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SAFEKINEX - Deliverable No. 34 Validated detailed C1 - C3 kinetic oxidation model p. 1 (45)

S A F E K I N E X

SAFe and Efficient hydrocarbon oxidation processes by KINetics and

Explosion eXpertise and development of computational process engineering tools

Project No. EVG1-CT-2002-00072

Work-package 4

Contractual deliverable No. 34

Validated detailed C1 - C3 kinetic oxidation model

A.A. Konnov

Vrije Universiteit Brussel

Brussels, October 2005


1. INTRODUCTION ...................................................................................................................................... 3

1. MODELING DETAILS............................................................................................................................. 4 1.1 CHEMKIN COLLECTION OF CODES........................................................................................................... 4 1.2 THERGAS, EXGAS CODES (CNRS, NANCY) ............................................................................................ 4 1.3 TROT PRE-PROCESSOR........................................................................................................................... 5 1.4 IGDELAY 1.0 CODE .................................................................................................................................. 5 1.5 IN-HOUSE SEARCH/ANALYSIS CODE........................................................................................................ 5 1.6 MECHMOD CODE ................................................................................................................................. 5

2. STATUS OF THE MECHANISM VALIDATION AT THE MID-TERM ASSESSMENT............. 6

3. MECHANISM COMPONENTS .............................................................................................................. 7 3.1 SPECIES ................................................................................................................................................... 7

3.1.1 Problems encountered and solved ............................................................................................... 7 3.2 THERMODYNAMIC AND TRANSPORT DATA ............................................................................................. 8

3.2.1 Problems encountered and solved ............................................................................................... 9 3.3 REACTIONS AND RATE CONSTANTS ........................................................................................................ 9

3.3.1 Problems encountered and solved ............................................................................................. 10 4. VALIDATION OF THE MECHANISM............................................................................................... 10

4.1 HYDROGEN ........................................................................................................................................... 11 4.2 CARBON MONOXIDE.............................................................................................................................. 13 4.3 FORMALDEHYDE, CH2O ...................................................................................................................... 16 4.4 METHANOL, CH3OH............................................................................................................................ 18 4.5 METHANE, CH4 .................................................................................................................................... 21 4.6 ETHANE, C2H6 ..................................................................................................................................... 24 4.7 ETHYLENE, C2H4 ................................................................................................................................. 26 4.8 ACETYLENE, C2H2 ............................................................................................................................... 28 4.9 ACETALDEHYDE, CH3HCO ................................................................................................................. 30 4.10 ETHANOL, C2H5OH ........................................................................................................................ 32 4.11 ETHYLENE OXIDE, C2H4O............................................................................................................... 34 4.12 PROPANE, C3H8............................................................................................................................... 36 4.13 PROPENE, C3H6............................................................................................................................... 37 4.14 PROPYNE, C3H4............................................................................................................................... 40 4.15 PROPYLENE OXIDE, C3H6O............................................................................................................. 42

5. CONCLUDING REMARKS................................................................................................................... 43

6. REFERENCES ......................................................................................................................................... 43


1. Introduction

This deliverable is prepared at the VUB within the WP 4 "Kinetic model development" and presents validation of the C1 - C3 kinetic model performed within the Task 4.3.1. The present deliverable is essentially a continuation of the previous report on ongoing progress of C1 - C3 detailed kinetic model development performed within the Task 4.1.2 and accordingly reported in the deliverable No. 26. Therefore discussion on the importance of the C1 - C3 detailed kinetic model development for the WP 4 and state of the art are not included in the present report being presented in the deliverable No. 26. Strategy and methodology and mechanism components (species, rate constants, thermodynamic data) were also presented in the deliverable No. 26. Additional discussion on these issues is included in the present report to address modifications and progress since the mid-term meeting in Brussels (February 2005). According to the detailed Project plan the present deliverable was to be prepared in March 2005. However, during the mid-term meeting, project partners agreed to postpone its submission to October 2005. The reasons of this delay and problems encountered are therefore discussed in the present report. Then modifications to the C1 - C3 kinetic model are outlined. Finally validation of the mechanism is presented. Some results of the mechanism validation have been already published in scientific journals or presented at symposia. To avoid unnecessary duplication these papers/presentations are not copied in the present report but outlined shortly citing major accomplishments. Present report includes examples of validation through comparison with experiments in flow reactors, shock tubes, static reactors, that are essentially 0-dimensional problems. The modeling was also compared with available from the literature and obtained within the Project flame burning velocities of different mixtures. These results will be included in the Deliverable 15 “Validated model for laminar burning velocity” to be prepared within WP 3. The mechanism itself is a long listing and therefore it is not included in the report. The mechanism is available for the project partners and will be further disseminated through publications.


1. Modeling details Development and validation of the C1 - C3 kinetic model has been performed using several computer codes outlined below. 1.1 Chemkin collection of codes The most popular collection of codes for combustion modeling is the Chemkin from Sandia National Laboratories (Kee et al. 1990a, 1990b; Lutz et al. 1990). It was used for the modeling in the present work. To keep close consistency with the Chemkin presentation of the pressure-dependent rate constants and collisional efficiencies, similar notations are used in the mechanism. This reliable collection includes codes for the modeling of non-isothermal chemical phenomena, such as slow oxidation or ignition in uniform gas phase as they occur in constant volumes, in flow or well-stirred reactors. Also one-dimensional laminar premixed and diffusion flames can be modeled. The modeling codes provide a possibility to analyze the influence of the specific reaction rate constants on the resulting prediction of the process behavior, product formation, etc. This sensitivity analysis is used to reveal key reactions responsible for the appearance of combustion process. In the case when a limited number of the key reactions are responsible for the observed characteristics of the process (for example concentration of pollutant), the rate constants of these reactions can be adjusted to improve an agreement between the model and experiment. The Premix code, software for calculation of laminar burning velocity, is described in details in the SAFEKINEX contractual deliverable No. 14. 1.2 Thergas, Exgas codes (CNRS, Nancy) Thergas code (Muller et al., 1995) based on the group and bond additivity methods proposed by Benson (1976) was used to calculate thermodynamic data of the individual species (molecules and radicals) when this information was not retrieved from the databases of Burcat (2004) or from HiTempThermo data obtained from ab initio electronic structure calculations. Recent update of the Thergas code has been kindly provided by Dr. Glaude, P. A. The development of the mechanism at CNRS, Nancy (Glaude et al., 2000; Warth et al. 1998; Fournet et al. 2000) aimed at the construction of the computer-generated kinetic schemes for oxidation modeling of heavy hydrocarbons up to decane. The sophisticated software, EXGAS-ALKANES (Battin-Leclerc et al., 2004), is particularly suitable for combustion modeling at low and intermediate temperatures (600 – 2000 K) since it generates and estimates rate constants for the reactions typical for slow oxidation and cool flames, such as formation and isomerisation of RO2 radicals, peroxides, and also their decomposition and self-reactions. This mechanism is described in the SAFEKINEX Deliverable No. 27.


