On the convective flow in Hg high pressure discharge lamps: Influence of tube geometry
- Univ. P. Sabatier, Toulouse (France). Centre de Physique des Plasmas et leurs Applications de Toulouse
Transport phenomena in electric arcs are responsible for effects of considerable importance for a stable operation of the device. In fact if the convection flow is unstable, undesirable phenomena appear and several discharge characteristics are affected. In the case of an atmospheric pressure discharge this flow is largely dependent of arc pressure and current as well as arc tube dimensions. In this paper the authors limit the discussion on the influence of the arc tube dimensions by using numerical simulation results. This simulation of arc properties is performed with a two-dimensional code. Herewith, mass, energy and momentum continuity time dependent equations are solved in order to calculate transport flows. Numerical resolution is done with a finite element semi-implicit scheme. It was found that stable laminar mono-cellular convection flow occurs at low values of tube diameter for a cylindrical burner. However, Reynolds number increases with tube diameter and thus a turbulent flow will appear up to a critical tube diameter value. In the proximity of this critical value a more complex convection multi-cellular flow pattern occurs. Energy losses by convection increase with tube radius. Furthermore, in the case of a wall stabilized discharge these convection losses are a small fraction of the total energy amount in the discharge. However, it was recognized that convection in some cases could affect lamp performances.
- OSTI ID:
- 178228
- Report Number(s):
- CONF-950612--; ISBN 0-7803-2669-5
- Country of Publication:
- United States
- Language:
- English
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