B151 熱損失を伴う水素-空気予混合火炎の不安定性に関する数値解析(OS-5 燃焼研究における可視化,計測およびモデル化手法の進展I)

Abstract

The instability of hydrogen-air premixed flames with heat loss is investigated by two-dimensional, unsteady calculations of reactive flows. The numerical model contains detailed hydrogen-oxygen combustion with 17 elementary reactions of 8 reactive species and a nitrogen diluent, compressibility, viscosity, heat conduction, molecular diffusion, and heat loss of Newtonian type. Estimating the diffusive-thermal effect on the instability of premixed flames, the equivalence ratio is varied 0.75 to 1.25. A sufficiently small disturbance is superimposed on a planar flame to obtain the dispersion relation and linearly most unstable wave number. To investigate the characteristics of cellular flames, the disturbance with the linearly most unstable wave number, i.e., the critical wave number, is superimposed. The superimposed disturbance evolves owing to intrinsic instability, and then the cellular-flame front forms. With an increase in heat-loss parameter, the burning velocity of a cellular flame becomes monotonously smaller, which is due to the decrease in thermal expansion. However, the burning velocity of a cellular flame normalized by that of a planar flame at the equivalence ratio of 0.75 becomes larger near the quenching point.