Amidst the global push for decarbonization,solar-powered Organic Rankine Cycle(SORC)systems are gaining significant attention.The small-scale Organic Rankine Cycle(ORC)systems have enhanced environmental adaptability,...Amidst the global push for decarbonization,solar-powered Organic Rankine Cycle(SORC)systems are gaining significant attention.The small-scale Organic Rankine Cycle(ORC)systems have enhanced environmental adaptability,improved system flexibility,and achieved diversification of application scenarios.However,the power consumption ratio of the working fluid pump becomes significantly larger relative to the total power output of the system,adversely impacting overall system efficiency.This study introduces an innovative approach by incorporating a vapor-liquid ejector into the ORC system to reduce the pump work consumption within the ORC.The thermoeconomic models for both the traditional ORC and an ORC integrated with a vapor-liquid ejector driven by solar parabolic trough collectors(PTCs)were developed.Key evaluation indicators,such as thermal efficiency,exergy efficiency,specific investment cost,and levelized cost of energy,were employed to compare the SORC with the solar ejector organic Rankine cycle(SEORC).Additionally,the study explores the effects of solar beam radiation intensity,PTC temperature variation,evaporator pinch point temperature difference,and condenser pinch point temperature difference on the thermo-economic performance of both systems.Results demonstrate that SEORC consistently outperforms SORC.Higher solar radiation intensity and increased PTC inlet temperature lead to better system efficiency.Moreover,there is an optimal PTC temperature drop where both thermal and exergy efficiencies are maximized.The influence of evaporator and condenser temperature pinches on system performance is found to be inconsistent.展开更多
The so-called organic Rankine cycle(ORC)is an effective technology allowing heat recovery from lower temperature sources.In the present study,to improve its thermal efficiency,a preheated ejector using exhaust steam c...The so-called organic Rankine cycle(ORC)is an effective technology allowing heat recovery from lower temperature sources.In the present study,to improve its thermal efficiency,a preheated ejector using exhaust steam coming from the expander is integrated in the cycle(EPORC).Considering net power output,pump power,and thermal efficiency,the proposed system is compared with the basic ORC.The influence of the ejector ratio(ER)of the preheated ejector on the system performances is also investigated.Results show that the net power output of the EPORC is higher than that of the basic ORC due to the decreasing pump power.Under given working conditions,the average thermal efficiency of EPORC is 29%higher than that of ORC.The ER has a great impact on the performance of EPORC by adjusting the working fluid fed to the pump,leading to significant variations of the pump work Moreover,the ER has a remarkable effect on the working fluid temperature lift(TL)at the evaporator inlet,thus reducing the evaporator heat load.According to the results,the thermal efficiency of EPORC increases by 30%,when the ER increases from 0.05 to 0.4.展开更多
Three-dimensional numerical computation of the flow fields and pumping performances for the lobed mixer-ejector are conducted using full Navier-Stokes equations. In the computation, the inlet of the primary flow uses ...Three-dimensional numerical computation of the flow fields and pumping performances for the lobed mixer-ejector are conducted using full Navier-Stokes equations. In the computation, the inlet of the primary flow uses the mass flowrate boundary condition. The inlet of the second flow and the outlet of the mixing flow use the pressure boundary condition. Compared with the relative experimental resuits, it is shown that the present calculation is reasonable. And a series of numerical studies is performed to obtain the effects of area ratio and length-to-diameter ratio of mixing duct on pumping coefficient and thermal mixing efficiency of a lobed mixer-ejector.展开更多
This study presents experimental results focused on a performance comparison of a transcritical CO2 ejector system without an internal heat exchanger(IHX) (EJE-S) to a transcritical CO2 ejector system with an IHX(EJE-...This study presents experimental results focused on a performance comparison of a transcritical CO2 ejector system without an internal heat exchanger(IHX) (EJE-S) to a transcritical CO2 ejector system with an IHX(EJE-IHX-S) . The comparison includes the effects of changes in operating conditions such as cooling water flow rate and inlet temperature. Experiments are conducted to assess the influence of the IHX on the heating coefficient of performance(COPr) ,heating capacity,entrainment ratio,pressure lift,and other parameters. The primary flow rate of the EJE-IHX-S is higher than that of the EJE-S. The pressure lift and actual ejector work recovery are reduced when the IHX is added to the transcritical CO2 ejector system. Using a more practical performance calculation,the compression ratio in the EJE-S is reduced by 10.0%-12.1%,while that of EJE-IHX-S is reduced only by 5.6%-6.7% compared to that of a conventional transcritical CO2 system. Experimental results are used to validate the findings that the IHX weakens the contribution of the ejector to the system performance.展开更多
A novel ε-type solenoid actuator is proposed to improve the dynamic response of electro-pneumatic ejector valves by reducing moving mass weight. A finite element analysis (FEA) model has been developed to describe th...A novel ε-type solenoid actuator is proposed to improve the dynamic response of electro-pneumatic ejector valves by reducing moving mass weight. A finite element analysis (FEA) model has been developed to describe the static and dynamic operations of the valves. Compared with a conventional E-type actuator, the proposed ε-type actuator reduced the moving mass weight by almost 65% without significant loss of solenoid force, and reduced the response time (RT) typically by 20%. Prototype valves were designed and fabricated based on the proposed ε-type actuator model. An experimental setup was also established to investigate the dynamic characteristics of valves. The experimental results of the dynamics of valves agreed well with simulations, indicating the validity of the FEA model.展开更多
