Simulation and performance analysis of organic Rankine cycle combined heat and power system

To improve the overall thermal efficiency of the organic Rankine cycle（ ORC）, a simulation study was carried out for a combined heat and power（ CHP） system, using the Redlich-Kuang-Soave（ RKS） equation of state. In the system,R245 fa was selected as the working fluid. A scroll expander was modeled with empirical isentropic expansion efficiency.Plate heat exchangers were selected as the evaporator and the condenser, and detailed heat transfer models were programmed for both one-phase and two-phase regions. Simulations were carried out at seven different heat source temperatures（ 80,90, 100, 110, 120, 130, 140 ℃） in combination with eight different heat sink temperatures（ 20, 25, 30, 35, 40, 45, 50,55 ℃）. Results showthat in the ORC without an internal heat exchanger（ IHE）, the optimum cycle efficiencies are in the range of 7. 0% to 7. 3% when the temperature differences between the heat source and heat sink are in the range of 70 to90 ℃. Simulations on CHP reveal that domestic hot water can be produced when the heat sink inlet temperature is higher than40 ℃, and the corresponding exergy efficiency and overall thermal efficiency are 29% to 56% and 87% to 90% higher than those in the non-CHP ORC, respectively. It is found that the IHE has little effect on the improvement of work output and efficiencies for the CHP ORC.

Thermo-economic Investigation of an Enhanced Geothermal System Organic Rankine Cycle and Combined Heating and Power System

As a potentially viable renewable energy, Enhanced Geothermal Systems(EGSs) extract heat from hot dry rock(HDR) reservoirs to produce electricity and heat, which promotes the progress towards carbon peaking and carbon neutralization. The main challenge for EGSs is to reduce the investment cost. In the present study, thermo-economic investigations of EGS projects are conducted. The effects of geofluid mass flow rate, wellhead temperature and loss rate on the thermo-economic performance of the EGS organic Rankine cycle(ORC) are studied. A performance comparison between EGS-ORC and the EGS combined heating and power system(CHP) is presented. Considering the CO_(2)emission reduction benefits, the influence of carbon emission trading price on the levelized cost of energy(LCOE) is also presented. It is indicated that the geofluid mass flow rate is a critical parameter in dictating the success of a project. Under the assumed typical working conditions, the LCOE of EGS-ORC and EGS-CHP systems are 24.72 and 16.1 cents/k Wh, respectively. Compared with the EGS-ORC system, the LCOE of the EGS-CHP system is reduced by 35%. EGS-CHP systems have the potential to be economically viable in the future. With carbon emission trading prices of 12.76 USD/ton, the LCOE can be reduced by approximately 8.5%.

Performance Analysis of an Organic Rankine Cycle with a Preheated Ejector

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.

Effects of ORC Working Fluids on Combined Cycle Integrated with SOFC and ORC for Stationary Power Generation

The purpose of this study is to explore the effects of working fluid on conventional combined cycle integrated with pressurized solid oxide fuel cell (SOFC) and waste heat recovery organic Rankine cycle (ORC) for stationary utility power generation. The mathematical model of a natural gas fueled design configuration is developed in Matlab and Simulink and simulated with 14 working fluids. The effluent gases of SOFC undergo combustion in the combustion chamber and it is utilized in the gas turbine, steam turbine cycle and ORC. The model is compared with those found in literature and the parametric studies of temperature, flow rate, fuel utilization factor and exhaust gas on the system efficiency are examined. Results revealed that working fluids show a closely related behavior in efficiency at low pressure ratio and high flow fraction, fuel utilization, and temperature. R-123 was found to perform the best among 14 working fluids studied, yielding a system energy efficiency of 70% in the combined cycle integrated with SOFC and ORC.

Parametric Energy and Economic Analysis ofModified Combined Cycle Power Plant with Vapor Absorption and Organic Rankine Cycle

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.

Study on Combination of Engine/Steam Turbine Cycle for Improving the Energy Conversion

This work discusses the combination of two thermodynamic cycles seeking to improve the overall chemical energy conversion rate into mechanical energy. Here one engine operates according a Rankine cycle in order to use part of the thermal energy released to the boundary, i.e., the neighboring atmosphere. The analysis of this combined cycle shows that it might, under proper condition, represent a gain of 1.2% in the overall delivered engine power.

