Quantification of combustion regime transitions in premixed turbulent DME flames
File(s)CNF2014MF_v38.pdf (6.17 MB)
Accepted version
Author(s)
Hampp, F
Lindstedt, RP
Type
Journal Article
Abstract
The current study quantifies the probability of encountering up to five fluid states (reactants, combustion products, mixing fluid, fluids with low and high reactivity) in premixed turbulent DME flames as a function of the Damköhler number. The flames were aerodynamically stabilised in a back-to-burnt opposed jet configuration featuring fractal grid generated multi-scale turbulence (Re≃ 18,400 and Ret > 370). The chemical timescale was varied via the mixture stoichiometry resulting in a wide range of Damköhler numbers (0.08 ≤ Da ≤ 5.6). The mean turbulent strain (≥ 3200 s−1) exceeded the extinction strain rate of the corresponding laminar flames for all mixtures. Simultaneous Mie scattering, OH-PLIF and PIV were used to identify the fluid states and supporting computations show that the thermochemical state (e.g. OH and CH concentrations) at the twin flame extinction point correlates well with flames in the back-to-burnt geometry at the corresponding rate of heat release. For mixtures where the bulk strain (≃ 750 s−1) was similar to (or less than) the extinction strain rate, fluids with low and high reactivity could accordingly be segregated by a threshold based on the OH concentration at the extinction point. A sensitivity analysis of the distribution between the fluid states was performed. The flow conditions were further analysed in terms of Damköhler and Karlovitz numbers. The study provides (i) the evolution of multi-fluid probability statistics as a function of the Damköhler number, including (ii) the flow direction across fluid interfaces and OH gradients, (iii) mean flow field statistics, (iv) conditional velocity statistics and (v) a tentative combustion regime classification.
Date Issued
2017-08-01
Date Acceptance
2017-04-06
Citation
Combustion and Flame, 2017, 182 (1), pp.248-268
ISSN
0010-2180
Publisher
Elsevier
Start Page
248
End Page
268
Journal / Book Title
Combustion and Flame
Volume
182
Issue
1
Copyright Statement
© 2017 Elsevier ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000404945100023&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Technology
Thermodynamics
Energy & Fuels
Engineering, Multidisciplinary
Engineering, Chemical
Engineering, Mechanical
Engineering
Combustion regime transition
DME
Multi-fluid statistics
Premixed flames
Fractal grid generated turbulence
PARTICLE IMAGE VELOCIMETRY
OPPOSED-JET FLAMES
DIMETHYL ETHER OXIDATION
FLOW-FIELD STATISTICS
IGNITION DELAY TIMES
REACTION ZONE REGIME
THIN REACTION ZONE
BURNING VELOCITIES
TRACER PARTICLES
DIFFUSION FLAMES
Publication Status
Published
Date Publish Online
2017-05-05