Auteur(s): Sébastien Cantin, François Morency, François Garnier
Date de la conférence: Mai 2019
Conférence: CASI AERO 2019, Laval, QC, Canada
Aircraft induced cirrus from contrails are known to contribute to the global radiative forcing. The physical processes affecting ice crystals in the contrail formation stage must be well understood and quantified. Understanding these processes is crucial to model and predict initial aircraft induced cirrus properties. By taking into account that the next generation of civil large turbofan engines will be designed for greater bypass ratios when compared to contemporary architectures, it may be helpful to compare the formation of ice crystals of these architectures. In this context, the objective of the present study is to compare the formation of ice crystals in a propellant jet from two aircraft engines: a modern engine (a LEAP-1A with a by-pass ratio of 10) and an old engine (a CFM56-7A with a by-pass ratio of 5). To achieve this, the geometry and the mesh of both engine aircraft are generated with the aid of ICEM-CFD. Then, three-dimensional Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations of contrails produced by aircraft engine are performed with the commercial software STAR-CCM+. A chemical and a microphysic model implemented in the commercial software are coupled to simulate ice particle growth using a Lagrangian approach. The implemented microphysic model can simulate water condensation onto soot particles, taking into account their activation by adsorption of sulfur species. A validation test case is used to determine the software’s ability to model the jet dynamics, and also to compare the result of three turbulence models on the jet dynamics. The obtained results for the simulation of the aircraft engine show that the crystal growth is faster for the LEAP-1A. The dilution is also faster for the LEAP-1A. However, the number of ice crystal formed is higher for the CFM56-7A because of the greater number of soot particles initially loaded in the engine core flow.