1.3 TROT pre-processor At TU/Eindhoven Evlampiev et al. (2004) recently developed TROT: a C++ interpreter for pre-processing and analysis of gas phase kinetics and thermodynamic properties. This pre-processor has additional possibilities to check consistency of thermodynamic data as compared to Chemkin interpreter. 1.4 Igdelay 1.0 code At Princeton University (USA) Kazakov (2004) developed Igdelay code to calculate ignition delays in homogeneous mixtures similar to the Chemkin code. However, different criteria to define ignition delay time are implemented: (1) dP/dt is at its maximum (most commonly used one), (2) [OH] is at its maximum; (3) [CO]x[O] is at its maximum (to mimic CO2 chemi-luminescence peak). Optionally, the code can also perform brute-force sensitivity analysis for implemented ignition delay criteria. 1.5 In-house search/analysis code Although modern word processors are able to perform different types of search in text files of the mechanism, more sophisticated options are often required. To search for reactions in which some species are consumed or formed, or to search for all reactions between two species, an in-house search/analysis code has been written. This code is also used on the web-page (Konnov, 2000) of the release 0.5 of the detailed mechanism for small hydrocarbons combustion. 1.6 MECHMOD code During the development of combustion mechanisms one has to do several mechanical things like converting the rate parameters from one unit to another, calculating the reverse rate parameters knowing the forward parameters and the thermodynamic data, or simply systematically eliminating some species from the mechanisms. To automate these tasks a utility program, called MECHMOD has been written (Turanyi, 2003). MECHMOD requires the usage of either the CHEMKIN-II or the CHEMKIN-III package. Using the CHEMKIN-II terminology, MECHMOD does the opposite to CKINTERP. CKINTERP creates a binary link (called chem.bin) file from a standard CHEMKIN mechanism text file, while MECHMOD restores the mechanism text file from the binary link file. In the CHEMKIN-III package, the mechanism interpreter is called chem.exe and the mechanism storage file is called chem.asc. In both cases, not only the original mechanism text file can be restored, but the mechanism can be modified in the following ways: - all reversible reactions are transformed to pairs of irreversible reactions - selected species are eliminated from the mechanism - the pre-exponential factors and the activation energies are converted to different units - the thermodynamic data are printed at the beginning of the mechanism. - the room-temperature heat of formation and entropy data are modified in the NASA polynomials.


2. Status of the mechanism validation at the mid-term assessment

According to the Project planning the validation of the C1-C3 mechanism was performed at temperatures higher than 550 K (up to 1600 K and higher) at pressures of 1 - 50 atm and for the mixtures having equivalence ratios from 0.5 to 2. The model was validated following its hierarchy starting from H2, CO, CH2O, CH3OH, CH4 and then C2H6, C2H4, C2H2, CH3HCO, C2H5OH, C2H4O (EtOx), C3H8, C3H6, C3H4, C3H6O (PrOx). At the time of the mid-term assessment reasonably good agreement was obtained for the following fuels: H2, CO, CH2O, CH3OH, CH4, C2H6, C3H8 (at high T), C3H6O. Satisfactory agreement was observed for: C2H4, C2H2, and C3H6. However, agreement of the modeling with selected experiments for CH3HCO, C2H5OH, C2H4O, C3H4, C3H8 (at lower T) was found unsatisfactory. Since the challenge of the development and validation of the C1-C3 mechanism was to create a single mechanism for the range of the fuels mentioned above, it was agreed by the Project partners to continue modification of the model and to postpone the present deliverable to October 2005. The team from CNRS, Nancy has published mechanisms suitable for the modeling of C3H6 (Heyberger et al., 2001) and for C2H2 and C3H4 (Fournet et al., 1999), also EXGAS-ALKANES (Battin-Leclerc et al., 2004) was available for the generation of, among others, C3H8 mechanism at lower temperatures. Therefore it was decided to combine these mechanisms with the C1-C3 mechanism available at this stage. Three detailed mechanisms have been combined:

- the C1-C3 mechanism under development - C3H6 mechanism (Heyberger et al., 2001) - C3H8 mechanism for low temperatures generated by the EXGAS-ALKANES code

(Battin-Leclerc et al., 2004). The mechanism for C2H2 and C3H4 (Fournet et al., 1999) was not used, because it was developed and validated using shock-tube experiments, which appeared to be incorrect as it will be discussed in the present report. Combination of these mechanisms was not a trivial task; it required re-development of the complete mechanism. Strategy and methodology of the mechanism development and mechanism components (species, rate constants, thermodynamic data) were presented in the deliverable No. 26. Additional discussion on these issues is included in the present report to address modifications and problems encountered. The (re-)development of the C1-C3 kinetic model includes the following steps: 1. Establishment of the list of C1 - C3 species and their intermediates relevant to the project goals and to the interest of industrial partners. 2. Establishment of a thermodynamic database for these species. 3. Compilation of the list of relevant reactions. The list includes all reactions important in the combustion and oxidation at temperatures higher than 550 K and at pressures of 1 - 50 atm.


3. Mechanism components A list of chemical reactions between a chosen set of species with associated rate constants is a major part of each comprehensive detailed reaction mechanism. When these reactions are written as irreversible ones, they can be used for isothermal chemical modeling. Modeling of the non-isothermal processes or calculation of the reverse reaction rate from the forward reaction rate constant requires thermodynamic data for each of the specie included in the mechanism. Besides, for the modeling of the non-uniform systems, such as one-dimensional flame, gas-phase viscosities, thermal conductivities and diffusion coefficients are to be calculated. In the following the criteria used for the preparation of the list of species and the origin of the reaction rate constants and thermodynamic data are outlined. 3.1 Species The criteria used to build up the list of the species participating in combustion of hydrocarbons depend on the desired or expected limits of the model applicability. In the present work the modeling is restricted to the non-sooting conditions, however some soot precursors (C4 - C6 species) were included in the list since they can be formed in the combustion of rich mixtures of the C1 - C3 hydrocarbon fuels. Oxygenated derivatives of hydrocarbons are included here since they can be formed in significant quantities during slow oxidation of hydrocarbons, particularly at low temperatures. Also some of them (e.g. alcohols) are considered as alternative fuels. Accurate description of the oxidation of hydrocarbons at low temperatures (600 – 1000 K) requires incorporation of a number of RO2 and RO2H species, aldehydes and corresponding radicals as well. The C1-C3 mechanism under development consisted of about 4000 reactions among 960 species. After combination with the two mechanisms mentioned above the mechanism listing was even bigger. Major task in the compilation of the species’ list was to reconstruct notations used in the mechanisms of CNRS, Nancy into normally accepted formulas. Also significant number of the species in these mechanisms was so-called lumped species. Most of them were “un-lumped” that is presented as real molecules or radicals. Sometimes this required introducing additional species. Problems encountered are discussed in the following sub-section. 3.1.1 Problems encountered and solved Low-temperature mechanisms developed at CNRS, Nancy (Glaude et al., 2000; Warth et al. 1998; Fournet et al. 2000) consist of two major parts:

- Primary mechanism, which describes initial stages of the fuel oxidation, formation of RO2 species, their isomerisation into e.g. QOOH, following reactions of decomposition and formation of OOQOOH species.

- Secondary mechanism describes the fate of the species formed within primary mechanism; it is in fact not detailed and includes many lumped species.

