Study on the Spray Characteristics and Oscillation Mechanism of a Feedback-Free Internal Impinging Nozzle

Feedback-free internal impinging nozzle, which can generate fan-shape oscillating spray with constant pendulum angle, is well-suitable for flow control, as it has a wide range of operation frequency and does not require additional energy for moving parts. In this study, the spray characteristics of an internal impinging nozzle were investigated in an open atomization test bench by utilizing high-speed Schlieren technology and Malvern particle size analyzer. To better understand the jet oscillation mechanism and to evaluate its impact on the spray sweeping behaviors, a 3D CFD simulation was carried out, which takes the nozzle internal flow dynamics and the external spray morphology into account. The results indicate that the sweeping behavior of the emitted jet is caused by the impingement between two opposite internal jets inside the nozzle. A bi-model spray spatial flow distribution of the nozzle is observed with varying oscillating frequencies and constant spray pendulum angle at different injection pressures. The oscillation process can be divided into two stages depending on jet breakup processes, and the spray waveforms are influenced by the ratio of the durations of these two stages.