Gas turbine engines operating in a hostile environment, polluted with sand or dust particles, are susceptible to the erosion damage, mostly at front axial fans and compressors. To accurately predict the erosion pattern and rate due to sand ingestion is one of the big challenges faced by the transportation and power industries. Maintenance costs are scrutinized and intensive research efforts are currently deployed in predictive life assessment tools to minimize the overhaul down time. The conventional prediction methods were usually based on steady-state simulations of gas-phase flows through a single blade passage per blade row to reduce computational cost. However, the multi-stage turbomachinery flows are intrinsically subject to unsteadiness, especially due to statorrotor interactions which may affect sand particle trajectories even if a one-way coupling method is considered. Furthermore, an unsteady stator-rotor interaction asks for a whole-annulus model at great computational cost to avoid simplifications of geometries or flow physics. To study the effects of the stator-rotor interaction on sand particle trajectories and erosion, an axial fan with inlet guide vanes is investigated based on the whole annulus computations of both steady and unsteady gasphase flows, each of which is then followed by a Lagrangian particle tracking step. A numerical algorithm for tracking particles driven by unsteady gas-phase flow is presented. The comparison of the numerical predictions with the experimental data confirms the validity and necessity of the unsteady CFD model in providing adequate predictions of sand erosion in the axial fan.

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