scholarly journals Reduced Combustion Mechanism for Fire with Light Alcohols

Fire ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 86
Author(s):  
Fekadu Mosisa Wako ◽  
Gianmaria Pio ◽  
Ernesto Salzano
Keyword(s):  
Alternative Fuels ◽  
Product Distribution ◽  
Transportation Systems ◽  
Combustion Mechanism ◽  
Primary Alcohols ◽  
Cfd Models ◽  
Reduced Mechanism ◽  
Soot Precursors ◽  
Kinetic Mechanisms ◽  
Flash Fire

The need for sustainable energy has incentivized the use of alternative fuels such as light alcohols. In this work, reduced chemistry mechanisms for the prediction of fires (pool fire, tank fire, and flash fire) for two primary alcohols—methanol and ethanol—were developed, aiming to integrate the detailed kinetic model into the computational fluid dynamics (CFD) model. The model accommodates either the pure reactants and products or other intermediates, including soot precursors (C2H2, C2H4, and C3H3), which were identified via sensitivity and reaction path analyses. The developed reduced mechanism was adopted to predict the burning behavior in a 3D domain and for the estimation of the product distribution. The agreement between the experimental data from the literature and estimations resulting from the analysis performed in this work demonstrates the successful application of this method for the integration of kinetic mechanisms and CFD models, opening to an accurate evaluation of safety scenarios and allowing for the proper design of storage and transportation systems involving light alcohols.

Evaluation of Kinetic Mechanisms for Direct Fired Supercritical Oxy-Combustion of Natural Gas

2016 ◽  
Author(s):  
Shane Coogan ◽  
Xiang Gao ◽  
Aaron McClung ◽  
Wenting Sun
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
San Diego ◽  
Laminar Flame ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Validation Data ◽  
Data Set ◽  
Reduced Mechanism ◽  
Kinetic Mechanisms

Existing kinetic mechanisms for natural gas combustion are not validated under supercritical oxy-fuel conditions because of the lack of experimental validation data. Our studies show that different mechanisms have different predictions under supercritical oxy-fuel conditions. Therefore, preliminary designers may experience difficulties when selecting a mechanism for a numerical model. This paper evaluates the performance of existing chemical kinetic mechanisms and produces a reduced mechanism for preliminary designers based on the results of the evaluation. Specifically, the mechanisms considered were GRI-Mech 3.0, USC-II, San Diego 204-10-04, NUIG-I, and NUIG-III. The set of mechanisms was modeled in Cantera and compared against the literature data closest to the application range. The high pressure data set included autoignition delay time in nitrogen and argon diluents up to 85 atm and laminar flame speed in helium diluent up to 60 atm. The high carbon dioxide data set included laminar flame speed with 70% carbon dioxide diluent and the carbon monoxide species profile in an isothermal reactor with up to 95% carbon dioxide diluent. All mechanisms performed adequately against at least one dataset. Among the evaluated mechanisms, USC-II has the best overall performance and is preferred over the other mechanisms for use in the preliminary design of supercritical oxy-combustors. This is a significant distinction; USC-II predicts slower kinetics than GRI-Mech 3.0 and San Diego 2014 at the combustor conditions expected in a recompression cycle. Finally, the global pathway selection method was used to reduce the USC-II model from 111 species, 784 reactions to a 27 species, 150 reactions mechanism. Performance of the reduced mechanism was verified against USC-II over the range relevant for high inlet temperature supercritical oxy-combustion.

