大型空气压缩机变工况性能试验研究

压缩空气储能系统压缩机受系统自身特性影响,长期处于变工况运行状态。对某多级压缩空气储能系统大型空气压缩机变工况条件下级间性能开展试验研究,即利用压缩机管网特性试验平台,开展排气压力6.5～9.5MPa范围试验测试,对压缩机各级吸气和排气压力、吸气和排气温度、压缩机排气量、电机电流、电压等参数进行实时采集。通过对压缩机实时变工况下各项参数分析,具体研究压缩机的容积效率、循环指示功率、等温效率、各级压比分配和各级压损随出口负荷变化而变化的规律。研究结果表明:压缩机的容积效率基本不随工况的变化而变化,平均为0.96;循环指示功率随出口负荷的增加而增加;压缩机的多变效率从74.02%上升到78.14%,多变效率随着排气压力的增加而增加;低压级压比增大速度较快,易达到额定状态,高压级压比达到额定状态较缓;一～四级的相对压力损失基本保持不变,五级出口排气到集气汇管的相对压力损失随着出口负荷的增大而减小。     

热泵储电系统中压降对效率的影响

构建了基于闭式布雷顿循环的热泵储电系统模型,通过热力学计算得到了状态参数和往返效率。闭式系统中压缩机和透平的进出口压力相互关联,压比随压降变化,引起压缩功与膨胀功改变,从而对往返效率产生重要影响。经对比分析,结果表明：压降升高会降低往返效率,储能过程压降升高造成储能功耗增大且释能发电量减少,释能过程压降升高只造成释能发电量减少;储能过程压降对效率的影响大于释能过程,低压侧压降的影响大于高压侧;按照影响程度从低到高,分别为储能过程高压侧压降、释能过程高压侧压降、储能过程低压侧压降和释能过程低压侧压降;在给定参数下,上述四个过程的压降从10kPa增至60kPa,往返效率降幅百分比分别为4.72%、5.79%、11.83%和20.63%。因此,在条件有限时,系统优化方向为首先降低释能过程低压侧的压降。本文构建的基于闭式布雷顿循环的热泵储电系统,可为热泵储电系统的设计与优化提供参考。     

热回收式CO2制冷系统性能研究

对热回收式CO2制冷系统性能COP进行了计算和分析,结果表明:蒸发温度、气体冷却器出口CO2温度、热水加热器入口水温是影响其COP的主要因素;回热器出口过热度对COP的影响较小,对压缩机的排气温度影响较大;随着排气压力的升高,COP是否出现峰值,取决于气体冷却器入口制冷剂的特征温度;在相同工况下,蒸发温度、气体冷却器出口CO2温度、回热器出口过热度对最佳排气压力的影响较小,热水加热器入口水温是影响最佳排气压力的主要因素。     

多级回热式跨临界压缩二氧化碳储能系统热力性能分析

为解决压缩空气储能系统储能密度和效率低的问题,建立了基于地下储气室的多级回热式跨临界压缩二氧化碳储能系统(Compress Carbon Dioxide Energy storage,TC-CCES)热力学模型及■分析模型,采用二氧化碳代替空气作为存储介质,对系统进行热力学性能分析和敏感性分析。结果表明:TC-CCES的储能密度达到57.29 kW·h/m~3,是先进绝热压缩空气储能系统(Advanced adiabatic CAES,AA-CAES)的2～25倍,储能效率和■效率分别为58.41%和67.89%,均高于AA-CAES;在TC-CCES中,储能过程的压缩机级间冷却器、释能过程的膨胀再热器以及回热系统中热泵■损失较大,通过提高系统储能压力、释能压力以及降低系统低压储气室入口压力,可以提高系统的储能效率和■效率。     

基于EBSILON的压缩二氧化碳储能系统仿真分析

基于EBSILON软件建立了100 MW/1 000 MWh两级压缩、两级膨胀二氧化碳储能系统模型,研究工质流量和膨胀机、压缩机入口温度对系统效率的影响。结果显示：储能系统模型的发电量与设计值的相对偏差为1.72%,电转电效率为65.61%。工质流量与发电量呈正相关,年泄露工质量5%,则发电量将降低3.15%。第一级膨胀机入口温度每提升2℃,发电量提升0.47 MW。第一级压缩机入口温度每提升5℃,压缩功耗平均降低1.63 MW。在资本金内部收益率为8%的前提下,项目作为用户侧储能时,峰谷电价差需达到1.46元/kWh。     

