本研究基于自行搭建的5 k W旋流预混火焰实验台,开展了轴向空气分级方式下CH_(4)/NH_(3)旋流预混火焰的实验测试,重点考察了分级风比例、分级风高度及分级风喷口数目对CH_(4)/NH_(3)旋流预混火焰燃烧及排放特性的影响。结果表明:随着NH_...本研究基于自行搭建的5 k W旋流预混火焰实验台,开展了轴向空气分级方式下CH_(4)/NH_(3)旋流预混火焰的实验测试,重点考察了分级风比例、分级风高度及分级风喷口数目对CH_(4)/NH_(3)旋流预混火焰燃烧及排放特性的影响。结果表明:随着NH_(3)占比的增大,火焰高度变长,燃烧室出口的NO排放量呈先增大后减小的趋势且在NH_(3)占比为50%达到峰值;在50%掺氨工况下采用轴向空气分级使一级燃烧室处于富燃状态可以有效降低NO的排放,其中分级风的最佳比例范围是30%~50%(当量比1.21~1.70),且随着分级风高度的增大呈下降趋势;此外,在最佳分级风比例和高度条件下(分级风高度80 mm、占比30%),增加分级风的喷口数目可减轻分级风碰撞对上游主燃区富燃状态的影响,使NO排放进一步降低。展开更多
Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Co...Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Consequently,it is desired to investigate the mechanisms of the FLP-catalyzed hydrogenation of C=C and C=O and provide insight into the modification of CeO_(2)catalysts for the selective hydrogenation.In this work,the reaction mechanism of the hydrogenation of CH_(2)=CH_(2)and CH_(3)CH=O at the FLP sites constructed on CeO_(2)(110)surface was investigated by density functional theory(DFT),with the classical Lewis acid-base pairs(CLP)site as the reference.The results illustrate that at the CLP site,the dissociated hydride(H^(δ−))forms a stable H−O bond with the surface O atom,while at the FLP site,H^(δ−)is stabilized by Ce,displaying higher activity on the one hand.On the other hand,the electron cloud density of the Ce atom at the FLP site is higher,which can transfer more electrons to the adsorbed C_(C=C)and O_(C=O)atoms,leading to a higher degree of activation for C=C and C=O bonds,as indicated by the Bader charge analysis.Therefore,compared to the CLP site,the FLP site exhibits higher hydrogenation activity for CH_(2)=CH_(2)and CH_(3)CH=O.Furthermore,at the FLP sites,it demonstrates high efficiency in catalyzing the hydrogenation of CH_(2)=CH_(2)with the rate-determining barrier of 1.04 eV,but it shows limited activity for the hydrogenation of CH_(3)CH=O with the rate-determining barrier of 1.94 eV.It means that the selective hydrogenation of C=C can be effectively achieved at the FLP sites concerning selective hydrogenation catalysis.The insights shown in this work help to clarify the reaction mechanism of the hydrogenation of C=C and C=O at FLP site on CeO_(2)(110)and reveal the relationship between the catalytic performance and the nature of the active site,which is of great benefit to development of rational design of heterogeneous FLP catalysts.展开更多
The aim of this paper is to explore the effect of geometrical parameters on ultimate load-carrying capacity of a circular hollow section(CHS)X-joint under axial compression of the brace end.First of all,finite element...The aim of this paper is to explore the effect of geometrical parameters on ultimate load-carrying capacity of a circular hollow section(CHS)X-joint under axial compression of the brace end.First of all,finite element(FE)model to calculate ultimate load-carrying capacity of the CHS X-joint subjected to uniaxial load of the brace is constructed,and the calculated load–displacement curves are compared to the experimental ones.After validation of the FE model,46080 groups of FE calculation models with different geometrical parameters are generated by means of parametric modeling.Subsequently,eight variables including gusset thickness and chord thickness are set as input to predict load-carrying capacity of the CHS X-joint by four machine learning(ML)algorithms,i.e.,Generalized Regression Neural Network,Support Vector Machine,random forest(RF),and Extreme Gradient Boosting(XGBoost).Finally,the constructed ML prediction models are interpreted by SHapley Additive exPlanations,to explore the impact weight of each factor on ultimate load-carrying capacity of the joint.The results show that all the four models can predict the load-carrying capacity of the subject accurately,with all the R2 values greater than 0.97.In addition,RF model yields the minimum mean-square error,Root Mean Squared Error,Mean Absolute Error,and Mean Absolute Percentage Error values,and the greatest R2 value,while the prediction accuracy of XGBoost is relatively worse.Among all the eight considered geometrical parameters,brace diameter has the strongest impact on load-carrying capacity of the joint,followed by chord thickness,chord ring width,chord ring thickness,brace ring width,and brace thickness,while the thicknesses of the gusset plate and brace have marginal influence on load-carrying capacity.The study of the current paper can provide guidelines for dimension design of CHS X-joints.展开更多
