微波特性对放电/点火核心形貌特征影响  

Experimental Study on Discharge and Flame Kernel Appearance Under Different Microwave Parameters

作　　者：吴慧珉 王兆文[1,2] 张新华 刘超辉[1] 成晓北 王志[2] Wu Huimin;Wang Zhaowen;Zhang Xinhua;Liu Chaohui;Cheng Xiaobei;Wang Zhi(Department of Energy and Power Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;State Key Laboratory of Automotive Safety and Energy,Tsinghua University,Beijing 100084,China)

机构地区：[1]华中科技大学能源与动力工程学院,湖北武汉430074 [2]清华大学汽车安全与节能国家重点实验室,北京100084

出　　处：《内燃机学报》2022年第1期20-28,共9页Transactions of Csice

基　　金：国家自然科学基金资助项目(51576083).

摘　　要：基于微波辅助点火/放电试验台架,采用因素解耦的方法,探究了微波辅助放电/点火过程中,微波脉冲频率、峰值功率对放电/点火核心半径及形貌的影响规律及其内在机制.研究发现:在频率为1 kHz和功率为1 kW时微波辅助模式的放电/点火核心半径是火花点火模式的173.6%,同时微波馈入导致核心表面出现褶皱;中断效应的存在使不同脉冲频率下放电/点火核心对微波能量的吸收效率不同,脉冲频率为40 kHz时微波能量吸收效率基本饱和,40~80 kHz增强效果相差不到10%;峰值功率对点火核心半径的增强效果呈两段式增强,动力学增强比热增强的增强效果更显著.增大脉冲频率或增大峰值功率,放电/点火核心表面褶皱增多.探索了放电/点火核心表面出现褶皱的形成机制,表明馈入微波导致核心表面出现压力梯度和温度梯度,进而形成褶皱.放电/点火核心半径和形貌与微波参数紧密相关.Effect of microwave parameters on discharge kernel and flame kernel,including kernel size and kernel shape,was visually investigated in a microwave-assisted discharge/ignition experiment test bench by the factor decoupling method.The result shows that both discharge/ignition kernel sizes of the micro-assisted cases are 173.6%larger than those of the spark plug cases.And the kernel shape is wrinkled due to microwave feeding,the discharge/ignition plasma have different microwave absorption efficiency at different pulse frequencies because of cutoff effect.The absorption efficiency is almost saturated at 40 kHz pulse frequency and the discrepancies of enhancement effect between 40—80 kHz are less than 10%.The ignition kernel enhancement exhibits two-stage changes with the microwave peak power due to the different enhance mechanism.The kinetics enhancement effect is more eminent than the thermal enhancement effect.As peak power or pulse frequencies increases,the kernel surface shows more wrinkled structure.In addition,the internal mechanism for the wrinkles on the kernel surface was also studied.The results show that the microwave energy distribution causes various pressure and temperature gradients,which causes wrinkle structure on kernel outer surface.The kernel sizes and kernel shape are determined by the microwave parameters.

关 键 词：微波 点火 放电 等离子体 火焰褶皱 

分 类 号：TK421[动力工程及工程热物理—动力机械及工程]