least partially gaseous during acceleration at the convergent nozzle and liquid downstream of the divergent nozzle.

14. The method of claim 2, wherein a fluid mixture consisting of a first fluid and a second fluid is used as the compressible fluid, wherein the first fluid is a gas and the second fluid is a liquid, and in that the first fluid is dissolved in the second fluid before acceleration at the convergent nozzle, is released from the second fluid during acceleration at the convergent nozzle and is dissolved again in the second fluid downstream of the divergent nozzle.

15. The method of claim 2, wherein the force FB acting in the direction of flow is a gravitational force, a centrifugal force, a magnetic force, an electrical force or a mechanical force provided by a further turbomachine.

16. The method of claim 2, wherein the turbomachine is a turbine or an MHD generator.

Description

THE DRAWINGS SHOW

[0039] FIG. 1 A flow of fluid with a turbomachine according to the prior art

[0040] FIG. 2 An arrangement for using the method according to the invention

[0041] FIG. 3 A further arrangement for using the method according to the invention

[0042] FIG. 4 A thermodynamic cycle with a centrifugal convergent nozzle and a centrifugal divergent nozzle

[0043] FIG. 5 A gravitational divergent nozzle

[0044] FIG. 6 A thermodynamic cycle with an MHD generator

[0045] FIG. 7 A heat pump with branched entropy circuit

[0046] FIG. 8 A heat pump with open branched entropy circuit

[0047] FIG. 9 A heat engine with branched entropy circuit

[0048] FIG. 10 A hydropower machine

[0049] FIG. 1 shows a flow of a fluid with a turbomachine 1 according to the prior art. Turbomachine 1 is shown as an impeller. The fluid flow transfers part of its kinetic energy to the turbomachine 1, where it is dissipated as work. The molecules M of the fluid move with the velocity v.sub.1 in the flow channel and give off a part of their lateral kinetic energy to the turbomachine at its impellers and then move on with the velocity v.sub.2.

[0050] FIG. 2 shows an arrangement for using the method according to the invention to increase an entropy flow in a turbomachine 1. For this purpose, a compressible fluid is polytropically expanded in turbomachine 1, which has the form of a turbine. After the polytropic expansion, an additional force F.sub.B 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 F.sub.B acting in the direction of flow is generated by a force field, whereby the fluid's potential energy is converted into kinetic energy of the fluid. This force F.sub.B 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 in the fluid, so that the pressure of the fluid, reduced in 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 for increasing the efficiency of the turbomachine is achieved directly downstream of the turbomachine. In the embodiment shown, the force F.sub.B can be the gravitational force, for example. 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 v.sub.2 of the fluid is at least so high that the translational velocity of the molecules M of the gas (compressible fluid component) is at least 0.3 times the speed of sound in the gas.

[0051] FIG. 3 shows a further arrangement for using the method according to the invention. The polytropic expansion in the turbomachine 1 is preceded by a convergent nozzle 2, so that the compressible fluid is accelerated before the turbomachine 1. A divergent nozzle 3 is located downstream of the turbomachine 1 in the direction of flow. Depending on the desired increase in efficiency for the turbomachine, the acceleration at the convergent nozzle upstream of the turbomachine can, for example, be up to 0.31 times or 0.51 times or 0.61 times or 0.81 times or 1.01 times the speed of sound in the fluid. Downstream of the turbomachine, the fluid is then accelerated again as close as possible to the value of the flow velocity upstream of the turbomachine (0.3 times or 0.5 times or 0.6 times or 0.8 times or equal to the speed of sound in the fluid). A compressor 5 is connected downstream of the divergent nozzle 3, although this is optional here. In another embodiment not shown, the compressor 5 is provided instead of the divergent nozzle 3. The fluid can be a pure substance (a gas), a mixture of gases or a mixture of gas and liquid and the force F.sub.B can be the force due to gravity, for example.

