Impact of operating conditions on the transitional flow in a low-pressure fast turbine cascade

Abstract

The transition of boundary layer from laminar to turbulent is more probable to happen across various components of a turbomachine. If narrowed down to a case of low-pressure turbine cascade, the transition of flow in boundary layer is due to separation induction. Due to this, blade losses are observed and it depends on various physical characteristics such as size and the length of the separation bubble. The physical characteristics can vary based on the variation of flow Reynolds number, expansion ration of the flow and the inlet flow turbulence intensity. Such characteristics can be studied using computational techniques, CFD analysis. Various computational techniques can be used for this scope of study, ranging from Reynolds Averaged Navier Stokes to Direct Numerical Simulation modelling, and each technique have its own set of advantages and disadvantages.

The objective of this thesis is to present and acknowledge on how these separation bubble physical characteristics vary due to the variation of flow expansion ratio and variation of exit isentropic Reynolds number for a SPLEEN blade cascade. Direct Numerical Simulation technique will be adapted for this thesis, due to its ability to accurately predict separation bubble location and size but compromising to relatively high computational power requirement.