Gas engine and method for operating it

Abstract

Gas engine (10), with at least one cylinder (11), wherein the or each cylinder (11) comprises a main combustion chamber (12) for the combustion of a fuel gas-air mixture and a purged pre-chamber (13) coupled to the main combustion chamber (12) via a transfer port (14), and with at least one exhaust gas turbocharger (15) comprising a turbine (16) for expansion of the exhaust gas leaving the or each cylinder (11) and a compressor (18, 22) for compression of air supplied to the or each cylinder (11), characterized by several air paths for the air supplied to the or each cylinder (11), wherein at least air can be compressed via a first air path (17) with a first compressor (18) and supplied to the main combustion chamber (12) of the or each cylinder (11), and wherein a fuel gas-air mixture can be compressed via a second air path (21) with a second compressor (22) and supplied to the pre-chamber (13) of the or each cylinder (11) can be supplied,wherein the first air path (17) and the second air path (21) are coupled via a check valve (27) such that a portion of the fuel gas-air mixture compressed in the second compressor (22) can be introduced from the second air path (21) into the first air path (17) downstream of the first compressor (18), wherein a further compressor (37) is assigned to the second air path (21) downstream of the second compressor (22), wherein the further compressor (37) is arranged in the second air path (21) downstream of the second compressor (22), and wherein a coupling line (26) comprising the check valve (27) of the first and second air paths (17, 21) branches off from the second air path (21) towards the first air path (19) between the second compressor (22) and the further compressor (37).

Description

[0001] The invention relates to a gas engine and a method for operating a gas engine.

[0002] Gas engines known from practice, which are used for the combustion of a gaseous fuel, have at least one cylinder, in which a fuel-air mixture is burned. The cylinders of gas engines known from practice typically have a main combustion chamber and a pre-chamber coupled to the main combustion chamber via at least one transfer port. It is known to supply the main combustion chamber with a fuel-air mixture of fuel gas and air, with pure fuel gas being supplied to the pre-chamber for scavenging. Furthermore, it is common practice in gas engines known from practice to supply exhaust gas, which is produced during the combustion of the fuel-air mixture in the cylinders of the gas engine, to one or more exhaust gas turbochargers, namely a turbine of an exhaust gas turbocharger, whereby energy gained during the expansion of the exhaust gas in the turbine is used to supply air, so-called charge air, to at least each cylinder.Combustion air is compressed. In gas engines known from practical experience, the fuel gas can be mixed with the compressed charge air either before or after the compressor via one or more mixing points.

[0003] Such gas engines can be found, for example, in DE 197 48 078 A1, DE 35 06 217 A1, DE 44 19 429 A1, DE 10 2013 201 710 A1 and CH 238 900 A.

[0004] There is a growing need to improve the efficiency of gas engines and reduce exhaust emissions.

[0005] Based on this, the present invention aims to create a novel gas engine and a method for operating a gas engine. This objective is achieved by a gas engine according to claim 1. According to the invention, the gas engine has several air paths for the combustion air to be supplied to the cylinder(s), wherein at least air can be compressed via a first air path with a first compressor and supplied to the main combustion chamber of the cylinder(s), and wherein a fuel gas-air mixture can be compressed via a second air path with a second compressor and supplied to the pre-chamber of the cylinder.

[0006] According to the invention, two air paths for combustion air are provided: the first air path, through which compressed combustion air can be supplied to the main combustion chamber of the cylinder(s), and the second air path, through which a compressed fuel-gas-air mixture can be supplied to the pre-chamber of the cylinder(s) for scavenging. According to the invention, the scavenging of the pre-chamber of the cylinder(s) is therefore not carried out with pure fuel gas, but rather with a fuel-gas-air mixture. This improves ignition conditions and thus ensures optimized combustion of the fuel gas, thereby improving efficiency and reducing exhaust emissions.

[0007] In a further advantageous development, the first and second air paths are coupled via a check valve such that a portion of the fuel gas-air mixture compressed in the second compressor can be introduced from the second air path into the first air path downstream of the first compressor. This allows the gas engine to be operated particularly efficiently.

