Boundary Layer Analysis of an SF6 Circuit Breaker Arc

Radial temperature profiles for pulsed SF6 arcs burning in high-pressure, approximately 5 bar, supersonic gas flow have been measured in the range 10 kA-1.0 kA. The temperature distribution was obtained from the emission intensities of spectral lines due to excited fluorine and ionized sulphur. The results for currents above 3.5 kA show that the axis temperature is 20000K+or-1000K and is independent of the arc current. Also the temperature profile is essentially parabolic, and any increase in arc current is accompanied by a corresponding increase in arc cross section to maintain a constant current density. Below 3.5 kA the axis temperature falls rapidly with current down to 15500K+or-1000K at kA and the temperature profiles show very steep temperature gradients less than 1 mm from the arc axis.

Section: Discussionmentioning

confidence: 99%

Time-resolved radial temperature profiles for 10 kA SF₆arcs

Airey¹,

Richards²,

Swift³

1975

“…Turbulent energy losses have also generally been ignored in these models. The present analysis overcomes these deficiencies using the boundary layer analysis first proposed by Swanson andRoidt (1971, 1972).…”

Section: Theorymentioning

confidence: 97%

The influence of laminar and turbulent flows upon the electrical characteristics of wall-stabilised arcs

Hill

Jones

1979

Measurements are reported of the electrical properties of wall-stabilised arcs subject to an imposed axial flow of nitrogen under steady current conditions. The current was in the range 10-60 A DC and the gas flow rate was 0-0.6 g s-1 with stabilising bore radii of 2.5 mm and 5 mm. The results of the investigation confirm the existence of two axial zones corresponding to a flow entrainment region and a fully developed column region. The electric field strength along the fully developed region increases with mass flow rate as turbulent effects become more pronounced. An analytical arc model, based upon boundary layer approximations and taking account of molecular and turbulent radial diffusion and axial convection, is presented. Results of calculations using this model predict the trends observed experimentally.

“…It had been shown previously that in our experiment the observed turbulence originates at the arc boundary and from there grows into the arc and into the cold gas region (Niemeyer and Ragaller 1973). Therefore it is more appropriate in our case to use the mixing length formula for free turbulent shear flow (Prandtl 1942, Pai 1954, Schlichting 1960, Swanson and Roidt 1969 :…”

Section: Radial Transport Due To Turbulent Mixingmentioning

confidence: 99%

“…Particular attention has been paid to arcs in high-pressure supersonic nozzle flows which are of interest not only from the point of view of arc physics but also as a result of important, technical applications such as gas blast circuit breakers and high-power arc heaters. Various physical aspects of this type of arc have been investigated both experimentally and theoretically in a number of papers (eg Stine and Watson 1962, Swanson and Roidt 1969, Cowley 1971, Grycz et a1 1971, Topham 1971, Andriessen 1973, Frind and Rich 1974.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical study of a stationary high-current arc in a supersonic nozzle flow

Hermann

Kogelschatz

Niemeyer

et al. 1974

In a previous paper (Hermann et al 1974) a detailed experimental and theoretical investigation of an arc in a supersonic nozzle flow was initiated by discussing the high-pressure arc section near the stagnation point. This paper is a continuation of this work for the section further downstream, especially within the nozzle. Extensive measurements of temperature, flow velocity, pressure and electric field strength are described. Theoretical results are obtained by a two-zone model. A detailed comparison between theory and experiment allows for the first time a complete quantitative discussion of all effects influencing the arc and the flow. Compared with the arc in the high-pressure section the influence of radiative energy transfer decreases. Instead, flow turbulence becomes the dominating exchange mechanism.