Transient gaseous fuel flow scheduling

A method for controlling gaseous fuel in an aircraft, the aircraft comprising:

• an aircraft engine comprising:
• a primary gas path including, in fluid communication and in series:
• a compressor:
• a combustor fluidly connected to an outlet of the compressor;
• and
• a turbine section fluidly connected to an outlet of the combustor, the compressor supplying compressed air to the combustor:
• a pressure sensor operable to gather a pressure measurement of a pressure in the primary gas path at or upstream of the combustor;
• a fuel control system including:
• a metering device in a fuel flow conduit operable to control flow of a gaseous fuel through the fuel flow conduit and to the combustor:
• a computer-readable medium storing:
• feedback logic operable to account for an ambient condition and/or an engine condition in achieving a requested engine state, and output a liquid fuel flow request based on a fuel flow schedule for liquid fuel;
• predictive logic operable to output a predictive logic gain dependent upon a measured engine speed of the aircraft engine;
• and
• compressibility logic operable to output a compressibility gain correlated to the pressure measurement of the pressure in the primary gas path at or upstream of the combustor;
• and
• a control module operatively connected to the metering device, wherein the control module includes an input line operable to receive a command input indicative of the requested engine state, wherein the control module is configured to:
• receive the liquid fuel flow request from the feedback logic;
• receive the predictive logic gain from the predictive logic;
• receive the compressibility gain from the compressibility logic;
• generate a gaseous fuel flow request by modifying the liquid fuel flow request based on the compressibility gain and the predictive logic gain;
• and
• control the metering device to achieve the requested engine state based on the gaseous fuel flow request,
• the method comprising:
• receiving a proportional-integral-derivative (PID) gain input at the control module;
• receiving a compressibility factor input at the control module;
• generating the gaseous fuel flow request using the control module;
• and
• controlling the metering device to achieve the commanded engine state based on the generated gaseous fuel flow request.