Influence de la géométrie de la tuyère sur la formation de trainées de condensation dans le champ proche d’un turboréacteur d’avion

Abstract

Depending on atmospheric conditions, contrails formed in the wake of airplanes can become persistent and lead to cirrus cloud formation. These aircraft induced clouds (AIC) influence the Earth's energy balance and represent a substantial portion of the radiative forcing due to civil aviation. Over the past decades, studies have been conducted to understand contrail formation processes, revealing that mixing significantly affects ice crystal formation. In this context, this thesis aims to investigate the influence of commonly used aft-body geometries in the industry on the microphysical properties of contrails. A numerical Computational Fluid Dynamics (CFD) model is configured to simulate a coaxial jet in the near-field of a LEAP-1A33 engine at cruising altitude. The ambient temperature is 219°K, with a relative humidity of 60%. The gas phase is composed of air and water vapor. An Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach is employed to model the gas phase flow. Residual soot particles from combustion act as condensation nuclei for water vapor in the plume and ambient air. These are modeled as passive particles using a Lagrangian approach. Ice crystal growth is modeled using the Fukuta and Walter model, implemented in the commercial code STAR-CCM+. Two parametric studies were conducted to quantify the influence of geometric parameters of chevrons (position on the nozzle, number, and penetration angle) and forced mixers (number and lobe height) on the aerothermodynamic properties of the jet and microphysical properties of contrails. The results show that chevrons do not sufficiently disturb the internal mixing of the plume to observe significant differences in microphysical properties, regardless of their position, number, and penetration angle. On the other hand, lobed mixers exhibit a strong impact on the mixing and temperature diffusion of the jet. Consequently, lobed configurations result in a significantly larger mean ice crystal radius (+60%). The parametric study indicates that reducing the number of lobes tends to accentuate these differences. However, varying the height of the lobes does not show a notable impact on crystal radii.

Date	19 Oct 2023
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	François Garnier (Supervisor)