Numerical Study of the Effect of Staged Gun and Quarl on the Performance of Low-NOx Burners

Three-dimensional numerical simulations were carried out to study fuel-staged low-NOx burners (LNB). The effect of the number of staged guns (four and six) and quarl style (Venturi and boss) on the performance of the LNBs was investigated. The flow field, flame temperature, OH radical field, and NO emission were analyzed. The turbulence, radiation, and chemical reactions were simulated with the standard k-epsilon model, discrete ordinate (DO) model, and probability density function mixture fraction model, respectively, using a commercial computational fluid dynamics code. The numerical model was validated with experimental measurements at different excess air conditions. The agreement of the calculated and measured NO emission is remarkable; therefore, the present model is considered reliable. The results indicate that the number of staged guns has little effect on the NO emission; the boss quarl increases mean air velocity, changes staged gas flow direction, and reduces peak flame temperature and peak OH mole fraction. The boss quarl reduces more than 60% of the NO emission compared with the Venturi quarl.