Extending Degree of Disequilibrium Analysis for Automatic Selection of Kinetic Constraints in the Rate-Controlled Constrained-Equilibrium Method

2018 ◽  
Author(s):  
Fatemeh Hadi ◽  
Vreg Yousefian ◽  
Ehsan Sarfaraz ◽  
Gian Paolo Beretta
Keyword(s):  
Initial Conditions ◽  
Equilibrium States ◽  
Chemical System ◽  
Accurate Identification ◽  
Constrained Equilibrium ◽  
Thermodynamic Conditions ◽  
Detailed Kinetic Model ◽  
Rate Controlled ◽  
The Individual ◽  
Value Decomposition

The Rate-Controlled Constrained-Equilibrium (RCCE) is a model reduction scheme for chemical kinetics. It describes the evolution of a complex chemical system with acceptable accuracy with a number of rate controlling constraints on the associated constrained-equilibrium states of the system, much lower than the number of species in the underlying Detailed Kinetic Model (DKM). Successful approximation of the constrained-equilibrium states requires accurate identification of the constraints. One promising procedure is the fully automatable Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. ASVDADD is based on simple algebraic analysis of the results of the underlying DKM simulation and is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. In this paper, we propose a method, as part of our work-in-progress efforts, that could expand the applicability of the derived constraints. This method involves running DKM calculations for a wider range of initial conditions, appending the results of all these cases one after the other after normalizing, and finally running the ASVDADD method to get a set of ‘universal’ constraints applicable within that range of conditions. The effectiveness and robustness of the derived constraints is examined in hydrogen/oxygen ignition delay simulations and the results are compared with those obtained from DKM. The proof-of-concept results demonstrate the potential of the method for finding ‘universal’ constraints.

A Reformulation of Degree of Disequilibrium Analysis for Automatic Selection of Kinetic Constraints in the Rate-Controlled Constrained-Equilibrium Method

2021 ◽  
pp. 1-25
Author(s):  
Fatemeh Hadi ◽  
Shrabanti Roy ◽  
Omid Askari ◽  
Gian Paolo Beretta
Keyword(s):  
Chemical Species ◽  
Equilibrium States ◽  
Chemical System ◽  
Accurate Identification ◽  
Linearly Independent ◽  
Constrained Equilibrium ◽  
Thermodynamic Conditions ◽  
Rate Controlled ◽  
The Individual ◽  
Value Decomposition

Abstract The Rate-Controlled Constrained-Equilibrium (RCCE) is a model reduction scheme for chemical kinetics. It describes the evolution of a complex chemical system with acceptable accuracy with a number of rate controlling constraints on the associated constrained-equilibrium states of the system, much lower than the number of species in the underlying Detailed Kinetic Model (DKM). Successful approximation of the constrained-equilibrium states requires accurate identification of the constraints. One promising procedure is the fully automatable Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. ASVDADD is based on simple algebraic analysis of the results of the underlying DKM simulation and is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. In this paper, we introduce an alternative ASVDADD algorithm. Unlike the original ASVDADD algorithm that require the direct computation of the DKM-derived DoDs and the identification of the set of linearly independent reactions, in the alternative algorithm, the components of the overall degree of disequilibrium vector can be computed directly by casting the DKM as an RCCE simulation considering a set of linearly independent constraints equalling the number of chemical species in size. The effectiveness and robustness of the derived constraints from the alternative procedure is examined in hydrogen/oxygen and methane/oxygen ignition delay simulations and the results are compared with those obtained from DKM.

