Philippe Teulet

The influence of Cu, Al, or Fe on the insulating capacity of CF3I

SF6 is widely used in electrical equipment as an insulating medium. However, SF6 is a serious greenhouse gas. CF3I is considered as one of its potential alternatives. This study verifies whether free metal particle (Cu, Al, or Fe) defects adversely affect CF3I insulation and investigates the incidence from different types and numbers of metal particles. This study is also devoted to calculating specific heat at constant pressure and electrical conductivity of CF3I–metal mixtures. The calculation results prove that with the increase of metal ions, temperature rises faster in the CF3I–Cu plasma or in the CF3I–Fe plasma than in the CF3I plasma without metal absorbing the same energy. The fast development of ionization can promote the increase of free electrons and the rise of electric conductivity. On the basis of the experiments and theoretical analysis, the influence of Cu and Al on the insulating capacity of CF3I is greater than that of Fe.

Thermophysical and radiation properties of high-temperature C4F8-CO2 mixtures to replace SF6 in high-voltage circuit breakers

C4F8-CO2 mixtures are one of the potential substitutes to SF6 in high-voltage circuit breakers. However, the arc quenching ability of C4F8-CO2 mixtures is still unknown. In order to provide the necessary basic data for the further investigation of arc quenching performance, the compositions, thermodynamic properties, transport coefficients, and net emission coefficients (NEC) of various C4F8-CO2 mixtures are calculated at temperatures of 300–30 000 K in this work. The thermodynamic properties are presented as the product of mass density and specific heat, i.e., ρCp. The transport coefficients include electrical conductivity, viscosity, and thermal conductivity. The atomic and molecular radiation are both taken into account in the calculation of NEC. The comparison of the properties between SF6 and C4F8-CO2 mixtures is also discussed to find their differences. The results of compositions show that C4F8-CO2 mixtures have a distinctive advantage over other alternative gases e.g., CF3I and C3F8, because the d...

Influence of metallic vapours on thermodynamic and transport properties of two-temperature air plasma

The metallic vapours (i.e., copper, iron, and silver in this paper) resulting from walls and/or electrode surfaces can significantly affect the characteristics of air plasma. Different from the previous works assuming local thermodynamic equilibrium, this paper investigates the influence of metallic vapours on two-temperature (2 T) air plasma. The 2 T compositions of air contaminated by Cu, Fe, and Ag are first determined based on Sahas and Guldberg–Waages laws. The thermodynamic properties (including mass density, specific enthalpy, and specific heat) are then calculated according to their definitions. After determining the collision integrals for each pair of species in air-metal mixtures using the newly published methods and source data, the transport coefficients (including electrical conductivity, viscosity, and thermal conductivity) are calculated for air-Cu, air-Fe, and air-Ag plasmas with different non-equilibrium degree θ (Te/Th). The influences of metallic contamination as well as non-equilibr...

Radiative properties of ceramic metal-halide high intensity discharge lamps containing additives in argon plasma

The lighting represents a consumption of about 19% of the world electricity production. We are thus searching new effective and environment-friendlier light sources. The ceramic metal-halide high intensity lamps (C-MHL) are one of the options for illuminating very high area. The new C-MHL lamps contain additives species that reduce mercury inside and lead to a richer spectrum in specific spectral intervals, a better colour temperature or colour rendering index. This work is particularly focused on the power radiated by these lamps, estimated using the net emission coefficient, and depending on several additives (calcium, sodium, tungsten, dysprosium, and thallium or strontium iodides). The results show the strong influence of the additives on the power radiated despite of their small quantity in the mixtures and the increase of visible radiation portion in presence of dysprosium.

Improvement of ceramic-halide high intensity discharge lamps: Study of the UV radiation that could be converted into visisible light

In the field of lighting and for devices such as big panels, leds remain less interesting compared with the high-pressure lamps which are preferred for their high illumination coupled to a correct IRC index and lifetime. For these lamps, the challenges consist in illuminating most efficiently in the visible spectral region and in reducing mercury inside the lamps. Among the solutions, we can put in additives having a high power radiation (calcium, sodium, dysprosium, thallium, and strontium), and\or find free mercury gases (mercury being usually mixed with pure argon). For such mixtures at high pressure, the radiative spectrum goes from UV to IR radiations. The UV radiations can be very important and could be absorbed and converted by phosphors in order to increase the visible light and reduce the skin diseases. Unfortunately, adding phosphors leads to expensive post-treatments. A theoretical study of the radiative spectrum seems more adapted and cheaper to estimate the radiation emitted in the IR, visible and UV regions. This radiative energy is often deduced according to simplified approaches1. Here, we propose a more accurate method, usually applied to evaluate the divergence of the radiative flux in thermal plasma modeling: the Net Emission Coefficient2. This method allows a good and rapid estimation of the total power emitted by the center of the lamp, by keeping a good description of the radiative mechanisms in the different spectral intervals (IR, visible and UV). The lamps we are studying work with a primary gas between 10-500 mbar, 5-40 mg/cm3 mercury, and metallic additives between 1 and 30 mg/cm3. The partial pressures are 200 mbar for Ar, 10 bar for Hg and 1 bar for metallic species with maximal temperatures around 5500K in the center of the lamp and plasma size of 1mm. We present the radiation emitted in the three spectral regions for different mixtures: 89%Hg-2%Ar-9% additives, the binary mixture 98%Hg-2%Ar often used in lamps, and a ficticious binary free mercury mixture at 11.2bar. The results show the radiation proportion emitted in each spectral interval (IR, visible and UV), and allow us to evaluate the UV part that can be converted in visible light. We also show the increase of the radiative power due to the presence of the metallic species and particularly in the visible and UV regions. The free mercury mixture is studied in order to evaluate the capacity of free mercury lamps to be good candidates.

Calculation of Photo-Ionisation Cross Sections and Radiative Recombination Rate Coefficients for CO and CO+ Molecules

A method based upon the weighted total cross section (WTCS) theory is proposed to calculate the photo-ionisation cross sections and the radiative recombination rate coefficients between the fundamental level of CO and the main electronic states of its corresponding ion. Total photo-ionisation cross sections and radiative recombination rate coefficients are determined from the calculation of elementary vibrational photo-ionisation cross sections. Transitions between CO+(X, A and B) and CO(X) are considered. Total photo-ionisation cross sections and recombination coefficients are computed in the temperature interval 500–15000 K.