Thermographic analysis of ethylene glycol–based aircraft anti-icing fluid: Investigation of fluid failure mechanisms during simulated snow endurance tests

Abstract

Applying anti-icing fluid is the primary method of protecting aircraft surfaces from freezing precipitation before takeoff. This research's main objective is to deepen our understanding of the fluid failure mechanisms using the infrared thermography technique to observe the snow-fluid interactions. We use a laboratory-scale setup with an optical and infrared camera to study the interaction between artificial snow and anti-icing fluids. The thermal aspects of snow melting upon deposition on an ethylene glycol–based fluid are examined for different ethylene glycol concentrations, snow mass deposits, and temperatures. When the freezing temperature of the water–ethylene glycol mixture is lower than the ambient temperature, deposited snow causes an instant temperature drop, revealing that a fraction of the snow undergoes an instantaneous phase change. Depending on the ethylene glycol concentration, ambient temperature, and snow mass input, the snow-to-water transformation may be total or partial. The magnitude of the temperature drop is proportional to the amount of snow melting and limited by the variation in local fluid concentration resulting from the melting process. As the ethylene glycol concentration decreases and the mixture's freezing point approaches the ambient temperature, the absence of temperature variation indicates that the snow remains solid and that the snow accumulation process is initiated. We demonstrate that the surrounding ambient temperature influences the melting rate. Higher temperature gradients are achieved at an ambient temperature of −5 °C, and the melt rate exhibits sensitivity to the studied snow mass. At −10 °C and −15 °C, temperature gradients due to snow melting are reduced and sensitivity to snow mass becomes negligible for the lowest masses achieved for these tests. This study provides insights into the failure mechanisms of anti-icing fluids. Thermal failure is indicated by the absence of a temperature change after snow deposition, signifying fluid melt saturation.