应用于钠冷快堆的超临界二氧化碳动力转换系统研究

超临界二氧化碳（SCO₂）布雷顿循环由于高效、紧凑和可避免钠水反应等特性而成为钠冷快堆的理想动力转换系统。本文以1 200 MWe大型池式钠冷快堆为系统热源，钠回路温度及热负荷为循环系统运行边界，对比研究了不同SCO₂布雷顿循环系统性能和关键设备性能的变化规律。研究发现，级间冷却再压缩循环与钠冷快堆热源特性匹配性最佳，且循环效率最高（40.7%）。进而研究了不同运行参数对级间冷却再压缩循环效率的影响规律，给出了循环系统效率对各关键影响因素的敏感度，发现循环系统效率对冷端参数的敏感度最强，其次为分流比和透平入口参数，对主压缩机级间压比的敏感度最弱。     

超临界二氧化碳布雷顿循环热力学特性研究

基于热力学第一定律,开展超临界二氧化碳(S-CO_2)布雷顿循环的热力学特性研究。在设备模型构建和初始条件假设的基础上,研究系统采用再压缩循环的热力学特性和参数限制条件。针对进出口温差较大的热源系统,提出了复叠式分流循环方案,开展热力学特性分析和评价,并与再压缩循环进行定量比较,得出各自的适用对象。     

超临界二氧化碳布雷顿循环的参数优化

本文通过建立二氧化碳布雷顿再压缩循环模型,研究了各参数对循环效率的影响及各参数间的关系,并对循环参数进行优化,阐述二氧化碳循环高效能量转换的机理。结果表明,超临界二氧化碳再压缩循环是一种较为理想的能量转换方式,适宜为出口温度较低的反应堆做能量转换。     

熔盐堆超临界二氧化碳布雷顿循环系统与热力学分析

熔盐堆（MSR）能实现在线填料和后处理,出口温度较高,应配备一种与之出口温度相匹配的创新型循环方式,且可达到较高的循环效率。本文基于中国科学院上海应用物理研究所设计的小型模块化熔盐堆（smTMSR-400）设计超临界二氧化碳（SCO₂）布雷顿循环系统,使用控制变量法分析了分流比、压缩机/透平效率、主压缩机出口温度、低温换热器换热温差/阻力对SCO₂布雷顿循环系统的影响。分析结果表明:①存在最佳分流比使低温换热器两侧温差相等;②相较于压缩机效率,等幅度的透平效率提升可使系统循环效率和?效率更高;③主压缩机出口压力增大为系统带来正面影响,但循环效率/?效率与其斜率都逐渐降低;④换热器换热温差和流动阻力都为系统循环带来了可量化的负担: 换热温差每增加10 K,循环效率降低1.85%,?效率降低2.70%;流动阻力每增加1 MPa,循环效率降低6.58%,?效率降低10.22%。最后根据分析结果和系统?流变化设计了5种物理参考方案。      

直接布雷顿循环气冷反应堆系统运行特性分析

基于Matlab/simulink程序，针对小型直接布雷顿循环反应堆系统，通过模块化思想建立该系统数学物理模型，开发了系统分析程序。通过改变反应堆、透平、压缩机、换热器等关键设备的运行参数或引入阶跃扰动，模拟了系统稳态工况与瞬态变工况运行，得到了关键设备功率、进出口压力、温度等关键参数的变化曲线。结果表明，系统分析程序对小型直接布雷顿循环反应堆系统稳态与瞬态运行特性的模拟结果较合理，能为小型直接布雷顿循环反应堆系统的设计、优化与安全分析提供依据。     

超临界二氧化碳动力循环在钠冷快堆中的应用综述

超临界二氧化碳循环系统在气冷快堆、铅冷快堆、钠冷快堆中极具应用前景。综述了应用于钠冷快堆的超临界二氧化碳动力循环系统及其样机关键部件研究现状和有关进展,结合钠冷快堆的热源特征,分别就典型超临界二氧化碳动力循环结构、印刷电路板式换热器换热特征系数、不同功率等级S-CO_2压缩机与透平类型选择以及轴承与密封关键特征进行了总结与分析,分析结果为后续开展适用于钠冷快堆的S-CO_2布雷顿循环设计及样机开发提供可借鉴的参考与依据。     

兆瓦级核电推进系统布雷顿循环热电转换特性分析

闭式布雷顿循环是兆瓦级核电推进系统主要采用的动态热电转换方式，具有结构简单、转换效率高等特点。本文针对兆瓦级核电推进系统的动态布雷顿热电转换方式进行特性分析，具体内容包括：对氦气、氮气、二氧化碳和氙气4种工质及它们以不同比例混合的工质的热物性进行比较，进而对其在兆瓦级核电推进系统闭式布雷顿循环中的换热性能、压力损失系数和透平机械所需级数进行分析；以带有同流换热器和预冷器的直接气体透平循环为研究对象，比较兆瓦级核电推进系统气体透平循环在采用不同比例混合物作为工质时的循环效率，并对参数变化对循环效率的影响进行研究。本研究为兆瓦级核电推进系统气体透平循环在工质选择方面提供了一定的参考，为其设计和控制系统的研究奠定了基础，为以后进行气体透平循环动态性能研究打下了基础。     

