Radiative transfer calculation in SF₆arc plasmas using partial characteristics

Abstract

The partial Characteristics of the radiation which correspond to partial sources and partial sinks of radiation along a given direction, were calculated for a SF, arc plasma between 3 000 and 30000 K. These partial characteristics allow rapid calculation of the 3 D radiative transfer in this type of plasma. The method was applied to several simple cases and showed the validity limits of the use of a net emission coefficient in the modelling of the arcs. It was shown that, to calculate the radiative transfer and the temperature in the hot regions, the use of a net emission coefficient is valid when the plasma is approximately isothermal. In the case of strong temperature gradients in the hot regions, the net emission coefficient depends strongly on the chosen plasma thickness whose value is difficult to estimate.

Equation of state driven radiative models for simulation of lightning strikes

“…retaining terms up to O(ε 8 ), substituting into equation (37), and simplifying, two expressions are obtained, 39…”

“…Lightning strikes last for O(100) ms, producing currents of O (10) kA in pulses lasting for O(100) µs 1 . The resulting ionisation generates magnetic fields, coupled to the lightning arc through Joule heating and the Lorentz force, and this injects heat into the plasma, increasing the temperature by 30 kK over the first few microseconds 2 .…”

“…The simplest approximate solution is the net emission coefficient (NEC) introduced by Lowke 9 , which considers only the radiation emitted by the plasma and, in its simplest form, all self-absorption is neglected. Despite its simplicity it has been found to produce good predictions for the volumetric radiative power in the hottest parts of the plasma, but is less accurate near boundaries or in regions of high pressure 10,11 . It is implemented by e.g.…”

State of Art and Challenges for the Calculation of Radiative and Transport Properties of Thermal Plasmas in HVCB

“…Due to the complexity of this equation, several simplifying approaches have been developed during the last decades such as the method of the net emission coefficient (NEC) initially proposed by Lowke and first calculated for SF 6 by Liebermann and Lowke [14,15], then by Aubrecht and Barlova or Gleizes et al [16,17]. In order to treat efficiently the radiative transfer in the middle or cold regions, the P1-Model or discrete ordinates methods are often preferred using grey body approximation or Mean Absorption Coefficients (MACs) [18][19][20][21][22]. Then, due to rise of the computer's capacity, some works have been developed on pure SF 6 in order to perform an exact calculation of the radiative transfer equation with a very fine description of the spectrum, evaluating the accuracy and the validity of the simplified methods by comparisons.…”

Effects of radiative transfer modelling on the dynamics of a propagating electrical discharge

“…The accuracy of this very simple approach has been studied in Refs. [12,24], and it is generally recognized that it can predict quite accurately radiative volumetric power and temperature level in the hottest parts of the plasma, but fails to predict radiation absorption in the boundaries and wall radiative fluxes. It remains however very popular and its simple implementation allows the treatment of unsteady plasmas in complex geometries (see e.g.…”