MIXTURE FORMATION DEVICE FOR A GAS ENGINE AND GAS ENGINE

Abstract

The invention relates to a mixture formation device for an internal combustion engine that is operated with a combustible gas, preferably compressed natural gas (CNG). The mixture formation device comprises a combination of a quantity regulator, a gas mixer, a flow guide element to recover pressure as well as a connection capability for recirculating the exhaust gas of the internal combustion engine. Owing to the mixture formation device according to the invention, a gas tank can be emptied down to a relatively low pressure of approximately 2 bar, whereby an excellent mixture formation is achieved over the entire speed and load ranges of the internal combustion engine. It is provided that, owing to the mixture formation device according to the invention, the installation space requirements as well as the production costs can be reduced in comparison to prior-art solutions. Moreover, an internal combustion engine operated with a combustible gas, especially natural gas (CNG), is being put forward which has such a mixture formation device in its intake tract.

Claims

1. A mixture formation device for installation in an intake channel of an internal combustion engine operated with a combustible gas, comprising: a closing member with which the opening cross section of the intake channel of the internal combustion engine can be reduced, at least one metering valve for metering the combustible gas into the intake channel of the internal combustion engine, at least one connector for an exhaust gas recirculation line of the internal combustion engine, wherein the deflecting geometry of the closing member diverts a fresh air stream into a diffuser, whereby a first feed point for the combustible gas and a second feed point for the gas that has been recirculated via the exhaust gas recirculation line are arranged downstream from the place with the deflecting geometry.

2. The mixture formation device according to claim 1, wherein the at least one metering valve meters the combustible gas into a fuel gas distribution ring that is connected via a channel to the diffuser of the intake channel.

3. The mixture formation device according to claim 2, wherein the channel runs essentially perpendicular to an outflow opening of the metering valve.

4. The mixture formation device according to claim 1, wherein the exhaust gas recirculation line has an exhaust gas recirculation distribution ring that runs around an intake pipe of the intake channel, at least in certain sections.

5. The mixture formation device according to claim 1, wherein the closing member has a deflecting section to guide the flow of the fresh air, of the combustible gas and/or of the recirculated exhaust gas as well as a guide section with which the closing member is positioned in a housing of the mixture formation device.

6. The mixture formation device according to claim 5, wherein the guide section is positioned on a closed section of the housing.

7. The mixture formation device according to claim 5, wherein a gasket is arranged between the guide section and the housing.

8. The mixture formation device according to claim 5, wherein the closing member is hollow in the area of the guide section and surrounds an equalization volume.

9. The mixture formation device according to claim 1, wherein the second feed point for the exhaust gas recirculation line is located downstream from the first feed point for the gas, as seen in the flow direction of the fresh air through the intake channel.

10. The mixture formation device according to claim 1, the gap width of the diffuser amounts to approximately to 1/800 of the diameter of an intake pipe of the intake channel.

11. The mixture formation device according to claim 1, wherein the closing member is a valve having a shaft and a disk, whereby the valve disk has a first, radially inner section that runs at a first angle relative to the valve shaft, and a second, radially outer section that runs at an angle relative to the valve shaft that is greater than that of the first section.

12. The mixture formation device according to claim 11, wherein the diffuser is formed downstream from the closing member.

13. The mixture formation device according to claim 1, wherein a recess is formed on the valve disk or on a wall of the diffuser located opposite from the valve disk, and a projection that protrudes into the recess is formed on the appertaining opposite component.

14. The mixture formation device according to claim 1, wherein the first feed point and the second feed point are arranged along a shared diameter.

15. A gas engine comprising at least a combustion chamber, an intake channel, an exhaust gas channel, an exhaust gas recirculation line as well as a mixture formation device according to claim 1, whereby a combustible gas for operating the gas engine is metered into the intake channel of the gas engine by means of a regulatable metering valve upstream from the combustion chamber.

