This paper researches the performance of a novel supercritical carbon dioxide(S-CO_2) Brayton cycle and organic Rankine cycle(ORC) combined system with a theoretical solar radiation diurnal distribution. The new syste...This paper researches the performance of a novel supercritical carbon dioxide(S-CO_2) Brayton cycle and organic Rankine cycle(ORC) combined system with a theoretical solar radiation diurnal distribution. The new system supplies all solar energy to a S-CO_2 Brayton cycle heater, where heat releasing from the S-CO_2 cooler is stored in the thermal storage system which is supplied to the ORC. Therefore, solar energy is kept at a high temperature, while at the same time the thermal storage system temperature is low. This paper builds a simple solar radiation diurnal distribution model. The maximum continuous working time, mass of thermal storage material, and parameter variations of the two cycles are simulated with the solar radiation diurnal distribution model. 10 organic fluids and 5 representative thermal storage materials are compared in this paper, with the mass and volume of these materials being shown. The longer the continuous working time is, the lower the system thermal efficiency is. The maximum continuous working time can reach 19.1 hours if the system provides a constant power output. At the same time, the system efficiency can be kept above 38% for most fluids.展开更多
In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential inve...In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.展开更多
In this paper,to further improve thermodynamic performance of supercritical carbon dioxide cycle,simple/recompression transcritical carbon dioxide Brayton cycle(STBC/RTBC)and simple/recompression transcritical carbon ...In this paper,to further improve thermodynamic performance of supercritical carbon dioxide cycle,simple/recompression transcritical carbon dioxide Brayton cycle(STBC/RTBC)and simple/recompression transcritical carbon dioxide Rankine cycle(STRC/RTRC)are proposed.Thermal and exergy performance analysis and optimization for the above four transcritical CO_(2)cycles and simple/recompression supercritical cycle(SSBC/RSBC)are conducted.The effect of key thermodynamic parameters on those CO_(2)cycle performance is studied.Results indicate that the improvements of thermodynamic performance of CO_(2)cycle are obvious when transcritical Brayton and Rankine cycle are applied in it.Within the same range of optimization variables,the maximum thermal efficiency improvements of RTRC and RTBC are 4.98%and 3.6%,and maximum exergy efficiency improvements of RTRC and RTBC are 7.08%and 5.13%when compared with RSBC.Moreover,the thermodynamic performances of STBC and STRC are also outstanding than that of SSBC.This work provides a way to further improve the thermodynamic performance of CO_(2)power cycle.展开更多
Helium-xenon Brayton cycle systems have significant potential as the energy conversion system for small-scale reactors in remote land,deep-sea,and space applications due to a range of advantages,including high cycle e...Helium-xenon Brayton cycle systems have significant potential as the energy conversion system for small-scale reactors in remote land,deep-sea,and space applications due to a range of advantages,including high cycle efficiency,compact system structures,and chemical stability.The objective of this review is to provide a comprehensive understanding of the helium-xenon Brayton cycle system based on the projects and researches.First,the basic information and development history are introduced,and a series of typical designs are summarized.Then,the system configurations,cycle parameter analysis and optimization are discussed.Next,the key components are classified,such as turbine,compressor,and heat exchanger.Moreover,the dynamic processes and control strategies are introduced in different conditions.Finally,the deficiency and prospect of current research are presented.The review covers the representative helium-xenon Brayton cycle systems,which could provide a reference for promoting the development of energy conversion systems.展开更多
Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and duration.Converting the tremendous high-quali...Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and duration.Converting the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the vehicle.This paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles,including the indirect conversion of Brayton and Rankine cycles,direct conversion of thermoelectric materials,and combined conversion.For the open Brayton cycle with hydrocarbon fuel as the working fluid,the Power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few components of the system.However,its work capacity is limited by the flow rate of the supplied fuel.The closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion efficiency.The Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about 0.88.The thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power demand.This review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.展开更多