矩形回路内超临界二氧化碳自然循环实验研究

为认识超临界二氧化碳自然循环基本特性,开展超临界二氧化碳在简单矩形回路内自然循环特性的实验研究,研究系统压力和冷热段流体温差对自然循环流量的影响,分析回路结构对自然循环特性的影响。结果表明:循环流量存在峰值;峰值点前,随加热功率增加流量快速上升,峰值点后流量变化平缓;在本试验参数条件下未观测到流动不稳定现象;压力对循环流量影响与亚临界自然循环类似,压力越高循环流量峰值越大,回路冷热段温差对循环流量影响较大;加热段出口流体温度接近拟临界温度时,很小的回路温差变化即可引起循环流量较大变化;加热段布置方式对超临界二氧化碳自然循环流量变化特性影响较大,对回路稳定性的影响需要进一步进行实验验证。     

氟盐冷却高温堆空气布雷顿循环系统瞬态行为研究

基于Mark-1氟盐冷却高温堆(FHR)系统的热力循环特点,研究FHR耦合空气布雷顿循环系统的热电转换效率。通过研究压气机与透平计算方法,在其实际工作特性曲线的基础上,分析布雷顿循环空气温度和流量变化对FHR系统的影响,以及在非额定工况下运行时系统效率的瞬态变化规律。计算结果显示系统,循环效率随着空气流量增加而逐渐下降,最高可达42.6%;空气流量变化量在小于5%额定流量范围内使循环效率变化幅度小于2%,但超出该范围后可根据效率变化曲线选择不同的系统再热运行方案;此外循环效率随着空气入口温度增加逐渐下降,系统效率变化幅度在1%以内。     

直接布雷顿循环气冷反应堆系统运行特性分析

基于Matlab/simulink程序,针对小型直接布雷顿循环反应堆系统,通过模块化思想建立该系统数学物理模型,开发了系统分析程序。通过改变反应堆、透平、压缩机、换热器等关键设备的运行参数或引入阶跃扰动,模拟了系统稳态工况与瞬态变工况运行,得到了关键设备功率、进出口压力、温度等关键参数的变化曲线。结果表明,系统分析程序对小型直接布雷顿循环反应堆系统稳态与瞬态运行特性的模拟结果较合理,能为小型直接布雷顿循环反应堆系统的设计、优化与安全分析提供依据。     

Supercritical Carbon Dioxide Power Conversion System Applied to Sodium-cold Fast Reactor

Because of the high efficiency, compactness and avoiding sodium water reaction, the supercritical carbon dioxide (SCO₂) Brayton cycle is an ideal power conversion system for sodium-cooled fast reactors. In this paper, the 1 200 MWe Sodium-cooled Fast Reactor was used as the heat source of the system, and the temperature and heat load of the sodium loop were used as the operating boundary of the circulation system. The system performance and key equipment performance of different supercritical carbon dioxide Brayton cycles were compared. The coupling between the inter-stage cooling and recompression cycle and the characteristics of the heat source of the sodium-cooled reactor is the best, and the cycle efficiency is the highest (40.7%). Furthermore, the influence of different operating parameters on the efficiency of the inter-stage cooling and recompression cycle was studied, and the sensitivity of the efficiency of the circulation system to each of the key influencing factors was given. It is found that the efficiency of the circulation system is the most sensitive to the cold-end parameters, followed by the split ratio and turbine inlet parameters, and the weakest to the main compressor inter-stage pressure ratio.     

Investigation of alternative layouts for the supercritical carbon dioxide Brayton cycle for a sodium-cooled fast reactor

Analyses of supercritical carbon dioxide (S-CO₂) Brayton cycle performance have largely settled on the recompression supercritical cycle (or Feher cycle) incorporating a flow split between the main compressor downstream of heat rejection, a recompressing compressor providing direct compression without heat rejection, and high and low temperature recuperators to raise the effectiveness of recuperation and the cycle efficiency. Alternative cycle layouts have been previously examined by Angelino (Politecnico, Milan), by MIT (Dostal, Hejzlar, and Driscoll), and possibly others but not for sodium-cooled fast reactors (SFRs) operating at relatively low core outlet temperature. Thus, the present authors could not be sure that the recompression cycle is an optimal arrangement for application to the SFR. To ensure that an advantageous alternative layout has not been overlooked, several alternative cycle layouts have been investigated for a S-CO₂ Brayton cycle coupled to the Advanced Burner Test Reactor (ABTR) SFR preconceptual design having a 510 °C core outlet temperature and a 470 °C turbine inlet temperature to determine if they provide any benefit in cycle performance (e.g., enhanced cycle efficiency). No such benefits were identified, consistent with the previous examinations, such that attention was devoted to optimizing the recompression supercritical cycle. The effects of optimizing the cycle minimum temperature and pressure are investigated including minimum temperatures and/or pressures below the critical values. It is found that improvements in the cycle efficiency of 1% or greater relative to previous analyses which arbitrarily fixed the minimum temperature and pressure can be realized through an optimal choice of the combination of the minimum cycle temperature and pressure (e.g., for a fixed minimum temperature there is an optimal minimum pressure). However, this leads to a requirement for a larger cooler for heat rejection which may impact the tradeoff between efficiency and capital cost. In addition, for minimum temperatures below the critical temperature, a lower heat sink temperature is required the availability of which is dependent upon the climate at the specific plant site.     

