ROTORDYNAMIC FORCES DUE TO TURBINE TIP LEAKAGE .1. BLADE SCALE EFFECTS

An experimental and theoretical investigation has been conducted on ro tordynamic forces due to nonaxisymmetric turbine tip leakage effects. This paper presents an actuator disk model that describes the flow res ponse to a finite clearance at the rotor tip. The model simplifies the flow field by assuming that the radially uniform flow splits into two streams as it goes through the rotor. The stream-associated with the tip clearance, or the underturned stream, induces radially uniform unl oading of the rest of the pow, called the bladed stream. Thus, a shear layer forms between the two streams. The fraction of each stream and the strength of shear layer between the two are found as functions of the turbine loading and flow parameters without resorting to empirical correlations The results show that this model's efficiency prediction s compare favorably with the experimental data and predictions from va rious correlations. A companion paper builds on this analysis to yield a model of the three-dimensional disturbances around an offset turbin e and to predict the subsequent cross forces.