An asymptotic assessment of non-premixed flames fed with porous biomass particles in counter-flow configuration considering the effects of thermal radiation and thermophoresis

[Display omitted] •An advanced asymptotic study of counter-flow non-premixed flames is performed.•Preheat, drying, vaporization, reaction and oxidizer zones are mathematically analyzed.•Mass and energy conservation equations are analytically solved in each zone.•Flame propagation through the mixture of micro-organic fuel particles and air is studied.•The effects of thermal radiation, fuel particle porosity and thermophoresis on the flame structure are discussed. In this research, a comprehensive mathematical analysis is conducted to evaluate the effects of thermal radiation, porosity and thermophoresis on combustion characteristics of multi-zone counter-flow non-premixed flames fed with moisty porous biomass particles taking into account non-unity fuel and oxidizer Lewis numbers. Volatile lycopodium particles are the biofuel and gaseous fuel evolving from the vaporization of these particles is considered to be methane. In this model, combustion system is composed of preheat, drying, vaporization, reaction and oxidizer zones. To describe the drying and vaporization processes, an asymptotic concept is applied. In order to model the radiative heat transfer, Mie theory is used. Governing conservation equations of mass and energy are solved using Matlab and Mathematica software. Finally, the influences of fuel and oxidizer Lewis numbers, effective equivalence ratio, particle size and porosity, fuel and oxidizer mass fractions, thermophoresis and critical strain rate on temperature and mass fraction distributions in presence/absence of thermal radiation are studied. Current results are compared with reliable findings from previous reports under the same conditions. Maximum flame temperatures in presence and absence of radiation are found to be 1995 K and 1955 K, respectively. Maximum absolute value of thermophoretic force is found to be 1.44×10-8 N.