Gas turbine fuel control having fuel viscosity compensation to provide improved ignition reliability

Claim 1

A fuel control for improving ignition reliability in a gas turbine having substantially fixed orifice nozzles comprising means for controlling the position of a throttle valve which varies the fuel flow to the turbine to control turbine speed or load over a relatively wide range, a fuel pump operative to supply fuel to the throttle valve at an elevated pump discharging pressure, a bypass valve for diverting fuel from the throttle valve, means located proximate to said nozzles and downstream from all valves in the fuel flow path for generating a signal representative of actual nozzle fuel pressure at least during the ignition period, means for generating a pump discharge pressure reference as a function of a nozzle pressure reference and the actual nozzle fuel pressure during ignition and means for generating a control output for said bypass valve during ignition in response to the actual pump discharge pressure and the pump discharge pressure reference substantially to hold the nozzle fuel pressure at the desired value even over relatively wide ambient temperature changes and corresponding fuel viscosity variations.