Polyoxymethylene dimethyl ether(PODE n,n≥1)is a class of oxygenated fuels containing unique carbon-oxygen chain structure and a promising alternative fuel for diesel engines.In this study,low-temperature oxidation ch...Polyoxymethylene dimethyl ether(PODE n,n≥1)is a class of oxygenated fuels containing unique carbon-oxygen chain structure and a promising alternative fuel for diesel engines.In this study,low-temperature oxidation characteristics of PODE_(3) were studied experimentally and numerically.Experiments were performed in a jet-stirred reactor(JSR)at equivalence ratios of 0.5,1.0 and 2.0,in the temperature range of 500 to 950 K,and at atmospheric pressure.Mole fractions of PODE_(3),O_(2),H_(2),CO,CO_(2),CH_(3) OH and C_(1)-C_(2) hydrocarbons were measured by gas chromatograph(GC).Experimental measurements were compared with the simulation results based on two literature low-temperature oxidation models,denoted as the He model and the Cai model,respectively.Good agreement was obtained between the measured and simulated fuel consumption profiles,while a deviation was observed between the experimental and simulation results on the mole fractions of O_(2) and intermediate products at medium temperatures.Reaction pathway analyses based on the two models were performed,revealing that the second O_(2)-addition reaction pathway is more significant in the prediction by the Cai model than that by the He model.Sensitivity analyses pointed out that the most important reactions affecting fuel consumption are the H-abstraction reactions of PODE_(3),and the decomposition of H_(2) O_(2) and the consumption of CH_(2)O become more sensitive at medium temperatures.展开更多
Oxidation of acetylene(C_(2)H_(2))has been investigated in a high-pressure jet-stirred reactor(HP-JSR)with equivalence ratiosΦ=0.5,1.0,2.0 and 3.0 in the temperature range of 650 K-900 K at 1.2 MPa.18 products and in...Oxidation of acetylene(C_(2)H_(2))has been investigated in a high-pressure jet-stirred reactor(HP-JSR)with equivalence ratiosΦ=0.5,1.0,2.0 and 3.0 in the temperature range of 650 K-900 K at 1.2 MPa.18 products and intermediates were analyzed qualitatively and quantitatively by gas chromatography(GC)and gas chromatography-mass spectrometry(GC-MS).Generally,withΦincreasing,the production of intermediates increases significantly.CH_(4),C_(2)H_(4),C_(2)H_(6),C_(3)H_(6)and C_(3)H_(8)were important intermediates,which were formed abundantly atΦ=3.0.Sufficient light hydrocarbon intermediates could be an important reason for significant formation of cyclopentadiene,benzene,toluene and styrene atΦ=3.0.A detailed kinetic mechanism consisting of 299 species and 2041 reactions has been developed with reasonable predictions against the present data and previous results obtained at 0.1 MPa.According to flux and sensitivity analysis,H and OH radicals play important roles in the consumption of C_(2)H_(2).The combinations among light hydrocarbons and their free radicals are the main generation pathways of aromatics.C_(3)H_(3),IC_(4)H_(5)and AC_(3)H_(5)are important precursors for the formation of aromatics.By comparing the results of atmospheric pressure and high pressure,it can be found that increasing the pressure is conducive to fuel consumption and aromatics generation.展开更多
The safety concerns of lithium-ion batteries(LIBs)due to thermal runaway hinder their broad applications.Flammable electrolytes are the major cause of gas venting and fire hazards of LIB,particularly when limited oxyg...The safety concerns of lithium-ion batteries(LIBs)due to thermal runaway hinder their broad applications.Flammable electrolytes are the major cause of gas venting and fire hazards of LIB,particularly when limited oxygen can be released because of the degradation of cathode materials.However,studies on the combustion characteristics of electrolytes under highly incomplete conditions,corresponding to thermal runaway scenarios,are limited.Therefore,a comprehensive experimental and kinetic study of three typical electrolyte solvents,namely,dimethyl carbonate(DMC),diethyl carbonate(DEC),and ethyl methyl carbonate(EMC),was performed under oxygen-lean and pyrolysis conditions.The experiments were conducted in a jet-stirred reactor with equivalence ratios of 2.5,5.0,and∞at atmospheric pressure,and the temperature ranged from 600 to 1100 K.Primary gas products,including H_(2),CH_(4),C_(2)H_(4),C_(2)H_(6),CH_(3)OH,C_(2)H_(5)OH,CO,and CO_(2),were quantified using gas chromatography.Results revealed that the consumption onset temperatures