High-speed airflow in wind tunnel tests usually causes dramatic vibration of ejector structure,which may lead to fatigue and even destruction of the wind tunnel.Therefore,analyzing and solving the flow-induced vibrati...High-speed airflow in wind tunnel tests usually causes dramatic vibration of ejector structure,which may lead to fatigue and even destruction of the wind tunnel.Therefore,analyzing and solving the flow-induced vibration problem is a tough and indispensable part of the wind tunnel security design.In this paper,taking a kind of two-stage ejector as the study object,multiple numerical simulation methods are adopted in order to carry out research on the analysis technique of the flow-induced vibration characteristics of ejector structure.Firstly,the structural dynamics characteristic is analyzed by using the ejector structural dynamics numerical model,which is built on the basis of finite element method.Secondly,the complex flow phenomenon is explored applying numerical fluid-dynamics model of the inner flow field of the ejector,which is constructed on the basis of finite volume method.Finally,based on the two numerical models above,the vibration response of the ejector structure induced by the high-speed airflow is computed via the fluid-solid coupling technique.The comparison of the simulation results with the actual vibration test indicates that these numerical simulation methods can accurately figure out the rule of flow-induced vibration of ejectors.展开更多
The flow field in the ejector-diffuser system and its optimal operation condition are hardly complicated due to the complicated turbulent mixing, compressibility effects and even flow unsteadiness which are generated ...The flow field in the ejector-diffuser system and its optimal operation condition are hardly complicated due to the complicated turbulent mixing, compressibility effects and even flow unsteadiness which are generated inside the ejector- diffuser system. This paper aims at the improvement in ejector-diffuser system by focusing attention on entrainment ratio and pressure recovery. Several mixing guide vanes were installed at the inlet of the secondary stream for the purpose of the performance improvement of the ejector system. A Computational Fluid Dynamics (CFD) method based on Fluent has been applied to simulate the supersonic flows and shock waves inside the ejector. A finite volume scheme and density-based solver with coupled scheme were applied in the computational process. Standard k-ω turbulent model, implicit formulations were used considering the accuracy and stability. Previous experimental results showed that more flow vortexes were generated and more vertical flow was introduced into the stream under a mixing guide vane influence. Besides these effects on the secondary stream, the mixing guide vane effects on the shock system of the primary stream were also investigated in this paper. Optimal analysis results of the mixing guide vane effects were also carried out in detail in terms of the positions, lengths and numbers to achieve the best operation condition. The comparison of ejector performance with and without the mixing guide vane was obtained. The ejector-diffuser system performance is discussed in terms of the entrainment ratio, pressure recovery as well as total pressure loss.展开更多
An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehen...An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.展开更多
A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by...A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure.Moreover,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor.To assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors.The model also accounts for the friction effect in the ejector mixing section.The equations of this model are solved using an Engineering Equation Solver(EES)for different fluids.These are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and R1270.The simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.展开更多
Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major re...Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major reasons for ozone depletion (man-made refrigerants emission) and global warming (CO 2 emission). So people pay more and more attention to natural refrigerants and energy saving technologies. An innovative system combining CO 2 transcritical cycle with ejector cycle is proposed in this paper. The CO 2 compression sub-cycle is powered by electricity with the characteristics of relatively high temperature in the gas cooler (defined as an intercooler by the proposed system). In order to recover the waste heat, an ejector sub-cycle operating with the natural refrigerants (NH 3, H 2O) is employed. The two sub-cycles are connected by an intercooler. This combined cycle joins the advantages of the two cycles together and eliminates the disadvantages. The influences of the evaporation temperature in CO 2 compression sub-cycle, the evaporation temperature in the ejector sub-cycle, the temperature in the intercooler and the condensation temperature in the proposed system performance are discussed theoretically in this study. In addition, some unique features of the system are presented.展开更多