Validation of the ASVDADD Constraint Selection Algorithm for Effective RCCE Modeling of Natural Gas Ignition in Air

2016 ◽  
Author(s):  
Luca Rivadossi ◽  
Gian Paolo Beretta
Keyword(s):  
Natural Gas ◽  
Accurate Identification ◽  
Thermodynamic Conditions ◽  
Gas Ignition ◽  
Detailed Kinetic Model ◽  
Rate Controlled ◽  
The Individual ◽  
Value Decomposition ◽  
Constraint Selection ◽  
Hydrocarbon Ignition

The Rate-Controlled Constrained-Equilibrium (RCCE) model reduction scheme for chemical kinetics provides acceptable accuracies in predicting hydrocarbon ignition delays by solving a smaller number of differential equations than the number of species in the underlying Detailed Kinetic Model (DKM). To yield good approximations, the method requires accurate identification of the rate controlling constraints. Until recently, a drawback of the RCCE scheme has been the absence of a fully automatable and systematic procedure capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. A recent paper [1] has proposed a new methodology for such identification based on a simple algebraic analysis of the results of a preliminary simulation of the underlying DKM, focused on the behaviour of the degrees of disequilibrium (DoD) of the individual chemical reactions. The new methodology is based on computing an Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) obtained from the DKM simulation. The effectiveness and robustness of the method has been demonstrated in [1] for some cases of methane/oxygen ignition by considering a C1/H/O (29 species/133 reactions) sub-mechanism of the GRI-Mech 3.0 scheme and comparing the results of a DKM simulation with those of RCCE simulations based on increasing numbers of ASVDADD constraints. The RCCE results are in excellent agreement with DKM predictions for relatively small numbers of RCCE constraints. Here we provide a demonstration of the new method for some cases of shock-tube ignition of a natural gas/air mixture, with higher hydrocarbons approximately represented by propane according to the full (53 species/325 reactions) GRI-Mech 3.0 scheme.

Validation of the ASVDADD Constraint Selection Algorithm for Effective RCCE Modeling of Natural Gas Ignition in Air

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
Luca Rivadossi ◽  
Gian Paolo Beretta
Keyword(s):  
Natural Gas ◽  
Nox Formation ◽  
Accurate Identification ◽  
Thermodynamic Conditions ◽  
Gas Ignition ◽  
Detailed Kinetic Model ◽  
The Individual ◽  
Value Decomposition ◽  
Constraint Selection ◽  
Hydrocarbon Ignition

The rate-controlled constrained-equilibrium (RCCE) model reduction scheme for chemical kinetics provides acceptable accuracies in predicting hydrocarbon ignition delays by solving a smaller number of differential equations than the number of species in the underlying detailed kinetic model (DKM). To yield good approximations, the method requires accurate identification of the rate controlling constraints. Until recently, a drawback of the RCCE scheme has been the absence of a systematic procedure capable of identifying optimal constraints for a given range of thermodynamic conditions and a required level of approximation. A recent methodology has proposed for such identification an algorithm based on a simple algebraic analysis of the results of a preliminary simulation of the underlying DKM, focused on the degrees of disequilibrium (DoD) of the individual chemical reactions. It is based on computing an approximate singular value decomposition of the actual degrees of disequilibrium (ASVDADD) obtained from the DKM simulation. The effectiveness and robustness of the method have been demonstrated for methane/oxygen ignition by considering a C1/H/O (29 species/133 reactions) submechanism of the GRI-Mech 3.0 scheme and comparing the results of a DKM simulation with those of RCCE simulations based on increasing numbers of ASVDADD constraints. Here, we demonstrate the new method for shock-tube ignition of a natural gas/air mixture, with higher hydrocarbons approximately represented by propane according to the full (53 species/325 reactions) GRI-Mech 3.0 scheme including NOx formation.