This investigation focused on the analysis of using the M-cycle （Maisotsenko cycle） to improve the efficiency of a gas turbine engine. By combining the M-cycle with an open Brayton cycle, a new cycle, is known as th...This investigation focused on the analysis of using the M-cycle （Maisotsenko cycle） to improve the efficiency of a gas turbine engine. By combining the M-cycle with an open Brayton cycle, a new cycle, is known as the MCTC （Maisotsenko combustion turbine cycle）, was formed. The MCTC used an indirect evaporative air cooler as a saturator with a gas turbine engine. The saturator was applied on the side of the turbine exhaust （M-cycle#2） in the analysis. The analysis included calculations and the development of an EES （engineering equation solver） code to model the MCTC system performance. The resulting performance curves were graphed to show the effects of several parameters on the thermal efficiency and net power output of the gas turbine engine. The models were also compared with actual experimental test that results from a gas turbine engine. Conclusions and discussions of results are also given.展开更多
Space nuclear reactor power(SNRP)using a gas-cooled reactor(GCR)and a closed Brayton cycle(CBC)is the ideal choice for future high-power space missions.To investigate the safety characteristics and develop the control...Space nuclear reactor power(SNRP)using a gas-cooled reactor(GCR)and a closed Brayton cycle(CBC)is the ideal choice for future high-power space missions.To investigate the safety characteristics and develop the control strategies for gas-cooled SNRP,transient models for GCR,energy conversion unit,pipes,heat exchangers,pump and heat pipe radiator are established and a system analysis code is developed in this paper.Then,analyses of several operation conditions are performed using this code.In full-power steady-state operation,the core hot spot of 1293 K occurs near the upper part of the core.If 0.4$reactivity is introduced into the core,the maximum temperature that the fuel can reach is 2059 K,which is 914 K lower than the fuel melting point.The system finally has the ability to achieve a new steady-state with a higher reactor power.When the GCR is shut down in an emergency,the residual heat of the reactor can be removed through the conduction of the core and radiation heat transfer.The results indicate that the designed GCR is inherently safe owing to its negative reactivity feedback and passive decay heat removal.This paper may provide valuable references for safety design and analysis of the gas-cooled SNRP coupled with CBC.展开更多
This work developed the modeling and supervisory control for gas turbine. A CTPN （continuous timed Petri Net） model of a gas turbine, using a first linear order approximation for every state of the Brayton cycle is ...This work developed the modeling and supervisory control for gas turbine. A CTPN （continuous timed Petri Net） model of a gas turbine, using a first linear order approximation for every state of the Brayton cycle is obtained. The Brayton cycle rules the functioning of a gas turbine, and it is composed by four states： compression, combustion, expansion and cooling. The principle of the gas turbine is developed by the Brayton cycle, a thermodynamic process which intervenes in the gas turbine components. The steady-state behavior of the gas turbine has been widely investigated in engineering area. Moreover, the dynamic behavior has been studied using non-linear models of its components, leading to complicated mathematical representations. The methodology of the current work begins with a simplification of the dynamical relations in every state （excepting the cooling phase） of the Brayton cycle. Temperature and pressure are modeled as first order linear systems, therefore, every system is translated into a CTPN. Furthermore, to guarantee a safety operation, an SC （supervisory controller） is designed to ensure the combustion chamber temperature is lower than 1,000 ℃. Although the model presented is extremely simplified, it will be used as a starting point to develop more complex models.展开更多
An irreversible cycle model of the quantum Bose Brayton engine is established, in which finite-time processes and irreversibilities in two adiabatic processes are taken into account. Based on the model, expressions fo...An irreversible cycle model of the quantum Bose Brayton engine is established, in which finite-time processes and irreversibilities in two adiabatic processes are taken into account. Based on the model, expressions for the power output and the efficiency are derived. By using a numerical computation, the optimal relationship between the power output and the efficiency of an irreversible Bose Brayton engine is obtained. The optimal regions of the power output and the efficiency are determined. It is found that the influences of the irreversibility and the quantum degeneracy on the main performance parameters of the Bose Brayton engine are remarkable. The results obtained in the present paper can provide some new theoretical information for the optimal design and the performance improvement of a real Brayton engine.展开更多
