EP2002089B1 - Piston steam engine having internal flash vapourisation of a working medium - Google Patents

Description

The invention relates to a piston steam engine and to a method for operating a piston steam engine.

State of the art.

Currently available piston steam engines use steam provided by a steam generator. Via inlet valves and exhaust valves, the steam is conducted in such a way that it reaches the cylinder chamber at high pressure, moves the piston in the cylinder chamber, is thereby expanded and then expelled from the cylinder chamber through the piston.

The steam generators required for a piston steam engine usually consist of a heat exchanger in which the working medium, such as water, is vaporized at the desired working pressure. The heat required for the evaporation process is provided by a heat transfer medium, such as flue gases. In return, the heat transfer medium in the steam generator is cooled to a temperature in the range of the evaporation temperature of the working medium.

• Das Verdichtungs- beziehungsweise das Expansionsverhältnis, nachfolgend auch zw. Volumenverhältnis genannt, liegt bei einer Schraubenmaschine bei ca. 4 bis maximal 8. In einer Kolbendampfmaschine hingegen können Volumenverhältnisse größer 100 erreicht werden.

Der konvektive Wärmeaustausch zwischen dem Arbeitsmedium und den Wänden der Schraubenmaschine ist sehr groß, da eine voll ausgebildete Zwei-Phasen-Strömung vorliegt und im Übrigen die wärmeübertagende Fläche sehr groß ist.
Der volumetrische Wirkungsgrad einer Schraubenmaschine ist bauartbedingt relativ schlecht, das die Leckageverluste nicht wie bei einer Kolbendampfmaschine durch Dichtungs- oder Kolbenringe reduziert werden können.
Auch bei anderen bekannten und am Markt verfügbaren Wärmekraftmaschinen, wie zum Beispiel herkömmliche Kolbendampfmaschinen, ORC-Maschinen, die nach dem Organic-Rankine-Cycle arbeiten, Rankine-Maschinen oder Dampfturbinen, wird aus einer vorhandenen Wärmequelle, vor allem wenn die Wärmequelle eine relativ geringe Temperatur besitzt, beispielsweise 200°C, nur eine relativ geringe mechanische Leistung entnommen.In another approach, an attempt is made to realize a so-called flash evaporation in a screw machine. Here are the works of Prof. Kauder, University of Dortmund called. However, the principal disadvantages of a screw machine are obvious:

• The compression or expansion ratio, also referred to below as the volume ratio, is approximately 4 to a maximum of 8 in a screw machine Piston steam engine, however, can be achieved volume ratios greater than 100.

The convective heat exchange between the working fluid and the walls of the screw machine is very large, since there is a fully developed two-phase flow and incidentally the heat transferring surface is very large.
The volumetric efficiency of a screw machine is due to the design relatively poor, the leakage losses can not be reduced as in a piston steam engine by sealing or piston rings.
Also, other known and commercially available heat engines, such as conventional piston steam engines, ORC machines operating in the Organic Rankine cycle, Rankine engines, or steam turbines, become available from an existing heat source, especially if the heat source is relatively low Temperature has, for example, 200 ° C, taken only a relatively small mechanical power.

From the US 4,301,655 US is and the GB 171, 291 Combined internal combustion engines and steam engines are known.

From the US Pat. No. 3,720,188 US and the DE 100 00 082 A1 Piston engines are known in which the thermal energy is transmitted through the wall of a cylinder head to the working medium.

The from the GB 2 082 683 A known steam engine has an external burner B, which heats the liquid working medium via a heat exchanger H. In this piston machine, the liquid working medium is injected directly into the working space.

