The influence of pulse parameters on the downstream uniformity of linear-field jet array in argon

Abstract

The nanosecond (ns) pulse excited plasma jet array shows merits of large treatment area and high chemical reactivity, while the pulse parameters influence the downstream uniformity of the ns pulse excited jet array significantly. In this paper, the downstream uniformity of the ns pulsed jet array with linear-field electrode structure is investigated by discharge image measurement at different amplitude of applied voltage, rising time and pulse repetition frequency (PRF). The voltage-current waveform and Schlieren image are measured and the electrical field distribution of the jet array is simulated to reveal the interaction mechanisms. The experimental results show that the divergence of side plumes becomes severer and the plume length of all three jet units becomes longer at higher applied voltage, which is caused by the enhancement of the electron energy and density. The shorter rising time also increases the transported charge and input energy and extends the length of the plasma plumes. At 0.5 L/min Ar flow rate, all of the lengths of plumes increase with PRF although the laminar regimes of the gas flows are reduced. At Ar flow rate of 1, 2, and 4 L/min, the middle jet is suppressed, which is analyzed by the electrical field distribution simulation. It is shown that the highest electric fields at the outside walls of side jet units, which suppress the propagation of ionization front from the orifice to the outer space of the middle jet. At lower Ar flow rate, there are severe depletion of electrons in the side jets by oxygen and penning ionization in the middle jet by background molecules, which result in the enhancement of the jet array downstream uniformity. The results are of importance to optimize pulse parameters for the realization of controllable and scalable pulse excited jet array for various applications.