Effect of Inhibitors on Biogas Laminar Burning Velocity and Flammability Limits in Spark Ignited Premix Combustion

Biogas is the natural byproduct of the decomposition of vegetation or animal manure, of
which there are almost in exhaustable supplies in the world, and which does not contribute CO2 or other
greenhouse gases to global warming or climate change. Biogas contains 66.4% flammable gas (CH4) and
33.6% inhibitors (CO2 and N2). This study focuses on the effects of inhibitors on biogas laminar burning
velocity and flammability limits in spark ignited premix combustion. Spherically expanding laminar
premixed flames, freely propagating from spark ignition sources in initially quiescent biogas–air
mixtures, are continuously recorded by a high-speed digital camera. Initially, all the experiments in this
paper were performed using inhibitorless biogas (biogas without inhibitors) at room temperature, at
reduced pressure (0.5 atm) and at various equivalence ratios (ϕ) from the lower flammable limit to the
upper flammable limit. The results are compared with those from biogas (containing inhibitors) flames at
reduced pressure, inhibitorless biogas flames at atmospheric pressure (1 atm), and biogas flames at
atmospheric pressure to emphasize the effect of inhibitors on biogas laminar burning velocity and
flammability limits. Compared to an inhibitorless biogas-air mixtures, in the biogas-air mixtures, the
presence of inhibitors cause a reduction in the laminar burning velocity and the flammable limits become
narrower.