were in the order of DEC~EMC<DMC,regardless of the oxygen concentration.The addition of oxygen primarily influenced the consumption rate of DMC,whereas that of DEC and EMC was found to be less sensitive.Moreover,the oxidation of carbonates was prone to generate CO,CO_(2),H_(2),and CH_(4)rather than C_(2)H_(4).Reaction pathway analysis indicated that DEC and EMC were primarily consumed by two sequential unimolecular decomposition reactions,forming C_(2)H_(4),C_(2)H_(5)OH/CH_(3)OH,and CO_(2)regardless of the oxygen level.On the contrary,the primary reaction pathway for DMC changed from a unimolecular decomposition reaction to an H-abstraction reaction with oxygen addition.Furthermore,rate of production analysis was performed to obtain insights into the gas generation mechanism of flammable gases,such as H_(2),CH_(4),and C_(2)H_(4).The primary contributors to the formation and consumption of these gases under pyrolysis and oxidation conditions were revealed.展开更多
Efficient mixing and thermal control are important in the flow reactor for obtaining a high product yield and selectivity.Here,we report a heterogeneous chemical kinetic study of propene oxidation within a newly desig...Efficient mixing and thermal control are important in the flow reactor for obtaining a high product yield and selectivity.Here,we report a heterogeneous chemical kinetic study of propene oxidation within a newly designed catalytic jet-stirred reactor(CJSR).To better understand the interplay between the catalytic performances and properties,the CuO thin films have been characterized and the adsorbed energies of propene on the adsorbed and lattice oxygen were calculated using density functional theory(DFT)method.Structure and morphology analyses revealed a monoclinic structure with nano-crystallite size and porous microstructure,which is responsible for holding an important quantity of adsorbed oxygen.The residence time inside the flow CJSR(1.12–7.84 s)makes it suitable for kinetic study and gives guidance for scale-up.The kinetic study revealed that using CJSR the reaction rate increases with O_2concentration that is commonly not achievable for catalytic flow tube reactor,whereas the reaction rate tends to increase slightly above 30%of O_2due to the catalyst surface saturation.Moreover,DFT calculations demonstrated that adsorbed oxygen is the most involved oxygen,and it has found that the pathway of producing propene oxide makes the reaction of C_3H_6over CuO surface more likely to proceed.Accordingly,these findings revealed that CJSR combined with theoretical calculation is suitable for kinetic study,which can pave the way to investigate the kinetic study of other exhaust gases.展开更多
Soot formation was investigated numerically with CO2 addition in a jet-stirred/plug-flow reactor （JSR/PFR） C2H4/OJN2 reactor （C/O ratio of 2.2） at atmospheric pressure. An updated Kazakov mechanism empha- sizes th...Soot formation was investigated numerically with CO2 addition in a jet-stirred/plug-flow reactor （JSR/PFR） C2H4/OJN2 reactor （C/O ratio of 2.2） at atmospheric pressure. An updated Kazakov mechanism empha- sizes the effect of the O2/CO2 atmosphere instead of an O2/N2 one in the premixed flame. The soot formation was taken into account in the JSR/PFR for C2H4/O2/N2. The effects of CO2 addition on soot formation in different C2H4/O2/CO2/N2 atmospheres were studied, with special emphasis on the chemical effect. The simulation shows that the endothermic reaction CO2 ＋ H - CO ＋ OH is responsible of the reduction of hydrocarbon intermediates in the CO2 added combustion through the supplementary formation of hydroxyl radicals. The competition of CO2 for H radical through the above forward reaction with the single most important chain branching reaction H ＋ O2, ＇ O ＋ OH reduces significantly the fuel burning rate. The chemical effects of CO2 cause a significant increase in residence time and mole fractions of CO and OH, significant decreases in some intermediates （H, C2H2）, polycyclic aromatic hydrocarbons （PAHs, C6H6 and CI6H10, etc.） and soot volume fraction. The CO2 addition will leads to a decrease by only about 5% to 20% of the maximum mole fractions of some C3 to Clo hydrocarbon intermediates. The sensitivity analysis and reaction-path analysis results show that C2H4 reaction path and products are altered due to the CO2 addition.展开更多
基金supported by the National Natural Science Foundation of China(Grants No.52022058,51776124 and 51861135303)the Shanghai Science and Technology Committee(Grant No.19160745400).
