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Detailed and Reduced Mechanisms of Jet a Combustion at High Temperatures a
a
a
b
M. I. Strelkova , I. A. Kirillov , B. V. Potapkin , A. A. Safonov , b
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L. P. Sukhanov , S. Ya. Umanskiy , M. A. Deminsky , A. J. Dean c
, B. Varatharajan & A. M. Tentner
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d
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RRC Kurchatov Institute, Moscow, Russia
b
Kintech Lab, Moscow, Russia
c
GE Global Research, Niskayuna, New York, USA
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Argonne National Laboratories, Argonne, Illinois, USA Published online: 02 Oct 2008.
To cite this article: M. I. Strelkova , I. A. Kirillov , B. V. Potapkin , A. A. Safonov , L. P. Sukhanov , S. Ya. Umanskiy , M. A. Deminsky , A. J. Dean , B. Varatharajan & A. M. Tentner (2008) Detailed and Reduced Mechanisms of Jet a Combustion at High Temperatures, Combustion Science and Technology, 180:10-11, 1788-1802, DOI: 10.1080/00102200802258379 To link to this article: http://dx.doi.org/10.1080/00102200802258379
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Combust. Sci. and Tech., 180: 1788–1802, 2008 Copyright # Taylor & Francis Group, LLC ISSN: 0010-2202 print/1563-521X online DOI: 10.1080/00102200802258379
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DETAILED AND REDUCED MECHANISMS OF JET A COMBUSTION AT HIGH TEMPERATURES M. I. Strelkova1, I. A. Kirillov1, B. V. Potapkin1, A. A. Safonov2, L. P. Sukhanov2, S. Ya. Umanskiy2, M. A. Deminsky2, A. J. Dean3, B. Varatharajan3, and A. M. Tentner4 1
RRC Kurchatov Institute, Moscow, Russia Kintech Lab, Moscow, Russia 3 GE Global Research, Niskayuna, New York, USA 4 Argonne National Laboratories, Argonne, Illinois, USA 2
For the Computational Fluid Dynamics (CFD) modeling of combustion and detonation of Jet A aviation fuel it is necessary to use the simplest kinetic mechanism that accurately describes the essential relevant phenomena. A surrogate that demonstrated good agreement with the parent fuel in the detonation process was chosen. A detailed kinetic mechanism was elaborated using a multilevel approach. A reduced mechanism was derived from the detailed mechanism for use in the CFD simulation of real detonation processes in combustors. Keywords: Combustion; Detailed and reduced kinetic mechanisms; Detonation; Jet A kerosene; Modeling; Surrogate
INTRODUCTION American civil aviation kerosene (Jet A) is multi-component fuel consisting of several hundreds of hydrocarbons, including alkanes, cycloalkanes, aromatic and polycyclic compounds. In Figure 1, Jet A fuel compositions for two phases (liquid and vapor) are presented (Shepherd et al., 2000). In the liquid phase it consists of hydrocarbons up to C16, while in gaseous phase it consists of hydrocarbons up to C10. A detailed, sufficiently accurate modeling of combustion processes of such fuel in propulsion systems such as ramjets, scramjets, pulse detonation and gas turbine engines requires huge computational resources and can be prohibitive even on the most advanced computing platforms available today. Hence, a simpler fuel model with well defined and reproducible composition (surrogate), which exhibits an ignition behavior similar to kerosene and can be used instead of the actual Jet A fuel to study the effect of the chemical composition and fuel properties, would be useful both in experimental investigations and in Received 28 September 2007; accepted 28 March 2008. This work was performed under partial financial support of the IPP Project ANL-T2-220-RU, sponsored by the U.S. Department of Energy IPP Program. Address correspondence to M. I. Strelkova, RRC Kurchatov Institute, Kurchatov sq. 1, Moscow, 123182, Russia. E-mail:
[email protected]
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Figure 1 Normalized total ion chromatograms for Jet A liquid (a) and vapor (b) phases.
