Bulletin of the American Physical Society
75th Annual Gaseous Electronics Conference
Volume 67, Number 9
Monday–Friday, October 3–7, 2022;
Sendai International Center, Sendai, Japan
The session times in this program are intended for Japan Standard Time zone in Tokyo, Japan (GMT+9)
Session ET1: Thermal and Arc Plasma I |
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Chair: Shinichi Namba, Hiroshima University Room: Sendai International Center Hagi |
Tuesday, October 4, 2022 8:00AM - 8:15AM |
ET1.00001: Influence of charging in feedstock particles injected into modulated induction thermal plasma for nanoparticle synthesis with OML theory Yasunori Tanaka, Ryudai Furukawa, Yurina Nagase, Yusuke Nakano, Tatsuo Ishijima, Shiori Sueyasu, Shu Watanabe, Keitaro Nakamura This report investigated influence of electric charging in feedstock particles injected in modulated induction thermal plasma (MITP) for nanoparticle synthesis. Charging feedstock particles can affect heating efficiency and evaporation rate, nanoparticle formation. The electric charging effect in feedstock particles was calculated on the basis of orbital motion limited (OML) theory with thermionic electron emission and secondary electron emission. The developed model was adopted to "MITP+TCFF method" in which modulated induction thermal plasma provides a periodical changed temperature and gas flow fields with intermittent feedstock feeding for synthesizing large amounts of nanoparticles. The Si feedstock was assumed to be supplied during on-time of MITP. Results indicated that feedstock particles were electrically charged in negative just after injection, while the particles have positive charge due to electron emission processes, which influences heating effect. |
Tuesday, October 4, 2022 8:15AM - 8:30AM |
ET1.00002: Arc Temperature Fluctuation near Electrode of Diode-Rectified Multiphase AC Arc Manabu Tanaka, Junjie Chang, Yuki Takemoto, Takayuki Watanabe, Tsugio Matsuura, Tsuguo Ueda, Hideki Touzaki, Juan P Trelles, Masaya Shigeta Diode-rectified multiphase AC Arc (DRMPA) has been developed to solve the electrode erosion of conventional multiphase AC Arc (MPA). Temperature fluctuation near the electrode in MPA or DRMPA has not been clarified due to its measurement difficulty owing to strong continuum emissions, while the understanding its fluctuation is crucial to understand electrode phenomena. In the present work, a high-speed camera system with band-pass filters (BPF) was successfully established to visualize fluctuated arc temperature field near electrode with consideration of both line emissions and continuum emissions. Preliminary measurements of optical emission spectroscopy and theoretical calculation of emission coefficients from the argon arc were performed to select the suitable BPFs carefully. The BPFs of 440 ± 5 nm and 480 ± 5 nm were finally selected as most suitable BPF combination for argon arc near the electrode. The obtained experimental results indicated that the arc temperature near the electrodes fluctuated in the range from 15,000 K to 20,000 K. The arc temperature fluctuation in the conventional MPA is more significant than that in DRMPA due to stronger arc swinging motion in MPA. DRMPA is expected to be applied to various material process due to the higher arc temperature and larger high-temperature area than the MPA. Obtained remarks can serve as a reference for the mechanism of electrode erosion and the industrial application of DRMPA. |
Tuesday, October 4, 2022 8:30AM - 9:00AM |
ET1.00003: Computational Studies of Thermal-Plasma-Induced Turbulence on Nanopowder Generation and Sustained Arc Discharge Invited Speaker: Masaya Shigeta Thermal-plasma-induced turbulence (TPIT) which appears and affects thermal plasma applications is discussed based on computational studies. A demonstrative simulation was performed for Si nanopowder generation in a turbulent-like flow induced by an Ar thermal plasma jet. The model described nanoparticles' collective growth by nucleation, condensation, and coagulation and transport by convection, diffusion, and thermophoresis in microsecond to millisecond time scales. The computation results showed that the plasma jet formed nonuniform thermofluid fields and induced multiscale vortices not only near but also far from the plasma jet, and the nanopowder collectively grew up and diffused outside the plasma region. The larger size regions coincided with smaller number density regions, which indicated that simultaneous coagulation decreasing particle number played an important role. A TPIT in a sustained SF6 arc discharge was also simulated by a simulation code named PLASTIPC (Plasma All-Speed Turbulence with Implicit Pressure Code) which was capable of capturing plasma-induced hydrodynamic instability leading to turbulence transition, treating subsonic and supersonic flows at all-speed range, and achieving numerically stable computation with a large increment of time steps even in such an extremely complex thermofluid system where hot plasma and cold nonionized gas co-exist. The computation results showed that the SF6 arc plasma was constricted with high temperature over 20,000 K, but the ambient nonionized gas had low temperature below 1,000 K. The arc plasma region exhibited small Mach numbers indicating an incompressible and subsonic flow. The ambient nonionized gas formed a compressible flow in Mach number > 0.3 with island-like supersonic flow zones in Mach number > 1.0. The intermittent backflows and forward flows produced a turbulent-like state. |
Tuesday, October 4, 2022 9:00AM - 9:15AM |
ET1.00004: Analysis of Amount of Metal Vapor Affected by Welding Speed in TIG Arc Welding Yusuke Nemoto, Masahiro Takagi, Honoka Morishita, Yuki Suzuki, Zhenwei Ren, Gustilo C Reggie, Toru Iwao In TIG welding, the anode is melted by the heat of the arc. Craftsmen change the welding speed according to the condition of anode. This technique is difficult and complex. However, the number of TIG craftsmen in Japan is decreasing. Thus, digital transformation of TIG welding is required. In this research, the amount of metal vapor affected by welding speed was analyzed. Specifically, the arc was analyzed under consideration of the movement of welding torch using three-dimensional electromagnetic thermal fluid simulation. In addition, thermal conductivity and specific heat were considered in the heat transfer between arc and anode. As a result, the amount of metal vapor decreased with increasing welding speed. This is because the heat input to the anode decreases with increasing welding speed. In addition, the arc temperature above the anode surface was maintained when the anode was at melting point. This is because latent heat of fusion was also considered in the heat transfer. Therefore, it is possible to analyze the melting of the metal vapor and the anode when the welding speed changes. In the future, arcs with transient changes in welding speed and applied external magnetic field plays an important role for the digital transformation of TIG welding. |
Tuesday, October 4, 2022 9:15AM - 9:30AM |
ET1.00005: Arc Temperature Measurement with High-Speed Camera Based on Continuum and Line Emissions in Argon-Nitrogen Free-Burning Arc Yuki Takemoto, Manabu Tanaka, Takayuki Watanabe 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. |
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