Two-Way Flow Coupling in Ice Crystal Icing Simulation

Abstract

Numerous turbofan power-loss events have occurred in high altitude locations in the presence of ice crystals. It is theorized that ice crystals enter the engine core, partially melt in the compressor and then accrete onto stator blade surfaces. This may lead to engine rollback, or shed induced blade damage, surge and/or flameout. The first generation of ice crystal icing predictive models use a single flow field where there is no accretion to calculate particle trajectories and accretion growth rates. Recent work completed at the University of Oxford has created an algorithm to automatically detect the edge of accretion from experimental video data. Using these accretion profiles, numerical simulations were carried out at discrete points in time using a manual meshing process. That work showed that flow field changes caused by a changing accretion profile had significant effects on the collection efficiency of impinging particles, ultimately affecting the mass of accreted ice and its shape. This paper discusses the development of the ICICLE numerical ice crystal icing code to include a fully automated two-way coupling between the accretion profile and flow field solution, to account for these effects. The numerical strategy; geometry redefinition, mesh update and flow field solution are discussed, followed by a comparison to experimental ice accretion of a simple 2D geometry and model predictions with and without flow field updating. The results showed that significant changes in leading edge accretion profiles were numerically predicted when the only the geometry was updated. Further changes then occurred when the flowfield was also updated.

Sticking–Erosion Model for Ice Crystal Icing Using Particle Size Distribution

“…13.d, the experimental accretion profile bends downwards, which is not captured by the prediction. This may be because the leading edge accretion was relatively wet and hence a relatively low stiffness [41]. This can lead to the profile bending downwards under the aerodynamic load, which is not accounted for in the ICICLE.…”

ICICLE: A Model for Glaciated & amp; Mixed Phase Icing for Application to Aircraft Engines

“…Surface smoothing is typically required to aid mesh creation, and any gain in prediction accuracy is offset against an increased computational cost. The efficacy of this method is discussed in full in a companion paper [17]. An iterative two-way coupling of energy and mass is also implemented.…”

“…This is due to the profile edge being approximately aligned with the axial direction, maximising erosive efficiency and minimising collection efficiency. It is demonstrated in [17] that the agreement may be improved by re-calculating the flowfield and particle trajectories at discrete points during the test. The new thermodynamic accretion model (EMM-C) also produces an estimate for the thickness of any internal water layer between the solid accretion and the test article.…”