computational modeling. In addition, the replacement of the real fuel by its surrogate makes it possible to apply first-principles methods to evaluate the kinetic and thermodynamic parameters required for detailed mechanism development. It allows the detonation and combustion characteristics of engineering interest to be predicted at a macroscopic level. During the modeling of homogeneous kerosene combustion different surrogates were studied: one-component surrogate, in which decane was chosen, was investigated in the works Vovelle et al. (1991) and Doute´ et al. (1995); twocomponent surrogates, consisted of n-decane and various aromatics (benzene, toluene, ethyl benzene=naphthalene) were considered in Lindstedt et al. (2000) and Patterson et al. (2001) papers; three-component surrogates, were suggested by Gue´ret et al. (1990) and Dagaut (2002). Cooke et al. (2005) studied the combustion of a 6-component model fuel, Mawid et al. (2003) used a 12-component fuel blend for developing of detailed chemical kinetic mechanism describing the ignitionoxidation of Jet A. Edwards and Maurice (2001) wrote the literature survey of fuel blends and surrogates in which they gave the recommendations for various classes of surrogate applications. The most comprehensive review of surrogates, available experimental data and kinetic schemes used for simulating ignition, oxidation and combustion of kerosene was given by Dagaut and Cathonnet in (2006). However detailed mechanisms developed for these surrogates contain many chemical species and elementary chemical reactions. Computational Fluid Dynamics (CFD) models that combine detailed chemical reaction mechanisms and fluid dynamics processes such as turbulence and mass transport to simulate multidimensional reacting flows are faced with serious computational difficulties due to the substantially increasing the computational time. This problem can be solved by using very simplified reduced chemical reaction mechanisms. But to accurately describe the combustion phenomena the appropriate reduced mechanism must first be derived from the detailed mechanism. The aims of this work are: 1. Choose the surrogate that can demonstrate detonation and combustion characteristics similar to its parent fuel Jet A;
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2. Develop a detailed first-principles mechanism for selected surrogate that describes the available experimental data for Jet A kerosene combustion and estimates the detonation reasonably well for the following conditions: . initial temperature 1000 –1800 K; . initial pressure: 1, 10, 100 atm; . equivalence ratio u: 0.5, 1, 2 3. Reduce the detailed mechanism of Jet A surrogate combustion so that the reduced mechanism can be used in conjunction with a CFD code for calculations of detonation processes and verify its results through comparisons with the detailed mechanism results and the available experimental data.
Surrogate Chosen for Elaboration of the Detailed Mechanism of Jet A Combustion A surrogate mixture of 72.7 wt% decane þ 9.1 wt% hexane þ 18.2 wt% benzene was chosen for the development of the detailed kinetic model of Jet A combustion. This surrogate was investigated in heated shock tube equipment by Dean et al. (2006). This surrogate was selected because: (a) its composition reproduces the vapor phase of Jet A fuel rather well, and (b) this surrogate has experimentally demonstrated good agreement of the ignition delay time and dynamics of reflected shock propagation with the corresponding characteristics of Jet A in a heated shock tube and thus could serve as surrogate for aviation kerosene (Dean et al., 2006).
Elaboration of High-Temperature Detailed Kinetic Mechanism of Jet A Surrogate Combustion Based on a Multilevel Approach The construction of the Jet A aviation kerosene surrogate (72.7% n-decane þ9.1% n-hexane þ18.2% benzene) combustion mechanism was performed using a multilevel approach. Level 1. At the first level the detailed chemical mechanism of Jet A surrogate combustion was constructed. The mechanism was built in a logical, hierarchical manner taking into account that hydrocarbon chemistry as determined by reactivity of the few functional groups. The initial set of the reactions rates have been taken mainly from the following papers on combustion mechanism development: for n-decane (Lindstedt et al., 2000; Bikas et al., 2001), for n-hexane (Curran et al., 1998), and for benzene (Dinaro et al., 2000) combustion mechanism development. Thermodynamic data were taken from Burcat et al. (2005). The detailed mechanism of Jet A surrogate combustion is constructed in such a way consisting of 417 elementary reversible reactions and 71 components. Level 2. At the second level, the rate constants of the elementary reactions entering the detailed mechanism were verified and those unknown were estimated using the similarity approach. This verification was based upon most recent compilation of experimental rate constants of reactions important in combustion (Baulch