A novel dual-pressure organic Rankine cycle system(DPORC)with a dual-stage ejector(DE-DPORC)is proposed.The system incorporates a dual-stage ejector that utilizes a small amount of extraction steam from the highpressu...A novel dual-pressure organic Rankine cycle system(DPORC)with a dual-stage ejector(DE-DPORC)is proposed.The system incorporates a dual-stage ejector that utilizes a small amount of extraction steam from the highpressure expander to pressurize a large quantity of exhaust gas to performwork for the low-pressure expander.This innovative approach addresses condensing pressure limitations,reduces power consumption during pressurization,minimizes heat loss,and enhances the utilization efficiency of waste heat steam.A thermodynamic model is developed with net output work,thermal efficiency,and exergy efficiency(W_(net,ηt,ηex))as evaluation criteria,an economicmodel is established with levelized energy cost(LEC)as evaluation index,anenvironmentalmodel is created with annual equivalent carbon dioxide emission reduction(AER)as evaluation parameter.A comprehensive analysis is conducted on the impact of heat source temperature(T_(S,in)),evaporation temperature(T_(2)),entrainment ratio(E_(r1),E_(r2)),and working fluid pressure(P_(5),P_(6))on system performance.It compares the comprehensive performance of the DE-DPORC system with that of the DPORC system at TS,in of 433.15 K and T2 of 378.15 K.Furthermore,multi-objective optimization using the dragonfly algorithm is performed to determine optimal working conditions for the DE-DPORC system through the TOPSIS method.The findings indicate that the DEDPORC system exhibits a 5.34%increase inWnet andηex,a 58.06%increase inηt,a 5.61%increase in AER,and a reduction of 47.67%and 13.51%in the heat dissipation of the condenser andLEC,compared to theDPORCsystem,highlighting the advantages of this enhanced system.The optimal operating conditions are TS,in=426.74 K,T_(2)=389.37 K,E_(r1)=1.33,E_(r2)=3.17,P_(5)=0.39 MPa,P_(6)=1.32 MPa,which offer valuable technical support for engineering applications;however,they are approaching the peak thermodynamic and environmental performance while falling short of the highest economic performance.展开更多
Now there were different aspects of heat exchangers of ejectors who could work in broad range of speed regulation characteristics, and with the different cores and auxiliary substance flows. For affirming of estimated...Now there were different aspects of heat exchangers of ejectors who could work in broad range of speed regulation characteristics, and with the different cores and auxiliary substance flows. For affirming of estimated performances the bench had been project, allowing to change speed regulation characteristics of a main stream and to regulate metering characteristics of an auxiliary fluid flow. For affirming of estimated performances of a heat exchanger of an ejector the imitative bench and with a view of accident prevention had been project, cooled air and the prepare water actuation mediums. The bench had been positioned in an insulated cooled room. For putting off gauging the multifunctional measuring complex of TESTO 400, was taken the temperature a surrounding medium, and a water rate does regulate by us. The high speed photo cameras were applied to bracing of formation of drips. Strain-gauge balances apply to determination of mass of water on the shield. The air flow was shape, and moving in an ejector heat exchanger by means of the axial multiple-speed fan. The purpose of projection of a heat interchanger of an ejector is maintaining of airspeeds by means of the ventilator in the mixing chamber 10 to 80 meters per second. The temperature of given air was a stationary value, equal to -20℃. Temperature of injection water was varying from 4 to 20℃.展开更多
This paper was designed to determine the performance of the R 141 b ejector includes analysis in economics. The first step is to determine the operating condition and ejector geometry through computer calculation prog...This paper was designed to determine the performance of the R 141 b ejector includes analysis in economics. The first step is to determine the operating condition and ejector geometry through computer calculation program. That found at the generator temperature 84 ℃ and evaporator temperature 8 ℃, diameter of nozzle throat is 2 mm, diameter of nozzle exit is 8 mm, diameter of mixing chamber inlet is 25 mm, diameter of constant area section is 8 mm. Area of evacuated solar collector is 10 m2, thermal storage tank size is 0.33 m3, cold thermal storage size is 2.3 m3. The entrainment ratio and COP （coefficient of performance） of computer calculation program are 0.295 and 0.235, respectively. The second step ejector is fabricated and equipped to solar ejector refrigeration system, it is found that, average COP is 0.265. The economics analysis of solar ejector cooling system are invested in the investment cost was 158,158 baht. When calculating payback period was 7.73 years, the return value on a NPV （net present value） was 60,872.63 baht of lifetime of the system throughout a period of 15 years, and IRR （internal rate of return） is 13.57%.展开更多
A system of energy storage for solar thermal air conditioning combined with ejector cooling system for residential is determined in this paper. The purpose of this study is to design the energy storage system for heat...A system of energy storage for solar thermal air conditioning combined with ejector cooling system for residential is determined in this paper. The purpose of this study is to design the energy storage system for heating the water in a storage tank to reach the required temperature for exchanging heat with the refrigerant of cooling system. The design from calculation of thermal energy storage system that proper with the solar flat plate collector area results are 70 m2, and the hot water temperature is over than 80 ℃. A cooling system is selected for refrigerant of R141b from the solar air conditioning system of 10.5 kW, and the energy source is solar thermal energy from the collector that there is an efficiency of 0.46 approximately. This storage system for the electric solar cooling system can be reduced the problem of the intermittent of energy source with the constant generating temperature to run the cooling system continuously.展开更多
