Properties of air–aluminum thermal plasmas

Abstract

We present the calculation and the main results of the properties of air–aluminum thermal plasmas, useful for complete modelling of arc systems involving aluminum contacts. The properties are calculated assuming thermal equilibrium and correspond to the equilibrium composition, thermodynamic functions, transport coefficients including diffusion coefficients and net emission coefficient representing the divergence of the radiative flux in the hottest plasma regions. The calculation is developed in the temperature range between 2000 and 30 000 K, for a pressure range from 0.1 to 1 bar and for several metal mass proportions. As in the case of other metals, the presence of aluminum vapours has a strong influence on three properties at intermediate temperatures: the electron number density, the electrical conductivity and the net emission coefficient. Some comparisons with other metal vapour (Cu, Fe and Ag) properties are made and show the original behaviour for Al-containing mixtures: mass density at high temperatures is low due to the low Al atomic mass; high electrical conductivity at T < 10 000 K due to low ionization potential (around 2 V less for Al than for the other metals); very strong self-absorption of ionized aluminum lines, leading to a net emission coefficient lower than that of pure air when T > 10 000 K, in contrast to copper or iron radiation.

Analysis of the characteristics of DC nozzle arcs in air and guidance for the search of SF6replacement gas

“…[16] and Gleizes, e.g. [17,18] and, most recently, by Wang et al [19]. The most important transport property for turbulent arc modelling is the electrical conductivity.…”

“…The standard k-epsilon model computes the length and velocity scales of turbulence, and thus the eddy viscosity, based on two partial differential equations, one of which for the turbulent kinetic energy per unit mass, k, and the other for the turbulence dissipation rate, . The corresponding governing equations are given below (16) 17where is the generation rate of the turbulence kinetic energy which is given for axisymmetric arc by (18) The length and velocity scales of turbulence are respectively defined as (19) and the eddy viscosity is given by (20) The default values of the turbulence parameters for the standard k-epsilon model are: , , ,…”

Pressure Rise in Electrical Installations due to Internal Arcing in CO2 as Insulating Gas

“…For collisions in pure air and CO 2 plasmas, the collision integrals provided in Refs. [1,13] have been used. For the mixtures between CO 2 and air, the collisions between carbon and nitrogen species are treated using the Lennard-Jones potentials for neutral-neutral interactions, polarisation potentials for neutral-ion interactions and screened Coulomb potential for charged-charged particles.…”

A Review of Progress Towards Simulation of Arc Quenching in Lightning Protection Devices Based on Multi Chamber Systems

“…It is possible then to precompute all thermodynamic properties and store in the form of lookup tables as described in ( [5][6][7]). For simplicity, electrode erosion and ablation of wall material were neglected, making it possible to consider pure air arc discharge.…”