The performance in finite time of a quantum-mechanical Brayton engine cycle is discussed, without intro- duction of temperature. The engine model consists of two quantum isoenergetic and two quantum isobaric processes...The performance in finite time of a quantum-mechanical Brayton engine cycle is discussed, without intro- duction of temperature. The engine model consists of two quantum isoenergetic and two quantum isobaric processes, and works with a single particle in a harmonic trap. Directly employing the finite-time thermodynamics, the efficiency at maximum power output is determined. Extending the harmonic trap to a power-law trap, we find that the efficiency at max/mum power is independent of any parameter involved in the model, but depends on the confinement of the trapping potential.展开更多
We propose a quantum-mechanical Brayton engine model that works between two superposed states,employing a single particle confined in an arbitrary power-law trap as the working substance. Applying the superposition pr...We propose a quantum-mechanical Brayton engine model that works between two superposed states,employing a single particle confined in an arbitrary power-law trap as the working substance. Applying the superposition principle,we obtain the explicit expressions of the power and efficiency,and find that the efficiency at maximum power is bounded from above by the function: η+= θ/(θ+1),with θ being a potential-dependent exponent.展开更多
A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results...A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine＇s high operating load, The thermal efficiency can be as large as 24.83% under 100% olaerating load, accordingly, the net outnut nower of 14.86 kW in nhtnined展开更多
The main compressor in a supercritical carbon dioxide(SCO2)Brayton cycle works near the critical point where the physical properties of CO_(2)are far away from the ideal gas.To investigate the effectiveness of the con...The main compressor in a supercritical carbon dioxide(SCO2)Brayton cycle works near the critical point where the physical properties of CO_(2)are far away from the ideal gas.To investigate the effectiveness of the conventional one-dimensional(1D)loss models for predicting the performance of compressors working in such nontraditional conditions,detailed comparisons of 1D predicted performance,experimental data and threedimensional CFD results are made.A 1D analysis method with enthalpy and total pressure based loss system is developed for multistage SCO2 centrifugal compressors,and it is firstly validated against the experimental results of a single stage SCO2 centrifugal compressor from the Sandia National Laboratory.A good agreement of pressure ratios with experiments can be achieved by the 1D method.But the efficiency deviations reveal the potential deficiencies of the parasitic loss models.On the basis of the validation,a two-stage SCO2 centrifugal compressor is employed to do the evaluation.Three-dimensional CFD simulations are performed.Detailed comparisons are made between the CFD and the 1D results at different stations located in the compressor.The features of the deviations are analyzed in detail,as well as the reasons that might cause these deviations.展开更多
Supercritical carbon dioxide(sCO_(2))power cycle is an innovative concept for converting thermal energy to electrical energy.It uses sCO_(2)as the working fluid medium in a closed or semi-closed Brayton thermodynamic ...Supercritical carbon dioxide(sCO_(2))power cycle is an innovative concept for converting thermal energy to electrical energy.It uses sCO_(2)as the working fluid medium in a closed or semi-closed Brayton thermodynamic cycle.The sCO_(2)power cycles have several benefits such as high cycle efficiency,small equipment size and plant footprint(and therefore lower capital cost)and the potential for full carbon capture.Achieving the full benefits of the sCO_(2)cycle depends on overcoming a number of engineering and materials science challenges that impact both the technical feasibility of the cycle and its economic viability.For example,the design and construction methods of turbomachinery,recuperator and high-pressure oxy-combustor pose significant technical challenges.Other R&D needs include material selection and testing,and optimized power cycle configuration.Over the years,particularly in the last decade,R&D efforts have been growing worldwide to develop sCO_(2)cycle technologies for power generation.Significant progress has been made in developing sCO_(2)cycle power systems.Some small,low-temperature sCO_(2)Brayton cycle power systems are starting to emerge in the commercial market,and a natural gas-fired demonstration power plant using a sCO_(2)cycle called the Allam Cycle is under construction.This article describes the sCO_(2)cycles for applications in power generation from fossil fuels and reviews the recent developments in sCO_(2)power cycle technologies.展开更多
