An Experimental Investigation on the Unsteady Heat Transfer Process Over an Ice Accreting NACA 0012 Airfoil

Abstract

The in-flight ice formation and accretion are highly dependent on weather conditions that essentially affect the heat transfer capability. When the temperature is sufficiently cold, the heat transfer is adequate to remove all of the latent heat from the collected water. The rate of rime ice accretion is controlled by the droplet collection efficiency. Otherwise, when the heat transfer is inadequate to remove all of the latent heat in collected water, the rate of glaze ice accretion is essentially controlled by the local convective heat transfer, which determines the amount of latent heat removal from the collected water. To better understand the physical details during an ice accretion process, time resolved heat transfer information is important and strongly desired. In this study, a methodology based on infrared thermography was developed to achieve nonintrusive measurements of unsteady heat transfer process over an ice accreting NACA 0012 airfoil. Comprehensive 2-D surface temperature distribution measurements under various icing conditions (e.g. air temperature, liquid water content, and wind speed) were performed in an icing wind tunnel. A heat balance model was formulated based on the current measurement model. The dynamic surface temperature distribution variations were characterized based on the measurements. The temperature variation history at different chordwise positions during ice accretion process was fully recorded and illustrated. Based on the temperature variation history along the airfoil surface, the heat transfer evolution in chordwise direction was evaluated. Finally, The effects of the liquid water content on the heat transfer process were elucidated based on the measurement results.