The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its ther...The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its thermodynamic properties make it a fluid of choice in the efficient use of energy at low and medium temperatures in engine cycles. However, the performance of transcritical CO2 cycles weakens under high temperature and pressure conditions, especially in refrigeration systems;On the other hand, this disadvantage becomes rather interesting in engine cycles where CO2 can be used as an alternative to the organic working fluid in small and medium-sized electrical systems for low quality or waste heat sources. In order to improve the performance of systems operating with CO2 in the field of refrigeration and electricity production, research has made it possible to develop several concepts, of which this article deals with a review of the state of the art, followed by analyzes in-depth and critical of the various developments to the most recent modifications in these fields. Detailed discussions on the performance and technical characteristics of the different evolutions are also highlighted as well as the factors affecting the overall performance of the systems studied. Finally, perspectives on the future development of the use of CO2 in these different cycles are presented.展开更多
A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The...A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.展开更多
Low critical temperature limits the application of CO_2 trans-critical power cycle.The binary mixture of R290/CO_2has higher critical temperature.Using mixture fluid may solve the problem that subcritical CO_2 is hard...Low critical temperature limits the application of CO_2 trans-critical power cycle.The binary mixture of R290/CO_2has higher critical temperature.Using mixture fluid may solve the problem that subcritical CO_2 is hardly condensed by conventional cooling water.In this article,theoretical analysis is executed to study the performance of the zeotropic mixture for trans-critical power cycle using low-grade liquid heat source with temperature of200℃.The results indicated that the problem that CO_2 can't be condensed in power cycle by conventional cooling water can be solved by mixing R290 to CO_2.Variation trend of outlet temperature of thermal oil in supercritical heater with heating pressure is determined by the composition of the mixture fluid.Gliding temperature causes the maximum outlet temperature of cooling water with the increase of mass fraction of R290.There are the maximum values for cycle thermal efficiency and net power output with the increase of supercritical heating pressure.展开更多
提出了一种SATA固态硬盘Power Cycle功能自动化测试方法,用于验证SATA固态硬盘在上下电过程中数据完整性与安全性,保证SATA固态硬盘在多种应用场景中都可以保持正常且高效的运行状态.通过分析标准SATA协议与ATA命令集协议,针对SATA固态...提出了一种SATA固态硬盘Power Cycle功能自动化测试方法,用于验证SATA固态硬盘在上下电过程中数据完整性与安全性,保证SATA固态硬盘在多种应用场景中都可以保持正常且高效的运行状态.通过分析标准SATA协议与ATA命令集协议,针对SATA固态硬盘Power Cycle工作流程,在DriveMaster和ULink Power Hub软硬件平台基础上进行脚本编程,对SATA固态硬盘Power Cycle功能进行自动化测试.测试方法包含基于标准协议提炼出的测试流程图,软件平台DriveMaster脚本编程和DriveMaster平台与ULink Power Hub硬件组件联动设置,待测硬盘运行状况记录,发生异常时运行环境记录,测试结果汇总等内容.为满足用户对SATA固态硬盘使用需求,测试过程在经典用例"写入数据-下电-上电-读回比较"基础上,为SATA固态硬盘制造多种不同写入压力,模拟SATA固态硬盘真实使用场景,从厂商角度保证SATA固态硬盘中数据完整性以及正确性.展开更多
The Wiener index of a graph is defined to be the sum of the distances of all pairs of vertices in the graph.The kth power G^(k) of a graph G is the graph on V(G)and two vertices are adjacent if and only if their dista...The Wiener index of a graph is defined to be the sum of the distances of all pairs of vertices in the graph.The kth power G^(k) of a graph G is the graph on V(G)and two vertices are adjacent if and only if their distance in G is less or equal to k.In this paper,we computed the Wiener index of the kth power of paths and cycles for any k≥2.展开更多
The supercritical CO_(2)Brayton cycle has potential to be used in electricity generation occasions with its advantages of high efficiency and compact structure.Focusing on a so-called self-condensing CO_(2)transcritic...The supercritical CO_(2)Brayton cycle has potential to be used in electricity generation occasions with its advantages of high efficiency and compact structure.Focusing on a so-called self-condensing CO_(2)transcritical power cycle,a model was established and four different layouts of heat recuperation process were analyzed,a without-recuperation cycle,a post-recuperation cycle,a pre-recuperation cycle and a re-recuperation cycle.The results showed that the internal normal cycle's share of the whole cycle increases with increasing the cooling pressure and decreasing the final cooled temperature.Heat load in the supercritical heater decreases with increasing the cooling pressure.From perspective of performance,the re-recuperation cycle and the pre-recuperation cycle have similar thermal efficiency which is much higher than other two layouts.Both thermal efficiency and net power output have a maximum value with the cooling pressure,except in the condition with the final cooled temperature of 31℃.Considering both the complexity and the economy,the pre-recuperation cycle is more applicable than the other options.Under 35℃of the final cooled temperature,the thermal efficiency of the pre-recuperation cycle reaches the peak 0.34 with the cooling pressure of 8.4 MPa and the maximum net power output is 2355.24 kW at 8.2 MPa of the cooling pressure.展开更多
