Experimental Analysis of Two-phase Flow Regimes in the discharge Passage of an Effervescent Atomizer

In the effervescent atomizer, the internal two-phase flow of discharge passage has an important role in determining the atomizer's performance. In this study, an air-water two-phase flow in a discharge passage of an effervescent atomizer is visualized using backlight photography utilizing a high-speed video camera (960 fps). The effects of operating conditions and the convergence angle of the mixing chamber on the two-phase flow regimes inside the atomizer are examined experimentally. The transparent mixing chamber has a rectangular cross-section 6mm×2mm. Moreover, the nozzle passage is 40mm in length and 2mm×2mm in cross-section. The atomizer is fed with water and uses air as an atomizing gas. Variations of flow regimes, bubble velocity and size, discharge coefficient (C _D ), as well as liquid film thickness due to different injection pressures, gas-to-liquid mass flow rate ratios (GLR) and mixing chamber convergence angles are investigated. The results indicate that the operating conditions are found to have a more pronounced effect on the two-phase flow regimes than the mixing chamber convergence angle. The experimental results show that the discharge coefficient is a non-linear function of GLR. The value of C _D decreases rapidly as GLR increases from zero to around 0.4% and thereafter decreases at a slower rate with further increases in GLR.