Mechanism of Microwave-Assisted Ignition in Argon Atmosphere
The effects of N2 atmosphere and Ar atmosphere on the core development of microwave-assisted igni-tion(MAI)were comparatively studied on a self-built MAI experimental bench with a high time resolution electrical diagnosis system.From the origin of microwave plasma formation and discharge current evolution,the internal mechanism of MAI core development was explored.The result shows that,when the equivalent ratio is 0.80,the enhancement effect of microwave in N2 atmosphere and Ar atmosphere is significantly correlated with the intensity of microwave plasma.However,the plasma generation characteristics of the two atmospheres are significantly dif-ferent,and the generation threshold of microwave plasma in Ar atmosphere is lower.When the equivalent ratio of Ar atmosphere is reduced to 0.65,the generation characteristics of microwave plasma are basically the same as that of Ar atmosphere with equivalent ratio of 0.80,but are significantly different from that of N2 atmosphere with equivalent ratio of 0.80.Therefore,the generation characteristics of microwave plasma are mainly determined by the working atmosphere.The microwave-assisted discharge window obtained by the electrical diagnostic system can quantitatively characterize the intensity of the microwave plasma.At the same time,the intensity of the microwave plasma is linearly related to the enhancement effect of the microwave on the ignition core.Finally,it is clarified that there are two effect windows for MAI,namely,the microwave-assisted discharge window for enhanced spark discharge and the microwave-assisted ignition window for enhanced ignition core,both of which work together to determine the ultimate effect of microwave enhancement.
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