Visualization research on influence of ambient pressure on CNG jet characteristics of gas injector with outward-opening nozzle

Abstract

In this study, the schlieren method was used to visualize the free jet from an outward-opening nozzle. The results showed that the gas jet developed faster in the radial direction than in the axial direction during the initial period. Over time, the axial penetration exceeded the radial expansion distance. When the ambient pressure was >1 bar, the x/y curves were almost coincident and did not depend on the injection pressure or ambient pressure. The effect of the ambient pressure on the penetration was significantly greater than that of the injection pressure. The ambient pressure determined the influence of the injection pressure on the penetration. The axial penetration was sensitive to the ambient pressure, which was not affected by the injection pressure. At an ambient pressure of 1 bar, the entrainment rate increased almost linearly with time. When the ambient pressure exceeded 1 bar, the entrainment rate started to increase rapidly, and then the increase slowed. An increase in the injection pressure increased the entrainment rate and improved the gas–air mixing. The values of penetration constant Γ for the near field and far field of the gas jet were determined under ambient pressures of 1 bar and >1 bar.