METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE

Abstract

The present disclosure relates to a method for operating a combustion engine. A main amount of gas fuel is fed via a pre-chamber into a main combustion chamber. An ignition quantity of gas fuel is fed into the pre-chamber before the piston reaches the upper dead center to form an air-gas fuel mixture in the pre-chamber, which is fatter than in the main combustion chamber. The air-gas fuel mixture in the pre-chamber ignites itself. The air-gas fuel mixture in the main combustion chamber ignites through the self-ignited air-gas fuel mixture in the pre-chamber.

Claims

1-15. (canceled)

16. A method for operating an internal combustion engine, comprising: supplying a main quantity of gas fuel into a main combustion chamber of the internal combustion engine via a prechamber, wherein the main combustion chamber is in fluid communication with the prechamber; compressing and mixing air and the main quantity of gas fuel to form an air/gas fuel admixture during a movement of a piston in the main combustion chamber to a top dead center of a piston movement of the piston; supplying an ignition quantity of gas fuel into the prechamber, before the piston reaches the top dead center, in order to form in the prechamber an air/gas fuel admixture which is richer than in the main combustion chamber; self-igniting the air/gas fuel admixture in the prechamber; and igniting the air/gas fuel admixture in the main combustion chamber by the self-ignited air/gas fuel admixture in the prechamber.

17. The method according to claim 16, wherein the internal combustion engine is a single-fuel internal combustion engine.

18. The method according to claim 16, wherein: the main quantity of gas fuel is selected from the group consisting of methane and natural gas; or the ignition quantity of gas fuel is selected from the group consisting of methane and natural gas.

19. The method according to claim 16, wherein the air and the main quantity of gas fuel are mixed during the compression to form a homogeneous air/fuel admixture in the main combustion chamber.

20. The method according to claim 19, wherein the homogeneous air/gas fuel admixture has a combustion air ratio (λ) that is greater than or equal to 2 or less than or equal to 3 so that a self-ignition of the air/gas fuel admixture in the main combustion chamber is inhibited; or the homogeneous air/gas fuel admixture has a combustion air ratio (λ) which does not lead to self-ignition of the air/gas fuel admixture in the main combustion chamber.

21. The method according to claim 16, further comprising: compressing a portion of the air/gas fuel admixture from the main combustion chamber into the prechamber during the movement of the piston to the top dead center; or compressing a portion of the air/gas admixture from the main combustion chamber into the prechamber during the movement of the piston to the top dead center after the main quantity of gas fuel has been supplied, wherein the ignition quantity is supplied into the portion of the air/gas fuel admixture which is compressed into the prechamber.

22. The method according to claim 16, wherein: the richer air/gas fuel admixture in the prechamber has a combustion air ratio (λ) between 0.8 and 1.5, so that a self-ignition of the richer air/gas fuel admixture in the prechamber is enabled; or the richer air/gas fuel admixture in the prechamber has a combustion air ratio (λ) which leads to a self-ignition of the richer air/gas fuel supply in the prechamber; or the richer air/gas fuel admixture in the prechamber has a combustion air ratio (λ) of 1, so that a self-ignition of the richer air/gas fuel admixture in the prechamber is enabled.

23. The method according to claim 16, wherein: the main quantity of gas fuel corresponds to between 90% and 98% of a gas fuel quantity supplied in total per combustion cycle; or the ignition quantity of gas fuel corresponds to between 2% and 10% of a gas fuel quantity supplied in total per combustion cycle; or the main quantity of gas fuel and the ignition quantity of gas fuel amount to 100% of a gas fuel quantity supplied in total per combustion chamber.

24. The method according to claim 16, wherein: an effective mean pressure is less than or equal to 10 bar so that a self-ignition of the air/gas fuel admixture in the main combustion chamber is inhibited; or an effective mean pressure is such that it does not lead to a self-ignition of the air/gas fuel admixture in the main combustion chamber; or an effective mean pressure is less than or equal to 9 bar so that a self-ignition of the air/gas fuel admixture in the main combustion chamber is inhibited; or an effective mean pressure is less than or equal to 8 bar so that a self-ignition of the air/gas fuel admixture in the main combustion chamber is inhibited.

