Experimental investigation of droplet size influence on low pressure steam turbine blade erosion

Abstract

In the last stages of steam turbines, large droplets (so-called coarse water) are generated from the wet steam flow. These droplets collide with the following rotating blades with almost the peripheral speed of the rotor. This high speed impact is perceived in the form of erosion of low pressure steam turbine blades. Among others, impacting droplet size is a key parameter contributing to the erosion of low-pressure steam turbine blades. At the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) Stuttgart, the effect of droplet size on the erosion of steam turbine blade has been investigated with the help of an erosion test rig. The experiments confirm that the erosion increases with increasing droplet sizes. It is also found that volume loss per droplet impact increases with droplet size with a simple power law relation Erosion ~Ddropletn where value of n is found to be 3.2 up to 3.5 for common blade materials.