[0052] FIG. 4a and FIG. 4b show two arrangements for using the method according to the invention in a thermodynamic cycle with a centrifugal convergent nozzle and a centrifugal divergent nozzle. A flow channel with a fluid is set in rotation around a rotational axis 4. This causes a centrifugal force F.sub.Z to act on the fluid and causes the density of the fluid to increase with distance from the rotational axis 4. A compressor 5 is placed at the location with the highest rotational speed. The turbomachine 1 is arranged on the rotational axis 4. The fluid is first accelerated in the convergent nozzle 2 and gives off energy and momentum to the turbomachine 1. Downstream of the turbomachine 1, the fluid is accelerated by the increasing centrifugal force, and the pressure in the divergent nozzle 3 is increased again. Here, too, the molecules M of the fluid are accelerated to at least 0.3 times the speed of sound in the fluid. An amount of thermal energy Q.sub.1 can be fed in between the compressor 5 and the convergent nozzle 2. Optionally, an amount of thermal energy Q.sub.2 can be dissipated between the divergent nozzle 3 and the compressor 2. In the embodiment according to FIG. 4a, the turbomachine 1 is arranged radially to the rotational axis. In FIG. 4b, the turbomachine 1 is arranged axially to the rotational axis in an alternative embodiment. Again, the fluid can be a pure substance (a gas), a mixture of gases or a mixture of gas and liquid. In the case of a fluid consisting of gas or mixture of gases, the fluid is also accelerated here downstream of the turbomachine to at least 0.3 times the speed of sound in the fluid, so that the pressure of the fluid, reduced in 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 for increasing 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 v.sub.2 of the fluid is at least so high that the translational velocity of the molecules M of the gas (compressible fluid component) is at least 0.3 times the speed of sound in the gas.

[0053] In the embodiment shown, the force F.sub.B is therefore provided by the centrifugal force F.sub.Z. The thermodynamic machine described with a centrifugal convergent nozzle and centrifugal divergent nozzle is thus also suitable for use in places with low gravity (such as in space).

[0054] In one embodiment, the arrangements according to FIG. 3 or FIG. 4a/4b use a multiphase flow in which a phase change (evaporation/condensation) of a component or a reversible chemical reaction is used. If, for example, a mixture of water and isobutane is fed into the convergent nozzle 2 at 4 bar and 300 K, both components are liquid. Due to the acceleration in the convergent nozzle 2, the pressure drops and the isobutane reaches its boiling point. By adding rotational and vibrational energy (of the molecules M) from the liquid water, it can evaporate. The increase in volume further accelerates the flow. Part of the kinetic energy is released in the turbomachine 1. The flow is then laterally accelerated by the gravitational or centrifugal force. Due to the increased pressure in the divergent nozzle 3 and/or in the following compressor 5, the gas condenses with a major reduction in volume. However, the energy released in the process does not have to be dissipated externally, but is stored in the circuit in the form of volume-independent vibrational and rotational energy.

[0055] 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 convergent nozzle 2, the equilibrium of the solution decreases and gaseous carbon dioxide is released in the flow channel, accelerating the flow. Since a concentration equilibrium is established in the solution, an even release of gas is to be expected here. After the releasing energy in the turbomachine and accelerating in the flow channel, the gas goes back into solution due to the pressure increase in the divergent nozzle 3 and/or in the following compressor 5 and reduces the volume of the multiphase flow. Carbon dioxide then reacts with the water to form carbonic acid.

[0056] The choice of components has a significant influence on the working pressure. For substances with low vapour pressures (e.g., an isopropanol/water mixture), the pressure upstream of the convergent nozzle 2 may be less than 1 bar. This simplifies the design. Due to the high density of liquid water, the energy density and entropy flow are nevertheless very high. This makes it possible to achieve a very high speed and energy output in the turbomachine with compact dimensions.

[0057] FIG. 5 shows a gravitational divergent nozzle as a further arrangement for using the method according to the invention. A fluid is accelerated in the convergent nozzle 2 and fed to the turbomachine 1. The flow channel and divergent nozzle 3 are arranged in the direction of gravity, whereby the gravitational force F.sub.G acts as a force F.sub.B and accelerates the molecules M of the fluid by converting potential energy into kinetic energy. The machine is dimensioned such that the volume between the compressor 5 and the convergent nozzle 2 is greater than the volume between the turbomachine 1 and the compressor 5. Alternatively, a pressure-balancing vessel 6 can be fitted. In this way, the compressor 5 creates a negative pressure in the turbomachine 1, which increases the efficiency. An amount of thermal energy Q.sub.1 is fed in between the compressor 5 and the convergent nozzle 2. Optionally, an amount of thermal energy Q.sub.2 can be dissipated between the divergent nozzle 3 and the compressor 5.

