【作者】 徐俊；

【导师】 徐从裕；

【作者基本信息】 合肥工业大学 ， 精密仪器及机械， 2020， 硕士

【摘要】 基于目前固废、废气等污染物对环境和人类健康造成的危害,而传统的污染物处理方法又面临着容易产生二次污染和通用性差等问题,等离子体技术属于一种污染物无害化处理的新兴技术。等离子体通过是否热平衡划分可分为冷等离子体和热等离子体,冷等离子体已有很多成功的应用案例,但是使用热等离子体处理危险污染物的研究还比较少。相较于前者,热等离子体的温度高,并且能量集中能够分解一些难于分解的污染物,并且无特定处理对象,是一种非常理想的无害化处理技术。但是目前的热等离子体技术能梯度分布太大,直接使用无法与气体和污染物充分接触,扩大电弧面积又面临电源功率过高的问题。针对目前热等离子体技术难以实用化的问题,本文以典型的滑动弧结构为研究对象,设计一种新型等离子体滑动弧发生器,同时建立能够驱动该设备的低功耗电源系统,通过仿真的手段分析装置流场和等离子场,并在此基础上进行结构改进,最后通过实验测试外界参数对热等离子场的影响。本文的主要研究内容可以归纳为:(1)热等离子场的控制方案:电极结构基于滑动弧原理,除了产生热等离子体的工作电极以外,还设计一组辅助电极,与工作电极呈十字交叉分布,用于提前击穿空气使得工作电极能够在低电压中起弧。为驱动工作电极设计大电流电路,采用全桥电路的逆变拓扑方式和电流环、电压环结合的反馈控制方式,保证电源的稳定输出。(2)有限元仿真分析:仿真理论分析分为气路流道的流场仿真和电极的等离子场仿真。流场仿真涉及到到气流的耦合,模型的选择;等离子体放电理论涉及到到电子的漂移扩散,粒子碰撞、重物质输运、化学反应等。运用ANSYS CFX建立流道气路通道的仿真模型,然后依据仿真改进装置气路结构,为等离子场发生建立一个平稳的流场条件;等离子场仿真使用COMSOL Multiphysics建立等离子体产生空间的反应模型,通过仿真得知辅助电极间隙最小处场强最大,明确了两组电极相互作用下周围空气电导率的改变情况。(3)热等离子体场实验研究:搭载电源系统和气路通道,在大气压环境下,通过调整气阀和电流大小探究不同功率和气流流速条件下对电弧的拉伸长度和电弧周期的影响,发现电流的增大确实能够提高拉伸长度和持续时间。但是在电流达到7A后,增强幅度不大。适当的提高气流流速,在一定程度上能够延长热等离子体电弧的拉长的程度,但是流速过大时,反而不利于热等离子体电弧的维持。(4)基于物联网技术的监测系统:搭建基于ARM9的物联网技术监测系统,其中包括现场监测和远程监测两大部分。保证在设备的运行界面和远端的上位机中都能对装置参数进行查看,提高对设备工作状态以及处理结果的监测效率。更多还原

【Abstract】 Based on the current harm caused by pollutants such as solid waste and exhaust gas to the environment and human health,while traditional pollutant treatment methods are faced with problems such as secondary pollution and poor versatility,plasma technology is an emerging technology for harmless treatment of pollutants.Plasma can be divided into cold plasma and thermal plasma by whether it is thermally balanced.There have been many successful applications of cold plasma,but the use of thermal plasma to deal with dangerous pollutants is still relatively few.Compared with the former,Therefore,it is an ideal harmless treatment technology that can decompose some pollutants which are difficult to decompose and has no specific treatment object.However,the energy gradient distribution of the current thermal plasma is too large to directly contact the gas and pollutants when used directly,and the expansion of arc area is faced with the problem of high power supply.In order to solve the problem that the current thermal plasma technology is difficult to be practical,this paper designs a new plasma sliding arc generator,based on the typical sliding arc structure,At the same time,a low power supply system is established to drive the device,and the structure is improved on the basis of the flow field and plasma field of the device are analyzed by means of simulation.Finally,the influence of external parameters on the thermal plasma field is tested through experiments.The main research contents of this paper can be summarized as:(1)Design of thermal plasma field generator: the electrode structure is based on the principle of sliding arc.In addition to the working electrode that generates thermal plasma,a set of auxiliary high-voltage electrodes are also designed,and it is used to break the air in advance so that the working electrode can arc in low voltage,which is distributed in a cross shape with the working electrode,A large current circuit is designed to drive the working electrode.The inverter topology of the full-bridge circuit and the feedback control method combining the current loop and the voltage loop are used to ensure the stable output of the power supply.(2)Finite element simulation analysis: the theoretical analysis is divided into flow field simulation of gas channel and plasma field simulation of electrode.Flow field simulation involves the coupling of airflow and the selection of model.Plasma discharge theory involves electron drift diffusion,particle collision,heavy matter transport,chemical reaction,etc.ANSYS CFX was used to establish the simulation model of the flow channel,then improve the gas path structure of the device according to the simulation to establish a stable flow field condition for the plasma field generation;the plasma field simulation uses COMSOL Multiphysics to establish the reaction model of the plasma generation space,it is found that the field strength is the largest at the minimum electrode gap,and the range of the surrounding air conductivity under the interaction of the two groups of electrodes is clarified.(3)Experimental construction of thermal plasma generator: equipped with a power supply system and gas channel,under atmospheric pressure environment,by adjusting the air valve and current to explore the influence of different power and flow velocity on the stretching length of arc and arc cycle under the atmospheric pressure environment,but after the current reaches 7A,the enhancement is very small.Therefore,properly increasing the flow rate of the gas flow will extend the elongation of the thermal plasma arc,but when the flow rate is increased too much,it is not suitable to the maintenance of the thermal plasma arc.(4)Monitoring system based on Internet of Things technology: A monitoring system of Internet of things based on ARM9 was built,which includes two parts: on-site monitoring and remote monitoring.To ensure that the device parameters can be checked in both the operating interface of the device and the remote upper computer,so as to improve the monitoring efficiency of the working status and processing results of the device.更多还原