Description

[0029] The invention will be explained in greater detail below in embodiments on the basis of the accompanying drawings. Identical components or components having the same function are designated here with the same reference numerals. The following is shown:

[0030] FIG. 1: a schematic diagram of an internal combustion engine;

[0031] FIG. 2: a first embodiment of a mixture formation device according to the invention, in a sectional view;

[0032] FIG. 3: the mixture formation device shown in FIG. 2, in a three-dimensional view;

[0033] FIG. 4: a second embodiment of a mixture formation device according to the invention, in a sectional view;

[0034] FIG. 5: the mixture formation device shown in FIG. 4, in a three-dimensional view;

[0035] FIG. 6: a first embodiment of a valve seat of a mixture formation device according to the invention;

[0036] FIG. 7: another embodiment of a valve seat of a mixture formation device according to the invention;

[0037] FIG. 8: another embodiment of a valve seat of a mixture formation device according to the invention;

[0038] FIG. 9: another embodiment of a valve seat of a mixture formation device according to the invention;

[0039] FIG. 10: a valve seat of a mixture formation device according to the invention according to the invention, with the valve partially closed.

[0040] FIG. 1 shows a greatly simplified structure of an internal combustion engine 1 with four combustion chambers 2, an intake channel 3 as well as an exhaust gas channel 4. Here, an exhaust gas recirculation line 5 is provided which connects the exhaust gas channel 4 to the intake channel 3 and thus allows burned fuel contents to be recirculated to the intake channel 3 of the internal combustion engine 1. The internal combustion engine 1 in the embodiment described below is configured as a gas engine 1 and is operated with a gaseous fuel, preferably by natural gas (compressed natural gasCNG). As an alternative, operation with a liquefied gas (liquefied natural gasLNG) is likewise possible. Gas engines 1 differ from classic internal combustion engineswhere a liquid fuel is metered into the intake channel 3 or into the combustion chambers 2in that the fuel is gaseous and thus highly compressible at ambient temperature and ambient pressure. As a result, the gaseous fuel cannot, or at least not efficiently, be introduced into the combustion chambers 2 of the internal combustion engine 1 by means of conventional injection technology, especially by means of an injection pump and/or a fuel injection system. Moreover, natural gas cannot be liquefied at room temperature, as a result of which the use of fuel injection technology for liquid fuels likewise falls by the wayside. For this reason, alternative mixture formation devices that are specifically adapted to the special characteristics of a gaseous fuel have been developed for gas engines 1. Here, the mixture is preferably formed in the intake channel 3 upstream from the combustion chambers 2 of the internal combustion engine 1 since the pressure level at this place is lower than in the combustion chambers 2 and consequently, the gas tank can be emptied to a greater extent.

[0041] FIG. 2 shows a first embodiment of a mixture formation device 10 according to the invention for an internal combustion engine 1 operated with a gaseous fuel. The mixture formation device 10 comprises a housing 42 in which a closing member 12, especially a valve 54, is arranged so that it can be moved. The housing 42 has a first section which runs vertically in the drawing plane and in which an intake pipe 36 is formed. The housing 42 also has a second section that forms a diffuser 22. The diffuser 22 runs at an angle of approximately 100 to 120 relative to the intake pipe 36. The housing 42 also has a closed housing section 44 which, together with the closing member 12, delimits an equalization volume 48. The closing member 12 is configured as a valve 54, especially as a disk valve, and it has a shaft 56 and a disk 58. The valve shaft 56 and the valve disk 58 form on their side facing the intake pipe 36 a deflecting section 38 through which the fresh air that is flowing through the mixture formation device is guided and deflected. Between the valve shaft 56 and the valve disk 58, a deflecting geometry is formed by means of which the fresh air that is flowing into the mixture formation device is deflected into the diffuser 22. The valve disk 58 is followed by a guide section 40 in which the valve 54 is installed in the closed housing section 44. The closing member 12 is configured in the area of the guide section 40 so as to be hollow and it surrounds the equalization volume 48. Between the guide section 40 and the housing wall of the closed housing section 44, there is a gasket 46 that is designed to prevent fresh air from penetrating into the equalization volume 48.

