Measurement of radial temperature distributions of the blown CO₂ arcs under different conditions

In this paper, the radial temperature distributions of the blown CO₂ arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO₂ flows with different flow rates (50, 100 and 150 l min^-1) were created to axially blow the arcs burning in a polymethyl methacrylate (PMMA) nozzle. Discharges with different arc currents (200 and 400 A) were conducted in the experiment. The absolute intensity method was applied for a carbon ionic line of 657.8 nm to obtain the radial temperature profiles of the arc columns at a cross-section 1 mm above the nozzle. The calibration for the intensity of the C II 657.8 nm line was achieved by the Fowler-Milne method with the help of an oxygen atomic line of 777.2 nm. The highest temperature obtained in the arc center was up to 19 900 K when the arc current was 400 A and the CO₂ flow rate was 50 l min^-1, while the lowest temperature in the arc center was about 15 900 K when the arc current was 200 A and the CO₂ flow rate was 150 l min^-1. The results indicate that as the arc current increases, the temperature in the arc center would also increase apparently, and a larger gas flow rate would lead to a lower central temperature in general. It can also be found that the influence of the CO₂ flow rate on the arc temperature was much less than that of the arc current under the present experimental conditions. In addition, higher temperature in the arc center would cause a sharper temperature decrease from the central region towards the edge.