A Study of Interactions between Mixing and Chemical Reaction Using the Rate-Controlled Constrained-Equilibrium Method

2016 ◽  
Vol 41 (4) ◽  
Author(s):  
Fatemeh Hadi ◽  
Mohammad Janbozorgi ◽  
M. Reza H. Sheikhi ◽  
Hameed Metghalchi
Keyword(s):  
Chemical Kinetics ◽  
Chemical Reaction ◽  
Computational Cost ◽  
Methane Combustion ◽  
Rate Equations ◽  
Wide Range ◽  
Constrained Equilibrium ◽  
Rate Controlled ◽  
Detailed Kinetics ◽  
Reacting Systems

AbstractThe rate-controlled constrained-equilibrium (RCCE) method is employed to study the interactions between mixing and chemical reaction. Considering that mixing can influence the RCCE state, the key objective is to assess the accuracy and numerical performance of the method in simulations involving both reaction and mixing. The RCCE formulation includes rate equations for constraint potentials, density and temperature, which allows taking account of mixing alongside chemical reaction without splitting. The RCCE is a dimension reduction method for chemical kinetics based on thermodynamics laws. It describes the time evolution of reacting systems using a series of constrained-equilibrium states determined by RCCE constraints. The full chemical composition at each state is obtained by maximizing the entropy subject to the instantaneous values of the constraints. The RCCE is applied to a spatially homogeneous constant pressure partially stirred reactor (PaSR) involving methane combustion in oxygen. Simulations are carried out over a wide range of initial temperatures and equivalence ratios. The chemical kinetics, comprised of 29 species and 133 reaction steps, is represented by 12 RCCE constraints. The RCCE predictions are compared with those obtained by direct integration of the same kinetics, termed detailed kinetics model (DKM). The RCCE shows accurate prediction of combustion in PaSR with different mixing intensities. The method also demonstrates reduced numerical stiffness and overall computational cost compared to DKM.

Constrained-Equilibrium Modeling of Methane Oxidation in Air

2013 ◽  
Author(s):  
Ghassan Nicolas ◽  
Mohammad Janbozorgi ◽  
Hameed Metghalchi
Keyword(s):  
Combustion Process ◽  
Rate Equations ◽  
Experimental Measurements ◽  
Combustion Modeling ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Constrained Equilibrium ◽  
Detailed Kinetic Model ◽  
Rate Controlled ◽  
Oxidation In Air

The Rate-Controlled Constrained-Equilibrium (RCCE) has been further developed and applied to model methane/air combustion process. The RCCE method is based on local maximization of entropy or minimization of a relevant free energy at any time during the non-equilibrium evolution of the system subject to a set of constraints. The constraints are imposed by slow rate-limiting reactions. Direct integration of the rate equations for the constraint potentials has been employed. Once the values of the potentials are obtained, the concentration of all species can be calculated. A set of constraints has been developed for methane/air mixtures in the method of Rate-Controlled Constrained-Equilibrium (RCCE). The model predicts the ignition delay times, which have been compared to those predicted by detailed kinetic model (DKM) and with shock tube experimental measurements. The DKM includes 60 H/O/C1–2/N species and 352 reactions. The RCCE model using 16 constraints has been applied for combustion modeling in a wide range of initial temperatures (900–1200 K), pressures (1–50 atmospheres) and fuel-air equivalence ratio (0.6–1.2). The predicted results of using RCCE are within 5% of those of DKM model and are in excellent agreement with experimental measurements in shock tubes.

A Comparison of Rate-Controlled Constrained-Equilibrium Formulations

2015 ◽  
Author(s):  
Fatemeh Hadi ◽  
Mohammad Janbozorgi ◽  
M. Reza H. Sheikhi
Keyword(s):  
Performance Studies ◽  
Turbulent Combustion ◽  
Gas Mixtures ◽  
Direct Integration ◽  
Stirred Reactor ◽  
Wide Range ◽  
Constrained Equilibrium ◽  
Rate Controlled ◽  
And Performance ◽  
Detailed Kinetics

In this study, constraint potential and constraint forms of the Rate-Controlled Constrained-Equilibrium (RCCE) method have been investigated in terms of accuracy and performance. Although the two formulations are equivalent mathematically, they show quite different performances from the computational standpoint. The main objective of this work is to determine the most efficient implementation of RCCE to be used in turbulent combustion simulations. Simulations are conducted of an adiabatic, isobaric stirred reactor. The kinetics includes methane oxygen combustion using 133 reaction steps and 29 species. RCCE calculations are performed by 12 constraints. The simulations are carried out over a wide range of initial temperatures for stoichiometric gas mixtures. Performance studies of the two RCCE formulations are carried out and the results are compared with those obtained by direct integration of detailed kinetics.

