A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the fu...A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the full mechanism using sensitivity analysis,reaction path analysis and quasi steady state(QSS) approximation. The model in premixed flame was validated and with computing savings in diffusion flame was applied by incor-porating into a CFD code. Simulations were performed to explore the effect of coflow air on flame structure and soot formation. Thermal radiation was calculated by a discrete-ordinates method,and soot formation was predicted by a simple two-equation soot model. Model results are in good agreement with those from experiment data and detailed mechanism at atmospheric conditions. The soot nucleation,growth,and oxidation by OH are all enhanced by decrease in coflow air velocity. The peak soot volume fraction region appears in the lower annular region be-tween the peak flame temperature and peak acetylene concentration locations,and the high soot oxidation rate due to the OH attack occurs in the middle annular region because of high temperature.展开更多
Thrombotic disease is a major problem that endangers human health. At present, MRI and CT are commonly used clinically to diagnose thrombosis, and thrombolytic drugs are used for treatment), but the diagnosis time is ...Thrombotic disease is a major problem that endangers human health. At present, MRI and CT are commonly used clinically to diagnose thrombosis, and thrombolytic drugs are used for treatment), but the diagnosis time is lagging, the utilization of drugs is low, and the resulting systemic toxicity problems such as side effects lead to poor treatment effects. Nanotechnology combining photoacoustic dynamics and chemical dynamics has shown great application value in tumor targeting, diagnosis, detection and treatment. It has also become a new direction in the diagnosis and treatment of thrombotic diseases, and has created new applications in the field of nanomaterials. This review summarizes the new progress of this combination in the diagnosis and treatment of thrombotic diseases according to the differences in the construction of the nanotherapy system, at the same time, we put forward some new problems and prospects for the integration of thrombosis diagnosis and treatment.展开更多
A package(a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matri...A package(a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matrix technology to chemical kinetics is included in the tool model, it is only necessary to triangularize the matrix related to the Jacobian matrix of the model equation. The Gear type procedure is used to integrate a model equation and its coupled auxiliary sensitivity coefficient equations. The FORTRAN subroutines of the model equation, the sensitivity coefficient equations, and their Jacobian analytical expressions are generated automatically from a chemical mechanism. The kinetic representation for the model equation and its sensitivity coefficient equations, and their Jacobian matrix is presented. Various FORTRAN subroutines in packages, such as SLODE, modified MA28, Gear package, with which the program runs in conjunction are recommended. The photo\|oxidation of dimethyl disulfide is used for illustration.展开更多
A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accompli...A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.展开更多
An explicit expression for local, instantaneous NO production rate model was proposed to simulate NO formation in turbulent methane-air combustion. The average production rates of mixture fraction and scalar dissipati...An explicit expression for local, instantaneous NO production rate model was proposed to simulate NO formation in turbulent methane-air combustion. The average production rates of mixture fraction and scalar dissipation were obtained from asymptotes through approximation of two single-variable probability-density function. The theory predicted significant contributions from the Zeldovich mechanism, but negligible contributions from the nitrous-oxide mechanism in the oxygenconsumption zone. The proposed model was used to simulate NO formation in the pilot methane-air jet diffusion combustion. The simulation results were compared with those obtained by the CFD software FLUENT module. Validation of predictions with the experimental data given by Sandia National Laboratory of the USA indicates that the proposed model yields better results than other models, and the deviation is under 5%. And in some complete reaction zones, the simulation results are even the same as the experimental data. Realizable κ-ε model, Reynold stress model and standard κ-ε model were also investigated to predict the turbulent combustion reaction, which shows that the simulation results of velocities, temperatures, and concentrations of combustion productions by standard κ-ε model are in accordance with the experimental data.展开更多
In this work,a calculation method of chemical kinetics was established for labeling reaction of 99mTc-N-ethyl-N_(2)S_(2)-memantine,a potential NMDA receptor imaging agent prepared in our laboratory.Four groups of vial...In this work,a calculation method of chemical kinetics was established for labeling reaction of 99mTc-N-ethyl-N_(2)S_(2)-memantine,a potential NMDA receptor imaging agent prepared in our laboratory.Four groups of vials (3 vials per group) were added with 0.02 mL (1 mg/mL) N-ethyl-N_(2)S_(2)Memantine,0.08 mL (40 mg/mL) GH,0.05 mL (10 mg/mL) EDTA-2Na,0.035 mL (2 mg/mL) SnF_(2),0.8 mL phosphate buffer(1mol/L,pH 6.5) and 37 MBq Na99mTcO_(4).The vials were incubated at 70℃,80℃,90℃ or 100℃.Samples were taken with capillary from the vials at 2,5,10,20,30,40 and 60min.Labeling yields were determined by TLC.Order of reaction n,rate constant k,activation