The supercritical carbon dioxide(SCO_(2))Brayton cycle has become an ideal power conversion system for sodium-cooled fast reactors(SFR)due to its high efficiency,compactness,and avoidance of sodiumwater reaction.In th...The supercritical carbon dioxide(SCO_(2))Brayton cycle has become an ideal power conversion system for sodium-cooled fast reactors(SFR)due to its high efficiency,compactness,and avoidance of sodiumwater reaction.In this paper,the 1200 MWe large pool SFR(CFR1200)is used as the heat source of the system,and the sodium circuit temperature and the heat load are the operating boundaries of the cycle system.The performance of different SCO_(2) Brayton cycle systems and changes in key equipment performance are compared.The study indicates that the inter-stage cooling and recompression cycle has the best match with the heat source characteristics of the SFR,and the cycle efficiency is the highest(40.7%).Then,based on the developed system transient analysis program(FR-Sdaso),a pool-type SFR power plant system analysis model based on the inter-stage cooling and recompression cycle is established.In addition,the matching between the inter-stage cooling recompression cycle and the SFR during the load cycle of the power plant is studied.The analysis shows that when the nuclear island adopts the flow-advanced operation strategy and the carbon dioxide flowrate in the SCO_(2) power conversion system is adjusted with the goal of maintaining the sodium-carbon dioxide heat exchanger sodium side outlet temperature unchanged,the inter-stage cooling recompression cycle can match the operation of the SFR very well.展开更多
一、概述 1.1 外位成分(extraposition)是指下面一组句子中的斜体部分: A science writer, he has a wide range of knowledge. Close to the urban areas, the commune mainly does market gardening. His eyes, penetratingly keen, s...一、概述 1.1 外位成分(extraposition)是指下面一组句子中的斜体部分: A science writer, he has a wide range of knowledge. Close to the urban areas, the commune mainly does market gardening. His eyes, penetratingly keen, seemed to be reading my mind. Brayton lay upon his stomach, dead. 1.2 外位成分的主要特点是与主语的关系相当密切,而且一般是一种所谓内包关系(intensive relation),可以用连系动词be表达。展开更多
A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established,in which the regeneration problem in two constant-magnetic field processes and the irreversibilit...A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established,in which the regeneration problem in two constant-magnetic field processes and the irreversibility in two adiabatic processes are considered synthetically.Expressions for the COP,cooling rate,power input,theminimum ratio of the two magnetic fields,etc.,are derived.It is found that the influence of the irreversibility and the regeneration on the main performance parameters of the magnetic Brayton refrigerator is remarkable.It is important that we have obtained several optimal criteria,which may provide some theoretical basis for the optimal design and operation of the Brayton refrigerator.The results obtained in the paper can provide some new theoretical information for the optimal design and performance improvement of real Brayton refrigerators.展开更多
A thermodynamic model was developed to analyze the performance of cogeneration plant based on irreversible recuperative Brayton cycle. A parameter, dimensionless total useful energy rate (DTUER), was used as the crite...A thermodynamic model was developed to analyze the performance of cogeneration plant based on irreversible recuperative Brayton cycle. A parameter, dimensionless total useful energy rate (DTUER), was used as the criterion for performance optimization of cogeneration plant. The effects of cycle parameters, internal irreversibilities, and recuperator efficiency on maximum DTUER and on the efficiency at maximum DTUER were numerically investigated. The relation between DTUER and cogeneration efficiency was also analyzed. The results show that there exists an optimal compressor pressure ratio which maximizes the DTUER. It is also found that there exists an optimal power-to-heat ratio which results in a dual-maximum DTUER.展开更多
基金financial support provided by the National Natural Science Foundation of China (Grant No. 51706181, 51806172)the Postdoctoral Science Foundation of China (Grant No. 2017M613294XB)+1 种基金Key Programs of China Huaneng Group (Grant No. HNKJ15-H07)Young Talent Programs of Shaanxi Province of China(Grant No. ZD-18-SST04)
文摘This paper researches the performance of a novel supercritical carbon dioxide(S-CO_2) Brayton cycle and organic Rankine cycle(ORC) combined system with a theoretical solar radiation diurnal distribution. The new system supplies all solar energy to a S-CO_2 Brayton cycle heater, where heat releasing from the S-CO_2 cooler is stored in the thermal storage system which is supplied to the ORC. Therefore, solar energy is kept at a high temperature, while at the same time the thermal storage system temperature is low. This paper builds a simple solar radiation diurnal distribution model. The maximum continuous working time, mass of thermal storage material, and parameter variations of the two cycles are simulated with the solar radiation diurnal distribution model. 10 organic fluids and 5 representative thermal storage materials are compared in this paper, with the mass and volume of these materials being shown. The longer the continuous working time is, the lower the system thermal efficiency is. The maximum continuous working time can reach 19.1 hours if the system provides a constant power output. At the same time, the system efficiency can be kept above 38% for most fluids.
文摘In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.
