Abstract
The growing demand for sustainable household energy systems has intensified interest in biogas as a renewable substitute for conventional cooking fuels such as liquefied petroleum gas (LPG) and piped natural gas (PNG). Although biogas cookstoves have been widely adopted in rural and semi-urban communities, their thermal performance remains highly dependent on burner geometry and combustion characteristics. This study presents a computational fluid dynamics (CFD) investigation of a domestic biogas cookstove burner to evaluate the influence of burner port diameter on flame structure, temperature distribution, heat transfer behaviour, and thermal efficiency. Four burner port diameters (3.5, 4.0, 4.5, and 5.0 mm) were examined under identical operating conditions, including a fuel flow rate of 4 L min⁻¹, injector diameter of 2.5 mm, loading height of 25 mm, and a standard cooking vessel with an external diameter of 180 mm and height of 100 mm. Numerical simulations were conducted using ANSYS Fluent with the standard k–ε turbulence model, species transport formulation, discrete ordinates radiation model, and a two-step methane combustion mechanism representing biogas containing 48.5% CH₄ and 51.5% CO₂. Performance evaluation followed the water-boiling test procedure specified in Indian Standard IS 8749:2002. Results indicate that maximum flame temperatures occur near burner ports and reach approximately 2400 K before decreasing due to heat transfer and buoyancy-induced flow expansion. The vessel bottom exhibits a dual-peak temperature distribution, with major heat transfer zones located directly above the burner and within the radial distance of 50–80 mm from the burner centre. Burner port diameters of 4.0 mm and 4.5 mm produced comparable thermal behaviour, whereas the 5.0 mm configuration resulted in reduced average temperatures and lower heat transfer rates. The highest thermal efficiency of 61.64% was obtained with the 4.0 mm burner port diameter. The findings demonstrate that burner port diameter moderately influences combustion performance and that optimised port geometry can enhance energy utilisation without increasing fuel consumption. The study contributes to the development of high-efficiency, low-cost biogas cookstoves for sustainable household energy applications.
Keywords: biogas combustion, cookstove burner, Computational fluid dynamics, thermal efficiency, renewable energy, heat transfer, burner optimization