DUAL FUEL SYSTEM AND METHOD FEEDING SAME FUEL AT TWO PRESSURES TO FUEL INJECTOR

A fuel system includes a first fuel subsystem having a supply of a first fuel and at least one fuel pump to provide a high-pressure feed of a first fuel and a low-pressure feed of the first fuel. The fuel system also includes a second fuel subsystem having a supply of a second fuel, and a plurality of fuel injectors. Each fuel injector forms a high-pressure fuel inlet, a low-pressure fuel inlet, a second-fuel inlet, and a combined-fuel outlet passage. A first fuel admission valve is movable to admit the first fuel into the combined-fuel outlet passage displacing some of the second fuel to form a combined fuel charge. A second fuel admission valve admits the second fuel to the combined-fuel outlet passage. The first fuel may include a compression-admission fuel such as diesel, and the second fuel may include an alcohol fuel such as methanol. Providing the first fuel at two different fuel pressures enables the first fuel to serve lubrication and cooling purposes within fuel injector, whilst also providing a component of a segmented combined fuel charge or substantially all of a fuel charge.