To meet the escalating electricity demand and rising fuel costs,along with notable losses in power transmission,exploring alternative solutions is imperative.Gas turbines demonstrate high efficiency under ideal Intern...To meet the escalating electricity demand and rising fuel costs,along with notable losses in power transmission,exploring alternative solutions is imperative.Gas turbines demonstrate high efficiency under ideal International Organization for Standardization(ISO)conditions but face challenges during summer when ambient temperatures reach 40℃.To enhance performance,the proposal suggests cooling inlet air by 15℃using a vapor absorption chiller(VAC),utilizing residual exhaust gases from a combined cycle power plant(CCPP)to maximize power output.Additionally,diverting a portion of exhaust gases to drive an organic Rankine cycle(ORC)for supplementary power generation offers added efficiency.This integrated approach not only boosts power output but alsominimizes environmental impact by repurposing exhaust gases for additional operations.This study presents a detailed energy and economic analysis of a modified combine cycle power plant,in Kotri,Pakistan.R600A is used as organic fuel for the ORC while LiBr-H2O solution is used for the VAC.Two performance parameters,efficiency and energy utilization factor,Four energetic parameters,Work output of ORC,modified CCPP,original CCPP and cooling rate,and one economics parameter,payback period were examined under varying ambient conditions and mass fraction of exhaust gases from outlet of a gas turbine(ψ).A parametric investigation was conducted within the temperature range of 18℃to 50℃,relative humidity between 70%and 90%,and theψranging from 0 to 0.3.The findings reveal that under elevated ambient conditions(40℃,90%humidity)withψat 0,the Energy Utilization Factor(EUF)exceeds 60%.However,the ORC exhibits a low work output of 100KWalongside a high cooling load of 29,000 kW.Conversely,the modified system demonstrates an augmented work output of approximately 81,850 KWcompared to the original system’s 78,500KW.Furthermore,the integration of this systemproves advantageous across all metrics.Additionally,the payback period of the system is contingent on ambient conditions,with lower conditions correlating to shorter payback periods and vice versa.展开更多
The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used i...The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used in this ammonia-water based cycle. Energy analysis and parametric analysis are performed to guide the theoretical performance and experimental investigation is done to verify the theoretical results. The results show that the generator pressure, heating source temperature and turbine outlet depressurization made by the ejector can affect the cycle performances. Besides, the experimental thermal efficiency is much lower than the theoretical one on account of the heat losses and irreversibility. Moreover, the performance of liquid-gas ejector is affected by primary flow pressure and temperature.展开更多
To meet the requirements of strict fuel consumption and emission limits,continuously increasing the thermal efficiency of an internal combustion engine and decreasing its exhaust emissions are the main challenges to i...To meet the requirements of strict fuel consumption and emission limits,continuously increasing the thermal efficiency of an internal combustion engine and decreasing its exhaust emissions are the main challenges to its sustainable development within the automotive industry.Considering the competition with other zero-emission powertrain systems,such as vehicle batteries and fuel cells,the development of the internal combustion engine needs to focus on producing higher efficiency and zero emissions to meet the request of CO_(2) reduction.This paper introduces two novel concepts for an internal combustion engine featuring high efficiency and zero emissions.Referred to as the argon power cycle engine fueled with either hydrogen or natural gas within an oxygen–argon mixture,its fundamentals and characteristics are expounded.This includes a method necessary to absorb carbon dioxide when natural gas is used as fuel instead of hydrogen.展开更多
Increasing efficiency and reducing emissions are fundamental approaches to achieving peak carbon emissions and carbon neutrality for the transportation and power industries.The Argon power cycle(APC)is a novel concept...Increasing efficiency and reducing emissions are fundamental approaches to achieving peak carbon emissions and carbon neutrality for the transportation and power industries.The Argon power cycle(APC)is a novel concept for high efficiency and zero emissions.However,APC faces the challenges of severe knock and low power density at high efficiency.To elevate efficiency and power density simultaneously of APC,the Miller cycle is applied and combined with APC.The calculation method is based on a modification of the previous thermodynamic method.The mixture of hydrogen and oxygen is controlled in the stoichiometric ratio.The results indicate that to obtain a thermal conversion efficiency of 70%,in the Otto cycle,the compression ratio and the AR(argon molar ratio in the argon-oxygen mixture)could be 9 and 95%,respectively.In comparison,for the Miller cycle,these two parameters only need to be 7 and 91%.A lower compression ratio can reduce the negative effect of knock,and a reduced AR increases the power density by 66%with the same efficiency.The improvement effect is significant when the expansion-compression ratio is 1.5.Meanwhile,increasing the expansion-compression ratio is more effective in the argon-oxygen mixture than in the nitrogen–oxygen mixture.For the next-generation Argon/Miller power cycle engine,the feasible design to achieve the indicated thermal efficiency of 58.6%should be a compression ratio of 11,an expansion-compression ratio of 1.5,and an AR of 91%.展开更多
Research on applying a supercritical carbon dioxide power cycle （S-CO2） to concentrating solar power （CSP） instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is s...Research on applying a supercritical carbon dioxide power cycle （S-CO2） to concentrating solar power （CSP） instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is suitable for CSP owing to its compactness, higher efficiency, and dry-cooling capability. At the Korea Institute of Energy Research （KIER）, to implement an S-CO2 system, a 10 kWe class test loop with a turbine- alternator-compressor （TAC） using gas foil bearings was developed. A basic sub-kWe class test loop with a high- speed radial type turbo-generator and a test loop with a capability of tens of kWe with an axial type turbo- generator were then developed. To solve the technical bottleneck of S-CO2 turbomachinery, a partial admission nozzle and oil-lubrication bearings were used in the turbo- generators. To experience the closed-power cycle and develop an operational strategy of S-CO2 operated at high pressure, an organic Rankine cycle （ORC） operating test using a refrigerant as the working fluid was conducted owing to its operational capability at relatively low- pressure conditions of approximately 30 to 40 bar. By operating the sub-kWe class test loop using R134a as the working fluid instead of CO2, an average turbine power of 400 W was obtained.展开更多
