The spray characteristics of an open-end swirl injector at ambient pressure

To study the spray characteristics of an open-end swirl injector under ambient pressure, cold flow tests were conducted using a high-speed shadowgraph system. The effects of geometrical parameters (including tangential inlet diameter and injector length) and operating parameters (including injection pressure drop) under high ambient pressure were systematically investigated. The experimental results indicate that spray is suppressed by ambient pressure. With increased ambient pressure, the discharge coefficient increased while the spray cone angle, spray width and breakup length decreased. Under a low injection pressure drop of 0.1 MPa, the maximum deviations of the discharge coefficient and spray cone angle under 5 ambient pressure conditions were 22.6% and 31.2%, respectively. Under a high injection pressure drop of 0.7 MPa, the maximum deviations under 5 ambient pressure conditions were 1% and 18.1%, respectively. A critical pressure value was found at which the spray structure converts from a wide hollow cone to a narrow contracting bell. Increasing the tangential inlet diameter (Dp) or the ratio of the injector length to the injector orifice diameter (L/D) would eventually decrease the swirling intensity. Therefore, the discharge coefficient increases while the spray cone angle decreases. Comprehensively considering the effects of geometrical and operating parameters, empirical formulas for the discharge coefficient and spray cone angle are proposed for engineering applications.