The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pc-fired furnace with multi-burner system. The development of the visualization of 3-...The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pc-fired furnace with multi-burner system. The development of the visualization of 3-D temperature distributions in pc-fired furnaces makes it possible for a new combustion control strategy directly with the furnace temperature as its goal to improve the control quality for the combustion processes. Studied in this paper is such a new strategy that the whole furnace is divided into several parts in the vertical direction, and the average temperature and its bias from the center in every cross section can be extracted from the visualization results of the 3-D temperature distributions. In the simulation stage, a computational fluid dynamics(CFD) code served to calculate the 3-D temperature distributions in a furnace, then a linear model was set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The adaptive genetic algorithm was adopted to find the optimal combination of the whole input parameters which ensure to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results showed that the strategy could soon find the factors making the temperature distribution apart from the optimal state and give correct adjusting suggestions.展开更多
The temperature-Altitude Test System(TATS) supplies various testing environments.The traditional PID method controls the temperature in TATS Temperature-Pressure Cabin(TPC) over a long adjusting time and with a large ...The temperature-Altitude Test System(TATS) supplies various testing environments.The traditional PID method controls the temperature in TATS Temperature-Pressure Cabin(TPC) over a long adjusting time and with a large overshoot.In order to solve this problem simply,a temperature control strategy with temperature difference corresponding factors is presented through a dynamic analysis and modeling of TPC temperature change.The TPC temperature descending process is simulated,and the results show that this control strategy can allot the proportion of PID heating controller and PID cooling controller in the whole control process and TPC temperature can be controlled at a set point quickly and effectively.展开更多
A finite element method(FEM) for the numerical simulation of the columnar part of the mould-temperature-control solidification(MTCS) process was presented. The latent heat was taken into account and 3D transient heat ...A finite element method(FEM) for the numerical simulation of the columnar part of the mould-temperature-control solidification(MTCS) process was presented. The latent heat was taken into account and 3D transient heat transfer analysis was carried out by using the developed FEM software. The relative errors between the numerical and experimental data are less than 6%. Three MTCS cases were computed with this method. The first case only opens the cooling channels in the bottom of the mold. The second case individually controls the separate 7 groups of cooling channels by giving 7 control points. When the temperature of a control point reaches the preset value of 400℃, the corresponding channel will be opened. The third case opens all the cooling channels at the same time. The results indicate that in the second case, the solid-liquid interface keeps near-planar. The growth velocity of the solid-liquid interface is 0.3-0.4 mm/s, which is greater than 0.1-0.3 mm/s of the first case, performing better than the others. Thus the forming quality and efficiency part interior can be improved by mold-temperature-control and the numerical model is validated. The numerical simulation of MTCS can provide an available tool for the advanced investigation on the defect improvement and the crystal’s quality.展开更多
Enzyme activity is easily influenced by temperature,resulting in accuracy decline of enzymatic detection of pesticide residues.In this study,a controller which controls the internal temperature of the pesticide residu...Enzyme activity is easily influenced by temperature,resulting in accuracy decline of enzymatic detection of pesticide residues.In this study,a controller which controls the internal temperature of the pesticide residues detector was simulated and analyzed.The mathematical model of temperature control was established by the application of the heat transfer theory.Against models with characteristics of large inertia and large hysteresis,a Smith fuzzy PID controller was proposed by combining the Smith predictor with the fuzzy PID controller.The PID controller,the fuzzy PID controller,and the Smith fuzzy PID controller were simulated in MATLAB,respectively in the same step signal given with amplitude of 1.The performance indexes(percent overshoot,settling time,and steady-state error)of various controllers were presented as follows:the PID controller(19%,250 s,0.0001),the fuzzy PID controller(11%,450 s,0.0001),and the Smith fuzzy PID controller(0%,140 s,0).From 1180 s to 1230 s,an interference signal with amplitude of 5 was added to test interference immunity.The PID controller and the fuzzy PID controller had greater fluctuations,but the Smith fuzzy PID controller had no fluctuations.The recovery time of each controller was described below:the PID controller(200 s),the fuzzy PID controller(300 s),and the Smith fuzzy PID controller(120 s).Robustness of the controller was tested by adjusting the time constant and the delay time.The performance indexes of the controllers were shown as follows:the PID controller(38%,450 s,0.0001),the fuzzy PID controller(23%,880 s,0.00025),and the Smith fuzzy PID controller(1%,150 s,0).The results of simulation showed that the performance indexes of the Smith fuzzy PID controller were better than that of the other controllers.Besides,the robustness and interference immunity are stronger than other controllers as well.The Smith fuzzy PID controller can accurately control the internal temperature of the pesticide residues detector to provide the best temperature for enzymatic detection.展开更多
