EP2002089A2

EP2002089A2 - Piston steam engine having internal flash vapourisation of a working medium

Info

Publication number: EP2002089A2
Application number: EP07723993A
Authority: EP
Inventors: Michael Löffler
Original assignee: Electricite de France SA
Current assignee: Electricite de France SA
Priority date: 2006-04-04
Filing date: 2007-04-04
Publication date: 2008-12-17
Anticipated expiration: 2027-04-04
Also published as: EP2002089B1; IL194523A; JP5145326B2; KR101417143B1; CA2650541A1; IL194523A0; WO2007115769A2; JP2009532619A; US20090100832A1; KR20080112362A; CA2650541C; CN101454542A; US8061133B2; WO2007115769A3

Abstract

The invention relates to a piston steam engine having flash vapourisation. Said inventive piston steam engine has a simple construction, a very good exergetic degree of efficiency and can be operated with various working mediums and at different temperatures. Also, the inventive piston steam machine can reach very high power density.

Description

Piston steam engine with internal flash evaporation of the working fluid

description

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 thereby 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.

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 ratio or the expansion ratio, also referred to below as the volume ratio, is approximately 4 to a maximum of 8 in a screw machine

BESTATIGUNGSKOPIE Piston steam engine on the other hand, volume ratios of large 100 can be achieved.

The convective heat exchange hiss the working medium and the walls of the screw machine is very large, since there is a fully developed two-phase flow and, incidentally, the warm non-wearing surface is very large.

The volumetric efficiency of a screw machine is due to design relatively poor, the leakage losses can not be reduced by a piston or piston rings as in a Kolbendampfmaschme.

Also in other known and commercially available heat engines, such as conventional piston steam engines, ORC engines operating on the Orgamc Rankine cycle, Rankine engines or steam turbines, becomes an existing heat source, especially if the heat source is relatively low Temperature has, for example, 200 ⁰ C, taken only a relatively small mechanical power.

In order to make the best possible use of the exergy contained in the warmth of the heat transfer medium, the heat transfer medium of the heat source should be cooled down to ambient temperature in as reversible a process 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 ⁰ C and not to the ambient temperature. In particular, if only heat is available at a relatively low temperature level, which is only partially convertible into mechanical energy anyway, this relatively high end temperature of the heat transfer medium of the heat source and the associated low exergetic efficiency have a particular 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 claim 1, characterized in that the working fluid in liquid form at least indirectly in the working space of

Piston steam engine is introduced when the piston is in the range of a top dead center (TDC). This makes it possible for the liquid phase and the vaporous phase of the working medium to be separated 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 an advantageous embodiment of the invention, at least one pre-chamber is provided, which is in communication with the working space, wherein the working medium is preferably introduced into the pre-chamber and particularly preferably on a circular path in the antechamber. 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 prechamber 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 completely or 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, if available, 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 C to 350 ° C, water has proved to be particularly suitable.

If heat or waste heat at a temperature of about 150 ⁰ C to 200 ⁰ C is available, methanol has proven to be particularly suitable. If warm or waste heat with a temperature of about 100 ⁰ C to 150 ⁰ C is available, pentane has been found to be particularly suitable.

If warm or waste heat with a temperature of about 100 ⁰ C is available, R134a has been found 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 the cyclone wall or other surfaces of the

Piston steam engine convective takes warm. This warmedammende coating disposed on the work space or cyclone inner wall may be for example made 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 components of the machine which are accessible to the gaseous phase must have a temperature which is greater than the condensation temperature of the working medium at the gas pressure currently being applied. If the surfaces of the components were cold, some of the resulting gaseous phase would abruptly 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.

drawing

Show it:

FIGS. 1 and 2: exemplary embodiments of piston steam engines according to the invention with cyclone,

Figure 3: An antechamber of a piston steam engine according to the invention and

Figure 4: an embodiment of an inventive

Piston steam engines with an injector injecting into the working space.

Description of the embodiments

Figure 1 shows an example of the structure 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. The discharge 17 for the working medium can also open directly into the working space 11 (not shown).

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 prechamber 13 at the time of injection is lower than the pressure of the working medium m of the supply line 15, a so-called flash evaporation takes place in the prechamber 13 immediately after the injection of the working medium. As a result, the pressure m of the prechamber 13 and m increases the work space 11 connected to the prechamber 13, so that the piston is moved 3 m towards bottom dead center UT while giving 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 flows 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.

Figure 2 shows the structure of a piston steam engine according to the invention with two prechambers 13.1 and 13.2, two supply lines 15.1 and 15.2 for the working fluid. In the supply lines 15.1 and 15.2 are two switchable intake valves

19.1 and 19.2 arranged.

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

The working medium contained in the first supply line 15.1 has a higher temperature than that in the second supply line

15.2 located working medium. 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 used optimally, since in an internal combustion engine, the exhaust gases at a temperature greater 200 ⁰ C incurred while the Kuhlmittelwarme and the oil have a temperature of about 120 ⁰ 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 Kuhlwassers and the oil required ,

First, the warmer working medium is injected at a temperature of 200 ⁰ C. If this has cooled to 120 ⁰ C, then some 120 ⁰ 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 Kolbendampfmaschme shown.