energy Ea and half life t1/2 of labeling reaction were calculated with the kinetics software we compiled.Mean labeling yields of 99m Tc-N-ethyl-N_(2)S_(2)-memantine at 2,5,10,20,30,40 and 60min were (1) 13.5,15.7,34.0,64.8,81.9,91.4 and 95.4 at 70℃;(2) 13.2,20.5,40.1,70.0,88.2,94.5 and 95.6 at 80℃;(3) 15.6,22.9,43.7,74.3,87.2,93.4 and 96.1 at 90℃;and (4) 20.5,25.8,45.3,81.1,92.2,95.6 and 96.0 at 100℃.The other parameters were;n =1;k=0.053,0.061,0.063 and 0.076 L/min at 70℃,80℃,90℃ and 100℃,respectively;Ea=12.38 kJ/L;t1/2=13.11,11.45,11.05 and 9.07min at 70℃,80℃,90℃ and 100℃,respectively.The mean labeling yield increased with temperature and time,optimized at 100℃ and 40-60min.The concentration of ^(99m)Tc-N-ethyl-N2S2-Memantine was larger than that of Na^(99m)TcO_(4),so n=1.The k increased with reaction,hence the accelerated reaction rate at higher temperatures.The labeling reaction was not so difficult because of the low Ea.The t1/2 decreased with increasing reaction temperature,hence the acceleration of labeling reaction.展开更多
Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications,especially for the steel and refractory industry.Accurate turbulent flow and temperature fields are of major importan...Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications,especially for the steel and refractory industry.Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields.The performances of the GRI-Mech 3.0 and the Jones and Lindstedt mechanisms are compared.Detailed chemistry is included with the GRI-Mech 3.0 and J-L kinetic mechanisms in combination with the laminar flamelet combustion model.The combustion system selected for this comparison is a confined non-premixed methane flame surrounded by co-flowing air The simulation results are compared with experimental data of Lewis and Smoot(2001).展开更多
A data-based reduced-order model(ROM)is developed to accelerate the time integration of stiff chemically reacting systems by effectively removing the stiffness arising from a wide spectrum of chemical time scales.Spec...A data-based reduced-order model(ROM)is developed to accelerate the time integration of stiff chemically reacting systems by effectively removing the stiffness arising from a wide spectrum of chemical time scales.Specifically,the objective of this work is to develop a ROM that acts as a non-stiff surrogate model for the time evolution of the thermochemical state vector(temperature and species mass fractions)during an otherwise highly stiff and nonlinear ignition process.The model follows an encode-forecast-decode strategy that combines a nonlinear autoencoder(AE)for dimensionality reduction(encode and decode steps)with a neural ordinary differential equation(NODE)for modeling the dynamical system in the AE-provided latent space(forecasting step).By means of detailed timescale analysis by leveraging the dynamical system Jacobians,this work shows how data-based projection operators provided by autoencoders can inherently construct the latent spaces by removing unnecessary fast timescales,even more effectively than physics-based counterparts based on an eigenvalue analysis.A key finding is that the most significant degree of stiffness reduction is achieved through an end-to-end training strategy,where both AE and neural ODE parameters are optimized simultaneously,allowing the discovered latent space to be dynamics-informed.In addition to end-to-end training,this work highlights the vital contribution of AE nonlinearity in the stiffness reduction task.For the prediction of homogeneous ignition phenomena for H2-air and C2H4-air mixtures,the proposed ROM achieves several ordersof-magnitude increase in the integration time step size when compared to(a)a baseline CVODE solver for the full-chemical system,(b)statistical technique–principal component analysis(PCA),and(c)computational singular perturbation(CSP),a vetted physics-based stiffness-reducing modeling framework.展开更多
Artificial Neural Networks(ANNs)have emerged as a powerful tool in combustion simulations to replace memory-intensive tabulation of integrated chemical kinetics.Complex reaction mechanisms,however,present a challenge ...Artificial Neural Networks(ANNs)have emerged as a powerful tool in combustion simulations to replace memory-intensive tabulation of integrated chemical kinetics.Complex reaction mechanisms,however,present a challenge for standard ANN approaches as modeling multiple species typically suffers from inaccurate predictions on minor species.This paper presents a novel ANN approach which can be applied on complex reaction mechanisms in tabular data form,and only involves training a single ANN for a complete reaction mechanism.The approach incorporates a network architecture that automatically conserves mass and employs a particular loss weighting based on species depletion.Both modifications are used to improve the overall ANN performance and individual prediction accuracies,especially for minor species mass fractions.To validate its effectiveness,the approach is compared to standard ANNs in terms of performance and ANN complexity.Four distinct reaction mechanisms(H_(2),C_(7)H_(16),C_(12)H_(26),OME_(34))are used as a test cases,and results demonstrate that considerable improvements can be achieved by applying both modifications.展开更多
A modern approach to model reduction in chemical kinetics is often based on the notion of slow invariant manifold.The goal of this paper is to give a comparison of various methods of construction of slow invariant man...A modern approach to model reduction in chemical kinetics is often based on the notion of slow invariant manifold.The goal of this paper is to give a comparison of various methods of construction of slow invariant manifolds using a simple Michaelis-Menten catalytic reaction.We explore a recently introduced Method of Invariant Grids(MIG)for iteratively solving the invariance equation.Various initial approximations for the grid are considered such as Quasi Equilibrium Manifold,Spectral Quasi Equilibrium Manifold,Intrinsic Low Dimensional Manifold and Symmetric Entropic Intrinsic Low Dimensional Manifold.Slow invariant manifold was also computed using the Computational Singular Perturbation(CSP)method.A comparison between MIG and CSP is also reported.展开更多
