压缩空气储能透平滑压运行参数优化研究

针对绝热压缩空气储能系统中的透平滑压运行参数进行研究，以某项目100MW空气透平为例，介绍了储气方式和储气参数对空气透平的影响，提出了以单位质量发电量作为压缩空气储能透平性能指标的考核办法。对于全周进气加补气阀的进气调节方式，核算出了9.8MPa～3.7MPa滑压范围内各个补气阀开启点压力对应的单位质量发电量，通过对比确定最佳的补气阀开启点压力为7.3MPa,此时发电效率与纯补气方案相比提高2.7%,与纯节流方案相比提高12.6%,具有明显效率提升效果，对其它压缩空气储能透平进气调节方式选型具有明显参考意义。     

CO2与R41跨临界朗肯循环低温发电系统比较分析

本文以R41为工质的跨临界朗肯循环低温发电系统进行了热力性能分析,并与CO_2跨临界发电系统进行比较,结果表明:R41和CO_2系统均存在一个最优进口压力使得热效率在相同的膨胀机进口温度下达到最大值,且膨胀机进口温度越高,对应的最优压力也越大。同热效率一样,系统均存在一个最优进口压力使得净功在相同的膨胀机进口温度下达到最大值,且R41系统比CO_2系统所作的最大净功平均提高52.6%,最优进口压力平均降低41.6%,系统火用效率平均提高24.8%。     

有机工质低温余热发电系统多目标优化设计

针对现有有机朗肯循环单目标优化设计的局限性,从热力性、经济性等多方面对有机工质低温余热发电系统进行多目标优化设计.以系统效率最大和总投资费用最小为目标函数,选取透平进口温度、透平进口压力、余热锅炉节点温差、接近点温差和冷凝器端差等5个关键热力参数作为决策变量,利用非支配解排序遗传算法(NSGA-II)分别对采用R123、R245fa和异丁烷的有机工质余热发电系统进行多目标优化,获得不同工质的多目标优化的最优解集(Pareto最优前沿),并采用理想点辅助法从最优解集中选择出最优解及相应的系统最佳热力参数组合.结果表明:在给定余热条件下,从热力性能和经济性两方面考虑,R245fa是最优的有机工质,从多目标优化的最优解集中选择出的最佳效率为10.37%,最小总投资费用为455.84万元.     

海洋温差能向心透平的气动设计及性能研究

通过对7.5 kW海洋温差能向心透平的蜗壳、喷嘴和叶轮进行气动设计,模拟研究了透平在设计工况及非设计工况下的气动性能。采用经验参数及遗传算法优化方法对透平的一维参数进行设计,得到一维设计结果,并据此对蜗壳、喷嘴和叶轮进行三维设计,得到透平的气动结构造型。利用CFD技术模拟研究了透平的三维流场及性能,得到透平在设计工况及非设计工况下的性能,模拟结果表明:在设计工况下,透平效率为86.5%;在非设计工况下,透平效率随着叶轮转速的增加而增大,但增加至设计转速后,透平效率增加幅度较小;随着进口温度的升高,透平效率逐渐增大;当进口压力为设计工况压力时,透平效率存在最大值;非设计工况下的透平功率基本与叶轮转速、进口压力和进口温度均呈正相关;设计工况下的最佳喷嘴-叶轮相对径向间隙为0.05,可变喷嘴叶片安装角为35～40°。     

初参数对超临界CO2塔式光热发电系统■效率的影响

初参数对塔式光热发电系统热力性能有着重要影响。基于国内外研究现状,文章建立了超临界二氧化碳(S-CO₂)再压缩塔式光热发电系统,研究了不同辐射强度下,该系统不同设备、各子系统和整个系统的(火用)效率,以及吸热器散热损失随透平进口温度和进口压力的变化情况。研究表明：透平进口温度从500℃上升到800℃时,低温回热器(火用)效率最大值为90.21%,对应温度560℃;当辐射强度从95%THA增加到105%THA时,集热子系统(火用)效率最大值点往温度升高的方向偏移且最大值增大,最大为27.88%,对应温度700℃。透平进口压力从20 MPa增加到34 MPa时,循环子系统(火用)效率先增后减,当辐射强度从95%THA增加到105%THA时,其最大值点往压力升高的方向偏移且最大值减小,最大为74.9%,对应压力24 MPa。透平进口压力对吸热器散热损失的影响较小,而进口温度对其影响较大。研究结果可为S-CO₂塔式光热发电系统优化设计提供参考。     

