Research on the proportional control of rectangular supersonic jet deflection based on passive secondary flow

Supersonic jet deflection control is the core of fluidic thrust vectoring technology. In particular, understanding the evolution law of jet wave structure with nozzle pressure ratio (NPR) can help to clarify the physical mechanism of jet deflection. In this study, a fluidic thrust vectoring nozzle controlled by passive secondary flow is designed. The synchronous schlieren visualization, wall pressure, and force measurement system is developed to investigate the characteristics of the jet under neutral and deflection states. Results show that under different passive secondary flow constraints, the supersonic jet exhibits three wave structure modes. Among them, asymmetric passive secondary flow constraint can cause asymmetric expansion of the jet boundary, thus realizing the deflection control of the supersonic jet. Based on this, the proportional passive secondary flow control method is proposed. When the NPR is 3.0, the maximum passive secondary flow rate is only 1.2% of the primary jet, with a maximum force vectoring angle of 8.8°, and there is no obvious hysteresis phenomenon in the entire vector control process. This control method does not need active secondary flow gas sources and has the significant advantage of simplicity in control. It is expected to play a greater role in the next generation of fluidic thrust vectoring control.