Analysis And Optimal Design Of Gas Flow Field For Triggered Spark Gap Switch

As a high-velocity and high-current switching device, the spark gap switch has been widely used in the high-power pulse systems, in which the requirement of high voltage, high repetition rate, low jitter and short delay time is always required. However, sometimes, prefire happens because of the remaining heat and charged particles, which worsens the reliability of the spark gap switch. Applying gas flow is generally considered as a simple and effective method to impede the prefire. The performances of the spark gap switch, especially the reliability, are significantly influenced by the gas, gas pressure, flow rate, flow field distribution and so on. For the gas, gas pressure, flow rate of the gas, there are a large amount of researches related on the influence of these parameters on the characteristics to the switch. However, there are no literatures reporting the research on the flow field distribution of the gas, gas flow state till now.Firstly, this thesis theoretically analyses the effect of the cooling gas on the characteristics of the spark gap switch. Then the reliability of the switch is experimentally measured. Based on the experimental results, a conclusion that prefire happens for the switch even blowing high gas flow is drawn. This is believed to be caused by the lack of optimization design. After that, a widely used commercial CFD software-FLUENT is used to simulate and analyze the flow field and distribution of inner velocity of the cooling gas. How to build and mesh the geometry modeling of the spark gap switch with Gambit is disclosed. Standard k ?εmodel and 3 dimensional steady flow are utilized in the simulation. From the simulations, it can be found that the flow field near the two main electrodes is a comparative parallel flow, but circumfluence and vortex exist in dead corner. These simulated results will greatly help to analyze the effect of the cooling gas on the performances of the switch, optimize the structure design and improve the performance of the switch.Based on the analysis of the results, a series of structural optimization are carried out. The effects of structural parameters, such as the distance from the nozzle to the center of the electrodes, the shape of the nozzle and the angle between inlets and outlets have been studied, and the results are given. In order to further improve the uniformity of velocity distribution near the electrodes and to make the gas expel from the switch easily, a method of smoothing and enlarging the outlet is proposed. The simulated results show that this method can improve the uniformity of the velocity distribution near the electrodes and minish the circumfluence. Furthermore, the effects of three gas passages and single passage are also analyzed in this thesis, the result shows that the export velocity of gas increases although the velocity fluctuation still exists, which is beneficial to the stability of the switch.