Lightoff fuel pressure reduction system
Traditionally, during ignition of a gas turbine engine, the fuel control valves are controlled to be nearly closed, in order to provide the small amount of fuel that is necessary to ignite the gas turbine engine. The error that is inherent in providing fuel flow through small openings results in a higher likelihood of start-up failures. Accordingly, a lightoff fuel pressure reduction system is disclosed that uses a pressure reducing regulator on a bypass flow path to temporarily reduce the pressure of fuel supplied to the fuel control valves. In this case, the fuel control valves may be maintained in a more open position during the ignition phase, which reduces the likelihood of ignition failures.
1 . A system for delivering fuel to one or more fuel injectors, the system comprising:
at least one main fuel control valve and a pilot fuel control valve which supply fuel to the one or more fuel injectors;
a lightoff fuel pressure reduction system (LFPRS) valve on a main flow path, between an inlet and the at least one main fuel control valve and the pilot 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 at least one main fuel control valve and the pilot fuel control valve, wherein the pressure reducing regulator is configured to reduce a fuel pressure of fuel flowing through the pressure reducing regulator; and
a vent between the LFPRS valve and the at least one main fuel control valve and the pilot fuel control valve.
2 . The system of claim 1 , further comprising one or more fuel shutoff valves between the vent and the at least one main fuel control valve and the pilot 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 fuel shutoff valve, and a closed state in which fuel cannot flow downstream through the fuel shutoff valve.
3 . The system of claim 2 , wherein the one or more fuel shutoff valves comprise at least two fuel shutoff valves.
4 . The system of claim 1 , wherein the at least one main fuel control valve is at least two main fuel control valves.
5 . The system of claim 1 , wherein the LFPRS valve comprises a ball valve.
6 . The system of claim 5 , wherein the ball valve is actuated by a solenoid.
7 . The system of claim 6 , wherein the LFPRS valve further comprises a valve timing orifice, downstream from the solenoid, that limits a speed at which the ball valve can transition from the closed state to the open state.
8 . A method of using the system of claim 1 , the method comprising, during an ignition phase:
shutting the LFPRS valve;
venting a portion of the main flow path that is downstream from the LFPRS valve using the vent;
opening the at least one main fuel control valve and the pilot fuel control valve; and
igniting a combustion process in a combustor of a gas turbine engine using the one or more fuel injectors.
9 . The method of claim 8 , wherein the system further comprises one or more fuel shutoff valves between the vent and the at least one main fuel control valve and the pilot fuel control valve, and wherein the method further comprises, during the ignition phase, opening the one or more fuel shutoff valves when shutting the LFPRS valve.
10 . The method of claim 8 , further comprising:
after igniting the combustion process, determining when to begin an acceleration phase; and
when determining to begin the acceleration phase, opening the LFPRS valve.
11 . The method of claim 10 , wherein determining when to begin the acceleration phase comprises determining to begin the acceleration phase when an engine speed of the gas turbine engine reaches a predefined threshold.
12 . The method of claim 10 , wherein opening the LFPRS valve comprises gradually opening the LFPRS valve according to at least one parameter.
13 . The method of claim 12 , wherein the at least one parameter comprises an engine speed of the gas turbine engine.
14 . A gas turbine engine comprising:
a compressor;
a combustor downstream from the compressor, wherein the combustor comprises the one or more fuel injectors;
the system of claim 1 positioned, relative to fuel flow, between the inlet and the one or more fuel injectors; and
a turbine downstream from the combustor.
15 . 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.
16 . The system of claim 15 , wherein the LFPRS valve is a ball valve, actuated by a solenoid, and wherein a valve timing orifice, downstream from the solenoid, limits a speed at which the ball valve can transition between the closed state and the open state.
17 . 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.
18 . The method of claim 17 , further comprising:
after igniting the combustion process, determining when to begin an acceleration phase; and
when determining to begin the acceleration phase, opening the LFPRS valve.
19 . The method of claim 18 , wherein opening the LFPRS valve comprises gradually opening the LFPRS valve when the gas turbine engine reaches a predefined engine speed.
20 . The system of claim 1 , wherein the processing system is further configured to control an actuator of the vent to transition the vent between an open state and a closed state.