Methods of Predicting the Tip Clearance Effects in Axial Flow Turbomachinery

Abstract

Using the author’s earlier flow model for the tip clearance flow, an expression is derived for the decrease in stage efficiency due to tip clearance. The analysis which includes all the dominant flow and blade parameters that affect the flow in the clearance region is compatible with fundamental physical principles, though not precise mathematically. The predictions agree closely with several compressor, fan, pump, and turbine data available. An alternate model which takes into account the presence of the vortex core is proposed. The theoretical treatment of the flow, more complete than hitherto available, predicts blade-to-blade variation in outlet angles accurately and stagnation pressure losses qualitatively. The predictions are compared with various experimental data available in the literature.