INTEGRATED DESIGN OF ROTOR LEADING EDGE AND CAVITY FLOWS IN AN AXIAL SHROUDED TURBINE

摘要

In this paper we examine the impact of rotor leading edge modifications on stage efficiency through their influence on the flow field and their interaction with the cavity flows. Three rotor leading edge modifications have been examined. The interaction of the cavity and main flows results in a false incidence on the rotor blade. The re-entry of part of the leakage flow back into the mainstream heavily impacts the main flow path, thus generating a false incidence on the downstream bladerow for the span locations above 75%. The initial leading edge metal angle of -19° (compared to the axial direction) was modified to +12°to better match the flow field as this was experimentally measured and computationally predicted. An efficiency gain of 0.21% was attributed to loss minimization due to the corrected incidence. Nevertheless, a modification of the metal angle to -30° met with success, increasing the efficiency by 0.19%. A supplementary computational analysis revealed that the lean imposed on the blade caused the tip passage vortex to lose strength and migrate to a lower span location.