Abstract
The effect of methane content on the flame structure, flow field and pressure characteristics of lean premixed ammonia/air gas combustion was systematically investigated in a constant volume chamber (CVC) under different methane content with a pre-combustion chamber (PCC). The results show that the auto-ignition locations of the CH4/NH3/Air dilute fuels begin at the top of the MCC and propagate from top to bottom, which is different from the auto-ignition at the bottom of the lean methane mixtures. Moreover, with the increase of ammonia content, the flame propagation time induced by jet ignition becomes longer, and the first derivative of the pressure changes from bimodal to unimodal, where the amplitude of the first peak gradually decreases and the second peak gradually dominates. Finally, chemical kinetic analysis combined with flame dynamics analysis showed that a reduction in fuel activity resulted in a shift in the heat release rate. Initially, the heat release rate was mainly dominated by the jet ignition. Subsequently, the auto-ignition became the dominant factor. This shift led to a shorter flame propagation time caused by auto-ignition, which increased the heat release rate in the auto-ignition stage.
Published Version
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