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et al., 2005), qualitative physical and chemical arguments (spin conservation, orders of magnitude of pre-exponential factors) and thermo-chemical data. After that the sensitivity and rate of production analyses were made to identify the key species and reactions. Level 3. For cases where the accuracy of thermochemical and kinetic data for important reactions and species were considered insufficient, a first principle study based on modern quantum chemistry and microscopic theory of chemical reactions was initiated. The following groups of reactions were calculated from first principles, based on modern quantum chemistry and microscopic theory of chemical reactions: (1) The initiation reactions CnH2nþ2þO2 ¼ CnH2nþ1þHO2 (2) Reactions CHþCnH2nþ2 Quantum-chemical calculations were performed with the GAUSSIAN-03 program package (Frisch et al., 1998) using the (CCSD)==BH & HLYP level of theory. The geometries and frequencies of reactants, transition and intermediate complexes, and products were calculated in the framework of the density functional theory with the hybrid BH & HLYP functional. The electronic energies of these species were evaluated at the CCSD level. The ab initio results obtained for the first five alkanes were extrapolated to higher alkanes (n-C6H14, n-C10H22) using the Benson similarity group method (Benson, 1976). . Initiation reactions CnH2nþ2 þ O2 ¼ CnH2nþ1 þ HO2 The initiation reactions cannot be studied in direct experiments due to their high activation energies. DFT calculations (with the BH & HLYP functional) were performed for the reactions from methane up to n-pentane (n ¼ 1 through 5). Although the barrier heights of these reactions calculated at the same level of theory were published previously, we calculated the vibration frequencies of the reactants and the transition states, which are unavailable in the literature and are required for further kinetics calculations. Using obtained vibration frequencies of the reactants and the transition states, the reaction constants were calculated using Chemical Work Bench code (Deminsky et al., 2003). In frame of the similarity method approach, quantum-chemical analysis of alkanes (CH4, C2H6, C3H8, n-C4H10, n-C5H12) with O2 permits us to choose the reaction constants for n-hexane and n-decane. All these reactions with corresponding constants are summarized in Table 1. Ab initio calculations proved the fact accepted in the kinetic literature that the activation energy of H-abstraction reactions between alkanes and O2 is equal to the enthalpy of these reactions (the reverse reactions has no potential barrier). It is interesting that the ab initio rate constants calculated for reactions with the participation of CH4 and C2H6 agree well with the rather uncertain experimental data given in Baulch et al., 2005 (see Fig. 2a). . Reactions CH þ CnH2nþ2 This reaction as itself really does not play an important role in the kinetic of Jet A surrogate combustion. But as it processes through intermediate
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M. I. STRELKOVA ET AL. Table 1 Reaction rate constants Direct
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Reactions CH4 þ O2 () CH3 þ HO2 C2H6 þ O2 () C2H5 þ HO2 C3H8 þ O2 () C3H7=1= þ HO2 C3H8 þ O2 () C3H7=2= þ HO2 C4H10 þ O2 () C4H9=1= þ HO2 C4H10 þ O2 () C4H9=2= þ HO2 C5H12 þ O2 () C5H11=1= þ HO2 C5H12 þ O2 () C5H11=2= þ HO2 C6H14 þ O2 () C6H13=1= þ HO2 C6H14 þ O2 () C6H13=2= þ HO2 C10H22 þ O2 () C10H21=1= þ HO2 C10H22 þ O2 () C10H21=2= þ HO2 C6H6 þ O2 () C6H5 þ HO2
Reverse
A (cm3=s)
n
Ea (kcal=mol)
A (cm3=s)
n
Ea (kcal=mol)
7.87*1021 1.01*1021 3.38*1022 1021 8.7*1022 8*1022 3.9*1022 4.1*1022 3.9*1022 4.1*1022 3.9*1022 4.1*1022 1.3*1020
3.4 3.38 3.38 3.35 3.35 3.35 3.48 3.34 3.5 3.4 3.5 3.4 3.2
52.46 48.6 48.88 45.51 48.86 45.54 48.86 45.76 49 46 49 46 61.45
1.7*1022 3.76*1024 2.08*1024 2.*1024 4.8*1024 1.4*1024 1.5*1024 1.6*1024 1.5*1024 1.6*1024 1.5*1024 1.6*1024 0.84*1025
3.3 3.32 3.33 3.34 3.3 3.34 3.32 3.34 3.32 3.34 3.32 3.34 3.35
5.34 5.4 5.33 5.37 5.13 5.3 5.41 5.05 5.41 5.05 5.41 5.05 4.93
Reaction rates are expressed in form k ¼ ATn exp(Ea=RT), where A (cm3=molec=s) is the preexponential factor, Ea (kcal=mol) is activation energy, R (cal=mol=K) is the ideal gas constant, T (K) is temperature.
complexes–primary and secondary alkyl radicals, the information about channels of alkyl dissociation is very important, and those reactions must be considered during the creation and reduction of the detailed mechanism. In Figure 2b the potential energy diagram for the reaction CHþC2H6 is shown as example.
