Methodology to Investigate Ice Crystal Icing in a Rectilinear Compressor Cascade under Relevant Boundary Conditions

Ingestion of high altitude ice particles into jet engines can cause engine power loss, flameout, mechanical damage and compressor instabilities. The detrimental effects on engine performance are attributed to time-dependent ice accretion on initially warmer than freezing surfaces within the engine core gas path. The phenomenon is referred to as ice crystal icing. The complexity of ice accretion physics and the multitude of related mechanisms render the development of strictly theoretical models currently infeasible. The derivation of empirical and physical models has therefore to rely on measurement data obtained for relevant and representative boundary conditions and geometries. Within the scope of this work, a coherent methodology and an experimental setup are developed to investigate ice crystal icing under relevant, engine-realistic, mixed-phase boundary conditions. A rectilinear compressor cascade test rig is designed based on a reference blade row geometry taking into account peculiarities arising from mixed-phase conditions and investigation of ice crystal icing. A numerical fan stage model is used to explore the design space with regard to experimental boundary conditions for prospective cascade experiments. A lower and an upper thermodynamic temperature limit for the occurrence of ice crystal icing is estimated from a limited number of CFD simulations assuming a two-phase flow of initially glaciated particles and air. The insight generated by the CFD simulations is complemented with governing analytic relations for the energy balance of a wetted surface exposed to impingement of glaciated particles. A range of cascade test rig boundary conditions conducive to ice accretion is derived for climb and descent operating regimes. For the first time, a coherent experimental methodology is available which is developed specifically to investigate ice crystal icing under relevant and representative boundary conditions.