文摘In this paper,to further improve thermodynamic performance of supercritical carbon dioxide cycle,simple/recompression transcritical carbon dioxide Brayton cycle(STBC/RTBC)and simple/recompression transcritical carbon dioxide Rankine cycle(STRC/RTRC)are proposed.Thermal and exergy performance analysis and optimization for the above four transcritical CO_(2)cycles and simple/recompression supercritical cycle(SSBC/RSBC)are conducted.The effect of key thermodynamic parameters on those CO_(2)cycle performance is studied.Results indicate that the improvements of thermodynamic performance of CO_(2)cycle are obvious when transcritical Brayton and Rankine cycle are applied in it.Within the same range of optimization variables,the maximum thermal efficiency improvements of RTRC and RTBC are 4.98%and 3.6%,and maximum exergy efficiency improvements of RTRC and RTBC are 7.08%and 5.13%when compared with RSBC.Moreover,the thermodynamic performances of STBC and STRC are also outstanding than that of SSBC.This work provides a way to further improve the thermodynamic performance of CO_(2)power cycle.
基金supported by the Innovative Scientific Program of China National Nuclear Corporation(XYYLC202104)。
文摘Helium-xenon Brayton cycle systems have significant potential as the energy conversion system for small-scale reactors in remote land,deep-sea,and space applications due to a range of advantages,including high cycle efficiency,compact system structures,and chemical stability.The objective of this review is to provide a comprehensive understanding of the helium-xenon Brayton cycle system based on the projects and researches.First,the basic information and development history are introduced,and a series of typical designs are summarized.Then,the system configurations,cycle parameter analysis and optimization are discussed.Next,the key components are classified,such as turbine,compressor,and heat exchanger.Moreover,the dynamic processes and control strategies are introduced in different conditions.Finally,the deficiency and prospect of current research are presented.The review covers the representative helium-xenon Brayton cycle systems,which could provide a reference for promoting the development of energy conversion systems.
基金This paper was supported by the National Natural Science Foundation of China(No.51922060).
文摘Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and duration.Converting the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the vehicle.This paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles,including the indirect conversion of Brayton and Rankine cycles,direct conversion of thermoelectric materials,and combined conversion.For the open Brayton cycle with hydrocarbon fuel as the working fluid,the Power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few components of the system.However,its work capacity is limited by the flow rate of the supplied fuel.The closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion efficiency.The Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about 0.88.The thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power demand.This review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.
文摘This investigation focused on the analysis of using the M-cycle （Maisotsenko cycle） to improve the efficiency of a gas turbine engine. By combining the M-cycle with an open Brayton cycle, a new cycle, is known as the MCTC （Maisotsenko combustion turbine cycle）, was formed. The MCTC used an indirect evaporative air cooler as a saturator with a gas turbine engine. The saturator was applied on the side of the turbine exhaust （M-cycle#2） in the analysis. The analysis included calculations and the development of an EES （engineering equation solver） code to model the MCTC system performance. The resulting performance curves were graphed to show the effects of several parameters on the thermal efficiency and net power output of the gas turbine engine. The models were also compared with actual experimental test that results from a gas turbine engine. Conclusions and discussions of results are also given.
基金the National Natural Science Foundation of China(Grant No.U1967203)the National Key R&D Program of China(Grant No.2019YFB1901100)and China Postdoctoral Science Foundation(Grant No.2019M3737).
文摘Space nuclear reactor power(SNRP)using a gas-cooled reactor(GCR)and a closed Brayton cycle(CBC)is the ideal choice for future high-power space missions.To investigate the safety characteristics and develop the control strategies for gas-cooled SNRP,transient models for GCR,energy conversion unit,pipes,heat exchangers,pump and heat pipe radiator are established and a system analysis code is developed in this paper.Then,analyses of several operation conditions are performed using this code.In full-power steady-state operation,the core hot spot of 1293 K occurs near the upper part of the core.If 0.4$reactivity is introduced into the core,the maximum temperature that the fuel can reach is 2059 K,which is 914 K lower than the fuel melting point.The system finally has the ability to achieve a new steady-state with a higher reactor power.When the GCR is shut down in an emergency,the residual heat of the reactor can be removed through the conduction of the core and radiation heat transfer.The results indicate that the designed GCR is inherently safe owing to its negative reactivity feedback and passive decay heat removal.This paper may provide valuable references for safety design and analysis of the gas-cooled SNRP coupled with CBC.