The anode pressure control in proton exchange membrane fuel cells(PEMFCs)significantly influences the stable operation of the hydrogen supply system and the internal gas circulation within the fuel cell.An efficient a...The anode pressure control in proton exchange membrane fuel cells(PEMFCs)significantly influences the stable operation of the hydrogen supply system and the internal gas circulation within the fuel cell.An efficient anode pressure control strategy is imperative for enhancing the overall system efficiency and mitigating lifespan degradation.Effective anode pressure control can prevent hydrogen starvation and instability in output per-formance under rapid load changes and purge disturbances.Fuzzy control has been extensively employed in anode pressure control studies.However,creating fuzzy rules in the control parameter’s tuning process in existing studies is predominantly dependent on expert knowledge,resulting in concerns about control accuracy.This study investigates the potential of employing the whale optimization algorithm to optimize the selection of fuzzy parameters.We first developed a control-oriented model to address the nonlinearity,coupling,and un-certainty in the hydrogen supply system.Then,based on the model and considering load variations and purge disturbances,we integrated feedforward compensation and fuzzy control into the conventional Proportional-Integral(PI)controller to suppress input disturbances,enhance control accuracy,and reduce the pressure response lag.Finally,an innovative fuzzy PI controller with the whale optimization algorithm is proposed to optimize the fuzzy parameter selection,thereby achieving precise anode pressure control.Simulation tests demonstrate that the whale-optimization-based fuzzy PI control(WFLPIF)reduces a root mean square error by 14.3%(0.636 vs.0.742)and a mean absolute percentage error by 28.8%(0.037 vs.0.052)compared to con-ventional PI control,while also outperforming feedforward-compensated fuzzy PI control(FLPIF)by 9.5%in RMSE and 17.8%in MAPE.This study substantiates the efficacy of the whale optimization algorithm in addressing the anode pressure stability control challenge of fuel cell hydrogen supply systems.展开更多
The present study addresses a variable ejector which can improve the ejector efficiency and control the re-circulation ratio under a fixed operating pressure ratio. The variable ejector is a facility to obtain specifi...The present study addresses a variable ejector which can improve the ejector efficiency and control the re-circulation ratio under a fixed operating pressure ratio. The variable ejector is a facility to obtain specific recirculation ratio under a given operating pressure ratio by varying the ejector throat area ratio. The numerical simulations are carried out to provide an understanding of the flow characteristics inside the variable ejector. The sonic and supersonic nozzles are adopted as primary driving nozzles in the ejector system, and a movable cone cylinder, inserted into a conventional ejector-diffuser system, is used to change the ejector throat area ratio. The numerical simulations are based on a fully implicit finite volume scheme of the compressible, Reynolds-Averaged Navier-Stokes equations. The results show that the variable ejector can control the recirculation ratio at a fixed operating pressure ratio.展开更多
Ejector refrigeration cycle(ERC)with advantages of simple structure and low cost holds great application potential in cascade/hybrid cycles to improve the overall system performance by removing or recovering the heat ...Ejector refrigeration cycle(ERC)with advantages of simple structure and low cost holds great application potential in cascade/hybrid cycles to improve the overall system performance by removing or recovering the heat from the main cycle.In this paper,a theoretical and experimental investigation of the ERC as a part of a cascade system was carried out.The operating parameters were optimized.The experimental ERC test rig was designed,developed and investigated at high evaporating temperatures and wide ranges of operating conditions.The influence of operating conditions on the efficiency of the ejector and ERC was analyzed.Experimental results and analysis in this study can be helpful for the application and operating condition optimization of ERC in cascade/hybrid refrigeration systems.展开更多
In this study,a modified ejector-expansion refrigeration cycle(MERC)is proposed for applications in small refrigeration units.A vapor bypass circuit is introduced into the standard ejector expansion refrigeration cycl...In this study,a modified ejector-expansion refrigeration cycle(MERC)is proposed for applications in small refrigeration units.A vapor bypass circuit is introduced into the standard ejector expansion refrigeration cycle(ERC)for increasing the ejector pressure lift ratio,thereby lowering the compressor pressure ratio in the MERC.A mathematical model has been established to evaluate the performances of MERC.Analysis results indicate that since a two phase vapor-liquid stream is used to drive the ejector in the MERC,a larger ejector pressure lift ratio can be achieved.Thus,the compressor pressure ratio decreases by 21.1%and the discharge temperature reduces from 93.6℃to 82.1℃ at the evaporating temperature of-55℃ when the vapor quality of two phase vapor-liquid stream increases from 0 to 0.2.In addition,the results show that the higher ejector component efficiencies are effective to reduce the compressor pressure ratio and the discharge temperature.Actually,the discharge temperature reduces from 91.4℃ to 82.1℃ with the ejector component efficiencies increasing from 0.75 to 0.85 at the two phase stream vapor quality of 0.2.Overall,the proposed cycle is found to be feasible in lower evaporating temperature cases.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
基金This research was funded by Natural Science Foundation of Guangdong Province,grant number 2024A1515030130National Natural Science Foundation of China,grant number 42102336.
