Theoretical and numerical studies of breakdown phenomena triggered by microparticle in nitrogen gaps

Abstract

This paper studies microparticle-triggered breakdown phenomena in mm-scale nitrogen gaps based on theoretical analysis and numerical simulation. Secondary electron and field emission contributions are both considered when predicting the microparticle-initiated breakdown voltage. In the present model, the ionization coefficient of the microscale discharge is modified to recognize the significant reduction in the number of collisions that occurs when a microparticle is present. The theoretical analysis indicates that small particles have little influence on the gas-gap breakdown voltage unless field-emission effects are dominant. However, when large microparticles (radius 50 μm) are present, a significant decrease (more than 20%) in the minimum breakdown voltage can be observed regardless of the particle position in the gas gap. Therefore, one should endeavor to exclude large microparticles from the discharge process. A fluid model is then used to simulate the microparticle-initiated breakdown process in a gas switch. The microparticle radius is 10 μm and the distance between the microparticle and cathode is 1 μm. It can be found that the electrode–particle microdischarge generates regions of high-density plasma that finally trigger main-gap breakdown when a voltage of 2.5 kV–3.5 kV is applied. The calculated results are consistent with our theoretical analysis. This paper provides a quantitative research method to evaluate the influence of microparticles on gas breakdown and contributes to improving gas-switch insulation performance.

Review of the gas breakdown physics and nanomaterial-based ionization gas sensors and their applications

“…Advanced studies describing changes in the secondary electron emission and field enhancement factors caused by the material properties of electrodes, such as morphology and roughness, are expected to provide a generalized universal theory. Although the field emission effect is a dominant factor to initiate the breakdown for small gaps, the effect of microparticles (or even viruses and bacteria) suspended in the discharge area should not be overlooked because they enhance the electric field between the microparticles and cathode in mm-scale N 2 gap discharge [126]. Recent studies have reviewed the detailed theoretical and experimental works focusing on the description of field-emission-driven microscale gas breakdowns [127,128] and contributions of thermionic and space-chargelimited emissions [129].…”