Air swirl effect on spray characteristics and droplet dispersion in a twin-jet crossflow airblast injector

Abstract

Spray characterization in a novel twin-jet airblast injector is reported in this paper with the focus on the study of the effect of injector air swirl on droplet characteristics and dispersion behavior. The operational principle of the injector is based on achieving atomization of two liquid jets, injected in a radially opposite direction from a central hub by high-speed annular swirling cross-stream flow of air. Liquid jet atomization within model atomizers and the resulting spray study have not gained much attention in spite of its practical importance, for example, in lean premixed prevaporized combustors. In the present work, droplet size and three-component velocity measurements are measured in the above injector using the phase Doppler particle analyzer technique. Air velocity without liquid injection is also obtained using the laser Doppler velocimetry technique. For given inlet air and liquid mass flow rates, experiments are conducted in the absence and presence of annular air swirl corresponding to swirl number, S = 0 and 0.74, respectively. The addition of air swirl is found to dramatically affect the spray topology and also the measured spray characteristics as the droplet size reduces significantly downstream of the injector exit, which is explained. Droplet dispersion is studied by evaluating droplet size velocity correlation and also droplet Stokes number. The results not only provide insight into the physics behind improved atomization due to air swirl, but also demonstrate the ability of the novel injector to achieve atomization quality and high spray dispersion over a wide operating range.

Droplet size distribution in a swirl airstream using in-line holography technique

“…A few researchers (Merkle et al. 2003; Rajamanickam & Basu 2017; Kumar & Sahu 2019; Patil & Sahu 2021; Soni & Kolhe 2021) have examined the characteristics of swirl flow using high-speed imaging and particle image velocimetry (PIV) techniques. The droplet morphology and breakup phenomenon in a swirling airflow is more complex than in a straight airflow without a swirl.…”

Primary spray breakup from a nasal spray atomizer using volume of fluid to discrete phase model

“…To date, no numerical studies can be found for the nasal spray application that resolves all the complex physics involved in primary atomization. Although, there are studies that have investigated breakup mechanisms from swirl atomizers (Patil and Sahu, 2021;Sahu et al, 2022;Kuo and Trujillo, 2022) and other atomizers such as hollow cones (Di Martino et al, 2022), air-blast (Patil and Sahu, 2021), and coaxial (Kumar and Sahu, 2020;Charalampous et al, 2019). Further computational studies of nasal spray applications can be used to provide a deeper understanding of the primary breakup of the liquid sheet which influences and secondary break-up of a nasal spray and eventually the droplet characteristics.…”