Development and Validation of a Reduced Reaction

08PFL-945

Development and Validation of a Reduced Reaction Mechanism for Biodiesel-Fueled Engine Simulations Jessica L. Brakora, Youngchul Ra and Rolf D. Reitz University of Wisconsin, Madison

Joanna McFarlane and Stuart Daw Oak Ridge National Laboratory Copyright © 2007 SAE International

ABSTRACT In the present study a skeletal chemical reaction mechanism for biodiesel surrogate fuel was developed and validated for multi-dimensional engine combustion simulations. The reduced mechanism was generated from an existing detailed methyl butanoate oxidation mechanism containing 264 species and 1219 reactions. The reduction process included flux analysis, ignition sensitivity analysis, and optimization of reaction rate constants under constant volume conditions. The current reduced mechanism consists of 41 species and 150 reactions and gives predictions in excellent agreement with those of the comprehensive mechanism. In order to validate the mechanism under biodiesel-fueled engine conditions, it was combined with another skeletal mechanism for n-heptane oxidation. This combined reaction mechanism, ERC-Bio, contains 53 species and 156 reactions, which can be used for diesel/biodiesel blend engine simulations. Biodiesel-fueled engine operation was successfully simulated using the ERC-Bio mechanism.

INTRODUCTION In recent years, increasingly stringent emissions standards and the high price of petroleum-based fuels have renewed an interest in fuels from alternative sources. Biodiesel, an oxygenated fuel composed of mono-alkyl esters [1], is seen as a promising alternative to conventional diesel for use in compression-ignition (CI) engines. In terms of emissions, biodiesel has been shown to reduce unburned hydrocarbons, carbon monoxide, and particulate matter compared to its petroleum counterpart. In addition, biodiesel contains no sulfur, and therefore produces no sulfur oxides or sulfates. As a plant-based fuel, it can be produced domestically, is a renewable energy source, and essentially has a closed carbon cycle over its lifetime [2]. Unfortunately, some disadvantages of biodiesel are limiting widespread use of the fuel. On a volumetric

basis, there is less energy per gallon of biodiesel compared to conventional diesel, which results in an estimated 11% decrease in fuel economy. Additionally, biodiesel’s higher cloud and pour points can cause flow problems in cold temperatures [3]. The most notable disadvantage is that biodiesel-fueled engines have been shown to increase nitrogen oxide (NOx) emissions. Several studies suggest increases of 10% or more for neat (100%) biodiesel [4]. The increase lessens if blends of biodiesel and diesel fuel are used, but in light of current and future regulations, any increase in emissions is undesirable. The NOx increase associated with the use of biodiesel is not completely understood and is the subject of many studies [4-7]. It is difficult to identify the main factor in the increase, because biodiesel and conventional diesel differ in both the chemical and physical properties. As an oxygenated fuel, biodiesel combustion produces intermediate species that are not found in conventional diesel combustion. These intermediates and their reactions may cause the increased in-cylinder temperatures or reaction pathways responsible for NOx production. In terms of physical properties, the kinematic viscosity and surface tension of biodiesel are significantly higher. These properties can greatly effect spray penetration, break-up, and atomization, and potentially create relatively fuel-rich areas and hence increased temperatures [8-9]. Multidimensional engine simulations have been used extensively to provide a better understanding of processes occurring inside the combustion chamber. Detailed kinetics models have been coupled with these simulations to improve predictions of the ignition and combustion processes [10]. Detailed kinetics models require accurate reaction mechanisms to represent the species, pathways, and reaction rates that describe the fuel chemistry. The objective of this work is to develop a practical reaction mechanism that will effectively predict biodiesel 1

combustion in a multi-dimensional diesel engine simulation. Methyl butanoate (MB) has been suggested as a surrogate for the large methyl esters found in biodiesel. A detailed kinetic mechanism for MB was developed by Lawrence Livermore National Laboratory (LLNL) [11].

from tests with initial pressures from 1-42 atm, temperatures from 550-1700 K, equivalence ratios from 0.3-1.5, and nitrogen-argon dilution from 70-99% were validated against experimental measurements from jetstirred reactors, plug flow reactors, rapid compression machines, and shock tubes.

For this study, the LLNL detailed mechanism was reduced and combined with a skeletal n-heptane mechanism. Ignition delay times of the reduced MB and combined MB/n-heptane mechanisms were validated against the detailed mechanism. For further validation the mechanism was applied to engine simulations and the results were compared to biodiesel experiments performed at the Sandia National Laboratories’ Combustion Research Facility in their SCORE engine.

Although comprehensive mechanisms are very useful, they are much too large to apply with CFD models for practical simulations. Several reduced n-heptane mechanisms have been developed that are more appropriate for modeling use.

MODEL FORMULATION KINETIC MECHANISMS A suitable model of ignition and combustion begins with a chemical kinetic mechanism. Mechanisms vary in size and complexity depending on the molecule of interest. Large molecules oxidize and decompose into hundreds of smaller species and can require thousands of reactions to describe the process. Alternately, smaller molecules generate less species and require significantly smaller mechanisms. The detail and accuracy of kinetic mechanisms vary as well. Comprehensive mechanisms contain the most complete reaction information available and, as a result, are generally very large and unsuitable for multidimensional engine simulations. Skeletal mechanisms, which only include significant elementary reactions, are much smaller in size; yet maintain the key features of comprehensive mechanisms. Surrogate Fuels Typical hydrocarbon fuels are not pure substances. Diesel and gasoline, for example, consist of many, high molecular weight components. In addition, the exact composition of these fuels varies based on the source, distributor, and intended region of use. To model these fuels, each component would require its own set of species and reactions and the resulting mechanism could be computationally prohibitive. In response to this issue, it is common practice to represent complex fuels with a single, relatively simple, surrogate species that exhibits similar combustion characteristics. Diesel fuel has been adequately represented by nheptane (n-C7H16) in many combustion models. Curran et al. [12] developed a detailed mechanism for nheptane oxidation that involved 550 species and 2450 reactions. Several modeling studies were used to determine the species and reactions responsible for both high and low temperature kinetics. Numerical results

Seiser et al. [13] created a reduced n-heptane mechanism using a sensitivity analysis based on ignition delay. Constant pressure, homogeneous reactor simulations were performed using the detailed mechanism under several conditions. Species and all reactions in which the species appeared were systematically removed and the ignition delay time was measured. If the ignition delay did not deviate from that of the detailed mechanism by more than 0.84%, that species and its corresponding reactions were removed from the mechanism. This process resulted in an intermediate mechanism of 282 species and 1282 reactions. The mechanism was reduced further by assessing the chemical pathways related to the fuel breakdown and oxidation. Species were neglected if they only appeared in pathways where the rate of fuel breakdown and oxidation were small. The final reduced mechanism had 160 species and 770 reactions. Golovitchev [14] created a skeletal n-heptane mechanism containing 40 species and 165 reactions. This method utilized sensitivity analysis and atom conservation. The resulting mechanism was validated against experimental shock tube data for 13.5 bar and 41 bar pressures. The Golovitchev skeletal mechanism was further reduced by Patel et al. [15]. In a similar method to that of Seiser, a sensitivity analysis was performed on species over a range of operating conditions. Species and reactions were removed based on ignition delay time comparisons. This method included application of a micro-genetic algorithm to optimize reaction rate constants in order to improve the agreement with more detailed mechanisms. The final reduced mechanism included 29 species and 52 reactions and was successfully applied to diesel engine simulations over a wide range of operating conditions. Unlike diesel, which consists of many components, biodiesel fuel is often assumed to be composed of just five methyl esters: methyl palmitate (C17H34O2), methyl stearate (C19H38O2), methyl oleate (C19H36O2), methyl linoleate (C19H34O2) and methyl linolenate (C19H32O2). It would seem relatively easy to create a representative biodiesel fuel from such a small number of components. Unfortunately, these long-chain methyl esters require large mechanisms to describe their oxidation, and the 2

combination of the mechanisms for each ester would be even larger.

The reduction process used in this study consisted of the following steps:

This dilemma illustrates the need for a biodiesel surrogate as well. Though biodiesel fuel has been available for many years, no widely accepted surrogate has been adopted. Recently, methyl butanoate (MB) has been proposed as a surrogate for the large methyl esters found in biodiesel. Researchers at the Lawrence Livermore National Laboratory (LLNL) developed a detailed kinetic reaction mechanism for MB that contained 264 species and 1219 reactions [11]. This mechanism was validated using a limited number of lowtemperature, sub-atmospheric experiments.

1. Perform constant volume SENKIN analysis for a range of initial pressures, initial temperatures, and equivalence ratios (φ). 2. Identify significant species based on their peak concentrations. Remove insignificant species and reactions from mechanism. 3. Identify significant reaction pathways based on reaction path fluxes. Remove insignificant species and reactions from mechanism. 4. Adjust reaction rate constants slightly in order to match the ignition time of the detailed mechanism 5. Combine the resulting reduced MB mechanism with the reduced n-heptane mechanism of Patel [15], allowing one to adjust the oxygen content of the fuel by blending MB with n-heptane, as shown in Table 1.

