Abstract
A simple model describing the plasma temperature, pressure and velocity distributions inside the nozzle during plasma arc cutting is developed. Temperature dependences of plasma properties are considered. Predicted and measured values of the plasma pressure inside the arc chamber are compared to validate the model. Calculations demonstrated that a substantial portion of the power dissipated inside the nozzle is radiated; the rest heats the plasma jet. The proportion of the power lost due to radiation increases with the arc current, length of the nozzle and gas-flow rate. The double-arcing phenomenon is hypothesized to result from the electrical breakdown of the gas at the nozzle's exit. Calculations of the electrical field at the nozzle's exit support this hypothesis.