多级Brayton/Rankine联合动力循环性能分析

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Study on the Performance of Organic Rankine Cycle-Heat Pump(ORC-HP) Combined System Powered by Diesel Engine Exhaust

This study presents an ORC-HP combined system driven by diesel engine exhaust. This paper focuses on the feasibility and performance of the combined system under heating mode to heat a coach. The performances of the combined system with different parameters, including condensation temperature and evaporation pressure in ORC system, gas cooler outlet pressure, gas cooler outlet temperature and evaporation temperature in HP system, have been analyzed. The results show that the combined system can fully meet the demand of heat production. The optimal flow division ratio(rp) of 0.32 is selected by analyzing the system performance. Low condensation temperature is beneficial to the combined system performance. There exists a suitable range of evaporation temperature, gas cooler outlet pressure and gas cooler outlet temperature to achieve excellent performance. The heating coefficient of performance(COP_h) shows a first increasing and then decreasing trend with gas cooler outlet pressure, namely there exists an optimal gas cooler outlet pressure that achieves the maximum COP_h. The maximum total efficiency, COP_h and heating capacity can reach up to 48.44%, 4.78 and 176.56 kW, respectively. These results show significant energy savings by applying the ORC-HP combined system.

Performance analysis of cogeneration systems based on micro gas turbine(MGT),organic Rankine cycle and ejector refrigeration cycle

In this paper,the operation perfonnance of three novel kinds of cogeneration systems under design and off-design condition was investigated.The systems are MGT(micro gas turbine)+ORC(organic Rankine cycle)for electricity demand,MGT+ERC(ejector refrigeration cycle)for electricity and cooling demand,and MGT+ORC+ERC for electricity and cooling demand.The effect of 5 different working fluids on cogeneration systems was studied.The results show that under the design condition,when using R600 in the bottoming cycle,the MGT+ORC system has the lowest total output of 117.1 kW with a thermal efficiency of 0.334,and the MGT+ERC system has the largest total output of 142.6 kW with a thermal efficiency of 0.408.For the MGT+ORC+ERC system,the total output is between the other two systems,which is 129.3 kW with a thermal efficiency of 0.370.For the effect of different working fluids,R123 is the most suitable working fluid for MGT+ORC with the maximum electricity output power and R600 is the most suitable working fluid for MGT+ERC with the maximum cooling capacity,while both R600 and R123 can make MGT+ORC+ERC achieve a good comprehensive performance of refrigeration and electricity.The thermal efficiency of three cogeneration systems can be effectively improved under oredesign condition because the bottoming cycle can compensate for the power decrease of MGT.The results obtained in this paper can provide a reference for the design and operation of the cogeneration system for distributed energy systems(DES).

计及氢能高效利用和热电灵活输出的综合能源系统源荷灵活运行策略

为进一步发挥氢能高效利用优势,构建绿色低碳能源系统,提出一种计及氢能高效利用和热电联产灵活输出的综合能源系统源荷灵活运行策略。首先,对源侧供能模型进行两方面改进:一是引入含风电制氢、燃气混氢、多能用氢和储氢的氢能利用模型,并考虑到电解水和甲烷化反应过程中的热量散失情况,引入热量回收装置,构建计及热量回收的氢能高效利用模型;二是针对常规热电联产灵活性不足的问题,构建含电锅炉和有机朗肯循环的热电灵活输出模型,以解耦常规热电联产“以热定电”和“以电定热”限制。其次,在荷侧引入含可转移、可削减和可平移的电、热柔性负荷,以缓解电、热负荷峰谷差,并与源侧相结合,形成源荷灵活运行模型。最后,综合考虑阶梯型碳交易成本、设备运行维护成本、弃风成本以及购能成本,建立综合能源系统源荷灵活优化运行模型。采用CPLEX求解器对所提综合能源系统源荷灵活运行模型进行求解,并设置不同场景进行对比。结果表明,相比常规氢能利用模型,考虑所提计及热量回收的氢能高效利用模型时,系统的总成本、碳排放量分别降低了1.92%、4.22%,并且引入热电联产改进模型后,其总成本、碳排放量可进一步降低4.08%、7.32%,实现系统低碳、经济和灵活运行。

面向月球基地的自循环热管理及发电系统研究

针对月球基地热管理需求,根据月面热环境特点,设计了一种面向月球基地的新型自循环热管理及发电系统。系统将有机朗肯循环(ORC)和喷射制冷循环(ERC)相结合,以仪器设备散热和太阳能或核能废热为热源,以外部冷背景为冷源,系统内一部分的工质吸收热源,通过有机朗肯循环发电,另一部分工质通过蒸发器吸收航天员日常工作环境中的热量,为航天服和科学研究提供冷量。系统不需要外部电力,可以独立运行,实现发电与制冷。经分析模型计算,在满足月球基地热量收集、传输和排散的基础上,可以实现最大废热制冷率40%以上,总废热利用效率50%以上.