In order to make the best possible use of the exergy contained in the heat of the heat transfer medium, the heat transfer medium of the heat source should be cooled down to ambient temperature in a process that is as reversible as possible.
In the steam generators of known heat engines in general, however, the heat transfer medium of the heat source only cools down to a temperature close to the evaporation or condensation temperature. The heat transfer medium is cooled, for example, only from 200 ° C to 140 ° C and not to the ambient temperature. In particular, if only heat at a relatively low temperature level is available, which is anyway only a small part convertible into mechanical energy, this relatively high end temperature of the heat transfer medium of the heat source and the associated low exergetic efficiency has a special effect unfavorable to the performance and economy of the heat engine.
In addition, some of the above-mentioned heat engines partially toxic or harmful work equipment used.
The invention is based on the object to provide a heat engine, which at least partially overcomes the above-mentioned disadvantages of the known from the prior art heat engines. In addition, to be converted into mechanical work with the heat engine according to the invention, the highest possible proportion of the available heat.
This object is achieved in a piston steam engine according to the preamble of claims 1 and 15 by the features of the characterizing parts of these claims. This solution includes, among other things, that the working fluid is introduced in liquid form into the at least one antechamber of the piston steam engine when the piston is in the region of top dead center (TDC). This makes it possible to separate the liquid phase and the vapor phase of the working medium in the piston steam engine according to the invention, so that the liquid phase comes into contact only to a small extent with the walls of the piston steam engine. For example, in an experimental setup, only 2% of the workspace surface was wetted by the liquid phase of the working medium. As a result, the heat losses are significantly reduced.
In the piston steam engine according to the invention hot and pressurized working fluid is introduced in liquid form directly or indirectly into the working space. Due to the pressures and temperatures prevailing in the piston steam engine, the working medium begins to evaporate as soon as it has been introduced into the piston steam engine. The resulting vapor pressure drives the piston.

In the course of the movement of the piston, the cylinder volume increases and further working fluid can evaporate. During evaporation, the liquid portion of the working medium cools down. When reducing the pressure, the vaporous portion of the working medium also cools down. Because of these processes, the efficiency, in particular the exergetic efficiency and the performance of the piston steam engine according to the invention are significantly increased compared to other heat engines.

In the invention, at least one pre-chamber is provided, which is in communication with the working space, wherein the working medium is introduced into the pre-chamber and particularly preferably in a circle-like path in the prechamber. The circular path of the liquid phase causes centrifugal forces which greatly accelerate the liquid phase radially outward due to the high density. The resulting in the flash evaporation of the working medium vapor has a significantly lower density than the liquid phase and can flow into the cylinder chamber, since the connection between the antechamber and the working chamber in the center of the antechamber opens into this. The radial acceleration causes the liquid phase can not escape from the antechamber. This achieves a very simple and at the same time effective phase separation. The volume of the prechamber should be as small as possible.

In a further embodiment of the invention, a plurality of pre-chambers and / or a plurality of injectors per cylinder are provided, which are all connected to the working space. This makes it possible to introduce the working fluid at different temperatures as a function of the pressure prevailing in the working space during the working cycle and / or the prevailing temperature in the working space and / or the position of the piston in the atria and / or the working space. This allows working media with different Temperatures without Exergieverluste be coupled due to mixing operations in the piston steam engine according to the invention.

If several injectors inject one after the other into an antechamber or the working space, it must be ensured that the working medium already in the cyclone is not vaporized or squirted by the injection process.

Alternatively, it is also possible to introduce the working medium partially directly into the working space. In this case, that liquid working medium can be atomized during the injection process and distributed in the form of small drops within the working space and the antechamber. The friction between the droplets and the gaseous phase of the working medium avoids direct contact between the droplets and the surfaces of the piston steam engine. As a result, the unwanted heat transfer between the drops and the surfaces of the piston steam engine is greatly reduced.
As injectors may serve injectors, as used in fuel injection systems of conventional gasoline or diesel internal combustion engines.
Of course, it may be necessary to adapt these commercially available injectors to the specific conditions of use, in particular the sometimes very high temperatures and the corrosive working media.
If the heat transfer medium has a temperature of about 200 ° C to 350 ° C, water has proved to be particularly suitable.
If heat or waste heat at a temperature of about 150 ° C to 200 ° C is available, methanol has proven to be particularly suitable.

