Numerical Simulation of Flow Field in Scarfed Nozzle of Torpedo Turbine

A three-dimensional, viscous, steady computational fluid dynamics (CFD) analysis is performed for investigating the flow field in the scarfed nozzle of a torpedo turbine by solving RANS-Navier-Stocks equations and RNG turbulence model. The flow detail and performance of the nozzle are studied in varying pressure ratio conditions. Numerical simulation results show that the inner complex flow characteristics in the scarfed nozzle are predicted. When the nozzle is in over-expansion state, the shock wave and flow separation appear at nozzle outlet, and the performance is degraded rapidly with the pressure ratio increasing. This situation should be avoided in nozzle design. As the pressure ratio is larger than the one at critical mass flow rate, the mass flow rate of the nozzle keeps the maximum.