Effect of Intercycle Ice Accretions on Airfoil Performance

Abstract

Results are presented 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-in. chord NACA 23012 airfoil section equipped with a pneumatic deicer for several different Federal Air Regulation 25 Appendix C cloud conditions. 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-in. 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 2.0 × × 10 6 to 10.5 × × 10 6) and Mach number (from 0.10 to 0.28) did not significantly affect the iced-airfoil performance. Nomenclature C d = drag coefficient C l = lift coefficient C l,max = maximum lift coefficient, coincident with α stall C l,α = lift-curve slope C m = quarter-chord pitching-moment coefficient c = airfoil chord length k = ice-roughness height or thickness M = freestream Mach number Re = Reynolds number based on chord x = chordwise position along airfoil y = normal position from airfoil chord line α = airfoil angle of attack α stall = stalling angle of attack, coincident with C l,max

Aerodynamic Simulation of Runback Ice Accretion

“…Changes in Mach number from 0.10 to 0.28 at Re 12:2 10 6 did have slightly more effect on the icedairfoil performance, with a small increase in drag coefficient over this range. These results are consistent with previous aerodynamic studies of iced airfoils [8,23,[28][29][30][31].…”

A Wind Tunnel Study of Icing Effects on a Business Jet Airfoil

“…The authors also reported similar Mach number trends in maximum lift behavior in the iced airfoil configurations at Re = 6.4×10 6 . More recently, Broeren, et al 21 carried out performance measurements on a NACA 23012 airfoil with intercycle ice castings. In this case there was a slight increase in C l,max (less than 0.05) between Re = 2.0×10 6 and 3.5×10 6 , but no further increase in C l,max up to Re = 10.5×10 6 was observed for all four iced airfoil configurations.…”

Inflight Icing Educational Objectives for Air Carrier Pilots

“…26 The ice shapes tested by Broeren, et.al., in the NASA LTPT were all formed at a zero degree angle of attack in the BF Goodrich icing tunnel. 51 The drag results shown in Figure7 are dramatic. Although these are section drag coefficients, and there are questions regarding scale effects between the 36 inch chord model used in these tests and a full scale wing, the effects of accreting ice at a low angle of attack and then increasing that angle can be seen clearly.…”

“…Broeren, et.al., 51 showed differences in the lift curves for a typical airfoil section, the NACA 23012, when tested at high Reynolds numbers with a variety of intercycle ice shapes and a standard, distributed roughness. Figure 7a shows the results for the intercycle shapes; Figure 7b the results for the sandpaper roughness.…”