Combustion Simulation of Propane/Oxygen (With Nitrogen/Argon) Mixtures Using Rate-Controlled Constrained-Equilibrium

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Guangying Yu ◽  
Hameed Metghalchi ◽  
Omid Askari ◽  
Ziyu Wang
Keyword(s):  
Experimental Data ◽  
Energy System ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Oxygen Mixture ◽  
Free Valence ◽  
Wide Range ◽  
Constrained Equilibrium ◽  
Rate Controlled ◽  
Good Agreement

The rate-controlled constrained-equilibrium (RCCE), a model order reduction method, has been further developed to simulate the combustion of propane/oxygen mixture diluted with nitrogen or argon. The RCCE method assumes that the nonequilibrium states of a system can be described by a sequence of constrained-equilibrium states subject to a small number of constraints. The developed new RCCE approach is applied to the oxidation of propane in a constant volume, constant internal energy system over a wide range of initial temperatures and pressures. The USC-Mech II (109 species and 781 reactions, without nitrogen chemistry) is chosen as chemical kinetic mechanism for propane oxidation for both detailed kinetic model (DKM) and RCCE method. The derivation for constraints of propane/oxygen mixture starts from the eight universal constraints for carbon-fuel oxidation. The universal constraints are the elements (C, H, O), number of moles, free valence, free oxygen, fuel, and fuel radicals. The full set of constraints contains eight universal constraints and seven additional constraints. The results of RCCE method are compared with the results of DKM to verify the effectiveness of constraints and the efficiency of RCCE. The RCCE results show good agreement with DKM results under different initial temperature and pressures, and RCCE also reduces at least 60% CPU time. Further validation is made by comparing the experimental data; RCCE shows good agreement with shock tube experimental data.

I.—The Action of “Active” Nitrogen on Iodine Vapour

1929 ◽  
Vol 48 ◽  
pp. 1-9
Author(s):  
L. H. Easson ◽  
R. W. Armour
Keyword(s):  
Chemical Kinetics ◽  
Chemical Reaction ◽  
Electronic Energy ◽  
Chemical Investigation ◽  
Rapid Progress ◽  
Active Nitrogen ◽  
Spectroscopic Observations ◽  
Wide Range ◽  
Band Spectra ◽  
Made In

The rapid progress which has been made in the last few years in the knowledge of the rotational, vibrational, and electronic energy of molecules has extended the range of chemical investigation, particularly in the region of chemical kinetics. This knowledge is derived chiefly from the study and interpretation of band spectra, and one of the most obvious cases to examine is that of “active” nitrogen which emits a characteristic spectrum and is capable of energetic chemical reaction with a wide range of substances. For most of the early work, including spectroscopic observations, we are indebted to the excellent and thorough investigations of Strutt.

Constrained-Equilibrium Modeling of Methane Oxidation in Air

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Ghassan Nicolas ◽  
Mohammad Janbozorgi ◽  
Hameed Metghalchi
Keyword(s):  
Kinetic Model ◽  
Ignition Delay ◽  
Combustion Process ◽  
Rate Equations ◽  
Time Step ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Delay Times ◽  
Constrained Equilibrium ◽  
Detailed Kinetic Model

Rate-controlled constrained-equilibrium method has been further developed to model methane/air combustion. A set of constraints has been identified to predict the nonequilibrium evolution of the combustion process. The set predicts the ignition delay times of the corresponding detailed kinetic model to within 10% of accuracy over a wide range of initial temperatures (900 K–1200 K), initial pressures (1 atm–50 atm) and equivalence ratios (0.6–1.2). It also predicts the experimental shock tube ignition delay times favorably well. Direct integration of the rate equations for the constraint potentials has been employed. Once the values of the potentials are obtained, the concentration of all species can be calculated. The underlying detailed kinetic model involves 352 reactions among 60 H/O/N/C1-2 species, hence 60 rate equations, while the RCCE calculations involve 16 total constraints, thus 16 total rate equations. Nonetheless, the constrained-equilibrium concentrations of all 60 species are calculated at any time step subject to the 16 constraints.

