Analytical development of a model for counter-flow non-premixed flames with volatile biofuel particles considering drying and vaporization zones with finite thicknesses

摘要

Non-premixed flames are extensively used in different industrial combustion systems such as gas turbines and coal furnaces. Therefore, reliable theoretical modelling of these flames is indispensable. The purpose of this study is to develop a comprehensive analytical model for counter-flow non-premixed flames employing volatile biomass particles as the fuel. In order to present a promising and accurate analysis for the flame structure and propagation, preheat, drying, vaporization, reaction and oxidizer zones are presumed. In the current analytical modelling, a non-asymptotic approach is used. In this regard, finite thicknesses are considered for the drying and vaporization zones. Lycopodium particles and air are taken as the biofuel and oxidizer, respectively. It is assumed that the gaseous fuel yielded from lycopodium particles is methane. Dimensionless parameters are defined and then non-dimensionalized forms of governing equations including mass and energy conservation equations are derived taking into account appropriate boundary and jump conditions for each zone. The equations are solved by Mathematica and Matlab software. Eventually, the impacts of fuel and oxidizer Lewis numbers, mass particle concentration parameter, equivalence ratio, lycopodium initial temperature on the flow strain rate, flame temperature, flame position and gaseous fuel and oxidizer mass fractions are elaborately examined.