直流电压激励单电极氩气射流阵列的放电模式

Investigation on discharge mode of an argon plasma jet array with a single electrode excited by a direct-current voltage

大气压等离子体射流在诸多领域具有非常广泛的应用。为了提高大面积材料的处理效率,通常需要将多个射流排列为射流阵列,但由于阵列中等离子体羽间的相互作用,实际上很难产生大面积均匀等离子体羽。针对于此,本文利用直流电压激励单电极氩气射流阵列,产生了大面积均匀等离子体羽。研究发现,在低电压下放电为分立的等离子体羽,而高电压下为均匀片状等离子体羽。片状等离子体羽随着电压、氩气流量及空气流量的增加而变长。电学和光学测量结果表明,分立等离子体羽的放电电流和发光信号均为频率很高的小脉冲。片状等离子体羽的电流和发光信号为频率很低的大脉冲,并且在两个大脉冲之间也存在着小脉冲。利用高速影像对分立羽和片状羽的产生机制进行了研究。结果表明分立羽中阳极羽对应正流光放电机制,而阴极羽对应汤森放电机制。片状羽的击穿机制也是流光机制,流光击穿后会产生辉光放电丝,此后辉光微放电丝沿着气流向下游运动。此外,利用光纤测温仪对片状等离子体羽的气体温度进行了研究,发现片状等离子体羽的气体温度不超过65℃。

Atmospheric pressure plasma jet has extensive applications in various fields.Usually,many jets are operated in parallel to compose a jet array in order to improve the treatment efficiency for large-area materials.However,it is essentially very difficult to generate a uniform plasma plume with large scale due to the interactions between plasma plumes of the jet array.It reported a uniform plasma plume with a large scale that is produced in an argon jet array excited by a direct-current voltage.Results show that two discrete plasma plumes are generated with a low voltage,while a uniform planar plume is produced with a high voltage.The planar plume elongates with increasing voltage,argon flow rate,and air flow rate.Electrical and optical measurements reveal that the discharge current and emission signal present weak pulses with a high frequency for the discrete plume,while strong pulses with a low frequency for the planar plume.Moreover,the weak pulses also appear in between two strong pulses.By fast photography,the mechanism for the discrete plume and the planar plume is investigated.It is found that for the discrete plume,a positive streamer is involved in the plume near the anode,while it is a Townsend discharge regime for the plume near the cathode.Moreover,the planar plume starts with a streamer discharge,which resulting in a discharge filament in a glow discharge regime.Then,the glow micro-discharge filament propagates with the argon flow.Besides,gas temperature of the planar plume is investigated by a optical fiber thermometer,which is less than 65℃for the planar plume.