Numerical simulations of biogas flames using OpenFOAM

• Main Authors: Kumar, R. Nivethana, Raghavan, V.
• Format: Conference Proceeding
• Language: English
• Subjects: Biogas; Carbon; Chemical reactions; Composition effects; Computational fluid dynamics; Diffusion; Dioxides; Fermentation; Flame stability; Flame structure; Flame temperature; Fuels; Heat loss; Household wastes; Industrial applications; Mathematical models; Numerical models; Power rating; Radiation; Reaction kinetics; Simulation; Source code
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0071011

Biogas is a renewable fuel obtained from the fermentation of animal and food wastes. Usage of biogas as a fuel in domestic and industrial applications has increased in recent times. The disadvantage of biogas is the presence of carbon-dioxide, which varies in the range of 30% to 45% by volume. The stability and burning characteristics of biogas flames strongly depend upon the amount of carbon-dioxide present and these aspects should be understood thoroughly. Numerical simulations of biogas flames reveal flow, temperature and species fields, which are important to understand the flame characteristics. The present work focuses on detailed numerical study of non-premixed biogas flames along with coflow air stream. Biogases having varying carbon-dioxide content have been studied. A two-dimensional, axisymmetric coflow diffusion flame is considered. A chemical kinetics mechanism with 25 species and 121 reactions is used for simulating the reactive flow. The numerical model includes Fick’s diffusion, Soret (thermal) diffusion and an optically thin radiation model to account for radiation heat loss from the flame. The governing equations for conservations of mass, momentum, species and energy are solved using an open-source Computational Fluid Dynamics (CFD) software, OpenFOAM. The effects of carbon-dioxide composition in biogas on the flame structure have been investigated. Flames with a fixed power rating of 0.25 kW are considered. Numerical results are validated against the experimental data available in the literature. Results show a decrease in flame stability with an increase in carbon-dioxide content. The flame temperature reduces and the reaction zone starts moving away from the burner exit, as carbon-dioxide content increases. Flame length also increases. Flame characteristics are described in terms of temperature and species fields and contours of net reaction rates of stable species.