Low Ice Adhesion Strength Coated Rotor Blades and the Effects of Surface Temperature on Ice Shedding

A study into the effectsof a low ice adhesion strengthcoatingand combinedlowpower thermal heater systemwas conducted.Preliminarytestsdeterminedthe mass of ice necessaryto shedfromthe lowice adhesion strength coating at a specific ambient temperature (-4°C, -8°C, -12°C, and-16°C). The heater tests were conducted at an ambient temperature of -20°C,wherethe samemass of ice was accreted for each specific case temperature.With theaccreted mass,the heaters wereturned onuntil a shed event occurred.The surfacetemperature at theshedeventwas recorded. For colder temperatures suchas -12°Cand-16°C,the surface needed to reacha temperature within 1°Cof -12°Cand-16°C,respectively,to initiatea shed event.For the warmer cases the replicationof ice at -20°Cwas not feasible,as the type of ice influences adhesionstrength.Ice accretedat -20°Chas differentphysical properties than iceformedat warmtemperatures,therefore thesurface temperature required for shedding did not match between the two tests. Results fromtheheater testsled toa discoveryof a valuethat describes theadhesionstrengthnormalizedwith respect to shed surfacetemperature.The valuewas found to be -1.09psi/°C,averaged oversix cases withvaryingconditions. This value is dependent upon a wide range of adhesion strength values for the systembut opens possibilities of a full understandingof the hybrid thermal/passivecoatingsystem.With the experimentalcharacterization of the adhesion strengthtoshedsurfacetemperaturevalue,futurecoatingdevelopmentcouldrelyonheatingthesurfaceandrecording the surface temperature needed for shedding. With such value, the ice adhesion strength of the coating could be characterized without the need for ice adhesion strength measurements.