有机朗肯循环热源温度与冷凝温度的影响分析

分析了蒸发器换热过程中热源温度对窄点温差位置的影响,讨论了冷凝温度和热源温度对有机朗肯循环(ORC)系统的影响。随着热源温度的升高,蒸发器窄点温差位置由有机工质蒸发温度处转移到蒸发器有机工质入口温度处。考虑冷却水循环,系统存在最佳冷凝温度,当冷凝温度低于最佳冷凝温度时,净功输出随冷凝温度的降低而急剧下降。给定工况下,最佳冷凝温度随热源温度的增长近似线性升高,热源温度每升高1℃,最佳冷凝温度增长0.035~0.045℃;净功输出随热源温度的升高而增加,上升速度存在转折点,转折发生在热源温度为160~270℃时。     

低温余热有机朗肯循环发电系统热经济性分析

针对工业中排放的低温烟气,建立有机朗肯循环发电系统的热经济分析模型,分析蒸发压力、热源温度及蒸发器最小传热温差对系统经济性能的影响。分析结果表明:热源温度为140℃,循环采用R123的经济性最佳,相应的发电成本与动态投资回收期分别为0.142元(/kW.h)与3.68年。余热发电系统存在一个经济性最高的蒸发压力,不同工质对应的最佳蒸发压力也不同。蒸发器内最小传热温差为15℃时,系统的经济性较好。烟气温度在100～180℃时,系统采用R123的投资回收期最短,而烟气温度高于180℃时,R141b的经济性更高;不宜采用有机朗肯循环发电技术回收温度低于100℃的低温烟气。     

余热发电有机朗肯循环系统性能实验研究

针对90℃热水型余热,以R123为工质,对应用于有机朗肯循环(ORC)系统的径流式汽轮机的喷嘴进行一维稳定流动分析,以单位质量热源水的发电量(比净功)最大为目标函数,开展ORC变工况实验研究。研究表明:R123的临界压力比为0.59~0.67,随工质压力的增大有小幅上升,实验系统需采用缩放喷嘴。系统比净功受换热性能,汽轮机效率,传动-发电效率以及系统总功率等多种因素的综合影响。实验中变蒸发压力最优工况为:蒸发压力0.46 MPa,比净功0.40 kJ/kg;变冷凝压力最优工况为:冷凝压力0.11 MPa,系统比净功0.76 kJ/kg。     

一种超临界二氧化碳布雷顿循环

为提高布雷顿循环热效率,在现有超临界二氧化碳布雷顿循环的基础上,提出一种基于回热技术的分级压缩与分级膨胀相结合的再压缩布雷顿循环方案,运用热力学计算软件EES对该循环参数进行热力学分析。结果表明,当分流系数约为0.47,透平入口温度为950 K,透平入口压力为29.0 MPa时,循环热效率为59%。当透平入口温度一定,分流系数在0.47～0.48时,循环热效率最高。在透平入口压力从20.0往29.0 MPa升高的过程中,最佳分流系数从0.39逐渐增加到0.47。在回热度从0.5增长到0.6的过程中,最佳分流系数从0.47增长到0.50。     

超临界二氧化碳布雷顿/有机朗肯循环联合系统的热力学特性

针对再压缩式超临界二氧化碳布雷顿发电循环(S-CO_2),将有机朗肯循环(ORC)作为底循环用于回收系统余热,建立了S-CO_2/ORC联合循环。采用Aspen Plus建立分析模型,根据顶循环余热温度范围和安全环保要求,选取R245fa作为ORC系统工质,分析透平进口温度、透平进口压力及分流比对循环效率的影响,并通过分析耗能设备的功率变化找到影响系统效率变化的因素。结果表明:通过顶循环低温余热的回收利用,系统热效率提高4%以上;增大透平进口温度可提高顶循环的热效率,但对底循环热效率的影响较小;随着顶循环透平进口压力的增大,顶循环热效率增加而底循环热效率下降;在透平入口温度680℃、入口压力280 MPa的条件下,存在最优的再压缩循环分流比0.66使得联合循环热效率最高;使用ORC底循环回收顶循环余热,最高可以将系统热效率从50.3%提高到53.7%,联合系统可以获得6.7%的效率提升。     

