Flow regime transitions in flow blurring injection through a CFD parametric study.

Flow-blurring (FB) is a twin-fluid atomization technique that generates fine sprays through internal turbulent mixing. This study presents a parametric computational investigation of an FB injector operating with air and various liquids at ambient pressure. A validated unsteady two-phase solver based on the Volume of Fluid (VOF) method is used to model the injector at different air-to-liquid mass flow rate ratios (ALRs). Parameters such as penetration length, volume fraction, static pressure, vorticity magnitude, and turbulent kinetic energy are analyzed to understand flow dynamics. The results identify three distinct flow regimes: air-dominant, liquid-dominant, and bubbly flow. Screening analysis of a full factorial design of 32 cases shows that liquid mass flow rate and dynamic viscosity are the most influential factors in penetration length. The resulting penetration length varies between 2 [mm] and 8.5 [mm] across the design space. A correlation analysis confirms these findings and reveals important two-way interactions between parameters, such as the positive effect of combined liquid and air mass flow rates. This insight offers a promising pathway for optimizing flow-blurring injectors in various applications.