Closed production systems,such as plant factories and vertical farms,have emerged to ensure a sustainable supply of fresh food,to cope with the increasing consumption of natural resource for the growing population.In ...Closed production systems,such as plant factories and vertical farms,have emerged to ensure a sustainable supply of fresh food,to cope with the increasing consumption of natural resource for the growing population.In a plant factory,a microclimate model is one of the direct control components of a whole system.In order to better realize the dynamic regulation for the microclimate model,energy-saving and consumption reduction,it is necessary to optimize the environmental parameters in the plant factory,and thereby to determine the influencing factors of atmosphere control systems.Therefore,this study aims to identify accurate microclimate models,and further to predict temperature change based on the experimental data,using the classification and regression trees(CART)algorithm.A random forest theory was used to represent the temperature control system.A mechanism model of the temperature control system was proposed to improve the performance of the plant factories.In terms of energy efficiency,the main influencing factors on temperature change in the plant factories were obtained,including the temperature and air volume flow of the temperature control device,as well as the internal relative humidity.The generalization error of the prediction model can reach 0.0907.The results demonstrated that the proposed model can present the quantitative relationship and prediction function.This study can provide a reference for the design of high-precision environmental control systems in plant factories.展开更多
Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the ...Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.展开更多
A simple two-by-two model for a boiler-turbine unit is derived in this paper, which can capture the essential dynamics of the typical process. The coordinated controller is designed based on this model. A PID control ...A simple two-by-two model for a boiler-turbine unit is derived in this paper, which can capture the essential dynamics of the typical process. The coordinated controller is designed based on this model. A PID control structure and a tuning procedure are proposed. The example shows that the method is easy to use and can achieve an acceptable performance.展开更多
As one of the key units of space CCD camera,the temperature range and stability of CCD components affect the image's indexes.Reasonable thermal design and robust thermal control devices are needed.One kind of temp...As one of the key units of space CCD camera,the temperature range and stability of CCD components affect the image's indexes.Reasonable thermal design and robust thermal control devices are needed.One kind of temperature control loop heat pipe(TCLHP) is designed,which highly meets the thermal control requirements of CCD components.In order to study the dynamic behaviors of heat and mass transfer of TCLHP,particularly in the orbital flight case,a transient numerical model is developed by using the well-established empirical correlations for flow models within three dimensional thermal modeling.The temperature control principle and details of mathematical model are presented.The model is used to study operating state,flow and heat characteristics based upon the analyses of variations of temperature,pressure and quality under different operating modes and external heat flux variations.The results indicate that TCLHP can satisfy the thermal control requirements of CCD components well,and always ensure good temperature stability and uniformity.By comparison between flight data and simulated results,it is found that the model is to be accurate to within 1℃.The model can be better used for predicting and understanding the transient performance of TCLHP.展开更多
In this paper,an online tracking simulation system for the 660 MW ultra-supercritical circulating fluidized bed(USCFB)boiler is established,and a tracking simulation test is conducted for the cold start-up process of ...In this paper,an online tracking simulation system for the 660 MW ultra-supercritical circulating fluidized bed(USCFB)boiler is established,and a tracking simulation test is conducted for the cold start-up process of the boiler.The system comprises two parts:the USCFB boiler model and a tracking mechanism based on sliding mode control algorithm.The USCFB boiler model includes a water-steam system,an air-flue gas system,a material supply system,and an ash circulation system.The online tracking simulation system receives the same control signal as the plant and runs synchronously in digital space.The tracking mechanism updates model parameters to eliminate deviations between simulation values and measured values.The SMC-based multi-input,multi-output algorithm is based on a state-space model,providing two distinct advantages.Firstly,it enables more efficient elimination of deviations;secondly,it exhibits robustness against uncertainties associated with simulation model behavior and measurement noise.Finally,this paper conducts tracking simulation research on the cold start-up process of the boiler.展开更多
