Investigation of airflow thermal ice melting process under various flight conditions

Abstract

The challenge of preventing and removing ice from exposed regions of aircraft is a significant engineering concern. Understanding the melting process of ice due to aerodynamic heating during flight is essential for developing UAV flight strategies in icy conditions. This paper analyzes the heat transfer mechanisms involved in airflow over ice and introduces a theoretical model to estimate the ice melting rate, using principles of turbulent heat transfer at the stagnation point. The study also discusses the impact of environmental conditions on ice melting rates. Findings indicate that the melting speed of the ice surface exhibits a negative linear correlation with the initial temperature of the ice, whereas it shows a nonlinear correlation with airflow velocity and total temperature of the incoming flow. Lower airflow velocity or total temperature of the incoming flow enhances the sensitivity of ice melting speed to changes. Additionally, lower ice density results in a higher melting speed, showing an exponential relationship with factors like average droplet diameter, airflow velocity, and airfoil leading edge diameter in the cloud field during icing. Experiments conducted using a small jet test bench and an icing wind tunnel confirmed the impact of varying conditions on ice melting rates. The deviation between experimental results and theoretical predictions was under 5 %. These conclusions offer valuable insights for flight safety planning of unprotected iced aircraft in challenging environments.