Development And Applications Of A Repetitive Pulsed Plasma Source

Atmospheric discharge is an international hotspot in the field of plasma which can produce non-thermal plasma with high activity and does not require expensive vacuum devices. Power supply is an important part of the atmospheric discharge devices and pulsed power source is a high-quality power supply for driving the atmospheric plasma reactor, because pulsed power source has bigger injection power, higher energy efficiency and ability to produce more active particles. As the market is always pursuing bigger power and more reliable pulsed power source, pulsed power technology is developing rapidly. Based on TLT (Transmission Line Transformer), pulsed power technology can achieve several output modes in series and parallel ways. Meanwhile, pulsed power technology shows a good performance in matching plasma reactor and has a high energy efficiency and it is prospective for environmental applications such as air cleaning and water treatment.In this paper, a set of high efficient and reliable pulsed plasma source is developed from the principle of the circuit to the design and implementation. The main work includes a primary microsecond pulsed power source which can be used in plasma jet system and a nanosecond pulsed power source with single switch TLT that can generate pulsed corona plasma for VOCs(Volatile Organic Compounds) treatment. In the exploration of applying the pulsed plasma discharge, the output characteristics and energy efficiency of the pulse source are also concerned. The contents and conclusions of this dissertation are summarized as follow:The primary microsecond pulsed power source is able to generate microsecond pulse with a pulse width of 0.5-10 μs, a peak voltage up to 15 kV, a pulsed frequency from 0.05-30 kHz. Pulse polarity can be positive or negative.Helium (He) plasma jet is realized by the primary pulsed power source. It can rapidly inactivate S. aureus bacteria on the agar plate, with the formation of a significant bactericidal spot. The area of bactericidal spot is positively correlated with the pulsed voltage, pulsed frequency, Helium flow rate and treatment duration, and negatively correlated with the treatment distance. Meanwhile, the negative pulsed plasma has better treatment effect than the positive one. When the peak voltage is 4-12 kV and repetition rate is 5-20 kHz, the power of generated plasma jet is 0.6-12.8 W. The length of plasma jet increases with the pulsed voltage, and the power increases with the pulsed frequency. When the voltage at 12 kV, the Helium flow rate at 6 L/min, positive pulsed discharge can stably generate plasma jet length of about 4 cm.When the primary pulsed power source combined with single switch TLT is connected to a matched resistive load, repetitive nanosecond pulses are generated with a rise-time of about 15 ns, a width of about 30 ns, a peak voltage up to 20 kV in series, a peak current to 340 A in parallel. Maximum pulsed frequency is to 600 Hz. Pulse polarity also can be positive or negative.Single switch TLT using LCR trigger circuit consists of a 1.11 nF capacitor bank, a three electrodes spark gap switch and one stage TLT made by 2 coaxial cables RG217. The nanosecond pulse source can generate corona plasma by driving self-made wire tube reactor. The energy efficiency of pulsed power generator is up to 87.3% in positive pulse discharge and only 37.4% in negative pulse discharge. At the highest frequency of 600 Hz, the peak output power of the reactor is 59.4 W. When nanosecond pulsed corona discharge plasma is used, the styrene removal efficiency can reach 98.6% when SIE (specific input energy) is 27.4 J/L. In the same SIE, negative pulsed discharge has the best treatment efficiency. However, in the same input energy, positive pulsed discharge becomes the best.