Supercharged gasoline engine with an active pre-chamber and an air intake after the turbocharger

Description

[0001] The invention relates to an internal combustion engine comprising at least one cylinder, wherein the at least one cylinder has a main combustion chamber for combustion of a fuel / air mixture or a fuel / air / exhaust gas mixture and a scavenged pre-chamber fluidically connected to the main combustion chamber via at least one overflow channel and an exhaust gas turbocharger.

[0002] Document WO 2014 / 114846A1 describes a method for operating a multi-cylinder piston engine. It is provided that each cylinder in the engine is provided with a reciprocating piston and a pre-combustion chamber, and the method comprises the steps of introducing gaseous fuel into an intake port of the engine, injecting liquid pilot fuel into the pre-combustion chamber, igniting the liquid pilot fuel by compression by the piston, and utilizing the combustion of the liquid pilot fuel to ignite the gaseous fuel. The exhaust gas is introduced into the pre-combustion chamber prior to the injection of the liquid pilot fuel. In this method, the exhaust gas is cooled before being introduced into the pre-combustion chamber, and the intake air is mixed with the exhaust gas prior to introducing the mixture of exhaust gas and intake air into the pre-combustion chamber.

[0003] Another gasoline engine and an associated method of the generic type for supplying a main combustion chamber with compressed combustion air and a pre-chamber with a fuel / air mixture are known from the document DE 10 2016 112 537 A1. The gasoline engine comprises at least one cylinder, wherein the at least one cylinder comprises a main combustion chamber for combusting a fuel-gas-air mixture and a purged pre-chamber coupled to the main combustion chamber via a transfer channel.The gasoline engine further comprises at least one exhaust gas turbocharger, which has a turbine for expanding exhaust gas leaving the at least one cylinder and a compressor for compressing air to be supplied to the at least one cylinder, wherein a plurality of air paths are provided for the air to be supplied to the at least one cylinder, wherein at least air can be compressed via a first air path with a first compressor and can be supplied to the main combustion chamber of the at least one cylinder, and wherein a fuel gas-air mixture can be compressed via a second air path with a second compressor and can be supplied to the pre-chamber of at least one of each cylinder.

[0004] The prior art also includes the documents AT 13 417 U1 and DE 10 2015 004 741 A1.

[0005] The invention is based on the object of creating a novel generic gasoline engine and a new method for operating the gasoline engine.

[0006] This task is solved by a gasoline engine and an associated method for operating the engine.

[0007] The internal combustion engine according to the invention comprises at least one cylinder, wherein the at least one cylinder has a main combustion chamber for combusting a fuel / air mixture or a fuel / air / exhaust gas mixture and a scavenged pre-chamber fluidically connected to the main combustion chamber via at least one overflow channel, and at least one exhaust gas turbocharger having a turbine for expanding exhaust gas leaving the at least one cylinder and a compressor for compressing fresh air to be supplied to the at least one cylinder or a fresh air / exhaust gas mixture as compressed charge air, wherein a tapping point is formed in a charge air line downstream of the compressor, from which a scavenging line branches off, via which a partial amount of the compressed charge air can be taken for scavenging the at least one pre-chamber, wherein an additional compressor is arranged in the scavenging line, which increases the boost pressure of the compressed charge air as required,wherein the fresh air / exhaust gas mixture can be supplied to the compressor from a fresh air line arranged upstream of the compressor, since the fresh air line is connected upstream of the compressor to an exhaust gas recirculation line of an exhaust gas line, so that exhaust gas can be supplied to the fresh air in the fresh air line, so that a fresh air / exhaust gas mixture can also be extracted as compressed charge air via the extraction point and can be recompressed in the purge line by means of the additional compressor as required, wherein in the purge line downstream of the additional compressor there is a feed point of a fuel supply line for supplying fuel to the charge air which is recompressed as required by means of the additional compressor and is present in the purge line as fresh air or as a fresh air / exhaust gas mixture.

[0008] It is preferably provided that a first charge air cooler is arranged in the charge air line downstream of the compressor in front of the extraction point.

