Rotordynamic Forces Due to Turbine Tip Leakage: Part II—Radius Scale Effects and Experimental Verification

Abstract

This paper presents a radius scale actuator disk model, which describes the flow response to a whirling/spinning rotor in an unshrouded turbine. At each azimuth, the upstream-downstream flow variables are matched by the results from a steady blade scale analysis presented in a companion paper, with allowance for mass storage in the stator-rotor region. The new model can accurately predict the magnitude of both direct and cross excitation forces as well as their breakdown into work extraction and pressure effects. The trends versus the mean flow coefficient and interblade distance are predicted. While underpredicted, a trend versus mean rotor tip clearance height is also indicated. Thus, the new model captures the dominant physical effects caused by a whirling/spinning rotor in an unshrouded turbine.