Prediction of Surface Roughness and Incidence Effects on Turbine Performance

The use of a Navier-Stokes analysis to predict the change in turbine efficiency resulting from changes in blade surface roughness or incidence flow angles is discussed. The results of a midspan Navier-Stokes analysis are combined with those from a quasi-three-dimensional flow analysis code to predict turbine performance. A quasi-three-dimensional flow analysis code was used to determine turbine performance over a range of incidence flow angles. This analysis was done for a number of incidence loss models. The change in loss due to changes in incidence flows computed from the Navier-Stokes analysis is compared with the results obtained using the empirical loss models. The Navier-Stokes analysis was also used to determine the effects of surface roughness using a mixing length turbulence model, which incorporated the roughness height. The validity of the approach used was verified by comparisons with experimental data for a turbine with both smooth and rough blades tested over a wide range of blade incidence flow angles.