M. Konrad

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

Processes and properties of electric arc stabilized by water vortex

Experimental investigation of an electric arc stabilized by a water vortex was carried out in a DC arc plasma torch for the power range 90-200 kW. Volt-ampere characteristics of the arc as well as the power balance were determined separately for the part of the arc column stabilized by water and for the remaining part between the nozzle exit and the external anode. The temperature of arc plasma close to the nozzle exit was determined by emission spectroscopy. Negatively biased electric probes in the ion collecting regime were used for determination of the plasma flow velocity. The measured temperatures up to 27000 K, and velocities up to 7 km/s are higher than the values commonly reported for plasma torches with DC arcs stabilized by a gas flow. Mass and energy balances within the arc chamber were determined from the experimental results. The radial transport of the energy by radiation was identified as a decisive process controlling the arc and plasma properties. The balance of radial energy transport was studied. The ratio of energy spent for evaporation of the water to the energy absorbed in the evaporated mass is very low in the water stabilized arc. This is the principal cause of high plasma temperatures and velocities found by the measurements.

Production of high quality syngas from argon/water plasma gasification of biomass and waste.

Extremely hot thermal plasma was used for the gasification of biomass (spruce sawdust, wood pellets) and waste (waste plastics, pyrolysis oil). The plasma was produced by a plasma torch with DC electric arc using unique hybrid stabilization. The torch input power of 100-110 kW and the mass flow rate of the gasified materials of tens kg/h was set up during experiments. Produced synthetic gas featured very high content of hydrogen and carbon monoxide (together approximately 90%) that is in a good agreement with theory. High quality of the produced gas is given by extreme parameters of used plasma--composition, very high temperature and low mass flow rate.

Experimental investigation of energy balance in plasma arc cutting process

The present paper describes the power balance of the arc cutting process provided by a plasma torch with steam working medium. The work was concentrated on definition of different power terms including power input as well as effective power utilization and losses as a function of plasma gas flow rate. The work was mostly experimental. The results have shown around 20% of total available power is utilized for material cutting and removing for the studied conditions.

Experimental investigation of hot gas mixture free jet

The distribution of mass fractions of individual species in the working gas mixture is computed, and the influence of radial component of velocity and of turbulence on this distribution and on the velocity field in the cross-section of the jet is studied. The jet is generated by a hybrid water-stabilized are torch. An admixture of argon is added at the input of the are heater.

Powder particle penetration into steam-argon plasma jet and its relation with particle parameters

Interaction of Al2O3+3% TiO2 particles of diameter in the range 50÷63 μm with the plasma jet generated by de arc plasma torch with hybrid water-argon stabilization was experimentally studied. The plasma jet and particles in the feeding region were photographed by a fast shutter CCD-camera. At spraying distance the particle velocities, temperatures, and fluxes were measured by spray diagnostic system DPV-2000. Relationship between the particles injection parameters, the way of penetration into plasma jet, the particle flux, velocities, and temperatures were investigated at different feeding conditions as well as plasma jet properties. The distribution of temperatures and velocities in particle spray have similar character, the particle flux is influenced by carrying air flow rate and the way of injection. The feeding distance has substantial effect on particle velocity, at higher feeding distance the increase of argon flow rate does not increase particle velocity.