When heat or waste heat at a temperature of about 100 ° C to 150 ° C is available, pentane has been found to be particularly suitable.

When heat or waste heat at a temperature of about 100 ° C is available, R134a has proven to be particularly suitable.

Furthermore, it has proved to be advantageous to provide the surfaces of the piston steam engine which come into contact with the liquid working medium with an inner and / or outer heat insulation.

The internal thermal insulation is of particular importance to prevent the cooling liquid working fluid from receiving convective heat from the cyclone wall or other surfaces of the piston steam engine. This arranged on the working space or cyclone inner wall heat-insulating coating may be for example of Teflon, enamel or ceramic.

Alternatively or additionally, the surfaces of the piston steam engine which come into contact with the working medium can be heated in order to effectively prevent the condensation of the working medium on these surfaces. When a gaseous phase is created by the flash process, the gaseous phase accessible components of the machine must be at a temperature greater than the condensation temperature of the working fluid at the gas pressure being applied. If the surfaces of the components were colder, some of the resulting gaseous phase would suddenly condense on these surfaces and the condensed phase would no longer be available to drive the piston and the performance and efficiency of the machine would decrease.

Further advantages and advantageous embodiments of the invention are the drawings, the description and the claims removed. All disclosed features can be essential to the invention both individually and in combination. The invention is defined by the entirety of the features of the independent claims.

drawing

Figuren 1 und 2:

Ausführungsbeispiele erfindungsgemäßer Kolbendampfmaschinen mit Zyklon,

Figur 3:

Eine Vorkammer einer erfindungsgemäßen Kolbendampfmaschine und

Figur 4:

ein Ausführungsbeispiel einer erfindungsgemäßen Kolbendampfmaschinen mit einem in den Arbeitsraum einspritzenden Injektor.

Show it:

FIGS. 1 and 2:

Embodiments of inventive piston steam engines with cyclone,

FIG. 3:

An antechamber of a piston steam engine according to the invention and

FIG. 4:

An embodiment of a piston steam engine according to the invention with an injector in the working space injector.

Description of the embodiments

FIG. 1 shows by way of example the construction of a first embodiment of a piston steam engine according to the invention with an antechamber 13, a piston 3, a cylinder 5, a connecting rod 7 and a crankshaft 9, which may be coupled to a generator, not shown. The piston 3 and the cylinder 5 define a working space 11. An antechamber 13 is connected to the working space 11. In the antechamber 13 open a supply line 15 and a discharge line 17 for the working medium.

In the supply line 15 for the liquid working medium, a switchable inlet valve 19 is arranged. With the aid of this inlet valve, which can be designed as an injector, liquid working fluid can be injected into the pre-chamber 13 become. This injection is preferably carried out when the piston 3 is in the region of the top dead center OT.

Since the pressure in the pre-chamber 13 at the time of injection is lower than the pressure of the working medium in the supply line 15, a so-called flash evaporation takes place in the pre-chamber 13 immediately after the injection of the working medium. As a result, the pressure in the prechamber 13 and in the working chamber 11 connected to the prechamber 13 increases, so that the piston 3 is moved in the direction of bottom dead center UT, thereby delivering work to the crankshaft 9.

When the piston 3 is in the area of the bottom dead center UT, a switchable outlet valve 21 located in the outlet 17 for the working medium is opened and the piston 3 pushes the remaining liquid phase and the working medium which has become vaporous during its subsequent movement in the direction TDC the work space 11 from.

Among other things, the discharge line 17 serves to discharge the liquid phase remaining in the pre-chamber 13. About the derivative 17 and the vaporized working medium can be removed. Alternatively, it is also possible in the working space 11 to provide an additional steam valve 22, which takes over the removal of the vaporized working medium. The steam valve 22 may be formed as a poppet valve and (not shown) by a camshaft, similar to a gas exchange valve of an internal combustion engine and be actuated.

