Uncertainty in stretch extrapolation of laminar flame speed from expanding spherical flames

Wu, Fujia; Liang, Wenkai; Chen, Zheng; Ju, Yiguang; Law, Chung K.

doi:10.1016/j.proci.2014.05.065

Cited by 181 publications

(96 citation statements)

References 28 publications

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“…Data from Saeed et al [7] were estimated from the pressure-time history, which could be affected by flame instability and heat loss. There are some inconsistencies in the flame speed extrapolation using spherical flames with different chamber shapes and sizes especially when the mixture Lewis number is much less or larger than unity [42]. Conservative estimates of radiation-induced uncertainty in spherically expanding flames [27] predict a maximum inhibition of 3.7% for the PU measurements and 6.1% for the TAMU measurements.…”

Section: Laminar Flame Speed Resultsmentioning

confidence: 99%

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

Burke

Donagh

et al. 2015

Combustion and Flame

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Experimental data obtained in this study (Part II) complement the speciation data presented in Part I, but also offer a basis for extensive facility cross-comparisons for both experimental ignition delay time (IDT) and laminar flame speed (LFS) observables.To improve understanding of the ignition characteristics of propene, a series IDT experiments were performed in six different shock tubes and two rapid compression machines (RCMs) under conditions not previously studied. This study is the first of its kind to directly compare ignition in several different shock tubes over a wide range of conditions. For common nominal reaction conditions among these facilities, cross-comparison of shock tube IDTs suggests 20-30% reproducibility (2σ) for the IDT observable. The combination of shock tube and RCM data greatly expands the data available for validation of propene oxidation models to higher pressures (2-40 atm) and lower temperatures (750-1750 K).Propene flames were studied at pressures from 1-20 atm and unburned gas temperatures of 295-398 K for a range of equivalence ratios and dilutions in different facilities. The present propene-air LFS results at 1 atm were also compared to LFS measurements from the literature. With respect to initial reaction conditions, the present experimental LFS cross-comparison is not as comprehensive as the IDT comparison; however, it still suggests reproducibility limits for the LFS observable. For the LFS results, there was agreement between certain data sets and for certain equivalence ratios (mostly in the lean region), but the remaining discrepancies highlight the need to reduce uncertainties in laminar flame speed experiments amongst different groups and different methods. Moreover, this is the first study to investigate the burning rate characteristics of propene at elevated pressures (> 5 atm).IDT and LFS measurements are compared to predictions of the chemical kinetic mechanism presented in Part I and good agreement is observed.

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Section: Laminar Flame Speed Resultsmentioning

confidence: 99%

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

Burke

Donagh

et al. 2015

Combustion and Flame

Self Cite

288

208

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“…The un-stretched flame propagation speed S b,0 is then calculated through extrapolation to zero stretch using the linear stretch relation (for mixtures with near unity Lewis number), although the curvature method [22] gives results within 5%. Low extrapolation uncertainty is expected, as -0.1 < Ma x Ka < 0.2 for all measurements [25]. Extrapolation endpoints are determined iteratively by locating the range where the residuals from the fit are below a threshold value and using this range to compute a new fit.…”

Section: Princeton University Flamesmentioning

confidence: 99%

A comprehensive experimental and modeling study of isobutene oxidation

Zhou

O'Connor

et al. 2016

Combustion and Flame

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Isobutene is an important intermediate in the pyrolysis and oxidation of higher-order branched alkanes, and it is also a component of commercial gasolines. To better understand its combustion characteristics, a series of ignition delay time (IDT) and laminar flame speed (LFS) measurements have been performed. In addition, flow reactor speciation data recorded for the pyrolysis and oxidation of isobutene is also reported. Predictions of an updated kinetic model described herein are compared with each of these data sets, as well as with existing jet-stirred reactor (JSR) species measurements.IDTs of isobutene oxidation were measured in four different shock tubes and in two rapid compression machines (RCMs) under conditions of relevance to practical combustors. The combination of shock tube and RCM data greatly expands the range of available validation data for isobutene oxidation models to pressures of 50 atm and temperatures in the range 666-1715 K. Isobutene flame speeds were measured experimentally at 1 atm and at unburned gas temperatures of 298-398 K over a wide range of equivalence ratios. For the flame speed results, there was good agreement between different facilities and the current model in the fuel-rich region.Ab initio chemical kinetics calculations were carried out to calculate rate constants for important reactions such as H-atom abstraction by hydroxyl and hydroperoxyl radicals and the decomposition of 2-methylallyl radicals.A comprehensive chemical kinetic mechanism has been developed to describe the combustion of isobutene and is validated by comparison to the presently considered experimental measurements. Important reactions, highlighted via flux and sensitivity analyses, include: (a) hydrogen atom abstraction from isobutene by hydroxyl and hydroperoxyl radicals, and molecular oxygen; (b) radical-radical recombination reactions, including 2-methylallyl radical self-recombination, the recombination of 2-methylallyl radicals with hydroperoxyl radicals; and the recombination of 2-methylallyl radicals with methyl radicals; (c) addition reactions, including hydrogen atom and 2 hydroxyl radical addition to isobutene; and (d) 2-methylallyl radical decomposition reactions. The current mechanism accurately predicts the IDT and LFS measurements presented in this study, as well as the JSR and flow reactor speciation data already available in the literature.The differences in low-temperature chemistry between alkanes and alkenes are also highlighted in this work. In normal alkanes, the fuel radical Ṙ adds to molecular oxygen forming alkylperoxyl (RȮ 2 ) radicals followed by isomerization and chain branching reactions which promote low-temperature fuel reactivity. However, in alkenes, because of the relatively shallow well (~20 kcal mol -1 ) for RȮ 2 formation compared to ~35 kcal mol -1 in alkanes, the Ṙ + O 2 ⇌ RȮ 2 equilibrium lies more to the left favoring Ṙ + O 2 rather than RȮ 2 radical stabilization. Based on this work, and related studies of allylic systems, it is apparent that reactivity fo...

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“…Specifically, a variety of experimental data sets for CH 4 /air reported in the literature [13][14][15][16][17][18][19][20][21][22][23][24][25][26] is collected to show the differences in S 0 u measurement using the OPF method. Moreover, effects of mixture preparation [5,9,27,28], ignition [29][30][31][32], buoyancy [33,34], instability [35][36][37], confinement [38][39][40][41], radiation [9,10,[41][42][43][44], nonlinear stretch behavior [22,[45][46][47][48][49], and extrapolation [50,51] on the discrepancies in S 0 u measurement are examined based on 1-D simulation of propagating planar and spherical flames. It should be noted that Egolfopoulos et al [5] have recently reviewed possible sources of uncertainty in S 0 u measurement using the OPF method.…”

Section: Introductionmentioning

confidence: 99%

On the accuracy of laminar flame speeds measured from outwardly propagating spherical flames: Methane/air at normal temperature and pressure

Chen

2015

Combustion and Flame

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230

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Uncertainty in stretch extrapolation of laminar flame speed from expanding spherical flames

Cited by 181 publications

References 28 publications

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

A comprehensive experimental and modeling study of isobutene oxidation

On the accuracy of laminar flame speeds measured from outwardly propagating spherical flames: Methane/air at normal temperature and pressure

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