EFFECT OF MIXING PORT LENGTH ON INTERNAL FLOW AND NEAR-FIELD JET CHARACTERISTICS OF TWIN-FLUID ATOMIZERS

The present study aims to elucidate the effect of the mixing port, defined as the region where liquid and gas mix, on the internal flow and atomization process. The volume of fluid-large eddy simulation (VOF-LES) method is conducted to investigate the multiphase flow behavior in three types of twin-fluid atomizers by different mixing port lengths: 6 mm, 12.5 mm, and 25 mm. Furthermore, the jet breakup processes are observed using a high-speed video camera. The results indicate that under a low liquid flow rate, annular flow occurrs in the three types of atomizers. The thickness of the annular liquid film becomes more uniform as the length of the mixing port increases. However, at high liquid flow rates, the spray performance first increases and then decreases with the increase of mixing port length and an excessively long mixing port restrained jet dispersion. The turbulence effect and the interaction between the atomizing air and liquid increase as the flow progresses downstream, leading to the swinging motion of the jet. By comparing the spray performance of high and low liquid mass flow rates, it can be concluded that the spray performance of the mixing port length of 12.5 mm is the best in this study. Although at a low liquid flow rate, the jet breakup from the region where the liquid film is located is thinner. The mixing port length of 6 mm shows large differences in atomization performance under different mass flow rates, making it difficult to ensure atomization quality under complex operating conditions. For the mixing port length of 25 mm, the jet maintains an annular pattern and hardly breaks up.