A consistency of the primary mechanism was checked and found to be good. However, many problems were discovered in the secondary mechanism. An example of the incorrect behaviour of the secondary mechanism is presented below. In this example C3H8O5


species generated in the primary mechanism are consumed through decomposition into OH radical and C2H4OHCOOOH species. These last species are lumped, their structure was not specified. The decomposition reactions have different rate constants according to generic rules implemented in the EXGAS-ALKANES code (Battin-Leclerc et al., 2004). CH3CHOO(CHOH)OOH=>OH+C2H4OHCOOOH 5.0D+09 1.000 35500.0 OOCH2COH(OOH)CH3=>OH+C2H4OHCOOOH 2.9D+08 1.000 27100.0 CH3(CO3H)CH2OOH=>OH+C2H4OHCOOOH 1.7D+09 1.000 34100.0 OOCH2CHOHCH2OOH=>OH+C2H4OHCOOOH 1.7D+09 1.000 29500.0 HOCH2CHOOCH2OOH=>OH+C2H4OHCOOOH 3.3D+09 1.000 32500.0 HOCHOOCH2CH2OOH=>OH+C2H4OHCOOOH 1.7D+09 1.000 35000.0 OOC2H4(CHOH)OOH=>OH+C2H4OHCOOOH 3.3D+09 1.000 32500.0 HOHCOO(CHOOH)CH3=>OH+C2H4OHCOOOH 1.7D+09 1.000 34100.0 OOCH2CHOOHCH2OH=>OH+C2H4OHCOOOH 1.7D+09 1.000 29500.0 However, the only reaction consuming C2H4OHCOOOH species is the following: C2H4OHCOOOH=>CH2O+CH2OH+OH+CO 7.0D+14 0.000 42000.0 Kinetically this means that the origin and the rate of accumulation of specific C3H8O5 species are masked by the last reaction. Product distribution cannot be predicted using this simplified approach. It is clear that complexity of the primary mechanism is spoiled by the lumping procedure in the secondary one. Another fault of the secondary mechanism generated by EXGAS-ALKANES code is “dead-end” reactions. About 60 species are only formed or only consumed. If the species are never formed and only consumed, they do not participate in the fuel consumption and product formation and can be easily removed from the mechanism. If the species are only formed, this leads to serious problems:

- additional artificial termination - inability to use this mechanism for equilibrium calculations.

Additional artificial termination of the reaction chains signifies that generic rate constants implemented in the primary mechanism are too high, because this is the only way to compensate excessive termination rate. Whenever possible additional reactions for these species were included in the mechanism, otherwise they were deleted from the mechanism. After thorough screening of the unnecessary reactions, the number of species was reduced to about 400. 3.2 Thermodynamic and transport data Whenever possible, thermodynamic data used were taken from the latest database of Burcat (2004). The second choice was HiTempThermo database. The database includes thermodynamic data (heats of formation, enthalpies, entropies, and heat capacities) for gas and condensed-phase species, thermodynamic models for specific condensed-phase material systems that account for non-ideal behavior in those systems, and a wide range of calculated molecular


properties for gas-phase species (vibrational frequencies, moments of inertia, etc.) Data for gas-phase species are obtained from ab initio electronic structure calculations. In most cases, the data were obtained from Bond Additivity Correction calculations (at either the MP4(SDTQ) or G2 level of theory). Data from coupled-cluster calculations and from literature sources are also included in cases where the BAC methods are either not applicable or have not yet been developed. In most cases, the data were obtained by C. F. Melius. This database is available at: http://www.ca.sandia.gov/HiTempThermo/index.html. For other species thermo-data were calculated using the software THERGAS (Muller et al., 1995), based on the group and bond additivity methods proposed by Benson (1976). Chemical species transport properties from Sandia National Laboratories have been largely used for the modeling (Kee et al. 1990c). 3.2.1 Problems encountered and solved Consistency of the thermodynamic data supplied with C3H6 mechanism (Heyberger et al., 2001) or generated by the EXGAS-ALKANES code (Battin-Leclerc et al., 2004) have been checked using TROT interpreter. In several dozens of cases the TROT code found wrong or inconsistent information manifested in: - jump of either enthalpy or heat capacity at 1000 K (junction point of NASA polynomials) - over- or under-estimated heat capacity. All appropriate thermodynamic data have been therefore recalculated using recent update of the Thergas code, which has been kindly provided by Dr. Glaude, P. A. 3.3 Reactions and rate constants Whenever possible, rate constants have been adopted from the recent review of Baulch et al. (2005). Otherwise the rate constants were looked up in the literature. In many cases different expressions of the rate of the same elementary reaction could be found in the literature. It is indispensable therefore to know and to analyze the auxiliary characteristics of each rate constant such as: - temperature range where it was determined, - pressure range, if reaction is pressure-dependent, - the source of the rate constant: measurements, theoretical calculations, estimations, review. Finally, in the absence of other sources the rate constants from the C3H6 mechanism (Heyberger et al., 2001) or from the EXGAS-ALKANES code (Battin-Leclerc et al., 2004) were employed. No attempts to modify or to adjust rate constants for the C4 and heavier species were made.


3.3.1 Problems encountered and solved The C3H6 mechanism (Heyberger et al., 2001) and the C3H8 mechanism generated by the EXGAS-ALKANES code (Battin-Leclerc et al., 2004) consist of one-way reactions (except the C0-C2 database, which was largely updated using review of Baulch et al., 2005). However, the approach adopted in the development of the present C1-C3 mechanism requires that all reactions were written as reversible. This provides additional opportunity to check consistency of the kinetic and thermodynamic data. To do so, the mechanism of reversible reactions has been transformed into the listing of irreversible reactions using MECHMOD code. When rate constants of the reversed reactions were found abnormally high or low, this reaction was analysed to find the source of the suggested rate constant and/or products formed. In fact, rate constants are often measured between known reactants but the products were unknown. Thus the analysis of the reverse reaction could show that suggested products are unrealistic. 4. Validation of the mechanism The strategy of the development and validation of kinetic schemes for H/C/O systems is based on hierarchical interrelationships of oxidation mechanisms for simple hydrocarbons and their oxygenated derivatives. This means that development of the mechanism should start from hydrogen and simplest hydrocarbons oxidation sub-mechanisms, subsequently extended to higher hydrocarbons and intermediates. It is clear that in many cases (mixtures) the complete range of the validation temperatures, pressures and equivalence ratios was not covered. For instance, flame burning velocities can only be modeled within flammability limits. At lower temperatures, there is important lack of reliable experimental data because heterogeneous processes can often mask the gas-phase chemistry to be modeled. In addition, in rich mixtures soot formation cannot be predicted accurately. Present report includes examples of validation through comparison with experiments in flow reactors, shock tubes, static reactors, that is essentially 0-dimensional problems. The mechanism was also compared with available from the literature and obtained within the Project flame burning velocities of different mixtures. These results are included in the Deliverable 15 “Validated model for laminar burning velocity” prepared within WP 3. In the following validation of the mechanism is presented. Some results of the mechanism validation have been already published in scientific journals or presented at symposia. To avoid unnecessary duplication these papers/presentations are not copied in the present report but outlined shortly citing major accomplishments.


