Correlation of icing relationships with airfoil and rotorcraft icingdata

Abstract

A high-speed icing wind tunnel test program was conducted to measure the ice growth and performance degradation on 10 rotorcraft airfoil models for ranges of liquid-water content, temperature, and Mach number at several steady and unsteady angles of attack. Prior to these tests, airfoil icing data had been acquired only in low-speed tunnels or during flight testing, but high-speed data are necessary for the prediction of icing on rotors. The test explored the boundaries for the onset of icing and between glaze and rime ice. Ice shapes were documented and lift, drag, and pitching moment were measured. Airfoil lift was reduced slightly at low angles of attack and about 20% at high angles. Drag increased in moderate icing at low angles of attack by a factor of three to four, increasing for higher liquid-water contents and angles above 6 deg. The effect of Mach number varied. Airfoil oscillation did not change the lift loss, but did reduce the drag penalty. Two-dimensional airfoil icing relationships for ice thickness and for changes in lift, drag, and pitching moment coefficients were formulated, with improved accuracy over prior relationships. These relationships have been used to predict aircraft power changes during icing. 7A Pi T Nomenclature = air foil chord, m = drag coefficient = lift coefficient = pitching moment coefficient = droplet diameter, /mi = total airfoil collection efficiency = roughness height-to-chord ratio = modified inertia parameter = empirical constants = ice height, m = ice adhesion width (interior ice thickness), m = freestream Mach number = airfoil leading-edge radius-to-chord ratio = ice thickness, m = airfoil thickness-to-chord ratio = corrected temperature, °C = glaze ice boundary static temperature (r glaze ), °C = onset of ice static temperature, °C = rime ice boundary static temperature, °C = static temperature, °C = local velocity, m/s (ft/s) = helicopter forward flight speed, km/h (knots) = liquid water content, g/m 3 = airfoil angle of attack, deg = ratio of specific heats = incremental quantity = ice density, kg/m = icing time, s = corrected icing time, s Presented as Paper 85-0337 at

Scaled ice accretion experiments on a rotating wind turbine blade

“…A wealth of literature on airfoil performance degradation under aircraft icing conditions is available (Flemming and Lednicer, 1986;Reinert and Aubert, 2011;Han et al, 2011). An equivalent database is required but to date does not exist for wind turbines under representative atmospheric ground icing conditions.…”

“…Controlled environments such as icing wind tunnels have provided ice shapes on generic airfoils which have been correlated to 2D ice prediction codes (Shin et al, 1994). A very limited number of experiments have been performed on a rotating test stand (for example, Flemming and Lednicer, 1986). Test data on torque increase are not available from stationary icing wind tunnel tests.…”

Prediction of ice accretion and performance degradation of HAWT in cold climates

“…The correlations were proposed to predict drag increment due to artificial rime and glaze icing. Correlation for lift coefficient is given by Flemming et al [28].…”

Helicopter flight characteristics in icing conditions

“…When, T C < 0ºC ice accretion occurs on the rotor blade. And as T C decreases from zero to T C GL to T C R ,and then to the temperature that even lower than T C R , the accreted ice shape on the outer portion of the rotor blade changes from beak to glaze to mixed, and to rime ice (24) . The glaze and rime ice boundary atmospheric temperature (8) on the blade surface are So combining with formula (1), (2), and (3), T C GL and T C R can be further deduced as…”

“…Corresponding ΔC L and ΔC D of the rime and glaze/beak ice can be calculated by using the empirical correlation of Flemming (24) . And the empirical correlation of the mixed ice can be conducted as referred to in Ref.…”