Two-temperature, two-dimensional fluid modelling of mercury plasma in high-pressure lamps

This paper deals with a two-temperature, two-dimensional modelling of a mercury high-pressure plasma stabilized by walls. We consider here a plasma composed of neutral particles, singly ionized positive ions and electrons. Both electron and heavy particle energies are supposed to follow Maxwell distribution functions at different temperatures. Moreover, the electrons were supposed to be carried by the heavy particles in their laminar convection movement. Hydrodynamic conservation equations are then solved by using a 2D semi-implicit finite element scheme. After validation the model is used to discuss deviations from thermal equilibrium due to external arc parameters such as arc current and pressure. These deviations are expressed as differences between electron and heavy particle temperatures. Our results confirm quantitatively for the first time the existence of thermal equilibrium deviations in such types of discharge. These deviations could be significant in many cases, especially when current or pressure is relatively low. Furthermore, we show that, in such types of discharge, the hot core is always closer to thermal equilibrium than the outer discharge jacket.