Properties of Laminar Premixed Hydrocarbon/Air Flames at Various Pressures

Hassan, M. I.; Аунг, К.; Kwon, Oh Chae; Faeth, G. M.

doi:10.2514/2.5304

Cited by 122 publications

(66 citation statements)

References 19 publications

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“…Fig. 21 compares ASRs for all the gaseous-HC extinction limits, from the 7.5 mm tube-OJB, with recently surveyed / published unstrained laminar burning velocity, S L,0 , measurements [37,38] at an equivalence ratio of unity (phi = 1). And, Fig.…”

Section: Comprehensive "Idealized Flameholding Scale" For Hcs H 2 Anmentioning

confidence: 99%

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Pellett¹,

Convery²,

Wilson³

2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Opposed Jet Burner (OJB) tools have been used extensively by the authors to measure Flame Strength (FS) extinction limits of laminar H 2 /N 2 -air and (recently) hydrocarbon (HC)-air Counterflow Diffusion Flames (CFDFs) at one atm. This paper details normalization of FSs of N 2 -diluted H 2 and HC systems to account for effects of fuel composition, temperature, pressure, jet diameter, inflow Reynolds number, and inflow velocity profile (plug, contoured nozzle; and parabolic, straight tube). Normalized results exemplify a sensitive accurate means of validating, globally, reduced chemical kinetic models at ~ 1 atm and the relatively low temperatures approximating the loss of non-premixed "idealized" flameholding, e.g., in scramjet combustors.Laminar FS is defined locally as maximum air input velocity, U air , that sustains combustion of a counter-jet of g-fuel at extinction. It uniquely characterizes a fuel. And global axial strain rate at extinction (U air normalized by nozzle or tube diameter, D n or t ) can be compared directly with computed extinction limits, determined using either a 1-D Navier Stokes stream-function solution, using detailed transport and finite rate chemistry, or (better yet) a detailed 2-D Navier Stokes numerical simulation. The experimental results define an "idealized flameholding reactivity scale" that shows wide ranging (50 x) normalized FS's for various vaporized-liquid and gaseous HCs, including, in ascending order: JP-10, methane, JP-7, n-heptane, n-butane, propane, ethane, and ethylene. Results from H 2 -air produce a unique and exceptionally strong flame that agree within ~1% of a recent 2-D numerically simulated FS for a 3 mm tube-OJB. Thus we suggest that experimental FS's and/or FS ratios, for various neat and blended HCs w/ and w/o additives, offer accurate global tests of chemical kinetic models at the Ts and Ps of extinction.In conclusion, we argue the FS approach is more direct and fundamental, for assessing, e.g., idealized scramjet flameholding potentials, than measurements of laminar burning velocity or blowout in a Perfectly Stirred Reactor, because the latter characterize premixed combustion in the absence of aerodynamic strain. And FS directly measures a chemical kinetic characteristic of non-premixed combustion at typical flameholding temperatures. It mimics conditions where gfuels are typically injected into a subsonic flameholding recirculation zone that captures air, where the effects of aerodynamic strain and associated multi-component diffusion become important.

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Section: Comprehensive "Idealized Flameholding Scale" For Hcs H 2 Anmentioning

confidence: 99%

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Pellett¹,

Convery²,

Wilson³

2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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“…While further improvement is still needed, the current version is much improved over the original one as a result of the experiments and modeling presented in Kopp et al [1] and the present paper, respectively. ... [2] ... [9] ... [4] ... [13] ... [11] ... [12] ... [16] ... [8] ... [17] ... [7] ... [14] ... [10] ... [15] ... [19] ... [5] ... [20] ... [6] ... [21] ... [1] ... [22] ... [18] ... [23] Ċ ... [34] ... [31] ... [35] ... [32] ... [36] ... [33] ... [30] ... [37] ... [26] ... [38] ... [27] ... [39] ... [28] ... [40] ... [24] ... [41] ... [25] ... [42] …”

