Experimental validation of the hybrid airfoil design procedure for full-scale ice accretion simulation

This paper presents results from the first series of ice accretion tests performed to validate the hybrid airfoil design method of Saeed, et al. The hybrid airfoil design method was developed to facilitate the design of hybrid or subscale airfoils with full-scale leading edges and redesigned aft-sections that exhibit full-scale airfoil water droplet impingement characteristics throughout a given a-range. The formulation is based on the assumption that the leadingedge ice accretion will be the same between the full-scale and hybrid airfoils if droplet cloud properties, droplet impingement, local leading-edge flowfield, model surface geometry, model surface quality, and model surface thermodynamic characteristics are the same. Thus, if ice accretion simulation could be predicted in terms of the droplet impingement characteristics alone, a myriad of issues related to ice accretion scaling could be avoided for tests where leading-edge ice accretion is desired. Hence, the method was used to design a 2-D halfscale hybrid airfoil, with a 20% plain-flap and a 5% upper and 20% lower leading-edge surface of an a scaled down model of a modern business jet wing section, that simulates droplet impingement characteristics of the scaled business jet airfoil, on- and off-design. The 2-D scaled business jet airfoil model and its half-scale hybrid airfoil model were then subjected to icing tests in the NASA Lewis Icing Research Tunnel (IRT). The design as well as the icing test conditions selected for the tests were representative of the conditions the business jet wing section would experience in flight.