具物理意義的通用大氣電漿束等效電路模擬之研究

Investigation of a Physical-Based Equivalent Circuit Model of a Universal Atmospheric-Pressure Plasma Jet

黃昰森(Shih-Sen Huang)

指導教授 ： 吳宗信

國立交通大學/工學院/機械工程系所/碩士(2020年)

摘要

本研究以交大APPL實驗室自行開發的通用型大氣電漿束為基礎，旨在建立一個具物理意義的等效電路模型。固定操作頻率20kHz及氣體流量30slm，對於不同操作電壓(6kV、12kV、15kV)及氣體種類(氬氣、氦氣)進行電性量測，並以強化光耦元件(ICCD)成像拍攝放電過程，並且為了確定利薩如分析的可靠度，進行了積分電流與不同種類量測電容的驗證。最後以上述數據為基礎，MATLAB Simulink建構一等效電路模型。等效電路模型分成兩大部分: 電源供應器與電漿源。首先，電源供應器使用符合真實電路的LC電路與變壓器模組，以理想方波產生器表示快速開關所產生的方波電壓，通過一LC電路後產生正弦波，再通過變壓器後產生供應電漿源的電壓；另通過實際外接電容測試後得到電感L值是0.65mH、電容C值是50nF，並且成功重現電源供應器對電容負載的電壓電流波型。其次，電漿源模型則將通用大氣電漿束區分成介電質電容和氣體間隙電容，並區分成放電區與非放電區域，將模擬放電的電阻並聯於放電區的氣隙電容，設定氣體的電壓到達崩潰電壓時，導通電阻部份使電流流過，並且依照放電模式不同設定了兩種電阻模式。另外，以柱狀介電質基本解析解輔以模擬3D靜電場找出石英管放電長度後推算出介電質與不規則形狀氣隙的等效電容。透過實驗得到的平均電流波型找出在不同氣體下的放電面積比; 隨著操作電壓由6kV提高到15kV，氬氣的放電/非放電面積比從7:3提高到9:1、氦氣的放電面積比從8:2提升到19:1。本文捨棄一般文獻常用的外加電流源模擬放電動態行為，改用被動元件 （如電阻）較符合實際物理意義；從時域來看主要現象為均勻放電在前、絲狀放電在後，利用本文提出的模型均可忠實的模擬。在模型中我們發現崩潰電壓的值與均勻放電出現時間有高度相關，大致位於1kV左右。模擬均勻放電的方法是在放電區的氣隙等效電容並聯電阻，並因應電流在正負週期不對稱的行為、比較瞬時的電流信號設定不同電阻值，氬氣的等效電阻明顯產生負半週期大於正半週期的現象，對應操作電壓6kV、12kV、15kV，分別為正半週期60kΩ、36kΩ、30kΩ，負半週期100kΩ、65kΩ、50kΩ，展現出操作電壓越大，等效電阻越小的趨勢，氦氣則較無規律，對應操作電壓6kV、12kV、15kV，分別為正半週期22kΩ、15kΩ、25kΩ，負半週期20kΩ、20kΩ、23kΩ。摸擬絲狀放電則是在均勻放電的電阻上再並聯一電阻，透過電阻並聯會造成等效電阻變小的原理，設定絲狀放電區間內快速開關模擬電阻值快速改變的情況。透過具物理意義的等效電路模擬及實驗研究不同條件下的電性，比較後展現了模擬的電性圖與實驗一致，驗證了模型的實用性。

關鍵字

大氣電漿 ； 等效電路 ； 通用大氣電漿束 ； 介電質障蔽放電過程 ； 利薩如圖形 ； 快速傅立葉轉換分析

並列摘要

In this thesis, a physical-based equivalent circuit model was developed to simulate the discharge electrical dynamics of a semi-cylindrical universal atmospheric-pressure plasma jet invented by APPL (Aerothermal & Plasma Physics Laboratory, NCTU). The major simulation parameters included a frequency of 20 kHz with a peak-to-peak amplitude of 6-15 kV and a argon and helium gas flow rate of 30slm. Discharge processes were imaged using an intensified charge-coupled device (ICCD). The reliability of Lissajous analysis was confirmed by comparing the method of integrated current with different kinds of commercial capacitors. A physical-based equivalent circuit model is developed based on the measured data using the MATLAB Simulink. The model is divided into two major parts, which include the power supply and discharge source. Firstly, the simulation of the power supply applies a realistic LC circuit and a transformer module. An ideal square-wave generator is used to represent the square-wave voltage waveform generated by the fast switching circuit. After passing through an LC circuit, a sine waveform can be generated. After passing through a transformer, the sinusoidal voltage is amplified and supplied to the discharge source. In addition, through the actual external capacitance test, the inductance and capacitance is measured to be 0.65 mH and 50 nF respectively. In addition, the voltage and current waveform applied to the discharge were successfully reproduced based on the above method. Secondly, the discharge source model divides the actual universal atmospheric-pressure plasma jet into a dielectric capacitor and a capacitor across the gas gap. For the discharge, it is further divided into a discharge area and a non-discharge area. A resistor of the simulated discharge is connected in parallel with the gas gap capacitor of the discharge area. When the voltage of the gas gap reaches the breakdown voltage, the switch of the resistor drives the current to occur. In addition, an equivalent length of the analytical solution of the cylindrical dielectric was obtained with the help of the simulation of a 3D electrostatic field, which leads to the calculation of an effective capacitance for this universal plasma jet. The ratios of discharge to non-discharge area for argon and helium discharges were found through the fitting of the averaged measured current waveform. The results show that the ratio of discharge to non-discharge area changed from 7:3 to 9:1 as the operating voltage increase from 6 kV to 15 kV for argon and from 8:2 to 19:1 for helium. In this thesis, the artificial current source often adopted in most literature is removed, instead a resistor is used which is more physical-based. In addition, the breakdown voltage is found to be about 1 kV, which is relatively universal for the modeling of homogeneous discharge occurs first and then by the filamentary one for both argon and helium discharges modeled in this thesis. The equivalent resistance of argon discharge obviously presents a phenomenon in which the negative half period is greater than the positive half period, corresponding to the operating voltages of 6kV, 12kV, 15kV, which are 60kΩ, 36kΩ, 30kΩ for positive period, 100kΩ, 65kΩ, 50kΩ for negative period. It shows that the larger the operating voltage is, the smaller the equivalent resistance is. However, it is relatively irregular for helium discharge. As for the modeling of filamentary discharge, a resistor was connected in parallel with the homogenous discharge resistor, which makes the equivalent resistance smaller. Then, a fast switch was used to activate filamentary discharge. In summary, a physical-based equivalent circuit model is proposed for simulating the electrical dynamics of an universal APPJ and the results are compatible with the experimental observations.

並列關鍵字

Atmospheric Plasma ； Equivalent Circuit ； Universal Atmospheric-Pressure Plasma Jet ； Dielectric Barrier Discharge Evolution ； Lissajous Figure ； Fast Fourier Transfer Analysis

參考文獻

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