Patent ID: 7003939

Claim:
A fuel injection system for a staged combustion chamber of a gas turbine engine, comprising: a control valve unit for variably adjusting a total fuel mass flow (WF) to pilot burners and main burners of the engine; a staging valve unit provided downstream of the control valve unit for variably splitting the total mass fuel flow (WF) in a staged mode between the pilot burners and the main burners; an engine control unit for controlling the control valve unit and the staging valve unit, the engine control unit controlling the staging valve unit to supply a certain quantity of fuel to the pilot burners under all operating conditions and to supply fuel to the main burners in the staged mode only at higher engine performance; the engine control unit constructed and arranged to calculate a staging parameter (SP) reflecting a load of the combustion chamber based on at least one engine operating parameter and control the staging valve unit to variably split the total mass fuel flow (WF) in the staged mode between the pilot burners and the main burners based on the staging parameter (SP); the engine control unit constructed and arranged to compute a difference between a nominal staging point and an actual staging point at a summation step to determine in which of the staged mode and a non-staged mode the engine should operate; and the engine control unit including a timer operating in response to a result from the summation step to delay change between the staged and non-staged mode if a period of time since a previous staging event is smaller than a predetermined time constant.