WO2005031135A1

WO2005031135A1 - Increasing the effectiveness of hydrogen-operated internal combustion engines

Info

Publication number: WO2005031135A1
Application number: PCT/EP2004/010741
Authority: WO
Inventors: Bernhard Adler; Robert Adler; Sascha Dorner
Original assignee: Linde Aktiengesellschaft
Priority date: 2003-09-26
Filing date: 2004-09-24
Publication date: 2005-04-07
Also published as: DE10344832A1; EP1664504A1

Abstract

Disclosed is a method for delivering a medium that is combustible in an internal combustion engine. According to said method, combustion air is fed before and/or at least temporarily along with the medium and is compressed in the combustion chamber/s of the internal combustion engine. Steam is delivered in the final phase of compression and/or following compression of the combustion air. Preferably, the steam is delivered in an isochoric or substantially isochoric manner at the top dead center.

Description

description

Increasing the efficiency of combustion engines powered by hydrogen

The invention relates to a method for supplying a medium which can be dispersed in an internal combustion engine, combustion air being supplied before and / or at least temporarily together with the supply of the medium and being compressed in the combustion chamber (s) of the internal combustion engine.

In the case of the prior art methods for supplying a medium, if a cryogenic medium, such as hydrogen, is used, the possibly modified internal combustion engines usually have a hydrogen

Intake manifold injection system, which essentially corresponds to the intake manifold injection system used in conventional Otto engines. Due to the poor efficiency of such internal combustion engines with hydrogen manifold injection, common-rail high-pressure injection systems are being tested. Common-rail high-pressure injection systems are not able to significantly improve the efficiency of an internal combustion engine, but they can be used to increase the displacement.

A disadvantage of the internal combustion engines with hydrogen intake manifold injection that have been used to date is that the gaseous hydrogen in the intake manifold displaces a considerable part of the intake air and thus less oxygen is available for combustion. The consequence of this is that the displacement capacity of hydrogen-powered internal combustion engines with intake manifold injection is significantly lower than in gasoline or diesel operation.

This disadvantage does not apply to a high-pressure injection of the gaseous hydrogen into the closed cylinder - that is to say with the suction valves closed or closed. In order to save compression work, the gaseous hydrogen is advantageously injected into the closed cylinder only just before the top dead center of the piston.

The temperature of the intake air at top dead center, which is dependent on the compression ratio selected, is for example 275 ° C. Is now cold hydrogen in injected into the combustion chamber of the cylinder, the compression temperature is lowered and compression work is thereby destroyed.

From German patent application 102 54 156 - the disclosure content of which is included in the disclosure content of the present patent application with this citation - a method for supplying a medium combustible in an internal combustion engine is known. In this, the medium is heated to at least ambient temperature, preferably to a temperature of at least 500 ° C., before being fed into the internal combustion engine, and is supplied to the internal combustion engine at a pressure between 100 and 500 bar, preferably at a pressure between 200 and 300 bar.

The above-described procedure - hereinafter referred to as the HTI procedure - results in an efficiency increase of more than 0% compared to conventional procedures in which an intake manifold injection system is used. In addition, the consumption of fuel or combustible medium is reduced while the internal combustion engine is more powerful. In the partial load range of the internal combustion engine in particular, a significant increase in efficiency is achieved using the HTI process. A disadvantage of the HTI process, however, is that the comparatively high working temperatures cannot be implemented in practice. The reason for this is the heat loss or the required heat dissipation, since these working temperatures are too high for the materials previously used.

From the unpublished German patent application 103 35 799 - the disclosure content of which is also included in the disclosure content of the present patent application - a method for supplying a medium which is combustible in an internal combustion engine is known, the medium under superatmospheric pressure and at elevated temperature to the internal combustion engine supplied and wherein combustion air is supplied before and / or at least temporarily together with the supply of the medium. With this procedure, water is now at least temporarily supplied to the internal combustion engine or its combustion chambers together with the supply of the combustion air. The procedure described in German patent application 103 35 799 - hereinafter referred to as the Advanced HTI process - has the advantage that, by supplying or injecting water during the compression of the combustion air required for the combustion, the mixture temperature - at a constant final pressure, however increased compression ratio - after compression can be kept significantly lower than is the case with the HTI process described above. The cooling effect required for this is achieved by evaporating the supplied or injected water and the heat of evaporation released in the process.

With this procedure, the final pressure after the compression of the combustion air is designed so that it is compressed along the saturation line of water - i.e. the boundary between wet and superheated steam - so that the water that is supplied or injected is completely evaporated without it is overheated; thus the optimal cooling effect is achieved. Only then is the medium to be burned fed to the internal combustion engine. As an alternative to this, this supply can also take place at least temporarily together with the supply of the combustion air. In the latter case, however, the combustible medium is advantageously only supplied to the internal combustion engine towards the end of the period in which the combustion air is supplied.

The method described above makes it possible to keep the combustion temperature lower compared to the HTI method. Although this results in reduced thermal efficiency, the thermal losses are comparatively low.