MB, a C5 species, is of manageable size and features the similar RC(=O)OCH3 chemical structure of biodiesel. Table 1 shows a comparison of MB with the average characteristics of the soy-based biodiesel typically used in the United States. Table 1: Comparison of soy-based biodiesel and methyl butanoate, a proposed surrogate for biodiesel fuel Methyl Butanoate

1 mole MB + 2 moles n-heptane R’C(=O)OCH3 + 2 C7H16

RC(=O)OCH3

R’C(=O)OCH3

C19H32O2

C5H10O2

C19H42O2

36-38

27

39

292

102

302

~11%

~30%

~11%

4000

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3500

Reduced MB mechanism

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MECHANISM REDUCTION METHODOLOGY

Temperature [K]

Chemical Structure Chemical Formula Lower H.V. (MJ/kg) Molec. Mass (kg/kmol) % Oxygen (by mass)

Soy-based Biodiesel

At each step, ignition delay for the reduced mechanism was calculated and compared to the LLNL mechanism over the range of initial conditions. Figure 1 illustrates the definition of ignition delay time for one set of initial conditions.

2500 2000 400K temperature rise

1500 1000 500

The purpose of this study was to identify a kinetic mechanism that will allow accurate simulations of biodiesel-fueled engine operation using multidimensional CFD codes. The detailed MB mechanism, hereafter referred to as the “LLNL mechanism”, was found to be much too large for practical CFD modeling. Therefore it was necessary to reduce the mechanism before applying it to engine simulations.

ignition delay time

ignition time

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Figure 1: Ignition delay time at an initial temperature of 900K, initial pressure of 40 bar, and equivalence ratio of 1.0.

SENKIN Analysis Due to limited available experiments related to MB, validation for the reduced mechanism was simply based upon comparisons with the LLNL mechanism. Though several automated reduction processes have been proposed, the process was not automated in the present study. Instead, it followed similar methods to those of Seiser [13] and Patel [15] with the goal of maintaining the same ignition delay timing as that of the LLNL mechanism. For this analysis, ignition was defined as the time at which the simulation experienced a temperature rise of 400K above the initial unburned gas temperature.

SENKIN is a FORTRAN program used to analyze homogeneous gas mixtures in closed systems [16]. Six systems are available for analysis: adiabatic constant pressure, adiabatic constant volume, adiabatic timedependant volume, constant pressure and temperature, constant volume and temperature, and time-dependant pressure and temperature. Once the problem is specified, SENKIN uses the same differential equations as those in the CHEMKIN-II solver [17] to provide species and temperature histories of the mixture based on the given mechanism. In addition SENKIN can evaluate sensitivity based on the reaction rates. 3

Initial conditions were varied to cover a range of pressures, temperatures, and equivalence ratios. In total, 90 conditions were evaluated in the SENKIN analysis. Table 2 summarizes these conditions. Table 2: Operating conditions for adiabatic, constant volume SENKIN analysis Condition Range Evaluated Initial Pressure [bar]

40, 60

Initial Temperature [K]

650-1350 (50 K increments)

Equivalence Ratio

0.4, 1.0, 1.5

Peak Concentration Analysis XSENKPLOT is an interactive graphics postprocessor that displays species and reaction information provided from SENKIN [18]. The program presents molar concentrations, steady-state analysis, reaction rates, reaction equilibrium, and temperature/time histories of the species as graphs that can be manipulated by the user. The initial analysis utilized the molar-concentrationsdisplay to identify thresholds below which species could be labeled insignificant. Four peak mole fraction thresholds were chosen (10-10, 10-9, 10-8 and 10-7). SENKIN constant volume results for φ=1.0 at 40 bar initial pressure were chosen for the concentration threshold analysis. Starting with the 10-10 concentration (Threshold 1), species that never exceeded the specified threshold were removed. Ignition delay was recalculated to ensure it was not significantly affected by the species removal. If ignition time did not vary from the detailed mechanism by more than 25% over the range of initial temperatures, the missing species were considered insignificant and remained out of the mechanism. The process was repeated for the three remaining threshold values. Figure 2 shows the results of removing species with each of the four thresholds. It can be seen that removal of all species with concentrations less than 10-10 resulted in a considerable change in ignition time at low temperatures (pink squares). However, by retaining species with the methyl ester structure, the ignition time was improved (Threshold 1*). Also, removal of species below Threshold 4 caused a delay in ignition. It was found the species CH2CHO had a strong affect on

ignition and it was replaced in the mechanism despite its low peak molar concentration (Threshold 4**). The peak concentration analysis thus eliminated 111 species from the LLNL mechanism without significantly changing the ignition time. LLNL mechanism (264 species) Threshold 1 (192 species) Threshold 1* (199 species) Threshold 2* (179 species) Threshold 3* (162 species) Threshold 4* (152 species) Threshold 4** (153 species)

1.E+00

1.E-01 Ignition Delay [s]

A constant volume adiabatic system was chosen for this study. Analysis began with a homogeneous mixture of air (20.95% O2 and 79.05% N2) and fuel (MB). The ratio of these components varied based on the desired equivalence ratio. Since EGR was not considered, no additional species were included in the initial mixture.

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* Species with the methyl ester structure included ** CH2CHO and methyl ester structure species included

Figure 2: Sensitivity of ignition due to species removal based on peak molar concentration.

Reaction Flux Analysis Reaction pathway analysis was used to further reduce the mechanism. By assessing the relative flux of each species, it was possible to identify the most significant pathways. Flux is defined as the integral of the reaction rate over time. XSENKPLOT offers another interactive feature that displays species and reaction pathways in a flowchart arrangement. This feature uses arrows of various widths to signify the importance of the flux of one species to the next. Users can view the reaction paths connecting each species in the mechanism and thus determine which pathways are important. The arrows connecting each species are separated into two sections: a base and a point. The width of the base section quantifies the destruction of the reactant species. The width of the point section quantifies the formation of the product species. The first step in the analysis involved the pathways related to the breakdown of MB. Figure 3 illustrates an example of six pathways displayed by XSENKPLOT. The species notation used in the MB mechanism is described in Appendix A. The base width of the arrows suggests that the flux of mb to the species mb2j is relatively high and this pathway is likely to be significant.

4

mb

mb2ooh

(ch3oco)

me2*o

me2j*o

Figure 3: XSENKPLOT’s reaction pathway display showing the breakdown of MB fuel.

(ch2co,ch3oco)

mb2oo

ch3o2h

(ch3o, ch2o, ch3o2)

mb2j

mb2o

mb2ooh4j

mp2d

c2h5cho

mb2ooh4oo

ch2cho

(c2h5)

mb4ooh2*o

ch2co

mp3j2*o

(ch2o)

(ch3oco, ch2co)

Figure 4 shows that when the mb2j species (and hence that pathway) was removed from the mechanism, ignition became significantly delayed. Removal of species mb2ooh and ch3o2h also caused big changes in ignition time. These three pathways were deemed to be important and were retained in the mechanism. However, mb3j, mb4j, and mbmj had relatively small effects and these species, along with their corresponding reactions, were removed from the mechanism. LLNL mechanism remove mb2j remove mb3j remove mb4j remove mbmj remove mb2ooh remove ch3o2h

1.E+00

Ignition Delay [s]

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Figure 5: Significant pathways included in the reduced MB mechanism. Lower-level species are in red. SENKIN tests were repeated over the range of initial conditions of Table 2 to ensure that the new mechanism did not display significant discrepancies with the other equivalence ratios or pressures. Reaction Rate Adjustment When species were removed from a mechanism, slight ignition delay changes were unavoidable. In order to improve the ignition time predictions, it was therefore necessary to adjust the reaction rate of certain reactions to compensate for species and pathways that were removed.

1.E-02

The reaction rates are described by the Arrhenius rate expression: k = A T b exp ( - E / R T)

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Figure 4: Sensitivity of ignition due to removal of pathways related to the breakdown of MB fuel

The reaction pathway analysis was repeated for the remaining pathways. The final mechanism, “ERC-mb”, contained just 41 species and 150 reactions. The significant pathways are shown in Figure 5.

where “A” is the pre-exponential factor, “b” is the temperature exponent, and “E” is the activation energy. Kinetic reaction mechanisms include these three rate parameters. A sensitivity analysis was performed on several important reactions, wherein the pre-exponential factor and activation energy were systematically changed to assess their effect on ignition times. Based on this study, two reactions were chosen for adjustments of the ignition timing. Table 3 shows the reactions, their initial Arrhenius parameters, and the adjusted parameters (in italics). Table 3: Adjusted Arrhenius rate constants for the ERCmb mechanism (in italics) Reaction A b E 4.000e+1 0.000 41300 3 mb+o2=ho2+mb2j 1.000e+1 0.000 41300 4 mb2oo=mb2ooh4j 6.097e+1 0.000 25076 5

0 2.622e+1 0.000 22067 0 Adjustments to these reactions significantly improved the predicted ignition times at low temperatures when compared to the LLNL mechanism. Figures 6 and 7 show the resulting ignition delay comparisons over the entire range of initial conditions tested. 1000

Figure 6: Ignition delay comparisons of the present reduced MB mechanism (ERC-mb) before and after rate constant adjustments for initial pressure of 40 bar and three equivalence ratios

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Only reactions for species that were unique to MB were included in the combined mechanism. The resulting mechanism, called “ERC-bio”, contains 53 species and 142 reactions. Initial SENKIN analysis for φ = 1.0 and an initial pressure of 40 bar revealed that the ignition delay curve drastically changed shape when the mechanisms were combined, as seen in Figure 8. This was found to be due to differences in the H2/O2 chemistry in the two mechanisms. Accordingly, thirteen HO2 and H2O2 reactions from the ERC-mb mechanism were also included in the combined mechanism and this removed some of the observed negative temperature coefficient dependence. The final mechanism included 53 species and 156 reactions.