Parametric analysis and optimization of a Kalina cycle driven by solar energy

A solar-driven Kalina cycle is examined to utilize solar energy effectively due to using ammonia–water's varied temperature vaporizing characteristic. In order to ensure a continuous and stable operation for the system, a thermal storage system is introduced to store the collected solar energy and provide stable power when solar radiation is insufficient. A mathematical model is developed to simulate the solar-driven Kalina cycle under steady-state conditions, and a modified system efficiency is defined to evaluate the system performance over a period of time. A parametric analysis is conducted to examine the effects of some key thermodynamic parameters on the system performance. The solar-driven Kalina cycle is also optimized with the modified system efficiency as an objective function by means of genetic algorithm under the given conditions. Results indicate that there exists an optimal turbine inlet pressure under given conditions to maximize the net power output and the modified system efficiency. The net power output and the modified system efficiency are less sensitive to a change in the turbine inlet temperature. An optimal basic solution ammonia fraction can be identified that yields maximum net power output and modified system efficiency. The optimized modified system efficiency is 8.54% under the given conditions.     

Thermodynamic analysis of a transcritical CO2 power cycle driven by solar energy with liquified natural gas as its heat sink

This paper proposes a transcritical CO₂ power cycle driven by solar energy while utilizing the cold heat rejection to an liquified natural gas (LNG) evaporation system. In order to ensure a continuous and stable operation for the system, a thermal storage system is introduced to store the collected solar energy and to provide stable power output when solar radiation is insufficient. A mathematical model is developed to simulate the solar-driven transcritical CO₂ power cycle under steady-state conditions, and a modified system efficiency is defined to better evaluate the cycle performance over a period of time. The thermodynamic analysis focuses on the effects of some key parameters, including the turbine inlet pressure, the turbine inlet temperature and the condensation temperature, on the system performance. Results indicate that the net power output mainly depends on the solar radiation over a day, yet the system is still capable of generating electricity long after sunset by virtue of the thermal storage tank. An optimum turbine inlet pressure exists under given conditions where the net power output and the system efficiency both reach maximum values. The net power output and the system efficiency are less sensitive to the change in the turbine inlet temperature, but the condensation temperature exerts a significant influence on the system performance. The surface area of heat exchangers increases with the rise in the turbine inlet temperature, while changes in the turbine inlet pressure have no significant impact on the heat exchanging area under the given conditions.     

A comparative thermodynamic analysis of Kalina and organic Rankine cycles for hot dry rock: a prospect study in the Gonghe Basin

Hot dry rock is a new type of geothermal resource which has a promising application prospect in China. This paper conducted a comparative research on performance evaluation of two eligible bottoming cycles for a hot dry rock power plant in the Gonghe Basin. Based on the given heat production conditions, a Kalina cycle and three organic Rankine cycles were tested respectively with different ammonia-water mixtures of seven ammonia mass fractions and nine eco-friendly working fluids. The results show that the optimal ammonia mass fraction is 82% for the proposed bottoming Kalina cycle in view of maximum net power output. Thermodynamic analysis suggests that wet fluids should be supercritical while dry fluids should be saturated at the inlet of turbine, respectively. The maximum net power output of the organic Rankine cycle with dry fluids expanding from saturated state is higher than that of the other organic Rankine cycle combinations, and is far higher than the maximum net power output in all tested Kalina cycle cases. Under the given heat production conditions of hot dry rock resource in the Gonghe Basin, the saturated organic Rankine cycle with the dry fluid butane as working fluid generates the largest amount of net power.     

Parametric analysis for a new combined power and ejector–absorption refrigeration cycle

A new combined power and ejector–absorption refrigeration cycle is proposed, which combines the Rankine cycle and the ejector–absorption refrigeration cycle, and could produce both power output and refrigeration output simultaneously. This combined cycle, which originates from the cycle proposed by authors previously, introduces an ejector between the rectifier and the condenser, and provides a performance improvement without greatly increasing the complexity of the system. A parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the cycle performance. It is shown that heat source temperature, condenser temperature, evaporator temperature, turbine inlet pressure, turbine inlet temperature, and basic solution ammonia concentration have significant effects on the net power output, refrigeration output and exergy efficiency of the combined cycle. It is evident that the ejector can improve the performance of the combined cycle proposed by authors previously.     

