Supercooled large droplet icing and hot-air anti-icing performance of a two-dimensional nacelle lip in a large-scale icing wind tunnel

This study conducts comprehensive experimental investigations in a large-scale icing wind tunnel, employing a 1:1 two-dimensional nacelle lip, to compare the icing and anti-icing characteristics of supercooled large droplets (SLDs) with those of small water droplets. The experiments were systematically designed by selecting six icing conditions and six hot-air anti-icing operating points, and the test matrix encompassed a range of median volume droplet diameters from 20 to 206 μm, while maintaining a constant liquid water content of 0.8 g/m3 across all test cases. The results demonstrated that SLDs significantly alter ice accretion characteristics, increasing the nacelle lip maximum ice thickness by 13–14 mm and expanding the ice accumulation range by 35–115 mm for the nacelle leading edge with approximately 230 mm streamwise length during an 800 s icing period. The underlying mechanism lies in SLDs' higher inertia overcoming airflow viscous drag at the stagnation point—preventing entrainment by the surrounding flow and promoting greater liquid adhesion and freezing, as well as the synergistic effects of the droplet splashing and runback. Additionally, SLD conditions reduced the average hot-air anti-icing temperature on the nacelle lip surface by 3.5–3.9 °C, and the most substantial temperature reduction occurred in the pressure side region. This phenomenon occurs because SLDs impacting on the nacelle anti-icing leading edge do not freeze immediately but rather undergo splashing and runback processes, thereby increasing evaporative heat absorption and anti-icing thermal load on the pressure side.