Vortex formation mechanism within fuel streams in laminar nonpremixed jet flames

Cha, Min Suk; Son, Jin Woo; Yoon, Sung Hwan; Luong, Hung Truyen; Lacoste, Deanna; Sohn, Chae Hoon

Vortex formation mechanism within fuel streams in laminar nonpremixed jet flames

Files

CNF_vortex laminar diffusion_final accepted.pdf (38.83 MB)

Type

Article

Authors

Cha, Min Suk

Son, Jin Woo
Yoon, Sung Hwan
Luong, Hung Truyen
Lacoste, Deanna

Sohn, Chae Hoon

KAUST Department

Clean Combustion Research Center
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division

KAUST Grant Number

BAS/1/1384-01-01

Online Publication Date

2018-10-24

Print Publication Date

2019-01

Date

2018-10-24

Abstract

A vortical structure occurring at the fuel stream in laminar nonpremixed jet flames was recently found and shown to have both a fluid-dynamic impact on the flow field and a possible influence on the flame stability and soot formation. We designed a systematic experiment and numerical simulation to investigate the physical mechanisms of this recirculation phenomenon in a coflow system. We hypothesized that a negative buoyancy, caused by the fuel jet being heavier than the ambient air, may play a significant role in the recirculation. Therefore, we experimentally varied the density of the fuel jet using a binary mixture of methane and n-butane, and tested the density of the coflow oxidizer by replacing nitrogen with carbon dioxide. Several fuel jet velocities, flame temperatures, and nozzle diameters were also studied to thoroughly investigate all parameters that might possibly affect the recirculation. As a result, we found that our modified Richardson number, which is based on the cold density difference between the fuel and the coflow, the flame length, and the jet momentum flux, explained the physical mechanism of the recirculation well, with Ri ∼60 being the critical value for formation of the recirculation. The negative buoyancy was the primary driving force behind the recirculation, while the jet momentum mitigated its formation.

Citation

Cha MS, Son JW, Yoon SH, Luong HT, Lacoste DA, et al. (2019) Vortex formation mechanism within fuel streams in laminar nonpremixed jet flames. Combustion and Flame 199: 46–53. Available: http://dx.doi.org/10.1016/j.combustflame.2018.10.015.

Acknowledgements

The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST), under Award Number BAS/1/1384-01-01. JWS and CHS were supported by Advanced Research Center Program (NRF-2013R1A5A1073861) through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) contracted through Advanced Space Propulsion Research Center at Seoul National University.