Behavior of Flame Propagation in Biogas Spark Ignited Premix Combustion with Carbon Dioxide Inhibitor

Abstract

Biogas is a mixture of gases which commonly consists of methane (up to 50%) and other inhibitor gases which are dominated by carbon dioxide (up to 50%). Biogas is produced naturally by the decomposition of organic materials such as vegetation or animal manure in the absence of oxygen and it also contributes less greenhouse gases which may lead to global warming or climate change. The presence of carbon dioxide (CO2) in biogas is presumed to have some effects on biogas flame propagation characteristics. This study focuses on the effect of carbon dioxide (CO2) as the biggest inhibitor composition in biogas on flame propagation speed as the important flame propagation characteristic in spark ignited premix combustion. Propagating flames are employed to measure the flame propagation speed as a function of the mixture composition. This parameter was measured using a transparent tube fuel chamber with dimensions of 60 mm inner diameter and 300 mm height based on DIN 51649 standards and recorded by high speed digital photographic technique. The characteristic of biogas-oxygen flames were studied at stoichiometric, room temperature and atmospheric condition from 0% to 50% CO2 biogas inhibitor composition increased by 10% for each experiment. The results showed that the carbon dioxide decreases flame propagation speed of biogas. These indicated that carbon dioxide reduced reaction rate of biogas premixed combustion.

The influence of CO2 in biogas flammability limit and laminar burning velocity in spark ignited premix combustion at various pressures

“…3. As seen from the prior experimental investigations to find the laminar burning velocities [1][2]5,[12][13][14][15][16][17], the laminar burning velocities of biogas-air mixtures premixed combustion has been found for biogas with 50% CO 2 at atmospheric pressure, ambient temperature and various equivalence ratios as shown in Table 2. The fuel (biogas with 25%CO 2 )-air mixtures produced propagating flame at reduced pressure (0.5 atm) for the equivalence ratios of 0.7, 0.8 and 0.9.…”

“…A Spherical spark ignited premixed combustion bomb was used for the biogas combustion research as mentioned in the previous studies [1][2]5,[12][13][14][15][16][17], the combustion bomb is filled with fuel-air mixtures with the various carbon dioxide compositions (25% and 50%) in biogas. All the experiments were conducted at various pressures (atmospheric pressure (1 atm) and reduced pressure (0.5 atm)), various equivalence ratios (from lower flammability limits to upper flammability limits) and ambient temperatures.…”

“…1. The laminar burning velocity of a spherically expanding flame was deduced from the high speed camera images, the procedures to find the laminar burning velocities can be found in the previous studies [1][2]5,[12][13][14][15][16][17].…”

“…Inhibitors are defined as substances that reduce laminar burning velocity [1]. A previous study found that carbon dioxide effects biogas combustion by reducing its flame speed [2].However, the effects of carbon dioxide in biogasflammability limits and laminar burning velocities, as themost important fundamental combustioncharacteristics of the fuel, have notbeen studied yet. Thus, the aim of this paper is to investigate the influence of CO 2 in biogas flammability limits and laminar burning velocities in spark ignited premix combustion at various pressures.…”

“…In addition to biogas use in its internal combustion engines, there has been research into combustion and emissions characteristics for use in dual fuel engines. These dual fuel engines consume two types of fuel, gaseous fuel known as primary fuel and liquid fuel known as pilot fuel and methane, the main component in biogas, produces far lower emissions of NO x when burnt than other hydrocarbon fuels [1,2,5,7,8].…”