The CO_(2)power cycle(CPC)system is an efficient and environmentally friendly method for waste heat recovery(WHR).However,the traditional design and optimization process of a CPC system is very complex and timeconsumi...The CO_(2)power cycle(CPC)system is an efficient and environmentally friendly method for waste heat recovery(WHR).However,the traditional design and optimization process of a CPC system is very complex and timeconsuming.This paper proposes a novel goal-oriented design method based on machine-learning methods for quickly designing an optimized CPC system with given performance indicators.And taking the design of the CO_(2)transcritical power cycle(CTPC)system for internal combustion engines(ICEs)as an example.Firstly,the net output power and the total cost of the system prediction models are trained by simulated data.Then the multiobjective optimization of the system is carried out by using the genetic algorithm coupled with the prediction models,and the optimization results are used to train a classification model.Finally,the given target indicators are input into the classification model for goal-oriented designing and getting the optimal configuration.The results of the goal-oriented design validation show that the goal-oriented design method can design the CTPC system well.And,once the classification model is trained,the CTPC system’s future goal-oriented design process only needs to be calculated once,significantly reducing design time.In conclusion,the goal-oriented design method based on machine-learning proposed is a novel and promising method.This is a technology that combines computer science and energy science and can provide users with a quick and reliable CPC system design method.展开更多
This paper briefs the configuration and performance of large size gas turbines and their composed combined cycle power plants designed and produced by four large renown gas turbine manufacturing firms in the world, pr...This paper briefs the configuration and performance of large size gas turbines and their composed combined cycle power plants designed and produced by four large renown gas turbine manufacturing firms in the world, providing reference for the relevant sectors and enterprises in importing advanced gas turbines and technologies.展开更多
To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net p...To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.展开更多
Yuan Jianglei has an amazing story to tell. The 27 year old is one of a handful of people who can say they have cycled through Africa - solo.Yuan began his epic adventure in the West African country of Benin, ending 1...Yuan Jianglei has an amazing story to tell. The 27 year old is one of a handful of people who can say they have cycled through Africa - solo.Yuan began his epic adventure in the West African country of Benin, ending 10,544 km and 333 days later in his hometown of Ningbo, east China＇s Zhejiang Province.展开更多
Concentrated solar power(CSP)plants with thermal energy storage(TES)system are emerging as one kind of the most promising power plants in the future renewable energy system,since they can supply dispatchable and low-c...Concentrated solar power(CSP)plants with thermal energy storage(TES)system are emerging as one kind of the most promising power plants in the future renewable energy system,since they can supply dispatchable and low-cost electricity with abundant but intermittent solar energy.In order to significantly reduce the levelized cost of electricity(LCOE)of the present commercial CSP plants,the next generation CSP technology with higher process temperature and energy efficiency is being developed.The TES system in the next generation CSP plants works with new TES materials at higher temperatures(>565℃)compared to that with the commercial nitrate salt mixtures.This paper reviews recent progressin research and development of the next generation CSP and TES technology.Emphasis is given on theadvanced'TES technology based on molten chloride salt mixtures such as MgCl_(2)/NaCl/KCl which hassimilar thermo-physical properties as the commercial nitrate salt mixtures,higher thermal stability(>800℃),and lower costs(<0.35USD·kg^(-1)).Recent progress in the selection/optimization of chloridesalts,determination of molten chloride salt properties,and corrosion control of construction materials(eg.,alloys)in molten chlorides is reviewed.展开更多
The insulated gate bipolar transistor(IGBT)module is one of the most age-affected components in the switch power supply, and its reliability prediction is conducive to timely troubleshooting and reduction in safety ri...The insulated gate bipolar transistor(IGBT)module is one of the most age-affected components in the switch power supply, and its reliability prediction is conducive to timely troubleshooting and reduction in safety risks and unnecessary costs. The pulsed current pattern of the accelerator power supply is different from other converter applications;therefore, this study proposed a lifetime estimation method for IGBT modules in pulsed power supplies for accelerator magnets. The proposed methodology was based on junction temperature calculations using square-wave loss discretization and thermal modeling.Comparison results showed that the junction temperature error between the simulation and IR measurements was less than 3%. An AC power cycling test under real pulsed power supply applications was performed via offline wearout monitoring of the tested power IGBT module. After combining the IGBT4 PC curve and fitting the test results,a simple corrected lifetime model was developed to quantitatively evaluate the lifetime of the IGBT module,which can be employed for the accelerator pulsed power supply in engineering. This method can be applied to other IGBT modules and pulsed power supplies.展开更多
Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely ...Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely applied because of the high power density of supercapacitors. In this study, we design a hybrid powertrain system containing two porous carbon electrode-based supercapacitor modules in parallel and one lithium ion battery pack. With the construction of the testing station, the performance and stability of the used supercapacitor modules are investigated in correlation with the structure of the supercapacitor and the nature of the electrode materials applied. It has been shown that the responding time for voltage vibration from 20 V to 48.5 V during charging or discharging process decreases from about 490 s to 94 s with the increase in applied current from 20 A to 100 A. The capacitance of the capacitor modules is nearly independent on the applied current. With the designed setup, the energy efficiency can reach as high as 0.99. The results described here provide a guidance for material selection of supercapacitors and optimized controlling strategy for hybrid power system applied in electric vehicles.展开更多
The absorption cycle is a promising technology for harnessing low-temperature heat,playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality.As a significant element in distributed ene...The absorption cycle is a promising technology for harnessing low-temperature heat,playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality.As a significant element in distributed energy systems,the absorption cycle can utilize various types of low-grade heat to fulfill cooling,heating,and electrical energy demands.Therefore,it can be employed in diverse settings to unleash its substantial energy-saving potential.However,the widespread adoption of the absorption cycle is limited to specific scenarios.Hence,further efforts are needed to enhance its technological maturity,gain societal acceptance,and expand its application scope.Focusing on the utilization of different low-grade heat,this paper provides an overview of significant advancements in the application research of various absorption cycles,such as the absorption refrigeration cycle,absorption heat pump,absorption heat transformer,and the absorption power cycle.According to current research,absorption cycles play a critical role in energy conservation and reducing carbon dioxide emissions.They can be applied to waste heat recovery,heating,drying,energy storage,seawater desalination,refrigeration,dehumidification,and power generation,leading to substantial economic benefits.The paper also outlines the primary challenges in the current application of the absorption cycle and discusses its future development direction.Ultimately,this paper serves as a reference for the application research of the absorption cycle and aims to maximize its potential in achieving global carbon neutrality.展开更多
The starting point for the pressurization process of a supercritical CO_(2) Brayton cycle is near the critical point, which may lead to a liquid hammer if the inlet pressure fluctuates. It is important to judge whethe...The starting point for the pressurization process of a supercritical CO_(2) Brayton cycle is near the critical point, which may lead to a liquid hammer if the inlet pressure fluctuates. It is important to judge whether the phase change of working fluid occurs during the pressurization process. With CO_(2) as the working fluid, the pressurization process for a centrifugal pressurization component is attention considered and analyzed. Specifying the inlet temperature, inlet pressure and outlet pressure as 32℃, 7.4 MPa and 24 MPa, respectively, the thermodynamic parameters of key state points of a centrifugal pressurization component are obtained. At the entrance of the impeller, a phase change of CO_(2) may occur, especially when the inlet points are close to the critical point. A method using enthalpy difference and exergy difference to express the possibility CO_(2) phase change is proposed. Furthermore, the risk degree of CO_(2) phase change is represented visibly. In view of the power consumption and efficiency of compressors under different working conditions, the changes of power consumption, isentropic efficiency and internal efficiency of compression components were analyzed under the conditions of constant outlet pressure and constant pressurization ratio. The power consumption is affected by the specific volume of the working fluid and the pressure difference. With the same inlet conditions, the isentropic efficiency under constant pressurization ratio is higher than that under a constant outlet pressure due to the lower power consumption;the internal efficiency is higher than the isentropic efficiency, and the trend is similar. This method can contribute to the setting of safe conditions for pressurization components.展开更多
文摘The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its thermodynamic properties make it a fluid of choice in the efficient use of energy at low and medium temperatures in engine cycles. However, the performance of transcritical CO2 cycles weakens under high temperature and pressure conditions, especially in refrigeration systems;On the other hand, this disadvantage becomes rather interesting in engine cycles where CO2 can be used as an alternative to the organic working fluid in small and medium-sized electrical systems for low quality or waste heat sources. In order to improve the performance of systems operating with CO2 in the field of refrigeration and electricity production, research has made it possible to develop several concepts, of which this article deals with a review of the state of the art, followed by analyzes in-depth and critical of the various developments to the most recent modifications in these fields. Detailed discussions on the performance and technical characteristics of the different evolutions are also highlighted as well as the factors affecting the overall performance of the systems studied. Finally, perspectives on the future development of the use of CO2 in these different cycles are presented.
