Effect of flame-wall impingement on heat transfer characteristics and soot migration in methane inverse diffusion flames

Flame-wall collisions are common in industrial and household applications. Therefore, it is very important to carry out detailed research of flame structure and soot generation during flame-wall impingement. In this study, the reaction characteristics and soot distribution of impinging wall flames at different equivalence ratios (lambda) and impact heights (L) were studied by means of spectral diagnosis and CFD simulation. The results noted that the increase of lambda causes the OH* peak intensities and soot concentration to rise and then decrease, reaching a maximum value at lambda = 0.5. With the increase of lambda, the amount of precursor polycyclic aromatic hydrocarbons (A1-A4) decreased while the soot particles growth rate increased. When lambda> 0.5, the soot oxidation is faster than the soot generation, and the soot is gradually oxidized, so that the soot concentration is the highest when lambda = 0.5. With the increase of L, the jet flame fully develops before the impact plate, and the flame brightness gradually increases. The increase of the L leads to a weakening of the methane-oxygen mixing and at the same time to a gradual loss of the kinetic energy of the flame along the impingement plate, which further causes an increase of the temperature and the soot content in the region where the flame jet is fully developed.