Production of coherent oscillations in thermal plasma jet generated in water stabilized torch

Summary form only given. A water plasma torch with an anode positioned downstream of the torch exit was used for the generation of an oxygen/hydrogen thermal plasma jet with extremely high plasma temperature and velocity. Fluctuations in the jet were observed using a linear array of photo-diodes. Coherent oscillations with narrow frequency spectrum were observed in the region of interaction of the plasma jet with an secondary anode jet which is created at the point of arc current passage into the electrode. The dependence of amplitude and frequency of oscillations on parameters of the plasma jet and on position of the anode was determined. The coherent oscillations observed in the plasma are probably related to the production of vortex structures due to interaction of flowing plasma in the mainjet with the anode jet. Besides the production of coherent oscillations the formation of new anode attachment by the downstream restrike is a source of perturbation similar to shock wave. The velocity of propagation of the perturbations through the plasma jet in both directions from the point of restrike was determined from the delay of signals of the diodes.