However, this procedure also has the disadvantages that, on the one hand, thermal energy is lost in the exhaust gas and, on the other hand, the high working temperatures lead to reduced material strengths. Furthermore, only comparatively low ignition pressures are achieved, and if these ignition pressures increase, as can be achieved, for example, by increasing the compression ratio, this results in an increase in efficiency. Task of the present. The invention is to provide a generic method for supplying a medium in an internal combustion engine, which avoids the aforementioned disadvantages, in particular reduces the described thermal losses of an internal combustion engine.

To achieve this object, a generic method is proposed, which is characterized in that water vapor is supplied to the combustion air in the final phase of compression and / or after compression has taken place.

Here, the supply of water vapor at top dead center is preferably isochoric or essentially isochoric.

The term "essentially isochoric" should be understood to mean a supply of water vapor in which the position of the piston changes by no more than 10% in relation to its entire stroke.

If the water vapor is supplied before top dead center, additional compression work would have to be carried out, while relaxation work is lost again when the water vapor is supplied after top dead center.

According to the invention, the isochoric or essentially isochoric supply of the water vapor in the final phase of the compression and / or after the compression of the combustion air has resulted in the mass, temperature and pressure of the medium in the respective combustion chambers or cylinders of the

Internal combustion engine increased. During combustion, the increased masses result in lower working temperatures, which result in higher material strengths. This enables the higher pressures to be absorbed, which in turn leads to an increase in efficiency. With this procedure, more relaxation work can be gained.

According to an advantageous embodiment of the method according to the invention, the temperature of the water vapor supplied is up to a temperature of 1000 ° C. above the saturation line of water at the respective pressure. The pressure of the supplied water vapor is preferably chosen between 100 and 300 bar.

It has been shown that the best results are achieved with the aforementioned temperature and pressure ranges. In principle, however, it is also possible to work in other temperature and / or pressure ranges.

The method according to the invention in an advantageous further development is proposed that the water vapor supplied to the internal combustion engine is provided by means of cooling the one or one of the exhaust gas streams of the internal combustion engine.

For this purpose, the exhaust gas stream (s) of the internal combustion engine is or are subjected to cooling in a condenser, the water obtained is compressed, then, preferably in an exhaust gas heat exchanger, heated and evaporated at the same time before it is fed to the internal combustion engine.

Alternatively or additionally, water which is subjected to the aforementioned procedure can also be provided in a (separate) storage container.

In particular due to the above-described heat recovery from the exhaust gas stream (s), the overall efficiency of the method according to the invention is significantly increased.

It is particularly advantageous if the method according to the invention is combined with the procedure described above - that is to say the at least temporary joint supply of combustion air and water.

In the case of the above-described supply of water, this is preferably supplied under conditions which make it possible for the supplied water to evaporate substantially completely.

With regard to the medium to be fed to the internal combustion engine, that is to say, for example, the hydrogen, it is recommended that the medium be at least at ambient temperature, preferably at a temperature, before it is fed into the internal combustion engine Temperature of at least 500 ° C and heated to the internal combustion engine at a pressure between 100 and 500 bar, preferably at a pressure between 200 and 300 bar.

In this case, the medium can be heated to the aforementioned temperatures at least partially by heat exchange with the or one of the exhaust gas streams of the internal combustion engine.

The pressure at which the water is fed to the internal combustion engine is or is preferably between 5 and 250 bar, in particular between 50 and 150 bar.

The method according to the invention enables lower working temperatures to be achieved in the combustion chambers of internal combustion engines and, in connection with this, a corresponding protection of the materials used for the internal combustion engine or its combustion chambers. In addition, the heat losses of an internal combustion engine can be reduced. With the same consumption of combustible medium, the performance can also be increased; in particular, the part-load behavior of the internal combustion engine is improved.

For conventional fuels - this means diesel and petrol or

Hydrocarbon-based fuels - without a disproportionately high technical effort, adequate water condensation from or the exhaust gas streams of the internal combustion engine should not be possible. When using these fuels, additional water is usually provided or must be obtained in another way.

The method according to the invention is fundamentally suitable for all known media which can be burned in an internal combustion engine, such as cryogenic media - for example hydrogen -, natural gas and all types of diesel and gasoline fuels.

The method according to the invention for supplying a medium which is combustible in an internal combustion engine and further refinements thereof are explained in more detail below with reference to the exemplary embodiments illustrated in FIGS. 1 to 3. The three exemplary embodiments each show hydrogen-powered internal combustion engines M. Here show:

Figure 1: A first embodiment of the method according to the invention

Figure 2: A second embodiment of the method according to the invention, in which the above-described HTI method is additionally implemented

Figure 3: A third embodiment of the method according to the invention, in which the above-described Advanced HTI method is additionally implemented

FIGS. 1, 2 and 3 show a multi-cylinder internal combustion engine M, which is only shown schematically and to which or whose cylinder spaces the combustion air required for the combustion is supplied via line 1. In addition, in the embodiment of the method according to the invention shown in FIG. 1, hydrogen is supplied via line 1 in the form of a hydrogen / air mixture formed by an external mixture formation. As already described, the water vapor required for the method according to the invention is obtained by the condensation of the water vapor contained in the exhaust gas stream of the internal combustion engine M.