The time integration method with four-order accuracy, self-starting and implicit for the diffuse chemical reaction kinetics equation or the transient instantaneous temperature filed equation was presented. The example...The time integration method with four-order accuracy, self-starting and implicit for the diffuse chemical reaction kinetics equation or the transient instantaneous temperature filed equation was presented. The examples show that both accuracy and stability are better than Runge-Kutta method with four-order. The coefficients of the equation are stored with sparse matrix pattern, so an algorithm is presented which combines a compact storage scheme with reduced computation cost. The computation of the competitive and consecutive reaction in the rotating packed bed, taken as examples, shows that the method is effective.展开更多
A gold tube simulation device was used to study the cleavage of representative compounds into gas.The goal of this study is to investigate hydrogen isotope composition change of gaseous hydrocarbons during maturity.Ga...A gold tube simulation device was used to study the cleavage of representative compounds into gas.The goal of this study is to investigate hydrogen isotope composition change of gaseous hydrocarbons during maturity.Gas chromatography and isotopic analyses were conducted to determine how the yield of natural gas components and their hydrogen isotopic composition were related to experimental temperature and heating rate.A chemical kinetic model for the generation of each component of the natural gas and for the hydrogen isotopic fractionation was established and calibrated based on the results.Results indicate that the hydrogen isotopic fractionation during the evolution of various gas-forming organic materials can be satisfactorily described by chemical kinetic models.During regular methane generation,the reactions at low-activation-energy region had a greater contribution than the high-activation-energy region.While the reactions with high-activation-energy region had greater contribution of deuterium-rich methane.Compared with carbon isotope fractionation,this results in a greater hydrogen isotopic fractionation,which is more sensitive to changes in maturity.This study lays a foundation for further investigations of genesis and maturity of natural gas provided by hydrogen isotopic fractionation.It also provides fundamental knowledge for investigating the filling history of natural gas reservoir and for identifying.展开更多
A general framework of hydro-mechanical-chemical coupling model is proposed for geomaterial subjected to the dual effects of mechanical loading and chemical degradation. Mechanical damage due to microcracks in solid m...A general framework of hydro-mechanical-chemical coupling model is proposed for geomaterial subjected to the dual effects of mechanical loading and chemical degradation. Mechanical damage due to microcracks in solid matrix and chemical damage induced by the increase of porosity due to dissolution of matrix minerals as well as their interactions are considered. A special model is proposed for sandstone. The reaction rate is formulated within the framework of mineral reaction kinetics and can thus take into account different dissolution mechanisms of three main mineral compositions under different pH values. The increase of porosity is physically defined by the dissolution of mineral composition and the chemical damage is related to the increase of porosity. The mechanical behavior is characterized by unified plastic damage and viscoplastic damage modeling. The effective stress is used for describing the effect of pore pressure. The elastic parameters and plastic evolution as well as viscoplastic evolution are dependent on chemical damage. The advection, which is coupled with mechanical damage and chemical damage, is considered as the dominant mechanism of mass transfer. The application of model proposed is from decoupled experiments to fully coupled experiment. The model offers a convenient approach to describing the hydro-mechanical-chemical coupled behavior of geomaterial.展开更多
In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a...In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a square pressure wave are numerically investigated by considering viscosity,surface tension,and the weak compressibility of the liquid.The theoretical prediction of the yield of oxidants produced inside bubbles during the strong collapse stage of cavitation bubbles is also investigated.The effects of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster on bubble temperature and the quantity of oxidants produced inside bubbles are analyzed.The results show that the change of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster have an effect not only on temperature and the quantity of oxidants inside the bubble,but also on the degradation types of pollutants,which provides a guidance in improving the sonochemical degradation of organic pollutants.展开更多
A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground th...A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.展开更多
