A thermodynamic model for ice crystal accretion in aircraft engines: EMM-C

Abstract

Ingestion of high-altitude ice particles can be hazardous to aircraft engines in flight. Ice accretion may occur in the compression system, leading to blockage of the core gas path, blade damage and/or engine flameout. Numerous engine powerloss events since 1990 have been attributed to this mechanism. An expansion in engine certification requirements to incorporate ice crystal conditions has spurred efforts to develop analytical models for phenomenon. A necessary component of a complete icing simulation is a thermodynamic accretion model. In this paper, a new model for ice crystal icing is developed through adaptation of the Extended Messinger Model (EMM) from supercooled water conditions to mixed phase conditions (ice crystals and supercooled water). The new model is termed the Extended Messinger Model -Crystals (EMM-C). Continuity and energy balances are performed using the local flow conditions and impinging mass fluxes of ice and water. For accretions grown on a warm engine surface, initially above freezing temperature, a novel three-layer (water-ice-water) accretion structure is proposed, and the underlying equations described. Finally, predictions from the EMM-C model are compared to experimental results generated in an ice crystal wind tunnel. Compared with current literature icing models, EMM-C provides a tractable framework for modelling engine icing through allowing mixed phase accretions on warm surfaces.