Arc Shape of High-Intensity Discharge Lamps: Simulation and Experiments

Abstract

A stationary compressible three-dimensional (3D) model of photothermal processes inside an arc tube of a high-intensity discharge lamp is developed on the basis of the finite element method. It takes plasma, electrodes, and the tube wall into account and enables simulation of acoustic phenomena. The temperature profile of the discharge arc is used as a marker for the emission of visible light. Complementary, experimental investigations are conducted at different modulation frequencies. A photodetector array is used to record 2D information about the light intensity distribution. The shape and length of the discharge arc are determined and compared to numerical results.

Backcoupling of acoustic streaming on the temperature field inside high-intensity discharge lamps

“…In the experiments it is set to a constant value that is just high enough to stimulate arc flicker. A more detailed description of the experimental setup can be found elsewhere [16]. Before the measurements the lamp is operated at stable conditions (α = 0) for at least 20 minutes to reach a stationary state.…”

“…Figure 4 shows the results of the experimental voltage measurements over the excitation frequency. The frequency deviation between the experimental and the simulation result of 4 kHz is related to the simplified geometry and uncertainties in the material properties [16,19]. Additionally, some boundary conditions, e.g.…”

“…To compare the temperature field of the simulation with experimental results, the light intensity distribution was recorded by a camera [16]. The left part of figure 6 shows the intensity distribution at stable operation conditions.…”