Biomass is a kind of renewable energy which is used increasingly in different types of combustion systems or in the production of fuels like bio-oil. Lycopodium is a cellulosic particle, with good combustion propertie...Biomass is a kind of renewable energy which is used increasingly in different types of combustion systems or in the production of fuels like bio-oil. Lycopodium is a cellulosic particle, with good combustion properties, of which microscopic images show that these particles have spherical shapes with identical diameters of 31 μm. The measured density of these particles is 1.0779 g/cm2. Lycopodium particles contain 64.06% carbon, 25.56% oxygen, 8.55% hydrogen and 1.83% nitrogen, and no sulfur. Thermogravimetric analysis in the nitrogen environment indicates that the maximum of particle mass reduction occurs in the temperature range of 250-550 ℃ where the maximum mass reduction in the DTG diagrams also occurs in. In the oxygen environment, an additional peak can also be observed in the temperature range of 500-600 ℃, which points to solid phase combustion and ignition temperature of lycopodium particles. The kinetics of reactions is determined by curve fitting and minimization of error.展开更多
The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin （2,3,7,8-TCDD） is an efficient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H2O ar...The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin （2,3,7,8-TCDD） is an efficient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H2O are introduced in detail at the method of MPWB1K/6-31＋G（d,p）//MPWB1K/6- 311＋G（3df,2p） level. In ozonolysis, H2O is an important source of OH radical formation and initiated the subsequent degradation reaction. The Rice-Ramsperger-Kassel-Marcus （RRKM） theory was applied to calculate rate constants with the temperature ranging from 200 to 600 K. The rate constant of reaction between 2,3,7,8-TCDD and 03 is 4.80 × 10^-20 cm3/（mole.sec） at 298 K and 760 Tort. The atmospheric lifetime of the reaction species was estimated according to rate constants, which is helpful for the atmospheric model study on the degradation and risk assessment of dioxin.展开更多
This work presents a chemical kinetic analysis of different species involved in nitrogen-oxygen mixed gas induced by stationary corona discharge at room temperature and atmospheric pressure.This study takes into accou...This work presents a chemical kinetic analysis of different species involved in nitrogen-oxygen mixed gas induced by stationary corona discharge at room temperature and atmospheric pressure.This study takes into account twenty different chemical species participating in one hundred and seventy selected chemical reactions.The reaction rate coefficients are taken from the literature,and the density is analyzed by the continuity equation without the diffusion term.A large number of investigations considered the removal of NOx showing the effects of N,O and O3 radicals.The aim of the present simulation is to complete these studies by analysing various plasma species under different reduced electric fields in the range of 100-200 Td（1 Td=10-21 V·m^2）.In particular,we analyze the time evolution of depopulation（10^-9-10^-3s）of NOx.We have found that the depopulation rate of NO and NO2 is substantially affected by the rise of reduced electric field as it grows from 100 Td to 200 Td.This allows us to ascertain the important role played by the reduced electric field.展开更多
An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900'C to 1300'C for 1 h. The product batches were subjecte...An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900'C to 1300'C for 1 h. The product batches were subjected to XRD and chemical analysis techniques specific for wollastonite. Mole fractions of different product batches were calculated on the basis of accumulated data to study the kinetics. Specific rate constants and reaction rate were also found out. Various probable models of mechanism for reaction were considered and testified with the laid down criterion for suggesting the suitable one. The resulting data were treated with Arrhenius equation as well and activation energy was calculated--therefrom. In addition to finding it's value from the slope of Arrhenius curve, an alternate method was also applied for this purpose. Both of the values were observed to be comparable. The activation energy required for performed reaction was found to be almost one third of that reported for synthesizing CaSiO3 by using quartz. This referred to the economical preparation of wollastonite by using rice husk as a source of silica instead of quartz.展开更多
The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation...The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.展开更多
基金Supported by the National Natural Science Foundation of China（50806023 50721005 50806024） Program of Introducing Talents of Discipline to Universities of China（“111” Project B06019）
文摘A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the full mechanism using sensitivity analysis,reaction path analysis and quasi steady state(QSS) approximation. The model in premixed flame was validated and with computing savings in diffusion flame was applied by incor-porating into a CFD code. Simulations were performed to explore the effect of coflow air on flame structure and soot formation. Thermal radiation was calculated by a discrete-ordinates method,and soot formation was predicted by a simple two-equation soot model. Model results are in good agreement with those from experiment data and detailed mechanism at atmospheric conditions. The soot nucleation,growth,and oxidation by OH are all enhanced by decrease in coflow air velocity. The peak soot volume fraction region appears in the lower annular region be-tween the peak flame temperature and peak acetylene concentration locations,and the high soot oxidation rate due to the OH attack occurs in the middle annular region because of high temperature.
