Quantification of fuel chemistry effects on burning modes in turbulent premixed flames
File(s)CNF2020MF_Fuel.pdf (1.43 MB)
Accepted version
Author(s)
Hampp, F
Lindstedt, RP
Type
Journal Article
Abstract
The present work quantifies the impact of fuel chemistry on burning modes using premixed dimethyl ether (DME), ethanol (EtOH) and methane flames in a back-to-burnt opposed jet configuration. The study considers equivalence ratios 0 ≤ Φ ≤ 1, resulting in a Damköhler (Da) number range 0.06 ≤ Da ≤ 5.1. Multi-scale turbulence (Re ≃ 19,550 and Ret ≃ 360) is generated by means of a cross fractal grid and kept constant along with the enthalpy of the hot combustion products (THCP = 1700 K) of the counterflow stream. The mean turbulent rate of strain exceeds the laminar extinction rate for all flames. Simultaneous Mie scattering, OH-PLIF and PIV are used to identify reactants, mixing, weakly reacting, strongly reacting and product fluids. The relative balance between conventional flame propagation and auto-ignition based combustion is highlighted using suitably defined Da numbers and a more rapid transition towards self-sustained (e.g. flamelet type) combustion is observed for DME. The strain rate distribution on the reactant fluid surface for methane remains similar to the (non-reactive) mixing layer (), while DME and EtOH flames gradually detach from the stagnation plane with increasing Φ leading to stabilisation in regions with lower compressive rates of strain. The study further provides information on the conditions leading to burning mode transitions via (i) multi-fluid probabilities, (ii) structural flow field information and turbulence-flame interactions delineated by means of conditional (iii) velocity statistics and (iv) the rate of strain along fluid iso-contours.
Date Issued
2020-08-01
Date Acceptance
2020-05-06
Citation
Combustion and Flame, 2020, 218, pp.134-149
ISSN
0010-2180
Publisher
Elsevier
Start Page
134
End Page
149
Journal / Book Title
Combustion and Flame
Volume
218
Copyright Statement
© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Air Force Office of Scientific Research
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000541918700015&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
FA9550-17-1-0021
Subjects
Science & Technology
Physical Sciences
Technology
Thermodynamics
Energy & Fuels
Engineering, Multidisciplinary
Engineering, Chemical
Engineering, Mechanical
Engineering
Turbulent premixed flames
Multi-fluid statistics
Fuel effects
Combustion chemistry
Damkohler number scaling
OPPOSED-JET FLAMES
DIMETHYL ETHER DME
MILD COMBUSTION
DELAY TIMES
TEMPERATURE
IGNITION
ETHANOL
AUTOIGNITION
EXTINCTION
OXIDATION
Publication Status
Published online
Date Publish Online
2020-05-28