[0009] The extraction point is preferably arranged between the first charge air cooler and a throttle valve of an intake manifold leading to the at least one main combustion chamber.

[0010] It is further preferred that a check valve or a check valve and a buffer tank is / are arranged upstream of the additional compressor in the flushing line.

[0011] The method according to the invention for operating an internal combustion engine is characterized in that the internal combustion engine comprises at least one cylinder, wherein the at least one cylinder has a main combustion chamber for combustion of a fuel / air mixture or a fuel / air / exhaust gas mixture and a scavenged pre-chamber fluidically connected to the main combustion chamber via at least one overflow channel, wherein the internal combustion engine further comprises at least one exhaust gas turbocharger having a turbine for expanding exhaust gas leaving the at least one cylinder and a compressor for compressing fresh air to be supplied to the at least one cylinder or a fresh air / exhaust gas mixture as compressed charge air, wherein the method according to the invention is characterized in that a tapping point is formed in a charge air line downstream of the compressor, from which a scavenging line branches off,via which a partial amount of charge air from the charge air compressed in the compressor of the exhaust gas turbocharger is taken for purging the at least one pre-chamber, wherein in the purge line downstream of an additional compressor there is a supply point of a fuel supply line for supplying fuel to the charge air which is recompressed as needed by means of the additional compressor, which increases the boost pressure of the compressed charge air as needed, so that the at least one pre-chamber is purged with the recompressed fresh air or the recompressed fresh air / exhaust gas mixture, since a fresh air line upstream of the compressor is connected to an exhaust gas recirculation line of an exhaust line, so that exhaust gas can be supplied to the fresh air in the fresh air line, wherein the structural design of the internal combustion engine makes it possible for the compressed charge air, in particular the fresh air or the fresh air / exhaust gas mixture downstream of the additional compressor,fuel is supplied as needed, so that at least one pre-chamber can also be flushed with a recompressed fuel / fresh air mixture or a recompressed fuel / air / exhaust gas mixture.

[0012] The invention is explained below with reference to the accompanying drawing. It shows: Figure 1 shows a schematic representation of an internal combustion engine, in particular a gasoline engine according to the invention with an air supply of an active prechamber for supercharged gasoline engines with an air extraction after an exhaust gas turbocharger.

[0013] The present invention relates to a gasoline internal combustion engine, in particular a gasoline engine operated with a gas or a liquid fuel, and to a method for operating such a gasoline engine.

[0014] Figure 1shows a diagram of the gasoline engine 1 according to the invention, which comprises a plurality of cylinders Z. Each of the cylinders Z has a main combustion chamber BK and a pre-chamber (not explicitly shown), wherein the respective pre-chamber is coupled to the main combustion chamber BK of the respective cylinder Z via at least one transfer channel (not shown).

[0015] In the cylinders Z of the gasoline engine 1, namely in the area of ​​the main combustion chambers BK of the cylinders Z, a mixture of fuel gas and air is burned, with the resulting exhaust gas FA being discharged via an exhaust gas turbocharger 200, in particular via a turbine 201 of the exhaust gas turbocharger 200 and, in the exemplary embodiment, in an exhaust line III via catalytic converters, in particular via a pre-catalytic converter 203 and a main catalytic converter 204. The energy obtained in the area of ​​the turbine 201 of the exhaust gas turbocharger 200 is used to compress combustion air / fresh air FF in a compressor 202, which is then supplied to the cylinders Z of the gasoline engine 1 as compressed combustion air FL or charge air in a charge air line II.

[0016] In the illustrated embodiment, the simplest form of boost pressure control is shown by means of a turbine-side bypass with boost control pressure flap 201-1.

[0017] The exemplary embodiment is a gasoline engine 1 with externally ignited internal mixture formation. This means that the fuel / air mixture is formed by direct injection of liquid fuel or injection of gaseous fuel via injection / injection valves (not shown) into the main combustion chamber BK and ignited by an ignition device (not shown). However, the described method can also be used analogously for external mixture formation. This means that the illustration and the following description are based on one of several embodiments of mixture formation.

