Internal Combustion Engine Having a Splitted Fuel Admission and a Respective Combustion Process

Abstract

The invention provides a combustion engine comprising at least one combustion chamber, preferably several combustion chambers (1), wherein to each combustion chamber a piston (2) moving within a cylinder (3), a cylinder head (4) comprising at least one admission valve (5), at least one outlet valve (6), at least one spark plug (7) an intake port (13) and a throttle (8) controlling the engine load, is assigned. The combustion chamber (1) comprises a secondary injector means (14) for injecting a secondary fuel directly into the combustion chamber (1) in the direction of the spark plug (7) and secondary fuel supply means (15) for supplying a gas as a secondary fuel to said secondary injector means (14). Supply means (16) for compressed air and mixture means for providing a mixture of air and gas fuel to said secondary injector means (14), facilitating the stoichiometric air-to-fuel ratio to be held at =1.

Claims

1. Combustion engine comprising at least one combustion chamber, wherein to each combustion chamber a piston moving within a cylinder, a cylinder head comprising at least one admission valve, at least one outlet valve, at least one spark plug, an intake port with a primary fuel injector or a carburettor and a throttle controlling the engine toad, is assigned, wherein said combustion chamber comprises a secondary injector means for injecting a secondary fuel directly into the combustion chamber and secondary fuel supply means for supplying a gas as a secondary fuel to said secondary injector means, characterized in that said secondary injector means for injecting a secondary fuel directly into the combustion chamber are arranged so that said secondary fuel is injected in the direction of said spark plug; said combustion engine further comprises supply means or pressure air and mixture means for providing a mixture of air and gas fuel to said secondary injector means said at least one of control means for controlling the penetration length of the mixture injected by said secondary injector means, by controlling the injection pressure of the mixture injected by said secondary injector means adjusting means for adjusting the penetration length of the mixture injected by said secondary injector means, by adjusting the injection pressure of the mixture injected by said secondary injector means.

2. Combustion engine according to claim 1, characterized by control means for controlling the mixture ratio of air and gas fuel of said mixture means.

3. Combustion engine according to claim 1, characterized by adjusting means for adjusting the mixture ratio of air and gas fuel of said mixture means.

4. Combustion engine according to claim 1, characterized by control means for controlling the amount of the mixture injected by said secondary injector means, by controlling the end of injection.

5. Combustion engine according to claim 1, characterized by adjusting means for adjusting the amount of the mixture injected by said secondary injector means, by adjusting the end of injection.

6. Combustion engine according to claim 1, characterized by an exhaust gas recirculation connection means comprising an external gas recirculation control valve and control means for controlling said external gas recirculation control valve.

7. A method for operating a combustion engine according to claim 1, characterized in that pressure air is supplied and mixed with said secondary gas and provided to said secondary injector means and injected.

8. The method according to claim 7, characterized in that the mixture is injected prior to ignition or, in case of consecutive ignitions, prior to first ignition.

9. The method according to claim 7, characterized in that the mixture ratio of air and gas fuel of said mixture means is controlled by control means.

10. The method according to claim 7, characterized in that the amount of the mixture of air and gas fuel injected by said secondary injector means is controlled by control means.

11. The method according to claim 7, characterized in that the penetration length of the mixture injected by said secondary injector means is controlled by control means.

12. The method according to claim 7, characterized by at least two injection intervals for each cylinder cycle spaced by a time wherein no injection is provided.

13. The method according to claim 7, characterized in that the combustion engine for one or more cylinders is operated by injection of the secondary injector means only.

14. A method according to claim 9, characterized in that the port comprises a primary fuel injector and the same gaseous fuel is used in the primary fuel injector and the secondary fuel injector.

15. A method according to claim 10, characterized in that the port comprises a primary fuel injector and the same gaseous fuel is used in the primary fuel injector and the secondary fuel injector.

16. A method according to claim 11, characterized in that the port comprises a primary fuel injector and the same gaseous fuel is used in the primary fuel injector and the secondary fuel injector.

17. A method according to claim 12, characterized in that the port comprises a primary fuel injector and the same gaseous fuel is used in the primary fuel injector and the secondary fuel injector.

18. A method according to claim 13, characterized in that the port comprises a primary fuel injector and the same gaseous fuel is used in the primary fuel injector and the secondary fuel injector.

19. Combustion engine according to claim 2, characterized by control means for controlling the amount of the mixture injected by said secondary injector means, preferably by controlling the end of injection.

