Effective ionization coefficients and transport parameters in binary and ultradilute SF₆–Ar mixtures using Boltzmann equation analysis

Abstract

The effective ionization coefficients and transport parameters such as electron mean energy drift velocity and transverse diffusion coefficient in binary and ultradilute SF6–Ar gas mixtures have been calculated for density reduced electric field strength E/N values from 10 to 400 Td. These calculations have been performed by using the two-term spherical harmonic expansion to obtain the numerical solution of the Boltzmann transport equation based on the finite element method under steady-state Townsend condition. In order to confirm the model and code developed in this study, the Reid ramp model has been used as a benchmark test and then effective ionization coefficients and transport parameters have been evaluated for SF6 contents of 1%, 10%, 25%, 50%, 70% and 100% in the binary mixture. Finally SF6 contents in the ultradilute mixtures of 0.1%, 0.3%, 0.5% and 0.7% are taken into account with the evaluated effective ionizations and transport parameters of electron mean energy, drift velocity and transverse diffusion coefficients.

Response analysis of electron attachment rates to C3F8and SF6in buffer gases

“…For certain mixtures of an electronegative gas and a buffer gas, and for particular values of E/N , a linear relation is apparent between k and the effective ionization rate constant ν eff /N . This is shown, for example, in figure 5 of [10] and figure 8 of [11]. Such a linear relation also appears in our measurements and in the results of two mutually independent numerical methods [8,9], as one can note from the figures 1 and 6 of the present article.…”

“…In this way the same gas mixture was investigated for 4 to 6 different N -values in the pressure range specified in table 2. The PT waveforms have been recorded for electrode spacings d = (17,15,13,11) mm in the E/N -range of interest. The cumulative uncertainty of the (E/N )-values was ±1.5%.…”

“…SF 6 can therefore be considered as providing a benchmark [1,13]. We compare our measurements to numerical results because experimental data are scarce in the parameter range of the present study [10,11]. Subsequently, the linear response technique is applied for testing the attachment cross sections of octafluoropropane (C 3 F 8 ).…”

Analysis of the insulation characteristics of CF3I gas mixtures with Ar, Xe, He, N2, and CO2using Boltzmann equation method

“…On the other hand, the strong electron attachment process slows down the electron drift velocity and leads to a depletion of the high energy tail of the EEDFs curve, which is coincident with the change trends in the SF 6 -Ar gas mixture. 31) Figure 6 shows the electron drift velocity for different mixture compositions in CF 3 I-Ar gas mixture as a function of E/N. The stronger E/N makes the electrons gain more kinetic energy from the applied electric field and speeds up the electron drift velocities, which results in V e displaying a relation in direct proportion to the E/N values.…”

Effective ionization coefficient of C5 perfluorinated ketone and its mixtures with air

“…One possible solution for the problem of high GWP of SF 6 is mixing of SF 6 with other gases e.g. N 2 , He, Ar, Xe, CO 2 , CHF 3 , CF 4 , N 2 O and CF 3 I [3][4][5][6][7][8][9][10][11]. However, at SF 6 fractions which allow sufficient reduction of GWP potential, the dielectric strength of these mixtures becomes comparable to the strength of air or CO 2 .…”