NUMERICAL MODELLING OF EROSION IN HIGHLY-LOADED AXIAL FLOW FANS

Particle laden flows are common in gas turbine applications and may be responsible for both fouling and erosion phenomena. The latter phenomenon is usually found in the operating environment which results from the transport of unfiltered solid or molten particles that typically drive the erosive process. Several studies correlate the erosion to a degradation of aerodynamic performance if the blades retain their structural integrity driven by the original blade profiles' deterioration. Reported limiting factors in eroded turbomachinery operations mostly correlated with the flow turning capability and direct influence on the boundary layers. As a result, rotor losses increased because of changes to the blade's leading edge, trailing edge, blade thickness and blade tip-to-casing clearance. This paper presents an erosion process model based on a simulation of the three-dimensional turbomachinery turbulent flow field, coupled with a prediction of transporting entrained particles and their impact on the blade surfaces in a highly-loaded fan rotor. The erosion model is embedded into an in-house computational fluid dynamics (CFD) solver using the finite element method (FEM) formulation. The authors propose an improved version of the Particle Cloud Tracking (PCT) model which accounts for the particle-blade interactions', non-isotropic effects. The authors implemented PCT using an original finite element based tracking scheme to identify the particle cloud centre's position and that of the computational cells within the cloud. The authors used the PCT technique to investigate the erosion pattern in a highly loaded axial flow fan. The numerical study focuses on the prediction of critical blade areas and erosion rate, together with an insight into the particle dynamics.