Figure 2 Ab initio calculations: (a) rate constants calculated for reactions C2H6 þ O2 (squares) and C5H12 þ O2 (triangles) in comparing with Baulch et al. (2005) recommended constant for reaction C2H6 þ O2 ¼ C2H5 þ HO2 (solid line); (b) potential energy diagram of reaction CH þ C2H6.
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Validation of Detailed Mechanism of Jet A Surrogate Combustion The validation of the detailed mechanism was carried out by comparing the simulated results, using this mechanism, with simulated and experimental data. Computational results were carried out using Chemical Work Bench code (Deminsky et al., 2003), which solves the coupled chemical kinetic and energy equations, and permits the use of a variety of initial conditions for reactive systems, depending on the needs of the particular system being examined. Calculations were made on the next reactor models: (a) the adiabatic Calorimetric Bomb Reactor (CBR) at constant volume, which describes the time evolution of the chemical composition and gas parameters under the effect of chemical reactions, external actions of heating or cooling; (b) the Chapman-Jouguet Reactor (CJ), which computes the static detonation parameters for the given initial thermochemical parameters (Po, To, chemical composition) of the reactive mixture; and (c) ZND Reactor, which permits the calculation of the detonation wave structure. . Validation of Jet A surrogate thermodynamic parameters Static detonation parameters (Velocity VCJ, Pressure PCJ, Temperature TCJ) for Jet A surrogate were calculated using CJ and ZND models. The simulated results
Figure 3 Comparison of thermodynamic parameters (a) TCJ, (b) PCJ, and (c) VCJ, calculated by the CWB code (triangles) for the Jet A surrogate with the results, obtained by the CEA code (McBride et al., 2003) (solid line) for Jet A at different initial pressures P: (1) 1, (2) 2, (3) 4, (4) 6, and (5) 8 atm, u ¼ 1.
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Figure 4 Velocity of reflected shock wave, obtained by Dean (2006) (triangles) and simulated C-J velocity (dash line) vs. initial temperature in stoichiometric Jet A surrogate=air mixture.
were compared with similar calculations made using the CEA code (McBride et al., 2003) for the Jet A fuel. Similar results were obtained for mixtures with equivalence ratios 0.5 and 2. Good agreement was obtained for the thermodynamics of the chosen surrogate and Jet A as shown in Figure 3, with the discrepancy for VC–J and TC–J being less than 1.8%. The experimental results for the reflected shock wave velocity at a 173-mm distance from the end wall (Dean et al., 2006) and the calculated C–J velocity VCJ for a stoichiometric Jet A surrogate–air mixture are shown in Figure 4. It is clear that the calculated velocity VCJ in the Jet surrogate mixture is in a good agreement with experimental results. The structure of the detonation wave was studied using the ZND model. This model can be used to obtain a qualitative estimation of the detonation capability of gaseous mixtures. The ZND profiles for the pressure and the temperature of the Jet A surrogate–air mixture at P0 ¼ 1.87 atm and T0 ¼ 787 K (initial experimental conditions) were obtained (Fig. 5).
Figure 5 ZND profiles for pressure (a) and temperature (b) of Jet A surrogate – air mixture at Po ¼ 1.87 atm and To ¼ 787 K (initial experimental conditions).
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. Validation of induction time The predicted induction time is studied in CBR (VQ) reactor and based on the time-history of CH and OH radicals. In the case of OH radicals, the ignition time is defined as the time at which the OH formation rate reaches its maximum value. In the framework of the detailed mechanism each surrogate component (n-decane, n-hexane, benzene) was validated using available experimental data. The induction times of n-decane (a), n-hexane (b), and benzene (c), predicted for temperatures 1000–1800 K at pressures 1 atm, 10 atm, and 100 atm with equivalence ratio 1 are shown in Figure 6. The calculated results were compared with the corresponding experimental data. It is clear that calculated and experimental results are in a good agreement. But at 10 atm pressure, for temperatures substantially below 1200 K, we observed discrepancies. This disagreement is expected since the high-temperature mechanism utilized here does not include radical-oxygen addition reactions characteristic of low and intermediate temperature oxidation of large carbon number species.
