Active Flow Control Of Dual-throat Fluidic Thrust-vectoring Nozzle Using Synthetic Jet Driven By Spark Discharge

Active flow control by using the synthetic jet had been more successfully used in the low-speed flow cases. However, this advanced flow control method was scarcely investigated in the supersonic flow conditions. The sparkjet is regarded as a promised technology for the high-speed flow control due to its stong penatration. Exploring the advanced active flow control method on the dual throat nozzle is beneficial for improving the nozzle performance and thrust vetoring. In this paper, the flow features of a sparkjet were researched experimentally and numerically. Simultaneously, the applications of the sparkjet on the thrust vectoring and boundary layer separation control for a dual throat nozzle were explored by numerical simulation.This paper includes mainly three aspects:The characteristics of a sparkjet flow was investigated experimentally and numerically. It is found that the spark jet takes on spherical-shape diffusion near the orifice outlet at the initial stage duiling the sparkjet formation. As the sparkjet develops, a series of vortices are induced by the shear and entrainment actions of the spark jet. The reciprocating movement of the high static pressure zone due to the spark dischage inside the actuator cavity makes the cavity pressure and jet ejecting velocity oscillate and decrease together. The normal ejecting velocity and penatrting capacity of a sparkjet are both increased with the increse of the operation frequency and discharge energy.The active flow control for the primary flow vectoring of a dual throat nozzle by using spark jet actuators was explored numerically. With regards to the individual action of the sparkjet, it is revealed that the sustained deflection of thrust vectoring is difficult to be relized because the injection mass and duty duration of the sparkjet is too small. Thus, a combined scheme of spark-excited synthetic jet and bypass continuous jet for the two-dimensional dual throat fluidic thrust vectoring nozzle was presented. The results show that the secondary flow injection with spark excitation can be divided three stages, such as spark-excited synthetic jet predominant injection, interval injection and bypass continuous jet predominant injection. It is revealed that the secondary flow injection with spark excitation is capable of changing the primary flow recirculation zone inside the two-dimensional dual throat fluidic thrust vectoring nozzle, thus affecting the vectoring deflection of the primary flow. Under the present spark-excitation parameters, the secondary flow injection with the use of 1% primary flow mass rate could realize maximum instantaneous vectoring deflection of 14 degree approximately. The averaged vectoring deflection in a spark-excitation cycle is about 6.6 degree, which is increased about 70% in relative to the no spark-excitation case.The active flow control for restrain the primary flow boundary layer separation in the single expansion edge of a dual throat nozzle by using spark jet actuators was explored numerically. It is found that the sparkjet is capable of postponing the primary flow boundary layer separation in the single expansion edge during the first several operation cycles and thus resulting in a larger flow deflection and a higher thrust coefficient. However, this effectiveness can not be sustained. Boundary layer separation on the single expansion edge is continuously and remarkably improved by using the combined scheme of spark-excited synthetic jet and bypass continuous jet, and resulting in a obvious improvement of the thrust coefficient.