[0008] Preferably, the first compressor of the first air path compresses a fuel gas-air mixture and supplies it to the main combustion chamber of the cylinder(s). The variant in which the first compressor also compresses a fuel gas-air mixture is particularly preferred.

[0009] In a further advantageous configuration, the first air path, however, does not interact with the second air path via exhaust gas recirculation. The exhaust gas recirculation diverts exhaust gas upstream of the turbine and feeds it downstream of the first compressor into the first air path, and / or diverts it downstream of the turbine and feeds it upstream of the first compressor into the first air path. The advantages of both air paths become particularly apparent when the gas engine utilizes exhaust gas recirculation. The higher the exhaust gas recirculation rate, the greater the benefit of the mixture-scavenged pre-chamber of the respective cylinder with regard to efficiency improvement and exhaust emission reduction.Purging the pre-chamber with a fuel-air mixture, particularly in gas engines with exhaust gas recirculation, can significantly improve homogeneity in the pre-chamber, resulting in accelerated combustion pressure and considerably less soot formation during combustion. This leads to reduced soot deposits in the pre-chamber and on the ignition device used to ignite the fuel-air mixture.

[0010] Preferably, a further compressor is assigned to the second air path downstream of the second compressor, wherein the further compressor is arranged in the second air path downstream of the second compressor, and wherein a coupling line with a check valve for the first and second air paths branches off from the second air path towards the first air path between the second compressor and the further compressor. The further compressor ensures that the pressure of the fuel-air mixture in the second air path is always above the pressure in the pre-chamber of the respective cylinder, so that the pre-chamber of the respective cylinder can always be reliably purged with the fuel-air mixture. The use of the further compressor is particularly advantageous if this pressure cannot always be maintained or set via the second compressor.In this case, the appropriate pressure for the fuel gas-air mixture in the second air path can then be set via a further compressor, preferably driven by an electric motor.

[0011] The first and second compressors can be driven together from a common turbine or from separate turbines. If the first and second compressors can be driven from a common turbine, the equipment complexity can be reduced.

[0012] The method for operating a gas engine is defined in claim 11.

[0013] Preferred embodiments of the invention are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1: a first gas engine according to the invention; Fig. 2: a second gas engine according to the invention; Fig. 3: a third gas engine according to the invention; and Fig. 4: a fourth gas engine according to the invention.

[0014] The invention presented here relates to a gas engine and a method for operating such a gas engine.

[0015] Fig. Figure 1 shows a highly schematic diagram of a first gas engine 10 according to the invention, comprising several cylinders 11. Each of the cylinders 11 has a main combustion chamber 12 and a pre-chamber 13, wherein the pre-chamber 13 is coupled to the main combustion chamber 12 of the respective cylinder 11 via a transfer channel 14.

[0016] In the cylinders 11 of the gas engine 10, specifically in the area of ​​the main combustion chambers 12 of the cylinders 11, a mixture of fuel gas and air is burned, whereby the resulting exhaust gas is passed through an exhaust gas turbocharger 15, namely a turbine 16 of the exhaust gas turbocharger 15. The energy recovered in the area of ​​the turbine 16 of the exhaust gas turbocharger 15 is used to compress combustion air, which is then supplied to the cylinders 11 of the gas engine 10 as compressed combustion air or charge air.

[0017] The gas engine 10 according to the invention has several air paths for the combustion air, wherein at least air 19 is compressed via a first air path 17 with a first compressor 18 and supplied to the main combustion chamber 12 of the respective cylinder 11 as compressed charge air 20, and wherein air 19 and fuel gas 23 are compressed via a second air path 21 to a second compressor 22 in the form of a fuel gas-air mixture 24 and supplied as a compressed fuel gas-air mixture 25 to the pre-chambers 13 of the cylinders 11.

[0018] By purging the pre-chambers 13 of the cylinders 11 of the gas engine 10 with the fuel-air mixture 25, better ignition conditions can be provided, resulting in improved combustion and thus an increase in efficiency. Furthermore, lower exhaust emissions can be ensured.

