Liquid Sheet Breakup in Gas-Centered Swirl Coaxial Atomizers

TL;DR

This study investigates how a central gas jet influences the breakup of swirling liquid sheets in coaxial atomizers, revealing that the jet's effects depend on the liquid's inertia and significantly affect spray characteristics.

Contribution

It provides experimental insights into the role of central air jets on liquid sheet breakup, highlighting the effects of flow parameters on breakup length and surface corrugations.

Findings

Central air jet shortens breakup length for low inertia sheets at small Re_g.

High inertia sheets are less affected at small Re_g but develop shorter breakup lengths at higher Re_g.

Surface corrugations induced by the air jet promote ligament formation.

Abstract

The study deals with the breakup behavior of swirling liquid sheets discharging from gas-centered swirl coaxial atomizers with attention focused toward the understanding of the role of central gas jet on the liquid sheet breakup. Cold flow experiments on the liquid sheet breakup were carried out by employing custom fabricated gas-centered swirl coaxial atomizers using water and air as experimental fluids. Photographic techniques were employed to capture the flow behavior of liquid sheets at different flow conditions. Quantitative variation on the breakup length of the liquid sheet and spray width were obtained from the measurements deduced from the images of liquid sheets. The sheet breakup process is significantly influenced by the central air jet. It is observed that low inertia liquid sheets are more vulnerable to the presence of the central air jet and develop shorter breakup lengths at smaller values of the air jet Reynolds number $Re_g$. High inertia liquid sheets ignore the presence of the central air jet at smaller values of $Re_g$ and eventually develop shorter breakup lengths at higher values of $Re_g$. The experimental evidences suggest that the central air jet causes corrugations on the liquid sheet surface, which may be promoting the production of thick liquid ligaments from the sheet surface. The level of surface corrugations on the liquid sheet increases with increasing $Re_g$. Qualitative analysis of experimental observations reveals that the entrainment process of air established between the inner surface of the liquid sheet and the central air jet is the primary trigger for the sheet breakup.