Experimental and Numerical Investigation of the Mechanical and Aerodynamic Particle Size Effect in High-Speed Erosive Flows

Abstract

Aircraft engines are subject to deterioration due to solid particle erosion. The environmental particulates encountered in service often feature broad particle size distributions and a generally large scatter of particle properties. In order to numerically calculate the erosive change of shape of the components, experimentally calibrated erosion models are required. Due to aerodynamic and mechanical particle size effects, erosion tests with different particle size distributions have to be calibrated individually. In this study, erosion experiments under high-pressure compressor conditions are conducted using a sand-blast type erosion rig. Flat plates out of Ti6Al4V were eroded at different impingement angles. The erodent used was quartz sand with size distributions corresponding to standardized Arizona Road Dust (ARD) grades A2, A3, and A4. The particle impact conditions were investigated using a high-speed shadowgraphy technique in combination with computational fluid dynamics (CFD) computations. Dimensional analyses were carried out in respect to the particle transport process and the material removal process. A nondimensional erosion model is derived. The experimental shadowgraphy results are corrected using numerically calibrated similarity parameters for the particle impact conditions. Thus, the influence of the aerodynamic particle size effect was eliminated by correcting the impact conditions. The isolated mechanical particle size effect is demonstrated. It is shown that wear increases and that the modeled erosion rate maximum shifts toward larger impact angles when using coarser particle size distributions.