LLNL mechanism

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Ignition Delay [ms]

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ERC-bio (+h2o2, ho2 rxns)

mb+ho2=h2o2+mb2 j

1.000e+1 4 4.000e+1 4 4.320e+1 2 5.616e+1 2

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The reduced MB mechanism was combined with the previously developed skeletal n-heptane mechanism to create different fuel blends, as described in Table 1. The n-heptane mechanism, “ERC n-heptane”, is an updated version of the reduced mechanism developed by Patel [15]. It contains 34 species and 77 reactions, including NOx related species and reactions taken from the GRI-Mech [19].

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Figure 7: Ignition delay comparison of the reduced MB mechanism (ERC-mb) before and after rate constant adjustments for initial pressure of 60 bar and three equivalence ratios Combination of Mechanisms

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Figure 8: Initial ignition delay calculation for the ERC-bio mechanism

The rate constants for two reactions in the ERC-bio mechanism required additional tuning from their ERCmb values. These two reactions and their adjusted parameters can be seen in Table 4. Figures 9 and 10 show the resulting ignition delay comparisons over the entire range of initial conditions tested. Table 4: Adjusted Arrhenius rate constants for the ERCbio mechanism (in italics) Reaction A b E

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Figure 9: Ignition delay comparison of the MB/nheptane combined mechanism (ERC-bio) and the detailed LLNL mechanism for initial pressure of 40 bar and three equivalence ratios 1000


Ignition Delay [ms]

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detailed LLNL mechanism for initial pressure of 60 bar and three equivalence ratios

It was concluded that the final reduced mechanism is adequate for the present CFD engine modeling purposes. The reaction steps and rates for the ERC-mb and ERC-bio mechanisms are given in Appendix B and C, respectively. Further details of both mechanisms are given by Brakora [20].

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ENGINE VALIDATION

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Once developed and validated against the detailed mechanism, it was of interest to test the applicability the ERC-bio mechanism for engine simulations. The combined mechanism was applied to diesel engine simulations using the KIVA3V-release 2 CFD code coupled with CHEMKIN-II [10, 15, 17, 21]. Numerical results were compared to biodiesel engine experiments performed at Sandia National Laboratories. Comparisons of combustion behavior and emissions were made.

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Cheng et al. [5] performed carefully controlled experiments in which neat (100%) biodiesel fuel was compared to several PRF blends. The start of combustion timing and premixed burn fractions were matched between the fuels in order to isolate the cause of the increased NOx typically seen in biodiesel combustion studies.

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EXPERIMENTS FOR VALIDATION

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Experimental Engine/Operating Conditions The experiments were performed on the Sandia compression-ignition optical research engine (SCORE), which is a modified version of the Caterpillar 3176 heavy-duty engine. The single-cylinder SCORE has a flat bottom piston bowl to provide optical access from underneath the combustion chamber. The piston rings are lower than on the production engine to prevent contact with the windows on the cylinder walls. The lowered piston rings result in an increased clearance volume and decreased compression ratio compared to the production engine. However, the temperature and pressure of the intake air were increased in the SCORE to match the motored top dead center conditions of the production engine. The engine specifications can be seen in Table 5. A hydraulically actuated, electronically-controlled unit injector (HEUI) was used for the fuel injection. The injection system specifications are shown in Table 6.

Figure 10: Ignition delay comparison of the MB/nheptane combined mechanism (ERC-bio) and the 8

Table 5: Specifications for the Sandia compressionignition optical research engine (SCORE) Engine type Single-cylinder CAT 3176 Cycle Four-stroke CIDI Bore x Stroke 125 mm x 140 mm IVO -32° ATDC IVC -153° ATDC EVO 116° ATDC EVC 11° ATDC Connecting rod length 225 mm Piston bowl diameter 90 mm Piston bowl depth 16.4 mm Swirl ratio 0.59 Displacement 1.72 L Compression ratio 11.3:1 (16.0:1 simulated)

Table 6: Fuel injection system specifications Injector type CAT HEUI A Injector model HIA-450 Nozzle style Single-guided VCO Number of orifices 6 Orifice diameter (nom.) 0.163 mm Hydro-erosion 13% Orifice L/D 8.0 Included spray angle 140° Oil rail pressure 20.8 MPa Max. fuel injection pressure 142 MPa Pressure intensification ratio 6.85:1 Valve opening pressure 31 MPa The engine was operated in a skip-fired mode, in which the fuel injector was only fired once every eight engine cycles. This was done to limit the amount of window cleaning needed and reduce the risk of window failure in the optical engine. Skip-firing also removed exhaust gas residual (EGR) from the combustion chamber. The engine was operated at low speed and higher load conditions in order to increase the potential for NOx. Start of Injection timing (SOI) was varied for each fuel in order to achieve a Start of Combustion (SOC) timing between TDC and 0.5 CAD aTDC. Operating conditions for the experiments are provided in Table 7.

Table 7: Experimental engine operating conditions Engine speed 800 rev/min Engine loads 10-16 bar gIMEP SOC TDC to 0.5° ATDC EGR None Coolant temperature 95°C Intake air temperature 116°C (69°C simulated) Intake air pressure 2.30 bar (1.43 bar sim.) Motored TDC temperature* 907 K Motored TDC pressure* 60.6 bar Motored TDC density* 23.3 kg/m3 Exhaust pressure 1.06 bar *Assuming polytropic compression with polytropic exponent of 1.349 from motored pressure data

Experimental Fuels The experimental study compared 100% soy-based biodiesel fuel (B100) to three primary reference fuel (PRF) blends, with the goal of matching the ignition delay and premixed-burn fraction of the reference fuel to that of the biodiesel. The PRF blends were mixtures of n-hexadecane and 2,2,4,4,6,8,8-hepthamethylnonane that could easily be adjusted to match ignition timing. It was found that the fuel mixture with a cetane number of 80 (CN80) most closely matched the biodiesel fuel. Table 8 shows a comparison of the B100 and CN80 fuels. Table 8: Comparison of soy-based biodiesel (B100) fuel and primary reference fuel with a cetane number of 80 (CN80) used in the experiments. Cetane Oxygen LHV Fuel Numbe Content (MJ/kg) r (mass %) B100

49.9

11.0

37.4

CN80

80.0

0.0

43.9

ENGINE SIMULATIONS For this study, the KIVA3V-release 2 CFD code [21] was coupled with the CHEMKIN-II chemistry solver [10, 15, 17]. This integrated code accounts for flow and fuel preparation effects in the engine, and provides a representation of the detailed fuel chemistry. KIVA provides species and thermodynamic information from each cell to CHEMKIN. CHEMKIN then returns new species and energy release information after solving the chemistry for each timestep [10, 15]. The KIVA/CHEMKIN simulations were performed for four of the experimental load cases: 10, 12, 14, 16 bar gross indicated mean effective pressure (gIMEP). Two 60-degree sector meshes were created based on the SCORE geometry, as shown in Figure 11. The coarse mesh with 5-mm cells was created to improve computation time for initial calibration tests. The fine mesh contained 2.5-mm cells.

Figure 11: The coarse and fine 60-degree sector meshes for the Sandia compression-ignition optical 9

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research engine (SCORE) shown at BDC. The piston crevice region is included in each mesh. A comparison of the coarse and fine mesh results showed that ignition delay time was consistent. However, the finer mesh more accurately predicted the structures within the combustion chamber. A comparison of the temperature distribution within the bowl as predicted by the coarse and fine mesh is shown in Figure 12.

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RESULTS Figures 13-16 show in-cylinder pressure and heat release rate (HRR) comparisons between the experimental and simulated results for each of the four experimental loads. As seen in the figures, ignition timing and peak pressure are adequately predicted, which suggests that the significant chemistry pathways are represented.

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0

HRR [J/CAD]

The engine simulations were run from intake valve closure (-153 atdc) to exhaust valve opening (116 atdc). Engine speed, fuel amount, and injection timing were kept at the experimental values. The initial pressure was taken from the experimental data at IVC, and the initial temperature was estimated using the TDC conditions and an ideal gas assumption. Since skipfiring was used in the experiment, the combustion chamber wall temperatures were assumed to be slightly greater than the coolant temperature. A fuel injection rate profile was not available from the experiment, and a simple top hat profile was assumed for the simulations. The actual duration of injection was unknown; hence the indicated duration was adjusted until the peak pressure matched the experimental data.

1600

60

20

P [bar]

As seen in Table 1, the oxygen content and molecular mass of biodiesel and MB differ. These characteristics affect ignition and energy content. In fact, the lower heating value of MB is about 27 MJ/kg [22], while biodiesel is typically 36-39 MJ/kg [23]. In order to address these issues, a mixture of 1 mole MB and 2 moles n-heptane was used to simulate biodiesel. The resulting mass-based oxygen content of the combined fuel was near 11% with an estimated LHV of 39 MJ/kg.

P [bar]

100

0 -40

-30

-20

-10


40

50

60


10

90


80

2000

70

1800

provided for Case 2. For example, the lift-off length measured at a time of 3.0 CAD was about 11 mm.

1600

60

1400

50

1200

40

1000

30

800 600

20

400

10

200

0

HRR [J/CAD]

P [bar]

100

0 -40

-30

-20

-10


40

50

60

Lift-off length predictions from engine simulations have been shown to strongly depend on mesh size [25]. Figure 18 illustrates the simulated mass fraction of OH for Case 2 along the plane of the spray at 3.0 CAD. As seen in Figure 18(a), the lift-off length is indistinguishable in the coarse mesh, while the fine mesh displays a slight lift-off length in Figure 18(b). The lift-off length predicted by the fine mesh was 4 mm, which is much shorter than the experimental results. Similarly small lift-off lengths were seen at all crank angles tested. These results suggest that a finer mesh size is required for accurate lift-off length predictions.


