Size- and Temperature-Dependent Collision and Deposition Model for Micron-Sized Sand Particles

Sand ingestion and deposition in gas turbine engine components can lead to several operational hazards. This paper discusses a physics-based model for modeling the impact, deposition, and sticking of sand particles to surfaces. The collision model includes both normal and tangential components of impact. The normal collision model divides the impact process into three stages, the elastic stage, the elastic-plastic stage, and full plastic stage, and the recovery process is assumed to be fully elastic. The adhesion loss in the recovery stage is described using Timoshenko's model and Tsai's model, and shows that the two models are consistent under certain conditions. Plastic deformation losses of surface asperities are also considered for particle-wall collisions. The normal impact model is supplemented by an impulse-based tangential model, which includes both sliding and rolling frictions. Sand properties are characterized by size and temperature dependencies. The predicted coefficient of restitution (COR) of micron-sized sand particles is in very good agreement with experimental data at room temperature and at higher temperatures from 1073 K to 1340 K. The predicted COR decreases rapidly at temperatures above 1340 K. There is a strong interplay between the size-dependent properties of micron sand particles and the temperature dependency of yield stress on the collision and deposition characteristics. This is the first physics-based high temperature model including translation and rotation of micron-sized sand particles with sliding and rolling modes in the gas turbine literature.