Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature ...Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature system of USC unit.Closed-loop SMI is applied to building step response model of the unit directly.The parameters selection method is proposed to deal with the parameter sensitivity and improve the reliability of the model.Finally,the model is used in model identification of real USC unit.展开更多
The regenerative cooling technology is a promising approach for effective thermal protection of propulsion and power-generation systems.A mathematical model has been used to examine fluid flows and heat transfer of th...The regenerative cooling technology is a promising approach for effective thermal protection of propulsion and power-generation systems.A mathematical model has been used to examine fluid flows and heat transfer of the aviation kerosene RP-3 with endothermic fuel pyrolysis at a supercritical pressure of 5 MPa.A pyrolytic reaction mechanism,which consists of 18 species and 24 elementary reactions,is incorporated to account for fuel pyrolysis.Detailed model validations are conducted against a series of experimental data,including fluid temperature,fuel conversion rate,various product yields,and chemical heat sink,fully verifying the accuracy and reliability of the model.Effects of fuel pyrolysis and inlet flow velocity on flow dynamics and heat transfer characteristics of RP-3 are investigated.Results reveal that the endothermic fuel pyrolysis significantly improves the heat transfer process in the high fluid temperature region.During the supercritical-pressure heat transfer process,the flow velocity significantly increases,caused by the drastic variations of thermophysical properties.Under all the tested conditions,the Nusselt number initially increases,consistent with the increased flow velocity,and then slightly decreases in the high fluid temperature region,mainly owing to the decreased heat absorption rate from the endothermic pyrolytic chemical reactions.展开更多
A general, green and efficient method for the synthesis of trans diiodoalkenes in CO 2(sc) has been developed. Trans diiodoalkenes were obtained stereospecifically in quantitative yields via diiodination of...A general, green and efficient method for the synthesis of trans diiodoalkenes in CO 2(sc) has been developed. Trans diiodoalkenes were obtained stereospecifically in quantitative yields via diiodination of both electron rich and electron deficient alkynes in the presence of KI, Ce(SO 4) 2 and water in supercritical carbon dioxide [CO 2 (sc)] at 40 ℃.展开更多
A good understanding of the thermophysical properties of hydrocarbon fuels at supercritical pressure is important to research on experiment and numerical simulation of fuel supercritical spray.Experimental measurement...A good understanding of the thermophysical properties of hydrocarbon fuels at supercritical pressure is important to research on experiment and numerical simulation of fuel supercritical spray.Experimental measurements are difficult to conduct directly because of the extremely high pressure and high temperature.In this study,back propagation(BP)neural network,BP optimized by mind evolution algorithm(MEA-BP)and BP neural network optimized by genetic algorithm(GA-BP)are established to determine the nonlinear temperature-dependent thermophysical properties of density,viscosity,and isobaric specific heat(C_(2))of hydrocarbon fuels at supercritical pressure.Meanwhile,approximate formulas for these properties prediction are primarily proposed using polynomial fitting.In this paper,models that can predict three types of physical properties of three kinds of hydrocarbon fuels and their mixtures in a wide temperature range under supercritical pressure are established.In the prediction of density and C_(2),BP neural network has a good prediction effect.The results show that the MAPE is lower than 2%in the prediction of density and C_(2),but the MAPE of viscosity prediction is slightly higher than 5%using BP.Furthermore,MEA and GA are used to optimize the prediction of viscosity.The optimization effect and computation of the MEA is better than that of GA because MEA does not have the local optimization and prematurity problems.The present work offers an efficient tool to predict the thermophysical properties of hydrocarbon fuels over a wide range of temperatures under supercritical pressure which can be easily extended to other fuels of interest.It will be beneficial to the experiment and numerical simulation studies of supercritical sprays.展开更多
基金National Natural Science Foundation of China(No.60974119)
文摘Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature system of USC unit.Closed-loop SMI is applied to building step response model of the unit directly.The parameters selection method is proposed to deal with the parameter sensitivity and improve the reliability of the model.Finally,the model is used in model identification of real USC unit.
