lonely是什么意思>s1 no 1 styleA Comprehensive Modeling Study of Hydrogen Oxidation
MARCUS´O CONAIRE,1HENRY J.CURRAN,2JOHN M.SIMMIE,1WILLIAM J.PITZ,3 CHARLES K.WESTBROOK3
1National University of Ireland,Galway,Ireland
2Galway-Mayo Institute of Technology,Galway,Ireland
3Lawrence Livermore National Laboratory,Livermore,CA94551
Received19November2003;accepted28May2004
DOI10.1002/kin.20036
Published online in Wiley InterScience(www.).
ABSTRACT:A detailed kinetic mechanism has been developed to simulate the combustion of
H2/O2mixtures,over a wide range of temperatures,pressures,and equivalence ratios.Over the
ries of experiments numerically investigated,the temperature ranged from298to2700K,the
pressure from0.05to87atm,and the equivalence ratios from0.2to6.
Ignition delay times,flame speeds,and species composition data provide for a stringent test
of the chemical kinetic mechanism,all of which are simulated in the current study with varying
success.A nsitivity analysis was carried out to determine which reactions were dominating
the H2/O2system at particular conditions of pressure,temperature,and fuel/oxygen/diluent
ratios.Overall,good agreement was obrved between the model and the wide range of exper-
iments simulated.C 2004Wiley Periodicals,Inc.Int J Chem Kinet36:603–622,2004
INTRODUCTION
The prospect of a hydrogen-bad economy has prompted incread interest in the u of hydrogen as a fuel given its high chemical energy per unit mass and cleanliness.It appears that most of the technologi-cal problems in using hydrogen in spark-ignited inter-nal combustion engines,including NO x emissions[1], have now been solved;vehicular on-board storage is probably the one remaining difficulty[2,3].
There is also continued interest in developing a bet-ter understanding of the oxidation of hydrocarbon fu-Correspondence to:Henry J.Curran;e-mail:henry.curran@ nuigalway.ie.
Contract grant sponsor:Higher Education Authority of Ireland.
Contract grant number:PRTLI-II.
c 2004Wiley Periodicals,Inc.els[4]over a wide range of operating conditions in order to increa efficiency an
d to reduc
e the emis-sion o
f pollutant species.All,or almost all petrochem-ical,fuels are hydrocarbons which burn to form carbon dioxide and water.Thus,the development of a detailed kinetic mechanism for hydrocarbon oxidation neces-sarily begins with a hydrogen/oxygen submechanism, followed by the addition of CO chemistry.
In recent years,many kinetic studies of hydrogen oxidation have concentrated on a single t of expe
ri-mental results obtained either in shock tubes,or inflow reactors or inflames;the have been simulated using a detailed kinetic mechanism.This procedure has been criticized recently by Smith[5]who asrts that uncer-tainty limits on individual reaction rate constants pro-duce a parameter space of possible mechanisms still too impreci for accurate prediction of combustion properties such asflame speed or ignition delay,thus
604´O CONAIRE ET AL.
requiring additional system data.Smith adds that low pressure and counterflowflames,mixtures in shock tubes,andflow or well-stirred reactors are examples of such experimental environments.It is the aim of this study to apply a hydrogen kinetic mechanism to as broad a range of combustion environments as possible.
There have been a very large number of measure-ments made on the reaction between hydrogen and oxy-gen.The includeflame speed measurements,burner-stabilizedflames in which species profiles are recorded, shock tube ignition delay times,and concentration pro-files inflow reactor studies.This study aims to simu-late the experiments using a detailed chemical kinetic mechanism which takes its origin from Mueller et al.
[6]in their study of hydrogen oxidation in aflow re-actor.Mueller and coworkers validated their mecha-nism using only theirflow reactor data over the tem-perature range850–1040K,at equivalence ratios of 0.3≤φ≤1.0,pressures of0.3to15.7atm and resi-dence times of0.004to1.5s.We have exercid their mechanism against shock-tube data,burner-stabilized flame experiments,andflame speed data and have made modifications to some of the kinetic parameters in or-der to achieve better overall agreement between mecha-nism simulations and this broader range of experimen-tal results.Previously,Marinov et al.[7]had also devel-oped a detailed H2/O2kinetic mechanism to simulate shock tube,flame speed,and burner-stabilizedflame experiments with good agreement between model and experiment but a large body of data ts have become available since then.Therefore,this study prents a new detailed chemical kinetic mechanism for hydro-gen oxidation but with incread attention paid to ex-periments conducted at high pressures since internal combustion engines operate at elevated pressures.
