Numerical Simulation And Experimental Research On Physical And Chemical Characteristics Of Gliding Arc Discharge

Gliding arc discharge is a low-temperature plasma with high energy efficiency, electron temperature and density and has broad application prospects in the field of environment and energy. Although numerous industrial applications have been attempted, the physical and chemical mechanisms governing the gliding arc evolution are not yet accurately and comprehensively understood. In this dissertation the physical and chemical properties of gliding arc are researched based on numerical simulation and experiments. The main objectives of the current research included as following:(1) The arc temperature field, electric field and size of conducting zone of gliding arc plasma are important parameters to determine temperature and density of the electrons, chemical reactions rates and energy efficiency. Electrical parameters of a 50Hz ac gliding arc discharge were measured at two gas flow rate conditions, 1.43L/min and 6.42L/min. An instantaneous model which was used to describe the energy transfer of gliding arc discharge was simplified by using an approximate expression for the electrical conductivity and diffusivity of plasma, which raveled out the moving boundary in the gliding arc simulation resulted by variation of arc structure. The current density, electric field, dynamic temperature field and the structure of ac gliding arc was calculated. The electric field strength from the simulation result of the model was in agreement with the experimental data. According to the calculational result, the temperature in the axis of arc reached as far as 5700-6700K. It showed gas flow directly affected the arc structure and current density, thus affected the electric field strength and temperature distribution. The electric field strength increased firstly and then decreased during a discharge period.(2) A nonlinear model of ac gliding arc discharges in atmosphere-pressure is developed based on the combination of the transient Elenbaas-Heller model and Maxwell's equations. According to the calculation results of discharge parameters, the self-magnetic properties of an ac gliding arc discharge is investigated. The numerical results indicate that the increase in the gas flow rate could change the evolution of the magnetic field. The conjunct effect of gas flow and self-magnetic field determines the arc column structure. Zones with smaller arc radius and larger axial curvatures in the plasma region have larger local magnetic field intensity and self-magnetic pressure, which accelerates the instability of discharges.(3) The electron temperature, electron density and degree of non-equinibrium are the important parameters that characterize the thermodynamics properties of gliding arc. According to the Stark broadening of the AlⅠ396. 1nm in a high electric current the distribution of the electrone density along the axis of the reactor is obtained. A transient two-temerature model is used to described energy transfer of the plasma discharge. The electrode density can achieve at 1021～1022m-3 orders of magnitude under the simulation conditions. The evolution of the electrode density is consistent with the experimental results. The electron temperature is in the range of 1.3～1.8eV in the middle 60% of a discharge cycle and first decreases and then increases, which is in agreement with results of the formula from literature. The development trend of the non-equilibrium degree of plasma is similar with that of the electric field strength. The increase of the gas flow rate could not evidently increase the non-equilibrium degree.(4) A mathematical model describing the chemical-reaction kinetics for gas-liquid gliding arc discharge is developed based upon assumed temperature profiles and chemical reactions. The distribution of OH from simulation agrees with the results from optical emission spectroscopy. The results indicate much higher temperature is in favor of the production of OH. The formation of the OH first increase and then decrease along the axis. The model can accurately predict the production of H2O2 and H2. Increasing the water flow rate leads to higher H2 and H2O2 production at fixed inlet oxygen carrier flow rates.(5)Using butyric acid solution as objective pollutant, the influences of the system parameters on the degradation of wastewater are studied. The respective combination of H2O2 and TiO2 photocatalytic with gliding arc are researched. The results shows a higher oxygen flow rate can promote the degradation of organic contamination. When the concentration of the TiO2 is 0.5g/L, the synergistic effect becomes most significant. Increasing the amount of H2O2 could improve degradation rate.