基金supported by the National Key Research and Development Plan Young Scientists Program (No. 2017YFA0106000)the National Science Fund for Outstanding Young Scholars (No. 31822021)+1 种基金the National Natural Science Foundation of China (No. 31771057)the National Key Research and Development Plan (No. 2016YFC1101100)。
文摘Thrombotic disease is a major problem that endangers human health. At present, MRI and CT are commonly used clinically to diagnose thrombosis, and thrombolytic drugs are used for treatment), but the diagnosis time is lagging, the utilization of drugs is low, and the resulting systemic toxicity problems such as side effects lead to poor treatment effects. Nanotechnology combining photoacoustic dynamics and chemical dynamics has shown great application value in tumor targeting, diagnosis, detection and treatment. It has also become a new direction in the diagnosis and treatment of thrombotic diseases, and has created new applications in the field of nanomaterials. This review summarizes the new progress of this combination in the diagnosis and treatment of thrombotic diseases according to the differences in the construction of the nanotherapy system, at the same time, we put forward some new problems and prospects for the integration of thrombosis diagnosis and treatment.
文摘A package(a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matrix technology to chemical kinetics is included in the tool model, it is only necessary to triangularize the matrix related to the Jacobian matrix of the model equation. The Gear type procedure is used to integrate a model equation and its coupled auxiliary sensitivity coefficient equations. The FORTRAN subroutines of the model equation, the sensitivity coefficient equations, and their Jacobian analytical expressions are generated automatically from a chemical mechanism. The kinetic representation for the model equation and its sensitivity coefficient equations, and their Jacobian matrix is presented. Various FORTRAN subroutines in packages, such as SLODE, modified MA28, Gear package, with which the program runs in conjunction are recommended. The photo\|oxidation of dimethyl disulfide is used for illustration.
基金Supported by the National Natural Science Foundation of China(50976012)
文摘A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.
文摘An explicit expression for local, instantaneous NO production rate model was proposed to simulate NO formation in turbulent methane-air combustion. The average production rates of mixture fraction and scalar dissipation were obtained from asymptotes through approximation of two single-variable probability-density function. The theory predicted significant contributions from the Zeldovich mechanism, but negligible contributions from the nitrous-oxide mechanism in the oxygenconsumption zone. The proposed model was used to simulate NO formation in the pilot methane-air jet diffusion combustion. The simulation results were compared with those obtained by the CFD software FLUENT module. Validation of predictions with the experimental data given by Sandia National Laboratory of the USA indicates that the proposed model yields better results than other models, and the deviation is under 5%. And in some complete reaction zones, the simulation results are even the same as the experimental data. Realizable κ-ε model, Reynold stress model and standard κ-ε model were also investigated to predict the turbulent combustion reaction, which shows that the simulation results of velocities, temperatures, and concentrations of combustion productions by standard κ-ε model are in accordance with the experimental data.