Heat conduction in single-walled carbon nanotubes (SWCNTs) has been investigated by using various methods, while less work has been focused on multi-walled carbon nanotubes (MWCNTs). The thermal conductivities of ...Heat conduction in single-walled carbon nanotubes (SWCNTs) has been investigated by using various methods, while less work has been focused on multi-walled carbon nanotubes (MWCNTs). The thermal conductivities of the double-walled carbon nanotubes (DWCNTs) with two different temperature control methods are studied by using molecular dynamics (MD) simulations. One case is that the heat baths (HBs) are imposed only on the outer wall, while the other is that the HBs are imposed on both the two walls. The results show that the ratio of the thermal conductivity of DWCNTs in the first case to that in the second case is inversely proportional to the ratio of the cross-sectional area of the DWCNT to that of its outer wall. In order to interpret the results and explore the heat conduction mechanisms, the inter-wall thermal transport of DWCNTs is simulated. Analyses of the temperature profiles of a DWCNT and its two walls in the two cases and the inter- wall thermal resistance show that in the first case heat is almost transported only along the outer wall, while in the second case a DWCNT behaves like parallel heat transport channels in which heat is transported along each wall independently. This gives a good explanation of our results and presents the heat conduction mechanisms of MWCNTs.展开更多
As the pivotal test equipment of aero-engines design,finalization,improvement,modification,etc.,the Altitude Ground Test Facilities(AGTF)plays an important role in the research and development of the aero-engines.With...As the pivotal test equipment of aero-engines design,finalization,improvement,modification,etc.,the Altitude Ground Test Facilities(AGTF)plays an important role in the research and development of the aero-engines.With the rapid development of advanced high-performance aeroengine,the increasing demand of high-altitude simulation test is driving AGTF to improve its test ability and level of automation and intelligence.The modeling method,simulation tool,and control technology are the key factors to support the improvement of the AGTF control system.The main purpose of this paper is to provide an overview of modeling methods,simulation tools,and control technologies in AGTF control system for future research.First,it reviews the evolution of AGTF in the world,from the early formative stage to integration stage.Then,the mathematical modeling method of AGTF for control application is overviewed.Furthermore,the simulation tools used in the AGTF control system are overviewed from numerical simulation to hardware-in-loop simulation and further to semi-physical simulation.Meanwhile,the control technologies used in the AGTF control system are summarized from single-variable control to multivariable integrated control,and from classical control theory to modern control theory.Finally,recommendations for future research are outlined.Therefore,this review article provides extensive literature information for the modeling,simulation,and control design of AGTF for control application.展开更多
In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging proc...In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging process,the paper designs a hardware-in-loop simulation of twin-screw extruder experiment system which is closer to scene,low cost and high safety.The system through the establishment of twin-screw extruder’s mathematical model on computer to simulate the realistic system and there is hardware practicality in the computer simulation loop.The hardware based on C8051F020 can operate in the simulation loop in real time.In computer software design, we desigh man-machine interface that is intuitive and easy to operate,can reflect twin-screw extruder main operation information vividly.Finally,twin-screw extruder’s 3 heater temperature mathematical model and PID incremental control algorithm are presented.展开更多
After steam discharge in heavy oil reservoirs,the distribution of temperature,pressure,and permeability in different wells becomes irregular.Flow channels can easily be produced,which affect the sweep efficiency of th...After steam discharge in heavy oil reservoirs,the distribution of temperature,pressure,and permeability in different wells becomes irregular.Flow channels can easily be produced,which affect the sweep efficiency of the oil displacement.Previous studies have shown that the salting-out plugging method can effectively block these channels in high-temperature reservoirs,improve the suction profile,and increase oil production.In the present study,the optimal dosage of the plugging agent is determined taking into account connection transmissibility and inter-well volumes.Together with the connectivity model,a water flooding simulation model is introduced.Moreover,a non-gradient stochastic disturbance algorithm is used to obtain the optimal plugging agent dosage,which provides the basis for the high-temperature salting-out plugging agent adjustment in the field.展开更多