文摘Amidst the global push for decarbonization,solar-powered Organic Rankine Cycle(SORC)systems are gaining significant attention.The small-scale Organic Rankine Cycle(ORC)systems have enhanced environmental adaptability,improved system flexibility,and achieved diversification of application scenarios.However,the power consumption ratio of the working fluid pump becomes significantly larger relative to the total power output of the system,adversely impacting overall system efficiency.This study introduces an innovative approach by incorporating a vapor-liquid ejector into the ORC system to reduce the pump work consumption within the ORC.The thermoeconomic models for both the traditional ORC and an ORC integrated with a vapor-liquid ejector driven by solar parabolic trough collectors(PTCs)were developed.Key evaluation indicators,such as thermal efficiency,exergy efficiency,specific investment cost,and levelized cost of energy,were employed to compare the SORC with the solar ejector organic Rankine cycle(SEORC).Additionally,the study explores the effects of solar beam radiation intensity,PTC temperature variation,evaporator pinch point temperature difference,and condenser pinch point temperature difference on the thermo-economic performance of both systems.Results demonstrate that SEORC consistently outperforms SORC.Higher solar radiation intensity and increased PTC inlet temperature lead to better system efficiency.Moreover,there is an optimal PTC temperature drop where both thermal and exergy efficiencies are maximized.The influence of evaporator and condenser temperature pinches on system performance is found to be inconsistent.
基金This work was supported by the National Risk Assessment Laboratory of Agroproducts Processing Quality and Safety,Ministry of Agriculture and Rural Affairs(S2020KFKT-06).
文摘The so-called organic Rankine cycle(ORC)is an effective technology allowing heat recovery from lower temperature sources.In the present study,to improve its thermal efficiency,a preheated ejector using exhaust steam coming from the expander is integrated in the cycle(EPORC).Considering net power output,pump power,and thermal efficiency,the proposed system is compared with the basic ORC.The influence of the ejector ratio(ER)of the preheated ejector on the system performances is also investigated.Results show that the net power output of the EPORC is higher than that of the basic ORC due to the decreasing pump power.Under given working conditions,the average thermal efficiency of EPORC is 29%higher than that of ORC.The ER has a great impact on the performance of EPORC by adjusting the working fluid fed to the pump,leading to significant variations of the pump work Moreover,the ER has a remarkable effect on the working fluid temperature lift(TL)at the evaporator inlet,thus reducing the evaporator heat load.According to the results,the thermal efficiency of EPORC increases by 30%,when the ER increases from 0.05 to 0.4.
文摘Three-dimensional numerical computation of the flow fields and pumping performances for the lobed mixer-ejector are conducted using full Navier-Stokes equations. In the computation, the inlet of the primary flow uses the mass flowrate boundary condition. The inlet of the second flow and the outlet of the mixing flow use the pressure boundary condition. Compared with the relative experimental resuits, it is shown that the present calculation is reasonable. And a series of numerical studies is performed to obtain the effects of area ratio and length-to-diameter ratio of mixing duct on pumping coefficient and thermal mixing efficiency of a lobed mixer-ejector.
基金Project supported by the National Basic Research Program (973) of China (No.2010CB227304)the National Key Technologies R & D Program in China (No.2006BAJ01A10)
文摘This study presents experimental results focused on a performance comparison of a transcritical CO2 ejector system without an internal heat exchanger(IHX) (EJE-S) to a transcritical CO2 ejector system with an IHX(EJE-IHX-S) . The comparison includes the effects of changes in operating conditions such as cooling water flow rate and inlet temperature. Experiments are conducted to assess the influence of the IHX on the heating coefficient of performance(COPr) ,heating capacity,entrainment ratio,pressure lift,and other parameters. The primary flow rate of the EJE-IHX-S is higher than that of the EJE-S. The pressure lift and actual ejector work recovery are reduced when the IHX is added to the transcritical CO2 ejector system. Using a more practical performance calculation,the compression ratio in the EJE-S is reduced by 10.0%-12.1%,while that of EJE-IHX-S is reduced only by 5.6%-6.7% compared to that of a conventional transcritical CO2 system. Experimental results are used to validate the findings that the IHX weakens the contribution of the ejector to the system performance.