When the working medium is guided in a closed circuit, the discharge line 17.1 for the working medium opens into a condenser 23. The working medium discharged through the steam valve 22 can be led into the condenser 23 through a discharge line 17.3. There is the working medium liquefied again and then conveyed by a pump 25 in a heat exchanger 27. From there, the working medium passes via the supply line 15 back into the prechamber 13.

FIG. 2 shows the structure of a piston steam engine according to the invention with two pre-chambers 13.1 and 13.2, two supply lines 15.1 and 15.2 for the working medium. In the supply lines 15.1 and 15.2 two switchable inlet valves 19.1 and 19.2 are arranged.

The remaining components of the piston steam engine and its periphery can, as in the first embodiment according to FIG. 1 be executed, which is hereby incorporated by reference.

The working medium contained in the first supply line 15.1 has a higher temperature than the working medium contained in the second supply line 15.2. Therefore, first a certain amount of the working medium contained in the first supply line 15.1 is introduced into the first prechamber 13.1. There, this working fluid evaporates and gives off work on the piston 3. This reduces the pressure and temperature of the working medium 11 and pre-chambers 13.1 and 13.2 located working medium. As soon as the temperature of the working medium located in the working space 11 and prechambers 13.1 and 13.2 has approached the temperature of the working medium located in the second feed line 15.2, working medium from the second supply line 15.2 is still in the same working stroke of the piston 15 by brief opening of the second inlet valve 19.2 introduced into the second prechamber 13.2. Also, this working medium evaporates immediately after it has been introduced into the antechamber 15.2 and gives off work on the piston 3 from.

With this embodiment of the piston steam engine according to the invention heat can be used, the two Temperature levels is available. As a result, for example, the waste heat of an internal combustion engine can be optimally utilized, since in an internal combustion engine, the exhaust gases at a temperature greater than 200 ° C incurred while the coolant heat and the oil have a temperature of about 120 ° C. To bring the working fluid to two different temperature levels, a first heat exchanger (not shown), which is operated with the waste heat of the exhaust gases, and a second heat exchanger (not shown), which is heated with the waste heat of the cooling water and the oil required ,

First, the warmer working fluid is injected at a temperature of 200 ° C. If this has cooled to 120 ° C, then some 120 ° C hot working medium is injected. The related to the heat of combustion efficiency of an internal combustion engine can be increased by about 10% with the piston engine shown.

The piston steam engine according to the invention operates on the two-stroke principle. An intake stroke and a compression stroke eliminated. In the region of the top dead center OT of the piston, the outlet valve or valves 21 are closed and then the working medium is injected through the inlet valve 19. On the way of the piston 3 from the TDC to the bottom dead center UT evaporated, as described, a part of the working medium. In the area of UT, the outlet valve 21 is opened. On the way of the piston 3 from BDC to TDC, the remaining liquid phase and the resulting gaseous phase are discharged through the outlet valve 21. Liquid and gaseous phase can pass through the same outlet valve 21 or separate valves are provided.

In the piston steam engine according to the invention hot liquid working fluid is injected under pressure into an antechamber of the piston steam engine. The working fluid can be harmless water.

FIG. 3 shows the structure of an antechamber 13 for a piston steam engine according to the invention. The prechamber 13 is constructed similar to a cyclone separator. The supply line 15, the discharge line 17 and the valves 19 and 21 are indicated.

The liquid working fluid is introduced substantially tangentially into the antechamber 13 and moves on a radially outer circular path. Due to its lower density, the vapor produced during the flash evaporation is forced into the middle of the prechamber 13, so that a separation of liquid and vaporous working medium takes place in the prechamber 13. In the middle of the pre-chamber 13, a compound 29 is arranged, which opens into the working space 11. Via the connection 29, the vaporous working medium passes from the antechamber into the working space 11.

If the pre-chamber 13 below the junction 29 and below the in FIG. 3 Not shown working space 11 is arranged, the gravity supports the separation of liquid and vapor phase in addition.

