Browse by author
Lookup NU author(s): Dr Thomas Howarth, Dr Andrew AspdenORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
A high-pressure hydrogen micromix combustor has been investigated using direct numerical simulation with detailed chemistry to examine the flame structure and stabilisation mechanism. The configuration of the combustor was based on the design by Schefer \cite{Schefer2003EvaluationBurner}, using numerical periodicity to mimic a large square array. A precursor simulation of an opposed jet-in-crossflow was first conducted to generate appropriate partially-premixed inflow boundary conditions for the subsequent reacting simulation. The resulting flame can be described as an predominantly-lean inhomogeneously-premixed lifted jet flame. Five main zones were identified: a jet mixing region, a core flame, a peripheral flame, a recirculation zone, and combustion products. The core flame, situated over the jet mixing region, was found to burn as a thin reaction front, responsible for over 85\% of the total fuel consumption. The peripheral flame shrouded the core flame, had low mean flow with high turbulence, and burned at very lean conditions (in the distributed burning regime). It was shown that turbulent premixed flame propagation was an order-of-magnitude too slow to stabilise the flame at these conditions. Stabilisation was identified to be due to ignition events resulting from turbulent mixing of fuel from the jet into mean recirculation of very lean hot products. Ignition events were found to correlate with shear-driven Kelvin-Helmholtz vortices, and increased in likelihood with streamwise distance. At the flame base, isolated events were observed, which developed into rapidly burning flame kernels that were blown downstream. Further downstream, near-simultaneous spatially-distributed ignition events were observed, which appeared more like ignition sheets. The paper concludes with a broader discussion that considers generalising from the conditions considered here.
Author(s): Howarth TL, Picciani MA, Richardson ES, Day MS, Aspden AJ
Publication type: Article
Publication status: Published
Journal: Combustion and Flame
Year: 2024
Volume: 265
Print publication date: 01/07/2024
Online publication date: 22/05/2024
Acceptance date: 07/05/2024
Date deposited: 23/05/2024
ISSN (print): 0010-2180
ISSN (electronic): 1556-2921
Publisher: Elsevier Inc.
URL: https://doi.org/10.1016/j.combustflame.2024.113504
DOI: 10.1016/j.combustflame.2024.113504
Altmetrics provided by Altmetric