Davis et al.[8]have recently prented a re-examination of a H2/CO combustion mechanism in which they simulated some of the experimental data included in this study.Their work was motivated by new kinetic parameters for the important reaction ˙H+O
2+M=H˙O2+M and by new thermodynamic data for˙OH,and had the objective of optimizing their H2/
CO model against experiment.
IGNITION DELAYS IN SHOCK WAVES
Schott and Kiny[9]measured ignition delay times of two H2/O2/Ar fuel mixtures behind incident shock waves over a wide range of reactant densities in the temperature range1085–2700K and at1atm. Skinner and Ringro[10]measured the ignition de-lays of an H2/O2/Ar mixture in the temperature range 965–1076K and at a reflected shock pressure of 5atm.Asaba et al.[11]performed experiments in
the temperature range1500–2700K,at reflected shock
pressures of178–288Torr,at an equivalence ratio,φ,of
0.5and with98%argon dilution.Fujimoto and Sujiki
[12]measured ignition delay times of stoichiometric
H2/O2/Ar fuel mixtures in the reflected shock pressure
range1.3–5atm and in the temperature range700–
1300K.Hagawa and Asaba[13]measured ignition
delays in the temperature range920–1650K,at a re-
flected shock pressure of5.5atm,withφ=0.25at94%
argon dilution.Bhaskaran et al.[14]reported ignition
delay times for a29.59%H2,14.79%O2,55.62%N2
mixture in the temperature range1030–1330K and at
a constant reflected shock pressure of2.5atm.
More recently,Slack[15]studied stoichiometric
hydrogen–air mixtures in a shock tube and measured
induction times near the cond explosion limit.The
experiments were performed at a reflected shock pres-
sure of2atm in the temperature range980–1176K.
Cheng and Oppenheim[16]reported ignition delay
times for a6.67%H2,3.33%O2,and90%Ar mixture in
the temperature range1012–1427K and at a reflected
shock pressure,P5 1.9atm.Koike[17]measured ignition delay times for two hydrogen/oxygen/argon
fuel mixtures of incident shock pressure20Torr in the
temperature range1000–1040K.
In a methane shock-tube study,Hidaka et al.[18]
carried out some measurements of a H2/O2/Ar mix-
ture at1250–1650K and at reflected shock pressures
of1.6–2.8bar.Petern et al.[19]measured high-
刘一男pressure(33–87atm)H2/O2/Ar reflected shock igni-
健康美白
tion delays at1189–1876K and at an equivalence ratio
of1.0in every ca for six mixtures.Petern et al.
[20]measured reflected ignition delay times in three
highly dilute H2/O2/Ar mixtures at temperatures of
1010–1750K,equivalence ratio range1.0≤φ≤1.47
and around atmospheric pressure.Finally,Wang et al.
[21]carried out reflected shock measurements in vari-
ous H2/air/steam mixtures at954–1332K and pressures
of3.36–16.63atm.Hydrogen concentration was15%
of air throughout.
FLAME MEASUREMENTS
Atmospheric Flame Speed Measurements Very many hydrogen/airflame speed studies have been performed at atmospheric pressure,over various ranges of equivalence ratio.Koroll et al.[22]reported data in the equivalence ratio range0.15≤φ≤5.5, Iijima and Takeno[23]in the range0.5≤φ≤3.9,and Takahashi et al.[24]in the range1≤φ≤4.How-ever,the data did not account for the effects of flame stretch.
A COMPREHENSIVE MODELING STUDY OF HYDROGEN OXIDATION 605
The earliest stretch-corrected atmospheric hydro-gen/air flame speed experiments were performed by Wu and Law [25]in the range 0.6≤φ≤6.Since then,stretch-corrected flame speeds,all of which were per-formed at 1atm,have been reported at various equiva-lence ratio ranges:Egolfopoulos and Law [26](0.25≤φ≤1.5),Law [27](0.4≤φ≤1.5),Vagelopoulos et al.[28](0.3≤φ≤0.55),Dowdy et al.[29](0.3≤φ≤5),and Aung [30](0.3≤φ≤5)and T et al.[31](0.4≤φ≤4),Fig.1.
