大气压射流冷等离子体的产生和特性研究

【作者】 程诚；

【导师】 詹如娟；

【作者基本信息】 中国科学技术大学 ， 等离子体物理， 2006， 博士

【摘要】 大气压放电因为不需要真空系统，便于工业应用。正是这个原因，有关大气压产生稳定的非平衡等离子体的放电，特别是大气压辉光放电的研究，已经成为国内外低温等离子体领域的一个研究热点。 近来，几种新颖的大气压等离子体源装置被研制出来，例如，一个大气压均匀辉光放电、大气压表面放电和大气压射流冷等离子体等。 大气压射流冷等离子体由于等离子体可以形成在放电区域之外，而且气体温度较低，用于材料处理时不仅减小了高温对物体表面带来的损伤，而且还可克服放电区域狭小给处理工作带来的不便，有利于处理体积大或复杂的物体，而且大气压射流冷等离子体可以在开放的环境中通入其他(非空气)气体进行工作，可以说大气压冷射流等离子体是大气压下产生非平衡等离子体的一种新的形式，已经受到越来越多的关注。 但是目前大气压射流冷等离子体的气体温度还是比较高的，达到50-300℃，这样就不适合处理一些不耐高温的物体；此外这种等离子体装置的处理面积较小，有待进一步改进。 为了改进大气压射流等离子体的不足，我们设计了几种大气压射流冷等离子体发生器，并作了一系列的实验研究。大气压射流冷等离子体的气体温度大约为25.30℃，低于目前已报道的大气压射流等离子体的气体温度50-300℃。我们通过改变喷嘴的形状来增大等离子体处理面积。对大气压射流等离子体的放电特性进行了研究：当固定电压峰值为12kV，电源频率在2-11kHz之间时，产生大气压射流冷等离子体的放电主要以丝状放电为主：电源频率在12-16kHz之时，放电主要以“类辉光放电”为主。当固定频率为7kHz改变电压时，我们发现随着电压的增加，产生大气压射流冷等离子体的放电由丝状放电为主向“类辉光放电”为主转变。我们利用发射光谱诊断手段对大气压射流冷等离子体的特性进行研究，通过费米-狄拉克模型对不同频率下的大气压射流冷等离子体的电子激发温度进行了计算，发现不同频率下的电子激发温度在考虑实验误差的情况下变化很小，说明在固定电压下电子激发温度受频率的影响不大。此外，我们还利用等效电路的方法推导和计算了同电压峰值不同频率下放电气隙的传导电流和加在放电气隙的电压，并根据传导电流对不同频率下的大气压射流冷等离子体的电子密更多还原

【Abstract】 The atmospheric pressure discharges (APDs) have many advantages because they do not need a high vacuum system and show to be of great prospect for a number of industrial applications. For this reason, there has been increasing interest in APDs, especially atmospheric pressure glow discharge (APGD), in the global low temperature plasma fields.Recently, a few novel atmospheric pressure plasma sources have been developed, such as the one atmosphere uniform glow discharge plasma (OAUGDP), the atmospheric pressure surface discharge and the atmospheric pressure plasma jet (APPJ). The discharge regions of these plasma sources are so limited that they are not suitable to treat the bulky or complex objects except APPJ. In addition, APPJ can operate with various gas in open air without vacuum equipment, and the other atmospheric pressure plasma devices have no this predominance. Recently, there has been great interest in the APPJ because of its advantages.However, the plasma gas temperature of APPJ is 50-300°C; it is not suitable for treating those vulnerable objects. The treatment area of APPJ is small, and it should be enlarged.To resolve the problem of the APPJ, a set of atmospheric pressure cold plasma jet (APCPJ) setup has been developed in our lab and we had performed many kinds of experiments. The gas temperature of APCPJ is lower than APPJ and the cold plasma torch, and it only 25-30°C. We augment the treatment area of APCPJ by changing its shape of nozzle. The discharge character of the APCPJ is studied. The main of discharge is filamentary discharge when electrical source operate between 2-11 kHz and the peak value of voltage is fixed at 12kV; the main of discharge is "like glow discharge" when electrical source operate between 12-16kHz with the same peak value of voltage. The discharge changes from filamentary discharge to "like glow discharge", when the frequency of electrical source is fixed at 7kHz and the peak value of voltage is increased. The emission spectrum is used as the APCPJ diagnostic methods to study the plasma characteristics. Excitation temperatures of APCPJ in更多还原