Characteristics of Runback Ice Accretions on Airfoils and Their Aerodynamic Effects
Edward A. Whalen, Andy P. Broeren, and Michael B. Bragg
University of Illinois, Urbana, Illinois, 61801
and
Sam Lee
NASA Glenn Research Center at Lewis Field, Cleveland, OH
ABSTRACT
The initial results of a research program to investigate runback ice accretions due
to hot-air ice protection systems, scaling of external flow parameters for testing thermal systems and the resulting
aerodynamic effects are presented. The scaling of external flow parameters for testing thermal anti-icing systems in
icing tunnel investigations was developed and tested. An icing tunnel test was conducted at the NASA Glenn Icing Research
Tunnel to evaluate three scaling methods developed to match thermodynamic and droplet impingement parameters. A typical
business jet wing section with a hot-air anti-icing system was used for the test. Data collected from the test included
surface temperatures (using both thermocouples and an IR camera), photographs, high definition video, tracings and molds.
Results of the scaling analysis showed that a useful and qualitatively accurate scaling method was developed for scaling
thermal anti-icing systems for ground testing. However, further development and investigation of the method and governing
equations is required, including generating full-scale runback ice accretions for quantitative evaluation of the scaling
methods. A wind tunnel test was also conducted to evaluate the aerodynamic performance effects of simulated ice shapes
based on the shapes observed in the icing tunnel test. Aerodynamic testing revealed significant aerodynamic penalties
for all flight conditions tested.