The measurements of Takahashi et al.[24]are con-siderably faster than the rest of the data and 10%faster than the intermediate values of T et al.and Dowdy et al.at an equivalence ratio of 1.75.The slowest flame speeds are tho of Aung et al.[30]that have a maxi-mum flame speed of 2.6
m s −1at φ=1.65.The authors point to possible greater stretch effects than accounted for to explain the relative slowness of their data.The Koroll et al.values [22],on the other hand,are much faster than any other between 1.0≤φ≤2.5.The re-cent flame speed measurements of Dowdy et al.[29]and T et al.[31]probably are the most reprenta-tive of the entire data t;they have a maximum flame speed of 2.85m s −1at φ=1.75.
Lamoureux et al.[32]very recently measured the speeds of freely propagating flames in a spherical bomb for five H 2/air mixtures using a diluent consisting of CO 2+He to mimic the effect of water vapor on flame speed.The mixtures were compod of as follows:x (40%He +60%CO 2)+(1−x )(H 2+air),where
x
Figure 1Atmospheric H 2/O 2/air flame speeds versus equivalence ratio,T i =298K. Koroll et al.[22], +Iijima and Takeno [23], Takahashi et al.[24];stretch corrected: ×Wu and Law [25]×Egolfopoulos and Law [26],•Law [27],⊕Vagelopoulos et al.[28], Dowdy et al.[29],+Aung et al.[30],and T et al.[31].
ranged from 0.0to 0.4,and with synthetic air of com-position O 2:N 2=20:80.
High-Pressure Flame Speeds
In addition to their atmospheric flame speed measure-ments,T et al.[31]also measured mass burning velocities for H 2/O 2/He mixtures in the equivalence ratio range 0.5≤φ≤3.5and between 1and 20atm at an initial temperature of 298K.It was reported that flames became increasingly unstable at elevated pres-sures.For this reason,true stretch-free flame speeds become more diffcult to measure.Experimentally,in the ca of the 10–20atm data,the oxygen to fuel ratio was reduced to suppress diffusional-thermal instabil-ity and delay hydrodynamic instability.Using helium as the diluent also helped minimize instability up to 20atm by reducing the Lewis number of the flame and retarding the formation of flame cells.Stretch-free flame speeds have only been available up to a few at-mospheres.The oxygen to helium ratio at 1to 5atm was 1:7(12%dilution)and at elevated pressures,this ratio was 1:11.5(8%dilution).
Burner-Stabilized Flame
In their investigation of a rich 18.83%hydrogen,4.6%oxygen,and 76.57%nitrogen flame at atmospheric pressure,Dixon-Lewis and Sutton [33]measured the temperature pro file and the concentration pro files of the stable species in the flame,above and below the burner.Flame structure measurements had been car-ried out by Koh-H ¨Oinghaus et al.[34]who measured
˙H
and ˙OH radical concentrations versus distance in a H 2/O 2/Ar flame,at a pressure of 95mbar,in the equiva-lence ratio range 0.6≤φ≤1.4and in the temperature range 1100–1350K.Vandooren and Bian [35]investi-gated the structure of a rich H 2/O 2/Ar flame over a flat burner at a pressure of 35.5Torr and at an equivalence
ratio of 1.91.They reported H 2,O 2,H 2O,˙H,
˙O,and ˙OH species mole fractions versus distance above the burner.
Flow Reactors
Mueller et al.[6]measured H 2,O 2,and H 2O pro files over the temperature range 850to 1040K,at equiva-lence ratios of 0.3≤φ≤1.0in the pressure range from 0.3to 15.7atm and over a range of residence times of 0.004to 1.5s.Previously,Yetter et al.[36]reported atmospheric H 2,O 2,and H 2O pro files at 910K,and at an equivalence ratio of 0.3.
606´O CONAIRE ET AL.