4.1 Hydrogen Related publications KONNOV, A.A. Refinement of the Kinetic Mechanism of Hydrogen Combustion. In: Combustion and Atmospheric Pollution (G.D. Roy, S.M. Frolov, A.M. Starik, Eds.), Moscow, Torus Press ltd., 2003, pp. 35-40. KONNOV, A.A. Refinement of the Kinetic Mechanism of Hydrogen Combustion. Khimicheskaya Fizika , 23 (8): 5-18 (2004). HERMANNS, R.T.E., KONNOV, A.A., BASTIAANS, R.J.M., de GOEY, L.P.H. Laminar burning velocities of diluted hydrogen - oxygen - nitrogen mixtures. Submitted to Int. J. Hydrogen Energy, June 2005 Contemporary reaction mechanisms for H2 - O2 system have been reviewed and evaluated. New accurate measurements of the elementary reaction rates and updates in the thermodynamic data require its extensive validation. The contemporary choice of the reaction rate constants is presented with the emphasis on their uncertainties. Then the predictions of ignition, oxidation, flame burning velocities and flame structure of hydrogen - oxygen - inert mixtures were shown. Modeling range covers ignition experiments from 950 to 2700 K from subatmospheric pressures up to 5 atm; hydrogen oxidation in a flow reactor at temperatures around 900 K from 0.3 up to 15.7 atm; flame burning velocities in hydrogen - oxygen - inert mixtures from 0.35 up to 4 atm; hydrogen flame structure at 1 and 10 atm. Ignition delay times 1. Stoichiometric H2 - air mixtures P = 2 atm. T = 950 – 1200 K. 2. H2 - O2 - Ar mixtures. 8 % H2 - 2 % O2, P = 5 atm.; T = 950 – 1050 K. 1 % H2 - 2 % O2, P = 1 atm.; T = 1050 – 1800 K. 4 % H2 - 2 % O2, P = 1 atm.; T = 1200 – 2700 K. 1 % H2 - 3 % O2; P = 0.22 - 0.4 atm. T = 1400 – 2500 K. 1 % H2 - 1 % O2; P = 0.22 - 0.4 atm. T = 1400 – 2500 K. 3 % H2 - 1 % O2. P = 0.22 - 0.4 atm. T = 1400 – 2500 K. 6.7 % H2 - 3.3 % O2; P = 1.7 - 2.5; T = 1000 – 1430 K. 5 % H2 - 5 % O2 P = 1.7 - 2.5; T = 1000 – 1430 K. Flow reactor 0.5 % H2 - 0.5 % O2 - N2 P = 0.3 atm, Tin = 880 K. 0.842 % H2 - 1.52 % O2 - N2 P = 1 atm Tin = 910 K. 1.18 % H2 - 0.61 % O2 - N2; P = 15.7 atm Tin = 914 K. 1.18 % H2 - 2.21 % O2 - N2. P = 15.7 atm Tin = 914 K. Laminar flame speeds hydrogen - air P = 1, Tin = 298 K. lean to rich. hydrogen - oxygen - nitrogen O2/(O2+N2) = 0.2. Tin = 295 K, P = 750 Torr. lean to rich.


hydrogen - oxygen - argon O2/(O2+Ar) = 0.21. P = 1, Tin = 298 K. lean to rich. hydrogen - air flames, Tin = 298 K. lean to rich. P = 0.4 – 4 atm.

Fig. (from HERMANNS et al., submitted) Laminar burning velocities of H2-O2-N2 mixtures. The presented results are at O2/(O2 + N2) = 0.077 with different equivalence ratios. The measurements and modeling were performed with a gas-flow temperature of 298 K and ambient pressure. O: heat Flux measurements; ◘: measurements by Egolfopoulos and Law; line: calculations with the present mechanism. Laminar flame structure 18.83 % H2 - 4.6 % O2 - 76.57 % N2 flame P = 1, Tin = 336 K. 10 % H2 - 5 % O2 - 85 % Ar flame P = 10 atm Tin =363 K.


4.2 Carbon monoxide Related publications KONNOV, A.A., DYAKOV, I.V. Measurement of Adiabatic Burning Velocity in Flat Premixed Flames of CO + H2 + O2 + N2. 18th JOURNEES D'ETUDES of the Belgian Section of the Combustion Institute. May 2004, LLN. KONNOV, A.A., DYAKOV, I.V. Measurement of Adiabatic Burning Velocity in Flat Premixed Flames of CO + H2 + O2 + N2 to Validate Kinetic Mechanisms. 18th International Symposium on Gas Kinetics, Bristol, August 2004, Abstr. Symp. Pap., p. 173. Ignition delay times

0.36 0.40 0.44 0.481000/T

2

5

2

5

10

100

Tim

e, m

ks

Dean et al., 1978

Exp. t'

Exp. t''

model

model

Fig. Oxidation characteristic times of 0.05 % H2 - 1.0 % O2 - 12.17 % CO – Ar mixture. Points - experiment ( Dean et al., 1978 ), lines - calculation. Pressure = 1.4 - 2.2 atm; time is in microseconds.


Reference Dean A.M., Steiner D.C., Wang E.E. A shock tube study of the H2/O2/CO/Ar and H2/N2O/CO/Ar systems: Measurements of the rate constant for H + N2O = N2 + OH. Combust. Flame, 1978, v.32, pp.73-83 Comments 1. Time t' corresponds to the concentration of CO2 equal 1.0*10^16 cm^-3, and t" - 3.0*10^16 cm^-3.

2. Reduction of shock wave speed along shock tube was not accounted for in calculation of heated gas parameters that leads to the estimated uncertainty up to 25 K in temperature (see Ref.). Flow reactor

0.0 0.1 0.2 0.3 0.4 0.5Time, sec

0.000

0.002

0.004

0.006

0.008

0.010

CO

mol

e fra

ctio

n

1 atm

3.46 atm


Fig. CO mole fraction as a function of residence time at 1 and 3.46 atm. Points - experiment, lines - calculation. Mixture : 1 % CO - 0.5 % O2 - 0.65 % H2O - N2. Initial temperature = 1040 K. Reference Kim, T.J., Yetter, R.A. and Dryer, F.L. (1994) New results on moist CO oxidation: high pressure, high temperature experiments and comprehensive kinetic modelling. 25th Symposium (Int.) on Combustion , pp.759 - 766. Comments 1. Model prediction was NOT time shifted to match the point of 50 % fuel consumption as done usually for flow reactors.

2. CO oxidation was modeled as isobaric, adiabatic process. Calculated final adiabatic temperature is 1124 K, reported (see Ref.) experimental final temperature is 1110 K.

3. As was confirmed by the modeling with heat losses, the difference between experimental data and model prediction at high pressure is due to non-adiabaticity of the flow reactor. Laminar flame speeds (see related publications) Hydrogen (50%) + carbon monoxide (50%) + oxygen + nitrogen flames at P =1, Tin = 298 K. Oxygen contents D = O2/(O2 + N2) in the artificial air was 7%; 8%; 9 %. Lean to rich.


4.3 Formaldehyde, CH2O Ignition delay times

0.40 0.45 0.50 0.55 0.60 0.651000/T

10

100

1000

Tim

e, m

ks

Dean et al., 1980

exp mix C

Fig. Temporal characteristics of oxidation in the mixture 0.5 % CH2O – 0.92 % O2 – 9.15 % CO – Ar defined by CO2 formation. Time is in microseconds Reference A. M. Dean, R. L. Johnson and D. C. Steiner (1980) Shock-tube studies of formaldehyde oxidation. Combust. Flame, 37: 41-62 Comment In the experiments and in the modeling characteristic time was defined as the time to [CO2] = 5*1015 1/cm3.


Flow reactor

0.00 0.04 0.08 0.12 0.16Time, s

0.000

0.001

0.002

0.003

0.004

0.005M

ole

fract

ion

CH2O + O2

ch2o

co

h2

Fig. Species profiles at 994 K, equivalence ratio = 30.6, [CH2O] = 4600 ppm. Reference S. Hochgreb and F. L. Dryer (1992) A comprehensive study on CH2O oxidation kinetics. Combust. Flame 91: 257-284 Comment Experimental data for the oxidative pyrolysis of CH2O are from Fig. 2 c of the paper of Hochgreb and Dryer (1992).


4.4 Methanol, CH3OH Ignition delay times

0.45 0.50 0.55 0.60 0.651000/T, K

10

100

1000

Igni

tion

dela

y, m

ks

C.T.Bowman (1975)

2%CH3OH-4%O2-Ar

1%CH3OH-1%O2-Ar

modeling

2-4o2

1-1O2

Fig. Ignition delay times in methanol – oxygen – argon mixtures. Crosses and solid line: 2% CH3OH – 4% O2 –Ar at pressures close to 1 atm; diamonds and dashed line: 1% CH3OH – 1% O2 –Ar at pressures close to 2.7 atm. Time is in microseconds Reference C.T. Bowman (1975) A shock-tube investigation of the high-temperature oxidation of methanol. Combust. Flame 25:343-354.