[0058] Since only the relative speed of the flow is relevant for the energy supply in turbomachines 1, energy can be extracted in a narrow flow channel at high speed with a turbomachine 1 and fed in within a wider flow channel at low speed. According to E=m/2*v.sup.2, more energy is released at high speed than is fed in at low speed. The mechanical force (F.sub.m) supplied by the compressor 5 acts like the gravitational force F.sub.g and reduces the pressure downstream of the turbomachine 1. For this purpose, the pressure-balancing vessel 6, which keeps the pressure at the inlet of the convergent nozzle 2 constant, is installed between the compressor 5 and the convergent nozzle 2. For compressible fluids, pressure balancing can also be achieved by having a large volume upstream of the convergent nozzle 2 compared to the volume between divergent nozzle 3 and the compressor 5. In open processes, the surrounding atmosphere can be used for pressure balancing. If mechanical work is supplied to the compressor 5, the pressure at the outlet of the divergent nozzle 3 drops. This allows the pressure at the outlet of the turbomachine 1 to drop to almost zero, which permits high flow velocities and thus high efficiency. For this, sufficient energy must be available for the acceleration in the convergent nozzle 2, and this can be provided by a high proportion of vibrational and rotational energy (in the case of complex molecules M or multiphase flows). This accelerates the fluid to supersonic speeds even without a de Laval nozzle. Since the thermal energy Q.sub.1 does not need to be fed in at a high temperature, but is only transferred when the relative translational velocity of the molecules M within the flow is reduced, the volume-effective heat capacity and thus the entropy flow I.sub.S at the working machine 1 increases. According to P=T*I.sub.S (P=power, T=temperature, I.sub.S=entropy flow), the power P increases at constant input temperature.

[0059] The compressor 5 should be located near the lowest point in the cycle. The energy W.sub.2 required to operate the compressor 5 can be supplied partly or completely by the mechanical energy W.sub.1 released in the turbomachine 1.

[0060] The fluid used in the arrangement according to FIG. 5 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 mixture of gases, the fluid is also accelerated here downstream of the turbomachine to at least 0.3 times the speed of sound in the fluid, so that the pressure of the fluid, reduced in 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 for increasing 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 v.sub.2 of the fluid is at least so high that the translational velocity of the molecules M of the gas (compressible fluid component) is at least 0.3 times the speed of sound in the gas.

[0061] FIG. 6 shows a thermodynamic cycle with a turbomachine designed as an MHD generator as a further arrangement for using the method according to the invention. A mixture of an electrolyte (e.g., an ionised solution) and a compressible fluid is used as the working medium. The mixture is accelerated in the convergent nozzle 2 and flows through a magnetic field of the turbomachine 1, which is designed as an MHD generator. In the process, the charge carriers of the electrolyte are deflected to the left or right and the electrical energy is dissipated via the electrodes. In the divergent nozzle 3, the flow velocity is reduced, converting translational energy into vibrational and rotational energy.

[0062] The fluid is compressed in the compressor 5 and flows back to the convergent nozzle 2. The volume between the compressor 5 and the convergent nozzle 2 must be larger than the volume between the MHD generator and the compressor 5. Alternatively, a pressure-balancing vessel 6 can be fitted. In this way, the compressor 5 creates a negative pressure downstream of the MHD generator, which accelerates the flow and increases the efficiency. The thermal energy Q.sub.1 is fed in upstream of the convergent nozzle 2. Optionally, thermal energy Q.sub.2 can be dissipated downstream of the divergent nozzle 3.

[0063] One advantage of this arrangement is a higher achievable magnetic field strength in the narrow flow channel compared to the wider flow channel of a de Laval nozzle. Furthermore, the charge-carrier density in the electrolyte is high, which permits compact dimensions of the machine. In contrast to when an ionised gas is used, the process can also take place at ambient temperature, which reduces the demands on materials and the costs.

[0064] FIG. 7 shows a heat pump with a branched entropy circuit for the application of the method according to the invention. A fluid consisting of a first fluid component and a second fluid component, wherein at least the second fluid component is compressible, is accelerated in a convergent nozzle 2 and fed to a turbomachine 1. Downstream of the turbomachine 1, the fluid can optionally be accelerated by the force F.sub.B in the flow channel and divergent nozzle 3, which reduces the pressure at the outlet of the turbomachine 1. Afterwards, the second fluid component, which has a larger c.sub.p/c.sub.V ratio compared to the first fluid component, is separated in the separator 7 and fed to the compressor 5.2, where the second fluid component is accelerated and/or compressed. The temperature increases due to the compression. The first fluid component is fed to the compressor 5.1, wherein the temperature does not change or changes only very slightly compared to the second fluid component. This allows thermal energy Q.sub.1 to be fed into the first fluid component by means of the heat exchanger 8.1. The second fluid component, compressed in compressor 5.2, releases its thermal energy Q.sub.2 by means of the heat exchanger 8.2. Afterwards, both fluid components are combined in the mixer 9. The volume between the turbomachine 1 and the compressor 5.2 must be smaller than the volume between the compressor 5.1 and the mixer 9. Alternatively, a pressure-balancing vessel 6 can be fitted. In this way the compressors 5.1 and 5.2 generate a negative pressure in the separator 9, which increases the efficiency of the turbomachine 1. For a significant difference, within the working temperature range at compressors 5.1, 5.2, the ratio c.sub.p/c.sub.V of the second fluid component should be at least 1.1 times the ratio c.sub.p/c.sub.V of the first fluid component.