基金Project(50976022) supported by the National Natural Science Foundation of ChinaProject(BY2011155) supported by Science and Technology Innovation and Transformation of Achievements of Special Fund of Jiangsu Province, China
文摘A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.
基金Project 51306198 supported by the National Natural Science Foundation of China
文摘Low critical temperature limits the application of CO_2 trans-critical power cycle.The binary mixture of R290/CO_2has higher critical temperature.Using mixture fluid may solve the problem that subcritical CO_2 is hardly condensed by conventional cooling water.In this article,theoretical analysis is executed to study the performance of the zeotropic mixture for trans-critical power cycle using low-grade liquid heat source with temperature of200℃.The results indicated that the problem that CO_2 can't be condensed in power cycle by conventional cooling water can be solved by mixing R290 to CO_2.Variation trend of outlet temperature of thermal oil in supercritical heater with heating pressure is determined by the composition of the mixture fluid.Gliding temperature causes the maximum outlet temperature of cooling water with the increase of mass fraction of R290.There are the maximum values for cycle thermal efficiency and net power output with the increase of supercritical heating pressure.
文摘提出了一种SATA固态硬盘Power Cycle功能自动化测试方法,用于验证SATA固态硬盘在上下电过程中数据完整性与安全性,保证SATA固态硬盘在多种应用场景中都可以保持正常且高效的运行状态.通过分析标准SATA协议与ATA命令集协议,针对SATA固态硬盘Power Cycle工作流程,在DriveMaster和ULink Power Hub软硬件平台基础上进行脚本编程,对SATA固态硬盘Power Cycle功能进行自动化测试.测试方法包含基于标准协议提炼出的测试流程图,软件平台DriveMaster脚本编程和DriveMaster平台与ULink Power Hub硬件组件联动设置,待测硬盘运行状况记录,发生异常时运行环境记录,测试结果汇总等内容.为满足用户对SATA固态硬盘使用需求,测试过程在经典用例"写入数据-下电-上电-读回比较"基础上,为SATA固态硬盘制造多种不同写入压力,模拟SATA固态硬盘真实使用场景,从厂商角度保证SATA固态硬盘中数据完整性以及正确性.
基金Supported by National Natural Science Foundation of China(Grant No.12201471)the Special Foundation in Key Fields for Universities of Guangdong Province(Grant No.2022ZDZX1034).
文摘The Wiener index of a graph is defined to be the sum of the distances of all pairs of vertices in the graph.The kth power G^(k) of a graph G is the graph on V(G)and two vertices are adjacent if and only if their distance in G is less or equal to k.In this paper,we computed the Wiener index of the kth power of paths and cycles for any k≥2.
基金Projects 51776215 and 12372237 supported by National Natural Science Foundation of China。
文摘The supercritical CO_(2)Brayton cycle has potential to be used in electricity generation occasions with its advantages of high efficiency and compact structure.Focusing on a so-called self-condensing CO_(2)transcritical power cycle,a model was established and four different layouts of heat recuperation process were analyzed,a without-recuperation cycle,a post-recuperation cycle,a pre-recuperation cycle and a re-recuperation cycle.The results showed that the internal normal cycle's share of the whole cycle increases with increasing the cooling pressure and decreasing the final cooled temperature.Heat load in the supercritical heater decreases with increasing the cooling pressure.From perspective of performance,the re-recuperation cycle and the pre-recuperation cycle have similar thermal efficiency which is much higher than other two layouts.Both thermal efficiency and net power output have a maximum value with the cooling pressure,except in the condition with the final cooled temperature of 31℃.Considering both the complexity and the economy,the pre-recuperation cycle is more applicable than the other options.Under 35℃of the final cooled temperature,the thermal efficiency of the pre-recuperation cycle reaches the peak 0.34 with the cooling pressure of 8.4 MPa and the maximum net power output is 2355.24 kW at 8.2 MPa of the cooling pressure.