The HRR calculated by KIVA represents the chemical energy release and does not consider the wall heat transfer effects. This may account for some of the HRR differences observed in Figures 13-16. It is likely that additional tuning of the injection duration would improve the match between the pressure and HRR curves, and these profiles were considered adequate. NOx predictions for the four loads are shown in Figure 17. The simulation under predicts the NOx compared to the experiment, but maintains the trend of decreased NOx with increased load. The initial temperature and pressure could be increased to achieve a closer match of the NOx emissions. For example, an initial temperature increase of just 5K resulted in a simulated NOx increase of 2 g/kW-h for Case 1. A change in fuel injection rate had a similar effect. Considering this sensitivity, the agreement was regarded as acceptable. 20 Experiment

18

Simulation

16

NOx [g/KW-h]

14

(a)

(b)

Figure 17: Mass fraction of OH at 3.0 CAD as predicted for the (a) 5.0-mm and (b) 2.5-mm mesh. OH can be used as an indicator of flame stabilization and lift-off length.

It was found that mesh size is partially responsible for the jump in pressure and heat release seen at ignition. As seen in Figure 18, use of the finer mesh with 2.5-mm cells greatly reduces the HRR peak at ignition. Unfortunately this reduction in cell sizes more than doubles computation time. It can be assumed that a mesh with cells less than 2.5-mm would result in additional improvements.

12 Sandia experiment

1000

10

ERC-bio (5.0 mm mesh)

8 800

6

ERC-bio (2.5 mm mesh)

2 0 1

2

3

4

P [bar]

4 600

400

Case

Figure 17: Comparison of NOx emissions

Lift-off length, defined as the distance between the injector and the point at which the fuel jet stabilizes [24], was experimentally measured at several crank angles using OH chemiluminescence. Experimental data were

200

0 -1

0

1

2


7

8

9

10

Figure 18: HRR comparison using two mesh sizes for Case 2. 11

CONCLUSION To develop a model for biodiesel fuel, an existing 264 species, 1219 reaction detailed kinetic mechanism for methyl butanoate was reduced to 41 species and 150 reactions. Ignition delay timing of the skeletal mechanism was found to be in good agreement with the detailed mechanism in constant volume analyses over a wide range of initial conditions. The reduced methyl butanoate mechanism was then combined with a skeletal mechanism for n-heptane oxidation. The combined mechanism, which contained 55 species and 156 reactions, was also compared to the detailed mechanism and ignition delay timing was adequately predicted. The combined mb/n-heptane mechanism (called ERCbio) was applied to KIVA/CHEMKIN engine simulations and compared to biodiesel-fueled engine experiments. The mechanism successfully predicted ignition timing in the simulated engine over the four engine loads tested. The pressure and heat release rate calculations were similar to the experimental values, but additional improvements are needed. NOx emissions for the simulations followed the trends of the experiments, but the results were found to be sensitive to parameters such as the initial charge temperature at IVC and the injection rate shape. This preliminary study demonstrates the applicability of this reduced mechanism for engine simulations. However, factors other than the chemistry influence the performance of the biodiesel engine simulations. Identification of appropriate spray breakup constants for biodiesel fuel, and fuel injection rate, as well as application of a finer mesh will likely improve agreement between the simulation and the experiments. To reduce the mesh cell size without compromising computation time, it will be necessary to further reduce the ERC-bio mechanism. The authors believe additional reduction of the mechanism is possible. For example, assimilating two or more reactions into a single reaction will shorten pathways and eliminate several species. The present study represents a first step in validation of a reduced biodiesel fuel mechanism. In addition to the improvements mentioned previously, future studies will include simulation of different operating regimes (e.g., HCCI), and further investigation into emissions development within the combustion chamber. These studies will offer additional insights into the performance of the mechanism as a biodiesel surrogate.

ACKNOWLEDGMENTS The authors thank Chuck Mueller of the Sandia National Laboratories for providing experimental engine data, as

well as the DOE Sandia Labs and DOE LTC contract for funding support.

REFERENCES 1. ASTM D6751, Standard specification for biodiesel fuel (B100) blend stock for distillate fuels. 2. Fuel Fact Sheets, National Biodiesel Board, www.biodiesel.org 3. Radich, Anthony, “Biodiesel Performance, Costs, and Use”, Energy Information Administration, www.eia.doe.gov 4. United States Environmental Protection Agency, “A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions”, EPA420-P-02-001, October 2002. 5. Cheng, A.S., Upatnieks, A., Mueller, C. J., “Investigation of the Impact of Biodiesel Fueling on NOx Emissions Using an Optical DI Diesel Engine”. Intl J of Engine Research, Vol 7, No 4 (2006) pp 297-318. 6. Yuan, Wenqiao, Hansen, Alan C., Tan, Zhongchao, “Modeling of NOx Emissions of Biodiesel Fuels” ASAE Annual International Meeting, July 2005. 7. Lee, Change Sik, Park, Sung Wook, Kwon, Sang Il, “An Experimental Study on the Atomization and Combustion Characteristics of Biodiesel-Blended Fuels” Energy & Fuels 2005, 19, 2201-2208. 8. Ahmed, M.A., Ejim, C.E., Fleck, B.A., Amirfazili, A. “Effect of Biodiesel Fuel Properties and Its Blend on Atomization” SAE 2006-01-0893. 9. Tat, Mustafa Ertunc, Van Gerpen, John H., “Fuel Property Effects on Biodiesel” ASAE Annual International Meeting. July 2003. 10. Kong, S.C., Marriott, C.D., Reitz, R.D., Christensen, M. “Modeling and Experiments of HCCI Engine Combustion Using Detailed Chemical Kinetics with Multidimensional CFD” SAE 2001-01-1026. 11. Fisher, E.M., Pitz, W.J., Curran H.J., Westbrook, C.K.. “Detailed Chemical Kinetic Mechanisms for combustion of Oxygenated Fuels”. Proceedings of the Combustion Institute, Vol 28, 2000/pp.15791586. 12. Curran, H.J., Gaffuri, P., Pitz, W.J. and Westbrook, C.K. "A Comprehensive Modeling Study of nHeptane Oxidation" Combustion and Flame 114:149-177 (1998). 13. Seiser, H., Pitsch, H., Seshadri, K., Pitz, W.J., and Curran, H.J., "Extinction and Autoignition of nHeptane in Counterflow Configuration," Proceedings of the Combustion Institute 28, p. 2029-2037, 2000. 14. Golovitchev, V.I, “Mechanisms (combustion chemistry)” www.tfd.chalmers.se/~valeri/MECH.html, Chalmers University of Technology, Gothenburg, Sweden, 2000. 15. Patel, A. Kong, S. C., Reitz, R. D., “Development and Validation of a Reduced Reaction Mechanism 12

16.

17.

18.

19. 20.

21.

22.

23.

24.

25.

for HCCI Engine Simulations”, SAE 2004-01-0558, 2004. Lutz, A.E., Kee, R.J., Miller, J.A., “SENKIN: A FORTRAN Program for Predicting Homogeneous Gas Phase Chemical Kinetics with Sensitivity Analysis”, Sandia Report SAND 87-8248, UC-4, 1988. Kee, R.J., Rupley, F.M., Miller, J.A., “CHEMKIN-II: A FORTRAN Chemical Kinetics Package for the Analysis of Gas Phase Chemical Kinetics” Sandia Report SAND 89-8009, 1989. “NIST XSenkplot: An Interactive Postprocessor for Numerical Simulations of Chemical Kinetics” www.cstl.nist.gov/div836/xsenkplot/ GRI-Mech 3.0. www.me.berkeley.edu/gri-mech/ Brakora, J.L., “Development and Validation of a Reduced Reaction Mechanism for Biodiesel-fueled Engine Simulations.” MS Thesis, University of Wisconsin-Madison, 2007. Amsden, A.A., KIVA-3V, Release 2: Improvements to KIVA-3V. Los Alaos National Laboratory Report LA-UR-99-915, October 1996. Daubert, T.E., Danner, R.D., Physical and Thermodynamic Properties of Pure Chemicals: Data Compilation. Taylor and Francis. 1992. U.S. DOE, Office of Energy Efficiency and Renewable Energy, Alternative Fuels Data Center. www.eere.energy.gov/afdc/altfuel/whatis_biodiesel.h tml Pickett, Lyle M, Siebers, Dennis L., Idicheria, Chertan A., “Relationship Between Ignition Processes and the Lift-off Length of Diesel Fuel Jets.” SAE 2005-01-3843. Vishwanathan, Gokul, Reitz, Rolf D., “Numerical Predictions of Diesel Flame Lift-off Length and Soot Distribution Under Low Temperature Combustion.” Submitted to SAE, 2007.

