Numerical Investigation of Wake-Shock Interactions and Clocking in a Transonic HP Turbine

A quasi-three-dimensional, blade-to-blade, time-accurate, viscous solver was used for the clocking optimization of a modern transonic heavy-duty, two stage gas turbine. Both stators and rotors operate in a transonic regime with fish-tail shock systems at the blade row exit. These shock systems interact with both stator and rotor wakes. A sensible reduction in the strength of shock waves was observed due to the upstream blade row wake passing. Such wake-shock interactions occur in the inter-blade gap, around locations which are fixed in the frame of reference of the downstream blade-row. The exploitation of such an effect to optimize the axial/circumferential position of blade rows is still compatible with the axial gap values commonly used for these kinds of stages. The results of the clocking investigation will be presented and discussed in terms of unsteady blade loading and efficiency variations.