Various methods and systems are provided for using only hydrogen as fuel in a duel fuel engine. In one example, a method may include direct injecting only hydrogen as fuel to one or more engine cylinders and compression igniting the injected hydrogen.

Various methods and systems are provided for skipping fire in one or more cylinders in a dual fuel engine. In one example, a method may include injecting a combination of two fuels to a first set of cylinders of the engine while disabling fuel injection to all remaining cylinders of the engine.

An action of injection of the main injection fuel (QM) from the fuel injector (3) is started within a range of crank angle from 10 degree before the compression top dead center to 10 degree after the compression top dead center. A smaller amount of the auxiliary injection fuel (QN) than the main injection fuel (QM) is made to be injected from the fuel injector (3) before the main injection fuel (QM) so as to make the auxiliary injection fuel (QN) ignite by the premixed charge compression ignition. The injection timing of the auxiliary injection fuel (QN) is controlled to a timing whereby a heat generated by the premixed charge compression ignition of the auxiliary injection fuel (QN) causes the premixed charge compression ignition of the main injection fuel (QM) after the start of injection of the main injection fuel (QM).

Main fuel injected from the fuel injector into the combustion chamber is made to auto-ignite. During the compression stroke after injection of the main fuel and before the auto-ignition of the main fuel, first auxiliary fuel and second auxiliary fuel are successively injected from the fuel injector. By controlling the injection timing of the first auxiliary fuel, the ignition timing of the spark plug, and the injection timing of the second auxiliary fuel, the first auxiliary fuel is made to burn by flame propagation combustion by the ignition action of the spark plug, the second auxiliary fuel is made to be injected inside the flame propagation combustion region, and the second auxiliary fuel is made to burn by diffusive combustion before auto-ignition of the main fuel occurs.

A control system for an internal combustion engine is provided with a combustion control part, an operating state judging part judging if an engine operating state is a steady state or a combustion noise is a noise transition state where the combustion noise increases over a predetermined allowable noise value when burning fuel by an ignition-assist self-ignition combustion, and an ozone supply control part controlling the amount of ozone supplied to the combustion chamber by the ozone supply system. The ozone supply control part controls the amount of supply of ozone to a predetermined reference amount when the state is judged to be the steady state and controls the amount of supply of ozone to an amount of supply smaller than the reference amount or makes the amount of supply of ozone zero when the state is judged to be the noise transition state.

An object is to enable stable diesel combustion in an internal combustion engine using a fuel having a relatively high self-ignition temperature. In the internal combustion engine, pre-injection and ignition of pre-spray fuel are performed, and thereafter main injection is performed to cause a portion of main-injected fuel to be burned by diffusion combustion. Injection ports of a fuel injection valve are provided in such a way that the quantity of the main injected fuel injected to a predetermined region defined by a predetermined angle equal to or smaller than 90 degrees about the fuel injection valve from the location of an ignition device in the direction of rotation of the swirl is relatively small.

An engine control method includes: a first fuel supply step of supplying fuel into the combustion chamber using an injector when a spark plug makes flame in the combustion chamber so that an air-fuel mixture is generated at least around the spark plug, the air-fuel mixture having an air-fuel mass ratio A/F or a gas-fuel mass ratio G/F, in which gas includes air, higher than a stoichiometric air-fuel ratio; after the first fuel supply step, an ignition step of making the flame in the combustion chamber in the compression stroke using the spark plug; and after the ignition step, a second fuel supply step of supplying the fuel into the combustion chamber in the compression stroke using the injector to increase a fuel concentration of the air-fuel mixture in the combustion chamber.

An engine device including an intake manifold configured to supply air into a cylinder; an exhaust manifold configured to output exhaust gas from the cylinder; a gas injector which mixes a gaseous fuel with the air supplied from the intake manifold; and a main fuel injection valve configured to inject a liquid fuel into the cylinder for combustion. At the time of switching from a gas mode in which the gaseous fuel is supplied into the cylinder to a diesel mode in which the liquid fuel is supplied into the cylinder, a supply-start timing of the liquid fuel is delayed relative to a supply-stop timing of the gaseous fuel.

A fuel system for an engine has a cylinder with an inlet air port, an air box surrounding the inlet air port, and a gaseous fuel injector positioned in the air box and having a nozzle located at the inlet air port. The fuel system also has a gaseous fuel control valve, a fuel supply line fluidly extending from the gaseous fuel control valve to the gaseous fuel injector, a purge valve, and a purge fluid supply line fluidly extending from the purge valve to at least one of the fuel supply line and the gaseous fuel injector. The fuel system also has a return valve and a return line fluidly extending from at least one of the fuel supply line and the gaseous fuel injector.

A method for operating a compression ignition engine includes forming a combustible mixture by mixing generally homogeneously a first fuel and air and introducing this mixture into the at least one cylinder, compressing the combustible mixture with the piston in a compression stroke, injecting a second fuel to the combustible mixture at an injection-time of the second fuel during the compression stroke but before start of combustion, and continuing the compression stroke until combustion starts at those locations in the at least one cylinder where concentration of the second fuel is highest and/or the temperature of the mixture is the highest. Emission of the cylinder and/or mechanical stress of the cylinder caused by the combustion are monitored, and if emissions and/or mechanical stress are above respective predetermined thresholds, individually for the cylinder, the amount and/or the timing of the second fuel injected, and/or temperature of the cylinder charge is changed.