基金Project supported by the Doctoral Fund of Ministry of Education of China (No. 20070335133)the Educational Commission of Zhejiang Province (No. 20070057), China
文摘A novel ε-type solenoid actuator is proposed to improve the dynamic response of electro-pneumatic ejector valves by reducing moving mass weight. A finite element analysis (FEA) model has been developed to describe the static and dynamic operations of the valves. Compared with a conventional E-type actuator, the proposed ε-type actuator reduced the moving mass weight by almost 65% without significant loss of solenoid force, and reduced the response time (RT) typically by 20%. Prototype valves were designed and fabricated based on the proposed ε-type actuator model. An experimental setup was also established to investigate the dynamic characteristics of valves. The experimental results of the dynamics of valves agreed well with simulations, indicating the validity of the FEA model.
基金supported in part by the National Natural Science Foundation of China (Nos.51806234, 51805530)
文摘High-speed airflow in wind tunnel tests usually causes dramatic vibration of ejector structure,which may lead to fatigue and even destruction of the wind tunnel.Therefore,analyzing and solving the flow-induced vibration problem is a tough and indispensable part of the wind tunnel security design.In this paper,taking a kind of two-stage ejector as the study object,multiple numerical simulation methods are adopted in order to carry out research on the analysis technique of the flow-induced vibration characteristics of ejector structure.Firstly,the structural dynamics characteristic is analyzed by using the ejector structural dynamics numerical model,which is built on the basis of finite element method.Secondly,the complex flow phenomenon is explored applying numerical fluid-dynamics model of the inner flow field of the ejector,which is constructed on the basis of finite volume method.Finally,based on the two numerical models above,the vibration response of the ejector structure induced by the high-speed airflow is computed via the fluid-solid coupling technique.The comparison of the simulation results with the actual vibration test indicates that these numerical simulation methods can accurately figure out the rule of flow-induced vibration of ejectors.
文摘The flow field in the ejector-diffuser system and its optimal operation condition are hardly complicated due to the complicated turbulent mixing, compressibility effects and even flow unsteadiness which are generated inside the ejector- diffuser system. This paper aims at the improvement in ejector-diffuser system by focusing attention on entrainment ratio and pressure recovery. Several mixing guide vanes were installed at the inlet of the secondary stream for the purpose of the performance improvement of the ejector system. A Computational Fluid Dynamics (CFD) method based on Fluent has been applied to simulate the supersonic flows and shock waves inside the ejector. A finite volume scheme and density-based solver with coupled scheme were applied in the computational process. Standard k-ω turbulent model, implicit formulations were used considering the accuracy and stability. Previous experimental results showed that more flow vortexes were generated and more vertical flow was introduced into the stream under a mixing guide vane influence. Besides these effects on the secondary stream, the mixing guide vane effects on the shock system of the primary stream were also investigated in this paper. Optimal analysis results of the mixing guide vane effects were also carried out in detail in terms of the positions, lengths and numbers to achieve the best operation condition. The comparison of ejector performance with and without the mixing guide vane was obtained. The ejector-diffuser system performance is discussed in terms of the entrainment ratio, pressure recovery as well as total pressure loss.
基金Project(NR2013K04) supported by Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning Engineering,ChinaProject(20130909) supported by the Higher School Science and Technology Development Fund of Tianjin,China
文摘An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.
文摘A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure.Moreover,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor.To assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors.The model also accounts for the friction effect in the ejector mixing section.The equations of this model are solved using an Engineering Equation Solver(EES)for different fluids.These are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and R1270.The simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.
文摘Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major reasons for ozone depletion (man-made refrigerants emission) and global warming (CO 2 emission). So people pay more and more attention to natural refrigerants and energy saving technologies. An innovative system combining CO 2 transcritical cycle with ejector cycle is proposed in this paper. The CO 2 compression sub-cycle is powered by electricity with the characteristics of relatively high temperature in the gas cooler (defined as an intercooler by the proposed system). In order to recover the waste heat, an ejector sub-cycle operating with the natural refrigerants (NH 3, H 2O) is employed. The two sub-cycles are connected by an intercooler. This combined cycle joins the advantages of the two cycles together and eliminates the disadvantages. The influences of the evaporation temperature in CO 2 compression sub-cycle, the evaporation temperature in the ejector sub-cycle, the temperature in the intercooler and the condensation temperature in the proposed system performance are discussed theoretically in this study. In addition, some unique features of the system are presented.
基金supported by the Foundation of Liaoning Provincial Key Laboratory of Energy Storage and Utilization(Grant Nos.CNWK202304 and CNNK202315)the Introduction of TalentResearch Start-Up Funding Projects ofYingkou Institute of Technology(Grant No.YJRC202107).
