Effects of Burner Configuration on the Characteristics of Biogas Flameless Combustion

The purpose of this experimental and numerical investigation is to analyze the effects of burner configuration on the characteristics of biogas flameless combustion. In the four non-premixed studied burners, the inlet jet of the fuel is located at the center of the burner, surrounded by four oxidizer parallel jets in the coaxial burners and four perpendicular jets in the tangential configuration. In the three-dimensional (3D) computational fluid dynamic (CFD) study, a two-step reaction scheme, eddy dissipation concept (EDC), eddy dissipation method (EDM), and the realizable k- ϵ formulation were set for all simulations. The results illustrate that the volume of the flame is wider in a tangential burner and, hence, the temperature uniformity in the tangential flameless burner is more than coaxial configurations. The inside temperature of the furnace and the combustor's wall temperature are higher in the tangential burner; consequently, higher heat loss from walls was recorded in tangential mode. Despite the higher energy loss from walls in the tangential burner, the efficiency of biogas flameless combustion in the tangential is more than the coaxial burners (66% and 64%, respectively). The concentration of CH4 in the exhaust gases was recorded at 48 ppm and 60 ppm in the tangential and coaxial burners, respectively, which confirms that the combustion of biogas is more complete in the tangential flameless burner. The lower concentration of oxygen in the tangential burner conducts the combustion system to generate higher carbon monoxide (CO) based on the two-step combustion concept.