Effects of capacitance on a plasma synthetic jet actuator with a conical cavity

Plasma Synthetic Jet Actuator (PSJA), which incorporates no mechanical parts, zero mass flux capability, adjustable operating frequency and momentum throughput, has drawn increasing attention on high speed flow control. Experiments were conducted on a PSJA with a conical cavity at same energy input, the energy supplied to the PSJA mainly comes from a charged capacitor in a high voltage. The effect of different capacitances on the control authority of the actuator in quiescent condition, as well as its essential characteristics, are investigated. In the experiments, qualitative and quantitative measurements including electrical characteristics, high-speed schlieren, phase locked particle image velocimetry, and dynamic pressure, were fulfilled. Comparative analysis was carried out to study the jet flow difference caused by discharge duration, which depends on the capacitance(1 μF, 2 μF, 4.7 μF and 10 μF), and the energy supplied to the actuator is assumed to be constant. Results show that the discharge duration extends as capacitance increases, so the air inside the cavity is heated more homogeneously. However, smaller capacitance leads to shorter discharge time, but a more vigorous jet flow with stronger blast wave and higher accelerated zone. Accordingly performance fade of the actuator was found as the capacitance increases. Furthermore, two typical morphological features, including the initial intermittent accelerated zones (blast jet) and the heated jet body (hot jet), are adopted to form a conceptual model, by which the nature of the jet was characterized.