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The ignition energy has a significant effect on the initial unsteady evolution of the flame kernel, which will affect the performance and emissions of a spark-ignition engine and the uncertainty in determining laminar burning velocity and Markstein length as a result of the inappropriate selection of the lower limit of the flame radius. In the present study, the outwardly propagating spherical flame was employed to experimentally investigate the initial propagation characteristics of ethanol/air premixed flames at different ignition energies. The emphases were to provide new insight into the effect of ignition energy on the initial propagation of the premixed flame and to develop a new reference flame radius (the lower limit of the flame radius) for deriving the laminar burning velocity and Markstein length of ethanol/air mixtures. Results show that the initial flame speed of ethanol/air mixtures increases with the increase of the ignition energy and the spark ignition has only a marginal effect on the in...

Laminar burning velocities and Markstein lengths of premixed methane–n-heptane–air mixtures were experimentally investigated at an initial pressure of 0.1 MPa, initial temperatures of 358, 393, and...