Effects of Insulation Thickness on Flame Spread over Electrical Copper Wire with Applied AC Electric Fields

Effects of insulation thickness on flame spread over electrical copper wires with applied AC electric fields were experimentally investigated. The AC volrage and frequency varied in ranges of 0-5 kV and 10-1000 Hz, respectively. A one electrode configuration was used such that the electric potential was applied to one wire end and thus the infinite ambience could be a ground. The results showed that the flame shape and the tilting direction were significantly influnced by applied voltage and frequency. The flame spread rate decreased in an increase of insulation thickness as well as varied sensitively with applied votage and frequency. Additionally, the molten polyethylene (PE) experienced various dynamic behaviors such as dripping of molten PE, electrospray, di-electro-phoresis, and rotation of molten PE, essentially affecting the flame spread rate. These complicated phenomena were systematically analyzed and discussed.