Engine fuel control system and method

A fuel control system for an engine including a combustion chamber, the system comprising:

• a fuel supply;
• at least one fuel injector with a calibrated nozzle to direct a fuel flow from the fuel supply into a combustion chamber of an engine, the calibrated nozzle having a known fuel flow vs. pressure drop characteristic;
• a servo valve connected between the fuel supply and the calibrated nozzle to meter the fuel flow from the fuel supply to the calibrated nozzle;
• a pressure transducer operably associated with the calibrated nozzle to measure a pressure drop in the fuel flow across the at least one calibrated nozzle and generate a first signal representative of the measured pressure drop;
• and
• a controller operably associated with the pressure transducer to receive the first signal therefrom, the controller configured to generate a second signal representative of the actual fuel flow through the calibrated nozzle based on the first signal and the known fuel flow vs. pressure drop characteristic of the calibrated nozzle, the controller operably associated with the servo valve to control the metering of the fuel flow by the servo valve based on a comparison between the second signal and a third signal representative of a desired fuel flow to the engine.

A method of providing a desired fuel flow rate to an engine through a fuel circuit including at least one fuel injector with a calibrated nozzle to direct the fuel flow into a combustion chamber of the engine and a servo valve to meter the fuel flow to the nozzle, the method including the steps of:

• calibrating the nozzle to determine the at least one nozzle's fuel flow vs. pressure drop characteristic;
• measuring a pressure drop in the fuel flow across the nozzle during operation of the engine;
• determining a fuel flow rate based on the measured pressure drop and the fuel flow vs pressure drop characteristic of the nozzle;
• and
• controlling the metering of the fuel flow by the servo valve based on a comparison between the determined fuel flow rate and the desired fuel flow rate.

A method of providing a desired fuel flow rate to an engine through a fuel circuit including at least one fuel injector with a calibrated nozzle to direct the fuel flow into a combustion chamber of the engine and a servo valve to meter the fuel flow to the nozzle in response to a control signal, the method including the steps of:

• calibrating the nozzle to determine a fuel flow vs. pressure drop characteristic for the nozzle;
• calibrating the servo valve to determine a predicted fuel flow vs. control signal relationship for the servo valve;
• measuring a pressure drop in the fuel flow across the nozzle during operation of the engine;
• determining a fuel flow rate based on the measured pressure drop and the fuel flow vs pressure drop characteristic of the nozzle;
• and
• correcting the predicted fuel flow vs. control signal relationship for the servo valve based on the determined fuel flow rate.