Investigation of the influence of buoyancy on gas convection of a horizontal xenon short arc lamp through 3D numerical simulation

When operating a xenon short arc lamp, tungsten vapour that evaporates from the electrodes is transported by gas convection to blacken the inner bulb wall. Since this reduces the output light intensity and increases the risk of lamp breakage, it is crucial to thoroughly understand the factors that govern gas convection to optimally control it to reduce blackening. Gas convection is complex, especially in horizontal lamps, because it is strongly affected by buoyancy. This study used 3D numerical simulation to investigate buoyancy's influence on the gas convection of a horizontal xenon short arc lamp, which directly affects the blackening location. Gas convection, especially in the low flow velocity region, was strongly affected by the buoyancy, whose strength was mainly determined by the anode surface temperature. The gas convection in turn affected the bulb wall temperature and the W vapour transport and was reflected in the blackening location. This result indicates that the surface temperature of the anode, which was determined by the energy balance between the gas and anode, also affected the blackening location. Therefore, the emissivity of the anode surface was an important factor controlling the horizontal lamp's gas convection.