Experimental Investigation on Ice Accretion Upon Ice Particle Impacting onto Heated Surface

Abstract

An experimental study was conducted to examine the dynamic ice accretion process upon the impingement of microsized, airborne ice particles/crystals onto a heated test surface pertinent to aeroengine icing phenomena. The experimental study was conducted in a specially designed ice crystal icing test facility to generate and inject microsized ice particles into a frozen-cold airflow. The microsized ice particles were forced to impinge onto a heated test plate with controllable surface temperatures. Upon impingement of the ice particles onto the heated test surface, the dynamic ice accretion process was found to take place over the heated surface in three distinct stages: 1) an ice-melting stage at the beginning, followed by 2) an ice/water mixture formation stage, and then 3) a water refreezing stage, causing the formation of a solid ice layer accreted on the heated test surface eventually. After impinging onto the test plate, while small ice particles with spheric shapes were found to be more ready to bounce off from the test surface, large, nonspheric-shaped ice particles experienced a catastrophic fragmentation process and break up into smaller pieces with noticeable impingement residues remaining on the test surface. The formation of a liquid water film layer on the test surface due to the melting of the impinged ice particles was found to be very beneficial to make more impinged ice particles stay sticking on the test surface, resulting in a rapid growth of the water/ice layer accreted on the heated test surface. A comprehensive theoretical analysis was also performed to examine the unsteady heat transfer characteristics during the dynamic ice accretion process. The theoretic predictions of the collection efficiency of the impinged ice particles on the heated test surface and the temperature variations of the water layer at the initial ice-melting stage were found to agree well with the experimental measurement results.