Effect of N2 and O2 Additions to CO2 on Extinction Limitation of Axial Gas Flow Arc

概要

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The arc extinguishing limitation, (dE / dt)lim, in a thermal re-ignition region was evaluated for CO2 and its mixtures with N2 and O2 at a concentration of 0.2 to study variation in (dE / dt)lim due to N2 and O2 additions. A progress effect on (dE / dt)lim did not necessarily emerge in any arc state but arose only in a specific arc state. Further consideration led to the essential facts that the emergence condition of the progress effect depended on the arc-core temperature at the instant of an interrupting current zero. In other words, admixing N2 with CO2 proved to produce an increasing effect on (dE / dt)lim, if the temperature composition in an arc-core cross-section at the current zero showed an axial temperature in a range from about 9 to 14kK. In contrast, mixture of O2 with CO2 was found to contribute to a distinct rise in (dE / dt)lim, if the arc temperature composition at the current zero revealed the axial temperatures below 10kK. This rise in (dE / dt)lim arose more pronouncedly with a lower axial temperature. The above-mentioned facts were explained, in terms of a temperature reduction factor showing a decay rate of an arc temperature with time.