Uhrlandt, Dirk

A pre-study of free burning arcs between carbon electrodes for potential use in gasification processes is presented. Free-burning arcs offer the potential to be used without additional gas feed or significant changes to gas flows in established gasification systems as well as with minimal cooling requirements for improved energy efficiency. Direct current (DC) arcs with currents up to 200 A and power levels up to 40 kW have been operated in molecular gas mixtures of H2, CO and CO2.

The data correspond to the results of modelling studies of DC electric arcs at a current of 2 A in air with admixture of copper metal vapour. Experimental findings are used to adjust input parametrs of the model in order to achieve a good match. The simulations are performed strating with a discharge burning with a minimum gap length of 30 µm for a physical time of 11 ms. Then, the separation of the electrodes is followed for further 51 ms and the discharge gap is increased up to 3 mm. The comparision of experimental and modelling data is based on the measured arc voltage.

The dataset contains results of a unified one-dimensional model of an arc plasma in air dominated by copper metal vapour. The plasma is generated between copper electrodes. The model resembles the microarcs that occur at low-voltage and low-current conditions in switching devices during a contact separation. Data concerning the plasma parameters, including electric potential, temperatures of electron and heavy particles, number densities of charged and neutral species are provided as tables.

In this work we present for the first time a unified model of a low-current short-length arc between copper electrodes. The model employs one-dimensional fluid description of the plasma in argon and copper vapour at atmospheric pressure and the heat transfer in the electrodes made of copper. The solution of the particle and energy conservation of electrons and heavy particles is coupled with the solution of the Poisson equation, from which the self-consistent electric field is obtained. The operation of the non-refractory cathode is based on thermo-field emission.

Recent research of gas metal arc welding (GMAW) has proven that the sheath voltage dominates the total voltage fall in the current circuit and delivers most of the energy, which is finally transferred to the wire and the weld pool. This data set provides the results for droplet temperatures and the energy delivered to the wire anode in comparison with the sheath voltages. These quantities have been studied experimentally for a typical pulsed GMAW process in the one drop per pulse mode for mild steel under Ar with 2.5% CO2 with different peak currents from 350 to 650 A.

The relation between the voltage and the arc length in gas metal arc welding (GMAW) is an important characteristic. It depends on a complex distribution of the electric conductivity along the current path and does not depend on the arc length only. Based on electric measurements and the arc length determination from high-speed arc images, a simplified electrical model is introduced for a pulsed GMAW process. It shows the relation of voltage, current, arc length and free wire length and considers also their temporal evolution during the process in particular during the high-current phase.