Various methods and systems are provided for controlling emissions and a likelihood of engine knock during combustion in a multi-fuel engine. A method for an engine includes mixing an amount of a first fuel and an amount of a second fuel to combust a fuel mixture having a fuel ratio of the first fuel relative to the second fuel, the first fuel having a faster combustion flame speed relative to the second fuel, the fuel mixture having an air-to-fuel ratio with an amount of air delivered to the engine. The method further includes controlling either or both of a speed of combustion and a stability of combustion of the fuel mixture with the amount of air delivered to the engine by changing at least one of the fuel ratio, the air-to-fuel ratio, or both of the fuel ratio and the air-to-fuel ratio.

Various methods and systems are provided for controlling emissions and a likelihood of engine knock during combustion in a multi-fuel engine. A method for an engine includes mixing an amount of a first fuel and an amount of a second fuel to combust a fuel mixture having a fuel ratio of the first fuel relative to the second fuel, the first fuel having a faster combustion flame speed relative to the second fuel, the fuel mixture having an air-to-fuel ratio with an amount of air delivered to the engine. The method further includes controlling either or both of a speed of combustion and a stability of combustion of the fuel mixture with the amount of air delivered to the engine by changing at least one of the fuel ratio, the air-to-fuel ratio, or both of the fuel ratio and the air-to-fuel ratio.

An engine operable in a premixed combustion system and a diffusion combustion system. The engine includes a main fuel injection valve, a pilot fuel injection valve, a liquid fuel tank, a main fuel supply path, a pilot fuel supply path, a pilot fuel filter, a pilot fuel high-pressure pump, a pilot fuel tank, and a pilot fuel supply pump. The pilot fuel tank stores pilot fuel sent from the pilot fuel high-pressure pump and not injected by the pilot fuel injection valve. This pilot fuel is sent to an automatic backwash filter and a pilot fuel filter while not passing through the liquid fuel tank.

An engine including a main fuel injection valve, a pilot fuel injection valve, a liquid fuel supply rail pipe, and a pilot fuel supply rail pipe. The main fuel injection valve supplies liquid fuel from the liquid fuel supply rail pipe to a combustion chamber during combustion in a diffusion combustion system. The pilot fuel injection valve supplies pilot fuel from the pilot fuel supply rail pipe to the combustion chamber in order to ignite gaseous fuel during combustion in a premixed combustion system. The liquid fuel supply rail pipe is disposed at one side of an imaginary vertical plane including an axis of a crank shaft. The pilot fuel supply rail pipe is disposed at the side of the imaginary vertical plane at which the liquid fuel supply rail pipe is disposed.

A method for carrying out the operation of an internal combustion engine, wherein liquid fuel injection amounts are injected at cylinders of a group of cylinders of the internal combustion engine in the context of injection events, wherein in a first step, a first cylinder of the group with the strongest knocking tendency over a time period is determined, and in a second step an injection correction occurs such that the injection events at the first determined cylinder can be sequentially reduced in their injection duration or injection amount by a first correction value, while the injection duration or injection amount of the injection events at the other cylinders of the group are sequentially increased by a second correction value.

Emission targets, such as NOx levels, for gaseous fuelled internal combustion engines that burn a gaseous fuel in a diffusion combustion mode are increasingly more challenging to achieve. A method of fuel injection for an internal combustion engine fuelled with a gaseous fuel comprises introducing a first amount of pilot fuel in a first stage of fuel injection; introducing a first amount of main fuel (the gaseous fuel) in a second stage of fuel injection; and introducing a second amount of main fuel in a third stage of fuel injection. The first and second amounts of main fuel contribute to load and speed demand of the internal combustion engine. Engine maps calibrated for different engine performance can be employed in different regions of the load and speed range of the engine. The engine maps are blended when the engine transitions between two regions; and momentary excursions into different regions do not change the engine calibration.

Emission targets, such as NOx levels, for gaseous fuelled internal combustion engines that burn a gaseous fuel in a diffusion combustion mode are increasingly more challenging to achieve. A method of fuel injection for an internal combustion engine fuelled with a gaseous fuel comprises introducing a first amount of pilot fuel in a first stage of fuel injection; introducing a first amount of main fuel (the gaseous fuel) in a second stage of fuel injection; and introducing a second amount of main fuel in a third stage of fuel injection. The first and second amounts of main fuel contribute to load and speed demand of the internal combustion engine. Engine maps calibrated for different engine performance can be employed in different regions of the load and speed range of the engine. The engine maps are blended when the engine transitions between two regions; and momentary excursions into different regions do not change the engine calibration.

Various methods and systems are provided for an intake manifold for an engine. In one example, an insert comprises an annular body having a top surface, bottom surface, inner surface, and outer surface. The insert further comprises a first groove for coupling an intake air port of an intake manifold to a cylinder head, a second groove for circulating gaseous fuel received from a gas runner of the intake manifold, and one or more openings to fluidically couple the second groove to an interior of the intake air port. The insert is configured to mix gaseous fuel and intake air at a coupling location between the intake manifold and the cylinder head.

An improved body defining a restricted fluid flow passage in a fuel supply system for delivering a gaseous fuel to an internal combustion engine. The body is formed for installation between and fluidly connecting a gaseous fuel supply conduit and a gaseous fuel flow passage that defines a predetermined volume between the restricted fluid flow passage and a nozzle chamber of a fuel injector from which the gaseous fuel is injected into the internal combustion engine. The restricted fluid flow passage has the smallest effective flow area between the gaseous fuel supply conduit and the nozzle chamber. The restricted fluid flow passage is located a predetermined distance from an injection valve seal within the fuel injector. The predetermined distance is calculated as a function of the speed of sound in the gaseous fuel and an opened time of the fuel injector.

Methods and systems are provided for adjusting a location of a fuel injection in response to a substitution rate and a desired EGR flow. In one example, a method may include injecting a first fuel to a combustion chamber via a direct injector positioned to inject directly into the combustion chamber, injecting a second, different, fuel to the combustion chamber via an exhaust port injector positioned to inject toward an exhaust valve of the combustion chamber, and combusting the first and second fuels together in the combustion chamber.