Flue gas heat loss accounts for a significant component of theoverall heat loss for coal-fired boilers in power plants. The flue gas absorbsmore heat as the exhaust gas temperature rises, which reduces boiler efficien...Flue gas heat loss accounts for a significant component of theoverall heat loss for coal-fired boilers in power plants. The flue gas absorbsmore heat as the exhaust gas temperature rises, which reduces boiler efficiencyand raises coal consumption. Additionally, if the exhaust gas temperatureis too high, a lot of water must be used to cool the flue gas for the wetflue gas desulfurization system to function well, which has an impact onthe power plant’s ability to operate profitably. It is consequently vital totake steps to lower exhaust gas temperatures in order to increase boilerefficiency and decrease the amount of coal and water used. Desulfurizationperformance may be enhanced and water use can be decreased by reasonableflue gas characteristics at the entry. This study analyzed the unit’s energyconsumption, investment, and coal savings while proposing four couplingstrategies for regulating flue gas temperature and waste heat recovery. Agraded flue gas conditioning and waste heat recovery plan was presentedunder the condition of ensuring high desulfurization efficiency, along withthe notion of minimizing energy loss owing to energy inflow temperaturedifference. Numerical results show that the proposed methods improved thesystem performance and reduced the water consumption and regulated theboiler temperature.展开更多
Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of s...Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of semiconductor refrigeration and establishes a heat transfer model. Semiconductor cooler on piping refrigeration is simulated,and influence of the parameters on the outlet temperature,such as pipe pressure difference of inlet and outlet,pipe length,pipe radius,are gotten,and then hydraulic tank semiconductor refrigeration system is proposed. The semiconductor refrigeration system can control temperature at 37 ± 1°C.展开更多
A novel pressure and vacuum continuous control system, which adopts a hybrid pump as pressure and vacuum source, is presented. The mathematical model of the system is developed. The theoretical simulation and analysis...A novel pressure and vacuum continuous control system, which adopts a hybrid pump as pressure and vacuum source, is presented. The mathematical model of the system is developed. The theoretical simulation and analysis on the system are implemented in order to study the relationships among the characteristics, parameters and working points of the system. The experimental investigations on the system characteristics are presented with the adoption ofa fuzzy-PID controller. The simulation and experimental results indicate that the pressure and vacuum continuous control system based on hybrid pump has good dynamic and static performance, strong robustness and satisfactory adaptability to various system parameters. According to the results, system can successfully gain high accuracy and fast response signal. Also, the mathematical model of system is also testified by the experimental results.展开更多
文摘The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pc-fired furnace with multi-burner system. The development of the visualization of 3-D temperature distributions in pc-fired furnaces makes it possible for a new combustion control strategy directly with the furnace temperature as its goal to improve the control quality for the combustion processes. Studied in this paper is such a new strategy that the whole furnace is divided into several parts in the vertical direction, and the average temperature and its bias from the center in every cross section can be extracted from the visualization results of the 3-D temperature distributions. In the simulation stage, a computational fluid dynamics(CFD) code served to calculate the 3-D temperature distributions in a furnace, then a linear model was set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The adaptive genetic algorithm was adopted to find the optimal combination of the whole input parameters which ensure to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results showed that the strategy could soon find the factors making the temperature distribution apart from the optimal state and give correct adjusting suggestions.
文摘The temperature-Altitude Test System(TATS) supplies various testing environments.The traditional PID method controls the temperature in TATS Temperature-Pressure Cabin(TPC) over a long adjusting time and with a large overshoot.In order to solve this problem simply,a temperature control strategy with temperature difference corresponding factors is presented through a dynamic analysis and modeling of TPC temperature change.The TPC temperature descending process is simulated,and the results show that this control strategy can allot the proportion of PID heating controller and PID cooling controller in the whole control process and TPC temperature can be controlled at a set point quickly and effectively.
