Two competing mechanisms of plasma action on a jet flow

The influence of the plasma generation and propagation in a pulsed atmospheric pressure plasma jet on the gas flow is experimentally studied. The discharge was powered with pulsed voltage signals of both polarities with amplitudes that ranged from 2.8 to 10.8 kV and with the frequencies of 1–5 kHz. It operated in a pure helium and helium with a small admixture of oxygen and nitrogen. The measurements of the flow changes are performed by means of a laboratory constructed manometer with a free membrane. Two plasma action mechanisms have been identified and described: the electrohydrodynamic force mechanism and thermal mechanisms due to the fast localized heating. These two mechanisms appear to be counterbalancing or supporting depending on the experimental conditions. Besides, it was shown that plasma can cause a decrease in the gas velocity, probably depending on the dominant presence of the negative or positive ions in the jet.