Qualification of Ice Accretion Characteristics on a Wind Turbine Blade Model at High Liquid Water Content Levels Pertinent to Offshore Wind Turbine Icing Phenomena

Abstract

Onshore and Offshore Wind Turbines installed in cold climates experience are subject to icing conditions regularly. The objective of this study is to replicate the conditions experienced by Offshore Wind Turbines in cold climates that are prone to icing events involving high Liquid Water Contents (LWC) and to study the icing physics surrounding this phenomenon. In the present study, an experimental investigation is performed in the Icing Research Tunnel available at the Iowa State University (ISU-IRT) to study the dynamic ice accretion process over a Wind Turbine blade model for high Liquid Water Content (LWC) values. Four cases were tested for Glaze and Rime ice conditions each, at LWC = 0.5 g/m3, 1.0 g/m3, 2.0 g/m3, and 4.0 g/m3 with a runtime of t = 600s, 300s, 150s, and 75s respectively to keep the total amount of accreted ice constant. The test cases were performed at a temperature of T = -5℃ for Glaze Ice and T = -15℃ for Rime ice. A high-speed imaging camera was used to capture the time evolution of the ice accretion process for each case. Runback towards the trailing edge is observed for the Glaze Ice condition along with the formation of rivulet structures, while most of the ice accretion happens around the leading edge for the Rime Ice condition. The qualification of the ice accretion characteristics for each case was done by performing a 3D scan of the iced wind turbine blade model. Various 2D cross-sections were then extracted from the 3D object to compare the ice characteristics along the spanwise length. Following that, the Maximum Combined Cross Section (MCCS) was calculated and compared for each case to understand the change in the accreted ice shape in relation to the LWC. The leading-edge ice thickness was found to decrease with an increase in the LWC, except for the condition of Rime Ice at LWC = 4.0 g/m3.