环保用板翅式换热器的数值模拟与试验研究

选取矩形截面平直翅片板翅式换热器的矩形单通道运用fluent软件进行数值模拟。首先对不同波高和波距的三组九种几何尺寸的翅片在同一工况下进行数值模拟,选出每组中传热和阻力综合性能最优者。然后对选出的三种翅片在不同工况下进行数值模拟,最终选出一种传热和阻力综合性能最优的。并对实物换热器进行试验研究,同时将试验结果和数值模拟结果进行对比分析,验证了数值模拟的正确性。     

稀疏气固两相流动中颗粒分离特性的数值模拟

针对循环流化床铁矿粉烧结技术中的关键问题,用数值模拟方法对不同密度床料颗粒在床内的分布进行了数值模拟。数值模拟将气相场和离散颗粒场分别用欧拉方法和拉格朗日方法进行处理,在每一时间步长内对气相场和离散颗粒场的相互作用进行耦合,得出了不同密度混合床料在循环流化床内的分离规律。数值模拟结果与国外相同研究的实验结果进行了对比,结果表明数值模拟结果具有较高的准确性。     

发动机冷却水三维流动数值模拟基础研究

本文在作者已完成的不可压缩流体三维流动数值模拟研究的基础上，对发动机冷却水三维流动的数值模拟方法进行了基础性研究。文章对具有发动机冷却水腹复杂形状的箱体内的水进行了三维流动模拟计算，介绍了数值模拟的基本方法，并对计算结果进行了分析，说明了该方法的有效性。该文介绍的内容是深入研究实际发动机冷却水三维流动数值模拟的基础。     

多流体模型在燃气轮机燃烧室三维反应流中的应用

对一种模型燃气轮机燃烧室中的三维反应流进行了数值模拟，模型燃烧室的燃料是CH4，燃烧类型是预混燃烧，在数值模拟过程中，采用了Spalding于1995年提出来的多流体模型来对燃烧室中的湍流预混燃烧进行了数值模拟，在数值模拟过程中考虑了辐射问题，采用了六通量辐射模型。通过数值模拟给出了速度，压力，湍流脉动动能，湍流动能耗散率，焓值，湍流粘度，温度，密度，燃烧产物质量分数，氧的质量分数，燃料/空气混合比，燃料质量分数，空间三个方向的辐射热通量以及各种流体的质量分数等变量的分布情况，此外，还采用传统的旋涡破碎模型对此燃烧室进行了数值模拟，并对两种方法的结果进行了分析比较，由分析可以看出多流体模型的结果接近于实际情况，对模型燃烧室进行三维反应流数值模拟的工作为今后对实际燃烧室反应流的数值模拟打下了一定的基础。     

层燃垃圾焚烧炉炉内燃烧工况的热态数值模拟

燃烧过程的数值模拟以计算机为桥梁,把燃烧理论、实验和燃烧设备三者有机地结合起来,对燃烧学的发展具有重要的科学价值和实际意义,目前已成为实验技术的有益补充。对垃圾焚烧炉的热态数值模拟主要包括对炉内的温度场的分布进行了数值模拟。根据垃圾焚烧炉膛的温度场分布可以判断燃烧工况的优劣,从而考核炉拱的性能。因此,对垃圾焚烧炉进行热态数值模拟具有极其重要的意义。对8个热态工况下的炉内温度场进行了数值模拟,其结果与热态试验定性一致,从而证实了热态数值模拟的可信性,对实际工程设计有一定的参考价值。     

柴油机排气道数值模拟和优化设计

使用Fluent软件对不同气门升程的排气道流场进行CFD数值模拟,并将计算结果同试验数据进行对比,发现两种方法获得的流量数据吻合良好。通过对数值模拟结果进行分析,指出了排气道改进的方向,改进后排气道的数值模拟结果显示流量系数获得较大提升。     

小型家用中央空调气流组织数值模拟

本文用FLUENT软件对小型家用中央空调气流组织进行数值模拟,以热线风速仪法测定流场辅助数值模拟验证。通过对原始模型数值模拟计算,提出了改善与优化测试室气流组织的方法。     

风力机叶片三维流动特性与气动性能的数值分析

采用基于雷诺平均的三维可压N-S方程,对美国国家可再生能源实验室开发的PhaseⅥ实验风力机叶片在7m/s来流下的绕流流场进行全三维数值模拟.通过对数值模拟得到的叶片表面压力分布与实验测量值的比较,验证了数值模拟的有效性,并在此基础上分析了叶片各截面的失速情况、叶片的三维绕流特性以及叶展方向上的升阻力系数与功率分布.数值模拟数据显示,相比简单的对二维数值模拟结果进行堆叠,全三维的数值模拟能够更准确的反映叶片绕流的气动特性.     

太阳能热气流电站中涡轮机流动特性分析

对太阳能热气流电站中的涡轮机进行了设计和数值模拟.建立了涡轮机区域流体流动的物理数学模型,并对其进行数值模拟;研究了涡轮机的转速与压降对涡轮机的流量、输出功率和能量转换效率的影响.通过与相近实验模型的试验结果对比,证明了设计方案和数值模拟方法是有效的.     

