Effects of Freestream Turbulence on Turbine Blade Heat Transfer

摘要

Experiments have shown that moderate turbulence levels can nearly double turbine blade stagnation region heat transfer. Data have also shown that turbine blade hear transfer is strongly affected by the scale of turbulence as well as its level. In addition to the stagnation region, turbulence is often seen to increase pressure surface heat transfer. This is especially evident at low to moderate Reynolds numbers. Vane and rotor stagnation region, and vane pressure surface heat transfer augmentation is often seen in a pre-transition environment. Rotor pressure surface augmentation is often seen in a relaminarized post-transition environment. Accurate predictions of transition and relaminarization are critical to accurately predicting blade surface heat transfer. An approach is described which incorporates the effects of both turbulence level and scale into a CFD analysis. The model for the effects of turbulence intensity and scale is derived from experimental data for cylindrical and elliptical leading edges. Results using this model are compared with experimental data for both vane and rotor geometries. There is a twofold purpose to these comparisons. One is to illustrate that using a model which includes the effects of turbulence length scale improves agreement with data. The second is to illustrate where improvements in the modeling are needed.