文摘A novel dual-pressure organic Rankine cycle system(DPORC)with a dual-stage ejector(DE-DPORC)is proposed.The system incorporates a dual-stage ejector that utilizes a small amount of extraction steam from the highpressure expander to pressurize a large quantity of exhaust gas to performwork for the low-pressure expander.This innovative approach addresses condensing pressure limitations,reduces power consumption during pressurization,minimizes heat loss,and enhances the utilization efficiency of waste heat steam.A thermodynamic model is developed with net output work,thermal efficiency,and exergy efficiency(W_(net,ηt,ηex))as evaluation criteria,an economicmodel is established with levelized energy cost(LEC)as evaluation index,anenvironmentalmodel is created with annual equivalent carbon dioxide emission reduction(AER)as evaluation parameter.A comprehensive analysis is conducted on the impact of heat source temperature(T_(S,in)),evaporation temperature(T_(2)),entrainment ratio(E_(r1),E_(r2)),and working fluid pressure(P_(5),P_(6))on system performance.It compares the comprehensive performance of the DE-DPORC system with that of the DPORC system at TS,in of 433.15 K and T2 of 378.15 K.Furthermore,multi-objective optimization using the dragonfly algorithm is performed to determine optimal working conditions for the DE-DPORC system through the TOPSIS method.The findings indicate that the DEDPORC system exhibits a 5.34%increase inWnet andηex,a 58.06%increase inηt,a 5.61%increase in AER,and a reduction of 47.67%and 13.51%in the heat dissipation of the condenser andLEC,compared to theDPORCsystem,highlighting the advantages of this enhanced system.The optimal operating conditions are TS,in=426.74 K,T_(2)=389.37 K,E_(r1)=1.33,E_(r2)=3.17,P_(5)=0.39 MPa,P_(6)=1.32 MPa,which offer valuable technical support for engineering applications;however,they are approaching the peak thermodynamic and environmental performance while falling short of the highest economic performance.
文摘Now there were different aspects of heat exchangers of ejectors who could work in broad range of speed regulation characteristics, and with the different cores and auxiliary substance flows. For affirming of estimated performances the bench had been project, allowing to change speed regulation characteristics of a main stream and to regulate metering characteristics of an auxiliary fluid flow. For affirming of estimated performances of a heat exchanger of an ejector the imitative bench and with a view of accident prevention had been project, cooled air and the prepare water actuation mediums. The bench had been positioned in an insulated cooled room. For putting off gauging the multifunctional measuring complex of TESTO 400, was taken the temperature a surrounding medium, and a water rate does regulate by us. The high speed photo cameras were applied to bracing of formation of drips. Strain-gauge balances apply to determination of mass of water on the shield. The air flow was shape, and moving in an ejector heat exchanger by means of the axial multiple-speed fan. The purpose of projection of a heat interchanger of an ejector is maintaining of airspeeds by means of the ventilator in the mixing chamber 10 to 80 meters per second. The temperature of given air was a stationary value, equal to -20℃. Temperature of injection water was varying from 4 to 20℃.
文摘This paper was designed to determine the performance of the R 141 b ejector includes analysis in economics. The first step is to determine the operating condition and ejector geometry through computer calculation program. That found at the generator temperature 84 ℃ and evaporator temperature 8 ℃, diameter of nozzle throat is 2 mm, diameter of nozzle exit is 8 mm, diameter of mixing chamber inlet is 25 mm, diameter of constant area section is 8 mm. Area of evacuated solar collector is 10 m2, thermal storage tank size is 0.33 m3, cold thermal storage size is 2.3 m3. The entrainment ratio and COP （coefficient of performance） of computer calculation program are 0.295 and 0.235, respectively. The second step ejector is fabricated and equipped to solar ejector refrigeration system, it is found that, average COP is 0.265. The economics analysis of solar ejector cooling system are invested in the investment cost was 158,158 baht. When calculating payback period was 7.73 years, the return value on a NPV （net present value） was 60,872.63 baht of lifetime of the system throughout a period of 15 years, and IRR （internal rate of return） is 13.57%.
文摘A system of energy storage for solar thermal air conditioning combined with ejector cooling system for residential is determined in this paper. The purpose of this study is to design the energy storage system for heating the water in a storage tank to reach the required temperature for exchanging heat with the refrigerant of cooling system. The design from calculation of thermal energy storage system that proper with the solar flat plate collector area results are 70 m2, and the hot water temperature is over than 80 ℃. A cooling system is selected for refrigerant of R141b from the solar air conditioning system of 10.5 kW, and the energy source is solar thermal energy from the collector that there is an efficiency of 0.46 approximately. This storage system for the electric solar cooling system can be reduced the problem of the intermittent of energy source with the constant generating temperature to run the cooling system continuously.