Rate-Controlled Constrained-Equilibrium Calculations of Ethanol-Oxygen Mixture

2006 ◽  
Author(s):  
Mohammad Janbozorgi ◽  
Yue Gao ◽  
Hameed Metghalchi ◽  
James C. Keck
Keyword(s):  
Chemical Reactions ◽  
Initial Pressure ◽  
Kinetic Scheme ◽  
Rate Equations ◽  
Oxygen Mixture ◽  
Free Valence ◽  
Free Oxygen ◽  
Constant Volume Chamber ◽  
Constrained Equilibrium ◽  
Rate Controlled

The Rate-Controlled Constrained-Equilibrium method (RCCE) is a powerful technique for simplifying the treatment of chemical reactions in complex systems. The method is based on the assumption that slow chemical reactions impose constraints on the allowed composition of such systems. Since the number of constraints can be very much smaller than the number of species, the number of rate equations to be integrated can be considerably reduced. In the present work, a kinetic scheme with 55 species and 366 reactions has been used to investigate stoichiometric Ethanol-oxygen mixture in a constant energy constant volume chamber. The state of the system was determined by three fixed elemental constraints: elemental carbon, elemental oxygen and elemental hydrogen and six variable constraints: moles of fuel, moles of fuel radicals, total number of moles, moles of free valence, moles of free oxygen, moles of OH+O+H. The 9 rate equations for the constraint potentials (LaGrange multipliers associated with the constraints) were integrated over a range of 1400 K-1700 K for initial temperature and 1atm-10atm for initial pressure. The RCCE calculations were in good agreement with detailed calculations and were faster than detailed calculations, which required integration of 55 species rate equations.

Analysis of chemical reaction systems by means of network thermodynamics

1989 ◽  
Vol 54 (9) ◽  
pp. 2335-2344
Author(s):  
José Horno ◽  
Carlos F. González-Fernández
Keyword(s):  
Steady State ◽  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reaction Rates ◽  
Rate Equations ◽  
Mathematical Treatment ◽  
Reaction Systems ◽  
Chemical Reaction Systems ◽  
Simple Network

The simple network thermodynamics approach is applied to chemical reaction systems, whereby chemical reactions can be studied avoiding complex mathematical treatment. Steady state reaction rates are obtained for two chemical reaction systems, viz. the decomposition of ozone and the reaction of hydrogen with bromine. The rate equations so obtained agree with those derived from the chemical kinetics concept.

scholarly journals Evaluation of Chemical Kinetic Mechanisms for Methane Combustion: A Review from a CFD Perspective

Fuels ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 210-240
Author(s):  
Niklas Zettervall ◽  
Christer Fureby ◽  
Elna J. K. Nilsson
Keyword(s):  
Model Development ◽  
Computational Cost ◽  
Informed Choice ◽  
Methane Combustion ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Cfd Modeling ◽  
Computational Time ◽  
Wide Range ◽  
Kinetic Mechanisms

Methane is an important fuel for gas turbine and gas engine combustion, and the most common fuel in fundamental combustion studies. As Computational Fluid Dynamics (CFD) modeling of combustion becomes increasingly important, so do chemical kinetic mechanisms for methane combustion. Kinetic mechanisms of different complexity exist, and the aim of this study is to review commonly used detailed, reduced, and global mechanisms of importance for CFD of methane combustion. In this review, procedures of relevance to model development are outlined. Simulations of zero and one-dimensional configurations have been performed over a wide range of conditions, including addition of H2, CO2 and H2O, and the results are used in a final recommendation about the use of the different mechanisms. The aim of this review is to put focus on the importance of an informed choice of kinetic mechanism to obtain accurate results at a reasonable computational cost. It is shown that for flame simulations, a reduced mechanism with only 42 irreversible reactions gives excellent agreement with experimental data, using only 5% of the computational time as compared to the widely used GRI-Mech 3.0. The reduced mechanisms are highly suitable for flame simulations, while for ignition they tend to react too slow, giving longer than expected ignition delay time. For combustible mixtures with addition of hydrogen, carbon dioxide, or water, the detailed as well as reduced mechanisms generally show as good performance as for the corresponding simulations of pure methane/air mixtures.

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