[0018] In the exemplary embodiment, an exhaust gas recirculation line IV is formed upstream of the turbine 201, which comprises an exhaust gas recirculation cooler 205 and an exhaust gas recirculation flap 206 in the usual way, wherein the exhaust gas FA is integrated into the fresh air line I downstream of an air filter 101 of the fresh air line I upstream of the compressor 202.

[0019] The inventive Otto engine 1 has two partial charge air lines II-1 and II-2, via which charge air FL-1 and FL-2 is supplied to the main combustion chambers BK and the pre-chambers, see Figure 1 which are formed downstream of the compressor 202 starting from the common charge air line II, which will be discussed below.

[0020] The first partial charge air line II-1 supplies compressed charge air FL-1 from the compressor 202 to the main combustion chambers BK of the respective cylinders Z, starting from the common charge air line II.

[0021] The second partial charge air line II-2 supplies compressed charge air FL -2 from the compressor 202 to the pre-chambers of the respective cylinders Z, starting from the common charge air line II.

[0022] In other words, the charge air line II has a sampling point II-E (upstream of the throttle valve 102) at which compressed charge air FL with the boost pressure present in front of the throttle valve 102 is extracted as scavenging air for the pre-chambers of the respective cylinders Z, which is why the second partial charge air line II-2 forms the scavenging line for the pre-chambers and the partial charge air line II-1 for the main combustion chambers BK.

[0023] A check valve 301, preferably a buffer tank 302 and an additional compressor 303 are assigned to the purge line behind the extraction point II-E, and after corresponding division of the purge line into individual purge air lines, timing valves 304 are assigned to each cylinder Z, via which a predeterminable quantity of purge air is guided via the purge line to the prechambers of the respective cylinder Z at predeterminable times.

[0024] Furthermore, according to the invention, it is provided that not only purge air, but alternatively an air-fuel vapor mixture is provided for purging the pre-chambers of the respective cylinders Z, so that the second partial charge air line II-2, which is also referred to as purge line, has a fuel supply line V fuel K at a supply point II-2Z to the purge line, which is arranged downstream of the additional compressor 303 before the purge line is divided into the individual purge air lines in front of the timing valves 304.

[0025] If an air-fuel vapor mixture FL -2 / K is present, a predeterminable quantity of air-fuel vapor mixture FL -2 / K can be fed as a purge medium via the purge line to the prechambers of the respective cylinder Z at predeterminable times.

[0026] According to the invention, for flushing the active pre-chambers with charge air FL -2 or with the charge air-fuel mixture FL -2 / K, a pressure level above the charge air pressure of the charge air FL -1 is required for the flushing medium to be injected.

[0027] It is therefore proposed that the additional compressor 303 arranged according to the invention increases the pressure level of the charge air FL in the purge line to a predeterminable purge air pressure, which is preferably up to twice the pressure of the charge air FL.

[0028] In other words, the purge pressure generated by the auxiliary compressor 303 is always higher than the pressure present in the prechamber. A demand-dependent pressure is generated by the auxiliary compressor 303, the pressure level of which is higher than the prechamber pressure, so that reliable purge of the prechambers 13 toward the main combustion chamber BK is always ensured when the respective timing valve 304 is opened. The pressure downstream of the auxiliary compressor 303 is thus always greater than the pressure of the compressor 202 of the exhaust gas turbocharger 200. The compressors 202 and 303 are configured accordingly and operated as described above.

[0029] Advantageously, by extracting the charge air FL from the charge air line II, the outlet pressure for the auxiliary compressor 303 during supercharged operation is above the ambient pressure, thus saving compression work for the auxiliary compressor 303. In other words, the auxiliary compressor 303 provides its compression power in the form of a pressure increase, which, based on the applied charge air pressure of the charge air FL at the extraction point II-E, depends on the required or predeterminable purge air pressure at the timing valves 304.