基金This work was supported by the Zhejiang Provincial Natural Science Foundation of China(R1100300)the National Natural Science Foundation of China(11372277).
文摘The regenerative cooling technology is a promising approach for effective thermal protection of propulsion and power-generation systems.A mathematical model has been used to examine fluid flows and heat transfer of the aviation kerosene RP-3 with endothermic fuel pyrolysis at a supercritical pressure of 5 MPa.A pyrolytic reaction mechanism,which consists of 18 species and 24 elementary reactions,is incorporated to account for fuel pyrolysis.Detailed model validations are conducted against a series of experimental data,including fluid temperature,fuel conversion rate,various product yields,and chemical heat sink,fully verifying the accuracy and reliability of the model.Effects of fuel pyrolysis and inlet flow velocity on flow dynamics and heat transfer characteristics of RP-3 are investigated.Results reveal that the endothermic fuel pyrolysis significantly improves the heat transfer process in the high fluid temperature region.During the supercritical-pressure heat transfer process,the flow velocity significantly increases,caused by the drastic variations of thermophysical properties.Under all the tested conditions,the Nusselt number initially increases,consistent with the increased flow velocity,and then slightly decreases in the high fluid temperature region,mainly owing to the decreased heat absorption rate from the endothermic pyrolytic chemical reactions.
文摘目的:通过在超临界CO2色谱上测定CO2流动相密度与全反式番茄红素组分峰面积的相关性,推算二氧化碳密度变化对全反式番茄红素的吸光系数(A1cm)的影响。方法:超临界色谱条件:色谱柱:Diamonsil C8(250mm×4.6m m,5μm);检测波长:4 5 3 n m;压力变化范围:1 1.5～1 7.5 M P a;温度变化范围:3 5～5 5℃;流速:2mL/min;进样量:20μL。结果:全反式番茄红素组分在超临界CO2中最大吸收波长处的峰面积是可变的,与CO2密度呈线性正相关。结论:可推断全反式番茄红素吸光系数与超临界CO2流体密度变化呈正相关。
文摘A general, green and efficient method for the synthesis of trans diiodoalkenes in CO 2(sc) has been developed. Trans diiodoalkenes were obtained stereospecifically in quantitative yields via diiodination of both electron rich and electron deficient alkynes in the presence of KI, Ce(SO 4) 2 and water in supercritical carbon dioxide [CO 2 (sc)] at 40 ℃.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51922076 and 91941102)
文摘A good understanding of the thermophysical properties of hydrocarbon fuels at supercritical pressure is important to research on experiment and numerical simulation of fuel supercritical spray.Experimental measurements are difficult to conduct directly because of the extremely high pressure and high temperature.In this study,back propagation(BP)neural network,BP optimized by mind evolution algorithm(MEA-BP)and BP neural network optimized by genetic algorithm(GA-BP)are established to determine the nonlinear temperature-dependent thermophysical properties of density,viscosity,and isobaric specific heat(C_(2))of hydrocarbon fuels at supercritical pressure.Meanwhile,approximate formulas for these properties prediction are primarily proposed using polynomial fitting.In this paper,models that can predict three types of physical properties of three kinds of hydrocarbon fuels and their mixtures in a wide temperature range under supercritical pressure are established.In the prediction of density and C_(2),BP neural network has a good prediction effect.The results show that the MAPE is lower than 2%in the prediction of density and C_(2),but the MAPE of viscosity prediction is slightly higher than 5%using BP.Furthermore,MEA and GA are used to optimize the prediction of viscosity.The optimization effect and computation of the MEA is better than that of GA because MEA does not have the local optimization and prematurity problems.The present work offers an efficient tool to predict the thermophysical properties of hydrocarbon fuels over a wide range of temperatures under supercritical pressure which can be easily extended to other fuels of interest.It will be beneficial to the experiment and numerical simulation studies of supercritical sprays.