25. The method according to claim 16, wherein: the ignition quantity of gas fuel is supplied to the prechamber when the piston is in the region of the top dead center of the piston movement; or the ignition quantity of gas fuel is supplied to the prechamber when the piston is in a range between 50 and 0 degrees crank angle before top dead center of the piston movement; or the ignition quantity of gas fuel is supplied to the prechamber when the piston is in a range between 30 and 15 degrees crank angle before top dead center of the piston movement.

26. The method according to claim 16, wherein the main quantity of fuel and the ignition quantity of fuel have the same gas fuel, wherein the gas fuel is methane or natural gas; or the main quantity of gas fuel is supplied during an inlet cycle up to a maximum of 100 degrees crank angle before the top dead center; or the main quantity of gas fuel is supplied during a compression cycle up to a maximum of 100 degrees crank angle before the top dead center.

27. The metho according to claim 16, further comprising supplying air into the main combustion chamber during an inlet cycle.

28. The method according to claim 16, wherein: the supply of the ignition quantity of fuel or the supply of the main quantity of fuel is carried out in a gaseous manner; or the supply of the main quantity of fuel is carried out temporarily before or spaced apart from the supply of the ignition quantity of fuel; or the supply of the ignition quantity of fuel and the supply of the main quantity of fuel are carried out by the same fuel injector; or the supply of the ignition quantity of fuel and the supply of the main quantity of fuel are carried by the same supply line of the same fuel injector; or the supply of the ignition quantity of fuel and the supply of the main quantity of fuel are carried out at the same supply pressure.

29. The method according to claim 16, wherein: the supply of the ignition quantity of fuel or the supply of the main quantity of fuel is carried out by means of a piezo fuel injector; or the supply of a pilot quantity of fuel or the supply of the main quantity of fuel is carried out by a fuel injector which is activated by means of an electromagnet; or

30. The method according to claim 16, wherein: an inner side face of the prechamber has a thermal insulator; or an inner side face of the prechamber has a thermal insulator in the form of a thermally insulating coating.

31. The method according to claim 16, wherein: self-ignition of the air/gas fuel admixture in the prechamber is carried out during normal operation of the internal combustion engine; and the method further comprises: remote ignition of the air/gas fuel admixture in the prechamber by means of a spark plug in the case of a cold start of the internal combustion engine; or preheating the prechamber by means of a glow plug and self-ignition of the air/gas fuel admixture in the preheated prechamber in the case of a cold start of the internal combustion engine.

32. The method according to claim 16, wherein: the prechamber has a volume in a range between 0.5 cm.sup.3 and 2 cm.sup.3; or the prechamber is connected to the main combustion chamber by means of a plurality of through-openings which are arranged in a distributed manner; or the prechamber is connected to the main combustion chamber by means of 6 to 14 through-openings which are arranged in a distributed manner; or the prechamber is integrated in a fuel injector for the ignition quantity of fuel or the main quantity of fuel; or the prechamber is constructed separately from a fuel injector for the ignition quantity of fuel or the main quantity of fuel; or the prechamber is arranged centrally with respect to the main combustion chamber.

33. An internal combustion engine, comprising: a main combustion chamber; a prechamber in fluid communication with the main combustion chamber; and a piston operably disposed within a portion of the main combustion chamber, wherein a main quantity of gas fuel is supplied to the main combustion chamber via the prechamber, wherein movement of the piston in the main combustion chamber to a top dead center of piston movement compresses and mixes air and the main quantity of fuel to form an air/gas fuel admixture, wherein the air/gas fuel admixture is self-ignited in the prechamber to effectuate a corresponding ignition of the air/gas fuel admixture in the main combustion chamber.

34. A motor vehicle, comprising: an internal combustion chamber, the internal combustion engine including: a main combustion chamber; a prechamber in fluid communication with the main combustion chamber; and a piston operably disposed within a portion of the main combustion chamber, wherein a main quantity of gas fuel is supplied to the main combustion chamber via the prechamber, wherein movement of the piston in the main combustion chamber to a top dead center of piston movement compresses and mixes air and the main quantity of fuel to form an air/gas fuel admixture, wherein the air/gas fuel admixture is self-ignited in the prechamber to effectuate a corresponding ignition of the air/gas fuel admixture in the main combustion chamber.

