Investigation of internal flow and mixing characteristics in dual-orifice atomizers

Dual-orifice atomizers have been developed to overcome the limitations of simplex atomizers—where “simplex” refers to having only a single flow channel—which cannot adjust flow rates over a wide range. This study explores the internal flow and mixing characteristics of dual-orifice atomizers using the Volume of Fluid method. The effects of four key parameters—primary post thickness, primary recess length, secondary swirl number, and mass flow rate ratio—on flow dynamics and atomizer performance, particularly exit film thickness and spray cone angle, are investigated. The results reveal that, before mixing, the low-pressure region created by the swirling flow inside the secondary nozzle increases the primary flow angle and reduces the thickness of the primary liquid film. After mixing, the velocity difference between the primary and secondary flows enhances atomization by promoting greater instability. The impingement position of the primary liquid film is influenced by recess and the low-pressure region inside the secondary nozzle, with longer recess lengths shifting the impingement point upstream. Increases in secondary swirl number, mass flow rate ratio, and primary post thickness further enlarge the low-pressure region, causing the impingement point to move upstream. The mixing regime is defined by the impingement position, with tip mixing creating velocity stratification that increases the instability. The performance of dual-orifice atomizers depends on the impingement position, resulting mixing regime, and secondary flow's swirl intensity. These findings provide valuable insights for optimizing atomizer design to improve performance.