Predicting the Coefficient of Restitution for Particle Wall Collisions in Gas Turbine Components

Abstract

Jet engines often operate under hostile conditions and are increasingly exposed to fine particulate matter such as sand, ash and dirt. Large amounts of fine particulate ingestion, sand in particular, can damage different engine components through deposition and erosion. The extent of damage depends on the particle-wall interaction, which is further governed by particle velocity, impact angle, particle size, particle material, target material and target surface roughness. Coefficient of restitution, which is the ratio of rebound velocity to impact velocity, encapsulates the effect of all the energy losses occurring during a collision. The current work presents a new model which predicts the energy losses and hence coefficient of restitution for a particle-wall collision. The current work combines elastic plastic deformation and adhesion theories of particle-wall interaction. Plastic deformation losses and adhesion losses are calculated separately based on impact parameters: impact velocity, impact angle, particle/wall material properties. These losses combine together to give the net energy loss during a collision and hence coefficient of restitution. The main objective of this study is to develop a collision model for sand particle interaction in gas turbine components, so the results are compared with available experimental data on coefficient of restitution for sand particles. The coefficient of restitution predictions are also compared with existing experimental data on a wide range of particle sizes and materials. Model predictions are found to be in good agreement with experiments.