基金supported by the National Key Research and Devel-opment Program of China(No.2021YFB2500502)Science and Technology Program of Sichuan Province(No.2024ZDZX0035).
文摘The anode pressure control in proton exchange membrane fuel cells(PEMFCs)significantly influences the stable operation of the hydrogen supply system and the internal gas circulation within the fuel cell.An efficient anode pressure control strategy is imperative for enhancing the overall system efficiency and mitigating lifespan degradation.Effective anode pressure control can prevent hydrogen starvation and instability in output per-formance under rapid load changes and purge disturbances.Fuzzy control has been extensively employed in anode pressure control studies.However,creating fuzzy rules in the control parameter’s tuning process in existing studies is predominantly dependent on expert knowledge,resulting in concerns about control accuracy.This study investigates the potential of employing the whale optimization algorithm to optimize the selection of fuzzy parameters.We first developed a control-oriented model to address the nonlinearity,coupling,and un-certainty in the hydrogen supply system.Then,based on the model and considering load variations and purge disturbances,we integrated feedforward compensation and fuzzy control into the conventional Proportional-Integral(PI)controller to suppress input disturbances,enhance control accuracy,and reduce the pressure response lag.Finally,an innovative fuzzy PI controller with the whale optimization algorithm is proposed to optimize the fuzzy parameter selection,thereby achieving precise anode pressure control.Simulation tests demonstrate that the whale-optimization-based fuzzy PI control(WFLPIF)reduces a root mean square error by 14.3%(0.636 vs.0.742)and a mean absolute percentage error by 28.8%(0.037 vs.0.052)compared to con-ventional PI control,while also outperforming feedforward-compensated fuzzy PI control(FLPIF)by 9.5%in RMSE and 17.8%in MAPE.This study substantiates the efficacy of the whale optimization algorithm in addressing the anode pressure stability control challenge of fuel cell hydrogen supply systems.
文摘The present study addresses a variable ejector which can improve the ejector efficiency and control the re-circulation ratio under a fixed operating pressure ratio. The variable ejector is a facility to obtain specific recirculation ratio under a given operating pressure ratio by varying the ejector throat area ratio. The numerical simulations are carried out to provide an understanding of the flow characteristics inside the variable ejector. The sonic and supersonic nozzles are adopted as primary driving nozzles in the ejector system, and a movable cone cylinder, inserted into a conventional ejector-diffuser system, is used to change the ejector throat area ratio. The numerical simulations are based on a fully implicit finite volume scheme of the compressible, Reynolds-Averaged Navier-Stokes equations. The results show that the variable ejector can control the recirculation ratio at a fixed operating pressure ratio.
基金financially supported by National Natural Science Foundation of China(NSFC)(Contract No.51906216,No.51706167)Zhejiang Province Natural Science Foundation of China(Contract No.LY16E060004)。
文摘Ejector refrigeration cycle(ERC)with advantages of simple structure and low cost holds great application potential in cascade/hybrid cycles to improve the overall system performance by removing or recovering the heat from the main cycle.In this paper,a theoretical and experimental investigation of the ERC as a part of a cascade system was carried out.The operating parameters were optimized.The experimental ERC test rig was designed,developed and investigated at high evaporating temperatures and wide ranges of operating conditions.The influence of operating conditions on the efficiency of the ejector and ERC was analyzed.Experimental results and analysis in this study can be helpful for the application and operating condition optimization of ERC in cascade/hybrid refrigeration systems.
基金funded by the National Natural Science Foundation of China(NSFC)No.51776147
文摘In this study,a modified ejector-expansion refrigeration cycle(MERC)is proposed for applications in small refrigeration units.A vapor bypass circuit is introduced into the standard ejector expansion refrigeration cycle(ERC)for increasing the ejector pressure lift ratio,thereby lowering the compressor pressure ratio in the MERC.A mathematical model has been established to evaluate the performances of MERC.Analysis results indicate that since a two phase vapor-liquid stream is used to drive the ejector in the MERC,a larger ejector pressure lift ratio can be achieved.Thus,the compressor pressure ratio decreases by 21.1%and the discharge temperature reduces from 93.6℃to 82.1℃ at the evaporating temperature of-55℃ when the vapor quality of two phase vapor-liquid stream increases from 0 to 0.2.In addition,the results show that the higher ejector component efficiencies are effective to reduce the compressor pressure ratio and the discharge temperature.Actually,the discharge temperature reduces from 91.4℃ to 82.1℃ with the ejector component efficiencies increasing from 0.75 to 0.85 at the two phase stream vapor quality of 0.2.Overall,the proposed cycle is found to be feasible in lower evaporating temperature cases.
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.