35. The motor vehicle according to claim 34, wherein the motor vehicle is a utility vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Various aspects and features of the present disclosure are described below with reference to the appended drawings, in which:

[0045] FIG. 1 is a schematic illustration of an internal combustion engine according to an embodiment of the present disclosure; and

[0046] FIG. 2 is a sectioned view through an exemplary cylinder head.

DETAILED DESCRIPTION

[0047] The embodiments shown in the Figures correspond at least partially so that components which are similar or identical are given the same reference numerals and for the explanation thereof reference may also be made to the description of the other embodiments or Figures in order to avoid repetition.

[0048] FIG. 1 shows an internal combustion engine 10. The internal combustion engine 10 is configured as a reciprocating internal combustion engine. In embodiments, the internal combustion engine 10 is configured as a four-cycle internal combustion engine. The internal combustion engine 10 has one or more cylinders. In order to improve clarity, only one cylinder is illustrated in FIG. 1. The internal combustion engine 10 is configured as a single-fuel internal combustion engine for operation using methane (natural gas) as a single fuel. However, the internal combustion engine 10 may, for example, also be operated with another gaseous fuel, for example, hydrogen.

[0049] The internal combustion engine 10 may be included in a vehicle, for example, a motor vehicle, a rail vehicle or a water-borne vehicle, for driving the vehicle. In embodiments, the internal combustion engine 10 is included in a utility vehicle, for example, a truck or a bus, for driving the utility vehicle. It is also possible to use the internal combustion engine 10 in a stationary facility, for example, for driving a generator.

[0050] The internal combustion engine 10 may have per cylinder at least one air inlet channel 12, at least one exhaust gas outlet channel 14, a main combustion chamber 16, a piston 18, a fuel injector 20, a (for example, single) prechamber (pre-combustion chamber) 22 and a cylinder head 24.

[0051] The air inlet channel 12 opens in the main combustion chamber 16. (Charging) air can be supplied to the main combustion chamber 16 via the air inlet channel 12. The air inlet channel 12 is arranged in the cylinder head 24. The cylinder head 24 delimits the main combustion chamber 16 from above. An air supply system may be arranged upstream of the air inlet channel 12. The air supply system may, depending on requirements, have, for example, one or more compressors of a turbocharger subassembly, a charge air cooler and/or an exhaust gas return line.

[0052] An aperture opening of the air inlet channel 12 into the main combustion chamber 16 is intended to be opened and closed by means of an air inlet valve 26. In one non-limiting embodiment, the air inlet valve 26 may be a disk valve. The air inlet valve 26 can be activated using any technology, for example, by means of an variable valve drive.

[0053] After the combustion, the exhaust gas leaves the main combustion chamber 16 through the exhaust gas outlet channel 14 which is opened by means of an exhaust gas outlet valve 28. The exhaust gas outlet valve 28 may, for example, be configured as a disk valve. The exhaust gas outlet channel 14 is arranged in the cylinder head 24. An exhaust gas system may be arranged downstream of the exhaust gas outlet channel 14. The exhaust gas system may, for example, have one or more exhaust gas turbines of a turbocharger subassembly and/or at least one exhaust gas aftertreatment apparatus. The exhaust gas outlet valve 28 can be activated using any technology, for example, by means of a variable valve drive.

[0054] The piston 18 is arranged so as to be able to be moved back and forth in the cylinder. The piston 18 is connected to a crankshaft 32 by means of a connection rod 30. The piston 18 delimits the main combustion chamber 16 in a downward direction. The piston 18 can compress air or an air/fuel admixture in the main combustion chamber 16 when it moves from the bottom dead center to the top dead center.

[0055] The fuel injector 20 is constructed as a gas fuel injector, and in embodiments a methane/natural gas injector. The fuel injector 20 is constructed as a single-fuel injector for guiding a single gas fuel. The fuel injector 20 is arranged or configured in such a manner that gas fuel is supplied to the prechamber 22. In embodiments, the fuel injector 20 blows the gas fuel in a gaseous state directly into the prechamber 22. The fuel injector 20 is arranged centrally with respect to the main combustion chamber 16.

