Analysis of Surface Roughness Effects on the Performance of a Gas Turbine Stage

Today, gas turbines are considered as one of the most important equipment in energy industry and with a lot of applications in other industries. So far, very few CFD studies on the effect of roughness on turbine performance have been performed. This paper presents numerical study of roughness which affects performance of a single stage axial flow turbine. Numerical calculations have been performed using an in-house developed software in the C environment employing Roe scheme to solve governing equations in generalized coordinates. In order to simulate the turbulent flow the Baldwin-Lomax model and for simulating the roughness the Cebeci-Chang model is used. To realize the roughness effects in a turbine stage, several roughness heights in transitionally rough and fully rough flow regimes on the stator and rotor blades have been simulated. Results show that the efficiency is reduced with increasing roughness height. Also, with increasing the surface roughness of the stator and rotor, deviation angle will increase and thus the work coefficient will reduce. Moreover, the loss coefficient in both stator and rotor blades is increased especially, suction surfaces are faced with more losses.