The Westinghouse/Rolls-Royce WR-21 marine gas turbine with an intercooled, recuperated thermodynamic cycle utilises exhaust heat to provide excellent efficiency not only at full power but also at part power. Vital to the success of the engine and the optimisation of fuel consumption is the Variable Area Nozzle (VAN) which is used to control turbine capacity across the power range. By continuously monitoring and controlling turbine capacity, the heat recovered by the recuperator is optimised across the power range.
The efficiency of the power turbine variable stage at low power (low flow) and its ability to deliver full power (high flow) is vital to the success of the engine. Success also requires precise control of the variable vane, easy maintenance and good reliability in a hot, mechanically hostile environment.
This paper describes the aerodynamic and mechanical design, rig verification and early engine experience of the variable power turbine stage.