The effects of the ambient air pressure level on the performance of plasma synthetic jet actuator have been investigated through electrical and optical diagnostics.Pressures from 1 atm down to 0.1 atm were tested with a 10 Hz excitation.The discharge measurement demonstrates that there is a voltage range to make the actuator work reliably.Higher pressure level needs a higher breakdown voltage,and a higher discharge current and energy deposition are produced.But when the actuator works with the maximum breakdown voltage,the fraction of the initial capacitor energy delivered to the arc is almost invariable.This preliminary study also confirms the effectiveness of the plasma synthetic jet at low pressure.Indeed,the maximum velocities of the precursor shock and the plasma jet induced by the actuator with maximum breakdown voltage are independent of the ambient pressure level;reach about 530 and 460 m/s respectively.The mass flux of the plasma jet increases with ambient pressure increasing,but the strength of the precursor shock presents a local maximum at 0.6 atm.
The evaluation indicator for the performance of a synthetic jet actuator(SJA) is welldefined because of its various applications, which require optimal design to improve its performance and extend its field of application. This paper presents a novel approach to the optimal design of an SJA applied to enhance fuel/air mixture. It optimizes the combination of an actuator's geometric parameters by selecting the strength of vortex pairs as the evaluation indicator, coupled with orthogonal experiments and analysis of variance(AOV). The results indicate that slot width is the most notable factor influencing the strength of vortex pairs, followed by cavity height and slot depth. The optimal value of the strength of vortex pairs increases by 32.5% over the experimental data of the base case, and more than 8.4% compared with the simulation results of the orthogonal experiments. It is concluded that the optimal method can effectively improve the performance of an SJA applied in mixing enhancement, reducing the test numbers and the associated design cycle and cost.