[0019] The first air path 17 and the second air path 21 are connected or coupled via a coupling line 26 with a check valve 27 connected in the coupling line 26, in such a way that, starting from the second air path 21, a part of the fuel gas-air mixture 25 compressed in the second compressor 22 can be introduced into the first air path 17 downstream of the first compressor 18, whereas an overflow from the first air path 17 into the second air path 21 is excluded.

[0020] In the exemplary embodiment of the Fig. 1 Both compressors 18, 22 of the two air paths 17, 21 can be driven from the common turbine 16.

[0021] Fig. It can be seen from Figure 1 that a charge air cooler 28 is integrated into the first air path 17 downstream of the coupling line 26 and thus also downstream of the first compressor 18.

[0022] The supply of the fuel gas-air mixture 24 to be compressed in the second compressor 22 of the second air path 21 is carried out via a mixing device 29, which mixes fuel gas 23 with combustion air 19, wherein this mixing device 29 may preferably be a Venturi nozzle.

[0023] Fig. Figure 2 shows a further development of the gas engine 10 of the Fig. 2, wherein, to avoid unnecessary repetition, for the exemplary embodiment of the Fig. Two identical reference numerals are used, as in the exemplary embodiment of the Fig. 1 and subsequently only those details will be discussed that distinguish the exemplary embodiment of the Fig. 2 from the exemplary embodiment of the Fig. 1 distinguishes.

[0024] Those optional, but preferred, further training courses that Fig. 2 shows that they can be used either alone or in any combination with each other on the gas engine 10 of the Fig. 1 will be used.

[0025] In the case of the gas engine 10 of the Fig. 2. The first compressor 18 of the first air path 17 serves not exclusively for the compression of combustion air 19, but for the compression of the combustion air 19 as well as the fuel gas 23, wherein a corresponding fuel gas-air mixture 30 is provided by a mixing device 31, which in turn is preferably designed as a Venturi nozzle. Downstream of the first compressor, a compressed fuel gas-air mixture 30' is then present.

[0026] Furthermore, in the case of the gas engine, 10 of the Fig. 2. It is provided that the same uses at least one exhaust gas recirculation system, wherein, via a first exhaust gas recirculation system 32, exhaust gas can be diverted upstream of the turbine 16 and directed downstream of the first compressor 18 towards the first air path 17 and mixed downstream of the first compressor 18 with the compressed fuel gas-air mixture 30'. Alternatively or additionally, via a second exhaust gas recirculation system 33, exhaust gas can be diverted downstream of the turbine 16 and mixed upstream of the first compressor 18 with the fuel gas-air mixture 30. In this case, the first compressor 18 then compresses a mixture of exhaust gas, fuel gas, and charge air. The exhaust gas recirculation system 32 uses a control element 34, and the exhaust gas recirculation system 33 uses a control element 35, to adjust the amount of recirculated exhaust gas. The control elements 34 and 35 are typically exhaust gas recirculation valves.Downstream of the control element 35, a heat exchanger 36 is integrated into the exhaust gas recirculation 33 to cool the recirculated exhaust gas.

[0027] Another difference of the gas engine 10 of the Fig. 2 compared to the gas engine 10 of the Fig. The feature consists of the integration of a further compressor 37 in the second air path 21 downstream of the second compressor 22, with the coupling line 26, via which the two air paths 17, 21 are coupled, branching off from the second air path 21 between the two compressors 22, 37 of the second air path 21 and leading towards the first air path 17. This further compressor 37 can be used for further compression of the fuel-air mixture 25 in order to always ensure a pressure level that guarantees reliable purging of the pre-chambers 13 with the fuel-air mixture. The pressure of the fuel-air mixture in the second air path 21 is always above the pre-chamber pressure. Preferably, the pressure downstream of the second compressor 22 in the second air path 21 is greater than the pressure downstream of the first compressor 18 in the first air path 17. This can be ensured by a corresponding configuration of the compressors 18, 22.Alternatively or additionally via the further compressor 37, which is preferably driven by an electric motor.

