DUAL-FUEL COMBUSTION ENGINE

Abstract

A dual-fuel internal combustion engine with at least one combustion chamber, wherein the at least one combustion chamber is assigned to an intake valve for a gas-air mixture and an injector (I1 to I4) for liquid fuel, and a control device, which is designed in a switch-over mode to perform a switch-over, that an amount of energy supplied to the at least one combustion chamber through the gas-air mixture is changed, and a supplied amount of liquid fuel and/or a time of the injection of the liquid fuel is changed, and a combustion sensor whose signals are characteristic for the combustion process occurring in the at least one combustion chamber, wherein the control device is designed to carry out the switch-over using a stored relationship between a time progression of the signals of the combustion sensor and an introduced amount of gas-air mixture.

Claims

1. A dual-fuel internal combustion engine with at least one combustion chamber, wherein the at least one combustion chamber is assigned to an intake valve for a gas-air mixture and an injector (I1 to 14) for liquid fuel, and a control device, which is designed in a switch-over mode to perform a switch-over, wherein an amount of energy supplied to the at least one combustion chamber through the gas-air mixture is changed, and a supplied amount of liquid fuel and/or a time of the injection of the liquid fuel is changed, and a combustion sensor whose signals are characteristic for the combustion process occurring in the at least one combustion chamber, characterized in that the control device is designed to perform the switch-over using a stored relationship between a time progression of the signals of the combustion sensor and an introduced amount of gas-air mixture

2. A dual-fuel internal combustion engine according to claim 1, wherein the combustion sensor is a knock sensor.

3. A dual-fuel internal combustion engine according to claim 1, wherein the combustion sensor is a cylinder pressure sensor.

4. A dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the control device is designed to detect a signal of the combustion sensor in a first crank angle range and to deduce from it the amount of gas-air mixture introduced.

5. A dual-fuel internal combustion engine according to the preceding claim, wherein the control device is designed to detect a signal of the combustion sensor in a second, later crank angle range and thus to detect knocking.

6. A dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the control device is designed to close a distance to a knock limit from the chronological progression of the signals of the combustion sensor in the first crank angle range.

7. A dual-fuel internal combustion engine according to at least one of the preceding claims, wherein a plurality of piston cylinder units with combustion chambers are provided, and the control device is designed to check a supplied amount of liquid fuel and the combustion process in a cylinder-specific manner.

8. A method for switch-over of a dual-fuel internal combustion engine, in which switch-over an amount of energy supplied to an at least one combustion chamber through a gas-air mixture is changed, and a supplied amount of liquid fuel and/or a time of an injection of the liquid fuel is changed, characterized in that the switch-over is performed using a stored relationship between a time progression of the signals of a combustion sensor and an introduced amount of gas-air mixture

Description

[0028] The invention is discussed with reference to the figures.

[0029] FIG. 1 shows schematically an internal combustion engine according to the invention. In this example, it has four combustion chambers B1 to B4, which can be supplied with liquid fuel, in this case diesel, via the injectors I1 to I4. The intake valves for the gas-air mixture are not shown.

[0030] To create the gas-air mixture, a central gas mixer GM is provided, which is connected to an air supply L and a gas reservoir G, e.g. a tank. Via a gas-air mixture supply R, the gas-air mixture produced in the central gas mixer GM is supplied to the combustion chambers B1 to B4. Downstream of the gas mixer GM, a compressor V of a turbocharger (mixed-charged internal combustion engine) is also provided. However, the gas mixer GM could also be arranged downstream of the compressor V in the air supply (air-charged internal combustion engine). The number of combustion chambers B1 to B4 is purely exemplary.

[0031] The invention can be used in dual-fuel internal combustion engines with 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 or 24 combustion chambers.

[0032] FIG. 2a shows the time progression of a combustion sensor (here in the form of a cylinder pressure sensor for the cylinder pressure P in the combustion chamber of a selected piston cylinder unit) over the entire crank angle range (CA=crank angle).

[0033] We can recognize the formation of a first maximum at a specific crank angle with a specific strength, which is attributable to the introduction of liquid fuel. The first time window should be positioned so that this maximum can be detected.

[0034] FIG. 2b shows the progression as in FIG. 2a but with a later and stronger first maximum (for comparison, dashed reference lines are drawn at the crank angle and cylinder pressure corresponding to the position and strength of the first maximum of FIG. 2a), suggesting a longer ignition delay and thus a larger amount of gas in the gas-air mixture.

[0035] FIG. 2c shows the time progression of a combustion sensor in the form of a knock sensor. (An amplitude for the solid-borne sound over the entire range of crank angle is shown.) Recognizable here is also the formation of a first maximum, which is attributable to the introduction of liquid fuel. The first time window should be positioned so that this maximum can be detected.

[0036] FIG. 2d shows the progression as in FIG. 2c but with a later and stronger first maximum (for comparison, dashed reference lines are drawn at the crank angle and cylinder pressure corresponding to the position and strength of the first maximum of FIG. 2c), suggesting a longer ignition delay and thus a larger amount of gas in the gas-air mixture.