Ingestion characteristics of ice slab shed from the lip of a branched turboprop inlet

Ice shedding from the lip of an engine inlet poses a severe risk to turboprop aircraft, causing engine ingestion, degraded flow field quality and even engine failure. In this paper, an unsteady CFD simulation approach incorporating the rotating propeller and the dynamic motion of an ice slab within a branched inlet has been developed using the overset mesh technique and the six-Degree-of-Freedom (6-DOF) motion theory. Using this approach, the trajectory characteristics of an ice slab shed from the lip of the inlet and the interaction between the ice slab and the internal airflow of the inlet are investigated. Furthermore, low-speed wind tunnel experiments were conducted to assess the ice exclusion efficiency of a branched inlet. The results indicate that the ice slab shed from the lower lip undergoes a more complex motion and a longer exclusion duration than that from the upper lip. Ice shed from the lower lip not only rolls around the z-axis but also experiences a roll angle of more than 180° around the x-axis, posing a greater engine threat. Ingestion of the detached ice yields a complex flow field, degrading the inlet performance with the total pressure recovery coefficient σ reduced to 0.953 for the lower-lip ice and 0.942 for the upper-lip ice. The ice slab shed from the lower lip has a higher probability of entry into the engine duct than that from the upper lip. The trajectory of ice slab is highly dependent on the Mach number of the inlet and the initial attitude angle of the ice slab.