CONTACT Jessica L. Brakora, [email protected]

13

APPENDIX A Fisher E.M., Pitz W.J., Curran H.J., Westbrook, C.K., "Detailed Chemical Kinetic Mechanisms for Combustion of Oxygenated Fuels", Proceedings of the Combustion Institute, Volume 28, p. 1579-1586, 2000; Lawrence Livermore National Laboratory, Livermore, CA, UCRL-JC-137097. UCRL-WEB-204236, Review and release date: May 19, 2004. 6/16/2000 Elizabeth M. Fisher The following are some notes explaining the choice of species names in the methyl butanoate and methyl formate mechanisms: mb=methyl butanoate mp=methyl propanoate me=methyl ethanoate mm=methyl methanoate (=methyl formate) ba= butanoic acid Carbons are numbered starting with 1 = carbonyl carbon. m denotes the carbon in the methoxy group Groups attached to a given carbon atom are listed after the number or letter labelling that carbon atom. j denotes a radical site *o denotes an oxygen atom attached via a double bond. For example, mb3j4ooh is methyl butanoate with a hydroxyl group attached to the terminal carbon (number 4) and a hydrogen atom missing from the carbon next to the terminal one (number 3) d denotes a double bond connecting carbon n and carbon n+1. For example, mb2d has a double bond between carbon 2 and carbon 3. An example of a cyclic species is:, mbcy4o2, which resembles mb but has an O bonded between carbons 4 and 2. Note that in many cases a more conventional notation is used. For example, ch3oco is used instead of mm1j. This is mainly for consistency with other reaction mechanisms.

14

APPENDIX B ERC-mb MECHANISM (Arrhenius rate constants in bold were adjusted to match ignition delay) SPECIES CONSIDERED 1. mb

8. mb4ooh2*o

15. h2

22. hco

29. ch3o

36. ch2cho

2. mb2j

9. me2*o

16. o

23. co2

30. c2h4

37. c3h6

3. mb2o

10. me2j*o

17. o2

24. ch3

31. c2h5

38. c2h5cho

4. mb2oo

11. mp2d

18. oh

25. ch4

32. ch2

39. ch3o2

5. mb2ooh

12. mp3j2*o

19. h2o

26. ho2

33. c2h2

40. ch3o2h

6. mb2ooh4j

13. ch3oco

20. n2

27. h2o2

34. c2h3

41. c2h3co

7. mb2ooh4oo

14. h

21. co

REACTIONS CONSIDERED 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47.

48. 49. 50. 51. 52.

mb2j+h=mb mb+c2h3=c2h4+mb2j mb+ch3=ch4+mb2j mb+ch3o2=ch3o2h+mb2j mb+h=h2+mb2j mb+ho2=h2o2+mb2j mb+o=oh+mb2j mb+o2=ho2+mb2j mb+oh=h2o+mb2j mb+mb2oo=mb2ooh+mb2j mp2d+ch3=mb2j co+ch3o=ch3oco co2+ch3=ch3oco mp2d+ch3=>c2h3co+ch2o+ch4 mp2d+h=>c2h3co+ch2o+h2 mp2d+o=>c2h3co+ch2o+oh mp2d+oh=>c2h3co+ch2o+h2o mp2d+ho2=>c2h3co+ch2o+h2o2 mp2d+o=ch3oco+ch2cho c2h3+ch3oco=mp2d hco+ch3oco=me2*o mb2j+o2=mb2oo mb2oo+mb2j=mb2o+mb2o mb2oo+ch3=ch3o+mb2o ch3o2+mb2j=ch3o+mb2o ho2+mb2j=oh+mb2o mb2oo=mb2ooh4j mb2oo+ho2=mb2ooh+o2 mb2oo+h2o2=>mb2ooh+ho2 mb2ooh+ho2=>mb2oo+h2o2 mb2oo+ch3o2=>mb2o+ch3o+o2 mb2oo+mb2oo=>o2+mb2o+mb2o mb2ooh=mb2o+oh me2*o+c2h5=mb2o c2h5cho+ch3oco=mb2o mb2ooh4j=>me2*o+c2h4+oh mb2ooh4j+o2=mb2ooh4oo mb2ooh4oo=mb4ooh2*o+oh mb4ooh2*o=>ch2o+mp3j2*o+oh me2*o+h=me2j*o+h2 me2*o+oh=me2j*o+h2o me2*o+o=me2j*o+oh me2*o+ch3=me2j*o+ch4 me2*o+ho2=me2j*o+h2o2 ch3oco+co=me2j*o ch2co+ch3oco=mp3j2*o ch3+h(+m)=ch4(+m) Low pressure limit: 0.33100E+31 -0.40000E+01 TROE centering: 0.00000E+00 0.10000E-14 h2 Enhanced by 2.000E+00 h2o Enhanced by 5.000E+00 co Enhanced by 2.000E+00 co2 Enhanced by 3.000E+00 ch4+h=ch3+h2 Reverse Arrhenius coefficients: ch4+oh=ch3+h2o Reverse Arrhenius coefficients: ch4+o=ch3+oh Reverse Arrhenius coefficients: hco+oh=co+h2o Reverse Arrhenius coefficients: co+oh=co2+h

28. ch2o 35. ch2co (k = A T**b exp(-E/RT)) A b E 1.00E+14 0.0 0.0 4.00E+11 0.0 14300.0 2.00E+11 0.0 7900.0 4.00E+12 0.0 14000.0 2.52E+14 0.0 7300.0 4.32E+12 0.0 14400.0 2.20E+13 0.0 3280.0 1.00E+14 0.0 41300.0 1.15E+11 0.5 63.0 2.16E+12 0.0 14400.0 1.00E+11 0.0 7600.0 1.50E+11 0.0 3000.0 1.50E+11 0.0 36730.0 4.52E-01 3.6 7154.0 9.40E+04 2.8 6280.0 9.65E+04 2.7 3716.0 5.25E+09 1.0 1590.0 8.40E+12 0.0 20440.0 5.01E+07 1.8 76.0 1.00E+13 0.0 0.0 1.00E+13 0.0 0.0 1.41E+13 0.0 0.0 7.00E+12 0.0 -1000.0 7.00E+12 0.0 -1000.0 7.00E+12 0.0 -1000.0 7.00E+12 0.0 -1000.0 2.62E+10 0.0 22066.9 1.75E+10 0.0 -3275.0 2.40E+12 0.0 10000.0 2.40E+12 0.0 10000.0 1.40E+16 -1.6 1860.0 1.40E+16 -1.6 1860.0 5.95E+15 0.0 42540.0 1.50E+11 0.0 11900.0 1.50E+11 0.0 11900.0 5.92E+19 -1.9 30290.0 4.52E+12 0.0 0.0 9.98E+10 0.0 20351.0 1.50E+16 0.0 42000.0 4.00E+13 0.0 4200.0 2.69E+10 0.8 -340.0 5.00E+12 0.0 1790.0 1.70E+12 0.0 8440.0 2.80E+12 0.0 13600.0 1.50E+11 0.0 3000.0 1.00E+11 0.0 9200.0 2.14E+15 -0.4 0.0 0.21080E+04 0.10000E-14 0.40000E+02

1.73E+04 6.61E+02 1.93E+05 4.82E+02 2.13E+06 3.56E+04 1.02E+14 2.90E+15 1.40E+05

3.0 3.0 2.4 2.9 2.2 2.2 0.0 0.0 1.9

8224.0 7744.0 2106.0 14860.0 6480.0 3920.0 0.0 105200.0 -1347.0 15

Reverse Arrhenius coefficients: 53. h+o2=o+oh Reverse Arrhenius coefficients: 54. o+h2=h+oh Reverse Arrhenius coefficients: 55. o+h2o=oh+oh Reverse Arrhenius coefficients: 56. oh+h2=h+h2o Reverse Arrhenius coefficients: 57. hco+m=h+co+m Reverse Arrhenius coefficients: h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 58. h2o2+oh=h2o+ho2 Reverse Arrhenius coefficients: Declared duplicate reaction... 59. c2h4+o=ch3+hco Reverse Arrhenius coefficients: 60. h+c2h4(+m)=c2h5(+m) Low pressure limit: 0.11120E+35 -0.50000E+01 TROE centering: 0.10000E+01 0.10000E-14 h2 Enhanced by 2.000E+00 h2o Enhanced by 5.000E+00 co Enhanced by 2.000E+00 co2 Enhanced by 3.000E+00 61. c2h5+o2=c2h4+ho2 Reverse Arrhenius coefficients: 62. ch3+ho2=ch3o+oh Reverse Arrhenius coefficients: 63. co+ho2=co2+oh Reverse Arrhenius coefficients: 64. h2o+m=h+oh+m Reverse Arrhenius coefficients: h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 65. h+o2(+m)=ho2(+m) Low pressure limit: 0.35000E+17 -0.41000E+00 TROE centering: 0.50000E+00 0.10000E-29 h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 66. co+o(+m)=co2(+m) Low pressure limit: 0.13500E+25 -0.27880E+01 h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 67. co+o2=co2+o Reverse Arrhenius coefficients: 68. hco+h=co+h2 Reverse Arrhenius coefficients: 69. hco+o=co+oh Reverse Arrhenius coefficients: 70. ch2o+m=hco+h+m Reverse Arrhenius coefficients: 71. ch2o+oh=hco+h2o Reverse Arrhenius coefficients: 72. ch2o+h=hco+h2 Reverse Arrhenius coefficients: 73. ch2o+o=hco+oh Reverse Arrhenius coefficients: 74. ch3+oh=ch2o+h2 Reverse Arrhenius coefficients: 75. ch3+o=ch2o+h Reverse Arrhenius coefficients: 76. ch3+o2=ch3o+o Reverse Arrhenius coefficients: 77. ch2o+ch3=hco+ch4 Reverse Arrhenius coefficients: 78. hco+ch3=ch4+co Reverse Arrhenius coefficients: 79. ch3o(+m)=ch2o+h(+m) Low pressure limit: 0.23440E+26 -0.27000E+01 80. c2h4(+m)=c2h2+h2(+m) Low pressure limit: 0.15000E+16 0.00000E+00 81. ho2+o=oh+o2 Reverse Arrhenius coefficients:

1.57E+07 1.97E+14 1.56E+13 5.08E+04 2.23E+04 2.97E+06 3.01E+05 2.16E+08 9.35E+08 1.86E+17 6.47E+13

1.9 0.0 0.0 2.7 2.7 2.0 2.0 1.5 1.5 -1.0 0.0

20990.0 16540.0 425.0 6292.0 4197.0 13400.0 -3850.0 3430.0 18580.0 17000.0 -442.0

1.00E+12 1.68E+11

0.0 0.3

0.0 31460.0

1.02E+07 1.9 179.0 2.85E+08 1.1 31770.0 1.08E+12 0.5 1822.0 0.44480E+04 0.95000E+02 0.20000E+03

1.22E+30 1.26E+30 1.10E+13 4.78E+14 3.01E+13 6.44E+15 1.84E+27 2.25E+22

-5.8 -5.6 0.0 -0.3 0.0 -0.3 -3.0 -2.0

10100.0 22310.0 0.0 24550.0 23000.0 84610.0 122600.0 0.0

1.48E+12 0.6 0.0 -0.11160E+04 0.10000E+31 0.10000+101

1.80E+10 0.0 0.41910E+04

2384.0

1.07E-15 7.1 9.44E-15 7.1 7.34E+13 0.0 4.81E+14 0.0 3.02E+13 0.0 8.70E+13 0.0 6.28E+29 -3.6 2.66E+24 -2.6 3.43E+09 1.2 1.19E+09 1.2 9.33E+08 1.5 7.45E+07 1.5 4.16E+11 0.6 1.46E+10 0.6 2.25E+13 0.0 6.76E+14 0.0 8.00E+13 0.0 1.06E+15 0.0 2.00E+18 -1.6 3.58E+18 -1.6 3.64E-06 5.4 7.58E-06 5.4 1.21E+14 0.0 2.07E+16 0.0 5.45E+13 0.0 0.30600E+05 1.80E+13 0.0 0.55443E+05 3.25E+13 0.0 7.86E+14 -0.3

13320.0 19540.0 0.0 90000.0 0.0 87900.0 93200.0 427.0 -447.0 29380.0 2976.0 17650.0 2762.0 15340.0 4300.0 76030.0 0.0 69630.0 29210.0 -1631.0 998.0 16150.0 0.0 90480.0 13500.0 76000.0 0.0 55390.0 16

82. hco+ho2=ch2o+o2 Reverse Arrhenius coefficients: 83. ch3o+o2=ch2o+ho2 Reverse Arrhenius coefficients: 84. ch3+ho2=ch4+o2 Reverse Arrhenius coefficients: 85. hco+o2=co+ho2 Reverse Arrhenius coefficients: 86. ho2+h=oh+oh Reverse Arrhenius coefficients: 87. ho2+h=h2+o2 Reverse Arrhenius coefficients: 88. ho2+oh=h2o+o2 Reverse Arrhenius coefficients: 89. h2o2+o2=ho2+ho2 Reverse Arrhenius coefficients: Declared duplicate reaction... 90. oh+oh(+m)=h2o2(+m) Low pressure limit: 0.30410E+31 -0.46300E+01 TROE centering: 0.47000E+00 0.10000E+03 h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 91. h2o2+h=h2o+oh Reverse Arrhenius coefficients: 92. ch4+ho2=ch3+h2o2 Reverse Arrhenius coefficients: 93. ch2o+ho2=hco+h2o2 Reverse Arrhenius coefficients: 94. oh+m=o+h+m Reverse Arrhenius coefficients: h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 95. o2+m=o+o+m Reverse Arrhenius coefficients: h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 96. h2+m=h+h+m Reverse Arrhenius coefficients: h2 Enhanced by 2.500E+00 h2o Enhanced by 1.200E+01 co Enhanced by 1.900E+00 co2 Enhanced by 3.800E+00 97. c2h3+h(+m)=c2h4(+m) Low pressure limit: 0.98000E+30 -0.38600E+01 TROE centering: 0.78200E+00 0.20800E+03 98. c2h5+c2h3=c2h4+c2h4 Reverse Arrhenius coefficients: 99. c2h2+h(+m)=c2h3(+m) Low pressure limit: 0.22540E+41 -0.72690E+01 TROE centering: 0.10000E+01 0.10000E-14 h2 Enhanced by 2.000E+00 h2o Enhanced by 5.000E+00 co Enhanced by 2.000E+00 co2 Enhanced by 3.000E+00 100. c2h4+h=c2h3+h2 Reverse Arrhenius coefficients: 101. c2h4+oh=c2h3+h2o Reverse Arrhenius coefficients: 102. c2h3+o2=c2h2+ho2 Reverse Arrhenius coefficients: Declared duplicate reaction... 103. ch2+o2=co+h2o Reverse Arrhenius coefficients: 104. c2h2+o=ch2+co Reverse Arrhenius coefficients: 105. ch2+o2=hco+oh Reverse Arrhenius coefficients: 106. ch2+o=co+h+h Reverse Arrhenius coefficients: 107. ch2+o2=co2+h+h Reverse Arrhenius coefficients: 108. c2h3+o2=c2h2+ho2 Reverse Arrhenius coefficients: Declared duplicate reaction... 109. h2o2+o=oh+ho2 Reverse Arrhenius coefficients:

2.97E+10 2.05E+13 5.50E+10 1.32E+09 3.60E+12 5.18E+15 7.58E+12 9.03E+11 7.08E+13 1.35E+14 1.66E+13 9.14E+14 2.89E+13 6.89E+15 5.94E+17 4.20E+14

0.3 0.0 0.0 0.3 0.0 -0.3 0.0 0.3 0.0 -0.3 0.0 -0.3 0.0 -0.3 -0.7 0.0

-3861.0 38950.0 2424.0 31390.0 0.0 57960.0 410.0 32930.0 300.0 39570.0 820.0 58300.0 -500.0 72140.0 53150.0 11980.0

1.24E+14 -0.4 0.0 0.20490E+04 0.20000E+04 0.10000E+16

2.41E+13 7.75E+12 3.42E+11 3.36E+11 5.82E-03 1.19E-02 3.91E+22 4.72E+18

0.0 0.0 0.0 -0.3 4.5 4.2 -2.0 -1.0

3970.0 74710.0 19290.0 2502.0 6557.0 4921.0 105300.0 0.0

6.47E+20 6.17E+15

-1.5 -0.5

121500.0 0.0

4.57E+19 2.42E+15

-1.4 -0.4

104400.0 -3040.0

6.10E+12 0.3 280.0 0.33200E+04 0.26630E+04 0.60950E+04 3.00E+12 0.0 0.0 4.82E+14 0.0 71530.0 3.11E+11 0.6 2589.0 0.65770E+04 0.67500E+03 0.10000E+16

8.42E-03 5.72E-01 2.02E+13 1.02E+13 5.19E-15 2.73E-16

4.6 3.8 0.0 0.0 -1.3 -0.9

2583.0 3233.0 5955.0 20220.0 3310.0 11400.0

7.28E+19 8.51E+20 6.12E+06 1.15E+06 1.29E+20 5.31E+19 5.00E+13 0.00E+00 3.29E+21 0.00E+00 2.12E-06 1.11E-07

-2.5 -2.5 2.0 2.0 -3.3 -3.3 0.0 0.0 -3.3 0.0 6.0 6.3

1809.0 179800.0 1900.0 52570.0 284.0 73170.0 0.0 0.0 2868.0 0.0 9484.0 17570.0

9.55E+06 2.54E+07

2.0 1.7

3970.0 19850.0 17

110. c2h2+oh=ch2co+h Reverse Arrhenius coefficients: 111. ch2co+h=ch3+co Reverse Arrhenius coefficients: 112. ch2co+o=ch2+co2 Reverse Arrhenius coefficients: 113. ch2+o2=ch2o+o Reverse Arrhenius coefficients: 114. ch2co(+m)=ch2+co(+m) Low pressure limit: 0.36000E+16 0.00000E+00 115. ch2+o2=co2+h2 Reverse Arrhenius coefficients: 116. ch3+c2h3=ch4+c2h2 Reverse Arrhenius coefficients: 117. ch3+c2h5=ch4+c2h4 Reverse Arrhenius coefficients: 118. c2h3+h=c2h2+h2 Reverse Arrhenius coefficients: 119. c2h5+h=ch3+ch3 Reverse Arrhenius coefficients: 120. c2h3+o2=ch2o+hco Reverse Arrhenius coefficients: 121. c2h4+ch3=c2h3+ch4 Reverse Arrhenius coefficients: 122. c3h6=c2h3+ch3 Reverse Arrhenius coefficients: 123. c3h6+o=ch2co+ch3+h Reverse Arrhenius coefficients: 124. c3h6+o=c2h5+hco Reverse Arrhenius coefficients: 125. c2h4+o2=c2h3+ho2 Reverse Arrhenius coefficients: 126. ch2o+m=co+h2+m Reverse Arrhenius coefficients: 127. c3h6+h=c2h4+ch3 Reverse Arrhenius coefficients: 128. c2h5cho=c2h5+hco Reverse Arrhenius coefficients: 129. h2o2+h=h2+ho2 Reverse Arrhenius coefficients: 130. hco+o=co2+h Reverse Arrhenius coefficients: 131. ch3+m=ch2+h+m Reverse Arrhenius coefficients: 132. ch3+h=ch2+h2 Reverse Arrhenius coefficients: 133. ch3+oh=ch2+h2o Reverse Arrhenius coefficients: 134. c2h4+o=ch2cho+h Reverse Arrhenius coefficients: 135. h2o2+o2=ho2+ho2 Reverse Arrhenius coefficients: Declared duplicate reaction... 136. c2h3+o2=ch2cho+o Reverse Arrhenius coefficients: 137. ch3o2+m=ch3+o2+m Reverse Arrhenius coefficients: 138. ch3o2h=ch3o+oh Reverse Arrhenius coefficients: 139. ch3o2+ch2o=ch3o2h+hco Reverse Arrhenius coefficients: 140. c2h4+ch3o2=c2h3+ch3o2h Reverse Arrhenius coefficients: 141. ch4+ch3o2=ch3+ch3o2h Reverse Arrhenius coefficients: 142. ch3o2+ch3=ch3o+ch3o Reverse Arrhenius coefficients: 143. ch3o2+ho2=ch3o2h+o2 Reverse Arrhenius coefficients: 144. h2o2+oh=h2o+ho2 Reverse Arrhenius coefficients: Declared duplicate reaction... 145. ch3o2+ch3o2=o2+ch3o+ch3o Reverse Arrhenius coefficients: 146. c2h3co=c2h3+co Reverse Arrhenius coefficients: 147. ch2cho=ch2co+h Reverse Arrhenius coefficients: 148. ch2cho+o2=ch2o+co+oh Reverse Arrhenius coefficients: 149. ch3+o2=ch2o+oh Reverse Arrhenius coefficients:

