The influence of geometrical and operational parameters on Y-jet atomizers performance

Abstract

The effects of operational and geometrical parameters on pressure distribution and flow pattern in Y-jet atomizers were studied using an experimental apparatus working with air and water. The results show that the mixing point pressure is very dependent on the diameter ratio of the mixing duct and the air port and the water supply pressure ratio. A correlation to predict the mixing point pressure was developed and showed good agreement with the experimental data. With this correlation, it is possible to predict the occurrence of the critical condition for the air flow at the exit of its port. In a second group of results, the influence of geometrical and operational parameters on the pressure distribution inside the mixing duct was analyzed. The main result found was that for air liquid ratio between 0.1 and 0.2, this pressure distribution can be taken as linear. This information about air liquid ratio and the correlation to predict the occurrence of chocked flow at the exit of the air port may give useful guidelines for atomizer designers. Finally, using a two-phase map, the flow pattern inside Y-jet atomizers was found to be a transition between the annular flow and the wispy-annular flow. Keywords Y-jet atomizers Á Twin-fluid atomizers Á Two-phase flow patterns Á Experimental correlations List of symbols ALR Air liquid ratio d Diameter [m] G Fluid mass velocity [kg/m 2 s] j Superficial velocity [m/s] l Length [m] p Pressure [Pa] SR Slope ratio T Temperature [K] _ m Mass flow rate [kg/s] z Position [m] Non-dimensional groups We Weber number Greek symbols c Ratio of specific heats Dp Pressure drop [Pa] h Angle between air and water ports [rad] q Density [kg/m 3 ] u Momentum ratio Subscripts 1 Middle point pressure measurement in mixing duct 2 End point pressure measurement in mixing duct a Air w Water ha Air at upstream position of the tape orifice plate M Mixing point m Mixing duct

The Influence of Geometrical and Operational Parameters on Internal Flow Characteristics of Internally Mixing Twin-Fluid Y-Jet Atomizers

“…Air and water are used as working fluids at atmospheric conditions. The geometries are constructed in ANSYS Design Modeler according to the design criteria of Mullinger and Chigier (1974); the same design criteria were also adopted by Pacifico and Yanagihara (2014) for the experimental study on pressure drop within internally mixing twin-fluid Y-jet atomizers. The geometries are meshed in ANSYS Meshing tool.…”

“…The advantage of such an atomizer is that it could be operated by keeping constant gas-to-liquid mass flow rate ratio, and the requirement of the atomizing fluid is low. Y-jet atomizers are reported to maintain a moderate emission rate while attaining relatively high atomization efficiency (Pacifico and Yanagihara, 2014). This kind of atomizer creates high relative velocity by injecting gas at high velocity, which induces disturbances in the liquid jet and leads to the creation of smaller liquid ligaments; subsequently, smaller droplets are formed due to the ligament's breakup due to aerodynamically induced surface waves (Dombrowski and Johns, 1963).…”

“…This kind of atomizer creates high relative velocity by injecting gas at high velocity, which induces disturbances in the liquid jet and leads to the creation of smaller liquid ligaments; subsequently, smaller droplets are formed due to the ligament's breakup due to aerodynamically induced surface waves (Dombrowski and Johns, 1963). The high relative velocity of the gas helps dispersion of the liquid and prevents coalescence of droplets (Pacifico and Yanagihara, 2014).…”

“…However, there exist a few numerical studies such as Tanner et al (2016) which focuses on the atomization and droplet breakup in annular gas-liquid co-flow for an internally mixing twin-fluid Y-jet atomizer, and Tapia and Chavez (2002), which focuses on the internal flow pattern. In all studies except Song and Lee (1996), Andreussi et al (1994), Mlkvik et al (2015), Pacifico and Yanagihara (2014), and Tapia and Chavez (2002), the parameters such as injection conditions and atomizer geometry were taken as input while the spray dispersion was the reported output, but the intermediate process between the input and output of the nozzle has not been investigated in detail.…”

Evaluation of Steadiness and Drop Size Distribution in Sprays Generated by Different Twin-Fluid Atomizers

“…According to [19][20][21] the internal flow regime depends on liquid and gas mass flows, and GLR and dimensions of the mixing chamber. The atomization process is divided into three phases according to [21].…”