0.9 1.0 1.1 1.21000/T

1E-1

1E+0

Igni

tion

dela

y, s

Fig. Ignition delay times in methanol – oxygen – argon mixtures at 1 atm. Crosses and solid line: 2% CH3OH – 3% O2 –Ar; diamonds and dashed line: 0.5% CH3OH – 0.75% O2 –Ar. Reference A.A. Borisov, V.M. Zamanskii, V.V. Lisyanskii, S.A. Rusakov (1992) High-temperature methanol oxidation. Sov. J. Chem. Phys. 9(8): 1836-1849. Comments Some results on ignition delay times for methanol (Borisov et al., 1992), ethanol, acetaldehyde and ethylene oxide mixtures (mentioned in the following) have been obtained in static by-pass apparatus. They were compared with the modeling at the initial stage of the current mechanism validation. As mentioned in the Section 3 of the present report, good agreement was found with experiments for CH3OH, however, agreement of the modeling with selected experiments for CH3HCO, C2H5OH, and C2H4O was found unsatisfactory at the time of the mid-term meeting. Analysis of the reasons for this disagreement took significant efforts and time. The paper from the lab of Prof. Borisov was found (Borisov et al., 1998), which explained important experimental uncertainties


associated with the static by-pass apparatus. In fact, assumption of the uniform temperature distribution after admission of the mixture into the pre-heated vessel is far from reality. It was shown experimentally that initial heating-up of the mixture takes about 0.2 sec, and even after that time the temperature of the mixture could be about 60 K lower that the temperature of the walls. Thus apparent ignition delays could not be attributed to the temperature of the walls; also simple “shift” of the temperatures to the lower T cannot be applied for comparison with the modeling. Regrettably, one can conclude that these experiments performed at around 1000 K and below cannot be used for the model validation using 0-dimensional modeling. Therefore significant disagreement observed in the Figure above does not indicate deficiencies of the mechanism at these lower temperatures. Reference A.A. Borisov, V.G. Knorre, E.L. Kudryashova, G.I. Skachkov, K.Y. Troshin (1998) On temperature measurements in the induction period of ignition of homogeneous gas mixtures in a static admittance apparatus CHEMICAL PHYSICS REPORTS 17 (7): 1323-1331


4.5 Methane, CH4 Related publications KONNOV, A.A., ZHU, J., BROMLY, J., and ZHANG, D.K. Non-Catalytic Methane Partial Oxidation over a Wide Temperature Range. Proceedings of the European Combustion Meeting - 2003 (CD, vol. 1) Paper # 9, 6 pp, October 25-28, 2003, Orleans, France KONNOV, A.A., ZHU, J.N., BROMLY, J.H., and ZHANG, D.K. Non-catalytic Partial Oxidation of Methane into Syngas over a Wide Temperature Range. Combust. Sci. Technol. 176 (7): 1093-1116 (2004) KONNOV, A.A., ZHU, J., BROMLY, J., and ZHANG, D.K. The Effect of NO and NO2 on the Partial Oxidation of Methane: Experiments and Modeling. Proceedings of the Combustion Institute, vol. 30 (1), pp. 1093-1100 (2005) KONNOV, A.A., DYAKOV, I.V. Measurement of burning velocity in adiabatic cellular methane-oxygen-carbon dioxide flames. Proceedings of the Third Mediterranean Combustion Symposium, Marrakech, Morocco, June 2003 pp. 1-10. KONNOV, A.A., DYAKOV, I.V. Measurement of Propagation Speeds in Adiabatic Cellular Premixed Flames of CH4 + O2 + CO2. Exp. Therm. Fluid Sci. 29 (8): 901-907 (2005) COPPENS, F., DE RUYCK, J. KONNOV, A.A., Effects of hydrogen enrichment on adiabatic burning velocity and nitric oxide formation in methane - air flames. Proceedings of the Fourth Mediterranean Combustion Symposium, Lisbon, October 6-10, 2005, CD, Paper # I.2, 12 pp. KONNOV, A.A., DYAKOV, I.V. Adiabatic Cellular Premixed Flames of Methane (Ethane, Propane) + Oxygen + Carbon Dioxide Mixtures. Proceedings of the 20th ICDERS (CD) Montreal, July 31 - August 5, 2005, 4 pp.

KONNOV, A.A. Modeling of nitric oxide formation in methane – oxygen – nitrogen (carbon dioxide) flames doped with ammonia. Book of abstracts of the 6th International Conference on Chemical Kinetics 25 - 29 July 2005, Gaithersburg, MD, p. 88. Ignition delay times


0.72 0.76 0.80 0.841000/T

100

1000

Igni

tion

dela

y, m

ks

3.8%CH4-19.2%O2-Ar

50 atm

Fig. Ignition delay times in CH4-O2-Ar mixture at 50 atm. Points: measurements from the database of the Stanford University (USA), line: present modelling. Time is in microseconds Flow reactor Non-catalytic partial oxidation of methane has been studied over a wide temperature range from 823 to 1531 K using two flow reactors. Highly diluted fuel rich CH4 – O2 – N2 mixtures were reacted in uncoated tubular flow reactors at 1.2 atm. Residence time was varied from 1 to 164 sec. Major and minor products of the partial oxidation were measured using a gas chromatograph. Kinetic modeling was performed to simulate experiments and key rate-controlling reactions were revealed by sensitivity analysis. It was found that chain-branching reaction H + O2 = OH + O, recombination CH3 + CH3 (+M) = C2H6 (+M), and methyl radical oxidation CH3 + O2 = CH2O + OH govern the overall rate of the process at short residence times. Recent measurements of these rate constants were analyzed and appropriate modifications in the detailed reaction mechanism were proposed. The model was adjusted to reproduce accurately the measurements at short residence times. At longer residence times, significant impact of the heterogeneous reactions leading to inhibition of the overall process was observed. The model developed in this study (Konnov et al. 2003, 2004b) correctly reproduced temporal profiles and final compositions of the products over the entire range of temperatures and the initial mixture compositions.


The chemistry of nitrogen-containing species was not a subject of the SAFEKINEX project, however these reactions were kept in the working mechanism to be able to model interaction of nitrogen oxides and hydrocarbons particularly at lower temperatures. It is well known that sensitization by NOx significantly reduces the temperature for onset of hydrocarbons' oxidation. Therefore modeling of such interaction extends the range of the mechanism validation down to lower temperatures by at least 100 - 200 K (Konnov et al., 2004). The reactions of nitrogen-containing species included in the working mechanism were published earlier (Konnov and De Ruyck, 2001c) and were not modified in the present study. CH4 – O2 – N2 mixtures, P = 1.2 atm, T = 823 – 1531 K, Residence time was varied from 1 to 164 sec. Table 1. CH4 – O2 – N2 mixtures studied experimentally. Contents are in vol. %.