耦合有机朗肯循环的液化空气储能系统性能研究

为解决液化空气储能系统(LAES)压缩热利用不完全的问题,构建了耦合有机朗肯循环的液化空气储能系统(ORC-LAES)。对ORC-LAES系统建立热力学性能计算模型,在设计参数下分析压缩机出口压力、膨胀机入口压力、加压水初温、加压水流量比及膨胀机级数对ORC-LAES系统性能的影响。结果表明,当压缩机出口压力由6 MPa上升到16 MPa、加压水初温从293 K上升到323 K时,系统的循环效率、火用效率和液化率均下降;当膨胀机入口压力由8 MPa上升到18 MPa时,系统循环效率和火用效率均增加;当加压水流量比由0.51上升到0.96时,系统循环效率和火用效率先增加再减少,流量比为0.71时,系统的循环效率和火用效率达到最大;在压缩热利用上耦合有机朗肯循环要优于增加膨胀机级数;ORC-LAES系统与LAES系统相比,循环效率提高4.8%,火用效率提升5.1%。     

微型燃气轮机圆筒原表面回热器的性能试验研究

对微型燃气轮机圆筒形原表面式回热器的传热与流动性能进行了试验研究.利用计算机控制检测传热性能试验台对该回热器在①两侧流量相等、改变两侧温度及②固定两侧温度,改变系统质量流量的情况下进行了传热性能和阻力性能试验.结果表明:随着质量流量的增加,回热器的传热系数增大,传热量逐渐增加,回热器的两侧压降也增大;在等流量时,回热器两侧的压降有所不同,高压低温侧压降比低压高温侧压降大,但低压高温侧压降增加较快,因此在设计回热器时必须重视两侧压降的变化情况,根据试验结果得出了传热和阻力随工况改变的变化趋势.     

两级填充床式压缩空气储能系统充放电行为研究

基于两级填充床式压缩空气储能系统运行原理,建立了压缩机、透平、填充床蓄热器及储气洞穴的非稳态分析模型,对两级填充床式压缩空气储能系统充放电行为进行了模拟,分析了系统在给定充电功率下的整体热力学性能和各部件的运行特性。结果表明：相比于完整充放电循环,在给定的充电功率下系统的充放电效率仅为54.33%,下降了约8.07%;受到储能功率的影响,压缩机的效率变化范围较大,仅有77.13%的电能转化为压缩空气的内能,而高/低压透平因为进口处空气温度逐渐降低而偏离设计工况导致效率下降;压缩机和透平的火用损之和占总火用损的81.51%。     

太阳能光伏-内燃机发电及余热利用系统热力学分析

对利用太阳能和生物质能的联合冷热电系统(CCHP)进行热力学分析。系统由内燃机和太阳能光伏电池供电，由吸收式制冷及热水系统进行余热回收。太阳能光伏电池采用五参数模型，内燃机为零维、单区模型。分析转速和压比对内燃机输出功率、排气排放物和气缸内传热的影响。结果显示：太阳能光伏电池效率为14%，日发电量500 kWh；内燃机热效率可以达到37%。转速提高后，整体CCHP电效率提高2.8%，余热利用效率提高10%。内燃机的压缩比增大后，CCHP电效率增大0.52%，整体冷热电效率几乎不变。整个CCHP系统电效率为20%，冷热电联合效率可以达到40%。     

一种熔融铝液辐射余热回收用集热器的性能仿真研究

以回收熔融铝液辐射热量的集热器为研究对象,建立了集热器热力学过程理论模型,并采用Workbench和Fluent软件对集热器辐射传热过程和对流传热过程进行仿真分析。结果表明：当辐射距离为400~900 mm时,壁面平均温度在190~350 ℃之间;出口压力和壁面温度增加导致对流传热系数减小,而流量增加则使对流传热系数增加;流量和出口压力增加导致出口温度降低;系统流量增加造成压缩空气压降增大,出口压力增大导致压降减小,而壁面温度对压降没有影响。     

Thermodynamic analysis of a novel energy storage system with carbon dioxide as working fluid

Recently, energy storage system (ESS) with carbon dioxide (CO₂) as working fluid has been proposed as a new method to deal with the application restrictions of Compressed Air Energy Storage (CAES) technology, such as dependence on geological formations and low energy storage density. A novel ESS named as Compressed CO₂ Energy Storage (CCES) based on transcritical CO₂ Brayton cycle is presented in this paper. The working principle of CCES system is introduced and thermodynamic model is established to assess the system performance. Parametric analysis is carried out to study the effect of some key parameters on system performance. Results show that the increase of turbine efficiency is more favorable for system optimization and the effect of minimum pressures on system performance is more significant compared with maximum pressures. A simple comparison of CCES system, liquid CO₂ system and Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) system is conducted. It is shown that the system efficiency of CCES is lower than that of AA-CAES system but 4.05% higher than that of liquid CO₂ system, while the energy density of CCES system is 2.8 times the value of AA-CAES system, which makes CCES a novel ESS with potential application.     

