Patent ID: 8776529

Claim:
A fuel delivery system for delivering fuel to a gas turbine engine, the fuel delivery system comprising: a fixed critical flow nozzle connected to a fuel source, the fixed critical flow nozzle having an orifice throat with a fixed effective cross-sectional area; a variable critical flow nozzle connected to the fuel source and in parallel with the fixed critical flow nozzle, the variable critical flow nozzle having an orifice throat with a variable effective cross-sectional area, the variable critical flow nozzle further having: an inlet; a nozzle having a converging-diverging shape and including the orifice throat and a recovery section downstream of the orifice throat; and a needle mounted on a spring biased piston, the needle positionable in the orifice throat to adjust the effective cross-sectional area of the orifice throat based upon a fuel pressure at the inlet; a first fuel nozzle connected to the fixed critical flow nozzle for delivering fuel to the gas turbine engine; and a second fuel nozzle connected to the variable critical flow nozzle for delivering fuel to the gas turbine engine.