文摘A finite element method(FEM) for the numerical simulation of the columnar part of the mould-temperature-control solidification(MTCS) process was presented. The latent heat was taken into account and 3D transient heat transfer analysis was carried out by using the developed FEM software. The relative errors between the numerical and experimental data are less than 6%. Three MTCS cases were computed with this method. The first case only opens the cooling channels in the bottom of the mold. The second case individually controls the separate 7 groups of cooling channels by giving 7 control points. When the temperature of a control point reaches the preset value of 400℃, the corresponding channel will be opened. The third case opens all the cooling channels at the same time. The results indicate that in the second case, the solid-liquid interface keeps near-planar. The growth velocity of the solid-liquid interface is 0.3-0.4 mm/s, which is greater than 0.1-0.3 mm/s of the first case, performing better than the others. Thus the forming quality and efficiency part interior can be improved by mold-temperature-control and the numerical model is validated. The numerical simulation of MTCS can provide an available tool for the advanced investigation on the defect improvement and the crystal’s quality.
基金supported by the National Natural Science Fund Project(31471413)Project A funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)+2 种基金Natural Science Fund Project of Jiangsu Province(BK20141165)China Postdoctoral Science Foundation funded project(2014M561594)Jiangsu Planned Projects for Postdoctoral Research Funds(1401175C).
文摘Enzyme activity is easily influenced by temperature,resulting in accuracy decline of enzymatic detection of pesticide residues.In this study,a controller which controls the internal temperature of the pesticide residues detector was simulated and analyzed.The mathematical model of temperature control was established by the application of the heat transfer theory.Against models with characteristics of large inertia and large hysteresis,a Smith fuzzy PID controller was proposed by combining the Smith predictor with the fuzzy PID controller.The PID controller,the fuzzy PID controller,and the Smith fuzzy PID controller were simulated in MATLAB,respectively in the same step signal given with amplitude of 1.The performance indexes(percent overshoot,settling time,and steady-state error)of various controllers were presented as follows:the PID controller(19%,250 s,0.0001),the fuzzy PID controller(11%,450 s,0.0001),and the Smith fuzzy PID controller(0%,140 s,0).From 1180 s to 1230 s,an interference signal with amplitude of 5 was added to test interference immunity.The PID controller and the fuzzy PID controller had greater fluctuations,but the Smith fuzzy PID controller had no fluctuations.The recovery time of each controller was described below:the PID controller(200 s),the fuzzy PID controller(300 s),and the Smith fuzzy PID controller(120 s).Robustness of the controller was tested by adjusting the time constant and the delay time.The performance indexes of the controllers were shown as follows:the PID controller(38%,450 s,0.0001),the fuzzy PID controller(23%,880 s,0.00025),and the Smith fuzzy PID controller(1%,150 s,0).The results of simulation showed that the performance indexes of the Smith fuzzy PID controller were better than that of the other controllers.Besides,the robustness and interference immunity are stronger than other controllers as well.The Smith fuzzy PID controller can accurately control the internal temperature of the pesticide residues detector to provide the best temperature for enzymatic detection.
文摘Closed production systems,such as plant factories and vertical farms,have emerged to ensure a sustainable supply of fresh food,to cope with the increasing consumption of natural resource for the growing population.In a plant factory,a microclimate model is one of the direct control components of a whole system.In order to better realize the dynamic regulation for the microclimate model,energy-saving and consumption reduction,it is necessary to optimize the environmental parameters in the plant factory,and thereby to determine the influencing factors of atmosphere control systems.Therefore,this study aims to identify accurate microclimate models,and further to predict temperature change based on the experimental data,using the classification and regression trees(CART)algorithm.A random forest theory was used to represent the temperature control system.A mechanism model of the temperature control system was proposed to improve the performance of the plant factories.In terms of energy efficiency,the main influencing factors on temperature change in the plant factories were obtained,including the temperature and air volume flow of the temperature control device,as well as the internal relative humidity.The generalization error of the prediction model can reach 0.0907.The results demonstrated that the proposed model can present the quantitative relationship and prediction function.This study can provide a reference for the design of high-precision environmental control systems in plant factories.
基金supported by National Key Research Development Planning Project of China (2004CB619108).
文摘Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.
