Review of atomization characteristics of liquid jets in crossflow

Buoyant jets have been a topic of interest due to their presence in various natural and industrial phenomena, as well as in our daily lives. Covering extensive literature, our focus in this review article is on free, miscible buoyant jets with small-density differences (under the Boussinesq approximation) within uniform and stagnant environments. We examine the latest research on Newtonian jet flows and expand our scope to their viscoplastic counterparts, reflecting a burgeoning trend in contemporary literature. Our analysis covers negatively buoyant, pure, and positively buoyant jets, via delving into their dynamics. This includes regime classifications and key jet characteristics, such as laminar length, penetration length, mixing behavior, velocity profiles, and turbulence parameters. In particular, the effects of the key governing dimensionless parameters, including the Reynolds number, the Froude number, the Bingham number, the viscosity ratio, and the injection angle, on these characteristics are explored.

A review on free miscible buoyant jets

Hassanzadeh,

Taghavi

2024

Numerical simulations of secondary atomization characteristics of shear-thinning kerosene gels

Li,

Yuan

et al. 2024

Owing to their unique non-Newtonian characteristics, gel propellants have become a new type of fuel with promising applications in the aerospace industry. However, the complex rheological properties and high viscosity of gels pose significant challenges for flow control in gel engines, particularly in terms of fuel atomization and combustion efficiency. Focusing primarily on kerosene gel, this study investigates the secondary atomization characteristics of shear-thinning droplets, where the volume of fluid method is employed to capture interface dynamics on adaptive grids, and the viscosity of the gel is described by a power-law model. The accuracy of the numerical model is validated by comparing it with the experimental observations of the breakup process of 1% silica kerosene gel droplets. Numerical simulations are conducted to analyze the droplet breakup processes and formation mechanisms under bag, multimode, and shear breakup. Compared to kerosene, the apparent viscosity distribution inside the kerosene gel droplets is non-uniform, and the inhibition of viscous force delays the breakup time and reduces the droplet deformation, thereby affecting the transition of the breakup mode. By varying the Weber number, We, the rheological parameters, and the density ratio, the quantitative effects of these factors on droplet deformation, centroid velocity, average viscosity, the breakup time, etc. are revealed. The results indicate that the breakup becomes more severe with increasing We number, resulting in larger deformation and a greater number of smaller droplets; the rheological parameters significantly affect the droplet breakup by altering the fluid viscosity; moreover, under the same flow condition, the higher the density ratio, the more difficult it is for the droplet to break up; however, on dimensionless scales, the effect of density ratio appears weak. Additionally, a breakup regime diagram is constructed in the We–Oh (Ohnesorge) number space for low Weber numbers. This study validates the numerical method for simulating the secondary atomization of kerosene gel propellants, providing a thorough analysis of three breakup mechanisms and the impact of key parameters on kerosene gel droplets. These insights offer a theoretical foundation for the optimization of gel propellants, aiding in the development of efficient and stable propulsion systems.

Atomization performance optimization of series dual-chamber self-excited oscillation nozzle using the entropy weight method combined with gray theory

Nie,

Song,

et al. 2024

In this study, a series dual-chamber self-excited oscillation nozzle (SDSON) for atomization was developed for photodecomposition of oily wastewater. In order to address the computational complexity associated with optimizing this nozzle, a surrogate model that integrates computational fluid dynamics simulation is proposed. By employing a multi-objective optimization algorithm that combines Genetic Algorithm and Non-dominated Sorting Genetic Algorithm II, significant improvements in atomization performance have been achieved. The influencing factors of atomization and their interactions on the nozzle's atomization performance have been analyzed. The entropy weight method was employed in conjunction with gray theory to rank the optimal solutions based on weighted correlation evaluation, resulting in the determination of the most favorable design solutions. The optimized design exhibited significant enhancements in turbulence kinetic energy and gas volume fraction at the nozzle outlet. Atomization experiments confirmed that the optimized SDSON generated smaller and more uniformly sized droplets under identical inlet pressure conditions, thereby greatly improving atomization performance.