Calculation of solid particle erosion in a multistage turbine

Abstract

This thesis presents a computer package developed to calculate the blade erosion rates in multistage turbines that use particle-laden hot expansion gases. This package is an extension of the single-stage erosion code presented in an earlier work. The present package calculates gas flow and particle trajectories in each stage. The calculated particle outlet conditions of given stage are processed statistically to generate the particle inlet conditions to the next stage enabling trajectory and erosion calculations to be advanced beyond a single turbine stage. The package allows erosion predictions to be obtained either based on the semiempirical erosion formula presented earlier or by using an improved model which relies upon direct interpolation of available experimental data. This computer package has been applied to a four-stage electric utility gas turbine. Erosion damage primarily occurs at the leading and trailing edges of the blades and is usually confined to pressure surfaces. It is found that, in addition to the first stage rotor blades, as indicated in earlier studies, the second stage rotor and the second andthir stage stator blades may also be exposed to critical erosion damage. The useful life of the machine appears to be dictated by the thinning of the first stage rotor trailing edge, but the'other high erosion points indicated by this study should also be effectively protected for feasible turbine operation. Recommended methods of controlling blade erosion and some general guidelines for the design of an erosion resistant turbine are indicated.