文摘This work developed the modeling and supervisory control for gas turbine. A CTPN （continuous timed Petri Net） model of a gas turbine, using a first linear order approximation for every state of the Brayton cycle is obtained. The Brayton cycle rules the functioning of a gas turbine, and it is composed by four states： compression, combustion, expansion and cooling. The principle of the gas turbine is developed by the Brayton cycle, a thermodynamic process which intervenes in the gas turbine components. The steady-state behavior of the gas turbine has been widely investigated in engineering area. Moreover, the dynamic behavior has been studied using non-linear models of its components, leading to complicated mathematical representations. The methodology of the current work begins with a simplification of the dynamical relations in every state （excepting the cooling phase） of the Brayton cycle. Temperature and pressure are modeled as first order linear systems, therefore, every system is translated into a CTPN. Furthermore, to guarantee a safety operation, an SC （supervisory controller） is designed to ensure the combustion chamber temperature is lower than 1,000 ℃. Although the model presented is extremely simplified, it will be used as a starting point to develop more complex models.
基金Project supported by the Program for Excellent Young Teachers Foundation of Shanghai,China(Grant No.thc-20100036)
文摘An irreversible cycle model of the quantum Bose Brayton engine is established, in which finite-time processes and irreversibilities in two adiabatic processes are taken into account. Based on the model, expressions for the power output and the efficiency are derived. By using a numerical computation, the optimal relationship between the power output and the efficiency of an irreversible Bose Brayton engine is obtained. The optimal regions of the power output and the efficiency are determined. It is found that the influences of the irreversibility and the quantum degeneracy on the main performance parameters of the Bose Brayton engine are remarkable. The results obtained in the present paper can provide some new theoretical information for the optimal design and the performance improvement of a real Brayton engine.
基金Supported by the National Natural Science Foundation of China under Grant No. 11265010, the Jiangxi Provincial Natural Science Foundation under Grant No. 20132BAB212009, University Young Teacher Training Program of the SMEC under Grant No. egdll005, and by Innovation Program of the SMEC under Grant No. 12YZ177
文摘The performance in finite time of a quantum-mechanical Brayton engine cycle is discussed, without intro- duction of temperature. The engine model consists of two quantum isoenergetic and two quantum isobaric processes, and works with a single particle in a harmonic trap. Directly employing the finite-time thermodynamics, the efficiency at maximum power output is determined. Extending the harmonic trap to a power-law trap, we find that the efficiency at max/mum power is independent of any parameter involved in the model, but depends on the confinement of the trapping potential.
基金Supported by the National Natural Science Foundation of China under Grant Nos.1150509111265010+1 种基金and 11365015the Jiangxi Provincial Natural Science Foundation under Grant No.20132BAB212009
文摘We propose a quantum-mechanical Brayton engine model that works between two superposed states,employing a single particle confined in an arbitrary power-law trap as the working substance. Applying the superposition principle,we obtain the explicit expressions of the power and efficiency,and find that the efficiency at maximum power is bounded from above by the function: η+= θ/(θ+1),with θ being a potential-dependent exponent.
基金Supported by the National Basic Research Program of China("973"Program,No.2011CB707201)the National Natural Science Foundation of China(No.51206117)
文摘A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine＇s high operating load, The thermal efficiency can be as large as 24.83% under 100% olaerating load, accordingly, the net outnut nower of 14.86 kW in nhtnined
基金supported by the National Key Research and Development Program of China(No.2016YFB0600100)National Natural Science Foundation of China(No.51506195)the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning。
文摘The main compressor in a supercritical carbon dioxide(SCO2)Brayton cycle works near the critical point where the physical properties of CO_(2)are far away from the ideal gas.To investigate the effectiveness of the conventional one-dimensional(1D)loss models for predicting the performance of compressors working in such nontraditional conditions,detailed comparisons of 1D predicted performance,experimental data and threedimensional CFD results are made.A 1D analysis method with enthalpy and total pressure based loss system is developed for multistage SCO2 centrifugal compressors,and it is firstly validated against the experimental results of a single stage SCO2 centrifugal compressor from the Sandia National Laboratory.A good agreement of pressure ratios with experiments can be achieved by the 1D method.But the efficiency deviations reveal the potential deficiencies of the parasitic loss models.On the basis of the validation,a two-stage SCO2 centrifugal compressor is employed to do the evaluation.Three-dimensional CFD simulations are performed.Detailed comparisons are made between the CFD and the 1D results at different stations located in the compressor.The features of the deviations are analyzed in detail,as well as the reasons that might cause these deviations.