回收船舶柴油机余热的双回路有机朗肯循环系统性能分析

为了降低船舶二氧化碳排放,利用双回路有机朗肯循环(DORC)系统对船舶柴油机的排烟和缸套冷却水余热进行回收发电。通过夹点温差法构建热力学模型,高温回路用于回收排烟热量,低温回路用于回收缸套冷却水热量和高温回路冷凝热。分析9对工质组合时DORC系统的冷凝器热力学参数对系统性能的影响,结果表明:随着高温回路的冷凝温度和冷凝热负荷的增高,低温回路蒸发压力和净输出功呈现升高趋势,在高温回路冷凝热负荷为715.2 kW~1 241.2 kW时,系统总净输出功呈现先升高后降低的趋势。当高温回路采用环乙烷,低温回路采用一氯三氟丙烯(反式)为工质时,系统总净输出功可达到410.6 kW。

超临界CO_(2)-有机朗肯联合循环的多目标优化

采用复合型超临界二氧化碳-有机朗肯联合循环来回收燃气轮机的余热,建立了热力学以及[火用]经济性模型,探究了关键参数对联合循环系统性能的影响规律,从热力学性能、空间紧凑性、[火用]经济性能等方面对联合循环系统进行了研究,并对联合循环进行了多目标优化。结果表明:在最优状态下复合型超临界二氧化碳再压缩-有机朗肯联合循环的效率为54.56%,比燃-蒸联合循环提高了4.2%,其单位输出功率所需换热面积为0.1178m^(2)/kW,比燃-蒸联合循环降低了21.41%。

低温热源喷射式发电制冷复合系统特性分析

提出一种低温热源喷射式发电制冷复合系统。该系统将有机物朗肯循环与喷射式制冷循环相结合,利用透平排气驱动喷射器工作,同时实现发电和制冷的功能。在定义系统评价指标的基础上,选取性能优良的有机物R245fa作为工质,建立系统仿真模型,进行计算分析。计算结果表明,在热源蒸发温度Tg=120℃,制冷蒸发温度Te=7℃,冷凝温度Tc=25℃的标准工况下,系统的热力学第一定律效率可达37%,热力学第一定律折合效率可达15.6%,火用效率可达37.5%。分析同时表明,提高热源蒸发温度Tg,提高制冷蒸发温度Te,降低冷凝温度Tc,有利于提高系统的工作性能;提高透平膨胀比β可以提高系统电冷比R。

微型燃气轮机与有机朗肯循环装置组成联合循环的设计与分析

提出筛选有机朗肯循环工质的方法。基于能的"温度对口,梯级利用"原理和有机工质的热力性质,讨论用于增大输出轴功的微型燃气轮机与有机朗肯循环装置组成的联合循环,给出该联合循环的流程布置。用此布置将国内某正在研制中的微型燃气轮机与使用R123为底循环工质的有机朗肯循环装置组成联合循环,进行模拟计算和敏感性分析。结果表明,该联合循环可将热效率提高9.4%,达到38.4%,循环增压比、最高温度、回热度和环境温度的变化均会对热效率产生一定的影响。

有机朗肯循环热电联供系统的实验研究

有机朗肯循环低温热力循环性能优越,易于小型化和自动运行,非常适合于分布式热电联供系统。依托已有的ORC-CHP实验平台,对热源温度101℃,膨胀机乏汽余热利用温度21.6～48.7℃时系统的热力性能进行了实验研究。在该温度范围内,ORC-CHP系统的综合能量效率96%～97%,其中热功转换效率4.4%～5.1%,乏汽余热利用效率91%～92%;从可用能角度出发,系统综合可用能效率50.0%～75.3%,其中热功可用能效率24.4%～19.2%,乏汽余热可用能效率25.7%～56.2%。实验表明该系统可以高效利用膨胀机乏汽余热,明显提高了有机朗肯循环的综合利用效率。