Experiments Simulated
A reprentative lection of recent experimental work has been chon to validate the H2–O2combustion mechanism.The chon experiments were
1.the ignition delay times measured by Schott and
Kiny[9],Skinner and Ringro[10],Fujimoto
and Suzuki[12],Bhaskaran and Gupta[14],
Slack[15],Cheng and Oppenheim[16],Petern
et al.[19],Hidaka et al.[18],Petern et al.[20],
and Wang et al.[21].Simulations of the data
of Asaba et al.[11],Hagawa and Asaba[13],
and Koike[17]were not attempted in this study
becau of a lack of sufficient information.
2.theflame speed measurements of Dowdy et al.
[29].Theflame speeds not only span a wide
range of equivalence ratio but are in agreement
with the more recent values of T et al.[31].
Dowdy and coworkers also measured the tem-
perature profiles,thus making their data more
amenable to simulation.
3.the high-pressureflame speed measurements of
T et al.[31].This data is the only t where
hydrogenflame speeds have been measured at
pressures greater than5atm.
4.the very lean H2/air and H2/air/CO2/Heflame
speed measurements of Lamoureux et al.[32].
5.the burner-stabilizedflame profiles of Vandooren
and Brian[35]in which reactant and intermedi-
ate species concentrations were measured as a
function of height above the burner surface.Also
included are the species profiles of Dixon-Lewis
and Sutton[33].
关于秋天的成语6.the comprehensiveflow reactor data of Mueller
et al.[6]along with a single data t from Yetter
et al.[36].
CHEMICAL KINETIC MODELING
The chemical kinetic mechanism was developed and simulations performed using the HCT program[37]. Initially,ignition delay times measured by Slack[15], Fig.8,and Hidaka et al.[18],Fig.7,and theflow re-actor experiments of Mueller et al.[6],Fig.25,were simulated with very good agreement obrved between experiment and model.The mechanism was then con-verted into Chemkin3.6[38]format and the simula-tions repeated in order to compare results from both codes,which were in very good agreement as expected. Thereafter,all other experiments including theflame speeds and the burner-stabilizedflame profiles were simulated using only the Chemkin applications.Thermodynamic and Transport Properties The H2/O2reaction mechanism consists of19
reversible elementary reactions,Table I,together
with the thermochemical data,Table II.Rever rate
coldcallconstants were computed by microscopic reversibility.
The thermochemical data for each species considered
in the mechanism are from the Chemkin thermody-
namic databa[51]with the exception of two:
1. H f(H˙O2,298K)of3.0kcal mol−1,from Hills
and Howard[52]which is in good agreement
with the recent reappraisal by Ramond et al.[53]
of3.2±0.5kcal mol−1.
2. H f(˙OH,298K)of8.91kcal mol−1which is
bad on recommendations by Ruscic et al.[54]
and Herbon et al.[55].
The Chemkin databa of transport parameters was
ud without modification.As in the study of T
et al.[31],the kinetic parameters of helium were as-
sumed equal to tho of argon in order to simulate
flame propagation where helium is the diluent.As T
d,using the third-body efficiency of argon for
monatomic helium is a uful starting estimate;ther-
molecular reactions such as˙H+O2+M=H˙O2+M become significant at elevated pressures and so the un-
certainties in the values can create considerable dif-
ferences in theflame speeds.
Mechanism Formulation
The kinetic mechanism referred to in this study as this
study or the revid mechanism has its origins in the CO/H2/O2reaction mechanism of Yetter et al.[56], which was updated later by Kim et al.[57]and is,for the most part,taken from the more recent work of Mueller et al.[6].
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We found it necessary to modify some of the kinetic
parameters of Mueller et al.in order to achieve an over-
all improvement with all the experimental data sim-
ulated here.This altered version of the mechanism,
Table I,the revid mechanism,reproduces the -
lected experimental datats more accurately than that
published by Mueller and coworkers.
要学习化妆
The entire data t has also been simulated using rel-
evant portions from Leeds1.5[58],Konnov[59,60]and
GRI-Mech3.0[61]which are all primarily methane ox-
idation mechanisms.The reason for using both Konnov
mechanisms is that the shock tube data prented in
Figs.4–6was ud to validate version0.3,while the
more recent version0.5was ud to simulate the re-
maining data.A lect t of experiments is repro-
duced here using GRI-Mech,Leeds,and Konnov as
A COMPREHENSIVE MODELING STUDY OF HYDROGEN OXIDATION607
Table I Revid H2/O2Reaction Mechanism(units:cm3,mol,s,kcal,K)
Reaction A n E a Ref.