基金Supported by the Jiangsu Natural Science Foundation (BK2008111,BK2010157)the National Natural Science Foundation of China (30770602)
文摘In this work,a calculation method of chemical kinetics was established for labeling reaction of 99mTc-N-ethyl-N_(2)S_(2)-memantine,a potential NMDA receptor imaging agent prepared in our laboratory.Four groups of vials (3 vials per group) were added with 0.02 mL (1 mg/mL) N-ethyl-N_(2)S_(2)Memantine,0.08 mL (40 mg/mL) GH,0.05 mL (10 mg/mL) EDTA-2Na,0.035 mL (2 mg/mL) SnF_(2),0.8 mL phosphate buffer(1mol/L,pH 6.5) and 37 MBq Na99mTcO_(4).The vials were incubated at 70℃,80℃,90℃ or 100℃.Samples were taken with capillary from the vials at 2,5,10,20,30,40 and 60min.Labeling yields were determined by TLC.Order of reaction n,rate constant k,activation energy Ea and half life t1/2 of labeling reaction were calculated with the kinetics software we compiled.Mean labeling yields of 99m Tc-N-ethyl-N_(2)S_(2)-memantine at 2,5,10,20,30,40 and 60min were (1) 13.5,15.7,34.0,64.8,81.9,91.4 and 95.4 at 70℃;(2) 13.2,20.5,40.1,70.0,88.2,94.5 and 95.6 at 80℃;(3) 15.6,22.9,43.7,74.3,87.2,93.4 and 96.1 at 90℃;and (4) 20.5,25.8,45.3,81.1,92.2,95.6 and 96.0 at 100℃.The other parameters were;n =1;k=0.053,0.061,0.063 and 0.076 L/min at 70℃,80℃,90℃ and 100℃,respectively;Ea=12.38 kJ/L;t1/2=13.11,11.45,11.05 and 9.07min at 70℃,80℃,90℃ and 100℃,respectively.The mean labeling yield increased with temperature and time,optimized at 100℃ and 40-60min.The concentration of ^(99m)Tc-N-ethyl-N2S2-Memantine was larger than that of Na^(99m)TcO_(4),so n=1.The k increased with reaction,hence the accelerated reaction rate at higher temperatures.The labeling reaction was not so difficult because of the low Ea.The t1/2 decreased with increasing reaction temperature,hence the acceleration of labeling reaction.
文摘Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications,especially for the steel and refractory industry.Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields.The performances of the GRI-Mech 3.0 and the Jones and Lindstedt mechanisms are compared.Detailed chemistry is included with the GRI-Mech 3.0 and J-L kinetic mechanisms in combination with the laminar flamelet combustion model.The combustion system selected for this comparison is a confined non-premixed methane flame surrounded by co-flowing air The simulation results are compared with experimental data of Lewis and Smoot(2001).
基金support from the Argonne Leadership Computing Facility,which is a U.S.Department of Energy Office of Science User Facility operated under contract DE-AC02-06CH11357support of ONR,United States Grant No.N00014-21-1-2475 with Dr.Eric Marineau as Program Manager.
文摘A data-based reduced-order model(ROM)is developed to accelerate the time integration of stiff chemically reacting systems by effectively removing the stiffness arising from a wide spectrum of chemical time scales.Specifically,the objective of this work is to develop a ROM that acts as a non-stiff surrogate model for the time evolution of the thermochemical state vector(temperature and species mass fractions)during an otherwise highly stiff and nonlinear ignition process.The model follows an encode-forecast-decode strategy that combines a nonlinear autoencoder(AE)for dimensionality reduction(encode and decode steps)with a neural ordinary differential equation(NODE)for modeling the dynamical system in the AE-provided latent space(forecasting step).By means of detailed timescale analysis by leveraging the dynamical system Jacobians,this work shows how data-based projection operators provided by autoencoders can inherently construct the latent spaces by removing unnecessary fast timescales,even more effectively than physics-based counterparts based on an eigenvalue analysis.A key finding is that the most significant degree of stiffness reduction is achieved through an end-to-end training strategy,where both AE and neural ODE parameters are optimized simultaneously,allowing the discovered latent space to be dynamics-informed.In addition to end-to-end training,this work highlights the vital contribution of AE nonlinearity in the stiffness reduction task.For the prediction of homogeneous ignition phenomena for H2-air and C2H4-air mixtures,the proposed ROM achieves several ordersof-magnitude increase in the integration time step size when compared to(a)a baseline CVODE solver for the full-chemical system,(b)statistical technique–principal component analysis(PCA),and(c)computational singular perturbation(CSP),a vetted physics-based stiffness-reducing modeling framework.
