The Format Design And Implementation Of Control System Of Platform For Atmospheric-Pressure Microwave Plasma Torch

The atmospheric pressure microwave plasma torch?APMPT?has a great application prospect in the industrial field due to its stability and high ionization degree and electron density.However,the noise generated by APMPT,the toxic gas produced in some cases,the hazard from leakage of electromagnetic radiation,and the harsh working environment caused by similar factors endanger the health of operators greatly.In addition,the system of APMPT is composed of many function modules,the cooperative operation between the modules is cumbersome,which not only increases the possibility of wrong operation during use,but also sets a barrier in combining with other system.And the difficulty of coordinating the work is greatly increased,which limits the development of its application to some extent.Therefore,based on a set of atmospheric pressure microwave plasma equipment?APPLAS-MPT3I?designed by our laboratory,a control system based on LabVIEW was designed and implemented for this equipment.Under the consideration of the previous operating habits,the system integrates the functions of each module reasonably,making the operation safer and more convenient.At the same time,due to its excellent operational stability and reasonable structure,it has significance in promotion for the application of atmospheric pressure microwave plasma torch in industry.The system is characterized by a modular structure,compose of a microwave source control module,a plasma torch generating device control module,a gas flow control module,and an image acquisition module.Each sub-module is both independent of each other and coordinated with each other.The plasma torch control module consists of a serial relay and a power supply for controlling the thermal resistance switch and the igniter.The microwave power supply has an RS-485 serial port,which can be directly connected to the computer to control the input value of the power and feedback the working parameters.The gas flow controller is coupled to the computer via a digital to analog converter for controlling gas flow and feeding back the input gas flow value.The hardware part of the image acquisition module is mainly a high-definition USB control line camera for collecting and detecting the discharge of the plasma torch.We use this control system to achieve the stable working state of atmospheric pressure microwave plasma torch discharge and study the decomposition efficiency of CO₂ gas by APMPT.It was observed that the CO₂ plasma torch consisted of a bright central region and a dim blue afterglow region;the plasma torch becomes unstable when the input power was below 1200 W or the gas flow was below 10 SLM.In addition,the influence of the change of CO₂ gas input and microwave input power on the torch shape was analyzed.It was found that the volume of the plasma torch was greatly affected by the input power,while the gas flow had little effect on it.In addition,we diagnosed the CO₂ plasma torch by optical emission spectroscopy,and found that there are atomic lines of C and O elements with a certain intensity in the long-wavelength regime of visible range.The spectral line and the relatively weak O and C element line are almost covered by the C₂?d₃?_g-a³?_u?and CN?B₂?⁺-X₂?⁺?molecular bands.At the same time,the spectra in different working parameters and different positions are compared.The reaction mechanism was discussed for further work.In the follow-up work,we will develop program for diagnosis of the CO₂ plasma temperature and CO₂ gas decomposition rate and explore the effects of decomposition of CO₂ gas when introducing Ar,N₂ and CH₄.