The erfmdungsgemaße Kolbendampfmaschme works on the two-stroke principle. Em intake stroke and a compression stroke omitted. 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.

Hot liquid working medium is injected under pressure into an antechamber of the piston steaming machine into the piston steaming machine according to the invention. The working fluid can be harmless water. FIG. 3 shows the construction 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 into the prechamber 13 substantially tangentially and moves on a radially outer circular path. Due to its lower density, the steam produced in the flash evaporation is forced into the middle of the prechamber 13, so that a separation of liquid and vaporous working medium m of the prechamber 13 takes place. In the middle of the pre-chamber 13, a compound 29 is arranged, which mouths in 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 is disposed below the connection 29 and below the working space 11, not shown in Figure 3, the gravity supports the separation of liquid and vapor phase in addition.

So that the resulting vapor does not condense on surfaces in the working space, the affected surfaces of the piston 3, cylinder 5 and prechamber 13 must be heated and / or heat-sealed. To prevent heat from the heated surfaces to the liquid phase of the working fluid, 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 steam, on which act due to lower density of 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, m the circular path remains. 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 a suitable dimensioning of the machine and coating the Vorkammerwande does not lead to a significant impairment of the process.

In addition, it was possible to demonstrate that the phase separation succeeds: the liquid phase remains in the cyclone during the flash evaporation, while the vapor phase escapes from the cylinder space.

In addition, it was possible to prove that the convection of the liquid phase with the wall of the antechamber 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 was possible to show that the flash process m in the pre-chamber 13 or in the working space 11 proceeds at a very high speed, which is important for the machine's feasibility.

FIG. 4 shows a further exemplary embodiment of a piston steam engine according to the invention. In this exemplary embodiment, the pre-chamber 13 is omitted 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, a safe working fluid, such as water, can be used compared to ORC processes and quay processes.

Claims

claims

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 space (11), wherein the working space (11) of the cylinder (5) and the piston (3) is limited, with at least one inlet valve (19), wherein the working fluid through the at least one inlet valve ( 19) into the working space (11) can be conducted, with at least one outlet valve (21), wherein the working medium through the at least one outlet valve

(21) from the working space (11) is conductive, characterized in that the working medium is introduced in liquid form at least indirectly in the working space (11) when the piston (3) in the region of a top dead center (TDC) or in Working stroke is located.

2. Piston steam engine according to claim 1, characterized in that at least one prechamber (13) is provided, that the working space (11) and the prechamber (13) communicate with each other in connection (29), and that the working fluid in liquid form in the Prechamber (13) is introduced, that the liquid phase of the working medium for the most part in the prechamber (13) remains, while the vapor phase of the working medium flows into the working space (11).

3. Piston steam engine according to claim 2, characterized in that the working medium is introduced substantially tangentially into the pre-chamber (13).

4. Piston steam engine according to claim 2 or 3, characterized in that the connection (29) between the working space (11) and pre-chamber (13) in the center of the pre-chamber (13) opens into this.

5. Piston steam engine according to one of claims 2 to 4, characterized in that a plurality of prechambers (13.1, 13.2) are arranged on a cylinder (5), that the pre-chambers (13.1, 13.2) are connected to the working space (11), and that Working fluid with different temperature as a function of the pressure prevailing in the working space (11) and / or the temperature prevailing in the working space (11) successively in the pre-chambers (13.1 or 13.2) or in the working space

(11) is introduced.

6. Piston steam engine according to one of the preceding claims, characterized in that a plurality of inlet valves (19.1, 19.2) per cylinder (5) are provided.

7. Piston steam engine according to one of the preceding claims, characterized in that the injected from the various inlet valves or injectors (19.1, 19.2) liquid working fluid has different temperatures, and that of the various injectors (19) injected liquid working fluid in the order of the warmest is injected to the coldest working fluid, the next working fluid is injected when the already in the pre-chamber (13) or the working space (11) located working fluid has reached the temperature of the next colder working medium.

8. Piston steam engine according to one of the preceding claims, characterized in that the liquid working medium in the working space (11) or in the at least one prechamber (13) by means of an injector

(19) is injected.

9. Piston steam engine according to one of the preceding claims, characterized in that the liquid Working medium is atomized during the injection process into small drops of liquid.

10. Piston steam engine according to one of the preceding claims, characterized in that water, methanol, pentane and / or R134a is used as the working medium.

11. 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 pre-chamber (13) inside and / or outside are thermally insulated.

12. Piston steam engine according to claim 11, characterized in that preferably the inner thermal insulation of Teflon, enamel and / or ceramic.

13. 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 heatable.

14. Piston steam engine according to one of the preceding claims, characterized in that a steam valve

(22) is provided, and that by means of the steam valve (22), the vaporous working medium is discharged from the working space.

15. Piston steam engine according to one of the preceding claims, characterized in that the one or more outlet valves (21) and the steam valve (22) in the region of top dead center (TDC) are closed, then that liquid working fluid in the pre-chamber (13) or the working space (11) is introduced, and that in the region of the bottom dead center (UT) or the exhaust valves (21) are opened.