Figure 6 Comparison of simulated induction time (line) of each components of Jet A surrogate (u ¼ 1) n-decane (a), n-hexane (b), benzene (c) combustion at P ¼ 10 atm with experimental data: ~ at 8–9.5 atm atm (Dean et al., 2006), & at 12 atm (Buda et al., 2004), 8 at 13 atm (Pfahl et al., 1996), at 13 atm and ^ at 39 atm (Fieweger et al., 1994).
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Figure 7 Comparison of simulated ignition times (solid line) obtained with the detailed kinetic scheme of Jet A surrogate combustion with experimental results, obtained by Gokulakrishnan et al. (2007) for JP8 (triangles) and by Freeman et al. (1984) for Jet A at Po ¼ 1 atm for mixtures with u ¼ 0.5 (a) and 1 (b).
The validation of induction times of Jet A surrogate combustion were carried out by comparing the simulated results with the appropriate experimental data. For validation the measured ignition delay times were taken from: a) experiments in flow reactor with JP 8 fuel (Gokulakrishnan et al., 2007) and Jet A (Freeman, 1984) at atmospheric pressure for mixtures with u ¼ 0, 5, 1 (Fig. 7);
Figure 8 Comparison of simulated ignition times (solid line) obtained with the detailed kinetic scheme of Jet A surrogate combustion at Po ¼ 10 atm with experimental results, carried out by Dean et al. (2006) for Jet A (square) and Jet A surrogate (sign) at Po ¼ 9.1–9.5 atm for equivalence ratios u: (a) 0.5, (b) 1, and (c) 2.
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b) experiments (Dean et al., 2006) with similar surrogate and Jet A in reflected shock waves at a post-shock pressure of 10 atm within the post-shock temperature range 1000–1700 K for lean, stoichiometric, and rich Jet-A=Air mixtures (u ¼ 0.5, 1, 2) (Fig. 8). As is clear from Figure 7 for lean and stoichiometric mixtures at Po ¼ 1 atm, our results agree well with experimental data obtained in the flow reactor. For lean and stoichiometric mixtures at initial pressure of 10 atm, we obtained satisfactory agreement with experiments in the reflected shock waves. But for rich mixtures, the disagreement is observed. The experimental results available for reach mixtures were those where experiments were carried out only in one group (Dean et al., 2006). To clarify the reason of this disagreement, it is necessary to have more experimental data. The comparison of predicted induction times, obtained using detailed mechanism of Jet A surrogate combustion with experimental data has shown that the chosen surrogate describes the combustion and detonation behavior for its parent fuel Jet A rather well.
Figure 9 C-fluxes in n-decane-air stoichiometric combustion at temperature 1400 K.
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2e-21 1.26e-17 1.66e-16 4.07e-11 2e-21 9.55e-16 4.68e-16 2.44e-11 1.58e-20 3.39e-11 2.69e-16 1.7e-11 9.33e-11 3.02e-12 5.62e-32 5.37e-11 1.26e-29 3.29e-22 3.39e-11
