Experimental investigations on dynamic ice accretion and unsteady heat transfer pertinent to aero-engine icing phenomena
Aircraft icing is a well-known weather hazard to flight safety and performance. While ice accretion over airframe surfaces due to airborne supercooled water droplets has been investigated extensively over the past decades, ice accretion caused by the inhaled ice crystals in the clouds impacting onto hot components of aero-engines has also been found to be a major risk to the safe operation of aero-engines and has received increasing attention in recent years. In the present study, comprehensive experimental studies were conducted to investigate the transient ice accretion process and unsteady heat transfer characteristics associated with the dynamic impingements of ice crystals onto hot surfaces in order to elucidate the underlying physics pertinent to aero-engine icing phenomena due to inhaled ice crystals. A multiple-function wind tunnel was developed and fitted into a temperature-controlled test chamber in order to perform the experimental investigation to study the ice crystal icing phenomena. An experimental campaign was conducted to quantify the dynamic ice accretion process and unsteady heat transfer characteristics upon the impingement of ice crystals onto hot test plates, in comparison to those with supercooled water droplets impinging onto cold test surfaces. During the experiments, while a high-speed imaging system was used to record the transient ice accretion process, a high-speed infrared (IR) thermal imaging system was used to map the temperature distributions over the test surfaces to quantify the unsteady heat transfer characteristics. A high-sensitive force transducer and a high-speed imaging system were also utilized to reveal the differences in the impacting characteristics of single water droplets, supercooled droplets, and ice crystals onto the same test plates. By leveraging the unique Icing Research Tunnel (IRT-ISU), a systematic study was performed to examine the dynamic ice accretion process over the surfaces of an aero-engine Inlet-Guide-Vane (IGV) and Pitot Probes under various testing conditions. A novel hybrid anti-/de-icing strategy by integrating icephobic coating and minimized surface heating was also explored to prevent ice accretion over the entire surface of the Pitot probe with much less power consumption in comparison to conventional surface heating methods. The research findings derived from the present study can lead to a better understanding of the underlying icing physics pertinent to aircraft/aero-engine icing phenomena, which is essential for the development of more effective and robust strategies to ensure safer operation of aircraft/aero-engines in cold climates.