[0030] Preferably, the charge air FL is extracted downstream of a charge air cooler LK1. In the present exemplary embodiment, a first charge air cooler LK1 is arranged in the common charge air line II, and a further charge air cooler LK2 is arranged downstream of the throttle valve 102 in the partial charge air line II-1 leading to the main combustion chambers BK.

[0031] Advantageously, by taking the charge air FL downstream of an intercooler LK1, a slightly lower output pressure will be present at the extraction point II-E than upstream of the intercooler LK1, however, the cooler purge air not only contains more oxygen, but the cooler purge air also has a smaller volume, which on the one hand advantageously means that less compression work has to be performed in the additional compressor 303, and on the other hand advantageously the charge air or the charge air-fuel mixture FL -2 / K for purging the prechambers is more ignitable despite the downstream additional compression by means of the additional compressor 303 due to the more oxygen available at the extraction point II-E.

[0032] In an alternative embodiment, exhaust gas can be supplied to the fresh air FF in the fresh air line I via the exhaust gas recirculation flap 206, so that exhaust gas can be supplied to the fresh air FF.

[0033] In this case, a fresh air / exhaust gas mixture FF / FA in a predeterminable mixing ratio is fed via the charge air line II, which is fed to the main combustion chambers BK and to the pre-chambers and, as previously explained, is compressed via the compressor 202 and recompressed in the scavenging line to the pre-chambers, wherein a predeterminable amount of fuel K can be fed to the fresh air / exhaust gas mixture FF / FA via the fuel feed line V at the feed point II-2Z, so that finally a fuel / air / exhaust gas mixture K / FF / FA recompressed by means of the additional compressor 303 can also be fed into the pre-chambers. List of reference symbols

[0034] 1 Internal combustion engine / gasoline engine 101 Air filter 102 Throttle valve ZZ Cylinder BK Main combustion chamber 200 Exhaust gas turbocharger 201 Turbine 202 Compressor 201-1 Charge control pressure flap 203 Pre-catalytic converter 204 Main catalyst 205 Exhaust gas recirculation cooler 206 Exhaust gas recirculation flap 301 Check valve 302 Buffer tank 303 Additional compressor 304 Timing valves LK1 Intercooler LK2 Intercooler I Fresh air line II Charge air line II-E Extraction point II-1 First partial charge air line II-2 Second partial charge air line (purge line) II-2 Z Supply point III Exhaust line IV Exhaust gas recirculation line V Fuel supply line FF Fresh air / combustion air FL Charge air before extraction point II-E FL -1 Charge air in II-1 FL -2Charge air in II-2 FL -2 / KCharge air-fuel mixture FA Exhaust gas FF / FA Fresh air / exhaust gas mixture KFuel K / FF Fuel-fresh air mixture K / FF / FA Fuel / air / exhaust gas mixture

Claims

1. Internal combustion engine (1), comprising at least one cylinder (Z), wherein the at least one cylinder (Z) has a main combustion chamber (BK) for the combustion of a fuel / air mixture (K / FL) or a fuel / air / exhaust gas mixture (K / FF / FA), and a flushed prechamber, which is connected in terms of fluid to the main combustion chamber (BK) via at least one overflow channel, and at least one exhaust turbocharger (200), which has a turbine (201) for expanding exhaust gas (FA) leaving the at least one cylinder (Z), and a compressor (202) for compressing fresh air (FF) or a fresh air / exhaust gas mixture (FF / FA) being supplied to the at least one cylinder (Z) as compressed charge air (FL), wherein in a charge-air tract (II) downstream of the compressor (202) an extraction point (II-E) is formed, from which branch off a second partial charge-air tract (II-2), as a flushing tract, and a first partial charge-air tract (II-1), wherein a charge-air partial quantity (FL-2) of the compressed charge air (FL) for flushing the at least one prechamber can be extracted via the flushing tract, wherein an auxiliary compressor (303) is arranged in the flushing tract which increases the charging pressure of the compressed charge air (FL) as required, wherein the fresh air / exhaust gas mixture (FF / FA) can be supplied to the compressor (202) from a fresh-air tract (I) arranged upstream of the compressor (202), since the fresh-air tract (I) is connected upstream of the compressor (202) to an exhaust gas return tract (IV) of an exhaust tract (III) such that exhaust gas (FA) can be supplied to the fresh air (FF) in the fresh-air tract (I) so that via the extraction point (II-E) a fresh-air / exhaust gas mixture (FF / FA) can also be extracted as compressed charge air (FL) and can be recompressed in the flushing tract by means of the auxiliary compressor (303) as required, wherein a supply point (II-2Z) of a fuel feed line (V) for supplying fuel (K) to the charge air (FL), which is recompressed as required by means of the auxiliary compressor (303), is formed in the flushing tract downstream of the auxiliary compressor (303), said charge air being present in the flushing tract as fresh air (FF) or as a fresh air / exhaust gas mixture (FF / FA).