C10H22 þ O2 ¼> C2H5 þ 4C2H4 þ HO2 C10H22 ¼> 2C2H5 þ 3C2H4 C10H22 þ OH ¼> C2H5 þ 4C2H4 þ H2O C10H22 þ HO2 ¼> C2H5 þ 2C2H4 þ 2OH C6H14 þ O2 ¼> C2H5 þ 2C2H4 þ HO2 C6H14 ¼> 2C2H5 þ C2H4 C6H14 þ OH ¼> C2H5 þ 2C2H4 þ H2O C6H14 þ HO2 ¼> C2H5 þ 2C2H4 þ 2OH C6H6 þ O2 ¼> C6H5 þ HO2 C6H6 þ O ¼> C5H5 þ CO þ H C6H6 þ OH ¼> C6H5 þ H2O C6H5 þ O2 ¼> C5H5 þ CO þ O C5H5 þ O ¼ C5H4O þ H C5H5 þ O2 ¼> C5H4O þ H C5H4O ¼> 2C2H2 þ H2O C5H5 þ O ¼> C2H2 þ C2H2 þ HCO C2H4 þ H þ M ¼ C2H5 þ M C2H4 þ H ¼> C2H3 þ H2 C2H4 þ OH ¼> C2H3 þ H2O
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
3.4 0 2 0 3.4 0 1.61 0 3.2 0 1.42 0 0.02 0.08 6.76 0.17 0 3.62 0
n 46 81 0.76 17 46 81 0.04 17 61.5 43 1.45 3.6 0.02 18 68.5 0.44 0.76 11.3 5.96
Ea 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
N C2H3 þ O2 ¼> HCO þ CH2O C2H3 þ H ¼> C2H2 þ H2 CH2O þ OH ¼> HCO þ H2O HCO þ O2 ¼> HO2 þ CO HCO þ M ¼ H þ CO þ M C2H2 þ O ¼> HCCO þ H HCCO þ O ¼> H þ CO þ CO CO þ OH ¼ CO2 þ H H þ O2 ¼ O þ OH H þ O2 þ M ¼ HO2 þ M OH þ H2 ¼ H2O þ H OH þ OH ¼ H2O þ O HO2 þ H ¼> OH þ OH HO2 þ OH ¼> H2O þ O2 CH2O þ H ¼> CHO þ H2 HO2 þ H ¼> H2 þ O2 HO2 þ HO2 ¼ H2O2 þ O2 OH þ OH þ M ¼ H2O2 þ M H þ OH þ M ¼ H2O þ M
Reactions 6.46e-12 3.31e-11 5.75e-15 2.24e-11 3.1e-7 1.55e-15 1.58e-10 1.51e-17 3.39e-10 7.76e-30 3.63e-16 5.5e-20 7.41e-10 4.79e-11 9.55e-17 1.75e-10 7e-10 6.31e-30 6.17e-26
A
0 0 1.18 0 1 1.4 0 1.5 0.1 0.86 1.52 2.42 0 0 1.9 0 0 0.9 2
n
0.24 2.5 0.45 0.4 17 2.22 0 0.5 15.12 0 3.48 1.94 1.4 0.497 2.74 2.06 12.6 1.7 0
Ea
Reaction rates are expressed in form k ¼ ATnexp( Ea=RT), where A (cm, molec, s) is the pre-exponential factor, Ea (kcal=mol) is activation energy, R (cal=mol=K) is the ideal gas constant, and T (K) is temperature.
A
Reactions
N
Table 2 Reduced mechanism of Jet A surrogate combustion
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Elaboration of the Reduced Kinetic Mechanism for Jet A Surrogate Combustion The utilization of the detailed mechanism described here is unfortunately impossible in computational fluid dynamic codes simulating a practical combustor because of CPU time and computer memory limitations. As a result, it is important to minimize the number of chemical reactions and species required for the simulation of combustion processes. The reduction of detailed mechanism was made in the framework of two-stage procedure. At the first stage reaction pathway analysis was used to exclude minor reactions and whole reaction pathways. At the second stage sensitivity analysis tools was used to build species and reactions priorities lists. The list of reactions and species was use afterwards for discrimination of unimportant components and reactions. Both these analyses are available in Chemical Workbench code. In all cases we controlled the deviation of the kinetics curves of reduced mechanism from those of the detailed mechanism in order to keep it within 50% accuracy for the pressure range from 1 atm to 100 atm and temperatures 1100 –1800 K.
Figure 10 Comparison results, predicted by detailed (line) and reduced (dash line) mechanisms of Jet A surrogate combustion for stoichiometric mixture: (a) time-history of final products at To ¼ 1200 K, Po ¼ 10 atm; (b) time-history of temperature at initial pressure 10 atm and To ¼ 1200 K (1), 1400 K (2), 1600 K (3); (c) induction times at initial pressures 1 atm (1), 10 atm (2), 100 atm (3).
