Built-in test of actively controlled fuel nozzles

A method for detecting performance degradation of an Actively Controlled Fuel Nozzle (AC Nozzle) in a gas turbine engine, the gas turbine engine comprising:

• a Main Fuel Metering Valve (MFMV), a Fuel Flow Meter (FFM) downstream from the MFMV, a manifold and fuel lines downstream from the FFM, a Number of Proportional Metering Valves (PMVs), and a plurality of AC Nozzles, wherein each Proportional Metering Valve (PMV) of the Number of PMVs associated with a AC Nozzle of the plurality of AC Nozzles on each of the fuel lines;
• and the method comprising:
• operating the gas turbine engine under a normal operating condition to power the gas turbine engine at a constant speed by providing a fuel flow to a combustion chamber and maintaining a constant fuel flow rate of the fuel flow to the combustion chamber via the MFMV;
• determining a delta pressure PDelta-Normal across the N number of PMVs as the gas turbine engine is operating under the normal operating condition, wherein determining the delta pressure PDelta-Normal includes:
• measuring a PF3 pressure downstream from the FFM, measuring a fuel flow rate at the FFM, and measuring a combustor pressure Pb within the combustion chamber;
• and
• subtracting a predicted pressure drop Pman_plum from the PF3 pressure to determine a Pvup value and subtracting the combustor pressure Pb from the Pvup value;
• controlling a selected PMV from the N number of PMVs to modify a fuel flow rate to the associated AC Nozzle to cause the gas turbine engine to operate under a modified fuel flow condition;
• determining a delta pressure PDelta-Modified across the N number of PMVs as the gas turbine engine is operating under the modified fuel flow condition;
• and
• comparing the delta pressure PDelta-Normal with the delta pressure PDelta-Modified to determine whether the selected AC Nozzle is uncalibrated or has failed.

A method for detecting performance degradation of an Actively Controlled Fuel Nozzle (AC Nozzle) in a gas turbine engine, the gas turbine engine comprising:

• a Main Fuel Metering Valve (MFMV), a Fuel Flow Meter (FFM) downstream from the MFMV, a manifold and fuel lines downstream from the FFM, a Number of Proportional Metering Valves (PMVs), and a plurality of AC Nozzles, wherein each Proportional Metering Valve (PMV) of the Number of PMVs associated with a AC Nozzle of the plurality of AC Nozzles on each of the fuel lines;
• and the method comprising:
• operating the gas turbine engine under a normal operating condition to power the gas turbine engine at a constant speed by providing a fuel flow to a combustion chamber;
• maintaining the fuel flow rate of the fuel flow to the combustion chamber of the gas turbine engine at a constant fuel flow rate;
• determining a delta pressure PDelta-Normal across the N number of PMVs as the gas turbine engine is operating under the normal operating condition;
• selecting a PMV from the N number of PMVs and the associated AC Nozzle from the plurality of AC Nozzles;
• controlling the selected PMV to modify a fuel flow rate to the associated AC Nozzle to cause the gas turbine engine to operate under a modified fuel flow condition;
• determining a delta pressure PDelta-Modified across the N number of PMVs as the gas turbine engine is operating under the modified fuel flow condition, wherein determining the delta pressure PDelta-Modified includes:
• measuring a PF3 pressure downstream from the FFM, measuring a fuel flow at the FFM, and measuring a combustor pressure Pb within the combustion chamber while the gas turbine engine is operating under the modified fuel flow condition;
• referencing a predicted pressure map to determine a predicted pressure drop Pman_plum across the manifold and the fuel lines at a point downstream from the FFM and upstream from the manifold and the fuel lines while the gas turbine engine is operating under the modified fuel flow condition;
• subtracting the predicted pressure drop Pman_plum from the PF3 pressure to determine a Pvup value and subtracting the combustor pressure Pb from the Pvup value while the gas turbine engine is operating under the modified fuel flow condition;
• and
• comparing the delta pressure PDelta-Normal with the delta pressure PDelta-Modified to determine whether the associated AC Nozzle is uncalibrated or has failed.