Effect of restitution coefficient on inertial particle separator's efficiency

• Online Access: http://hdl.handle.net/2047/d1001925x

Deficiencies of Inertial Particle Separators (IPS) at the inlet of turboshaft engines, operating in harsh environments, have caused significant maintenance costs for the US government and endangered the safety of Operating personnel. In this research, an investigation was conducted to study the sand particle rebound characteristics which are widely used in the design of the Inertial Particle Separators. Experimental and numerical approaches are applied to measure the restitution coefficients. Three different particle accelerator setups were designed to eject high speed small particles and to measure the restitution parameters upon their impact with target surfaces at various conditions. In addition, numerical modeling of fully elastoplastic collision was performed using a commercial finite element software to study the rebound characteristics in detail. Results revealed a strong dependency of normal restitution coefficients on the impact velocity. Also it was found that the tangential restitution coefficients vary vastly with particle size while the impact velocity has no significant effect on tangential restitution coefficients. The results were in complete agreement with previous studies, on functional behavior of restitution coefficients with respect to the incident collision angle. These developed restitution coefficients were integrated into a commercially available computational fluid dynamic software to predict the particle trajectories in a typical IPS model operating in particle-laden environments in accordance with the government standards. The results of IPS efficiency are surprisingly in good agreement with experimental data reported in open literature. Our study further showed that to improve the IPS efficiency, a drastic reduction in normal restitution coefficients is necessary by modifying the IPS's outer shell surface materials. Numerical modeling with reduced normal restitution coefficients demonstrated improvements in the order of 10% in IPS efficiency.