基金Supported by Specialized Research Fund for the Doctoral Program of Higher Education (20020079007)
文摘A simple two-by-two model for a boiler-turbine unit is derived in this paper, which can capture the essential dynamics of the typical process. The coordinated controller is designed based on this model. A PID control structure and a tuning procedure are proposed. The example shows that the method is easy to use and can achieve an acceptable performance.
文摘As one of the key units of space CCD camera,the temperature range and stability of CCD components affect the image's indexes.Reasonable thermal design and robust thermal control devices are needed.One kind of temperature control loop heat pipe(TCLHP) is designed,which highly meets the thermal control requirements of CCD components.In order to study the dynamic behaviors of heat and mass transfer of TCLHP,particularly in the orbital flight case,a transient numerical model is developed by using the well-established empirical correlations for flow models within three dimensional thermal modeling.The temperature control principle and details of mathematical model are presented.The model is used to study operating state,flow and heat characteristics based upon the analyses of variations of temperature,pressure and quality under different operating modes and external heat flux variations.The results indicate that TCLHP can satisfy the thermal control requirements of CCD components well,and always ensure good temperature stability and uniformity.By comparison between flight data and simulated results,it is found that the model is to be accurate to within 1℃.The model can be better used for predicting and understanding the transient performance of TCLHP.
文摘In this paper,an online tracking simulation system for the 660 MW ultra-supercritical circulating fluidized bed(USCFB)boiler is established,and a tracking simulation test is conducted for the cold start-up process of the boiler.The system comprises two parts:the USCFB boiler model and a tracking mechanism based on sliding mode control algorithm.The USCFB boiler model includes a water-steam system,an air-flue gas system,a material supply system,and an ash circulation system.The online tracking simulation system receives the same control signal as the plant and runs synchronously in digital space.The tracking mechanism updates model parameters to eliminate deviations between simulation values and measured values.The SMC-based multi-input,multi-output algorithm is based on a state-space model,providing two distinct advantages.Firstly,it enables more efficient elimination of deviations;secondly,it exhibits robustness against uncertainties associated with simulation model behavior and measurement noise.Finally,this paper conducts tracking simulation research on the cold start-up process of the boiler.
基金supported by the National Natural Science Foundation of China(Grant Nos.51322603,51136001,and 51356001)the Program for New Century Excellent Talents in University,Science Fund for Creative Research Groups of China(Grant No.51321002)the Initiative Scientific Research Program of Tsinghua University,China
文摘Heat conduction in single-walled carbon nanotubes (SWCNTs) has been investigated by using various methods, while less work has been focused on multi-walled carbon nanotubes (MWCNTs). The thermal conductivities of the double-walled carbon nanotubes (DWCNTs) with two different temperature control methods are studied by using molecular dynamics (MD) simulations. One case is that the heat baths (HBs) are imposed only on the outer wall, while the other is that the HBs are imposed on both the two walls. The results show that the ratio of the thermal conductivity of DWCNTs in the first case to that in the second case is inversely proportional to the ratio of the cross-sectional area of the DWCNT to that of its outer wall. In order to interpret the results and explore the heat conduction mechanisms, the inter-wall thermal transport of DWCNTs is simulated. Analyses of the temperature profiles of a DWCNT and its two walls in the two cases and the inter- wall thermal resistance show that in the first case heat is almost transported only along the outer wall, while in the second case a DWCNT behaves like parallel heat transport channels in which heat is transported along each wall independently. This gives a good explanation of our results and presents the heat conduction mechanisms of MWCNTs.
基金This study was co-supported by the National Science and Technology Major Project,China(No.J2019-V-0010-0104)Zhejiang Provincial Natural Science Foundation of China(No.LQ23E060007).
文摘As the pivotal test equipment of aero-engines design,finalization,improvement,modification,etc.,the Altitude Ground Test Facilities(AGTF)plays an important role in the research and development of the aero-engines.With the rapid development of advanced high-performance aeroengine,the increasing demand of high-altitude simulation test is driving AGTF to improve its test ability and level of automation and intelligence.The modeling method,simulation tool,and control technology are the key factors to support the improvement of the AGTF control system.The main purpose of this paper is to provide an overview of modeling methods,simulation tools,and control technologies in AGTF control system for future research.First,it reviews the evolution of AGTF in the world,from the early formative stage to integration stage.Then,the mathematical modeling method of AGTF for control application is overviewed.Furthermore,the simulation tools used in the AGTF control system are overviewed from numerical simulation to hardware-in-loop simulation and further to semi-physical simulation.Meanwhile,the control technologies used in the AGTF control system are summarized from single-variable control to multivariable integrated control,and from classical control theory to modern control theory.Finally,recommendations for future research are outlined.Therefore,this review article provides extensive literature information for the modeling,simulation,and control design of AGTF for control application.