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Reduction was started with a lumping procedure. The lumping process of detailed mechanism is performed in three steps–the lumping of alkyl isomers, lumping of primary elementary reactions and the estimation of lumped kinetic parameters. We used the detailed lumping procedure, described by Fournet et al. (2000). Reaction pathway analysis is performed as postprocessor code in Chemical Workbench. It permits to visualize the reaction fluxes. In this plot the species are presented as labeled boxes and the element fluxes among the species as arrows. The width of arrows is proportional to the logarithm of the element fluxes. In Figure 9 the change of the C-fluxes among the species with the reaction progress can be seen for stoichiometric n-decane consuming at T ¼ 1400 K. It is clear that that the major paths of n-decane consuming are its thermal decomposition with formation primary alkyl radicals and OH and HO2 attack leading to H-abstraction with decyl formation, followed by destruction with smaller alkyl radical and olefins formation. Sensitivity analyses were also carried out for intermediate products and radicals, formed during the surrogate combustion. Using the quasi-stationary approach for intermediate alkyl radicals and carrying out the sensitivity and rate production rate analyses led to a reduced mechanism of high-temperature Jet A surrogate combustion, consisting of 38 reactions and 24 species. This reduced mechanism is shown in Table 2. This reduced mechanism was validated through comparison with the detailed mechanism. The comparisons of temperature time histories and induction times, obtained using the detailed mechanism, the reduced mechanism and corresponding experimental results are shown in
Figure 11 Induction time, simulated by using Jet A surrogate detailed (line) and reduced (dash line) mechanisms and experimental data, obtained by Dean et al. (2006) for Jet A (square) and Jet A Surrogate (sign) at Po ¼ 9.1–9.5 atm. Equivalence ratios u ¼ 1 (a), 0.5 (b), 2 (c).
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Figures 10 and 11. Good agreements for induction times, temperature and main concentrations behavior, predicted by detailed and reduced mechanisms for the following conditions are obtained:
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. initial temperatures 1000–1800 K, . pressures 1 atm, 10 atm and 100 atm, . equivalence ratios u: 0.5, 1 and 2. CONCLUSIONS A three-species (72.7 wt% decane þ 9.1 wt% hexane þ 18.2 wt% benzene) surrogate mixture representing Jet A fuel was chosen for the development of the first-principles detailed kinetic model of Jet A combustion. This detailed mechanism, consisted of 417 reversible reactions and 71 components, was validated against available experimental data for Jet A combustion at pressure of 1, 10 atm for lean, stoichiometric and rich Jet A=air mixtures (u ¼ 0.5, 1, 2) within the temperature range of 1000–1700 K and against simulated results, obtained on CEA code for Jet A and shown to provide good agreements. A reduced mechanism of Jet A surrogate combustion was obtained based on the detailed mechanism, which was implemented in CFD simulations of gas turbine combustors. This mechanism consists of 38 reactions and 24 species and can be utilized in wide range of temperatures, pressures and equivalent ratios. The reduced mechanism results were shown to be in reasonable agreement with detailed mechanism results, which are, in turn, in reasonable agreement with the measurements. Both these mechanisms with thermodynamic data in Chemkin format can be obtained from authors by request. The capability of the 3-component Jet A surrogate fuel to predict the ignition delay times as well as pressure, temperature and velocity of detonation for Jet A fuel over wide temperature and pressure range was shown. REFERENCES Baulch, D.L., Bowman, C.T., Cobos, C.J., Cox, R.A., Just, Th., Kerr, J.A., Pilling, M.J., Stocker, D., Troe, J., Tsang, W., Walker, R.W., and Warnatz, J. (2005) Evaluated kinetic data for combustion modeling: Supplement II. J. Phys. Chem. Ref. Data, 34(3), 757. Benson, S.W. (1976) Thermochemical Kinetics, Wiley, New York. Bikas, G. and Peters, N. (2001) Kinetic modeling of n-decane combustion and autoignition. Combust. Flame, 126(1), 1456. Buda, F., Glaude, P.A., Battin-Leclerc, F., Porter, R., Hughes, K.J., and Griffiths, J.F. (2004) Use of detailed kinetic mechanisms for the prediction of autoignitions. Fifth International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions, ISHPMIE, 235. Burcat, A. and Ruscic, B. Ideal Gas Thermochemical Database with updates from Active Thermo chemical Tables. http://garfield.chem.elte.hu/Burcat/burcat.html Cooke, J.A., Bellucci, M., Smooke, M.D., Gomez, A., Violi, A., Favarelli, T., et al. (2005) Computational and experimental study of JP-8, a surrogate, and its components in counterflow diffusion flames. Proc. Combust. Instit., 30, 439. Curran, H.J., Gaffuri, P., Pitz, W.J., and Westbrook, C.K. (1998) A comprehensive modeling study of n-heptane oxidation. Combust. Flame, 114, 149.
Downloaded by [Russian Research Centre - Kurchatov Institute] at 03:14 19 September 2013
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M. I. STRELKOVA ET AL.
