Numerical Investigation of Erosion of a Steam Turbine Blade Due to the Impact of Condensed Water Droplets

Water droplets striking a solid surface at high speeds creates fatigue that results into erosion of the solid surface. This phenomenon is likely to occur in steam turbines and hence it can be very problematic for turbine blade life. At the final stages of the turbine, the steam does not have enough energy to be in the gaseous state so condensation occurs to some extent and liquid droplets form at the trailing edges of the final stator stages. These water droplets travel with steam and continue to hit the rotor stage blades at high impact velocities. This creates high pressures inside the droplets that easily exceeds water hammer pressures for a brief period and then releases which causes fatigue onto the turbine blades in turn eroding the blade. The current research work studies the erosion of steam turbine blade due to the impact of droplets. This study evaluates the one-dimensional model of the droplet striking a solid surface which is obtained by combining the fluid model and the solid model. The fluid model is simply a wave equation of the pressure wave fronts inside the droplet which is derived from the well-known N-S equations. The solid model is also a wave equation for the deformation of the turbine blade when struck by the high-speed droplet. Parametric studies are carried out to investigate the effect of parameters such as impact speed and turbine blade material on pressure and stress of the turbine blade.