2. Internal combustion engine (1) according to Claim 1, wherein in the charge-air tract (II) downstream of the compressor (202) a first charge-air cooler (LK1) is arranged upstream of the extraction point (II-E).

3. Internal combustion engine (1) according to Claim 2, wherein the extraction point (II-E) is arranged between the first charge-air cooler (LK1) and a throttle valve (102) of a suction pipe leading to the at least one main combustion chamber (BK).

4. Internal combustion engine (1) according to Claim 1, wherein upstream of the auxiliary compressor (303) in the flushing tract there is / are arranged a check valve (301) or a check valve (301) and a buffer container (302).

5. Internal combustion engine (1) according to Claim 4, wherein fresh air (FF) can be supplied to the compressor (202) from a fresh-air tract (I) arranged upstream so that fresh air (FF) can be extracted as compressed charge air (FL) via the extraction point (II-E) and recompressed as required in the flushing tract by means of the auxiliary compressor (303).

6. Method for operating an internal combustion engine (1) which comprises at least one cylinder (Z), wherein the at least one cylinder (Z) has a main combustion chamber (BK) for the combustion of a fuel / air mixture (K / FL) or a fuel / air / exhaust gas mixture (K / FF / FA), and a flushed prechamber, which is connected in terms of fluid to the main combustion chamber (BK) via at least one overflow channel, and which comprises at least one exhaust turbocharger (200), which has a turbine (201) for expanding exhaust gas (FA) leaving the at least one cylinder (Z), and a compressor (202) for compressing fresh air (FF) or a fresh air / exhaust gas mixture (FF / FA) being supplied to the at least one cylinder (Z) as compressed charge air (FL), wherein in a charge-air tract (II) downstream of the compressor (202) an extraction point (II-E) is formed, from which branch off a second partial charge-air tract (II-2), as a flushing tract, and a first partial charge-air tract (II-1), wherein a charge-air partial quantity (FL-2) of the charge air (FL) compressed in the compressor (202) of the exhaust turbocharger (200) for flushing the at least one prechamber is extracted via the flushing tract, wherein in the flushing tract downstream of an auxiliary compressor (303) there is formed a supply point (II-2Z) of a fuel feed line (V) for supplying fuel (K) to the charge air (FL), which is recompressed as required by means of the auxiliary compressor (303), which increases the charge pressure of the compressed charge air (FL) as required so that the at least one prechamber is flushed with the recompressed fresh air (FF) or the recompressed fresh air / exhaust mixture (FF / FA) since a fresh-air tract (I) is connected upstream of the compressor (202) to an exhaust return tract (IV) of an exhaust tract (III) such that exhaust gas (FA) can be supplied to the fresh air (FF) in the fresh-air tract (I), wherein fuel (K) can be supplied as required to the compressed charge air (FL) or to the fresh-air / exhaust gas mixture (FF / FA) downstream of the auxiliary compressor (303) so that the at least one prechamber can also be flushed with a recompressed fuel / fresh-air mixture (K / FF) or a recompressed fuel / air / exhaust mixture (K / FF / FA).