STABILITY OF A DC SF6 ARC IN AN AXIALLY ACCELERATING FLOW

The stability of a dc arc burning in an axially accelerating flow of S F6 is investigated, The method of normal modes is applied to the equat ions governing an axisymmetric, infinitesimal perturbation of a self-s imilar are, and solutions are obtained numerically. Results are presen ted for a range of discharge conditions, The physical mechanisms causi ng instability are deduced from equations for the time-averaged, squar ed enthalpy, and velocity of a perturbation, The steep radial gradient of the density at the edge of the arc is shown to cause instability, The effect of density fluctuations in comparison with velocity fluctua tions is not negligible, and the possible implication of this result f or turbulent are modeling is discussed.