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Direct numerical simulation of a high-pressure hydrogen micromix combustor: Flame structure and stabilisation mechanism

Journal Article · · Combustion and Flame
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  1. Newcastle University, Newcastle upon Tyne (United Kingdom)
  2. Reaction Engines Ltd., Abingdon (United Kingdom); Sunborne Systems Ltd., Abingdon (United Kingdom)
  3. University of Southampton (United Kingdom)
  4. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
+ Show Author Affiliations
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 et al., 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.
Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR)
Grant/Contract Number:
AC02-06CH11357; AC36-08GO28308
OSTI ID:
2370391
Report Number(s):
NREL/JA--2C00-87505; MainId:88280; UUID:6470a898-6390-4eaf-a871-e78508c203f1; MainAdminId:72731
Journal Information:
Combustion and Flame, Journal Name: Combustion and Flame Vol. 265; ISSN 0010-2180
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
97 MATHEMATICS AND COMPUTING
direct numerical simulation
flame stabilisation
flame structure
hydrogen
micromix combustor