[0056] The supply by the fuel injector 20 is carried out at a high pressure, for example, in a range between 200 bar and 600 bar. For example, the fuel injector 20 may be fluidically connected to a gas fuel common rail. The gas fuel common rail may supply gas fuel to the fuel injector 20.

[0057] The fuel injector 20 is constructed to supply an ignition quantity and a main quantity of gas fuel into the prechamber 22 at different times. The fuel injector 20 may be activated in any manner. In order to also enable a supply of extremely small quantities of gas fuel, the fuel injector 20 may be a piezo fuel injector which can be activated by means of a piezo element, for example, a closure needle of the fuel injector 20 can be raised or lowered in accordance with a state of a piezo element or piezo crystal of the fuel injector 20. For example, it is also possible for the fuel injector 20 to be able to be activated by means of an electromagnet. In embodiments, an activation of the fuel injector 20 may be controlled by means of an electronic control unit 34.

[0058] The prechamber 22 may be integrated in the fuel injector 20, as indicated in FIG. 1. However, it is also possible to construct the prechamber 22 separately from the fuel injector 20, as illustrated in FIG. 2. The fuel injector 20 can then open, for example, directly in the prechamber 22. When the prechamber 22 and the fuel injector 20 are constructed separately, for example, the prechamber 22 may be formed at least partially by the cylinder head 24, by a cap element 36 which is fitted to the combustion chamber side of the cylinder head 24 (see FIG. 2) and/or by means of an assembly sleeve 38 (see FIG. 2) for the fuel injector 20. When the cap element 36 is used, for example, it may be screwed from below into the assembly sleeve 38.

[0059] The prechamber 22 may, for example, have a spherical, dome-like or rounded inner volume. The gas fuel can be supplied by means of the fuel injector 20 into the inner volume. The inner volume may be in a range between 0.5 cm.sup.3 and 2.5 cm.sup.3.

[0060] The prechamber 22 is connected to the main combustion chamber 16 in fluid terms by means of a plurality of through-openings (overflow openings). The through-openings are arranged in a state distributed symmetrically about a periphery of the prechamber 22. For example, from six to fourteen through-openings are included.

[0061] It is possible for an inner side face of the prechamber 22 to have a thermal insulator 40. The thermal insulator 40 may be configured as a coating of the inner side face. For example, the thermal insulator 40 may comprise a ceramic material. It is possible, for example, for the thermal insulator 40 to be vapor deposited on the inner side face, applied to the inner side face by means of plasma application or injected onto the inner side face by means of an injection method. The thermal insulator 40 can prevent or at least reduce a cooling of gas fuel in the prechamber 22 by walls of the prechamber 22.

[0062] In an inlet cycle, (combustion) air is supplied through the air inlet channel 12 and the opened air inlet valve 26 into the main combustion chamber 16. The piston 18 moves from the top dead center to the bottom dead center.

[0063] In the inlet and/or compression cycle, a main quantity of gas fuel is supplied via the fuel injector 20 into the prechamber 22, and in embodiments, may be blown in. It is contemplated that the gas fuel is supplied no longer than up to 100° KW before TDC in the compression cycle.

[0064] The main quantity of gas fuel is blown into the prechamber 22 at a pressure which is higher than a pressure in the prechamber 22 and the main combustion chamber 16, for example, higher than a final compression pressure of the internal combustion engine 10. In embodiments, the main quantity of gas fuel corresponds to between approximately 90% and approximately 98% of a quantity of gas fuel which is supplied in total during a (single) combustion cycle (comprising inlet, compression, expansion and outlet cycle).

[0065] The main quantity of gas fuel flows during the inlet and/or compression cycle via the through-openings out of the prechamber 22 into the main combustion chamber 16. The main quantity of gas fuel is mixed with the supplied air in the main combustion chamber 16 to form an air/gas fuel admixture. During the compression cycle/a piston movement of the piston 18 from the bottom dead center to the top dead center, the air/gas fuel admixture is compressed to form a homogeneous admixture, for example, as a result of the gas movements in the main combustion chamber 16.

