Numerical analysis of the effect of swirl angle and fuel equivalence ratio on the methanol combustion characteristics in a swirl burner

Abstract

The outstanding advantages of methanol such as low pollutant emissions of nitrogen oxides (NOx) and carbon monoxide (CO) make it a promising clean-burning fuel. Despite, the latent heat of vaporization of methanol is 3.70 times that of gasoline, the low heating value of methanol is one of the most critical barriers to its effective utilization in industrial applications. Thus, the methanol burner needs to be effectively designed to determine the desired combustion characteristics and the optimal design of this type of clean burner. Hence, this study presents a computational fluid dynamic analysis on the combustion characteristics of a methanol swirling burner with two layers of swirling blades. A particular focus of this study is emphasized on the effects of different swirling blade angles (45°+45°, 60°+60°, and 45°+60°) and various equivalence ratios (0.5, 0.75, 1.0, 1.25, and 1.75) on the combustion characteristics and pollutants formation of the swirl burner. The velocity and temperature profiles, combustion characteristics, and concentrations of major combustion species are analyzed in detail. The results show that the blade angle arrangement of 45°+ 60° exhibits the best combustion characteristics in comparison with the other blade angle arrangements. It is also found that the BA3 with an equivalent ratio in the range of 1.0–1.25 shows the best performance in the emissions of NOx and CO compared with other combinations of swirling blade arrangements and equivalence ratios. More specifically, the optimal equivalence ratio ranges from 1.0 to 1.25 at which the NOx and CO emissions are measured to be 27.0 and 11.0 mg/m3, respectively.