Arc Temperature Measurement with High-Speed Camera Based on Continuum and Line Emissions in Argon-Nitrogen Free-Burning Arc

Temperature in thermal plasmas is one of the important parameters that determine transport and thermodynamic properties. Arc temperature measurement method that combines a high-speed video camera (HSVC) with a pair of band-pass filters (BPFs) had been developed. However, the relatively low spectral resolution of the HSVC system leads to measurement errors. In this study, both line and continuum emissions were considered to solve the afore-mentioned problem of HSCV imaging technique. Nitrogen is a promising gas that is safe, inexpensive, and easily accessible to industry. Free-burning arcs generated under atmospheric pressure of nitrogen (N₂)-argon (Ar) was targeted. The error of the calculated temperature was derived theoretically, and an important factor in determining the combination of BPFs was revealed. Combination of BPFs which transmit 480±5 nm and 500±5 nm was employed in 50vol%N₂-Ar and 70vol%N₂-Ar arc according to this factor. The temperature calculated with the new method was 19,800 K at 2 mm from the cathode tip for 70vol%N₂-Ar arc. In contrast, the calculated temperature with consideration of only line spectrum was 17,900 K. Obtained results indicates that the new method with the consideration of both line and continuum emissions improves the measurement accuracy.