2.19E-04 4.5 2.16E-03 4.5 1.10E+13 0.0 2.40E+12 0.0 1.75E+12 0.0 3.74E+12 0.0 3.29E+21 -3.3 3.86E+22 -3.3 3.00E+14 0.0 0.59270E+05 1.01E+21 -3.3 3.05E+23 -3.3 3.92E+11 0.0 2.96E+13 0.0 1.95E+13 -0.5 2.90E+16 -0.7 2.00E+13 0.0 1.33E+13 0.0 3.61E+13 0.0 5.45E+16 -1.0 1.70E+29 -5.3 1.66E+29 -5.3 6.62E+00 3.7 1.44E+00 4.0 2.73E+62 -13.3 4.71E+59 -13.2 2.50E+07 1.8 1.00E+00 0.0 1.58E+07 1.8 1.40E+05 1.9 4.00E+13 0.0 4.94E+13 -0.5 1.83E+32 -4.4 5.07E+27 -3.4 4.83E+33 -5.8 2.31E+33 -5.9 9.85E+18 -0.7 1.81E+13 0.0 4.82E+13 0.0 1.88E+12 0.3 3.00E+13 0.0 9.68E+15 0.0 1.97E+16 0.0 2.11E+11 1.0 9.00E+13 0.0 1.82E+13 0.0 3.00E+06 2.0 2.62E+06 2.0 3.39E+06 1.9 9.48E+06 1.8 1.84E+14 -0.7 1.30E+11 0.0

-1000.0 19670.0 3400.0 40200.0 1350.0 53690.0 2868.0 63180.0 70980.0 1508.0 186700.0 0.0 66050.0 0.0 70170.0 2500.0 68080.0 0.0 16980.0 6500.0 93050.0 9500.0 5472.0 123200.0 29540.0 76.0 0.0 -1216.0 26510.0 58200.0 1368.0 87120.0 84350.0 18500.0 31620.0 81710.0 0.0 7950.0 24260.0 0.0 110200.0 92520.0 -19620.0 15100.0 10400.0 2500.0 12960.0 179.0 16050.0 39550.0 -1629.0

3.50E+14 2.59E+12 4.34E+27 5.44E+25 6.31E+14 1.17E+11 1.99E+12 8.50E+12 1.13E+13 3.00E+12 1.81E+11 3.71E+11 7.00E+12 2.97E+16 1.75E+10 5.16E+13 5.80E+14 9.77E+13

-0.6 0.1 -3.4 -3.3 0.0 0.6 0.0 -0.5 0.0 0.0 0.0 -0.5 0.0 -0.9 0.0 -0.8 0.0 0.3

5260.0 6459.0 30470.0 0.0 42300.0 -1771.0 11670.0 7009.0 30430.0 11500.0 18480.0 -1327.0 -1000.0 28310.0 -3275.0 34880.0 9560.0 41020.0

1.40E+16 0.00E+00 2.04E+14 1.51E+11 3.09E+15 5.00E+13 2.00E+13 0.00E+00 7.47E+11 7.78E+11

-1.6 0.0 -0.4 0.0 -0.3 0.0 0.0 0.0 0.0 0.0

1860.0 0.0 31450.0 4810.0 50820.0 12300.0 4200.0 0.0 14250.0 67770.0 18

150. c2h4+h2=ch3+ch3 Reverse Arrhenius coefficients: NOTE: E units cal/mole, A units mole-cm-sec-K

3.77E+12 1.00E+14

0.8 0.0

84710.0 32000.0

19

APPENDIX C ERC-bio MECHANISM (Arrhenius rate constants in bold were adjusted to match ignition delay) SPECIES CONSIDERED 1. mb 9. h2o2

17. ch3

25. mb2o

33. mp2d

41. c2h3co

49. c5h11co

2. o2

10. ho2

18. ch4

26. mb2oo

34. mp3j2*o

42. nc7h16

50. n

3. n2

11. h

19. c2h2

27. mb2ooh

35. ch3oco

43. c3h4

51. n2o

4. co2

12. o

20. c2h3

28. mb2ooh4j

36. ch2co

44. c3h5

52. no

5. h2o

13. ch3o

21. c2h4

29. mb2ooh4oo

37. ch2cho

45. c3h7

53. no2

6. co

14. ch2o

22. c2h5

30. mb4ooh2*o

38. c2h5cho

46. c7h15-2

7. h2

15. hco

23. c3h6

31. me2*o

39. ch3o2

47. c7h15o2

8. oh

16. ch2

24. mb2j

32. me2j*o

40. ch3o2h

48. c7ket12

REACTIONS CONSIDERED 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50.

mb2j+h=mb mb+c2h3=c2h4+mb2j mb+ch3=ch4+mb2j mb+ch3o2=ch3o2h+mb2j mb+h=h2+mb2j mb+ho2=h2o2+mb2j mb+o=oh+mb2j mb+o2=ho2+mb2j mb+oh=h2o+mb2j mb+mb2oo=mb2ooh+mb2j mp2d+ch3=mb2j mb2j+o2=mb2oo mb2oo+mb2j=mb2o+mb2o mb2oo+ch3=ch3o+mb2o ch3o2+mb2j=ch3o+mb2o ho2+mb2j=oh+mb2o mb2oo=mb2ooh4j mb2oo+ho2=mb2ooh+o2 mb2oo+h2o2=>mb2ooh+ho2 mb2ooh+ho2=>mb2oo+h2o2 mb2oo+ch3o2=>mb2o+ch3o+o2 mb2oo+mb2oo=>o2+mb2o+mb2o mb2ooh=mb2o+oh me2*o+c2h5=mb2o c2h5cho+ch3oco=mb2o mb2ooh4j=>me2*o+c2h4+oh mb2ooh4j+o2=mb2ooh4oo mb2ooh4oo=mb4ooh2*o+oh mb4ooh2*o=>ch2o+mp3j2*o+oh co+ch3o=ch3oco co2+ch3=ch3oco hco+ch3oco=me2*o me2*o+h=me2j*o+h2 me2*o+oh=me2j*o+h2o me2*o+o=me2j*o+oh me2*o+ch3=me2j*o+ch4 me2*o+ho2=me2j*o+h2o2 ch3oco+co=me2j*o mp2d+ch3=>c2h3co+ch2o+ch4 mp2d+h=>c2h3co+ch2o+h2 mp2d+o=>c2h3co+ch2o+oh mp2d+oh=>c2h3co+ch2o+h2o mp2d+ho2=>c2h3co+ch2o+h2o2 mp2d+o=ch3oco+ch2cho c2h3+ch3oco=mp2d ch2co+ch3oco=mp3j2*o c2h2+oh=ch2co+h ch2co+h=ch3+co ch2co+o=ch2+co2 ch2co(+m)=ch2+co(+m) Low pressure limit: 0.36000E+16 51. c3h6+o=ch2co+ch3+h 52. ch2cho=ch2co+h 53. c2h4+o=ch2cho+h

A

b

1.00E+14 0.0 4.00E+11 0.0 2.00E+11 0.0 4.00E+12 0.0 2.52E+14 0.0 5.62E+12 0.0 2.20E+13 0.0 4.00E+14 0.0 1.15E+11 0.5 2.16E+12 0.0 1.00E+11 0.0 1.41E+13 0.0 7.00E+12 0.0 7.00E+12 0.0 7.00E+12 0.0 7.00E+12 0.0 2.62E+10 0.0 1.75E+10 0.0 2.40E+12 0.0 2.40E+12 0.0 1.40E+16 -1.6 1.40E+16 -1.6 5.95E+15 0.0 1.50E+11 0.0 1.50E+11 0.0 5.92E+19 -1.9 4.52E+12 0.0 9.98E+10 0.0 1.50E+16 0.0 1.50E+11 0.0 1.50E+11 0.0 1.00E+13 0.0 4.00E+13 0.0 2.69E+10 0.8 5.00E+12 0.0 1.70E+12 0.0 2.80E+12 0.0 1.50E+11 0.0 4.52E-01 3.6 9.40E+04 2.8 9.65E+04 2.7 5.25E+09 1.0 8.40E+12 0.0 5.01E+07 1.8 1.00E+13 0.0 1.00E+11 0.0 2.19E-04 4.5 1.10E+13 0.0 1.75E+12 0.0 3.00E+14 0.0 0.00000E+00 0.59270E+05 2.50E+07 1.8 3.09E+15 -0.3 3.39E+06 1.9

E 0.0 14300.0 7900.0 14000.0 7300.0 14400.0 3280.0 41300.0 63.0 14400.0 7600.0 0.0 -1000.0 -1000.0 -1000.0 -1000.0 22066.9 -3275.0 10000.0 10000.0 1860.0 1860.0 42540.0 11900.0 11900.0 30290.0 0.0 20351.0 42000.0 3000.0 36730.0 0.0 4200.0 -340.0 1790.0 8440.0 13600.0 3000.0 7154.0 6280.0 3716.0 1590.0 20440.0 76.0 0.0 9200.0 -1000.0 3400.0 1350.0 70980.0 76.0 50820.0 179.0 20

54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95.