文摘Polyoxymethylene dimethyl ether(PODE n,n≥1)is a class of oxygenated fuels containing unique carbon-oxygen chain structure and a promising alternative fuel for diesel engines.In this study,low-temperature oxidation characteristics of PODE_(3) were studied experimentally and numerically.Experiments were performed in a jet-stirred reactor(JSR)at equivalence ratios of 0.5,1.0 and 2.0,in the temperature range of 500 to 950 K,and at atmospheric pressure.Mole fractions of PODE_(3),O_(2),H_(2),CO,CO_(2),CH_(3) OH and C_(1)-C_(2) hydrocarbons were measured by gas chromatograph(GC).Experimental measurements were compared with the simulation results based on two literature low-temperature oxidation models,denoted as the He model and the Cai model,respectively.Good agreement was obtained between the measured and simulated fuel consumption profiles,while a deviation was observed between the experimental and simulation results on the mole fractions of O_(2) and intermediate products at medium temperatures.Reaction pathway analyses based on the two models were performed,revealing that the second O_(2)-addition reaction pathway is more significant in the prediction by the Cai model than that by the He model.Sensitivity analyses pointed out that the most important reactions affecting fuel consumption are the H-abstraction reactions of PODE_(3),and the decomposition of H_(2) O_(2) and the consumption of CH_(2)O become more sensitive at medium temperatures.
基金the financial support from NSFC(No.51976216/51888103/M-0139)MOST(2021YFA0716200)+2 种基金the National Science and Technology Major Project(J2019-Ⅲ-0005-0048)Beijing Municipal Natural Science Foundation(JQ20017)K.C.Wong Education Foundation(GJTD-2020-07)。
文摘Oxidation of acetylene(C_(2)H_(2))has been investigated in a high-pressure jet-stirred reactor(HP-JSR)with equivalence ratiosΦ=0.5,1.0,2.0 and 3.0 in the temperature range of 650 K-900 K at 1.2 MPa.18 products and intermediates were analyzed qualitatively and quantitatively by gas chromatography(GC)and gas chromatography-mass spectrometry(GC-MS).Generally,withΦincreasing,the production of intermediates increases significantly.CH_(4),C_(2)H_(4),C_(2)H_(6),C_(3)H_(6)and C_(3)H_(8)were important intermediates,which were formed abundantly atΦ=3.0.Sufficient light hydrocarbon intermediates could be an important reason for significant formation of cyclopentadiene,benzene,toluene and styrene atΦ=3.0.A detailed kinetic mechanism consisting of 299 species and 2041 reactions has been developed with reasonable predictions against the present data and previous results obtained at 0.1 MPa.According to flux and sensitivity analysis,H and OH radicals play important roles in the consumption of C_(2)H_(2).The combinations among light hydrocarbons and their free radicals are the main generation pathways of aromatics.C_(3)H_(3),IC_(4)H_(5)and AC_(3)H_(5)are important precursors for the formation of aromatics.By comparing the results of atmospheric pressure and high pressure,it can be found that increasing the pressure is conducive to fuel consumption and aromatics generation.
基金supported by the National Natural Science Foundation of China(Grant Nos.52106261,52022058)the Postdoctoral Research Foundation of China(Grant Nos.2022M712042,2022T150403)the Science and Technology Commission of Shanghai Municipality(Grant No.22170712600)。
文摘The safety concerns of lithium-ion batteries(LIBs)due to thermal runaway hinder their broad applications.Flammable electrolytes are the major cause of gas venting and fire hazards of LIB,particularly when limited oxygen can be released because of the degradation of cathode materials.However,studies on the combustion characteristics of electrolytes under highly incomplete conditions,corresponding to thermal runaway scenarios,are limited.Therefore,a comprehensive experimental and kinetic study of three typical electrolyte solvents,namely,dimethyl carbonate(DMC),diethyl carbonate(DEC),and ethyl methyl carbonate(EMC),was performed under oxygen-lean and pyrolysis conditions.The experiments were conducted in a jet-stirred reactor with equivalence ratios of 2.5,5.0,and∞at atmospheric pressure,and the temperature ranged from 600 to 1100 K.Primary gas products,including H_(2),CH_(4),C_(2)H_(4),C_(2)H_(6),CH_(3)OH,C_(2)H_(5)OH,CO,and CO_(2),were quantified using gas chromatography.Results revealed that the consumption onset temperatures were in the order of DEC~EMC<DMC,regardless of the oxygen concentration.The addition of oxygen primarily influenced the consumption rate of DMC,whereas that of DEC and EMC was found to be less sensitive.Moreover,the oxidation of carbonates was prone to generate CO,CO_(2),H_(2),and CH_(4)rather than C_(2)H_(4).Reaction pathway analysis indicated that DEC and EMC were primarily consumed by two sequential unimolecular decomposition reactions,forming C_(2)H_(4),C_(2)H_(5)OH/CH_(3)OH,and CO_(2)regardless of the oxygen level.On the contrary,the primary reaction pathway for DMC changed from a unimolecular decomposition reaction to an H-abstraction reaction with oxygen addition.Furthermore,rate of production analysis was performed to obtain insights into the gas generation mechanism of flammable gases,such as H_(2),CH_(4),and C_(2)H_(4).The primary contributors to the formation and consumption of these gases under pyrolysis and oxidation conditions were revealed.
