Diagnosis Of OH Temporal And Spatial Distribution In Atmosphere Dielectric Barrier Discharge By Laser Induced Fluorescence Technique

In this thesis, the asynchronous laser induced fluorescence (LIF) technique has been developed to characterize the OH temporal and spatial distribution in atmosphere He-H20(0.4%) needle-plate dielectric barrier discharge (DBD). The evolution of OH average relative density with the applied voltage was studied and the spatial distribution of emission spectrum and OH radical fluorescence was measured by ICCD camera to analyze the production mechanism of OH radical in DBD discharge.The main research results are as follows:(1) The needle-plate DBD system and humidifying adjusting system were established, and combined with the laser induced fluorescence diagnosis instrument to realize the OH radical diagnosis.(2) The relative fluctuation of OH radical density was measured by the asynchronous LIF technique in the DBD, and the results indicated that all the fluctuation was in the range of ±35% and nearly 90% sampling acquisition fluctuated in the range of ±15%, and relative fluctuation decreased with the increasing of the applied voltage, Therefore the ground state OH produced in AC DBD can be characterized by its average density via asynchronous LIF measurement.(3) Four different discharge patterns were observed when the applied voltage increased from 1.4 KV to 4.0 KV, and the voltage-current (U-I) waveform and ICCD images of the four discharge patterns indicated that four discharge patterns were related to negative barrier corona discharge, glow discharge, multi-glow discharge and streamer discharge, and introduced the discharge mechanism of four discharge patterns.(4) The evolution of OH average density with the applied voltage was studied by asynchronous LIF technique, the results indicated that the evolution of OH average density was also divided into four stages, the spatial distribution of emission spectrum and OH radical fluorescence was measured by ICCD camera to analyze the mechanism of OH production. The results indicated that the main mechanism of OH production in negative barrier corona discharge was the electron direct collision dissociation and in the other three discharge patterns the He metastable penning ionization was main process.(5) The efficiency of OH production per injection power was defined, and the evolution of efficiency of OH production with the applied voltage was studied, the results indicated that the corona discharge was the most efficiency discharge phase for OH production, and the streamer discharge was the lowest.