文摘To meet the escalating electricity demand and rising fuel costs,along with notable losses in power transmission,exploring alternative solutions is imperative.Gas turbines demonstrate high efficiency under ideal International Organization for Standardization(ISO)conditions but face challenges during summer when ambient temperatures reach 40℃.To enhance performance,the proposal suggests cooling inlet air by 15℃using a vapor absorption chiller(VAC),utilizing residual exhaust gases from a combined cycle power plant(CCPP)to maximize power output.Additionally,diverting a portion of exhaust gases to drive an organic Rankine cycle(ORC)for supplementary power generation offers added efficiency.This integrated approach not only boosts power output but alsominimizes environmental impact by repurposing exhaust gases for additional operations.This study presents a detailed energy and economic analysis of a modified combine cycle power plant,in Kotri,Pakistan.R600A is used as organic fuel for the ORC while LiBr-H2O solution is used for the VAC.Two performance parameters,efficiency and energy utilization factor,Four energetic parameters,Work output of ORC,modified CCPP,original CCPP and cooling rate,and one economics parameter,payback period were examined under varying ambient conditions and mass fraction of exhaust gases from outlet of a gas turbine(ψ).A parametric investigation was conducted within the temperature range of 18℃to 50℃,relative humidity between 70%and 90%,and theψranging from 0 to 0.3.The findings reveal that under elevated ambient conditions(40℃,90%humidity)withψat 0,the Energy Utilization Factor(EUF)exceeds 60%.However,the ORC exhibits a low work output of 100KWalongside a high cooling load of 29,000 kW.Conversely,the modified system demonstrates an augmented work output of approximately 81,850 KWcompared to the original system’s 78,500KW.Furthermore,the integration of this systemproves advantageous across all metrics.Additionally,the payback period of the system is contingent on ambient conditions,with lower conditions correlating to shorter payback periods and vice versa.
基金supported by the National Natural Science Foundation of China (Grant No. 51076146)
文摘The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used in this ammonia-water based cycle. Energy analysis and parametric analysis are performed to guide the theoretical performance and experimental investigation is done to verify the theoretical results. The results show that the generator pressure, heating source temperature and turbine outlet depressurization made by the ejector can affect the cycle performances. Besides, the experimental thermal efficiency is much lower than the theoretical one on account of the heat losses and irreversibility. Moreover, the performance of liquid-gas ejector is affected by primary flow pressure and temperature.
基金The authors thank the National Natural Science Foundation of China(51576164)R&D Center of FAW and CDHK KSPG Professorship Chair Funds on Argon Power Cycle Engine Stud-ies.
文摘To meet the requirements of strict fuel consumption and emission limits,continuously increasing the thermal efficiency of an internal combustion engine and decreasing its exhaust emissions are the main challenges to its sustainable development within the automotive industry.Considering the competition with other zero-emission powertrain systems,such as vehicle batteries and fuel cells,the development of the internal combustion engine needs to focus on producing higher efficiency and zero emissions to meet the request of CO_(2) reduction.This paper introduces two novel concepts for an internal combustion engine featuring high efficiency and zero emissions.Referred to as the argon power cycle engine fueled with either hydrogen or natural gas within an oxygen–argon mixture,its fundamentals and characteristics are expounded.This includes a method necessary to absorb carbon dioxide when natural gas is used as fuel instead of hydrogen.
基金supported by the Natural Science Foundation of China(No.51576141)the Shanghai Science and Technology Program(No.22ZR1463000)。
文摘Increasing efficiency and reducing emissions are fundamental approaches to achieving peak carbon emissions and carbon neutrality for the transportation and power industries.The Argon power cycle(APC)is a novel concept for high efficiency and zero emissions.However,APC faces the challenges of severe knock and low power density at high efficiency.To elevate efficiency and power density simultaneously of APC,the Miller cycle is applied and combined with APC.The calculation method is based on a modification of the previous thermodynamic method.The mixture of hydrogen and oxygen is controlled in the stoichiometric ratio.The results indicate that to obtain a thermal conversion efficiency of 70%,in the Otto cycle,the compression ratio and the AR(argon molar ratio in the argon-oxygen mixture)could be 9 and 95%,respectively.In comparison,for the Miller cycle,these two parameters only need to be 7 and 91%.A lower compression ratio can reduce the negative effect of knock,and a reduced AR increases the power density by 66%with the same efficiency.The improvement effect is significant when the expansion-compression ratio is 1.5.Meanwhile,increasing the expansion-compression ratio is more effective in the argon-oxygen mixture than in the nitrogen–oxygen mixture.For the next-generation Argon/Miller power cycle engine,the feasible design to achieve the indicated thermal efficiency of 58.6%should be a compression ratio of 11,an expansion-compression ratio of 1.5,and an AR of 91%.
