An Overview of Droplet Impact Erosion, Related Theory and Protection Measures in Steam Turbines

Erosion of last-stage steam turbine blades is a well-known problem in the turbine manufacturing industry. Damage of structure and loss of efficiency are the common problems associated with erosion. Understanding of the phenomenon leading to low-pressure blade erosion, erosion protection and erosion prediction has been the topic of scientific research and interest in the steam turbine manufacturing community since the start of the nineteenth century. Although several changes in both the steam turbine stage design and steam properties have been adopted to eliminate this problem, none of them have proved to eradicate this phenomenon completely. The only option left for the scientists and designers is to mitigate the process by utilising materials with high erosion resistance. This requires the development of high erosion-resistive materials and then quantitative confirmation of their erosion resistance by using some precise and accurate laboratory methods reflecting the conditions in the last stage of steam turbines. An overview of droplet impact erosion and related theory has been addressed in this chapter. Moreover, different methods to quantify erosion on a laboratory scale will be presented. In addition, different measures to mitigate erosion in low-pressure stages of steam turbines will be described. In the end, different droplet impact erosion prediction approaches will be discussed.