Patent ID: 7162874

Claim:
A gas turbine engine comprising an air compressor, a premixer for mixing fuel with a first portion of compressed air to provide a fuel/air mixture the premixer having a fixed area exit, a combustor for receiving and combusting the mixture to provide combustion gases, the compressor also providing a second portion of the compressed air to an exit of the combustor as dilution air, a compressed air valve for controlling the first compressed air portion, a fuel valve for controlling fuel flow to the premixer, and a turbine operatively connected to the combustor for expanding the combustion gases and the dilution air to drive the compressor and provide net power, the engine further comprising: (1) an engine controller responsive to engine power output and engine power demand for controlling the fuel valve and the air valve, wherein in response to a decrease in engine power output relative to engine power demand the controller will increase the fuel flow and air flow to the premixer, whereby the mixture flow velocity through the premixer exit will also increase, and (2) means for diverting part of the second portion of compressed air to bypass at least the turbine, and wherein the engine controller is also operatively connected to the diverting means for selectively controlling the bypass air flow to maintain at least a selected minimum mixture flow velocity through the premixer exit.