96.

97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119.

c2h3+o2=ch2cho+o ch2cho+o2=ch2o+co+oh c2h5cho=c2h5+hco ch3o2+m=ch3+o2+m ch3o2h=ch3o+oh ch3o2+ch2o=ch3o2h+hco c2h4+ch3o2=c2h3+ch3o2h ch4+ch3o2=ch3+ch3o2h ch3o2+ch3=ch3o+ch3o ch3o2+ho2=ch3o2h+o2 ch3o2+ch3o2=o2+ch3o+ch3o c2h3co=c2h3+co nc7h16+h=c7h15-2+h2 nc7h16+oh=c7h15-2+h2o nc7h16+ho2=c7h15-2+h2o2 nc7h16+o2=c7h15-2+ho2 c7h15-2+o2=c7h15o2 c7h15o2+o2=c7ket12+oh c7ket12=c5h11co+ch2o+oh c5h11co=c2h4+c3h7+co c7h15-2=c2h5+c2h4+c3h6 c3h7=c2h4+ch3 c3h7=c3h6+h c3h6+ch3=c3h5+ch4 c3h5+o2=c3h4+ho2 c3h4+oh=c2h3+ch2o c3h4+oh=c2h4+hco ch3+ho2=ch3o+oh ch3+oh=ch2+h2o ch2+oh=ch2o+h ch2+o2=hco+oh ch2+o2=co2+h2 ch2+o2=co+h2o ch2+o2=ch2o+o ch2+o2=co2+h+h ch2+o2=co+oh+h ch3o+co=ch3+co2 co+oh=co2+h o+oh=o2+h h+ho2=oh+oh oh+oh=o+h2o h+o2+m=ho2+m h2o Enhanced co2 Enhanced h2 Enhanced co Enhanced h2o2+m=oh+oh+m h2o Enhanced co2 Enhanced h2 Enhanced co Enhanced h2+oh=h2o+h ho2+ho2=h2o2+o2 ch2o+oh=hco+h2o ch2o+ho2=hco+h2o2 hco+o2=ho2+co hco+m=h+co+m ch3+ch3o=ch4+ch2o c2h4+oh=ch2o+ch3 c2h4+oh=c2h3+h2o c2h3+o2=ch2o+hco c2h3+hco=c2h4+co c2h5+o2=c2h4+ho2 ch4+o2=ch3+ho2 oh+ho2=h2o+o2 ch3+o2=ch2o+oh ch4+h=ch3+h2 ch4+oh=ch3+h2o ch4+o=ch3+oh ch4+ho2=ch3+h2o2 ch4+ch2=ch3+ch3 c3h6=c2h3+ch3 ch2+ch2=c2h2+h2 ch2+ch2=c2h2+h+h

by by by by

2.100E+01 5.000E+00 3.300E+00 2.000E+00

by by by by

2.100E+01 5.000E+00 3.300E+00 2.000E+00

3.50E+14 2.00E+13 9.85E+18 4.34E+27 6.31E+14 1.99E+12 1.13E+13 1.81E+11 7.00E+12 1.75E+10 1.40E+16 2.04E+14 4.38E+07 9.70E+09 1.65E+13 2.00E+15 4.68E+11 4.50E+14 6.67E+14 9.84E+15 7.05E+14 9.60E+13 1.25E+14 9.00E+12 6.00E+11 1.00E+12 1.00E+12 5.00E+13 7.50E+06 2.50E+13 4.30E+10 6.90E+11 2.00E+10 5.00E+13 1.60E+12 8.60E+10 1.57E+14 3.51E+07 4.00E+14 1.70E+14 6.00E+08 3.60E+17

-0.6 0.0 -0.7 -3.4 0.0 0.0 0.0 0.0 0.0 0.0 -1.6 -0.4 2.0 1.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3 -0.5 0.0 1.3 -0.7

5260.0 4200.0 81710.0 30470.0 42300.0 11670.0 30430.0 18480.0 -1000.0 -3275.0 1860.0 31450.0 4760.0 1690.0 16950.0 47380.0 0.0 18232.7 41100.0 40200.0 34600.0 30950.0 36900.0 8480.0 10000.0 0.0 0.0 0.0 5000.0 0.0 -500.0 500.0 -1000.0 9000.0 1000.0 -500.0 11800.0 -758.0 0.0 875.0 0.0 0.0

1.00E+16

0.0

45500.0

1.17E+09 3.00E+12 5.56E+10 3.00E+12 3.30E+13 1.59E+18 4.30E+14 6.00E+13 8.02E+13 4.00E+12 6.03E+13 2.00E+10 7.90E+13 7.50E+12 3.80E+11 6.60E+08 1.60E+06 1.02E+09 9.00E+11 4.00E+12 3.15E+15 1.20E+13 1.20E+14

1.3 0.0 1.1 0.0 -0.4 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.6 2.1 1.5 0.0 0.0 0.0 0.0 0.0

3626.0 0.0 -76.5 8000.0 0.0 56712.3 0.0 960.0 5955.0 -250.0 0.0 -2200.0 56000.0 0.0 9000.0 10840.0 2460.0 8604.0 18700.0 -570.0 85500.0 800.0 800.0 21

120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150. 151. 152.

153. 154.

155. 156.

c2h4+m=c2h2+h2+m 1.50E+15 0.0 c2h2+o2=hco+hco 4.00E+12 0.0 c2h2+o=ch2+co 1.02E+07 2.0 c2h2+h+m=c2h3+m 5.54E+12 0.0 c2h3+h=c2h2+h2 4.00E+13 0.0 c2h3+oh=c2h2+h2o 3.00E+13 0.0 c2h3+ch2=c2h2+ch3 3.00E+13 0.0 c2h3+c2h3=c2h2+c2h4 1.45E+13 0.0 c2h3+o=c2h2+oh 1.00E+13 0.0 c2h2+oh=ch3+co 4.83E-04 4.0 c2h3=c2h2+h 4.60E+40 -8.8 h2o2+oh=h2o+ho2 1.00E+12 0.0 Declared duplicate reaction... oh+oh(+m)=h2o2(+m) 1.24E+14 -0.4 Low pressure limit: 0.30410E+31 -0.46300E+01 0.20490E+04 h2o2+h=h2o+oh 2.41E+13 0.0 h2o2+o=oh+ho2 9.55E+06 2.0 h2o2+h=h2+ho2 4.82E+13 0.0 h2o2+oh=h2o+ho2 5.80E+14 0.0 Declared duplicate reaction... co+ho2=co2+oh 3.01E+13 0.0 ho2+o=oh+o2 3.25E+13 0.0 hco+ho2=ch2o+o2 2.97E+10 0.3 ch3o+o2=ch2o+ho2 5.50E+10 0.0 ho2+h=h2+o2 1.66E+13 0.0 c2h3+o2=c2h2+ho2 5.19E-15 -1.3 Declared duplicate reaction... c2h3+o2=c2h2+ho2 2.12E-06 6.0 Declared duplicate reaction... c2h4+o2=c2h3+ho2 4.00E+13 0.0 n+non2+o 3.50E+13 0.0 n+o2no+o 2.65E+12 0.0 n+ohno+h 7.33E+13 0.0 n2o+on2+o2 1.40E+12 0.0 n2o+o2no 2.90E+13 0.0 n2o+hn2+oh 4.40E+14 0.0 n2o+ohn2+ho2 2.00E+12 0.0 n2o(+m)n2+o(+m) 1.30E+11 0.0 Low pressure limit: 0.62000E+15 0.00000E+00 0.56100E+05 h2 Enhanced by 2.000E+00 h2o Enhanced by 6.000E+00 ch4 Enhanced by 2.000E+00 co Enhanced by 1.500E+00 co2 Enhanced by 2.000E+00 ho2+nono2+oh 2.11E+12 0.0 no+o+mno2+m 1.87E+15 0.0 h2 Enhanced by 2.000E+00 h2o Enhanced by 6.000E+00 ch4 Enhanced by 2.000E+00 co Enhanced by 1.500E+00 co2 Enhanced by 2.000E+00 no2+ono+o2 3.90E+12 0.0 no2+hno+oh 1.32E+14 0.0

NOTE:

55800.0 28000.0 1900.0 2410.0 0.0 0.0 0.0 0.0 0.0 -2000.0 46200.0 0.0 0.0 3970.0 3970.0 7950.0 9560.0 23000.0 0.0 -3861.0 2424.0 820.0 3310.0 9484.0 58200.0 330.0 6400.0 1120.0 10810.0 23150.0 18880.0 21060.0 59620.0

-480.0 0.0

-240.0 360.0

A units mole-cm-sec-K, E units cal/mole

22