Turbine Design and Performance at Large Tip Clearance of Unshrouded Rotor Cascades

Abstract

The aerodynamic design of the turbines driving the pumps of the Vinci expander cycle engine is discussed. Focus is put on the turbine driving the hydrogen pump of the engine. Design methods for stage peripherals are presented. Air test data for the outlet duct are shown. The vane-less and diffuser-less concept performs as expected in reference conditions. As rotor outlet swirl increases, losses increase but stay within acceptable and anticipated limits. The stage design is presented. It can be shown to be significantly dependent on the fluid driving the turbine, which deviates from ideal gas law. Performance of the turbine stage is presented in terms of characteristic variables. Three independent assessments are available: Meanline calculation and analyses by Computational Fluid Dynamics (CFD) is compared to air test data. The consistency is found satisfying after correction of test and meanline data for deviation in Reynolds number and gas properties. This is necessary as the CFD analyses are performed in engine conditions. – Explicit treatment of gas data is seen as key to make use of air test data for predication of operation in engine conditions. The meanline calculations are based on a dedicated loss model derived for reference conditions. The good agreement with test and CFD data even in off-design conditions can be seen as verification of this loss model for future application.