[0066] So that there is no undesirable self-ignition in the main combustion chamber, it is envisioned that the method should be used only at comparatively low effective mean pressures. In this instance, the homogeneous admixture may reach a compression air ratio (λ) between approximately 2 and approximately 3. From a thermodynamic viewpoint, the method can consequently be used up to an effective mean pressure of approximately 10 bar, in an embodiment approximately 9 bar, and in one non-limiting embodiments approximately 8 bar or less. Consequently, the method may, for example, be carried out without the combustion air ratio (λ) for the air/gas fuel admixture in the main combustion chamber 16 falling below values of approximately 2.

[0067] The air/gas fuel admixture is, after the supply of the main quantity of gas fuel into the prechamber 22 has ended, during the compression cycle compressed or pushed via the through-openings out of the main combustion chamber 16 into the prechamber 22.

[0068] At the end of the compression cycle, before the piston 18 reaches the top dead center, an ignition quantity of gas fuel is supplied into the prechamber 22, and in embodiments blown in and/or supplied under high pressure. It is envisioned that the supply may be carried out between 30° KW and 15° KW prior to the top dead center. The supply time for the ignition quantity may be comparatively low, for example, from only 50 μs to 200 μs.

[0069] It is contemplated that the ignition quantity of gas fuel may be supplied by means of the same fuel injector 20 as the main quantity. In embodiments, the ignition quantity of gas fuel corresponds to between approximately 2% and approximately 10% of a quantity of gas fuel supplied in total during a (single) combustion cycle. The main quantity and the ignition quantity amount to 100%. For example, between 0.5 mg and 3 mg of gas fuel may be supplied as an ignition quantity.

[0070] In the prechamber 22, as a result of the supply of the ignition quantity into the air/gas fuel admixture there is formed in the prechamber 22 an air/gas fuel admixture which is richer and more ignition-friendly than the air/gas fuel admixture in the main combustion chamber 16. As can be appreciated, as a result of the supply of the ignition quantity in the prechamber, a combustion air ratio (λ) between 0.8 and 1.5, and in embodiments approximately 1, is achieved in the prechamber 22. At least during normal operation of the internal combustion engine 10, this richer air/gas fuel admixture self-ignites in the prechamber 22. A flame front which is produced in this instance expands out of the prechamber 22 through the through-openings into the main combustion chamber 16 and ignites the leaner, homogeneous air/gas fuel admixture at that location. The following homogeneous lean combustion in the main combustion chamber 16 enables a significant reduction of the nitrogen oxide emissions, in particular under partial load of the internal combustion engine 10.

[0071] It is possible that, under cold start conditions of the internal combustion engine, a supported self-ignition or remote ignition of the gas fuel is brought about. The self-ignition of the ignition quantity may, for example be supported by means of a glow plug which protrudes into the prechamber 22. A remote ignition can also be brought about by means of a spark plug which protrudes into the prechamber 22. The glow plug or spark plug is preferably only used under cold start conditions of the internal combustion engine 10.

[0072] The invention is not limited to the preferred embodiments described above. Instead, a large number of variants and modifications which also make use of the notion according to the invention and which are therefore included within the protective scope are possible. In particular, the present disclosure also claims protection for the subject-matter and the features of the dependent claims regardless of the claims which are referred to. In particular, the individual features of the independent claim 1 are disclosed independently of each other in each case. In addition, the features of the dependent claims are also disclosed independently of all the features of the independent claim 1. All range indications therein are intended to be understood to be disclosed in such a manner that so to speak all the values falling within the respective range are disclosed individually, for example, also as more narrow outer limits of the respective range.

LIST OF REFERENCE NUMERALS

[0073] 10 Internal combustion engine [0074] 12 Air inlet channel [0075] 14 Exhaust gas outlet channel [0076] 16 Main combustion chamber [0077] 18 Piston [0078] 20 Fuel injector [0079] 22 Prechamber (pre-combustion chamber) [0080] 24 Cylinder head [0081] 26 Air inlet valve [0082] 28 Exhaust gas outlet valve [0083] 30 Connection rod [0084] 32 Crankshaft [0085] 34 Control unit [0086] 36 Cap element [0087] 38 Assembly sleeve [0088] 40 Thermal insulator