Snow Effects on the NGCTR Nacelle for Relevant Certification Conditions

This paper is focused on the numerical analysis of the impingement and water catch rate of snow particles on the engine air intake of the Next Generation Civil Tilt Rotor (NGCTR). This NGCTR is developed by Leonardo Helicopters. The collection efficiency and water catch rate for the intake geometry are obtained for the test cases that have been defined for the relevant snow conditions. These conditions are related to the flight envelope of the NGCTR, existing EASA/FAA certification specifications, and the snow characterization. The analyses have been performed for the baseline air intake geometry. A range of particle diameters has been simulated with a particle density equal to the density of ice and with a particle drag relation that disregards the particle shape. Based on the results for the water catch rate on the basic nacelle configuration in snow conditions it is concluded that the ‘cheeks’ of the duct are more susceptible to impingement of larger snow crystals (>75 μm), whereas the ‘chin’ of the duct is more susceptible to impingement of smaller droplets (<75 μm). Additionally, ground operations of the NGCTR are predicted not to be critical for icing by snow crystals primarily due to the perpendicular orientation of the intake plane to the rotor downwash. The assessment of the basic configuration of the NGCTR inlet in snow conditions has shown that the critical area of snow impact exists near the small passage inside the inlet where the duct transitions towards a circular shape.