A validation study for a new erosion model to predict erosive airfoil defouling

Abstract

A new defouling erosion model for Lagrangian particle tracking is used to predict defouling of amorphous, heterogeneous coatings such as those typically found in aircraft compressors. The main problem description, the mathematical formulation and the underpinning experiment of the model are presented in a previous communication by the authors. In this work, the Ansys CFX implementation of the model is described and an experiment is presented for the validation of the model. Air flows laden with a number of dry-ice particles are observed in an optically accessible stream channel containing a flat plate target. The defouling process of these particles is recorded with HSCs and the main parameters, such as indentation size in fouling layers, are processed and compared to corresponding numerical results. The model parameters considered are particle impact velocity and angle as well as particle and fouling material. Typical coatings which are relevant to commercial aircraft defouling processes are investigated. The target plate angle and the air velocity are varied and dry-ice particles of random size and shape are injected into the flow. The experiment is set up in a wind-tunnel test-rig and all recordings are made using two HSCs, a digital camera and Prandtl probe measurement. Experimental and numerical defouling results show good overall agreement for steep target angles but significant deviations for low target angles. Potential improvement to the defouling erosion model is discussed based on these results. The model as presented is used in large-scale compressor defouling simulations in the development process of on-wing aircraft maintenance systems.