| The surface dielectric barrier discharge (SDBD) could generate plasma with large area and uniformity along the surface of the dielectric with little restriction of the discharge space. It has some basic properties, which make it have a promising application prospect at the field of aerodynamic, biomedicine and environmental protection. They are relatively simple to manufacture, simple to operate and with fast response times. In addition, plenty of active particles, such as 03, O, OH and H2O2, and their excited states, etc., are produced along with the discharge. In recent years, plasma has been paid attention to by the research people at home and abroad, and significant progresses have been made. At present, the investigation on SDBD plasma and its application is still at the preliminarily exploring stage. Therefore, research on the characteristics of SDBD with different parameters will have important theoretical significance and engineering value to the development of its application.An experimental system is constructed, which is mainly constituted by a plasma generation devices, a subsystem designed for electronically and optically diagnosing plasma. It can realize the record of the waveforms of voltage-current, images of the discharge and the optical emission spectrum emitted from the discharge and then the calculate of plasma parameters, such as the discharge power, N2(C3∏u) rotational and vibrational temperature, etc.. Furthermore, in order to better understand the discharge mechanism of the surface dielectric barrier discharge and illustrate the regularity evolution of characteristic parameters of the plasma, an equivalent circuit of the asymmetric surface dielectric barrier discharge plasma generator has been established based on the experimental results. The main contents and results are summarized as follows.Firstly, the basic characteristics of the SDBD plasma under the nanosecond pulsed power has been investigated systematically. Then the influence of the symmetry of electrode of the actuator, encapsulation of the back electrode and the connection of the high voltage and ground electrode on the plasma parameters, such as current, deposited energy, transported charges, optical emission spectrum intensity of N2 (C3∏u'B3∏g) and N2+(B2∑u+'X2∑g+,0-0,391.4nm), N2(C3∏u) rotational and vibrational temperature are experimentally compared under different repeat frequencies of nanosecond pulse. It is shown that with the increase of the frequency, the deposited energy and transported charges decrease. The emission intensity has an obvious increase, and the N2(C3∏u) rotational temperature increase, but N2(C3∏u) vibrational temperature decreases. Compared with the asymmetrical structure of the actuator, the discharge of the symmetrical structure occurs earlier, with higher current value, N2(C3∏u) vibrational temperature and rotational temperature. The encapsulation of the back electrode improves the efficiency of the power consumption, and higher emission intensity, N2(C3∏u) vibrational temperature and rotational temperature are obtained. Because of the effect of polarity, the discharge of the HV-GND happens later than that of the GND-HV, however, can achieve higher peak current, emission intensity, deposited energy, transported charges, N2(C3∏u) vibrational temperature and rotational temperature.The SDBD discharge characteristics under the effect of the sine wave power are analyzed in comparison with that of nanosecond pulsed power. Further, the properties of the current, discharge power and transport charge, optical emission spectrum intensity of N2 (C3∏u'B3∏g) and N2+(B2∑u+'X2∑g+,0-0,391.4nm), N2(C3∏u) vibrational temperature and rotational temperature with the symmetry of electrode of the actuator, encapsulation of the back electrode and the connection of the high voltage and ground electrode are experimentally compared under different frequencies of the power. And the following results are obtained:comparing with the nanosecond pulsed power, the N2(C3∏u) rotational temperature is higher when the power is supplied by the sine wave power, however, the N2(C3∏u) vibrational temperature is lower, and the discharge current is quite lower than that of the nanosecond pulsed power. The composition of the optical emission spectrum is the same. The increase of the frequency is benefical for the increasing of discharge. The influence of the symmetry of the electrode, the encapsulation of the back electrode on the discharge is consistent with that of the nanosecond pulsed power. However, since the sine wave power is alternating current power, the effect on the SDBD discharge plasma parameters of the HV-GND and GND-HV is almost the same.The effect of argon flow on the air surface dielectric barrier discharge excited by a sinusoidal excitation voltage at atmospheric pressure is experimentally investigated and discussed with the purpose to strengthen the discharge. The plasma discharge characteristics including waveforms of voltage-current, images of the discharge and the optical emission spectrum and the mechanisms of excitation and ionization processes of nitrogen molecules have been discussed in this mixture. Furthermore, the spactial distribution of optical emission intensities of N2 (C3∏u'B3∏g), Na+(B2∑u+ 'X2∑g+,0-0,391.4nm) and Ar I(2P,'1S2.750.39nm), N2(C3∏u) rotational and vibrational temperature have also been analyzed. Finally, the influences of the argon flow rate, tube spacing, voltage amplitude and frequency on the plasma characteristics are discussed. It is shown that stable large-volume plasma is developed with higher discharge intensity and uniformity. Thermal effect of the plasma is evident. It is beneficial for the increase of the momentum transfer efficiency and the induced velocity by using argon-induced discharge. The spatial distribution results shows that the intensity of the spectral lines and the N2(C3∏u) rotatioal temperature have the maximum value at the central position and decrease along the electrode on both sides, however, variations of the N2(C3∏u) vibrational temperature are just contrary. In addition, as the argon flow increases, the discharge intensity increases firstly then reduces, while the N2(C3∏u)rotational temperature increases. N2(C3∏u) vibrational temperature decreases after the addition of argon flow. And it increases at first, then decreases and tends to stability at last with increasing flow rate. There is almost no influence of flow rate on electronic excitation temperature. When increasing the tube spacing, the discharge is weakened, and the characteristics of the plasma parameters present a downward trend except N2(C3∏u) vibrational temperature. Increasing the voltage amplitude or the frequency of the power supply is beneficial to the enhancement of the discharge, but the influence on N2(C3∏u) vibrational temperature is small.In order to better understand the discharge mechanism of the surface dielectric barrier discharge and illustrate the regularity evolution of characteristic parameters of the plasma, an equivalent circuit of the asymmetric surface dielectric barrier discharge plasma generator under nanosecond pulsed and sine wave power is established based on the physical processes and experimental results, respectively. Firstly, the relationship curve between the plasma geometry and the voltage amplitude was derived in terms of high-speed camera images. Then, by virtue of matlab/simulink, the current, voltage drop across the discharge gap, air gap voltage, average electron density and temperature, plasma resistance and capacitance are obtained by solving the Kirchhoff’s voltage equation and electron continuity equation. It is shown that the average electron density and electron temperature could be calculated approximately by applying the variable resistance to simulate the discharge process, which reduces the use of switch function, and it is favor for the realization of the impedance matching and the improvement of the efficiency of power supply. When the current of the sine wave power discharge reach the maximum, the average electron density, electron temperature and resistance are 1.01×1016m-3,6.1 eV and 0.5MΩ, respectively. The resistance and capacitance decreases nonlinearly as the increase of the current intensity, while the electron temperature rises slightly. Under the effect of the nanosecond discharge, there exists the reverse discharge, and the electron density and electron temperature are 2.7×1018m-3 and 8.5eV, higher than that of sine wave power. The slope of the power supply takes important part in the discharge. As the voltage rate of rise is increased, the discharge occurs earlierly, and current in the first discharge increases but the second discharge current decreases slightly. The increase of the voltage rate of decrease is positive correlation with the second discharge, but the first discharge current decreases slightly... |
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