The ignition and combustion in the main-chamber due to the combustion jet injected through an orifice are simulated numerically. The results show that a quasiperiodical oscillation of injected jet forms the basic shape of wrinkled flame front. Although this wrinkled flame front can be classified as corrugated flamelets, the head of the combustion jet is found to have a characteristic combustion process, i. e. an “abnormal” flame sustained by the downstream burnt gas jet: Different from the other parts of flame, the abnormal flame gives a strange correlation between the heat release rate and H
2O mass production rate. Near the head of combustion jet, furthermore, the surrounding fresh mixture is entrained into the burnt gas jet by the action of vortex ring and is forced to ignite by the accumulation of partially burnt gas. Thus, combustion at the head portion strongly interacts with the flowfield, and therefore the oscillating jet accelerates combustion there.
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