Selective perchlorate(ClO_(4)^(−))removal from surface water is a pressing need due to the stringent perchlorate drinking water limits around the world.Herein,we anchored N^(+)–C–H hydrogen bond donors in hydrophobi...Selective perchlorate(ClO_(4)^(−))removal from surface water is a pressing need due to the stringent perchlorate drinking water limits around the world.Herein,we anchored N^(+)–C–H hydrogen bond donors in hydrophobic cavities via interactions of cationic surfactants with montmorillonite to prioritize perchlorate bonding.The prepared adsorbent exhibited high selectivity over commonly occurring competing anions,including SO_(4)^(2−),NO_(3)^(−),PO_(4)^(3−),HCO_(3)^(−),and halide anions.High adsorption capacity,fast adsorption kinetics,and excellent regeneration ability(removal efficiency≥80%after 20 cycles)were confirmed via batch experiments.Unconventional CH···O hydrogen bonding was verified as the primary driving force for perchlorate adsorption,which relies on the higher bond energy(∼80 kcal·mol−1)than conventional bonding.The removal efficiency of anions followed the order of the Hofmeister Series,demonstrating the importance of hydrophobic cavities formed by the tail groups of cationic surfactants.The hydrophobic cavities sheltered the C–H bonds from interacting with anions of low hydration energy(e.g.,perchlorate).Furthermore,a fixed-bed column test demonstrated that about 2900 bed volumes of the feeding streams(∼500μg·L^(−1))can be treated to≤70μg·L^(−1),with an enrichment factor of 10.3.Overall,on the basis of the hydrophobicity-induced hydrogen bonding mechanism,a series of low-cost adsorbents can be synthesized and applied for specific perchlorate removal.展开更多
Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were ...Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were generat-ed with internal excitation by multiphoton photolysis of CHBr_(3)at 248 nm,and its rotational temperature was found to relax to the flow temperature in a few microseconds by colliding with bath gas.The relaxation rate coefficients for CH(X^(2)Π,v=0)radical in He,Ar,and N_(2)flow were obtained by time-resolved laser-induced fluorescence measurements,ranging from 10^(-12)cm^(3)·molecule^(-1)·s^(-1)to 10^(-11)cm^(3)·molecule^(-1)·s^(-1).The N_(2)flow exhibits the highest relax-ation rate for CH(X^(2)Π)radical due to its additional rovibrational levels,which allow for more efficient energy dissipation during collisions compared to monoatomic gases.The Ar flow shows a larger relaxation rate than He flow due to its greater polarizability and stronger long-range interaction with the CH(X^(2)Π)radical.展开更多
文摘本研究基于自行搭建的5 k W旋流预混火焰实验台,开展了轴向空气分级方式下CH_(4)/NH_(3)旋流预混火焰的实验测试,重点考察了分级风比例、分级风高度及分级风喷口数目对CH_(4)/NH_(3)旋流预混火焰燃烧及排放特性的影响。结果表明:随着NH_(3)占比的增大,火焰高度变长,燃烧室出口的NO排放量呈先增大后减小的趋势且在NH_(3)占比为50%达到峰值;在50%掺氨工况下采用轴向空气分级使一级燃烧室处于富燃状态可以有效降低NO的排放,其中分级风的最佳比例范围是30%~50%(当量比1.21~1.70),且随着分级风高度的增大呈下降趋势;此外,在最佳分级风比例和高度条件下(分级风高度80 mm、占比30%),增加分级风的喷口数目可减轻分级风碰撞对上游主燃区富燃状态的影响,使NO排放进一步降低。
基金supported by the National Natural Science Foundation of China(22302115,22072079)the Fundamental Research Program of Shanxi Province(202303021221056).
文摘Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Consequently,it is desired to investigate the mechanisms of the FLP-catalyzed hydrogenation of C=C and C=O and provide insight into the modification of CeO_(2)catalysts for the selective hydrogenation.In this work,the reaction mechanism of the hydrogenation of CH_(2)=CH_(2)and CH_(3)CH=O at the FLP sites constructed on CeO_(2)(110)surface was investigated by density functional theory(DFT),with the classical Lewis acid-base pairs(CLP)site as the reference.The results illustrate that at the CLP site,the dissociated hydride(H^(δ−))forms a stable H−O bond with the surface O atom,while at the FLP site,H^(δ−)is stabilized by Ce,displaying higher activity on the one hand.On the other hand,the electron cloud density of the Ce atom at the FLP site is higher,which can transfer more electrons to the adsorbed C_(C=C)and O_(C=O)atoms,leading to a higher degree of activation for C=C and C=O bonds,as indicated by the Bader charge analysis.Therefore,compared to the CLP site,the FLP site exhibits higher hydrogenation activity for CH_(2)=CH_(2)and CH_(3)CH=O.Furthermore,at the FLP sites,it demonstrates high efficiency in catalyzing the hydrogenation of CH_(2)=CH_(2)with the rate-determining barrier of 1.04 eV,but it shows limited activity for the hydrogenation of CH_(3)CH=O with the rate-determining barrier of 1.94 eV.It means that the selective hydrogenation of C=C can be effectively achieved at the FLP sites concerning selective hydrogenation catalysis.The insights shown in this work help to clarify the reaction mechanism of the hydrogenation of C=C and C=O at FLP site on CeO_(2)(110)and reveal the relationship between the catalytic performance and the nature of the active site,which is of great benefit to development of rational design of heterogeneous FLP catalysts.