Improvements on a Newton-Krylov Based Solver for CFD Models Using Finite Rate NOx Chemistry

2004 ◽  
Author(s):  
Qing Tang ◽  
Martin Denison ◽  
Mike Maguire ◽  
Mike Bockelie ◽  
Jyh-Yuan Chen
Keyword(s):  
Electric Utility ◽  
Iteration Scheme ◽  
Cfd Modeling ◽  
Finite Rate ◽  
Modeling Tool ◽  
Krylov Method ◽  
Cfd Models ◽  
Reduced Mechanism ◽  
Computational Fluid Dynamics Cfd ◽  
Matrix Free

In this paper, we describe our progress on improving the performance of a newly developed Computational Fluid Dynamics (CFD) modeling tool, which uses reduced chemical kinetics mechanisms to model the finite rate chemistry effects and solves the resulting system of stiff partial differential equations with a matrix-free Newton-Krylov method. A multi-grid based preconditioner and a Newton iteration scheme have been implemented in the Newton-Krylov solver and the reduced mechanism module, respectively, to replace the original Picard based preconditioner and the point iteration scheme for steady state species evaluation. Preliminary tests of the improved modeling tool have been conducted using simple hotbox and a full-scale, coal fired electric utility boiler, and shown very promising results in terms of the accuracy, robustness, and efficiency of the new tool.

scholarly journals Fuel-Rich Premixed n-Heptane/Toluene Flame: a Molecular Beam Mass Spectrometry and Chemical Kinetic Study

2014 ◽  
Vol 16 (2-3) ◽  
pp. 219
Author(s):  
D.A. Knyazkov ◽  
N.A. Slavinskaya ◽  
A.M. Dmitriev ◽  
A.G. Shmakov ◽  
O.P. Korobeinichev ◽  
...  
Keyword(s):  
Mole Fraction ◽  
Volume Ratio ◽  
Chemical Kinetic ◽  
Liquid Volume ◽  
Data Set ◽  
Kinetic Reaction ◽  
Molecular Beam Mass Spectrometry ◽  
Soot Precursors ◽  
Kinetic Mechanisms ◽  
Fuel Surrogates

<p>The mole fraction profiles of major flame species and intermediates including PAH precursors are measured in an atmospheric premixed burner-stabilized fuel-rich (<em>φ</em> = 1.75) <em>n</em>-heptane/toluene/O<sub>2</sub>/Ar flame (<em>n</em>-heptane/toluene ratio is 7:3 by liquid volume). These data are simulated with a detailed, extensively validated chemical kinetic reaction mechanism for combustion of <em>n</em>-heptane/toluene mixture, involving the reactions of PAH formation. The mechanism is extended with cross reactions for <em>n</em>-heptane and toluene derivatives. A satisfactory agreement between the new experimental data on the structure of <em>n</em>-heptane/toluene flame and the numerical simulations is observed. The mechanism reported can be successfully used in the models of practical fuel surrogates for reproducing the formation of soot precursors. The analysis of the reaction pathways shows that in the flame of the <em>n</em>-heptane/toluene blend (7:3 liquid volume ratio) the reactions dominant for the formation of the first aromatic ring (benzene and phenyl) are as those typical for pure toluene flames. The discrepancies between the measured and calculated species mole fractions are detected as well. The steps for the mechanism improvements are determined on the basis of the sensitivity analysis performed. To our knowledge, the measurements of mole fraction profiles of PAH and intermediates reported here, are the first of its kind and represent an unique data set extremely important for validation of chemical kinetic mechanisms for combustion of practical fuels.</p><p> </p>

scholarly journals Evaluation of reduced chemical kinetic mechanisms used for modeling mild combustion for natural gas

2009 ◽  
Vol 13 (3) ◽  
pp. 131-137 ◽  
Author(s):  
Mohamed Hamdi ◽  
Hmaeid Benticha ◽  
Mohamed Sassi
Keyword(s):  
Natural Gas ◽  
Chemical Kinetic ◽  
Gas Temperature ◽  
Combustion Mode ◽  
Reduced Mechanism ◽  
Mild Combustion ◽  
Reduced Chemistry ◽  
Key Species ◽  
Kinetic Mechanisms ◽  
Step Mechanism

