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.