The mixing of the spray in mach 2 high enthalpy cross flow

An experiment observation of liquid jet spray in supersonic cross flow is revealed in this research. A reflected shock tunnel is used to simulate the high temperature supersonic flow conditions (Mach 2, total temperature of 2000K). JP-4 is adopted as the liquid fuel. High speed camera coupled with Schlieren system is used to observe the mixing of the liquid jet spray with the supersonic airflow. A laser system is also used for Mie scattering observation. In this research, the JP-4 is injected with a mass flow rate of 16g/s through single or double 0.5mm orifice into supersonic flow. The injection system is capable to provide the jet to free stream momentum flux ratio (J) from 4 to 9. Quantitative analysis of their mixing behavior is performed A series of experiments results show the detailed mechanism of spray dissipation or mixing in supersonic cross flow was elucidated in this research. The liquid jet breaks up into spray instantly because of high Weber number of supersonic freestream and a strong shock wave compression. Due to the vortex surrounding the spray, a strong stripping interaction between the droplets and the freestream turbulence enhances the evaporation of droplets and reduces their size. The observation shows the interactions between the oblique shock induced by boundary separation and the bow shock induced by the liquid jet crucially affect the mixing behavior between spray and surrounding airflow also. The unsteady phenomena of the boundary separation cause the shock/shock interaction to be unstable. Bow shock vibration occurs because of the unstable shock interactions. The spatially vibrating shock creates spatial pressure fluctuation behind the shock wave; therefore, the liquid jet becomes unstable as well. The high-pressure and high-temperature region behind the shock/shock interaction zone increases the instability of the jet.