A numerical and parametric study was performed to evaluate the potential of reduced chemistry mechanisms to model natural gas chemistry including NOx chemistry under mild combustion mode. Two reduced mechanisms, 5-step and 9-step, were tested against the GRI-Mech3.0 by comparing key species, such as NOx, CO2 and CO, and gas temperature predictions in idealized reactors codes under mild combustion conditions. It is thus concluded that the 9-step mechanism appears to be a promising reduced mechanism that can be used in multi-dimensional codes for modeling mild combustion of natural gas.

scholarly journals Formation of Cyclic Compounds in Cracking Reactions for Hydrocarbon-Fueled High Speed Vehicles

1999 ◽  
Author(s):  
R. C. Striebich ◽  
L. Q. Maurice ◽  
T. Edwards
Keyword(s):  
Gas Phase ◽  
High Speed ◽  
Computational Models ◽  
Fuel System ◽  
Growth Mechanisms ◽  
Soot Precursors ◽  
Experimental Apparatus ◽  
Kinetic Mechanisms ◽  
Fuel Reactor ◽  
Cyclic Compounds

An endothermic fuel pyrolytic reactor may favor the formation of benzene and polynuclear aromatic hydrocarbon (PAH) soot precursors which degrade fuel system performance. Both experimental and computational studies are in progress which verify the formation of multi-ring aromatic compounds in endothermic thermal cracking processes. Classic gas phase pyrolytic soot mechanisms may be effective for the prediction of soot precursor concentrations. Hence, a need exists to examine thermal molecular growth processes in a versatile experimental apparatus which can help guide modeling efforts and increase basic understanding (and mitigation) of growth mechanisms. In the present work, cyclic formation experimental data are presented for three mixtures: n-decane, 90 volume % n-decane/10 volume % toluene, and 80 volume % n-decane/20 volume % toluene pyrolysis in a System for Thermal Diagnostic Studies (STDS). The data are qualitatively and quantitatively compared to computations at temperatures, pressures and residence times commensurate with those encountered in endothermic fuel reactor systems. These computations are an attempt to assess the applicability of gas-phase kinetic mechanisms to predict the chemistry of thermal decomposition in the fuel system. Preliminary results show the prominence of molecular growth reactions similar to gas phase pyrolysis mechanisms, starting with hydrocarbon unsaturation, cyclization, and finally, benzene, toluene and heavier PAH formation. Experimental results to date show general qualitative agreement to computational models. However, it is clear that molecular growth mechanisms found to be unimportant at the high temperatures generally associated with combustion can play a significant role in fuel systems.

scholarly journals Implementation of kinetic mechanisms of methane combustion by example of expanding functionality of physicochemical libraries in conjunction with reactingPimpleCentralFoam solver

2021 ◽  
Vol 33 (5) ◽  
pp. 271-280
Author(s):  
Dmitry Sergeevich Kononov ◽  
Vladimir Yurevich Gidaspov ◽  
Sergei Vladimirovich Strijhak
Keyword(s):  
Shock Wave ◽  
Test Problem ◽  
Three Dimensional ◽  
Methane Combustion ◽  
Reflected Shock Wave ◽  
Computational Domain ◽  
Moscow Aviation Institute ◽  
Reflected Shock ◽  
Reduced Mechanism ◽  
Kinetic Mechanisms

The possibility of using reduced combustion mechanisms for hydrocarbon fuels in solvers developed and used at ISP RAS is investigated. These mechanisms contain smaller number of stages and substances appearing in them, but they allow obtaining results in a good agreement with experimental data in a much shorter calculation time. The comparison is made with the results obtained with using the Moscow Aviation Institute solvers. A modified mechanism of methane combustion is considered. It can be extended to describe the chemical reaction processes in other hydrocarbon-oxygen mixtures. The choice of methane is due to the prospects of this fuel at the present time. As the first test problem, a standard chemFoam is used. This solver was designed to demonstrate the occurrence of chemical reactions in a computational domain consists of one cell only. The ignition delay and the parameter values of the thermodynamic equilibrium state reached are taken as the comparison criteria. The second test problem is the flow modeling in a shock tube after the shock wave has been reflected from the wall. This problem is considered in a three-dimensional domain using the ISP RAS reactingPimpleCentralFoam solver. Results were compared with ones obtained by grid-characteristic and Godunov's methods in one-dimensional nonstationary calculations. The effects of viscosity, thermal conductivity and diffusion are not taken into account. The distributions of the flow parameters behind the reflected shock wave are obtained. Results are analyzed depending on the value of the falling shock wave Mach number. Estimates of the possible application of this reduced mechanism are given.

