M. Stambouli

Thermalization of the high pressure mercury lamp positive column during the warm-up phase

This work deals with the modeling of high pressure mercury lamp positive column thermalization. Because of the important pressure variation during the start-up phase, the discharge properties change fundamentally before the steady state is reached. For this reason the corresponding pressure range is split into three phases, namely the low pressure, intermediate and high pressure phases, in which interesting simplifications of the simulation can be obtained. A self-consistent collisional-radiative model is used to simulate the first phase. In the second, the model has been modified in order to include the significant reactions of this phase. Finally a LTE model describes the high pressure phase. Partial validation of the models are obtained from the study of the warm-up of a mercury lamp supplied under DC conditions. The results obtained are in good agreement with literature experimental data and, furthermore, allow the discussion of the validity limits for each model. >

Effect of a pulsed power supply on the spectral and electrical characteristics of HID lamps

Results of spectral and photometric measurements are presented for pulsed power operated high intensity discharges (HIDs). This investigation is related to the application of a pulsed power supply for pile driving of HID lamps. Specifically, we are interested in controlling the spectral response radiation of visible and ultraviolet (UV) lines for tertiary treatment of water using UV radiation. Simulations based on a physical model of the lamps were conducted. These results relate to the radial temperature, line intensity and electrical properties (voltage, power and conductivity). Good agreement has been found between the results of the simulations and the experimental findings.

Modeling the warm-up phase of a high-pressure-lamps lighting network

This work presents a study of the dynamic regime of a lamp-network interaction corresponding to the warm-up phase of a high-pressure mercury discharge lamp. The lamps behavior is described by a variable pressure model using the local thermodynamic equilibrium (LTE) concept. Indeed, this model covers the most interesting phase of the network dynamic regime, where discharge lamps appreciably impose their nonlinearity. We first analyze the electrical behavior of the discharge lamp in a single phase circuit, taking into account the ballast saturation. Then a micronetwork is studied and are show the influence of the discharges evolution on currents in phases and neutral conductors. Finally, from the results of the physical model, we set up a simple parametric modeling which reproduces the electrical behavior of the lamp during its warm-up phase. Such an approach can be useful for electrical engineers working on the discharge supply circuits at industrial frequency (50-60 Hz).

Integrating cylinder radiometry and photometry: Application to radiant flux and irradiance measurements

Abstract In this paper, we present the detail calculations of the indirect spectral irradiance E(λ) as a function of the spectral radiant flux Φt(λ) of a radiating source. This relation is used to predict the integrating cylinder irradiance for a given input radiant flux as a function of the geometrical parameters and reflectivity called “multiplier constant”. The radiation transfer within a cylindrical enclosure composed of three different surfaces, the inside circular surface and the two bases in the ends, has been examined. The configuration factor is introduced. Then all the configuration factors needed for our calculation have been given in analytical form.

Discrete ordinates method in the analysis of the radiative transfer in high intensity discharge lamps

This paper deals with radiation transfer in cylindrical high pressure discharges for which local thermodynamic equilibrium can be assumed. An S?N approximation (a set of N discrete directions) of the discrete ordinates method is used to solve the radiative transfer equation. A summary of the basic equations and numerical formulations is given in order to calculate the spectral intensities and then to evaluate radiative flux and net emission coefficient. Also, the net emission coefficient is described by a semi-empirical formula which contains terms representing the generation and absorption of radiation. The results are presented for a typical high pressure mercury discharge commonly used as a light source.

Experimental study of a mercury high‐pressure discharge in the course of its start‐up phase

This work deals with an experimental study of the start‐up phase of a mercury high‐pressure discharge. We demonstrate, by using electrical and spectroscopic measurements, that a steady‐state discharge can be said to be equivalent to a specific stage of the warm‐up phase if, for a given current, arc voltage together with several spectral line intensities are the same in both states. Subsequently, using these measurements we were able to: (i) determine the evolution of the electric field and the voltage drop at the electrodes in the course of a start‐up phase; and (ii) establish that the determination of the excitation temperature of Hg and Ar excited levels gives us a first indication concerning discharge thermalization and local thermodynamic equilibrium hypothesis limits.

Study of the influence of additive on the radiative properties of a HgTℓI high pressure discharge

This paper deals with radiation transfer in a cylindrical high pressure HgTlI discharge for which local thermodynamic equilibrium can be assumed. The discrete ordinates method (DOM) is used to solve the radiative transfer equation. Calculations of concentration profiles of all species have been performed using a parabolic temperature profile and a constant mercury/thallium ratio throughout the discharge tube. The influence of thallium in HgTlI discharges on the spectroscopic parameters such as the spectral intensity, the radiative flux and the net emission coefficient is studied. A comparison of the calculated thallium line shapes with the measured ones shows good agreement.

The experimental study of the current pulse duration on the HID lamps luminance

The general objective of this work consists in studying the influence of the current pulses duration on the electric and photometric behaviour of the gas-discharge high pressure mercury vapour lamps, intended particularly for the water treatment. With this intention we carried out a feeding system allowing providing the lamp a crenels of current with variable amplitude and duration of pulses. In this work we focused on the presentation of the feeding system carried out. We also present experimental measurements (voltage-arc, current, power, conductance and the luminance) of a 400W high pressure lamp coupled to its electronic power supply. These electric and photometric results highlight and evaluate the effectiveness of the currents pulses duration on the behaviour of the lamp conductance and the luminance of visible radiation.

Effect of a pulsed power supply on the ultra violet radiation and electrical characteristics of low pressure mercury discharge

This work deals with the application of a pulsed power supply for pile driving of a low pressure mercury discharge (LPD). The influence of the pulsed current power supply on the electrical properties and the spectral radiant flux emitted by a germicidal UV lamp has been investigated, both experimentally and theoretically. A Self Consistent Collisional-Radiative model SCCR is described to understand the behavior of the plasma characteristics operated in a pulsed mode. This model includes elastic and inelastic processes as well as ambipolar diffusion. The output gives the whole macroscopic plasma properties such as the electric field strength, the electron temperature, the energy transfers of the various collision processes and the radiation output. To evaluate the energy emitted in the UV bandwidth, a photometric system composed of an integrating cylinder, UV radiometer, a spectrograph and a CCD camera is mounted. This study provides a framework for the design of a pulsed current power supply which features single or multiple pulses superimposed on a low-frequency square wave. Reasonable agreement has been obtained between the experimental data and the results of calculations which take the above processes into account.

Effect of a pulsed power supply on the ultraviolet radiation and electrical characteristics of a low-pressure mercury discharge

The influence of a pulsed-current power supply on the electrical properties and the spectral radiant flux emitted by a germicidal ultraviolet (UV) lamp has been investigated, both experimentally and theoretically. A self-consistent collisional–radiative model has been developed and used to model the temporal behaviour of the plasma characteristics of the lamp operated in the pulsed mode. The model includes elastic and inelastic processes as well as ambipolar diffusion. The macroscopic properties of the plasma, including the electron temperature, electric fields, radiation and energy transfer due to various collisional processes, have been considered. To evaluate the energy emitted in the UV bandwidth, a photometric system composed of an integrating cylinder, a UV radiometer, a spectrograph and a charge-coupled device camera is mounted. This study provides a framework for the design of a pulsed-current power supply, which permits the generation of a single pulse or multiple pulses superimposed on a low-frequency square wave.