[0065] The dimensioning of the entropy flows has a great influence on the efficiency. With the same thermal power at the inlet and outlet (P.sub.1=P.sub.2), it follows from I.sub.S1>I.sub.S2 that, according to P.sub.1=T.sub.1.Math.I.sub.S1=T.sub.2.Math.I.sub.S2=P.sub.2, also T.sub.2>T.sub.1. This means that the mechanical energy supplied−W.sub.mech=|W.sub.4|+|W.sub.5|−|W.sub.3|—only has to compensate for the process losses. With T.sub.2=T.sub.1=T and I.sub.S1>I.sub.S2, it follows that P.sub.1>P.sub.2. A stream of energy then flows out of the machine: P=T.sub.2.Math.I.sub.S2−T.sub.1.Math.I.sub.S1=T.Math.(I.sub.S2−I.sub.S1). This means that, depending on the dimensioning of the entropy flows, the machine can also work as a heat engine.

[0066] The mass flows of the fluid components should be dimensioned such that an entropy flow I.sub.S1 of the first fluid component at the compressor 5.1 is greater than an entropy flow I.sub.S2 of the second fluid component at the compressor 5.2. For a significant increase in efficiency, the mass flow for I.sub.S1 at the compressor 5.1 should be at least five times greater than the mass flow for I.sub.S2 at the second compressor 5.2. The entropy flow at the inlet of the turbomachine is equal to the sum of the two entropy flows I.sub.S1 and I.sub.S2.

[0067] FIG. 8 shows a heat pump with an open branched entropy circuit. The machine uses a fluid in which the compressible component is air. The air is drawn in from the atmosphere at the inlet 7 and mixed with an incompressible fluid (e.g. water) in the mixer 9. The fluid is accelerated in a convergent nozzle 2 and fed to a turbomachine 1. Downstream of the divergent nozzle 3, the air is separated in the separator 7 and fed to the compressor 5.2. The compressor 5.2 increases the pressure of the air to atmospheric pressure and thus ensures there is a negative pressure in the mixer 9. The heated air then flows back into the atmosphere via the outlet 10. The pressure of the cooler, incompressible component of the fluid is increased to atmospheric pressure in the compressor 5.1. At the heat exchanger 8, the thermal energy Q.sub.1 extracted from the air is returned to the incompressible fluid.

[0068] FIG. 9 shows a heat engine with a branched entropy circuit (see FIG. 9). The heat engine works in the same way as the heat pump in FIG. 7. In the entropy circuit I.sub.S2, the thermal energy Q.sub.2 is first dissipated in the heat exchanger 8.2 and then the fluid is compressed in the compressor 5.2. Due to a low heat capacity of the fluid component in the entropy circuit I.sub.S2 in relation to I.sub.S1, only little thermal energy has to be dissipated.

[0069] FIG. 10 shows a hydropower machine for further application of the method, which converts potential and thermal energy into mechanical energy. The water flows from the upper reservoir 11 to the lower reservoir 12. The turbomachine 1, designed as a turbine, is arranged below the upper reservoir. The entropy flow of the water I.sub.S1 is mixed with air I.sub.S2 and accelerated in a convergent nozzle 2 with a mixer (e.g., a Venturi or jet-stream nozzle). The air being cooled by the acceleration extracts vibrational and rotational energy from the water molecules and expands almost isothermally. At the same time, the water molecules are accelerated with the air and release their kinetic energy to the turbine 1. The water is separated from the air in the turbine housing 1.1. The water collects at the bottom of the turbine housing 1.1 and is accelerated with a gravitational divergent nozzle. With a fall of 10 m or more, this increases the pressure by about 1 bar, thereby creating a vacuum on the turbine housing 1.1. To maintain this negative pressure, the air must be pumped out through the air duct 14, e.g., by means of a piston pump or a jet-stream pump 13.

LIST OF REFERENCES

[0070] M Molecule [0071] 1 Turbomachine [0072] 1.1 Housing [0073] 2 Convergent nozzle [0074] 3 Divergent nozzle [0075] 4 Rotational axis [0076] Compressor [0077] 5.1 Compressor [0078] 5.2 Compressor [0079] 6 Balancing vessel [0080] 7 Separator [0081] 8 Heat exchanger [0082] 8.1 Heat exchanger [0083] 8.2 Heat exchanger [0084] 9 Mixer [0085] 10 Outlet [0086] 11 Reservoir [0087] 12 Reservoir [0088] 13 Jet-stream pump [0089] 14 Air duct