Thermodynamic optimization for an open cycle of an externally fired micro gas turbine (EFmGT). Part 1: Thermodynamic modelling

The principle of optimally tuning the air flow rate and subsequent distribution of pressure drops is applied to optimize the performance of a thermodynamic model for an open regenerative cycle of an externally fired micro gas turbine power plant with pressure drop irreversibilities by using finite-time thermodynamics and considering the size constraints of the real plant. There are eight flow resistances encountered by the working fluid stream for the cycle model. Two of these, the friction through the blades and vanes of the compressor and the turbine, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet and outlet, the turbine inlet and outlet and the regenerator hot/cold-side inlet and outlet. These resistances associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop, and control the air flow rate and the net power output and thermal efficiency. The analytical formulae for the power output, efficiency and other coefficients are derived, which indicate that the thermodynamic performance for an open regenerative cycle of an externally fired micro gas turbine power plant can be optimized by adjusting the mass flow rate (or the distribution of pressure losses along the flow path). It is shown that there are optimal air mass flow rates (or the distribution of pressure losses along the flow path) which maximize the net power output.     

Thermodynamic analysis of a novel energy storage system based on compressed CO2 fluid

Because of rapidly growing renewable power capacity, energy storage system is in urgent need to cope with the reliability and stability challenges. CO₂ has already been selected as the working fluid, including thermo‐electrical energy storage or electrothermal energy storage systems and compressed CO₂ energy storage (CCES) systems. In this paper, a CCES system based on Brayton cycle with hot water as the heat storage medium is proposed and analyzed. Thermodynamic model of the system is established for energy and exergy analysis. Sensitivity analysis is then conducted to reveal effects of different parameters on system performances and pursue optimization potential. At a typical transcritical operation condition, round trip efficiency is 60% with energy density of 2.6 kWh/m³. And for the typical supercritical operation condition, the round trip efficiency can reach 71% with energy density of 23 kWh/m³. High round trip efficiency and energy density, which is comparable with those of compressed air energy storage systems, thermo‐electrical energy storage (electrothermal energy storage) systems, and other CCES systems, lead to promising prospect of the proposed system. Copyright © 2017 John Wiley & Sons, Ltd.     

Optimization of capacity and operation for CCHP system by genetic algorithm

The technical, economical and environmental performances of combined cooling, heating and power (CCHP) system are closely dependent on its design and operation strategy. This paper analyzes the energy flow of CCHP system and deduces the primary energy consumption following the thermal demand of building. Three criteria, primary energy saving (PES), annual total cost saving (ATCS), and carbon dioxide emission reduction (CDER) are selected to evaluate the performance of CCHP system. Based on the energy flow of CCHP system, the capacity and operation of CCHP system are optimized by genetic algorithm (GA) so as to maximize the technical, economical and environmental benefits achieved by CCHP system in comparison to separation production system. A numerical example of gas CCHP system for a hotel building in Beijing is given to ascertain the effectiveness of the optimal method. Furthermore, a sensitivity analysis is presented in order to show how the optimal operation strategy would vary due to the changes of electricity price and gas price.     

Performance comparison of combined cooling heating and power system in different operation modes

Operation mode of combined cooling heating and power (CCHP) system determines its energetic and environmental performances. This paper analyzes the energy flows of CCHP system and separated production (SP) system. The fuel energy consumptions of CCHP system following electrical demand management (EDM) and thermal demand management (TDM) are deduced respectively. Three indicators: primary energy saving, exergy efficiency and CO₂ emission reduction, are employed to evaluate the performances of CCHP system for a commercial building in Beijing, China. The feasibility analysis shows that the performance of CCHP system is strictly dependent upon building energy demands. The selection of CCHP operation modes is systemically based on building loads, CCHP system and local SP system. The calculation results conclude that CCHP system in winter under EDM achieves more benefits than in summer. The sensitivity discussion indicates that the coefficient of performance for cooling and the efficiency of electricity generation are the most sensitive variables to the energetic and environmental performances of CCHP system.     