基于固体氧化物燃料电池的有机工质余热发电联合系统特性的理论研究

针对有机朗肯循环对低温余热回收的显著优势,提出了一种基于固体氧化物燃料电池(SOFC)的有机工质余热发电联合系统.该系统包含内重整SOFC、后燃室、燃气轮机、压气机、预热器和有机朗肯循环,实现了能量的梯级利用,有效地提高了系统的总发电效率.在稳态数学模型的基础上,建立了基于SOFC的有机工质余热发电联合系统的热力仿真分析平台,研究了关键参数对系统性能的影响.结果表明:在设计工况下,系统的总发电效率可达65%以上;随着燃料摩尔流量的增加,系统的净输出功增加,但系统的总发电效率有所下降;在一定范围内,增大压气机压比可以提高系统净输出功和总发电效率;随着蒸汽与碳物质的量比的增大,系统的净输出功减小,总发电效率下降.

中心支板式RBCC发动机引射模态流动与燃烧研究

为了深入认识引射模态工作机理,针对中心支板式RBCC发动机,在飞行马赫数2、不同内置火箭流量时的工作情况进行了全流道一体化的数值模拟,并对其内流场特征、火箭射流/引射空气掺混发展特征以及复合型释热规律和火焰结构等开展了详细分析。研究发现:RBCC发动机引射模态下的流动掺混燃烧过程是一个复杂且高度耦合的过程。在即时预混燃烧(SMC)模式下,燃烧过程主要在内置火箭射流与来流空气之间形成的剪切层内进行;流道上游剪切层厚度较薄,温度和组分浓度梯度较大,掺混速率快;高释热区集中分布在流道上游,可分为超声速释热区和亚声速释热区;流道内的燃烧反应以扩散燃烧为主,随着掺混过程的进行逐渐向预混燃烧过渡。提高火箭流量,流道内温度升高,反应持续距离增加,但掺混效率降低。

火箭引射模态下一次火箭流量优化方法研究

对火箭基组合循环(RBCC)发动机火箭引射模态下一次火箭流量优化方法开展了研究,并对飞行条件下一次火箭流量的变化规律进行了分析。提出了采用有效比冲作为优化目标的一次火箭流量单目标优化模型;建立了求解与一次火箭流量相匹配的二次燃料流量的比例控制方法;在考虑发动机性能优化与弹道分析耦合作用的基础上,采用试验设计和遗传算法,建立了火箭引射模态下一次火箭流量优化方法。针对空中载机发射的RBCC发动机,开展了火箭引射模态下一次火箭流量优化,并根据弹道分析结果,给出了飞行条件下一次火箭流量变化规律。结果表明,为了克服飞行过程中声障阻力,一次火箭流量在Ma=1.0附近达到最大,此时对发动机提出较高的推力设计要求;在Ma=1.5附近,来流空气的冲压作用占主导地位,一次火箭流量出现较大程度的节流,此时对发动机提出较高的比冲设计要求;超过Ma=1.5后,一次火箭以较小的流量状态维持稳定工作;火箭引射模态下一次火箭流量调节比达到了5.0。

多模态RBCC主火箭室压对引射流动燃烧影响研究

为了研究火箭冲压组合动力循环(RBCC)发动机主火箭室压对引射模态发动机性能的影响,针对宽范围飞行的二元中心支板式构型,分析了引射模态亚声速飞行阶段发动机工作特点,采用发动机与飞行器前后体集成的全流道数值模拟计算方法,研究了主火箭室压对RBCC亚声速飞行阶段燃烧室流动燃烧及发动机性能的影响。结果表明:主火箭室压增至26MPa时,由于主火箭喷管面积扩张比相应增大,使得主火箭喷管出口射流欠膨胀程度没有增大,避免了Fabri壅塞现象的产生,同时增大的主火箭射流马赫数使主火箭射流对第一级凹腔下游二次流道的挤压作用明显减弱,综合作用使得Ma=0和Ma=0.8条件下引射比分别提高了22.4%和40.0%;全流道计算结果表明在亚声速飞行阶段,提高主火箭室压一方面提升了主火箭推力,另一方面提升了燃烧室及后体推力,综合作用使得发动机比冲分别提高了11.5%和25.3%。提高主火箭室压有利于提升宽范围飞行RBCC发动机亚声速飞行阶段发动机性能。