Numerical Study of One Air Fired and Two

A computational fluid dynamics (CFD) modeling study has been carried out to investigate gaseous fuel combustion, focusing on chemical reactions, radiative heat transfer, and turbulence in a 100 kW rough-tube firing unit. The study examined one air-fired and two oxy-fuel combustion cases (OF21 with 21 vol % O2 and OF27 with 27 vol % O2). A swirl injection system was employed to stabilize the flame of the turbulent non-premixed combustible gases, utilizing a modified eddy breakup (EBU) model with empirical coefficients tailored for propane combustion. Results indicated that the CFD outcomes closely aligned with measured data, specifically temperature distributions and species concentrations (CO, CO2, and O2) at critical combustion zones. The luminous characteristics and temperature levels of the OF27 flame were similar to the reference air-fired flame, attributed to reduced volumetric flow and increased oxygen concentration. Notably, carbon dioxide levels in both oxy-fuel scenarios were approximately eight times higher than in air-fired conditions. The multi-step reaction mechanism yielded improved agreement, most notably in the flame zone, and demonstrated lower CO concentrations in the OF21 case. The findings form a basis for future studies on combustion behavior in large-scale furnaces under oxy-fuel conditions.