Effect of Intercycle Ice Accretions on Airfoil Performance
Andy P. Broeren and Michael B. Bragg
University of Illinois, Urbana, Illinois 61801
and
Harold E. Addy, Jr.
NASA Glenn Research Center at Lewis Field, Cleveland, Ohio 44135
ABSTRACT
This paper presents the results of an experimental study
designed to characterize and evaluate the aerodynamic performance penalties
of residual and intercycle ice accretions that result from the cyclic operation
of a typical aircraft deicing system. Icing wind tunnel tests were carried
out on a 36-inch chord NACA 23012 airfoil section equipped with a pneumatic
deicer for several different cloud conditions modeled after FAR 25 Appendix
C. Results from the icing tests showed that the intercycle ice accretions
were much more severe in terms of size and shape than the residual ice accretions.
Molds of selected intercycle ice shapes were made and converted to castings
that were attached to the leading edge of a 36-inch chord NACA 23012 airfoil
model for aerodynamic testing. The aerodynamic testing revealed that the
intercycle ice shapes caused a significant performance degradation. Maximum
lift coefficients were typically reduced about 60% from 1.8 (clean) to 0.7
(iced) and stall angles were reduced from 17 deg. (clean) to 9 deg. (iced).
Changes in the Reynolds number (from 2.0x106 to 10.5x106)
and Mach number (from 0.10 to 0.28) did not significantly affect the iced-airfoil
performance coefficients.