Studies of the dynamics of autoignition assisted outwardly propagating spherical cool and double flames under shock-tube conditions

The initiation, propagation, and transition of the autoignition assisted spherical cool flame double are studied numerically experimentally using n-heptane/air/He mixtures under shock-tube experimental conditions over a wide range temperatures. primary goal current study is to understand effects ignition Damkohler number, energy, curvature, autoignition-induced flow compression on propagation flames ensure proper interpretation speed measurements at engine-relevant conditions. results show that high there three different regimes, flame, hot flame. accelerates dramatically with increase number. In addition, it found change regime, low-temperature autoignition, stretch, result in complicated non-linear dependence stretch. also reveal has much lower Markstein length compared T > 600 K. Moreover, both trailing front can propagate faster alone same mixture conditions, leading nonlinear initial temperature. simulated trajectories temperature agree qualitatively well experiments. A quantitative criterion accurate measurement proposed. present provides important physical insight guidance for engine relevant