Mixture O2 CH4 T, K Time, s Case 1 0.89 1.77 1100 0 - 164 Case 2 0.8 1.26 1100 0 - 164 Case 3 1.39 1.7 1100 0 - 164 Case 4 1.46 1.17 1100 0 - 164 Case 5 1.39 1.7 1123 - 1531 1.16 - 1.59 Case 6 1.01 2.11 1194 - 1529 1.02 - 1.3 Case 7 10.4 33.4 1015 - 1271 1.22 - 1.53 Case 8 1.39 1.7 1177 - 1525 21.3 - 27.6 Case 9 0.89 1.77 823 - 1073 56.1 - 73.1 Case 10 1.39 1.7 900 - 1100 90.4 - 110.5 Case 11 1.46 1.17 900 - 1100 90.4 - 110.5 Case 12 0.8 1.26 900 - 1100 90.4 - 110.5

Laminar flame speeds Methane + oxygen + carbon dioxide flames. The oxygen content O2/(O2 + CO2) in the artificial air was varied from 26 to 35 %. P = 1 atm, Tin = 298 K. lean to rich.


4.6 Ethane, C2H6 Related publications KONNOV, A.A., BARNES, F., BROMLY, J., ZHU, J., and ZHANG, D.K. The pseudo-catalytic promotion of nitric oxide oxidation by ethane at low temperatures. Combust. Flame 141 (3): 191-199 (2005) KONNOV, A.A., DYAKOV, I.V. Measurement of Propagation Speeds in Adiabatic Flat and Cellular Premixed Flames of C2H6 + O2 + CO2. Combustion and Flame, 136 (3): 371-376 (2004) KONNOV, A.A., DYAKOV, I.V. Adiabatic Cellular Premixed Flames of Methane (Ethane, Propane) + Oxygen + Carbon Dioxide Mixtures. Proceedings of the 20th ICDERS (CD) Montreal, July 31 - August 5, 2005, 4 pp. Ignition delay times

0.48 0.52 0.56 0.601000/T

80

100

120

140

[OH

] max

, ppm

100

1000

Tim

e to

1/2

max

, mks

C2H6-O2-Ar

[OH] max

Fig. Ignition delay times in C2H6 (300 ppm) -O2 (1052 ppm) -Ar mixture at pressures close to 1.2 atm. Points: measurements from the database of the Stanford University (USA), lines: present modelling. Crosses and dashed line: [OH] at maximum, diamonds and solid line: half-time to maximum; time is in microseconds.


Flow reactor C2H6 + O2 + N2 mixtures. P = 1.2 atm, T = 690 – 750 K. Residence times varied from 2.2 s at the highest temperature to 2.4 s at the lowest temperature. [O2] = 0 – 70 %, [C2H6] = 0 – 5000 ppm, balance is N2. Comment The chemistry of nitrogen-containing species was not a subject of the SAFEKINEX project, however these reactions were kept in the working mechanism to be able to model interaction of nitrogen oxides and hydrocarbons particularly at lower temperatures. It is well known that sensitization by NOx significantly reduces the temperature for onset of hydrocarbons' oxidation. Therefore modeling of such interaction extends the range of the mechanism validation down to lower temperatures by at least 100 - 200 K (Konnov et al., 2004). The reactions of nitrogen-containing species included in the working mechanism were published earlier (Konnov and De Ruyck, 2001c) and were not modified in the present study. Laminar flame speeds Ethane + oxygen + carbon dioxide flames. The oxygen content O2/(O2 + CO2) in the artificial air was varied from 26 to 35 %. P = 1 atm, Tin = 298 K. lean to rich.


4.7 Ethylene, C2H4 Ignition delay times

0.4 0.6 0.8 1.01000/T

1

10

100

1000

10000

Igni

tion

dela

y, m

ks

Brown, Tomas

c2h4+3O2+96 Ar

c2h4+3o2+12Ar

Fig. Ignition delay times in ethylene – oxygen –argon mixtures. Points: measurements (Brown and Thomas, 1999), lines: present modeling. Crosses and dashed line: 1%C2H4 – 3% O2 – 96% Ar at pressures 1.3 – 3 atm; diamonds and solid line: 6.25%C2H4 – 18.75% O2 – Ar. Time is in microseconds Comments 1. Experimentally ignition delay times have been defined by the onset of CH emission. Excited CH* radicals are not included in the present model. In the modeling ignition delays were defined as time to the peak of C2H radicals, because Devriendt and Peeters (1997) demonstrated that CH* could be formed in the reaction C2H + O = CH* + CO


2. Significant difference between modeling and experiment calls for detailed analysis of the C2H4 oxidation mechanism. References Brown C.J., Thomas G.O. (1999) Experimental studies of shock-induced ignition and transition to detonation in ethylene and propane mixtures. Combust. Flame, 117:861-870. Devriendt,K.; Peeters,J. (1997) Direct identification of the C2H(X2«SIGMA»+) + O(3P) = CH(A2«DELTA») + CO reaction as the source of the CH(A2«DELTA»=X2«PI») chemiluminescence in C2H2/O/H atomic flames. J. Phys. Chem. A: 101, 2546-2551


4.8 Acetylene, C2H2 Ignition delay times

0.50 0.60 0.70 0.80 0.90 1.001000/T

10

100

1000

Igni

tion

dela

y, m

ks

Nancy

1%C2H2-8%O2-Ar

3%C2H2-12%O2-Ar

Eiteneer, Frenklach, 2003

0.5%C2H2-5%O2-Ar

modeling

Fig. Ignition delay times in C2H2 – O2 - Ar mixtures. Crosses and diamonds: measured by Fournet et al. (1999) using OH emission, modeled as the time to [OH] maximum rise; solid circles (Eiteneer and Frenklach, 2003): measured and modeled as the time to [CO] maximum. Time is in microseconds Comment Experimental data published by Fournet et al. (1999) for self-ignition of C2H2, allene and propyne have been obtained at high pressures (8.5 – 10 atm) and at relatively low temperatures. Therefore they were chosen for the mechanism validation. At the time of the mid-term meeting the agreement between these experiments for C2H2 ignition and modeling was considered as satisfactory. Specifically, calculated ignition delay times were close to the experimental, however, experimental activation energy was much higher than predicted one.


Analysis of the available in the literature data on C2H2 self-ignition (Varatharajan and Williams, 2001) showed that effective activation energy observed by Fournet et al. (1999) is in fact much higher than all other measurements. One may argue that this exceptionally high activation energy could be explained by the changes in the oxidation kinetics due to high pressures. Indeed other experiments were performed at pressures below 4 atm, while those of Fournet et al. (1999) were in the range 8.5 – 10 atm. However, similar disagreement between results of Fournet et al. (1999) and results of Radhakrishnan and Burcat (1987) was observed for ignition of propyne (shown in the section below). In both studies pressures were close to 9 atm, but activation energies are significantly different. It was therefore decided not to use experimental data of Fournet et al. (1999) for C2H2 and C3H4 for the mechanism validation. The graphs with these measurements are kept in the present report to illustrate that calculated activation energies are much lower than experimental ones for these fuels. References Varatharajan B. and Williams F.A. (2001) Chemical-kinetic description of high-temperature ignition and detonation of acetylene-oxygen-diluent systems. Combust. Flame 125:624-645. Radhakrishnan K. and Burcat A. (1987) Kinetics of the ignition of fuels in artificial air mixtures. II: Oxidation of propyne. Combust. Sci. Technol., 54: 85-102. Eiteneer B., Frenklach, M. (2003) Experimental and modeling study of shock-tube oxidation of acetylene. Int. J. Chem. Kinet., 35: 391-414.


