| Compared with volumn DBD, surface DBD is more likely to produce a large area plasma layer, and control air flow distribution in the boundary layer. Surface DBD has a bright prospect in the field of material surface treatment, active flow control and biomedical application in recent years. Discharge mode transformation mechanism and uniform control are new hotspots of surface DBD. Emission spectroscopy and high-speed photography are used to analyze the surface DBD combined with digital image processing and numerical simulation. The main contents are as following:1. A surface DBD actuator and optical diagnosis system are established, a synchronous trigger control system with 10 ns delay and light jitter is designed to capture the transient discharge.2. The influence of different parameters on the emission spectroscopic, electron excitation temperature, rotational and vibrational temperature characteristic by using spectroscopy and voltage-current detection. The results show that:the electron excitation temperature is no big change in the axial direction, and the maximum appear at the edge of exposed electrode in the radical direction. The electron excitation temperature, rotational and vibrational temperature of O increases with increasing of peak voltage.3. The radical propagation and discharge modes transformation are researched by using ICCD camera. Two different discharge modes presented in positive and negative going cycles: filamentary discharge and diffuse discharge. Emission intensity and temperature characteristics of two discharge modes can be compared by the method of time-resolved spectroscopy. The reason of discharge asymmetry of surface DBD is analyzed. The results show that:high energy electron density in filamentary discharge channel is higher than that in diffuse discharge. The rotational temperature of N2 decreases with filamentary discharge transforming into diffuse discharge. Discharge asymmetry is ascribed to charges accumulated on the dielectric layers.4. The discharge area can be detected by the sum of pixels after extracting threshold. Gray frequency distribution curve can be used to the quantitative analyze discharge uniformity at different parameters. The influence of discharge parameters, gas components and flow rate on discharge mode is discussed. The change of frequency does not find any inhibition or promotion effects on the discharge transformation. The penning effect in noble gas has a greatly effect on the discharge uniformity. The flow has a little effect on the inhibition of filamentary discharge. Ceramic with bigger permittivity is helpful for producing of uniform discharge.5. Based on the 2D fluid model of surface DBD in air at atmospheric pressure, the evolution of charge density in dielectric and electric field can be analyzed. The discharge asymmetry can be validated. Effect of applied voltage, dielectric and electrode configuration on surface DBD in air is researched. The results show that:the charges originate from primary electron, the electron avalanche results in the change of electric field, and the maximum of electron density and electric field appears in the same point. The maximum of electron density can reach to 3.6x 1016 m-3 in the reverse voltage phase. The discharge asymmetry is attributing to the large sum of electron along the dielectric plate. The increase of secondary electron emission coefficient reduces the gas voltage. Sliding surface DBD is helpful for the production of plasma layer with large area. |
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