Thermodynamic analysis of a new combined cooling, heat and power system driven by solid oxide fuel cell based on ammonia-water mixture

Although a solid oxide fuel cell combined with a gas turbine (SOFC-GT) has good performance, the temperature of exhaust from gas turbine is still relatively high. In order to recover the waste heat of exhaust from the SOFC-GT to enhance energy conversion efficiency as well as to reduce the emissions of greenhouse gases and pollutants, in this study a new combined cooling, heat and power (CCHP) system driven by the SOFC is proposed to perform the trigeneration by using ammonia-water mixture to recover the waste heat of exhaust from the SOFC-GT. The CCHP system, whose main fuel is methane, can generate electricity, cooling effect and heat effect simultaneously. The overall system performance has been evaluated by mathematical models and thermodynamic laws. A parametric analysis is also conducted to examine the effects of some key thermodynamic parameters on the system performance. Results indicate that the overall energy conversion efficiency exceeds 80% under the given conditions, and it is also found that the increasing the fuel flow rate can improve overall energy conversion efficiency, even though both the SOFC efficiency and electricity efficiency decrease. Moreover, with an increased compressor pressure ratio, the SOFC efficiency, electricity efficiency and overall energy conversion efficiency all increase. Ammonia concentration and pressure entering ammonia-water turbine can also affect the CCHP system performance.     

压缩空气/二氧化碳储能系统的运行方式研究

为深入研究不同工质和输出方式对太阳能-先进绝热压缩空气/二氧化碳联合储能系统性能的影响,提出4种运行方案.通过仿真计算,对比分析4种不同方案下系统的热力学与经济学特性,并研究关键参数对系统性能的影响.结果表明:采用二氧化碳为工质,只输出电能时系统的储能效率最高.而采用二氧化碳为工质,同时输出电能和热能时系统的年利润率最...     

新型城市低温地热冷热电联产系统热力性能分析

为节约及合理利用能源,提高城市能量总能系统利用率,基于有机朗肯循环(ORC)和冷热电联产(CCHP),提出了一种新型的城市低温地热冷热电联产系统(以下简称ORC-CCHP系统)。根据热力学第一、第二定律,建立了热力学模型,编写计算机程序进行了系统的热力性能分析。结果表明:采用R245fa、LiBr溶液作为ORCCCHP系统循环工质时,选择窄点温差较小蒸发器可获得更高火用效率;增加太阳能集/蓄热系统,提高热流参数,减小换热温差,可进一步提升系统热力学性能;系统分别采用5种不同有机工质时,R236fa使系统的热力性能达到最佳,并在蒸发压力为0. 62 MPa、窄点温差为0 K时,ORC-CCHP系统获得最大净输出功为1 948 kW,系统火用效率为19. 28%,系统火用效率最高值为85. 78%。     

A solar energy storage and power generation system based on supercritical carbon dioxide

This paper proposes a new type of solar energy based power generation system using supercritical carbon dioxide and heat storage. The power generation cycle uses supercritical carbon dioxide as the working fluid and integrates the supercritical carbon dioxide cycle with an efficient high-temperature heat storage. The analysis shows that the new power generation system has significantly higher solar energy conversion efficiency in comparison to the conventional water-based (steam) system. At the same time, the heat storage not only overcomes the intermittent nature of solar energy but also improves the overall system efficiency. The study further reveals that the high temperatures and high pressures are favorable for solar energy storage and power generation. Moreover the expander and the heat storage/regenerator are found to be the key components that determine the overall system performance.     

The influence of rotary valve distribution systems on the energetic efficiency of regenerative thermal oxidizers (RTO)

On–off valve systems, commonly used in regenerative thermal oxidizer (RTO) plants, generate, during the opening time, a mass flow rate (MFR) which is constant. On the contrary, rotary valve systems, which are increasingly adopted in RTO plants, are characterized by variable MFR profiles. In this work, the energy requirements of two RTO systems, equipped with on–off or rotary valves, were determined using a home‐developed numerical code. Energy performances were evaluated by calculating the thermal efficiency and pressure drop within structured or random packed bed RTO systems, at the same mean MFR. The results demonstrated that thermal efficiency was only moderately influenced by the valve system, and is slightly lower for the RTO with on–off valve. On the other hand, the study revealed that energy requirements of all RTO systems were basically unaffected by cycle duration, allowing valve rotational velocity to be freely set to maximize for other technical requirements. On the contrary, pressure drop was greatly influenced by the valve type and increased as variability in MFR function augmented. Moreover, the type of regenerator, structured or random packed bed, affected differently the total energy requirements (basically pumping energy plus auxiliary fuel). Energy requirements of structured and random regenerators were comparable only when volatile organic compounds concentration was lower than typical values encountered in the industrial practise. In other cases, structured regenerators RTO were more competitive. Finally, structured regenerators are usually the best choice when rotating valve distribution systems are adopted. Copyright © 2007 John Wiley & Sons, Ltd.