文摘Research on applying a supercritical carbon dioxide power cycle （S-CO2） to concentrating solar power （CSP） instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is suitable for CSP owing to its compactness, higher efficiency, and dry-cooling capability. At the Korea Institute of Energy Research （KIER）, to implement an S-CO2 system, a 10 kWe class test loop with a turbine- alternator-compressor （TAC） using gas foil bearings was developed. A basic sub-kWe class test loop with a high- speed radial type turbo-generator and a test loop with a capability of tens of kWe with an axial type turbo- generator were then developed. To solve the technical bottleneck of S-CO2 turbomachinery, a partial admission nozzle and oil-lubrication bearings were used in the turbo- generators. To experience the closed-power cycle and develop an operational strategy of S-CO2 operated at high pressure, an organic Rankine cycle （ORC） operating test using a refrigerant as the working fluid was conducted owing to its operational capability at relatively low- pressure conditions of approximately 30 to 40 bar. By operating the sub-kWe class test loop using R134a as the working fluid instead of CO2, an average turbine power of 400 W was obtained.
基金supported by the National Key R&D Program of China(2022YFE0100100).
文摘The CO_(2)power cycle(CPC)system is an efficient and environmentally friendly method for waste heat recovery(WHR).However,the traditional design and optimization process of a CPC system is very complex and timeconsuming.This paper proposes a novel goal-oriented design method based on machine-learning methods for quickly designing an optimized CPC system with given performance indicators.And taking the design of the CO_(2)transcritical power cycle(CTPC)system for internal combustion engines(ICEs)as an example.Firstly,the net output power and the total cost of the system prediction models are trained by simulated data.Then the multiobjective optimization of the system is carried out by using the genetic algorithm coupled with the prediction models,and the optimization results are used to train a classification model.Finally,the given target indicators are input into the classification model for goal-oriented designing and getting the optimal configuration.The results of the goal-oriented design validation show that the goal-oriented design method can design the CTPC system well.And,once the classification model is trained,the CTPC system’s future goal-oriented design process only needs to be calculated once,significantly reducing design time.In conclusion,the goal-oriented design method based on machine-learning proposed is a novel and promising method.This is a technology that combines computer science and energy science and can provide users with a quick and reliable CPC system design method.
文摘This paper briefs the configuration and performance of large size gas turbines and their composed combined cycle power plants designed and produced by four large renown gas turbine manufacturing firms in the world, providing reference for the relevant sectors and enterprises in importing advanced gas turbines and technologies.
基金Projects(U0937604,50876116)supported by the National Natural Science Foundation of ChinaProjects(2010QZZD0107,2014zzts192)supported by the Fundamental Research Funds for the Central Universities of China
文摘To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.
文摘Yuan Jianglei has an amazing story to tell. The 27 year old is one of a handful of people who can say they have cycled through Africa - solo.Yuan began his epic adventure in the West African country of Benin, ending 10,544 km and 333 days later in his hometown of Ningbo, east China＇s Zhejiang Province.
文摘Concentrated solar power(CSP)plants with thermal energy storage(TES)system are emerging as one kind of the most promising power plants in the future renewable energy system,since they can supply dispatchable and low-cost electricity with abundant but intermittent solar energy.In order to significantly reduce the levelized cost of electricity(LCOE)of the present commercial CSP plants,the next generation CSP technology with higher process temperature and energy efficiency is being developed.The TES system in the next generation CSP plants works with new TES materials at higher temperatures(>565℃)compared to that with the commercial nitrate salt mixtures.This paper reviews recent progressin research and development of the next generation CSP and TES technology.Emphasis is given on theadvanced'TES technology based on molten chloride salt mixtures such as MgCl_(2)/NaCl/KCl which hassimilar thermo-physical properties as the commercial nitrate salt mixtures,higher thermal stability(>800℃),and lower costs(<0.35USD·kg^(-1)).Recent progress in the selection/optimization of chloridesalts,determination of molten chloride salt properties,and corrosion control of construction materials(eg.,alloys)in molten chlorides is reviewed.