[0028] Another variant of the invention shows Fig. 3, wherein in Fig. Figure 3 shows a gas engine 10 comprising two exhaust gas turbochargers 15 and thus two turbines 16. Exhaust gas from cylinders 11 of a first cylinder group is routed via the exhaust gas turbocharger 15 or the turbine 16 of the exhaust gas turbocharger 15 that drives the first compressor 18 of the first air path 17, whereas exhaust gas from cylinders 11 of a second cylinder group is supplied to the turbine 16 of the exhaust gas turbocharger 15 that drives the second compressor 19 of the second air path 21. In the exemplary embodiment of the Fig. 3 are therefore, in contrast to the exemplary embodiment of the Fig. 1. The two compressors 18, 22 are driven by separate turbines 16. However, with regard to all other details, the embodiment of the Fig. 3 with the exemplary embodiment of the Fig. 1. Therefore, to avoid unnecessary repetition, we refer to the explanations regarding the exemplary embodiment of the Fig. 1 is referred to.

[0029] Fig. Figure 4, which shows a further embodiment of a gas engine 10 according to the invention, illustrates that in the case of the gas engine 10 the Fig. 3, whose compressors 18, 22 are driven by separate turbines 16, which are connected with Fig. 2 further developments can be used, namely the compression of the fuel gas-air mixture 30 in the first compressor 18 of the first air path 17 and / or the use of exhaust gas recirculation 32 in the first air path 17 and / or the use of exhaust gas recirculation 33 in the first air path 17 and / or the use of the further compressor 32 in the second air path 21. With regard to these details, the following applies to the exemplary embodiment of the Fig. 4. Refer to the explanations regarding the exemplary embodiment of the Fig. 2 referred.

[0030] All exemplary embodiments of the Fig. 1, Fig. 2, Fig. 3 to Fig. 4 is common in that the gas engine 10 uses two air paths 17, 21 with separate compressors 18, 22, whereby in the first air path 17 at least combustion air 19 is compressed, possibly mixed with exhaust gas and / or fuel gas, whereas in the second air path 21 air 19 is always compressed with fuel gas 23 in order to purge pre-chambers 13 of the cylinders 11 with a fuel gas-air mixture.

[0031] Then, if the gas engine 10 is to be operated as a lean-burn engine with a lambda value greater than 1, preferably only air 19 is compressed in the first air path 17, whereas in the second air path 21 the mixture 24 of air 19 and fuel gas 23 is compressed.

[0032] Then, if the gas engine 10 is preferably to be operated as a stoichiometric lean-burn engine with a lambda value of approximately 1, the exhaust gas recirculation 32 and / or the exhaust gas recirculation 33 is used in the first air path 17 to supply the main combustion chambers 12 of the cylinders 11 with a mixture of combustion air 19 and exhaust gas via the first air path 17.

[0033] Then, if the gas engine 10 is to be used as a stoichiometric gas engine with a lambda value of approximately 1 in combination with a 3-way catalytic converter, air 19, fuel gas 23 and exhaust gas are preferably routed via the first air path 17, preferably as shown in Fig.4 shown, such that in the first compressor 18 of the first air path 17 the mixture 30 of fuel gas 23 and combustion air 19 is mixed, and that either exhaust gas is supplied to the mixture 30 and / or 30' via the exhaust gas recirculation 32 downstream of the first compressor 18 and / or via the exhaust gas recirculation 33 upstream of the first compressor 18.

[0034] The invention enables gas engines to achieve an increase in thermodynamic efficiency, improved combustion in the main combustion chambers of the cylinders, lower exhaust emissions, reduced soot formation, and a reduction in soot deposits in the area of ​​the pre-chambers and in the area of ​​ignition devices associated with the pre-chambers, which serve for spark ignition in the area of ​​the pre-chambers. Preferably, gas engines with exhaust gas recirculation are used, in particular stoichiometric gas engines with exhaust gas recirculation and a three-way catalytic converter. Reference symbol list 10 Gas engine 11 cylinders 12 Main combustion chamber 13 Atrium 14 Overflow channel 15 exhaust gas turbochargers 16 Turbine 17 first air path 18 compressors 19 air 20 compressed air 21 second air path 22 compressors 23 Fuel gas 24 Fuel gas-air mixture 25 compressed fuel gas-air mixture 26 coupling line 27 Check valve 28 Intercoolers 29 Mixing device 30 Fuel gas-air mixture 31 Mixing device 32 Exhaust gas recirculation 33 Exhaust gas recirculation 34 Control device 35 Control device 36 heat exchangers 37 compressors