[0042] The mixture formation device 10 also has at least one receiving opening, preferably, as shown in FIG. 1, several receiving openings 78 which are preferably uniformly distributed along the circumference of the mixture formation device 10 and in each of which a metering valve 16 that serves to feed in a combustible gas is arranged. On the circumference of the metering valve 16, there is a gasket 76, especially a sealing ring, by means of which a gap between the metering valve 16 and the receiving opening 78 is sealed off, thus preventing an uncontrolled escape of the combustible gas from the mixture formation device 10. Each one of the receiving openings 78 is connected to a fuel gas distribution ring 28 in which gaseous fuel that has been fed in via the metering valves 16 can be mixed with fresh air. The fuel gas distribution ring 28 is connected to the diffuser 22 via channels 30, whereby each channel 30 runs essentially perpendicular to the diffuser 22. In order to allow combustible gas to be fed into the diffuser 22, at each end of the channel 30 facing the diffuser 22, first feed points 24 are formed via which the channels 30 are fluidically connected to the diffuser 22. Here, the channels 30 run essentially perpendicular to the outflow openings 32 of the metering valves 16. The metering valves 16 are arranged radially here, that is to say, they are oriented perpendicular to the intake pipe 36 of the mixture formation device 10. Each metering valve 16 has a plug 52 with which the metering valves 16 can be electrically contacted with the metering valves 16.

[0043] A connector for an exhaust gas recirculation line 5 of the internal combustion engine 1 is formed on the mixture formation device 10. In this context, the mixture formation device 10 has a distribution ring 34 for the exhaust gas recirculation line, said distribution ring 34 being arranged around the intake pipe 36 of the intake channel 3, at least in certain sections. The second ring channel 34 [sic] runs essentially parallel to the diffuser 22 and it is connected to this diffuser 22 via second feed points 26. In this context, the distribution ring 34 for the exhaust gas line is connected to the exhaust gas recirculation line 5 via at least one connector 18.

[0044] FIG. 3 shows the mixture formation device 10 in a three-dimensional view. It can be seen here that the metering valve 16 is oriented perpendicular to the intake pipe 36 and that it does not project in the radial direction beyond the housing 42 of the mixture formation device 10.

[0045] During operation of the mixture formation device 10, fresh air is drawn into the mixture formation device 10 via the intake pipe 36. At the same time, the combustible gas is metered by means of the metering valve 16 into the fuel gas distribution ring 28, where a first mixing of the combustible gas with the fresh air takes place. Since the gas is deflected from the outflow opening 32 of the metering valve 16 via the wall of the precombustion chamber, and since it is further conveyed through the channel 30 into the diffuser 22, a vortex is formed that brings about a uniform and thorough mixing of fresh air and combustible gas. Downstream from the first feed point 24, the mixture consisting of fresh air and combustible gas is additionally charged with exhaust gas that has been recirculated via the exhaust gas recirculation line 5 and via the distribution ring 34 for the exhaust gas line. For this purpose, at a second feed point 26, the recirculated exhaust gas is fed into the diffuser 22, whereby the exhaust gas is mixed with the mixture consisting of fresh air and combustible gas.

[0046] The closing member 12 has the function of a quantity regulator and can thus replace the throttle valve in a conventional internal combustion engine. In this context, the mixture formation device 10 shown in FIG. 2 is depicted with a completely open valve 54, in other words, maximally unthrottled. When the valve 54 is closed, that is to say, moved in the direction of a seat edge 74 on the housing 42, the opening cross section 14 of the diffuser 22 can be reduced. Such a partially closed valve 54 is shown in FIG. 10. Here, in the area of the guide section 40, the valve disk 58 has a sharp trailing edge in the flow direction of the gas through the diffuser 22, thus causing the formation of a vortex downstream from the valve disk 58, a process in which the wake 80 of the vortex brings about an additional mixing of fresh air, combustible gas and exhaust gas from the exhaust gas recirculation line 5. First of all, the capability to form minute quantities, especially during idling of the internal combustion engine 1, has to be rendered possible, and so does a favorable flow guidance entailing the lowest possible losses during full load operation. The valve 54 is adjusted, for example, by means of an electro-mechanical control element although, as an alternative, this can also be achieved purely mechanically, for example, by means of a spindle, a rocker arm, a toothed gear or the like.

