Study on the spark discharge plasma jet driven by nanosecond pulses

Plasma jet is a new type of rapid and wide-frequency aerodynamic actuator, which can significantly improve the aerodynamic characteristics of aircraft and power plant. Spark discharge plasma jet is advantageous for developing the higher pressures and jet velocities, compared to dielectric barrier discharge plasma actuator, which is very useful for supersonic flow control. In this paper, spark discharge plasma jet driven by high voltage nanosecond pulses is studied experimentally. The rotational temperature of N₂(C³Π_u) molecule is calculated according to its rotational emission band near 380.5 nm. The vibrational temperature is calculated with the relative intensity ratios of 371.1 and 380.5 nm, the vibrational temperatures of N₂ is 4502K. Schlieren system was used for the flow visualization. Jet velocities with different discharge parameters were measured. At very beginning an obvious bow expansion wave can be observed above the head of the jet, and then a clear pulsed jet issued out from the orifice. During the spreading of jet into the air, the velocity reduced from about 93.7m/s to less than 27m/s at about 200 us. Along with the driving frequency ascending, the velocity reduced.