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.     

空间核能布雷顿循环系统热力学参数分析及优化*

在深空探索快速发展的背景下,空间核能布雷顿循环系统因其能量密度高、环境适应性强、效率高等优势成为深空探测的理想方案之一。与地面发电站不同的是,空间能量转换系统要兼顾系统效率和轻量化的要求,而系统关键参数对系统的效率和质量等性能有着重要的影响。因此,开展热力学参数分析和优化对空间核能布雷顿循环系统的设计具有重要意义。通过建立空间核能布雷顿循环的数学模型和系统部件的质量计算模型,以“质量比功率”为性能优化目标,研究压气机进口温度、压气机压比和涡轮进口温度等参数对系统性能的影响,并采用正交实验法进行优化分析。结果表明,压气机进口温度和压气机压比存在最优值使质量比功率取得最小值,涡轮进口温度升高有利于提高系统的发电效率和降低系统质量。涡轮进口温度的最优值为1 500 K,压气机进口温度的最优值范围为416 ~ 508 K,压气机压比的最优值范围为2.4 ~ 3.1。     

Parametric analysis and optimization for a combined power and refrigeration cycle

A combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the absorption refrigeration cycle. This combined cycle uses a binary ammonia–water mixture as the working fluid and produces both power output and refrigeration output simultaneously with only one heat source. A parametric analysis is conducted to evaluate the effects of thermodynamic parameters on the performance of the combined cycle. It is shown that heat source temperature, environment temperature, refrigeration temperature, turbine inlet pressure, turbine inlet temperature, and basic solution ammonia concentration have significant effects on the net power output, refrigeration output and exergy efficiency of the combined cycle. A parameter optimization is achieved by means of genetic algorithm to reach the maximum exergy efficiency. The optimized exergy efficiency is 43.06% under the given condition.     

Performance analysis of open cycle gas turbines

In this study, the performance of ideal open cycle gas turbine system was examined based on its thermodynamic analysis. The effects of some parameters, such as compressor inlet temperature (CIT), pressure ratio (PR) and the turbine inlet temperature (TIT), on the performance parameters of open cycle gas turbine were discussed. The turbine net power output, the thermal efficiency and the fuel consumption of the turbine were taken as the performance parameters. The values of these parameters were calculated using some basic cycle equations and variables values of thermodynamic properties. Other variables such as lower heating value, combustion efficiency and isentropic efficiencies of compressor and turbine were assumed to be constant. The result showed that the net power output and the thermal efficiency increased by a decrease in the CIT and increase in the TIT and PR values. If it is aimed to have a high net power output and the thermal efficiency for the turbine, the CIT should be chosen as low as possible and the TIT should be chosen as high as possible. Copyright © 2008 John Wiley & Sons, Ltd.     

The effect of elevated inlet air temperature and relative humidity on cogeneration system

The effect of elevated inlet air temperature and relative humidity on a gas turbine (GT) cogeneration system performance was investigated. The analysis was carried out on a GT of a capacity 171 MW at ISO condition, which is integrated with a dual pressure heat recovery steam generator (HRSG), the cogeneration system had been tested under Kuwait summer climate conditions. A computational model was developed and solved using engineering equation solver professional package to investigate the performance of a dual pressure GT‐HRSG system. The suggested HRSG is capable of producing high‐pressure superheated steam at 150 bar and 510°C to operate a power generation steam turbine cycle, and a medium pressure saturated steam at 15 bar to run a thermal vapor compression (TVC) desalination system. In this research, the influence of elevated inlet air temperature and relative humidity on the energy assessment of the suggested cogeneration system was thoroughly investigated. Results indicated that operating GT under elevated values of inlet air temperatures is characterized by low values of net power and thermal efficiency. At elevated inlet air temperatures, increasing relative humidity has a small positive impact on GT cycle net power and thermal efficiency. Integrating the GT with HRSG to generate steam for power generation and process heat tends to increase energy utilization factor of the system at elevated inlet air temperatures. Increasing inlet air temperature plays a negative impact on power to heat ratio (PHR), while relative humidity has no effect on PHR. Copyright © 2009 John Wiley & Sons, Ltd.