Experimental study on the discharge characteristics of a DC transferred arc twin torch system

The transferred arc twin torch system has attracted significant attention in fields such as coal gasification, metallurgy, and solid waste treatment due to its superior characteristics, including high temperature, high enthalpy, and high energy density. However, compared with the traditional axial-arc plasma torch, the large-area exposed arc of the transferred arc twin torch system renders the maintenance of stable discharge more complex. This work focuses on the DC transferred arc twin torch system and investigates the effects of nozzle structural parameters and discharge operating parameters on arc stability. The correlation between arc characteristics and both structural and operating parameters is established. Research shows that both straight-channel nozzles and backward-facing stepped nozzles are effective in stabilizing the arc. In contrast, the backward-facing stepped nozzle exhibits lower gas flow limits for discharge stability, weaker arc rigidity, a longer restrike period, as well as lower average discharge voltage and power. An increase in nozzle length or a decrease in nozzle diameter can enhance the constraint strength of the arc, increasing its rigidity, average length, and restrike frequency. This is beneficial for increasing the average voltage and reducing voltage fluctuations, but it also raises the minimum gas flow rate required for stable discharge. In addition, as the current increases, the rigidity of the arc also improves. Emission spectroscopy results indicate that the DC transferred arc twin torch system generated plasma with extremely high temperature. At a current of 140 A, the electron temperature could reach up to 1.88 eV, while the heavy particle temperature was approximately 21000 K, which makes the system suitable for high-temperature and high-enthalpy applications.