H2/O2chain reactions
1˙H+O2=˙O+˙OH1.91×10140.0016.44[39]
2˙O+H2=˙H+˙OH5.08×104 2.67 6.292[40]
3˙OH+H2=˙H+H2O2.16×108 1.51 3.43[41]
4˙O+H2O=˙OH+˙OH2.97×106 2.0213.4[42]
H2/O2dissociation/recombination reactions
5a H2+M=˙H+˙H+M4.57×1019−1.40105.1[43]
pto
单眼皮的化妆技巧6b˙O+˙O+M=O2+M6.17×1015−0.500.00[43]
7c˙O+˙H+M=O˙H+M4.72×1018−1.000.00[43]
8d,e˙H+˙OH+M=H2O+M4.50×1022−2.000.00[43]×2.0
Formation and consumption of H˙O2
9f,g˙H+O2+M=H˙O2+M3.48×1016−0.41−1.12[44]˙H+O
2=H˙O21.48×10120.600.00[45] 10H˙O2+˙H=H2+O21.66×10130.000.82[6]
11H˙O2+˙H=˙OH+˙OH7.08×10130.000.30[6]
12H˙O2+˙O=˙OH+O23.25×10130.000.00[46] 13H˙O2+˙OH=H2O+O22.89×10130.00−0.50[46]
Formation and consumption of H2O2
14h H˙O2+H˙O2=H2O2+O24.2×10140.0011.98[47] H˙O2+H˙O2=H2O2+O21.3×10110.00−1.629[47] 15i,f H2O2+M=˙OH+O˙H+M1.27×10170.0045.5[48] H2O2=˙OH+O˙H2.95×10140.0048.4[49] 16H2O2+˙H=H2O+˙OH2.41×10130.00 3.97[43] 17H2O2+˙H=H2+H˙O26.03×10130.007.95[43]×1.25 18H2O2+˙O=˙OH+H˙O29.55×1006 2.00 3.97[43] 19h H2O2+˙OH=H2O+H˙O21.0×10120.000.00[50] H2O2+˙OH=H2O+H˙O25.8×10140.009.56[50]
a Efficiency factors are H2O=12.0;H2=2.5.
b Efficiency factors are H2O=12;H2=2.5;Ar=0.83;He=0.83.
c Efficiency factors are H2O=12;H2=2.5;Ar=0.75;He=0.75.
d Original pre-exponential A factor is multiplied by2here.
e Efficiency factors are H2O=12;H2=0.73;Ar=0.38;He=0.38.
f Troe parameters:reaction9,a=0.5,T∗∗∗=1.0×−30,T∗=1.0×10+30,T∗∗=1.0×10+100;reaction15,a=0.5,T∗∗∗=1.0×−30, T∗=1.0×10+30.
g Efficiency factors are H2=1.3;H2O=14;Ar=0.67;He=0.67.
h Reactions14and19are expresd as the sum of the two rate expressions.
i Efficiency factors are H2O=12;H2=2.5;Ar=0.45;He=0.45;
Table II H f(298.15K)kcal mol−1,S(300K)and C p(T)in cal mol−1K−1
Specific heat capacity,C p
Species H298K
S300K300K400K500K800K1000K1500K f
˙H52.09827.422 4.968 4.968 4.968 4.968 4.968 4.968˙O59.5638.500 5.232 5.139 5.080 5.016 4.999 4.982˙OH8.9143.933 6.947 6.9927.0367.1997.3417.827 H20.0031.256 6.902 6.960 6.9977.0707.2097.733 O20.0049.0507.0107.2207.4378.0688.3508.721 H2O−57.7745.1548.0008.2318.4469.2239.87511.258 H˙O2 3.0054.8098.3498.8869.46510.77211.38012.484 H2O2−32.5355.72410.41611.44612.34614.29415.21316.851 N20.0045.900 6.8207.1107.5207.7708.2808.620 Ar0.0037.000 4.900 4.900 4.900 4.900 4.900 4.900 He0.0030.120 4.970 4.970 4.970 4.970 4.970 4.970
