Based on the power diagnosis method,an enhancement effect of different microwave parameters(pulse waveform and feed delay time)on microwave assisted ignition was studied.The microwave energy coupling with the ignition kernel during ignition was precisely measured,and the mechanism of energy coupling was analyzed.The results show that a part of the incident microwave energy is coupled to the ignition kernel in the form of plasma generation.The coupling energy increases with the increase of the microwave pulse power and decreases with the increase of the delay time,and the highest coupling energy reaches 6.16 mJ.The enhancement effect of the ignition kernel is consistent with the variation trend of the coupling energy,which indicates that the coupling microwave energy is the essence of the enhancement of ignition.The energy coupling efficiency(coupling energy/incident en-ergy)generally decreases with the increase of pulse width and delay time,and the highest coupling efficiency reaches 7.23% .It is also found that the efficiency of microwave energy coupling increases to a plateau,which is de-fined as the saturated coupling pattern.The shorter the transition to the saturated coupling pattern is,the higher the energy coupling efficiency is.The energy coupling efficiency of the saturated coupling pattern is not affected by the microwave parameters,but the transition can be facilitated by the pulse waveform with higher power,shorter pulse width and lower delay time,leading to a significant improvement of the ignition enhancement effect.
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