Analysis of water drop erosion on turbine blades based on a nonlinear liquid-solid impact model

Water drop erosion is regarded as one of the most serious reliability concerns in the wet steam stage of a steam turbine. One of the most challenging aspects of this problem involves the fundamental solution of the transient pressure field in the liquid drop and stress field in the metal substrate, which are coupled with each other. In this paper, we first solve the fundamental problem of high-speed liquid-solid impact, both analytically and numerically, based on a nonlinear wave model. The transient pressure distribution in liquid (include shock wave) and transient stress distribution in solid are obtained for representative water drop-1Cr13 impacts, with impact speed varying from 10 m/s to 500 m/s. The relationship between the most important parameters characterizing impact and incident speed is established. With the statistics of water drop impact on the blade, a simple fatigue model is employed in this paper to obtain the lifetime map on a blade surface under typical working conditions, in terms of both impact times and operation hours. The most dangerous water drop erosion regions and operating conditions of the steam turbine blade are deduced. These results are useful for evaluating the water drop erosion mechanisms based on the fundamental solution of liquid-solid impact. © 2009 Elsevier Ltd. All rights reserved.