4.9 Acetaldehyde, CH3HCO Ignition delay times

0.9 1.0 1.1 1.2 1.3 1.4 1.51000/T, K

0.01

0.10

1.00

10.00

Igni

tion

dela

y, s

Legend Title

1%AA-2.5%O2-Ar

1%AA-10%O2-Ar

2%AA-20%O2-Ar

Fig. Ignition delay times in CH3CHO – O2 – Ar mixtures at 1 atm (Borisov et al., 1989). Solid line and crosses: 1% CH3HCO – 2.5% O2 – Ar; solid circles and dashed line: 2% CH3HCO – 20% O2 – Ar. In the experiments and modeling ignition time was defined as the time to rapid pressure rise. Comments In the section 5.4 (methanol) of the present report serious problems and experimental uncertainties associated with the static by-pass apparatus have been discussed. Similar disagreement of the modeling with measurements of Borisov et al. (1989) was found also for acetaldehyde ignition at low temperatures. Regrettably, one can conclude that these experiments performed at around 1000 K and below cannot be used for the model validation using 0-dimensional modeling. Therefore


significant disagreement observed in the Figure above does not indicate deficiencies of the mechanism at these lower temperatures.

0.55 0.60 0.65 0.70 0.75 0.801000/T

1E-4

1E-3

1E-2Ig

nitio

n de

lay,

s

Fig. Ignition delay times in CH3CHO – O2 – Ar mixtures at 3.5 atm (Dagaut et al., 1995). Solid line and crosses: 1% CH3HCO – 1.25% O2 – Ar; diamonds and dashed line: 0.5% CH3HCO – 2.5% O2 – Ar. In the experiments ignition time was defined as the time to CO2* emission, in the modeling as the time to [OH] max. References Borisov, A.A., Zamanskii, V.M., Konnov, A.A., Lissyamskii, V.V., Rusakov, S.A., and Skachkov, G.I. High-temperature ignition of mixtures of ethanol and acetaldehyde with oxygen. Sov.J.Chem.Phys. 4:2561-2575 (1989). Dagaut P., Reuillon, M., Cathonnet, M., McGuinnes, M., Simmie, J.M. (1995) Acetaldehyde oxidation in a JSR and ignition in shock waves: experimental and comprehensive kinetic modeling. Combust. Sci. Technol., 107: 301-316.


4.10 Ethanol, C2H5OH Ignition delay times

0.92 0.96 1.00 1.041000/T

0.01

0.10

1.00

10.00

Igni

tion

dela

y,s

Legend Title

0.5%EtOH-3%O2-He, 1 atm

1%EtOH-3%O2-He, 0.5 atm

0.5%EtOH-1.5%O2-He, 1 atm

1%EtOH-3%O2-He, 1 atm

Fig. Ignition delay times in C2H5OH – O2 – He mixtures at 1 atm (Borisov et al., 1989). Solid line and crosses: 0.5% C2H5OH – 3% O2 – He. In the experiments and modeling ignition time was defined as the time to rapid pressure rise. Comments In the section 5.4 (methanol) of the present report serious problems and experimental uncertainties associated with the static by-pass apparatus have been discussed. Similar disagreement of the modeling with measurements of Borisov et al. (1989) were found also for ethanol ignition at low temperatures. Regrettably, one can conclude that these experiments performed at around 1000 K and below cannot be used for the model validation using 0-dimensional modeling. Therefore



0.60 0.70 0.80 0.901000/T, K

10

100

1000

10000

Igni

tion

dela

y, m

ks

modeling

2 atm

4.6 atm

Fig. Ignition delay times in 0.625% C2H5OH – 7.5% O2 – Ar mixtures (Dunphy and Simmie 1991). Solid line and triangles: 2 atm; diamonds: 3.4 atm; circles and dashed line: 4.6 atm. In the experiments ignition time was defined as the time to CO2* emission, in the modeling as the time to [O] max. Time is in microseconds References Borisov, A.A., Zamanskii, V.M., Konnov, A.A., Lissyamskii, V.V., Rusakov, S.A., and Skachkov, G.I. High-temperature ignition of mixtures of ethanol and acetaldehyde with oxygen. Sov.J.Chem.Phys. 4:2561-2575 (1989). Dunphy, M.P., Simmie, J.M. (1991) High-temperature oxidation of ethanol. J.Chem.Soc. Faraday Trans. 87(11): 1691-1696.


4.11 Ethylene oxide, C2H4O Ignition delay times

1.12 1.17 1.22 1.27 1.321000/T

0.01

0.10

1.00

Igni

tion

dela

y, s

Legend Title

100 Etox, 0.3 atm

50% Etox-He, 0.3 atm

16%Etox-Ar, 0.5 atm

10% Etox-Ar, 1 atm

Fig. Ignition delay times in C2H4O – He (Ar) mixtures (Borisov et al., 1990). Solid line and crosses: pure C2H4O at 0.3 atm; solid circles and dashed line: 10% C2H4O – Ar at 1 atm. In the experiments and modeling ignition time was defined as the time to rapid pressure rise. Comments In the section 5.4 (methanol) of the present report serious problems and experimental uncertainties associated with the static by-pass apparatus have been discussed. Similar disagreement of the modeling with measurements of Borisov et al. (1990) were found also for ethylene oxide ignition at low temperatures. Regrettably, one can conclude that these experiments performed at around 1000 K and below cannot be used for the model validation using 0-dimensional modeling. Therefore



0.75 0.80 0.85 0.90 0.95 1.001000/T

10

100

1000Ig

nitio

n de

lay,

mks

Fig. Ignition delay times in C2H4O – O2 – Ar mixtures (Burcat, 1980). Solid line and upside triangles: 3.1%C2H4O – 6.9%O2 – Ar at 5 atm; crosses and dashed line: 9%C2H4O – 7%O2 – Ar at 5 atm. In the experiments and modeling ignition time was defined as the time to rapid pressure rise. Time is in microseconds References Borisov, A.A., Zamanskii, V.M., Konnov, A.A., Lissyamskii, V.V., and Skachkov, G.I. Pyrolysis and ignition of ethylene oxide. Sov.J.Chem.Phys. 6:2181-2195 (1990).

Burcat A. (1980) Kinetics of the ignition of fuels in artificial air mixtures. I. The oxidation of ethylene oxide. Combust. Sci. Technol., 21: 169-174.


4.12 Propane, C3H8 Relevant publications

KONNOV, A.A., DYAKOV, I.V. Adiabatic Cellular Premixed Flames of Methane (Ethane, Propane) + Oxygen + Carbon Dioxide Mixtures. Proceedings of the 20th ICDERS (CD) Montreal, July 31 - August 5, 2005, 4 pp. Ignition delay times

0.60 0.80 1.00 1.201000/T

1E-2

1E-1

1E+0

1E+1

1E+2

Igni

tion

dela

y, m

s

4%C3H8-20.2%O2-Ar

burcat 7 atm

cadman, 5atm

Fig. Ignition delay times in 4% C3H8 – 20.2% O2 – Ar mixtures. Solid line and crosses (Burcat et al. 1971): 7 atm; diamonds (Cadman et al. 2000) and dashed line: 5 atm. In the experiments ignition time was defined as the time to CH* emission, in the modeling as the time to [O] max. References Burcat A., Lifshitz, K., Scheller, K., Skinner, G.B. (1971) 13th Symp. (Int.) on Combustion, p. 745. Cadman, P., Thomas, G.O., Butler, P. (2000) The auto-ignition of propane at intermediate temperatures and high pressures. PCCP, 2: 5411-5419.


4.13 Propene, C3H6 Ignition delay times

590 630 670 710Temperature, K

0

400

800

1200

1600

Indu

ctio

n pe

riod,

s

Wilk, Cernansky

C3H6, fi=0.8

OH modeling

O modeling

0

10

20

30

Non

-isot

herm

al in

duct

ion

perio

d, s

Fig. Induction period of propene oxidation, equivalence ratio = 0.8. Points: experiment (Wilk et al., 1987). Solid and dashed lines: isothermal modeling (same scale as experiments) for maximums of [OH] and [O] respectively; dash-dot line: non-isothermal induction time (note different scale).


