Disintegration Characteristics of Liquid Jet Ejected from Internal Mixing Twin Fluid Atomizers

To understand the disintegration phenomena of cylindrical liquid jet co-flowing with high speed air stream in the nozzle, the disintegration mechanism depending on the coaxial air flow introduced to the liquid jet was experimentally investigated with twin fluid atomizers made of glass. This study focused on the effects of the dimension of the mixing tube, the liquid and air flowrate on flow patterns, the disintegration mechanism of liquid jet, and the pressure variation of nozzle interior. When the air stream was supplied to the longest smooth liquid jet, flow patterns in the nozzle interior were observed for various diameters of mixing tubes and liquid jets. For the nozzles where the through-flow of liquid jet was obtained, the maximum breakup length according to the ejection velocity of liquid jet was seen at Re_i = 2100 and the minimum at Re_i = 4500. The former Reynolds number indicated the boundary between the laminar jet and transient jet, and the latter Reynolds number indicated the boundary between the transient jet and turbulent jet. When air flowed coaxially along the liquid jet, the breakup length generally decreased drastically. On the contrary, there existed a region where the breakup length increased even though air was supplied to the liquid jet. This phenomenon was observed in the region of the droplet flow. The pressure within the nozzle peaked at the boundary region of transient flow and turbulent flow where fluctuation of the liquid jet was most severe.