Numerical Investigation of Supersonic Hybrid Argon–Water-Stabilized Arc for Biomass Gasification
This paper presents a numerical simulation of temperature and flow fields in the discharge and near outlet regions of the hybrid argon-water-stabilized electric arc. The calculations for an argon mass flow rate of 0.450 g ldr s-1 reveal the transition from a transonic plasma flow for 400 A to a supersonic one for 600 A with the maximum Mach number of 1.57. The comparison with available experimental data for 400 A shows satisfactory agreement.
Properties of Hybrid Water/Gas DC Arc Plasma Torch
A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow was investigated. This hybrid water/gas stabilization offers the possibility of adjusting plasma jet parameters within a wide range from high-enthalpy low-density plasmas typical for liquid stabilized torches to lower enthalpy higher density plasmas generated in gas stabilized torches. The torch was operated at an arc power from 22 to 130 kW with an exit centerline plasma velocity from 2 to 6.5 km/s and a plasma temperature from 14 000 K to 22 000 K. Moreover, gas flow in the cathode part protects a cathode tip and thus a consumable carbon cathode used in water torches could be replaced by a fixed tungsten cathode. The characteristics of the electric arc with combined gas/water stabilization were measured and the effect of gas properties and flow rate on plasma properties and gas-dynamic flow characteristics of the plasma jet were studied for argon, and mixtures of argon with hydrogen and nitrogen
A numerical solution of the Stefan problem
A two-dimensional Stefan problem is solved for a prism and a cylinder by approximating the enthalpy formulation of the problem byC0 piecewise linear finite elements in space combined with a semi-implicit scheme in time. The numerical integration in space makes the scheme easy to implement.