基金financial support from the Ministry of Science and Technology of China (2017YFA0402800)the National Natural Science Foundation of China (51476168 and 91541102)+1 种基金Recruitment Program of Global Youth Expertsthe support of Chinese Academy of Sciences for senior international scientists within the framework of PIFI program (2017PE0009)
文摘Efficient mixing and thermal control are important in the flow reactor for obtaining a high product yield and selectivity.Here,we report a heterogeneous chemical kinetic study of propene oxidation within a newly designed catalytic jet-stirred reactor(CJSR).To better understand the interplay between the catalytic performances and properties,the CuO thin films have been characterized and the adsorbed energies of propene on the adsorbed and lattice oxygen were calculated using density functional theory(DFT)method.Structure and morphology analyses revealed a monoclinic structure with nano-crystallite size and porous microstructure,which is responsible for holding an important quantity of adsorbed oxygen.The residence time inside the flow CJSR(1.12–7.84 s)makes it suitable for kinetic study and gives guidance for scale-up.The kinetic study revealed that using CJSR the reaction rate increases with O_2concentration that is commonly not achievable for catalytic flow tube reactor,whereas the reaction rate tends to increase slightly above 30%of O_2due to the catalyst surface saturation.Moreover,DFT calculations demonstrated that adsorbed oxygen is the most involved oxygen,and it has found that the pathway of producing propene oxide makes the reaction of C_3H_6over CuO surface more likely to proceed.Accordingly,these findings revealed that CJSR combined with theoretical calculation is suitable for kinetic study,which can pave the way to investigate the kinetic study of other exhaust gases.
基金Supported by the Foundation of State Key Laboratory of Coal Combustion, the National Natural Science Foundation of China （51306022, 51176059） and the Natural Science Foundation of Hubei Province （2013CFB398）.
文摘Soot formation was investigated numerically with CO2 addition in a jet-stirred/plug-flow reactor （JSR/PFR） C2H4/OJN2 reactor （C/O ratio of 2.2） at atmospheric pressure. An updated Kazakov mechanism empha- sizes the effect of the O2/CO2 atmosphere instead of an O2/N2 one in the premixed flame. The soot formation was taken into account in the JSR/PFR for C2H4/O2/N2. The effects of CO2 addition on soot formation in different C2H4/O2/CO2/N2 atmospheres were studied, with special emphasis on the chemical effect. The simulation shows that the endothermic reaction CO2 ＋ H - CO ＋ OH is responsible of the reduction of hydrocarbon intermediates in the CO2 added combustion through the supplementary formation of hydroxyl radicals. The competition of CO2 for H radical through the above forward reaction with the single most important chain branching reaction H ＋ O2, ＇ O ＋ OH reduces significantly the fuel burning rate. The chemical effects of CO2 cause a significant increase in residence time and mole fractions of CO and OH, significant decreases in some intermediates （H, C2H2）, polycyclic aromatic hydrocarbons （PAHs, C6H6 and CI6H10, etc.） and soot volume fraction. The CO2 addition will leads to a decrease by only about 5% to 20% of the maximum mole fractions of some C3 to Clo hydrocarbon intermediates. The sensitivity analysis and reaction-path analysis results show that C2H4 reaction path and products are altered due to the CO2 addition.
