A system for exchanging of different fuels that can be used for operation of an engine. The system includes a fuel exchange unit, a control and an exchange return conduit. The fuel exchange unit is configured to deliver a first fuel at pressure into the injections system given a switched-off engine, in order to replace a second fuel, which is located in the injection system, with the first fuel. A fuel delivery system includes a media converter which includes a deflectable element. The media converter is driven by a drive unit via the fluid by way of the fluid being able to be led at a varying pressure to the media transformer via a first feed conduit, and is configured to deliver the fuel via a pumping effect.

A method for operating an engine, comprising port injecting a first quantity of a first gaseous fuel in a cylinder cycle and direct injecting a second quantity of a secondary injectant in the cylinder cycle as a function of a desired air-to-fuel ratio (AFR), the desired AFR based on a temperature of an engine cylinder valve. The desired AFR may be outside the AFR range available during natural gas combustion alone and thus allows for cooler engine operation.

Fuel management system for enhanced operation of a spark ignition gasoline engine. Injectors inject an anti-knock agent such as ethanol directly into a cylinder. It is preferred that the direct injection occur after the inlet valve is closed. It is also preferred that stoichiometric operation with a three way catalyst be used to minimize emissions. In addition, it is also preferred that the anti-knock agents have a heat of vaporization per unit of combustion energy that is at least three times that of gasoline.

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.

In a dual-fuel fuel injector comprising a first injector unit for a first injector operating mode using a first main fuel and a second injector unit for a second injector operating mode using a second main fuel and an injector-reservoir, the reservoir is connected at one end to a first main fuel supply and at the opposite end to a second main fuel supply with a separating element disposed in the injector reservoir so as to be movable between the opposite ends so that, in each operating mode, the full volume of the reservoir can be used for accommodating the respective main fuel.

An objective of the present invention is to stabilize the fuel injection amount for each cylinder and to execute fuel injection control accurately in a single-pressure-feed dual-injection type alcohol fuel injection system. An engine includes two injection valves and and a single-pressure-feed dual-injection type fuel supply system. The fuel supply system is configured such that fuel is injected sequentially in two cylinders during the pressure-feed-interval period from the execution of one fuel pressure-feed operation to the execution of the next fuel pressure-feed operation. If the alcohol concentration in the fuel is higher than a predetermined determination value γ at a startup operation time, an ECU executes only a cylinder injection for the first of the two cylinders described above, and executes both an intake passage injection and a cylinder injection for the second cylinder. Thus, even if the fuel pressure decreases due to the fuel injection for the first cylinder, the required fuel injection amount can be reserved for the second cylinder.

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.

A fuel injector feeds fuel to a combustion chamber of a cylinder of a dual-fuel engine and includes: a main body having a needle guide; a nozzle needle guidable in the needle guide; a needle fuel chamber defined by the main body, coupleable to the combustion chamber, wherein the orifices are open in a first position of the nozzle needle and closed in a second position of the nozzle needle; a first line arranged in the main body, and being coupled to the needle fuel chamber, via the first line a fuel being introduceable into the needle fuel chamber. In the main body a second line is coupleable to the needle guide and to a control chamber of a control valve of the fuel injector, wherein via the second line a fuel is feedable to the needle guide as barrier fluid and to the control chamber as working fluid.

A dual-fuel internal combustion engine includes: cylinders for combusting a first liquid fuel having a first ignitability in a first operating mode, and a second liquid fuel having a second lesser ignitability, in a second operating mode; a main injection system including a main injector for each cylinder, for feeding the first liquid fuel to the respective cylinders in the first operating mode and for feeding the second liquid fuel to the respective cylinders in the second operating mode; and a pilot injection system including a pilot injector for each cylinder, via which the first liquid fuel can is feedable to the respective cylinders in the second operating mode for igniting the second liquid fuel. The main and pilot injection systems are coupled such that in the second operating mode the first liquid fuel, is feedable to the respective main injector as a working fluid and/or a barrier fluid.

A dual-fuel supply system (100) for direct injection for engines of heavy vehicles, comprising: a supply line of a combustible liquid (160); a supply line of a combustible gas (170); a plurality of injectors (150) in fluid communication with the supply line of the combustible liquid (160) and with the supply line of the combustible gas (170); a pressure regulator device (1) for regulating the combustible gas; an electronic control unit (ECU) configured to control the supply of combustible liquid and of the combustible gas to the injectors (150), the electronic control unit (ECU) being configured to control the pressure regulator device (1) to track a reference pressure (p.sub.target) according to a feedback logic.