Icing is due to the presence in the atmosphere of super-cooled water droplets which freeze when coming into contact with a solid surface. In very cold temperature (typically less than -20°C), the water freezes almost completely and the ice formed in such a case is referred to as rime ice. When they freeze, super-cooled water droplets release a important amount of heat (the latent heat of melting) which in turn can limit the further freezing process. In very cold conditions, the cooling due to the external air flow is high enough to extract almost all the latent heat, hence the water can freeze almost completely and produce rime ice.
Rime ice can be considered to have a little or no water on its surface. Rime ice shapes are generally quite well predicted by existing icing tools. However, for temperature close to freezing (between -10°C and 0°C), a significant part of the water coming onto the surface does not freeze and there is a combination of ice and water. The ice formed in such a case is referred to as glaze ice. Since the presence of a thin liquid film on the ice surface influences any further ice formation, glaze ice often leads to complex ice shapes. Hence the prediction of glaze ice shapes is still a challenging problem.
The objective of WP4 is to improve the capability of simulation tools for the prediction of ice accretion with runback phenomena due to glaze ice conditions or activation of the thermal IPS, with an accuracy of 20%, thanks to the development of more realistic models than existing ones and validation based on tests representative of the engine environment enabling to achieve TRL5 at the end of the project.
Two modeling strategies will be followed. The first one will consist of extending the classical Messinger model by introducing a more accurate description of liquid film phenomena (improved sub-models for the film dynamics, droplet re-emission, etc).The second one will go further by using a two-layer model based on the coupling between a first set of equations for the liquid film behavior and a second system of equations for the accreted ice layer. This kind of approach provides a natural framework for introducing more physics in the modeling of film phenomena.
Two innovative experiments will also be performed in order to improve the physical knowledge, feed the model development and provide a database for validations.
Rime Ice formation on the spinner
Glaze Ice formation on stator blades