Numerical Simulation of Aircraft and Variable-Pitch Propeller Icing with Explicit Coupling

A 3D CFD methodology is presented to simulate ice build-up on propeller blades exposed to known icing conditions in flight, with automatic blade pitch variation at constant RPM to maintain the desired thrust. One blade of a six-blade propeller and a 70-passenger twin-engine turboprop are analyzed as stand-alone components in a multi-shot quasi-steady icing simulation. The thrust that must be generated by the propellers is obtained from the drag computed on the aircraft. The flight conditions are typical for a 70-passenger twin-engine turboprop in a holding pattern in Appendix C icing conditions: 190 kts at an altitude of 6,000 ft. The rotation rate remains constant at 850 rpm, a typical operating condition for this flight envelope. Two icing conditions are simulated: air static temperature -23 °C, LWC 0.2 g/m³ and MVD 20 microns resulting in rime ice, and air static temperature -16 °C, LWC 0.3 g/m³ and MVD 20 microns resulting in mixed ice with rime to glaze transition in the radial direction. The ice shapes in both conditions are assumed to remain intact and attached to the blade, based on a predictive ice shedding calculation carried out a priori. The iced geometries are automatically remeshed at each shot using ANSYS FENSAP-ICE and Fluent Meshing tools. Solutions for the 2-meter blade are computed in a periodic domain to reduce computational costs. The pitch variation is a fully-automated process for each icing shot that uses an iterative Newton search on the blade position to converge the thrust to 0.1% of the target value.