Rate Controlled Constrained-Equilibrium Simulation of Ethanol Combustion Using SVD Derived Constraints

2019 ◽  
Author(s):  
Shrabanti Roy ◽  
Fatemeh Hadi ◽  
Omid Askari
Keyword(s):  
Chemical Reactions ◽  
Fluid Dynamic ◽  
Equilibrium States ◽  
Chemical System ◽  
Accurate Identification ◽  
Combustion Modeling ◽  
Number Of Species ◽  
Constrained Equilibrium ◽  
Ethanol Combustion ◽  
Rate Controlled

Abstract In this study, the fully automatable Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method is used for combustion modeling of ethanol. Due to the importance of ethanol as one of the most common type of biofuels, modeling its reaction kinetics and chemical composition evolution during combustion is necessary. The detailed kinetic mechanism (DKM) considered here is generated by authors using reaction mechanism generator (RMG) technique and it consists of 66 species and 1031 reactions. Tracking this number of species and chemical reactions in computational fluid dynamic (CFD) analysis of engineering problems is prohibitive. To alleviate this issue, Rate-Controlled Constrained-Equilibrium (RCCE) model reduction scheme for chemical kinetics is employed. It describes the evolution of a complex chemical system with acceptable accuracy with a number of rates controlling constraints on the associated constrained-equilibrium states of the system, much lower than the number of species in the underlying DKM. Successful approximation of the constrained equilibrium states requires accurate identification of the constraints. One promising procedure is the ASVDADD method that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. ASVDADD is based on simple algebraic analysis of the results of the underlying DKM simulation and is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. In this paper, ASVDADD is used to derive the RCCE constraints and ethanol combustion is modeled using both DKM and RCCE. Comparison of RCCE results with those of DKM shows the effectiveness of the ASVDADD derived constraints which demonstrates the potential of the RCCE method for combustion modeling of heavy and complex fuels.

Study of the Constraint Selection Through ASVDADD Method for Rate-Controlled Constrained-Equilibrium Modeling on Ethanol Oxidation Without PLOG Reactions

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Shrabanti Roy ◽  
Omid Askari
Keyword(s):  
Ethanol Oxidation ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Kinetic Mechanism ◽  
Optimal Level ◽  
Chemical Kinetic ◽  
Constrained Equilibrium ◽  
Rate Controlled ◽  
The Individual ◽  
Value Decomposition

Abstract Reduction of the detail chemical kinetic mechanism is important in solving complex combustion simulation. In this work, a model reduction scheme rate-controlled constrained-equilibrium (RCCE) is considered in predicting the oxidation of ethanol. A detail kinetic mechanism by Merinov from Lawrence Livermore National Laboratory (LLNL) is used in modeling this reduction technique. The RCCE method considers constrained equilibrium states which subjected to a lower number of constraints compared to the number of species. It then has to solve a smaller number of differential equations compared to the number of equations required in solving the detailed kinetic model (DKM). The accuracy of this solution depends on the selection of the constraint. A systematic procedure which will help in identifying the constraint at an optimal level of accuracy is an essential for RCCE modeling. A fully automated Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method is used in this study to derive the constraint for RCCE simulation. ASVDADD uses an algorithm which follows the simple algebraic analysis on results of underlying DKM to find the degree of disequilibrium (DoD) of the individual chemical reactions. The number of constraints which will be used in RCCE simulation can be selected to reduce the number of equations required to solve. In the current work, this ASVDADD method is applied on ethanol oxidation to select the constraint for RCCE simulation. Both DKM and RCCE calculations on ethanol fuel are demonstrated to compare the result of temperature distribution and an ignition delay time for validating the method.

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.

Review of Applications of Rate-Controlled Constrained-Equilibrium in Combustion Modeling

2020 ◽  
Vol 45 (1) ◽  
pp. 59-79 ◽  
Author(s):  
Guangying Yu ◽  
Fatemeh Hadi ◽  
Ziyu Wang ◽  
Hameed Metghalchi
Keyword(s):  
Equilibrium State ◽  
Order Reduction ◽  
Second Law Of Thermodynamics ◽  
Equilibrium States ◽  
Computational Time ◽  
Thermodynamic Quantities ◽  
Constrained Equilibrium ◽  
Rate Controlled ◽  
Order Reduction Method ◽  
Non Equilibrium

