Influence des gouttes d'éthanol sur la propagation d'une flamme laminaire prémélangée

Abstract

The goal of this thesis is to numerically evaluate ethanol droplet’s effect on premixed laminar flame propagation. A simplified numerical model has been developed with COSILAB. This model allows studying freely propagating 1-D premixed biphasic flames at 300 K. The model is coupled to a detailed chemical kinetic scheme for ethanol oxidation and is validated against experimental and numerical results of the literature. A parametric study is then conducted in order to quantify the influence of droplet size, equivalence ratios and initial pressure on flame propagation. The results revealed that the increase in initial droplet diameter and liquid equivalence ratio can cause significant variations of the flame speed. For example, large droplets (larger than 11 μm in diameter)enter the flame because their vaporization is incomplete. This late vaporization induces a decrease in effective equivalence ratio that can have the following impacts : - for lean mixtures, the reactions become less intense and the flame becomes thicker and the flame speed is reduced; - for rich mixtures, the gaseous equivalence ratio approaches the stoichiometric equivalence ratio that leads to more intense reactions, and thinner and faster flames. Increasing the pressure leads to effective equivalence ratios approaching the total equivalence ratios, which promotes vaporization. The two-phase flame behaves like the equivalent gaseous flame. Finally, correlations are proposed enabling predicting biphasic laminar flame speed.

Date	15 Dec 2014
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Patrice Seers (Supervisor)