文摘Artificial Neural Networks(ANNs)have emerged as a powerful tool in combustion simulations to replace memory-intensive tabulation of integrated chemical kinetics.Complex reaction mechanisms,however,present a challenge for standard ANN approaches as modeling multiple species typically suffers from inaccurate predictions on minor species.This paper presents a novel ANN approach which can be applied on complex reaction mechanisms in tabular data form,and only involves training a single ANN for a complete reaction mechanism.The approach incorporates a network architecture that automatically conserves mass and employs a particular loss weighting based on species depletion.Both modifications are used to improve the overall ANN performance and individual prediction accuracies,especially for minor species mass fractions.To validate its effectiveness,the approach is compared to standard ANNs in terms of performance and ANN complexity.Four distinct reaction mechanisms(H_(2),C_(7)H_(16),C_(12)H_(26),OME_(34))are used as a test cases,and results demonstrate that considerable improvements can be achieved by applying both modifications.
基金supported by SNF,Project 200021-107885/1(E.C.)and by BFE,Project 100862(I.V.K.)。
文摘A modern approach to model reduction in chemical kinetics is often based on the notion of slow invariant manifold.The goal of this paper is to give a comparison of various methods of construction of slow invariant manifolds using a simple Michaelis-Menten catalytic reaction.We explore a recently introduced Method of Invariant Grids(MIG)for iteratively solving the invariance equation.Various initial approximations for the grid are considered such as Quasi Equilibrium Manifold,Spectral Quasi Equilibrium Manifold,Intrinsic Low Dimensional Manifold and Symmetric Entropic Intrinsic Low Dimensional Manifold.Slow invariant manifold was also computed using the Computational Singular Perturbation(CSP)method.A comparison between MIG and CSP is also reported.
文摘The time integration method with four-order accuracy, self-starting and implicit for the diffuse chemical reaction kinetics equation or the transient instantaneous temperature filed equation was presented. The examples show that both accuracy and stability are better than Runge-Kutta method with four-order. The coefficients of the equation are stored with sparse matrix pattern, so an algorithm is presented which combines a compact storage scheme with reduced computation cost. The computation of the competitive and consecutive reaction in the rotating packed bed, taken as examples, shows that the method is effective.
基金the National Natural Science Foundation of China(41672130,41772131)the National Oil and Gas Major Project(2016ZX05061-003-001,2016ZX05029002-002)+1 种基金the Sinopec Scientific and Technological Research Project(P17027-3)the Ministry of Education’s Independent Innovation Fund Project(14CX02224A)for financial support of this study。
文摘A gold tube simulation device was used to study the cleavage of representative compounds into gas.The goal of this study is to investigate hydrogen isotope composition change of gaseous hydrocarbons during maturity.Gas chromatography and isotopic analyses were conducted to determine how the yield of natural gas components and their hydrogen isotopic composition were related to experimental temperature and heating rate.A chemical kinetic model for the generation of each component of the natural gas and for the hydrogen isotopic fractionation was established and calibrated based on the results.Results indicate that the hydrogen isotopic fractionation during the evolution of various gas-forming organic materials can be satisfactorily described by chemical kinetic models.During regular methane generation,the reactions at low-activation-energy region had a greater contribution than the high-activation-energy region.While the reactions with high-activation-energy region had greater contribution of deuterium-rich methane.Compared with carbon isotope fractionation,this results in a greater hydrogen isotopic fractionation,which is more sensitive to changes in maturity.This study lays a foundation for further investigations of genesis and maturity of natural gas provided by hydrogen isotopic fractionation.It also provides fundamental knowledge for investigating the filling history of natural gas reservoir and for identifying.
基金Project supported by the National Natural Science Foundation of China(Nos.51009132,50920105908,50979104and10972221)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(No.Z011006)
文摘A general framework of hydro-mechanical-chemical coupling model is proposed for geomaterial subjected to the dual effects of mechanical loading and chemical degradation. Mechanical damage due to microcracks in solid matrix and chemical damage induced by the increase of porosity due to dissolution of matrix minerals as well as their interactions are considered. A special model is proposed for sandstone. The reaction rate is formulated within the framework of mineral reaction kinetics and can thus take into account different dissolution mechanisms of three main mineral compositions under different pH values. The increase of porosity is physically defined by the dissolution of mineral composition and the chemical damage is related to the increase of porosity. The mechanical behavior is characterized by unified plastic damage and viscoplastic damage modeling. The effective stress is used for describing the effect of pore pressure. The elastic parameters and plastic evolution as well as viscoplastic evolution are dependent on chemical damage. The advection, which is coupled with mechanical damage and chemical damage, is considered as the dominant mechanism of mass transfer. The application of model proposed is from decoupled experiments to fully coupled experiment. The model offers a convenient approach to describing the hydro-mechanical-chemical coupled behavior of geomaterial.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674207)
文摘In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a square pressure wave are numerically investigated by considering viscosity,surface tension,and the weak compressibility of the liquid.The theoretical prediction of the yield of oxidants produced inside bubbles during the strong collapse stage of cavitation bubbles is also investigated.The effects of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster on bubble temperature and the quantity of oxidants produced inside bubbles are analyzed.The results show that the change of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster have an effect not only on temperature and the quantity of oxidants inside the bubble,but also on the degradation types of pollutants,which provides a guidance in improving the sonochemical degradation of organic pollutants.