Dagaut, P. (2002) On the kinetics of hydrocarbons oxidation from natural gas to kerosene and diesel fuel. Phys. Chem. Chem. Phys., 4, 2079. Dagaut, P. and Cathonnet, M. (2006) The ignition, oxidation and combustion of kerosene: A review of experimental and kinetic modeling. Prog. Energy Combust. Sci., 32, 48. Dean, A.J., Penyazkov, O.G., Sevruk, K.L., and Varatharajan, B. (2006) Avtoignition of surrogate fuels at elevated temperatures and pressures. Proc. Combust. Instit., 28, 1529. Deminsky, M., Chorkov, V., Belov, G., Cheshigin, I., Knizhnik, A., Shulakova, E., Shulakov, M., Iskandarova, I., Alexandrov, V., Petrusev, A., Kirillov, I., Strelkova, M., Umanskii, S., and Potapkin, B. (2003) Chemical Workbench—Integrated environment for materials science. Computational Materials Science, 28, 169. Dinaro, J.L., Howard, J.B., Green, W.H., Tester, J.W., and Bozzeli, J.W. (2000) Analysis of an elementary reaction mechanism for benzene oxidation in supercritical water. Proc. Combust. Instit., 28, 1529. Doute´, C., Delfau, J.L., Akrich, R., and Vovelle, C. (1995) Chemical structure of atmospheric pressure premixed n-decane and kerosene flames. Combust. Sci. Technol., 106, 327. Edwards, T. and Maurice, L.Q. (2001) Surrogate mixtures to represent complex aviation and rocket fuels. J. Propulsion and Power, 17, 461. Fieweger, K., Blumenthal, R., and Adomeit, G. (1994) Proc. Combust. Instit., 25, 1579. Fournet, R., Warth, V., Glaude, P.A., Battin-Leclerc, F., Scacchi, G., and Come, G.M. (2000) Automatic reduction of detailed mechanisms of combustion of alkanes by chemical lumping. Intl. J. Chem. Kinet., 32(1), 36. Freeman, G. and Lefebvre, A.H. (1984) Spontaneous ignition characteristics of gaseous hydrocarbon-air mixtures. Combust. Flame, 58, 153. Frisch, M.J. et al. (1998) GAUSSIAN98, Revision A. 3, Gaussian Inc., Pittsburgh, PA. Gokulakrishnan, P., Gaines, G., Klassen, M.S., and Roby, R.J. (2007) Autoignition of aviation fuels: Experimental and modeling study. Proc. of 43 Joint Propulsion Conferences, Cincinnati, OH. Gue´ret, C., Cathonnet, M., Boettner, J.C., and Gaillard, F. (1990) Experimental study and modeling of kerosene oxidation in a jet-stirred flow reactor. Proc. Combust. Instit., 23, 211. Lindstedt, R.P. and Maurice, L.Q. (2000) Detailed chemical-kinetic model for aviation fuels. J. Propul. Power, 16, 187. Mawid, M., Park, T., Sekar, B., and Arana, C. (2003) Development of detailed chemical kinetic mechanisms for ignition=oxidation of JP-8=JetA=JP=7 fuels. Proceedings of ASME Turbo Expo 2003 Power for Land, Sea, and Air, Atlanta, Georgia, USA. McBride, B.J. and Gordon, S. (1994) Computer program for calculation of complex chemical equilibrium compositions and applications- ii users manual and program description. NASA Reference Publication, 1311. Patterson, P.M., Kyne, A.G., Pourkhashanian, M., Williams, A., and Wilson, C.W. (2001) Combustion of kerosene in counterflow diffusion flames. J. Propul. Power, 16, 453. Pfahl, U., Fieweger, K., and Adomeit, G. (1996) Shock tube investigation of ignition delay times of multi-component fuel=air mixtures under engine relevant conditions. Final Report, Subprogramme FK4, IDEA-EFFECT. Shepherd, J.E., Nuyt, C.D., and Lee, J.J. (2000) Explosion Dynamics Lab. Report FM99-4. Vovelle, C., Delfau, J.L., Reuillon, M., Ackrich, R., Bouhria, M., and Sanogo, O. (1991) Comparison of aromatics formation in decane and kerosene flames. Proceedings of the ACS Natl. Mtg., 36(4), 1456.