scholarly journals Conversion of Oxygenates on H-ZSM-5 Zeolites—Effects of Feed Structure and Si/Al Ratio on the Product Quality

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 432
Author(s):  
Torsten Gille ◽  
Markus Seifert ◽  
Mathias S. Marschall ◽  
Sascha Bredow ◽  
Tobias Schneider ◽  
...  
Keyword(s):  
Reaction Network ◽  
Product Distribution ◽  
Zeolite Catalysts ◽  
Primary Alcohols ◽  
Reaction Sequence ◽  
Al Content ◽  
Multi Stage ◽  
Flexible Adaptation ◽  
The Relationship ◽  
Subsequent Integration

The conversion of different biogenic feedstocks to hydrocarbons is a major challenge when ensuring hydrocarbon and fuel supply in spite of the heterogeneity of this feed. Flexible adaptation to changing compositions is mandatory for the respective processes. In this study, different oxygenate model feeds, such as alcohols, aldehydes, carboxylic acids and esters, were converted at 500 °C and 5 barg H2 using H-ZSM-5 zeolite catalysts with various Si/Al ratios to identify the relationship between the feed structure and the final product distribution. As the main outcome, the product distribution becomes increasingly independent of the feed structure for Al-rich H-ZSM-5 catalyst samples at low Time on Stream (ToS). Some minor exceptions are the increased formation of aromatics during ToS for carbonyl oxygenates compared to primary alcohols and the dominance of initial deoxygenation products for Si-rich H-ZSM-5 samples. This is interpreted by a multi-stage reaction sequence, which involves the initial deoxygenation of the feed and the subsequent integration of the olefin intermediates into a reaction network. The results pave the way towards the achievement of a desired product distribution in the conversion of different oxygenates simply by the adaption of the Al content of H-ZSM-5.

scholarly journals Development of Air Toxic Emission Factor and Inventory of On-road Mobile Sources

2014 ◽  
Vol 7 ◽  
pp. ASWR.S13320 ◽  
Author(s):  
P. Outapa ◽  
S. Thepanondh
Keyword(s):  
Natural Gas ◽  
Public Transportation ◽  
Alternative Fuels ◽  
Control Policy ◽  
Emission Factors ◽  
Transportation Systems ◽  
Mitigation Measures ◽  
Fuel Quality ◽  
Toxic Emission ◽  
Public Transportation Systems

Dynamic emission factors of air toxic compounds, emitted from vehicles in Bangkok, Thailand, are developed using the IVE model. The model takes into account the actual fleet and characteristics of vehicles in the study area. It is found that the calculated emission factors are greatly influenced by vehicle emission control policy. Approximately 2000 tons of benzene emission per year is reduced by the changing of fuel quality from Euro 2 to Euro 4 standards. As for mitigation measures, introduction of gasohol and natural gas as alternative fuels, as well as encouraging the utilization of public transportation systems, are analyzed. The outcomes reveal that a combined scenario using 100% gasohol plus decreasing vehicle kilometers traveled (VKT) by 20% is the most effective in reduction of benzene emission. In addition, 1,3-butadiene, acetaldehyde and formaldehyde emissions are greatly decreased by the combined scenario of using compressed natural gas (CNG) plus decreasing VKT by 20%.

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