基金financial support from the National Science and Technology Major Project of China(Grant No. 2008ZX05018)Taishan Scholar Constructive Engineering Foundation of Shandong province(No. ts20120518)
文摘A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.
基金supported by the Ministry of Science, Research & Technology of Iran
文摘Biomass is a kind of renewable energy which is used increasingly in different types of combustion systems or in the production of fuels like bio-oil. Lycopodium is a cellulosic particle, with good combustion properties, of which microscopic images show that these particles have spherical shapes with identical diameters of 31 μm. The measured density of these particles is 1.0779 g/cm2. Lycopodium particles contain 64.06% carbon, 25.56% oxygen, 8.55% hydrogen and 1.83% nitrogen, and no sulfur. Thermogravimetric analysis in the nitrogen environment indicates that the maximum of particle mass reduction occurs in the temperature range of 250-550 ℃ where the maximum mass reduction in the DTG diagrams also occurs in. In the oxygen environment, an additional peak can also be observed in the temperature range of 500-600 ℃, which points to solid phase combustion and ignition temperature of lycopodium particles. The kinetics of reactions is determined by curve fitting and minimization of error.
基金supported by National Natural Science Foundation of China(No.21277082,21177076,71201093)the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province(No.BS2012HZ009,BS2012SF012)+2 种基金the Hi-Tech Research and Development Program(863)of China(No.2012AA06A301)the New Century Excellent Talents in University(NCET-13-0349)the Open Project from special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control(No.13K05ESPCP)
文摘The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin （2,3,7,8-TCDD） is an efficient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H2O are introduced in detail at the method of MPWB1K/6-31＋G（d,p）//MPWB1K/6- 311＋G（3df,2p） level. In ozonolysis, H2O is an important source of OH radical formation and initiated the subsequent degradation reaction. The Rice-Ramsperger-Kassel-Marcus （RRKM） theory was applied to calculate rate constants with the temperature ranging from 200 to 600 K. The rate constant of reaction between 2,3,7,8-TCDD and 03 is 4.80 × 10^-20 cm3/（mole.sec） at 298 K and 760 Tort. The atmospheric lifetime of the reaction species was estimated according to rate constants, which is helpful for the atmospheric model study on the degradation and risk assessment of dioxin.
文摘This work presents a chemical kinetic analysis of different species involved in nitrogen-oxygen mixed gas induced by stationary corona discharge at room temperature and atmospheric pressure.This study takes into account twenty different chemical species participating in one hundred and seventy selected chemical reactions.The reaction rate coefficients are taken from the literature,and the density is analyzed by the continuity equation without the diffusion term.A large number of investigations considered the removal of NOx showing the effects of N,O and O3 radicals.The aim of the present simulation is to complete these studies by analysing various plasma species under different reduced electric fields in the range of 100-200 Td（1 Td=10-21 V·m^2）.In particular,we analyze the time evolution of depopulation（10^-9-10^-3s）of NOx.We have found that the depopulation rate of NO and NO2 is substantially affected by the rise of reduced electric field as it grows from 100 Td to 200 Td.This allows us to ascertain the important role played by the reduced electric field.
文摘An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900'C to 1300'C for 1 h. The product batches were subjected to XRD and chemical analysis techniques specific for wollastonite. Mole fractions of different product batches were calculated on the basis of accumulated data to study the kinetics. Specific rate constants and reaction rate were also found out. Various probable models of mechanism for reaction were considered and testified with the laid down criterion for suggesting the suitable one. The resulting data were treated with Arrhenius equation as well and activation energy was calculated--therefrom. In addition to finding it's value from the slope of Arrhenius curve, an alternate method was also applied for this purpose. Both of the values were observed to be comparable. The activation energy required for performed reaction was found to be almost one third of that reported for synthesizing CaSiO3 by using quartz. This referred to the economical preparation of wollastonite by using rice husk as a source of silica instead of quartz.
文摘The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.
