Numerical Investigation of the Influence of Burner’s Bluff Body on Air-Fuel Mixing and Reaction

One way to improve air-fuel mixing in a gas diffusion flame is to produce targeted vortices and circulate the flow using a bluff body. In this study, the influences of radius, thickness, and location of a disk-shaped bluff body on the performance of a methane gas diffusion flame are numerically studied. This investigation is carried out under both cold mixing and hot mixing (with combustion reaction) conditions. The present simulation is verified against experimental data. The results show the substantial influence of the mentioned parameters on the size and intensity of downstream vortices, and a direct dependence is observed between the sizes of inner and outer recirculation zones and air-fuel mixing. It is also observed that the flow pattern and level of air-fuel mixing are more dependent on the bluff body’s radius than its thickness. Based on the hot mixing simulation results and regarding the dependence between the rates of the chemical reaction and turbulence mixing, the higher rate of air-fuel mixing is associated with the decreased flame length. Among the cases investigated, the bluff body with a radius of 6mm, the thickness of 5mm, and axial location of 5mm away from the air channel exit results in the best air-fuel mixing.