3-D computational fluid dynamic analysis of effect of tip clearance on the performance of impulse turbine for wave energy conversion

This paper depicts numerical analysis on impulse turbine of 0.6 m diameter with fixed guide vanes for wave energy conversion. From the earlier investigations, it is found that one of the reasons for the mismatch between computed and experimental data is due to neglecting tip clearance effect. Hence, a three-dimensional (3-D) model with tip clearance has been generated with structured grids to predict the internal flow and performance of the turbine. As a result, it is found that the comparison between computed and experimental data is good. Computation has been carried out for various tip clearances to understand the effect of tip clearance leakage flow on such unconventional turbine. The change in flow behavior in the turbine blade passage due to tip clearance flow has been studied by comparing the results with without tip clearance, which is impossible by experiments. It is predicted that the efficiency of the turbine has been reduced about 4%, due to tip clearance flow at higher flow coefficients.