Study of Deformation and Breakup of Submillimeter Droplets’ Spray in a Supersonic Nozzle Flow

Oleg A Gobyzov,Artur V Bilsky,Mikhail N Ryabov

doi:10.3390/app10186149

Abstract

The problem of secondary atomization of droplets is crucial for many applications. In high-speed flows, fine atomization usually takes place, and the breakup of small droplets determines the final products of atomization. An experimental study of deformation and breakup of 15–60 µm size droplets in an accelerated flow inside a converging–diverging nozzle is considered in the paper. Particle image velocimetry and shadow photography were employed in the experiments. Results of gas and liquid phase flow measurements and visualization are presented and analyzed, including gas and droplets’ velocity, shape and size distributions of droplets. Weber numbers for droplets’ breakup are reported. For those small droplets at low Weber numbers, the presence of well-known droplets’ breakup morphology is confirmed, and rare “pulling” breakup mode is detected and qualitatively described. For the “pulling” breakup mode, a consideration, explaining its development in smaller droplets through shear stress effect, is provided.

Highlights

Experimental data on droplets behavior in high-speed flows is often required for such applications as combustion of liquid fuels, especially in ramjets, liquid atomization in airblast nozzles and many others
Results provided by Kim and Hermanson [19] and further developed in [21], showed that under supersonic and overheating conditions, droplets exhibit breakup stages and morphology in some aspects different from commonly adopted
One of the main conclusions brought by the authors was that for different test liquids droplet breakup followed a similar pattern that included four subsequent stages: the initial deformation of the droplet, sheet stripping, ‘primary breakup’ and a catastrophic breakup

Summary

Introduction

Experimental data on droplets behavior in high-speed flows is often required for such applications as combustion of liquid fuels, especially in ramjets, liquid atomization in airblast nozzles and many others. Through the last several decades, a large number of experimental works aimed at revealing of influencing parameters, better understanding of breakup evolution and morphology, systematization of acquired data were performed. A widely-adopted breakup morphology classification was proposed in the paper by Pilch and Erdman [1]. A lot of attention was paid to the physical phenomena, governing the droplets morphology and transition between regimes. The proposed classification was expanded, and the role of different phenomena was revised through a series of works summarized in the paper of Theofanous [4]

Methods

Results

Conclusion