Lightoff fuel pressure reduction system

A system for delivering fuel in a gas turbine engine, the system comprising:

• an inlet;
• a pilot fuel control valve which controls an amount of fuel flowing to a pilot manifold;
• a main fuel control valve which controls the amount of fuel flowing to a main manifold;
• a lightoff fuel pressure reduction system (LFPRS) valve on a main flow path, between the inlet and the pilot fuel control valve and the main fuel control valve, wherein the LFPRS valve is configured to switch between an open state, in which fuel can flow downstream through the LFPRS valve, and a closed state in which fuel cannot flow downstream through the LFPRS valve;
• a processing system configured to control the LFPRS valve to transition between open and closed states;
• a pressure reducing regulator, connected in parallel to the LFPRS valve, on a bypass flow path between the inlet and the pilot fuel control valve and the main fuel control valve, wherein the pressure reducing regulator is configured to reduce a fuel pressure of fuel flowing through the pressure reducing regulator;
• a vent between the LFPRS valve and the pilot fuel control valve and the main fuel control valve;
• and
• one or more fuel shutoff valves between the vent and the pilot fuel control valve and the main fuel control valve, wherein each of the one or more fuel shutoff valves is configured to switch between an open state, in which fuel can flow downstream through the one or more fuel shutoff valves, and a closed state in which fuel cannot flow downstream through the one or more fuel shutoff valves.

A method of starting a gas turbine engine having a combustor, the method comprising, during an ignition phase:

• shutting a lightoff fuel pressure reduction system (LFPRS) valve, on a main flow path between an inlet and a pilot fuel control valve which controls an amount of fuel flowing to a pilot manifold and a main fuel control valve which controls the amount of fuel flowing to a main manifold, based on a transition of the LFPRS valve between open and closed states, wherein the LFPRS valve is connected in parallel to a pressure reducing regulator on a bypass flow path between the inlet and the pilot fuel control valve and the main fuel control valve, wherein the pressure reducing regulator is configured to reduce pressure in a portion of the main flow path that is downstream from the LFPRS valve to an ignition pressure;
• decreasing the pressure in the portion of the main flow path that is downstream from the LFPRS valve;
• opening the pilot fuel control valve and the main fuel control valve;
• and
• igniting a combustion process in the combustor using one or more fuel injectors.