Investigation of temperature characteristics of multiphase AC arc by high-speed visualization

Abstract

The objective of the present study is to understand fluctuation phenomena in a multiphase AC arc as a heat source for material processing based on the high-speed visualization technique of the temperature field. The multiphase AC arc is one of the most attractive thermal plasmas which possess extremely high temperature, high chemical reactivity, rapid quenching capability, and selectivity of the reaction atmosphere in accordance with required chemical reaction. In particular, the multiphase AC arc has a strong advantage on higher energy efficiency compared with other thermal plasmas. Therefore, this heat source has been applied to innovative material processing such as in-flight glass melting. However, the temporal and spatial characteristics of the multiphase AC arc have not been clarified although these are essential to control the characteristics of the products such as particle size distribution, yields of the desired materials. The high-speed visualization of the temperature field of the multiphase AC arc was conducted at 1x10 4 fps as typical framerate to observe the dynamic behavior of the multiphase AC arc in millisecond time scale. An optical system including the band-pass filters was combined with the high-speed camera to observe particular line emissions from atomic argon with negligible emissions from thermal plasma. The obtained experimental results indicated that the temperature of the multiphase AC arc was around 1.0x10 4 K. The arc temperature fluctuated in the range from 0.6x10 4 to 1.3x10 4 K. Consequently, the arc temperature in the multiphase AC arc is sufficiently high to treat the refractory metals and/or ceramics powders. Furthermore, the obtained temperature was well-validated by the conventional spectroscopic method with high accuracy.

Investigation of Arc Behavior and Temperature Distribution Corresponding to Electrode and Phase Configurations in a Multiphase AC Arc

“…e distributions of emission intensity on two di erent wavelength were obtained on CCD by passing through the band-pass lters. e transmission lters of 675±5 nm and 794±5 nm were adopted to transmit the line spectrum of argon at 675.2834 nm and 794.8176 nm (Tanaka et al, 2017). Continuum emission passing through these lters was considered as negligible, because the intensity of the continuum emission is su ciently smaller than that of the line spectrum of atomic argon on the basis of spectroscopic measurement.…”

“…Recent studies on arc movement (Tanaka et al, 2011b) and consumption of electrode using a high-speed video observation method (Tanaka et al, 2016b;Hashizume et al, 2017) have been revealed. e measurement method for temperature distribution in millisecond time scale has been suggested (Bachmann et al, 2013;Tanaka et al, 2017;Okuma et al, 2018Okuma et al, , 2019.…”

Arc Behavior and Temperature Distribution in Water Thermal Plasma with Mist Generation

“…e arc temperature is closely related to arc voltage and reattachment process, which results from the arc uctuation (Wutzke et al, 1967;Trelles et al, 2007). Recently, a 2-D temperature measurement method using a high-speed camera and band-pass lters has been developed (Bachmann et al, 2013;Tanaka et al, 2017), which is based on the principle of the Boltzmann plot method.…”

Arc temperature measurement with microsecond spectroscopic measurement

“…Tanaka et al conducted a study in which they combined a high‐speed video camera with a spectrometer and used the two‐line intensity method to elucidate the dynamic behavior of a multiphase AC arc . However, with the Fowler‐Milne method, the particle number density calculated from Saha's thermoionization equation assuming LTE (local thermal equilibrium) is required; and, with the two‐line intensity method, the slope of a straight line is calculated from a two‐point plot and, consequently, slope accuracy is low.…”