基金supported by the National Key Research and Development Program of China (No. 2019YFA0405402)。
文摘The insulated gate bipolar transistor(IGBT)module is one of the most age-affected components in the switch power supply, and its reliability prediction is conducive to timely troubleshooting and reduction in safety risks and unnecessary costs. The pulsed current pattern of the accelerator power supply is different from other converter applications;therefore, this study proposed a lifetime estimation method for IGBT modules in pulsed power supplies for accelerator magnets. The proposed methodology was based on junction temperature calculations using square-wave loss discretization and thermal modeling.Comparison results showed that the junction temperature error between the simulation and IR measurements was less than 3%. An AC power cycling test under real pulsed power supply applications was performed via offline wearout monitoring of the tested power IGBT module. After combining the IGBT4 PC curve and fitting the test results,a simple corrected lifetime model was developed to quantitatively evaluate the lifetime of the IGBT module,which can be employed for the accelerator pulsed power supply in engineering. This method can be applied to other IGBT modules and pulsed power supplies.
基金Funded by the National Key Basic Research Development Program of China(973 Plan)(No.2013CB632505)the National Natural Science Foundation of China(51477125)the Scientific Research Foundation for the Returned Overseas Chinese Scholars
文摘Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely applied because of the high power density of supercapacitors. In this study, we design a hybrid powertrain system containing two porous carbon electrode-based supercapacitor modules in parallel and one lithium ion battery pack. With the construction of the testing station, the performance and stability of the used supercapacitor modules are investigated in correlation with the structure of the supercapacitor and the nature of the electrode materials applied. It has been shown that the responding time for voltage vibration from 20 V to 48.5 V during charging or discharging process decreases from about 490 s to 94 s with the increase in applied current from 20 A to 100 A. The capacitance of the capacitor modules is nearly independent on the applied current. With the designed setup, the energy efficiency can reach as high as 0.99. The results described here provide a guidance for material selection of supercapacitors and optimized controlling strategy for hybrid power system applied in electric vehicles.
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA0400000)the National Key R&D Program of China(Grant No.2023YFB4005404)+1 种基金the National Natural Science Foundation of China(Grant No.52241601)the R&D Program of Institute of New Energy Dongguan(Grant No.2025-ZDBS-01)。
文摘The absorption cycle is a promising technology for harnessing low-temperature heat,playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality.As a significant element in distributed energy systems,the absorption cycle can utilize various types of low-grade heat to fulfill cooling,heating,and electrical energy demands.Therefore,it can be employed in diverse settings to unleash its substantial energy-saving potential.However,the widespread adoption of the absorption cycle is limited to specific scenarios.Hence,further efforts are needed to enhance its technological maturity,gain societal acceptance,and expand its application scope.Focusing on the utilization of different low-grade heat,this paper provides an overview of significant advancements in the application research of various absorption cycles,such as the absorption refrigeration cycle,absorption heat pump,absorption heat transformer,and the absorption power cycle.According to current research,absorption cycles play a critical role in energy conservation and reducing carbon dioxide emissions.They can be applied to waste heat recovery,heating,drying,energy storage,seawater desalination,refrigeration,dehumidification,and power generation,leading to substantial economic benefits.The paper also outlines the primary challenges in the current application of the absorption cycle and discusses its future development direction.Ultimately,this paper serves as a reference for the application research of the absorption cycle and aims to maximize its potential in achieving global carbon neutrality.
基金Projects (51776215 and 12372237) supported by National Natural Science Foundation of China.
文摘The starting point for the pressurization process of a supercritical CO_(2) Brayton cycle is near the critical point, which may lead to a liquid hammer if the inlet pressure fluctuates. It is important to judge whether the phase change of working fluid occurs during the pressurization process. With CO_(2) as the working fluid, the pressurization process for a centrifugal pressurization component is attention considered and analyzed. Specifying the inlet temperature, inlet pressure and outlet pressure as 32℃, 7.4 MPa and 24 MPa, respectively, the thermodynamic parameters of key state points of a centrifugal pressurization component are obtained. At the entrance of the impeller, a phase change of CO_(2) may occur, especially when the inlet points are close to the critical point. A method using enthalpy difference and exergy difference to express the possibility CO_(2) phase change is proposed. Furthermore, the risk degree of CO_(2) phase change is represented visibly. In view of the power consumption and efficiency of compressors under different working conditions, the changes of power consumption, isentropic efficiency and internal efficiency of compression components were analyzed under the conditions of constant outlet pressure and constant pressurization ratio. The power consumption is affected by the specific volume of the working fluid and the pressure difference. With the same inlet conditions, the isentropic efficiency under constant pressurization ratio is higher than that under a constant outlet pressure due to the lower power consumption;the internal efficiency is higher than the isentropic efficiency, and the trend is similar. This method can contribute to the setting of safe conditions for pressurization components.