文摘Supercritical carbon dioxide(sCO_(2))power cycle is an innovative concept for converting thermal energy to electrical energy.It uses sCO_(2)as the working fluid medium in a closed or semi-closed Brayton thermodynamic cycle.The sCO_(2)power cycles have several benefits such as high cycle efficiency,small equipment size and plant footprint(and therefore lower capital cost)and the potential for full carbon capture.Achieving the full benefits of the sCO_(2)cycle depends on overcoming a number of engineering and materials science challenges that impact both the technical feasibility of the cycle and its economic viability.For example,the design and construction methods of turbomachinery,recuperator and high-pressure oxy-combustor pose significant technical challenges.Other R&D needs include material selection and testing,and optimized power cycle configuration.Over the years,particularly in the last decade,R&D efforts have been growing worldwide to develop sCO_(2)cycle technologies for power generation.Significant progress has been made in developing sCO_(2)cycle power systems.Some small,low-temperature sCO_(2)Brayton cycle power systems are starting to emerge in the commercial market,and a natural gas-fired demonstration power plant using a sCO_(2)cycle called the Allam Cycle is under construction.This article describes the sCO_(2)cycles for applications in power generation from fossil fuels and reviews the recent developments in sCO_(2)power cycle technologies.
基金the International Cooperative Research and Development Project on Key Technologies of the Fourth Generation Nuclear Energy System Sodium-cooled Fast Reactor(2016YFE0100800).
文摘The supercritical carbon dioxide(SCO_(2))Brayton cycle has become an ideal power conversion system for sodium-cooled fast reactors(SFR)due to its high efficiency,compactness,and avoidance of sodiumwater reaction.In this paper,the 1200 MWe large pool SFR(CFR1200)is used as the heat source of the system,and the sodium circuit temperature and the heat load are the operating boundaries of the cycle system.The performance of different SCO_(2) Brayton cycle systems and changes in key equipment performance are compared.The study indicates that the inter-stage cooling and recompression cycle has the best match with the heat source characteristics of the SFR,and the cycle efficiency is the highest(40.7%).Then,based on the developed system transient analysis program(FR-Sdaso),a pool-type SFR power plant system analysis model based on the inter-stage cooling and recompression cycle is established.In addition,the matching between the inter-stage cooling recompression cycle and the SFR during the load cycle of the power plant is studied.The analysis shows that when the nuclear island adopts the flow-advanced operation strategy and the carbon dioxide flowrate in the SCO_(2) power conversion system is adjusted with the goal of maintaining the sodium-carbon dioxide heat exchanger sodium side outlet temperature unchanged,the inter-stage cooling recompression cycle can match the operation of the SFR very well.
文摘一、概述 1.1 外位成分(extraposition)是指下面一组句子中的斜体部分: A science writer, he has a wide range of knowledge. Close to the urban areas, the commune mainly does market gardening. His eyes, penetratingly keen, seemed to be reading my mind. Brayton lay upon his stomach, dead. 1.2 外位成分的主要特点是与主语的关系相当密切,而且一般是一种所谓内包关系(intensive relation),可以用连系动词be表达。
基金supported by the Program for Excellent Young Teachers of Shanghai,China (Grant No.thc-20100036)
文摘A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established,in which the regeneration problem in two constant-magnetic field processes and the irreversibility in two adiabatic processes are considered synthetically.Expressions for the COP,cooling rate,power input,theminimum ratio of the two magnetic fields,etc.,are derived.It is found that the influence of the irreversibility and the regeneration on the main performance parameters of the magnetic Brayton refrigerator is remarkable.It is important that we have obtained several optimal criteria,which may provide some theoretical basis for the optimal design and operation of the Brayton refrigerator.The results obtained in the paper can provide some new theoretical information for the optimal design and performance improvement of real Brayton refrigerators.
基金Project(2011FJ1007-1) supported by the Funds of Key Science and Technology of Hunan Province, ChinaProject(YB2010B027)supported by the Funds for the Author of Provincial Excellent Doctoral Dissertation of Hunan Province, ChinaProject(KF200903)supported by the Opening Funds of Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal Mines, China
文摘A thermodynamic model was developed to analyze the performance of cogeneration plant based on irreversible recuperative Brayton cycle. A parameter, dimensionless total useful energy rate (DTUER), was used as the criterion for performance optimization of cogeneration plant. The effects of cycle parameters, internal irreversibilities, and recuperator efficiency on maximum DTUER and on the efficiency at maximum DTUER were numerically investigated. The relation between DTUER and cogeneration efficiency was also analyzed. The results show that there exists an optimal compressor pressure ratio which maximizes the DTUER. It is also found that there exists an optimal power-to-heat ratio which results in a dual-maximum DTUER.