As shown in FIG. 1, the exhaust gas of the internal combustion engine M is drawn off via the exhaust gas line 2, cleaned in an optionally provided catalytic converter K and cooled in a first heat exchanger E1 connected downstream of the catalytic converter K against the water vapor stream 5 to be explained. Subsequently, in a second heat exchanger E2 - preferably against ambient air - the exhaust gas stream is cooled further before it is fed to a condenser or ■ water separator W. The exhaust gas stream treated in this way is then discharged via line 3 - as a rule via an exhaust not shown in FIGS. 1 to 3. The water obtained in the condenser or water separator W is first fed via line 4 to an optional filter F and then to an (intermediate) water reservoir S which is also optionally provided.

The filter F is to be provided at least whenever the water has dissolved particles, such as burnt lubricant components, which have to be removed before the water is supplied to the internal combustion engine M. The water reservoir S serves as a buffer in order to be able to ensure an adequate supply of water or steam to the internal combustion engine M at all times. In particular in the start-up phase of the internal combustion engine M or in the event of load changes, insufficient water or water vapor may possibly be obtained using the condenser or water separator W.

According to the invention, the water is now drawn off from the water reservoir S via line 5, in which at least one water pump P is provided, fed to heat exchanger E1 and evaporated in line 2 against the exhaust gas stream to be cooled. The water vapor is then fed to the internal combustion engine M or its cylinder chamber or chambers.

The amount of water vapor supplied to the internal combustion engine M or its cylinder chamber or chambers can be varied by means of appropriate injection valves 8.

In the embodiments of the method according to the invention shown in FIGS. 2 and 3, the exhaust gas stream drawn off from the internal combustion engine M via the exhaust line 2 is cooled in three heat exchangers E1, E1 'and E2 connected in series before the water required in the condenser or water separator W. is separated from the cooled exhaust gas stream.

In contrast to the embodiment of the method according to the invention described in FIG. 1, a control valve 9 is now provided in the water vapor line 6. After this, the water vapor stream is mixed with the hydrogen stream which is brought in via lines 10 and 11 and which was heated in heat exchanger E1 'and the like Flow rate is also adjustable by means of a control valve 12. The combined water vapor / hydrogen stream is then fed to the internal combustion engine M via the line 7.

In the embodiment of the method according to the invention shown in FIG. 3, in contrast to the embodiment shown in FIG. 2, a partial flow of the water withdrawn from the (intermediate) water reservoir S is fed via line 5 'and corresponding injection valves 13 to the internal combustion engine M or its cylinder space or spaces supplied.

Claims

claims

1. A method for supplying a combustible medium in an internal combustion engine, combustion air being supplied before and / or at least temporarily together with the supply of the medium and being compressed in the combustion chamber (s) of the internal combustion engine, characterized in that in the final phase of compression and / or after Once the combustion air has been compressed, water vapor (5 ', 6, 7) is supplied.

2. The method according to claim 1, characterized in that the supply of water vapor (5 ', 6, 7) is isochoric or essentially isochoric at top dead center.

3. The method according to claim 1 or 2, characterized in that the temperature of the supplied water vapor (5 ', 6, 7) is up to a temperature of 1000 ° C above the saturation line of water at the respective pressure.

4. The method according to any one of the preceding claims 1 to 3, characterized in that the pressure of the supplied water vapor (5 ', 6, 7) is 100 to 300 bar.

5. The method according to any one of the preceding claims 1 to 4, characterized in that the water vapor (5 ', 6, 7) supplied to the internal combustion engine (M) by means of cooling (E1, E1', E2) of the or one of the exhaust gas streams (2 ) of the internal combustion engine (M) is provided.

6. The method according to any one of the preceding claims 1 to 5, characterized in that water is supplied at least temporarily together with the supply of the combustion air (1).

A method according to claim 6, characterized in that the water is supplied under conditions that allow a substantially complete evaporation of the water supplied.

8. The method according to any one of the preceding claims 1 to 7, characterized in that the medium before being fed into the internal combustion engine (M) is heated to at least ambient temperature, preferably to a temperature of at least 500 ° C, and the internal combustion engine (M) with a pressure between 100 and 500 bar, preferably at a pressure between 200 and 300 bar.

9. The method according to claim 8, characterized in that the heating of the medium takes place at least partially in the heat exchange (E1, E1 ') with the or one of the exhaust gas streams (2) of the internal combustion engine (M).

10. The method according to any one of the preceding claims 6 to 9, characterized in that the water is supplied to the internal combustion engine (M) at a pressure between 5 and 250 bar, preferably between 50 and 150 bar.