Predicted results of a HID DC current lamp considering a P-1 radiation model

This paper presents a numerical model that can be used for designing and/or improving a high-intensity DC discharge lamp. For purposes of illustration, we present results for the plasma subregion considering a 10 A discharge in a mercury-argon mixture (91:9 mass concentrations) operating at 1.1 atm. Calculation is carried out for a simple geometry of lamp, which consists of spherical vessel and ellipsoidal electrodes with a 15 mm interelectrode gap. The steady-state transport equations for mass, momentum, and energy, Laplace's equation for electrostatic potential, Ampere's law for magnetic field intensity, the species continuity equation, and the P-1 radiation equation are solved simultaneously for a simple two-dimensional axisymmetric geometry. The buoyancy effect is introduced and the lamp is placed vertically with the anode at the top. We have found a maximum plasma temperature of 10 000 K and a maximum velocity magnitude of 6 m/s near the cathode surface. The values of maximum temperature and velocity are also predicted to be relatively high near the anode surface compared to the values calculated around the middle of the interelectrode gap.