ICICLE: A Model for Glaciated and Mixed Phase Icing for Application to Aircraft Engines

High altitude ice crystals can pose a threat to aircraft engine compression and combustion systems. Cases of engine damage, surge and rollback have been recorded in recent years, believed due to ice crystals partially melting and accreting on static surfaces (stators, endwalls and ducting). The increased awareness and understanding of this phenomenon has resulted in the extension of icing certification requirements to include glaciated and mixed phase conditions. Developing semi-empirical models is a cost effective way of enabling certification, and providing simple design rules for next generation engines. A comprehensive ice crystal icing model is presented in this paper, the Ice Crystal Icing ComputationaL Environment (ICICLE). It is modular in design, comprising a baseline code consisting of an axisymmetric or 2D planar flowfield solution, Lagrangian particle tracking, air-particle heat transfer and phase change, and surface interactions (bouncing, fragmentation, sticking). In addition, an efficient particle tracking method has been developed into the code, which employs the representative particle size distribution at each injection location and a deterministic particle sticking method by using an in-situ particle based scaling factor without aborting the particle trajectories. Various time integration algorithms, including implicit and explicit Euler and Runge-Kutta methods, are discussed and the effect on an acceptable timestep investigated. The model then improves on those available in the literature in three ways: firstly, an adaptation of the Extended Messinger Model (EMM) to mixed phase conditions is incorporated, improving the fidelity of the ice accretion prediction compared with the classical Messinger model. Secondly, an experimentally-derived model for sticking efficiency improves the accuracy of the continuity equation in the EMM; thirdly a simple model for integrating two-way coupling of mass and energy is proposed