20. Combustion engine according to claim 3, characterized by control means for controlling the amount of the mixture injected by said secondary injector means, preferably by controlling the end of injection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Examples of the engine will henceforth be described in more detail by reference to the drawings, wherein are shown:

[0015] FIG. 1 is a diagram of pertinent elements of a cylinder of a combustion engine according to a preferred embodiment of the invention;

[0016] FIG. 2 a possible control scheme for the use of the combustion engine according to FIG. 1;

[0017] FIG. 3 a timing diagram of the fueling situation in a normal mode of the combustion engine according to FIG. 1;

[0018] FIG. 4 a timing diagram of the fueling situation in a not regular (emergency) mode of the combustion engine according to FIG. 1; and

[0019] FIG. 5 a timing diagram of the fueling situation in exhaust gas increasing mode of the combustion engine according to FIG. 1.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0020] FIG. 1 shows a part of a combustion engine comprising the conventional elements like a combustion chamber (1), a piston (2) moving within a cylinder (3), a cylinder head (4) comprising an admission valve (5), an outlet valve (6) and a port (13). The combustion engine according to this embodiment of the invention is provided with at least one spark plug (7) for ignition.

[0021] Fuel (12) for this internal combustion engine is mixed in the intake port (13) using a gas injector (11). According to the embodiment of FIG. 1, the amount of already burned gases inside the combustion chamber (1) is controlled using external EGR (9) with an EGR control valve (10) or by setting the timing of the intake (5) and exhaust (6) gas exchange valves accordingly. The engine load is controlled using a throttle (8) in combination with the amount of EGR and optionally by controlling a boosting device like a turbocharger, supercharger or similar.

[0022] It should be noted that fuel (12) means several liquid or gaseous fuel types. Typical liquid fuels are gasoline, methanol or ethanol. Typical gaseous fuels are natural gas, biogas, landfill gas, synthetic gas which are gases consisting mainly of methane, hydrogen, propane, butane, carbon monoxide with possible inert parts like nitrogen, carbon dioxide or air.

[0023] In operating conditions where the inflammability of the mixtures is poor, a secondary fuel injector (14) which is able to inject directly into the combustion chamber (2) injects a small amount of a mixture of additional gas (15) and air (16) prior to ignition or, if consecutive ignition is applied, prior first ignition in such a way that a good inflammable air/fuel mixture (regarding stoichiometry and flow field/micro turbulences) is established around the spark plug (7).

[0024] The overall air-to-fuel ratio in the combustion chamber remains at a desired level (=1 or lean). Good inflammability can be controlled by setting the air to fuel ratio of the secondary fuel injector, the amount of the mixture as well as the penetration length of the directly injected mixture. The effect of the increased inflammability is not just achieved by the control of the stoichiometry of the mixture around the spark plug but also by influencing the flow field in such a way, that a fast and stable flame kernel development is given.

[0025] It should be noted that secondary fuel injector which is the direct injector can be fed by a mixture of fuel gas and air which may be pressurized orif not pressurizedthe pressure increase of the air has to be performed within the injector. Alternatively, the secondary fuel injector may use a mixture of fuel and air mixed before.

[0026] The control of the engine system is laid out to achieve desired targets which are mainly lowest fuel consumption, lowest pollutant emissions and good driveability. This is done using feedforward and feedback control strategies on the respective actuating variables while the distribution between port fuel and direct injection (quantity, quality, timing, pressure) are new actuating variables. The optimum control structures are typically found by numerical modelling of the engine system and the best parameters are typically found with help of experiments on an engine test bench. A possible control scheme is shown in FIG. 2. This scheme allows the control of using the port fueland the direct injection path by setting the injection timings, the pressures and the air/fuel ratio of the direct injection accordingly.

[0027] In normal mode, port fuel injection is typically performed during the intake stroke and direct injection is performed during the compression stroke prior ignition. The exact phasing of the direct injection event depends on the layout of the engine and the operating point and it is typically found using numerical simulation and/or experiments. The typical timing diagram according to the normal mode is shown in FIG. 3.

[0028] If the port fuel injector fails, the direct injection mode can be prolonged so that the engine can still be operated in an emergency mode. The typical timing diagram according such an emergency mode is shown in FIG. 4.

[0029] If the exhaust gas temperature has to be increased (e.g. for thermal management reasons of the exhaust gas treatment devices), an additional direct injection event can be placed during the expansion stroke (prior opening of the exhaust valve). The typical timing diagram according such a temperature increasing mode is shown in FIG. 5.

LIST OF REFERENCE SIGNS

[0030] 1 combustion chamber [0031] 2 piston [0032] 3 cylinder [0033] 4 cylinder head [0034] 5 admission valve [0035] 6 valve [0036] 7 spark plug [0037] 8 throttle [0038] 9 exhaust gas recirculation [0039] 10 exhaust gas recirculation control valve [0040] 11 primary fuel injector [0041] 12 primary fuel supply [0042] 13 port [0043] 14 secondary fuel injector [0044] 15 secondary fuel supply [0045] 16 air supply