So that the resulting steam is not condensed on surfaces in the working space, the affected surfaces of the piston 3, cylinder 5 and prechamber 13 must be heated and / or heat-insulated. So that no heat is released from the heated surfaces to the liquid phase of the working medium, two alternative measures can be taken.

The pre-chamber 13 is geometrically designed such that the injected liquid phase of the working medium can move stably on a circular path. The pre-chamber 13 is referred to in this case as a cyclone. The centrifugal forces occurring on the circular path ensure that the resulting vapor, on which act due to lower density low centrifugal forces, can escape into the cylinder chamber of the piston steam engine and the liquid Heat transfer medium, act on the large density due to the large centrifugal forces, remains in the circular path. Experiments have shown that in this way a phase separation is achieved during the evaporation process.

Calculations have shown that the rotational speed of the liquid working medium, despite the friction of the liquid on the wall of the pre-chamber 13 remains at a level sufficient for phase separation and that the heat exchange of the liquid working medium with the cyclone wall with appropriate dimensioning of the machine and coating of the pre-chamber walls does not lead to a significant impairment of the process.

Furthermore, it could be demonstrated in experiments that the phase separation succeeds: the liquid phase remains in the flash vaporization in the cyclone, while the vapor phase escapes into the cylinder space.

In addition, it was possible to prove that the convection of the liquid phase with the wall of the pre-chamber 13 is not significant. In the experiment, essentially the calculated amount of liquid phase is present after the flash process. Convection has not led to any significant additional evaporation.

Finally, it could be shown in tests that the flash process takes place in the prechamber 13 or in the working space 11 at a very high speed, which is important for the feasibility of the machine.

In FIG. 4 is a further embodiment of a piston steam engine according to the invention shown. In this embodiment eliminates the pre-chamber 13 and the liquid working medium is injected directly into the working space 11. This can be done with the aid of an injector known from the prior art.

The working fluid is atomized during the injection process into small drops, similar to the injection of diesel fuel into the combustion chamber of an internal combustion engine. The drops are held in suspension by friction in the gas phase. In this way, the drops can touch the hot surfaces only to a small extent and the heat exchange between the liquid phase and the hot surfaces is kept low.

With the piston steam engine according to the invention approximately twice the mechanical power can be obtained in an existing heat source compared to conventional machines in which an ORC or a Kalina process are realized. In addition, compared to ORC processes and Kalina processes a safe working fluid, such as water, can be used.

Claims (18)