Claims

[1] Gas engine (10), comprising at least one cylinder (11), wherein the or each cylinder (11) comprises a main combustion chamber (12) for the combustion of a fuel gas-air mixture and a purged pre-chamber (13) coupled to the main combustion chamber (12) via a transfer port (14), and comprising at least one exhaust gas turbocharger (15) comprising a turbine (16) for expansion of the exhaust gas leaving the or each cylinder (11) and a compressor (18, 22) for compression of air supplied to the or each cylinder (11), characterized byseveral air paths for the air to be supplied to the or each cylinder (11), wherein at least air can be compressed via a first air path (17) with a first compressor (18) and supplied to the main combustion chamber (12) of the or each cylinder (11), and wherein a fuel gas-air mixture can be compressed via a second air path (21) with a second compressor (22) and supplied to the pre-chamber (13) of the or each cylinder (11), wherein the first air path (17) and the second air path (21) are coupled via a check valve (27) such that a portion of the fuel gas-air mixture compressed in the second compressor (22) can be introduced from the second air path (21) into the first air path (17) downstream of the first compressor (18), wherein a further compressor (37) is assigned to the second air path (21) downstream of the second compressor (22), wherein the further compressors (37) are arranged in the second air path (21) downstream of the second compressor (22),wherein a coupling line (26) having the check valve (27) of the first and second air path (17, 21) branches off from the second air path (21) towards the first air path (19) between the second compressor (22) and the further compressor (37). [2] Gas engine according to claim 1, characterized by , that the first compressor (18) of the first air path (17) compresses a fuel gas-air mixture and supplies it to the main combustion chamber (12) of the or each cylinder (11). [3] Gas engine according to claim 1 or 2, characterized by , that the first air path (17) does not interact with the second air path (21) in conjunction with exhaust gas recirculation (32, 33). [4] Gas engine according to claim 3, characterized by , that the exhaust gas recirculation (32) diverts exhaust gas upstream of the turbine (16) and feeds it downstream of the first compressor (18) to the first air path (17). [5] Gas engine according to claim 3 or 4, characterized by, that the exhaust gas recirculation (33) diverts exhaust gas downstream of the turbine (16) and feeds it upstream of the first compressor (18) to the first air path (17). [6] Gas engine according to any one of claims 1 to 5, characterized by , that the first compressor (18) and the second compressor (22) can be driven together from a common turbine (16). [7] Gas engine according to any one of claims 1 to 5, characterized by , that the first compressor (18) and the second compressor (22) can be driven from separate turbines (16). [8] Method for operating a gas engine (10), in particular a gas engine according to any one of claims 1 to 7, wherein the gas engine (10) has at least one cylinder (11), wherein the or each cylinder (11) comprises a main combustion chamber (12) for combustion of a fuel gas-air mixture and a purged pre-chamber (13), and wherein the gas engine (10) has at least one exhaust gas turbocharger (15) comprising a turbine (16) for expansion of the exhaust gas leaving the or each cylinder (11) and a compressor (18, 22) for compression of the air supplied to the or each cylinder (11), characterized by , that at least air is compressed via a first air path (17) with a first compressor (18) and supplied to the main combustion chamber (12) of the or each cylinder (1), and that a fuel gas-air mixture is compressed via a second air path (21) with a second compressor (22) and supplied to the pre-chamber (13) of the or each cylinder (11). [9] Method according to claim 8, characterized by , that from the second air path (21) a part of the fuel gas-air mixture compressed in the second compressor (22) is introduced into the first air path (17) downstream of the first compressor (18). [10] Method according to claim 8 or 9, characterized by , that in the first compressor (18) of the first air path (17) a fuel gas-air mixture is compressed. [11] Method according to any one of claims 8 to 10, characterized by , that exhaust gas is supplied to the first air path (17) but not to the second air path (21) via exhaust gas recirculation (32, 33).

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