Study on the influence of flame inherent instabilities on crack propagation of expanding premixed flame

To evaluate the effect of hydrogen fraction and equivalence ratio on the competitive relationship between flame and crack development, combustion experiments of H-2/CO/air mixtures at various equivalence ratios and hydrogen fractions were conducted in a constant volume combustion chamber. The crack length and growth rate were defined. The results indicate that the crack length and the number of the cells increase with the flame development. With the increase (decrease) in hydrogen fraction (equivalence ratio), the disturbances caused by flame inherent instabilities increases, and the crack length at the same radius increases. The appearance and generation of the new cracks dominate the cellular structure process, clear increasing the crack growth rate. The effect of hydrogen fraction on the development of cracks is more obvious at lower equivalence ratios. Flame stretch affects the competitive relationship between crack growth rate and flame propagation speed, exhibiting two completely different trends. The critical crack growth rate decreases with the increase of the equivalent ratio.