1. Piston steam engine with at least one cylinder (5), wherein in the at least one cylinder (5) a piston (3) oscillates, with a working chamber (11), wherein the working chamber (11) is limited by the cylinder (5) and the piston (3), with at least one inlet valve (19), wherein the working medium can be conducted through the at least one inlet valve (19) into the working chamber (11), with at least one outlet valve (21), wherein the piston steam engine is adequate such that the working medium in liquid form is brought at least indirectly into the working chamber (11), when the piston (3) is in the region of a top dead center (TDC) or in the work cycle, wherein the piston steam engine is suitable such that the liquid working medium is conveyed via a feed line (15) to the inlet valve (19), characterized in that at least one prechamber (13) is provided, that the working chamber (11) and the prechamber (13) are connected to each other, that the piston steam engine furthermore is suitable such that the working medium in liquid form is introduced into the prechamber (13) such that the liquid phase of the working medium remains predominantly in the prechamber (13), while the vaporous phase of the working medium streams into the working chamber (11), and that the working medium can be conducted through the at least one outlet valve (21) from the prechamber (13).
2. Piston steam engine according to claim 1, characterized in that the working medium is introduced essentially tangentially into the prechamber (13).
3. Piston steam engine according to claim 1 or 2, characterized in that the connection (29) between the working chamber (11) and the prechamber (13) opens out in the center of the prechamber (13).
4. Piston steam engine according to one of the preceding claims, characterized in that several prechambers (13.1, 13.2) are arranged at a cylinder (5); that the prechambers (13.1,13.2) are connected to the working chamber (11); and that the working medium with different temperature depending on the pressure prevalent in the working chamber (11) and/or the temperature prevalent in the working chamber (11) is successively introduced into the prechambers (13.1 or 13.2) or into the working chamber (11).
5. Piston steam engine according to one of the preceding claims, characterized in that several inlet valves (19.1, 19.2) are provided per cylinder (5).
6. Piston steam engine according to one of the preceding claims, characterized in that the liquid working medium injected out of the various inlet valves or injectors (19.1, 19.2) has different temperatures; and that the liquid working medium injected out of the various injectors (19) is injected in sequence from the warmest to the coldest working medium, wherein the respectively next working medium is injected when the working medium that is already in the prechamber (13) or the working chamber (11) has reached the temperature of the next coldest working medium.
7. Piston steam engine according to one of the preceding claims, characterized in that the liquid working medium is injected into the working chamber (11) or into the at least one prechamber (13) by means of an injector (19).
8. Piston steam engine according to one of the preceding claims, characterized in that during the injection process, the liquid working medium is reduced to small droplets of liquid.
9. Piston steam engine as according to one of the preceding claims, characterized in that as working medium water, methanol, pentane, and/or R134a is used.
10. Piston steam engine according to one of the preceding claims, characterized in that the cylinder (5), the piston (3) and/or the at least one prechamber (13) are thermally insulated inside and/or outside.
11. Piston steam engine according to claim 11, characterized in that preferably the interior thermal insulation consists of Teflon, enamel, and/or ceramic.
12. Piston steam engine according to one of the preceding claims, characterized in that the cylinder (5), the piston (3) and/or the at least one prechamber (11) are heatable.
13. Piston steam engine according to one of the preceding claims, characterized in that a vapor valve (22) is provided; and that by means of the vapor valve (22) the vaporous working medium is discharged from the working chamber.
14. Piston steam engine according to one of the preceding claims, characterized in that the outlet valve(s) (21) and the vapor valve (22) are closed in the area of the top dead center (TDC); that liquid working medium is subsequently introduced into the prechamber (13) or into the working chamber (11); and that in the area of the bottom dead centre (BDC) the outlet valve(s) is/are opened.
15. Method for operating a piston steam engine with at least one cylinder (5), with at least one inlet valve (19) and at least one outlet valve (21), wherein in the at least one cylinder (5) a piston (3) oscillates, with one working chamber (11) and at least one prechamber (13), wherein the working chamber (11) is limited by the cylinder (5) and the piston (3), wherein the working chamber (11) and the prechamber (13) are connected to each other (29), and wherein at least one outlet valve (21) is arranged at the prechamber (13), characterized in that the outlet valve (21) is closed when the piston (3) is in the area of the top dead centre (TDC), that liquid and heated working medium is injected into the at least one prechamber (13), after closing the outlet valve (21) and when the piston (3) is in the area of the top dead centre (TDC) or in the work cycle, that the liquid phase of the working medium predominantly remains in the prechamber (13), while the vaporous phase of the working medium streams into the working chamber (11), and that subsequently the piston (3) ejects the remaining liquid phase and the now vaporous working medium through the at least one outlet valve (21).
16. Method according to claim 15, characterized in a piston steam engine according to one of the preceding claims, characterized in that several prechambers (13.1, 13.2) are arranged at a cylinder (5), that the prechambers (13.1, 13.2) are connected with the working chamber (11) and that the working medium with different temperature depending on the pressure prevalent in the working chamber (11) and/or the temperature prevalent in the working chamber (11) is injected successively into the prechambers (13.1 or 13.2) or into the working chamber (11).
17. Method according to claim 15 or 16, characterized in that during the work cycle liquid working medium of various temperatures is injected in the sequence from the warmest to the coldest working medium, and that the respectively next working medium is injected, when the working medium already prevalent in the prechamber (13) or the working chamber (11) has reached the temperature of the next-coldest working medium.
18. Method according to one of the claims 15 to 17, characterized in that at least one outlet valve (21) is opened, when the piston (3) is in the area of the bottom dead center (BDC.)

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