Section: Discussionmentioning

confidence: 99%

“…Such comparisons were made throughout the development of the current version of the mechanism. Laminar flame speed data from Egolfoupolos et al [40], Hassan et al [41], and Jomass et al [42] are available for ethyleneair mixtures at pressures from 1 to 5 atm. Un-stretched, unburned gas laminar flame speeds were calculated using Chemkin Pro [2]; solutions converged to GRAD and CURV values of 0.02 (> 800 grid points) utilizing mixtureaveraged transport equations including thermal diffusion effects.…”

Section: Model Comparisons and Validationmentioning

confidence: 99%

Oxidation of Ethylene—Air Mixtures at Elevated Pressures, Part 2: Chemical Kinetics

Kopp¹,

Petersen²,

Metcalfe³

et al. 2014

Journal of Propulsion and Power

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“…14 compares ASRs for the gaseous-HC extinction limits, from the 7.5 mm tube-OJB, with recently surveyed / published unstrained laminar burning velocity, S L,0 , measurements [48,49] at an equivalence ratio of unity (phi = 1). And, Fig.…”

Section: Comparison Of Flame Strengths With Laminar Burning Velocitiesmentioning

confidence: 99%

Opposed Jet Burner Extinction Limits: Simple Mixed Hydrocarbon Scramjet Fuels vs Air

Pellett

Vaden²,

Wilson

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Opposed Jet Burner tools have been used extensively by the authors to measure Flame Strength (FS) of laminar non-premixed H 2 -air and simple hydrocarbon (HC)-air counterflow diffusion flames at 1-atm. FS represents a strain-induced extinction limit based on air jet velocity. This paper follows AIAA-2006-5223, and provides new HC-air FSs for global testing of chemical kinetics, and for characterizing "idealized flameholding potentials" during early scramjet-like combustion. Previous FS data included six HCs, pure and N 2 -diluted; and three HC-diluted H 2 fuels, where FS decayed very nonlinearly as HC was added to H 2 , due to H-atom scavenging. This study presents FSs on mixtures of (candidate surrogate) HCs, some with very high FS ethylene. Included are four binary gaseous systems at 300 K, and a "hot" ternary system at ~ 600 K. The binaries are methane + ethylene, ethane + ethylene, methane + ethane, and methane + propylene. The first three also form two ternary systems. The hot ternary includes both 10.8 and 21.3 mole % vaporized nheptane and full ranges of methane + ethylene. Normalized FS data provide accurate means of (1) validating, globally, chemical kinetics for extinction of non-premixed flames, and (2) estimating (scaling by HC) the loss of "incipient" flameholding in scramjet combustors. The n-heptane is part of a proposed "baseline simulant" (10 mole % with 30% methane + 60% ethylene) that "mimics" the ignition of endothermically cracked JP-7 "like" kerosene fuel, as suggested by Colket and Spadaccini in 2001 in their shock tube "Scramjet Fuels Autoignition Study." Presently, we use FS to gauge idealized flameholding, and define HC surrogates. First, FS was characterized for hot nheptane + methane + ethylene; then a hot 36 mole % methane + 64% ethylene surrogate was defined that mimics FS of the "baseline simulant" system. A similar hot ethane + ethylene surrogate can also be defined, but it has lower vapor pressure at 300 K, and thus exhibits reduced gaseous capacity. The new FS results refine our earlier "idealized reactivity scale" that shows wide ranging (50 x) diameter-normalized FSs for various HCs. These range from JP-10 and methane to H 2 -air, which produces an exceptionally strong flame that agrees within ~1% of recent 2-D numerically simulations. Finally, we continue advocating the FS approach as more direct and fundamental, for assessing idealized scramjet flameholding potentials, than measurements of "unstrained" laminar burning velocity or blowout in a Perfectly Stirred Reactor.

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Properties of Laminar Premixed Hydrocarbon/Air Flames at Various Pressures

Cited by 122 publications

References 19 publications

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Oxidation of Ethylene—Air Mixtures at Elevated Pressures, Part 2: Chemical Kinetics

Opposed Jet Burner Extinction Limits: Simple Mixed Hydrocarbon Scramjet Fuels vs Air

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