Method of switching from a liquefied gas fuel to a liquid fuel being provided to a direct injection combustion engine, and direct injection bi-fuel system for such an engine

摘要

A method of switching between liquefied gas fuel and liquid fuel consuming modes of a direct injection combustion engine including pumping liquefied gas fuel to a high pressure, pump for pumping the liquefied gas fuel to a high pressure rail of the engine during the liquefied gas fuel consuming mode, switching to the liquid fuel consuming mode, pumping the liquid fuel to the high pressure pump, flushing liquefied gas fuel via a return line between the high pressure pump and a fuel tank, controlling pump operation, controlling flow through the return line, and controlling the pressure of the fuels.

主权项

1. A method of switching from a liquefied gas fuel being provided to a direct injection combustion engine during a liquefied gas fuel consuming mode, to a liquid fuel being provided to the engine during a liquid fuel consuming mode, the method comprising the steps of:
a) pumping a liquefied gas fuel by means of a liquefied gas fuel pump to a high pressure pump which is configured to pump liquefied gas fuel to a high pressure rail of the direct injection combustion engine during the liquefied gas fuel consuming mode; b) switching from the liquefied gas fuel consuming mode to the liquid fuel consuming mode; c) pumping a liquid fuel at a pressure at least equal to the vapor pressure of the liquefied gas fuel to the high pressure pump, by means of at least a first liquid fuel pump, wherein liquefied gas fuel is flushed via a return fuel line between the high pressure pump and a fuel tank; d) stop pumping liquefied gas fuel to the high pressure pump; e) stop flushing liquefied gas fuel by closing a return valve in the return fuel line; f) after a predetermined delay after step e) and during the liquid fuel consuming mode, opening the return valve for a predetermined time to flush liquid fuel comprising any residual liquefied gas fuel via the return fuel line; and g) decreasing the pressure of the liquid fuel pumped to the high pressure pump to a pressure lower than the vapor pressure of the liquefied gas fuel.