Assessment of aircraft anti-icing ethylene glycolbased fluid ethylene glycol-based performance using thermography approach

Protecting the aircraft surfaces from ground icing in cold weather conditions before takeoff via anti-icing fluids is crucial for flight safety. These fluids offer a specific protection time evaluated through outdoor endurance time testing. As outdoor conditions are difficult to standardize and repeat, there is interest in developing interior tests under simulated snow conditions. This study investigates the impact of snow type on snow-fluid interactions which govern fluid failure mechanisms. Natural snow is compared to fresh and aged artificial snow for ethylene glycol-based anti-icing fluids. Infrared and visual cameras are utilized to monitor a small test plate measuring six by eight centimetres, with a depth of 6 millimetres. This plate serves as the deposition site for snow at regular intervals, adjusted based on the precipitation rate at the center of the plate. The snow is distributed onto the plate via a specially designed deposition system, ensuring a consistent volume over a constant area. Thermography is used to study temperature drops and the rebalancing process under simulated snow precipitations. This work presents two test methodologies: the first considers a single snow deposition for each fluid at different concentrations. The second aims to study fluid saturation by simulating different snow intensities. The snow mass is calculated based on the density measured by the Schnee- und Lawinenforschung (SLF) snow sensor and the known deposited snow volume. The average deposited snow mass is then used to determine the time interval for snow deposition to simulate representative natural precipitation rates. Infrared (IR) thermography results for each snow type (natural, fresh artificial snow, aged artificial snow) are considered. Snow types are characterized by density and liquid water content (LWC). Results show that ethylene-based fluids experienced significant temperature drops and have a characteristic temperature rebalancing process related to the fluid's thermal and diffusion properties. Furthermore, the relationship between the deposited snow mass and the temperature gradient remains consistent irrespective of the snow type as long as the snow mass does not almost reach the saturation threshold. The impact of different snow types is studied and compared for both test procedures to evaluate possible sources of discrepancies between outdoor and indoor fluid snow precipitation endurance testing. This study revealed how the temperature changes, fluid saturation, and failure stages are reached for each studied anti-icing fluid with snow precipitation rate and snow types.