Flow and Heat Transfer Characteristics of Swordfish Fin Microchannel

The supercritical carbon dioxide Brayton cycle is a new generation of thermal cycle used in the fourth generation of nuclear energy. As a high or low temperature recuperator of supercritical carbon dioxide Brayton cycle, the thermal hydraulic characteristics of the compact microchannel heat exchanger directly affect the power cycle efficiency. Reducing flow resistance of the temperature recuperator while maintaining high heat transfer efficiency is an important research for microchannel heat exchanger optimization design. The swordfish fin microchannel design considering bionics theory can significantly reduce the flow resistance. In this work, the swordfish fin heat exchanger model was established with supercritical carbon dioxide fluid as the flow medium. The effect of swordfish fin design with different arrangements on heat transfer characteristics was analyzed by three-dimensional numerical simulation. At the same time, the thermal hydraulic characteristics of swordfish fin design were compared with those of traditional commercial Z-shaped microchannel heat exchanger. The results show that under the same Reynolds number, the Nusselt number of the swordfish fin microchannel is twice as much as that of the Z-shaped microchannel, but the pressure drop is only half of that. Therefore, the thermal hydraulic performance of swordfish fin microchannel heat exchanger is obviously better than that of Z-shaped heat exchanger. It is obtained from optimization analysis that the optimal pitches for swordfish fin design is that the L_a＝8 mm along the flow direction, and the L_b＝6 mm perpendicular to the flow direction.     

箭鱼形翅片微通道流动换热特性研究

超临界二氧化碳布雷顿循环是第4代核能采用的新一代热能循环系统。紧凑式微通道换热器作为超临界二氧化碳布雷顿循环的高低温回热器，其流动换热特性直接影响整体热电转化的效率。降低回热器的流动阻力，同时维持较高的换热效率是微通道换热器优化设计的重要研究内容。箭鱼形翅片微通道设计借鉴仿生学原理，理论上可显著降低流动阻力。本文以超临界二氧化碳为流动工质，建立箭鱼形翅片换热器的模型并进行三维数值模拟，分析不同排列下的箭鱼形翅片设计对换热器流动换热特性的影响。同时对箭鱼形翅片设计与传统商用折线形微通道换热器流动换热特性进行对比分析。研究分析表明，在相同雷诺数下，箭鱼形翅片微通道的努塞尔数为折线形流道的2倍，而压降仅为其1/2，所以箭鱼形翅片微通道换热器的流动换热特性明显优于折线形换热器。通过优化分析，发现箭鱼形翅片设计最优的排列间距为沿流动方向的翅片间距L_a＝8 mm，垂直于流动方向的翅片间距L_b＝6 mm。     

Feasibility analysis of two-phase MHD energy conversion for liquid metal cooled reactors

A two-phase MHD energy conversion unit is proposed to a liquid metal cooled fast reactor. Using supercritical CO₂ as the working fluid in the gas cycle without considering friction and heat losses, the optimized cycles efficiency is obtained, which is about 5% higher than that of the gas turbine Brayton cycle with the same regenerator/compressor configurations. Based on a simple MHD power analysis and the two-phase homogeneous flow model, the important system operational conditions were estimated. The results suggest that a liquid lead pump of at least 20% of the MHD power output is needed in order to convert the 400 MW reactor heat into electricity at the specified thermal efficiency, unless a mixture foam flow of void fraction greater than 80% is achievable at very high mixture velocity.     

小型氟盐冷却高温堆耦合布雷顿循环系统分析与研究

为满足小型氟盐冷却高温堆（FHR）能量转换需求,开发与之匹配的高效、紧凑、无水冷却动力转换系统,本文对比了超临界二氧化碳（SCO₂）、空气、氩气（Ar）、氮气（N₂）、氙气（Xe）5种气体工质在不同布雷顿循环构型中的热电转换效率、?效率、?损失分布。研究发现,SCO₂布雷顿循环相比其它工质循环具有最高的热电转换效率和?效率,且结构更为紧凑,易于小型化和模块化,与小型氟盐冷却高温堆耦合更具优势;进而对SCO₂布雷顿循环进行构型优化,得出匹配小型氟盐冷却高温堆的最佳循环构型方式,构成固有安全模块化小型氟盐冷却高温堆热电转换系统,为西部能源利用提供新研究思路。