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.

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.

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.

Predicting the Physical and Chemical Ignition Delays in a Military Diesel Engine Running n-Hexadecane Fuel

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Len Hamilton ◽  
Dianne Luning Prak ◽  
Jim Cowart
Keyword(s):  
Diesel Engine ◽  
Ignition Delay ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Combustible Mixture ◽  
Load Range ◽  
Modeling Tools ◽  
Start Of Injection

There are currently numerous efforts to create renewable fuels that have similar properties to conventional diesel fuels. One major future challenge is evaluating how these new fuels will function in older legacy diesel engines. It is desired to have physically based modeling tools that will predict new fuel performance without extensive full scale engine testing. This study evaluates two modeling tools that are used together to predict ignition delay in a military diesel engine running n-hexadecane as a fuel across the engine's speed-load range. AVL-FIRE® is used to predict the physical delay of the fuel from the start of injection until the formation of a combustible mixture. Then a detailed Lawrence Livermore National Laboratory (LLNL) chemical kinetic mechanism is used to predict the chemical ignition delay. This total model predicted ignition delay is then compared to the experimental engine data. The combined model predicted results show good agreement to that of the experimental data across the engine operating range with the chemical delay being a larger fraction of the total ignition delay. This study shows that predictive tools have the potential to evaluate new fuel combustion performance.

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.

scholarly journals Five-dimensional crystallography

2010 ◽  
Vol 66 (2) ◽  
pp. 198-206 ◽  
Author(s):  
Marius Schmidt ◽  
Tim Graber ◽  
Robert Henning ◽  
Vukica Srajer
Keyword(s):  
Time Series ◽  
Relaxation Times ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Photoactive Yellow Protein ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
First Results ◽  
Two Temperatures ◽  
Value Decomposition

A method for determining a comprehensive chemical kinetic mechanism in macromolecular reactions is presented. The method is based on five-dimensional crystallography, where, in addition to space and time, temperature is also taken into consideration and an analysis based on singular value decomposition is applied. First results of such a time-resolved crystallographic study are presented. Temperature-dependent time-resolved X-ray diffraction measurements were conducted on the newly upgraded BioCARS 14-ID-B beamline at the Advanced Photon Source and aimed at elucidating a comprehensive kinetic mechanism of the photoactive yellow protein photocycle. Extensive time series of crystallographic data were collected at two temperatures, 293 K and 303 K. Relaxation times of the reaction extracted from these time series exhibit measurable differences for the two temperatures, hence demonstrating that five-dimensional crystallography is feasible.

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.

NUMERICAL SIMULATION FOR REDUCED CHEMICAL KINETIC MECHANISM: A CASE FOR CARBON MONOXIDE AND HYDROGEN

2018 ◽  
Author(s):  
Rafael Torres Teixeira ◽  
Rafaela Sehnem ◽  
Letícia Kaufmann ◽  
Daniela Buske ◽  
Regis Sperotto de Quadros
Keyword(s):  
Numerical Simulation ◽  
Carbon Monoxide ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Chemical Kinetic Mechanism
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