NUAGE

This project falls within the framework of aviation security related to icing. Recent serious events related to icing with the presence of droplets with diameter between 50 microns and 1 millimetre lead to the modification of the regulation for aircraft certification. In order to deal with these new demands in terms of certification, we saw the emergence of European projects such as WEZARD or EXTICE in which new wind tunnel capabilities where developed in icing conditions. However, even if those capabilities are now fully operational, it is not certain that the reproduced icing conditions are fully controlled until specific parameters such as the supercooled droplets temperature or local hygrometry are checked and measured. Furthermore, it is necessary to check that the droplets are really over icing and to evaluate the presence of ice in the droplets. To date and to our knowledge, there is no reference experiment to deal with those three parameters. Thus, this project aims to develop, from existing techniques, new experimental diagnostics to measure supercooled droplets temperature, the fraction of ice within the droplet and the hydrometry with the presence of droplets, in icing aeronautical conditions. These conditions involve droplets having velocities up to about 250 m/s and diameter of several millimetres. Therefore, this ambitious project will be carry out via a partnership gathering together four labs (LEMTA from the Université de Lorraine, DGA Essais Propulseurs in Saclay, IRSTEA in Antony and CORIA in Rouen), each lab bringing its own expertise. Taking into account that icing aeronautical conditions are an extreme environment, this project is split in two work-packages. The first work-package is dedicated to the development of all the measurements techniques leading to characterize supercooled droplets having velocity and diameter of about 10 m/s and 300 µm respectively. The second work-package constitutes the main output of the project since the goal is to apply the previous improved measurements techniques under aeronautical conditions (velocity of about 150 m/s in maximum). In parallel, a transverse numerical activity will be undertaken in order to bring assistance for several expected steps in both work-packages. The first work-package is divided in three parts. The first one is devoted to the development of an experimental set-up (Experiment 1) to allow the generation of supercooled droplets at lower velocity (about10 m/s). For the second part, the experimental techniques for the measure of the droplet temperature, the fraction of ice within the droplet and the hygrometry will be set-up. The second work-package will be conducted also in two parts. In a first part, a small size dynamic wind tunnel will be developed (Experiment 2) to generate supercooled droplets at high speeds. Then, Experiment 2 will be used to undertake an experimental campaign in order to characterise the over melted droplets (temperature and ice fraction). On top of this, the project is also intending to provide a sufficient level of maturity for measurement techniques which could be used on one side for the normalisation work of the Society of Automotive Engineers (SAE) (Calibration methods for icing plants) and on the other side for a potential involvement in future European projects to complement EXTICE.