Biogas Laminar Burning Velocity and Flammability Characteristics in Spark Ignited Premix Combustion

Anggono, Willyanto and Wardana, ING and Lawes, M and Hughes, KJ and Wahyudi, Slamet and Hamidi, Nurkholis and Hayakawa, Akihiro (2013) Biogas Laminar Burning Velocity and Flammability Characteristics in Spark Ignited Premix Combustion. Journal ofPhysics:ConferenceSeries 423 (2013) 012015, 423. ISSN ISSN 1742-6596

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Abstract

Spherically expanding flames propagating at constant pressure were employed to determine the laminar burning velocity and flammability characteristics of biogas-air mixtures in premixed combustion to uncover the fundamental flame propagation characteristics of a new alternative and renewable fuel. The results are compared with those from a methane-air flame. Biogas is a sustainable and renewable fuel that is produced in digestion facilities. The composition of biogas discussed in this paper consists of 66.4 methane, 30.6 carbon dioxide and 3 nitrogen. Burning velocity was measured at various equivalence ratios (ϕ) using a photographic technique in a high pressure fan-stirred bomb, the initial condition being at room temperature and atmospheric pressure. The flame for methane–air mixtures propagates from ϕ=0.6 till ϕ=1.3. The flame at ϕ≥1.4 does not propagate because the combustion reaction is quenched by the larger mass of fuel. At ϕ≤0.5, it does not propagate as well since the heat of reaction is insufficient to burn the mixtures. The flame for biogas–air mixtures propagates in a narrower range, that is from ϕ=0.6 to ϕ=1.2. Different from the methane flame, the biogas flame does not propagate at ϕ≥1.3 because the heat absorbed by inhibitors strengthens the quenching effect by the larger mass of fuel. As in the methane flame, the biogas flame at ϕ≤0.5 does not propagate. This shows that the effect of inhibitors in extremely lean mixtures is small. Compared to a methane-air mixture, the flammability characteristic (flammable region) of biogas becomes narrower in the presence of inhibitors (carbon dioxide and nitrogen) and the presence of inhibitors causes a reduction in the laminar burning velocity. The inhibitor gases work more effectively at rich mixtures because the rich biogas-air mixtures have a higher fraction of carbon dioxide and nitrogen components compared to the lean biogas-air mixtures.

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