Match!

On the chemical characteristics and dynamics of n-alkane low-temperature multistage diffusion flames

Published on Jan 1, 2019
· DOI :10.1016/j.proci.2018.06.161
Omar R. Yehia2
Estimated H-index: 2
(Princeton University),
Christopher B. Reuter8
Estimated H-index: 8
(Princeton University),
Yiguang Ju57
Estimated H-index: 57
(Princeton University)
Abstract
Abstract We demonstrate experimentally, perhaps for the first time, the existence of low-temperature multistage diffusion flames of n -alkanes. Multistage diffusion flames of n -heptane, n -decane, and n -dodecane are established in an atmospheric counterflow burner. Planar laser-induced fluorescence, chemiluminescence, and thermometry are used to probe the structures of such flames. In the first flame zone, the majority of the fuel is partially oxidized via low-temperature peroxy chemistry. In the second flame zone, the intermediate species produced are further oxidized via intermediate-temperature chemistry. The two stages of the flame are coupled such that significant fuel and oxidizer leakage occur, respectively, from the first and second reaction zones. The fuel is then further consumed, in the second stage, after the radical pool is replenished by the oxidation of the intermediates. The structure of the n -alkane multistage flame is found to be consistent with that previously observed for acyclic ethers. Owing to the different classes of temperature-dependent chemistries dominating the first and second stages, the reaction zone structure of multistage diffusion flames is dramatically influenced by the reactant concentrations and flame temperatures. The first stage is relatively favored at lower temperatures whereas the second stage is favored at elevated temperatures. Moreover, near extinction where the flame temperature is low, the multistage flame dynamics are controlled by the first oxidation stage, governed by peroxy chemistry, whereas the second oxidation stage, governed by intermediate chemistry, is dominant near high-temperature ignition conditions. Finally, by doping the oxidizer with ozone, we demonstrate the role of ozone doping on the multistage flame structure and the existence of a separate low-temperature ozone-assisted burning mode.
  • References (15)
  • Citations (0)
📖 Papers frequently viewed together
7 Citations
6 Citations
2015
5 Authors (Sang Hee Won, ..., Yiguang Ju)
56 Citations
78% of Scinapse members use related papers. After signing in, all features are FREE.
References15
Newest
#1Omar R. Yehia (Princeton University)H-Index: 2
#2Christopher B. Reuter (Princeton University)H-Index: 8
Last. Yiguang Ju (Princeton University)H-Index: 57
view all 3 authors...
7 CitationsSource
#1Christopher B. Reuter (Princeton University)H-Index: 8
#2Minhyeok Lee (Princeton University)H-Index: 2
Last. Yiguang Ju (Princeton University)H-Index: 57
view all 4 authors...
Abstract The low-temperature oxidation of hydrocarbon fuels has received increasing attention as advanced engines seek to operate in less conventional combustion regimes. Large n -alkanes are a notable component of many real transportation fuels and possess strong reactivity in this important low-temperature range. These n -alkanes have been studied extensively in various canonical kinetic experiments but seldom in systems with strong coupling between low-temperature chemistry, transport, and he...
19 CitationsSource
#1Yiguang Ju (Princeton University)H-Index: 57
Abstract The flame speeds and propagation limits of premixed cool flames at elevated pressures are numerically modeled using dimethyl ether mixtures. The primary focus is paid on the effects of pressure, mixture dilution, computation domain, and heat loss on cool flame propagation. The results showed that cool flames exist on both fuel lean and fuel rich sides and dramatically extend the lean and rich flammability limits of conventional hot flames. There exist three different flame regimes: the ...
20 CitationsSource
#1Hao Zhao (Princeton University)H-Index: 7
#2Xueliang Yang (Princeton University)H-Index: 10
Last. Yiguang Ju (Princeton University)H-Index: 57
view all 3 authors...