文摘In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging process,the paper designs a hardware-in-loop simulation of twin-screw extruder experiment system which is closer to scene,low cost and high safety.The system through the establishment of twin-screw extruder’s mathematical model on computer to simulate the realistic system and there is hardware practicality in the computer simulation loop.The hardware based on C8051F020 can operate in the simulation loop in real time.In computer software design, we desigh man-machine interface that is intuitive and easy to operate,can reflect twin-screw extruder main operation information vividly.Finally,twin-screw extruder’s 3 heater temperature mathematical model and PID incremental control algorithm are presented.
基金supported by China Postdoctoral Science Foundation(No.2021M702304)Shandong Provincial Natural Science Foundation Youth Fund(No.ZR2021QE260).
文摘After steam discharge in heavy oil reservoirs,the distribution of temperature,pressure,and permeability in different wells becomes irregular.Flow channels can easily be produced,which affect the sweep efficiency of the oil displacement.Previous studies have shown that the salting-out plugging method can effectively block these channels in high-temperature reservoirs,improve the suction profile,and increase oil production.In the present study,the optimal dosage of the plugging agent is determined taking into account connection transmissibility and inter-well volumes.Together with the connectivity model,a water flooding simulation model is introduced.Moreover,a non-gradient stochastic disturbance algorithm is used to obtain the optimal plugging agent dosage,which provides the basis for the high-temperature salting-out plugging agent adjustment in the field.
文摘Flue gas heat loss accounts for a significant component of theoverall heat loss for coal-fired boilers in power plants. The flue gas absorbsmore heat as the exhaust gas temperature rises, which reduces boiler efficiencyand raises coal consumption. Additionally, if the exhaust gas temperatureis too high, a lot of water must be used to cool the flue gas for the wetflue gas desulfurization system to function well, which has an impact onthe power plant’s ability to operate profitably. It is consequently vital totake steps to lower exhaust gas temperatures in order to increase boilerefficiency and decrease the amount of coal and water used. Desulfurizationperformance may be enhanced and water use can be decreased by reasonableflue gas characteristics at the entry. This study analyzed the unit’s energyconsumption, investment, and coal savings while proposing four couplingstrategies for regulating flue gas temperature and waste heat recovery. Agraded flue gas conditioning and waste heat recovery plan was presentedunder the condition of ensuring high desulfurization efficiency, along withthe notion of minimizing energy loss owing to energy inflow temperaturedifference. Numerical results show that the proposed methods improved thesystem performance and reduced the water consumption and regulated theboiler temperature.
基金Supported by the National Natural Science Foundation of China(No.51175448,51405424)
文摘Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of semiconductor refrigeration and establishes a heat transfer model. Semiconductor cooler on piping refrigeration is simulated,and influence of the parameters on the outlet temperature,such as pipe pressure difference of inlet and outlet,pipe length,pipe radius,are gotten,and then hydraulic tank semiconductor refrigeration system is proposed. The semiconductor refrigeration system can control temperature at 37 ± 1°C.
基金This project is supported by National Natural Science Foundation of China (No.50675075).
文摘A novel pressure and vacuum continuous control system, which adopts a hybrid pump as pressure and vacuum source, is presented. The mathematical model of the system is developed. The theoretical simulation and analysis on the system are implemented in order to study the relationships among the characteristics, parameters and working points of the system. The experimental investigations on the system characteristics are presented with the adoption ofa fuzzy-PID controller. The simulation and experimental results indicate that the pressure and vacuum continuous control system based on hybrid pump has good dynamic and static performance, strong robustness and satisfactory adaptability to various system parameters. According to the results, system can successfully gain high accuracy and fast response signal. Also, the mathematical model of system is also testified by the experimental results.