Study on arc and flow characteristics of a non-transferred DC steam torch

A turbulent magnetohydrodynamic model is proposed to predict the steam plasma flow inside a direct-current and non-transferred torch. The continuity, momentum, energy and current continuity equations as well as the turbulence model are expressed in the cylindrical coordinate system and numerically solved with a finite volume method. The operation conditions of mass flow rate ranging from 3?g/s to 8?g/s and current varying between 125 A and 200 A are systematically analyzed via a proposed numerical approach. An explicit determination of the arc root location and the maximum current density of the cathode spot via the experimental measurements is demonstrated. The maximum current density at cathode is found to be on the order of 107 A/m2. A least square fitting approach is then employed to analyze the experimental and numerical results where the quantitative formulation of the arc and flow characteristics in terms of the arc current and mass flowrate are presented. The main arc length falls in the range between 220 mm and 330 mm. At the torch exit, the mean gas temperature is predicted to be between 7.5 kK and 10 kK, the mean axial velocity varies from 750 m/s to 2 km/s and the mean azimuthal velocity is found between 160 m/s and 360 m/s. ? 2021 The Chinese Institute of Engineers.