Flow reactor Reactivity experiments in the Princeton flow reactor (Zheng et al., 2003) have been modeled. Stoichiometric mixture of 0.33 % C3H6 – O2 – N2 at 12.5 atm had residence time of 1.8 sec. A turnover temperature (840 K) and slow oxidation from 500 to 800 K were reproduced.

500 600 700 800 900 1000T, K

0

1000

2000

3000

4000

C3H

6 m

ole

fract

ion,

ppm

Fig. Comparison of C3H6 profile of the reactivity experiments (Zheng et al. 2003) with the model prediction at 12.5 atm and stoichiometric conditions with residence time 1.8 sec. Line: modeling, symbols: experiment. Modeling has been performed for the stated in the text initial concentration of C3H6 = 0.33%. Comments Zheng et al. (2003) did not observe or predict NTC region within 500 – 860 K at 12.5 atm. They demonstrated that the model of Heyberger et al. (2001) was too slow at these conditions since it predicts a turnover temperature about 100 K higher than the experimental one.


0-dimentional non-isothermal calculations with the present mechanism lead to relatively short induction times (6 – 20 sec, see Fig. above). Isothermal modeling showed that peaks of OH and O have significantly different induction times, but in this case they are compatible to experimental observations. Apparently, correct modeling of the results of Wilk et al. (1987) requires taking into account radical sink on the surface and heat losses. Good agreement with the experiments of Zheng et al. (2003) is encouraging, yet further research of the C3H6 oxidation is required. References Wilk, R.D. Cernansky N.P., Cohen, R.S. (1987) An experimental study of propene oxidation at low and intermediate temperatures. Combust. Sci. Technol. 52: 39-58. Heyberger B., Battin-Leclerc, F., Warth, V., Fournet, R., Come, G. M., Scacchi, G., (2001) Combust. Flame, 126: 1780-1802. Zheng, L. Kazakov, A., Dryer, F.L. (2003) Experimental study of propene oxidation at low and intermediate temperatures. Proc. 3rd Joint Meeting of the US sections of the Combustion Institute.


4.14 Propyne, C3H4 Ignition delay times

0.6 0.7 0.8 0.91000/T

1

10

100

1000

10000Ig

nitio

n de

lay,

mks

Nancy

1%pC3H4-8%O2-Ar

Burcat

3%C3H4-12%O2-Ar, 9 atm

modeling

Fig. Ignition delay times in C3H4 (propyne) – O2 – Ar mixtures. Solid line and circles (Radhakrishnan and Burcat, 1987): 9 atm; crosses (Fournet et al., 1999) and dashed line: 9 atm. Time is in microseconds Comment In the section 5.8 (acetylene) of the present report experimental uncertainties in the apparent activation energy of ignition delays measured by Fournet et al. (1999) have been discussed. These are illustrated in the Fig. above. In both studies pressures were close to 9 atm, but activation energies are significantly different. It was therefore decided not to use experimental data of Fournet et al. (1999) for C2H2 and C3H4 for the mechanism validation. The graphs with these measurements are kept in the present report to illustrate that calculated activation energies are much lower than experimental ones for these fuels.


Significant difference between modeling and experiment calls for detailed analysis of the C3H4 oxidation mechanism. References Radhakrishnan K. and Burcat A. (1987) Kinetics of the ignition of fuels in artificial air mixtures. II: Oxidation of propyne. Combust. Sci. Technol., 54: 85-102. Fournet R., Baugé J.C., Battin-Leclerc F., Experimental and modelling study of oxidation of acetylene, propyne, allene and 1,3-butadiene, Int. J. Chem. Kinet., 31 :361-79 (1999).


4.15 Propylene oxide, C3H6O Decomposition in shock waves

900 1000 1100 1200Temperature, K

1E-2

1E-1

1E+0

1E+1

1E+2

Prod

uct d

istri

butio

n, %

1% PrOx internal st

co

ch4

c2h4

c3h6o

modeling

CO

ch4

c2h4

C3H6O

Fig. Major products during decomposition of C3H6O (Lifshitz and Tamburu, 1994). Reference Lifshitz, A., Tamburu, C. (1994) Isomerization and decomposition of propylene oxide. Studies with a single-pulse shock tube. J.Phys. Chem., 98: 1161 – 1170.


5. Concluding remarks According to the Project planning the validation of the C1-C3 mechanism was performed at temperatures higher than 550 K (up to 1600 K and higher) at pressures of 1 - 50 atm and for the mixtures having equivalence ratios from 0.5 to 2. The model was validated following its hierarchy starting from H2, CO, CH2O, CH3OH, CH4 and then C2H6, C2H4, C2H2, CH3HCO, C2H5OH, C2H4O (EtOx), C3H8, C3H6, C3H4, C3H6O (PrOx). At the time of the mid-term assessment reasonably good agreement was obtained for the following fuels: H2, CO, CH2O, CH3OH, CH4, C2H6, C3H8 (at high T), C3H6O. Satisfactory agreement was observed for: C2H4, C2H2, and C3H6. However, agreement of the modeling with selected experiments for CH3HCO, C2H5OH, C2H4O, C3H4, C3H8 (at lower T) was found unsatisfactory. After re-development of the C1-C3 mechanism reasonably good agreement was demonstrated for the following fuels: H2, CO, CH2O, CH4, C2H6, C2H2, CH3HCO, C2H5OH, C2H4O, C3H8, C3H6, C3H6O. Satisfactory agreement was observed for: CH3OH and C2H4. Further improvement of the propyne sub-mechanism is required. 6. References Battin-Leclerc, F., Bounaceur, R., Come, G. M., Fournet, R., Glaude, P. A., Scacchi, G.,

Warth, V., Exgas-alkanes. A software for the automatic generation of mechanisms for the oxidation of alkanes, 2004.

D. L. Baulch, C. T. Bowman, C. J. Cobos, R. A. Cox, Th. Just, J. A. Kerr, M. J. Pilling, D. Stocker, J. Troe, W. Tsang, R. W. Walker, and J. Warnatz Evaluated Kinetic Data for Combustion Modeling: Supplement II Journal of Physical and Chemical Reference Data -- September 2005 -- Volume 34, Issue 3, pp. 757-1397

Benson S.W., Thermochemicals kinetics, 2nd edition, John Wiley, New York (1976). Burcat, A. "Third Millennium Ideal Gas and Condensed Phase Thermochemical Database

for Combustion" Technion Aerospace Engineering (TAE) Report # 867 January 2001. or Alexander Burcat's Ideal Gas Thermochemical Database (2004) http://ftp.technion.ac.il/pub/supported/aetdd/thermodynamics

A. Evlampiev, L.M.T. Somers, L.P.H. de Goey, R.S.G. Baert. "TROT: A C++ interpreter for pre-processing and analysis of gas phase kinetics and thermodynamic properties." In proceedings of the conference on Numerical Combustion; Sedona, United States (2004)

Fournet R., Baugé J.C., Battin-Leclerc F., Experimental and modelling study of oxidation of acetylene, propyne, allene and 1,3-butadiene, Int. J. Chem. Kinet., 31 :361-79 (1999).

Fournet, R., Warth, V., Glaude, P.A., Battin-Leclerc, F., Scacchi, G., Come, G.M. Int.J. Chem. Kinet., 32: 36-51 (2000).

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