Abstract The ozone assisted low temperature oxidation chemistry of dimethyl ether (DME) from 400 K to 750 K has been investigated in the mixture of DME/O3/O2/He/Ar in an atmospheric-pressure flow reactor coupled with the molecular beam mass spectrometry (MBMS) sampling technique. The mole fraction of ozone was varied from 0 to 0.146% in the mixture to study its enhanced kinetic effect on DME oxidation. The mole fractions of DME, O2, O3, CH2O, H2O2, CO, CO2, and CH3OCHO were quantified as functio...
22 CitationsSource
#1Liming Cai (RWTH Aachen University)H-Index: 11
#2Heinz Pitsch (RWTH Aachen University)H-Index: 53
Last. S.M. Sarathy (KAUST: King Abdullah University of Science and Technology)H-Index: 27
view all 7 authors...
This work was performed within the Cluster of Excellence “Tailor-Made Fuels from Biomass”, which is funded by the Excellence Initiative of the German federal state governments to promote science and research at German universities. The authors also acknowledge funding support from the Clean Combustion Research Center and Saudi Aramco under the FUELCOM program. VR was supported by SERDP Grant WP-2151 with Dr. Robin Nissan as Program Manager. NUI Galway would like to acknowledge the support of the...
42 CitationsSource
#1Vedha NayagamH-Index: 15
#2Daniel L. DietrichH-Index: 13
Last. Forman A. WilliamsH-Index: 54
view all 3 authors...
A simplified model for droplet combustion in the partial-burning regime is applied to the cool-flame regime observed in droplet-burning experiments performed in the International Space Station with normal-alkanes fuels resulting in expressions for the quasi-steady droplet burning rate and for the flame standoff ratio. The simplified predictions are found to produce reasonable agreement with the experimentally measured values of burning-rate constants but not with their apparent dependencies on p...
12 CitationsSource
#1Christopher B. Reuter (Princeton University)H-Index: 8
#2Sang Hee Won (Princeton University)H-Index: 30
Last. Yiguang Ju (Princeton University)H-Index: 57
view all 3 authors...
Abstract Self-sustaining premixed cool flames are successfully stabilized in a dimethyl ether/oxygen counterflow burner through ozone addition, creating a new platform for the quantitative measurement of cool flame extinction limits, ignition limits, and structure as well as the validation of low-temperature chemical kinetic models. First, results show that stable premixed cool flames can exist over a broad region of equivalence ratios and strain rates, which allows for the ignition and extincti...
33 CitationsSource
#1Yiguang Ju (Princeton University)H-Index: 57
#2Christopher B. Reuter (Princeton University)H-Index: 8
Last. Sang Hee Won (Princeton University)H-Index: 30
view all 3 authors...
Abstract The formation and dynamics of premixed cool flames are numerically investigated by using a detailed kinetic mechanism of dimethyl ether mixtures in both freely-propagating and stretched counterflow flames with and without ozone sensitization. The present study focuses on the dynamics and transitions between cool flames and high temperature flames. The impacts of mixture temperature, inert gas temperature, and ozone concentration on low temperature ignition, cool flame formation, and fla...
41 CitationsSource
#1Tanvir Farouk (USC: University of South Carolina)H-Index: 18
#2Frederick L. Dryer (Princeton University)H-Index: 68
Abstract Recent experimentally observed two stage combustion of n -heptane droplets in microgravity is numerically studied. The simulations are conducted with detailed chemistry and transport in order to obtain insight into the features controlling the low temperature second stage burn. Predictions show that the second stage combustion occurs as a result of chemical kinetics associated with classical premixed “ Cool Flame ” phenomena. In contrast to the kinetic interactions responsible for premi...
59 CitationsSource
#1Vedha NayagamH-Index: 15
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last. Forman A. Williams (UCSD: University of California, San Diego)H-Index: 54
view all 5 authors...
Abstract Experimental observations of anomalous combustion of n-heptane droplets burning in microgravity are reported. Following ignition, a relatively large n-heptane droplet first undergoes radiative extinction, that is, the visible flame ceases to exist because of radiant energy loss. But the droplet continues to experience vigorous vaporization for an extended period according to a quasi-steady droplet-burning law, ending in a secondary extinction at a finite droplet diameter, after which a ...
73 CitationsSource
Cited By0
Newest