Iris control for gas turbine engine air brake

摘要

A gas turbine engine of the two shaft free turbine type has a first gasifier turbine for driving a compressor to supply air to a combustor for combustion with fuel to produce motive fluid for driving the compressor turbine and a second free wheeling power turbine. An air brake with a compressor impeller directly coupled to the power turbine has an inlet and an exhaust and a close coupled iris throttle assembly for regulating the inlet flow of air into the compressor to obtain maximized power turn down ratios without aerodynamic instability.