AbstractDeveloping an effective model for non-equilibrium states is of great importance for a variety of problems related to chemical synthesis and combustion. Rate-Controlled Constrained-Equilibrium (RCCE), a model order reduction method that originated from the second law of thermodynamics, assumes that the non-equilibrium states of a system can be described by a sequence of constrained-equilibrium states kinetically controlled by a relatively small number of constraints within acceptable accuracy. The full chemical composition at each constrained-equilibrium state is obtained by maximizing (or minimizing) the appropriate thermodynamic quantities, e. g., entropy (or Gibbs functions), subject to the instantaneous values of RCCE constraints. Regardless of the nature of the kinetic constraints, RCCE always guarantees a correct final equilibrium state. This paper reviews the fundamentals of the RCCE method, its constraints, constraint potential formulations, and major constraint selection techniques, as well as the application of the RCCE method to combustion of different fuels using a variety of combustion models. The RCCE method has been proven to be accurate and to reduce computational time in these simulations.

scholarly journals Crystal growth of clathrate hydrate formed with H2 + CO2 mixed gas and tetrahydropyran

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Meku Maruyama ◽  
Riku Matsuura ◽  
Ryo Ohmura
Keyword(s):  
Crystal Growth ◽  
Synthesis Gas ◽  
Water System ◽  
Hydrate Formation ◽  
Growth Dynamics ◽  
Operating Conditions ◽  
Mixed Gas ◽  
Thermodynamic Conditions ◽  
The Individual ◽  
And Storage

AbstractHydrate-based gas separation technology is applicable to the CO2 capture and storage from synthesis gas mixture generated through gasification of fuel sources including biomass. This paper reports visual observations of crystal growth dynamics and crystal morphology of hydrate formed in the H2 + CO2 + tetrahydropyran (THP) + water system with a target for developing the hydrate-based CO2 separation process design. Experiments were conducted at a temperature range of 279.5–284.9 K under the pressure of 4.9–5.3 MPa. To simulate the synthesis gas, gas composition in the gas phase was maintained around H2:CO2 = 0.6:0.4 in mole fraction. Hydrate crystals were formed and extended along the THP/water interface. After the complete coverage of the interface to shape a polycrystalline shell, hydrate crystals continued to grow further into the bulk of liquid water. The individual crystals were identified as hexagonal, tetragonal and other polygonal-shaped formations. The crystal growth rate and the crystal size varied depending on thermodynamic conditions. Implications from the obtained results for the arrangement of operating conditions at the hydrate formation-, transportation-, and dissociation processes are discussed.

scholarly journals Development of dynamic system response curve method for estimating initial conditions of conceptual hydrological models

2018 ◽  
Vol 20 (6) ◽  
pp. 1387-1400
Author(s):  
Yiqun Sun ◽  
Weimin Bao ◽  
Peng Jiang ◽  
Xuying Wang ◽  
Chengmin He ◽  
...  
Keyword(s):  
Dynamic System ◽  
Response Curve ◽  
Initial Conditions ◽  
Model Performance ◽  
System Response ◽  
Hydrological Models ◽  
Flood Prediction ◽  
Ill Posed ◽  
Value Decomposition

Abstract The dynamic system response curve (DSRC) has its origin in correcting model variables of hydrologic models to improve the accuracy of flood prediction. The DSRC method can lead to unstable performance since the least squares (LS) method, employed by DSRC to estimate the errors, often breaks down for ill-posed problems. A previous study has shown that under certain assumptions the DSRC method can be regarded as a specific form of the numerical solution of the Fredholm equation of the first kind, which is a typical ill-posed problem. This paper introduces the truncated singular value decomposition (TSVD) to propose an improved version of the DSRC method (TSVD-DSRC). The proposed method is extended to correct the initial conditions of a conceptual hydrological model. The usefulness of the proposed method is first demonstrated via a synthetic case study where both the perturbed initial conditions, the true initial conditions, and the corrected initial conditions are precisely known. Then the proposed method is used in two real basins. The results measured by two different criteria clearly demonstrate that correcting the initial conditions of hydrological models has significantly improved the model performance. Similar good results are obtained for the real case study.

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.

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