中文摘要：

混粉准干式电火花加工以气、液、固三相流作为工作介质,能够有效改善气中加工短路率高、加工效率低的问题。以纯净气体介质的击穿理论为基础,对三相流工作介质的击穿机理进行理论分析,阐明固、液分散相的作用机制。建立混粉准干式电火花加工的极间电场强度表达式,给出三相流中加工的放电间隙计算式,从理论上证明分散相的加入使得混粉准干式电火花加工的放电间隙较气中加工大,指出放电间隙增大是加工效率提高的一个重要原因。进行压缩空气中和三相流介质中的放电加工对比试验。测得两种加工介质中的放电间隙值,试验证实三相流工作介质具有放电间隙增大效果。测得放电电压波形,证实气体连续相中固、液分散相的加入能够降低短路率,提高加工稳定性。

英文摘要：

Powder mixed near dry electrical discharge machining（PMND EDM） uses gas-liquid-powder mixture as the three phase dielectric medium.Problems such as high short circuit rate and low machining efficiency in dry electrical discharge machining（DEDM） can be solved effectively.Based on the breakdown mechanism of pure gas medium,theory analysis of breakdown mechanism for three phase dielectric medium is carried out.Function of liquid and solid dispersed phase is illustrated.Formula of electric field strength between electrodes for PMND EDM is established.Equation for discharge gap calculation in PMND EDM is given.It is theoretically proved that the discharge gap of PMND EDM is larger than that of DEDM due to the addition of dispersed phase.And discharge gap increase is considered to be one of the important reasons for machining efficiency improvement.Comparison experiments are conducted in compressed air and three phase dielectric medium,respectively.Discharge gap is obtained.And it is verified that three phase flow can increase discharge gap.Discharging voltage waves are obtained,and it is confirmed that short circuit rate is reduced and machining efficiency is improved due to the addition of dispersed phase to continuous phase.