文摘The aim of this paper is to explore the effect of geometrical parameters on ultimate load-carrying capacity of a circular hollow section(CHS)X-joint under axial compression of the brace end.First of all,finite element(FE)model to calculate ultimate load-carrying capacity of the CHS X-joint subjected to uniaxial load of the brace is constructed,and the calculated load–displacement curves are compared to the experimental ones.After validation of the FE model,46080 groups of FE calculation models with different geometrical parameters are generated by means of parametric modeling.Subsequently,eight variables including gusset thickness and chord thickness are set as input to predict load-carrying capacity of the CHS X-joint by four machine learning(ML)algorithms,i.e.,Generalized Regression Neural Network,Support Vector Machine,random forest(RF),and Extreme Gradient Boosting(XGBoost).Finally,the constructed ML prediction models are interpreted by SHapley Additive exPlanations,to explore the impact weight of each factor on ultimate load-carrying capacity of the joint.The results show that all the four models can predict the load-carrying capacity of the subject accurately,with all the R2 values greater than 0.97.In addition,RF model yields the minimum mean-square error,Root Mean Squared Error,Mean Absolute Error,and Mean Absolute Percentage Error values,and the greatest R2 value,while the prediction accuracy of XGBoost is relatively worse.Among all the eight considered geometrical parameters,brace diameter has the strongest impact on load-carrying capacity of the joint,followed by chord thickness,chord ring width,chord ring thickness,brace ring width,and brace thickness,while the thicknesses of the gusset plate and brace have marginal influence on load-carrying capacity.The study of the current paper can provide guidelines for dimension design of CHS X-joints.
基金supported by the National Key Research and Development Program of China(2023YFC3207904).
文摘Selective perchlorate(ClO_(4)^(−))removal from surface water is a pressing need due to the stringent perchlorate drinking water limits around the world.Herein,we anchored N^(+)–C–H hydrogen bond donors in hydrophobic cavities via interactions of cationic surfactants with montmorillonite to prioritize perchlorate bonding.The prepared adsorbent exhibited high selectivity over commonly occurring competing anions,including SO_(4)^(2−),NO_(3)^(−),PO_(4)^(3−),HCO_(3)^(−),and halide anions.High adsorption capacity,fast adsorption kinetics,and excellent regeneration ability(removal efficiency≥80%after 20 cycles)were confirmed via batch experiments.Unconventional CH···O hydrogen bonding was verified as the primary driving force for perchlorate adsorption,which relies on the higher bond energy(∼80 kcal·mol−1)than conventional bonding.The removal efficiency of anions followed the order of the Hofmeister Series,demonstrating the importance of hydrophobic cavities formed by the tail groups of cationic surfactants.The hydrophobic cavities sheltered the C–H bonds from interacting with anions of low hydration energy(e.g.,perchlorate).Furthermore,a fixed-bed column test demonstrated that about 2900 bed volumes of the feeding streams(∼500μg·L^(−1))can be treated to≤70μg·L^(−1),with an enrichment factor of 10.3.Overall,on the basis of the hydrophobicity-induced hydrogen bonding mechanism,a series of low-cost adsorbents can be synthesized and applied for specific perchlorate removal.
基金supported by the National Natural Science Foundation of China(No.22273103)the National Natural Science Foundation of China(NSFC Center for Chemical Dynamics)(No.22288201)+1 种基金Dalian Institute of Chemical Physics(DICP I202230)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(grant GJJSTD20220001)。
文摘Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were generat-ed with internal excitation by multiphoton photolysis of CHBr_(3)at 248 nm,and its rotational temperature was found to relax to the flow temperature in a few microseconds by colliding with bath gas.The relaxation rate coefficients for CH(X^(2)Π,v=0)radical in He,Ar,and N_(2)flow were obtained by time-resolved laser-induced fluorescence measurements,ranging from 10^(-12)cm^(3)·molecule^(-1)·s^(-1)to 10^(-11)cm^(3)·molecule^(-1)·s^(-1).The N_(2)flow exhibits the highest relax-ation rate for CH(X^(2)Π)radical due to its additional rovibrational levels,which allow for more efficient energy dissipation during collisions compared to monoatomic gases.The Ar flow shows a larger relaxation rate than He flow due to its greater polarizability and stronger long-range interaction with the CH(X^(2)Π)radical.