[0047] FIG. 4 shows an alternative embodiment of a mixture formation device 10 according to the invention. Since its structure is essentially identical to the one shown in FIG. 2, only the actual differences will be elaborated upon below. In this embodiment, the metering valves 16 are arranged axially, that is to say, parallel to the intake pipe 36. As a result, additional space is created in the radial direction, so that the available installation space can be optimally utilized. Corresponding to the axial arrangement of the metering valves 16, the shape of the fuel gas distribution ring 28 is adapted accordingly, whereby the channel 30 is formed at one end of the fuel gas distribution ring 28 facing the intake pipe 36 and it is arranged eccentrically relative to the outflow opening 32 of the metering valve 16 in order to attain a commensurate multiple deflection and mixing of the combustible gas with the fresh air in the fuel gas distribution ring 28. FIG. 5 shows this embodiment of a mixture formation device 10 in a three-dimensional view.

[0048] FIG. 6 shows an alternative embodiment of the valve 54 and of the diffuser 22. Here, the disk 58 of the valve 54 has a first, radially inner section 60 and a second, radially outer section 62 that runs an angle relative to the valve shaft 56 that is greater than that of the first section 60. As a result, a diffuser 50 is created between a wall 64 of the housing 42 and the second section 62 of the valve disk 58. As an alternative, the diffuser 50, as shown in FIG. 7, can also be formed between two parts or sections of the housing 42 downstream from the valve disk 58.

[0049] In order to improve the capability of the mixture formation device 10 to form minute quantities, a simple labyrinth gasket can be provided on the seat of the valve 54. Towards this end, as is shown in FIG. 8, a recess 66 can be provided on the wall 64 of the housing 42, whereby a projection 70 on the valve disk 58 engages with said recess 66 when the valve 54 is essentially closed. As an alternative, as shown in FIG. 9, it is also possible for a projection 72 to be formed on the wall 64 of the housing 42, said projection 72 engaging with a recess 68 in the valve disk 58. Thanks to the profiling of the projections 70, 72, the transition from a minute quantity of metered-in combustible gas to an area with greater gas quantities can be improved, as a result of which the comfort during the dynamic operation of the internal combustion engine 1 is enhanced.

LIST OF REFERENCE NUMERALS

[0050] 1 internal combustion engine/gas engine [0051] 2 combustion chamber [0052] 3 intake channel [0053] 4 exhaust gas channel [0054] 5 exhaust gas recirculation line [0055] 10 mixture formation device [0056] 12 closing member [0057] 14 opening cross section [0058] 16 metering valve [0059] 18 connector [0060] 20 pressure equalization hole [0061] 22 diffuser [0062] 24 first feed point [0063] 26 second feed point [0064] 28 fuel gas distribution ring [0065] 30 channel [0066] 32 outflow opening [0067] 34 distribution ring for the exhaust gas line [0068] 36 intake pipe [0069] 38 deflecting section [0070] 40 guide section [0071] 42 housing [0072] 44 closed housing section [0073] 46 gasket [0074] 48 equalization volume [0075] 50 diffuser [0076] 52 plug [0077] 54 valve [0078] 56 valve shaft [0079] 58 valve disk [0080] 60 first section [0081] 62 second section [0082] 64 wall [0083] 66 recess [0084] 68 recess [0085] 70 projection [0086] 72 projection [0087] 74 seat edge [0088] 76 gasket [0089] 78 receiving opening [0090] 80 wake of the vortex