弯道水流特性和数值模拟方法研究进展

在分析弯道水流基本特性的基础上对弯道水流数值模拟方法进行了归纳,分析了数值模拟的关键因素自由水面的模拟方法,并对复式断面弯道水流等复杂弯道流的研究进展进行了评述,对未来研究方法和趋势作了展望.     

一种新型空气预热器及其性能分析

提出了一种新型空气预热器,该预热器依靠8个阀门的不同开闭来控制空气与烟气交替流过2个蓄热体,从而实现烟气对空气的加热.分析表明,新型空气预热器与回转式空气预热器相比,漏风率大大降低,不到3%.     

A two-pass solar air heater

An air heater, in which the air first flows between metallic and cover plates and is then made to flow between two metallic plates in opposite direction, is discussed theoretically. The governing equations of the model are solved explicitly under suitable conditions. The measured values of the solar insolation and ambient temperature are represented by Fourier series. The effects of collector length and flow rate have been studied. The air heater in this mode of operation is more efficient than one in which air flows between two metallic plates in the same direction, provided the plate length is less than 5 m.     

CONVECTIVE AND DIFFUSIVE PHENOMENA OF AIR IN A VERTICAL CYLINDER UNDER A STRONG MAGNETIC FIELD

Transient characteristics of air flow in a vertical pipe under a superconducting magnet were studied numerically with new mathematical modeling equations of magnetizing force. Air is a paramagnetic fluid and has an exceptionally large magnetic susceptibility. The distribution of the magnetic field in the bore of a superconducting magnet was calculated by Biot-Savart's law. When the vertical cylinder was filled initially with hot air, the hot air was repelled from the pipe upward immediately, due to the buoyancy and magnetizing forces. However, when the vertical pipe was filled initially with cold air, the cold air was sustained for a long time due to the magnetizing force overcoming the buoyancy force.     

A hybrid aluminum/hydrogen/air cell system

A hybrid aluminum/hydrogen/air cell system is developed to solve the parasitic hydrogen-generating problem in an alkaline aluminum/air battery. A H₂/air fuel cell is integrated into an Al/air battery so that the hydrogen generated by the parasitic reaction is utilized rather than wasted. A systematic study is conducted to investigate how the parasitic reaction and the added H₂/air cell affect the performance of the aluminum/air battery. The aluminum/air sub-cell has an open circuit voltage of 1.45 V and the hydrogen/air sub-cell of 1.05 V. The maximum power density of the entire hybrid system increases significantly by ∼20% after incorporating a H₂/air sub-cell. The system maximum power density ranges from 23 to 45 mW cm⁻² in 1–5 M NaOH electrolyte. The hybrid system is adaptable in concentrated alkaline electrolyte with significantly improved power output at no sacrifice of its overall efficiency.     

Air fuelled zero emission road transportation: A comparative study

Road transportation using air as a fuel has attracted much attention over the past decade. The fuel (air) can be in two forms, compressed gas form and cryogenic liquid form and engines based on both forms of air have been investigated. Prototypes of air powered road vehicles are expected to emerge over the next few years. However, there have been debates over the advantages and disadvantages of the two technologies. This paper aims to compare the two technologies from the technological point of view. Engines for a typical small scale passenger car are used for the analyses and the comparison is based on the shaft work, coolth, efficiency and energy density. It is shown that the shaft work outputs and the coolth available to engines powered by both fuels increase with increasing working pressure and temperature. Given the working pressure and temperature, liquid air powered engines have a slightly lower specific work outputs than compressed air powered engines. The volumetric energy density of liquid air, however, is much higher than that of compressed air, and liquid air has much higher coolth than compressed air. On the other hand, the efficiency of the compressed air powered engines is higher than that of liquid air powered engines mainly because of the higher energy consumption of liquefaction plants. The analyses also suggest that an effective use of coolth be a key to improve the overall efficiency of liquid air powered engines.     

A design procedure for solar air heating systems

A natural extension of the design procedure for liquid-based solar space and water heating systems is a similar analysis for solar heating systems using air as the heat transfer fluid. In this paper, a solar air heating system incorporating a flat-plate air heater and packed bed thermal storage is described and a simulation model for the system is developed. The results of many simulations of the air heating system are used to establish the relationship between system performance and the system design and meteorological variables. The results are presented in analytic and graphical form, referred to as an f-chart for solar air heating systems. The results of simulations in several widely different climates suggest that the information presented in the f-chart is location independent. Methods of estimating the performance of air heating systems having a collector air capacitance rate and a storage capacity other than those used to generate the f-chart are included. A comparison of the performance of air and liquid based systems is afforded by a comparison of their respective f-charts. The air system is shown to perform better at high load fractions supplied by solar energy than a liquid-based system with the same collector thermal performance parameters.     

一种简易可行的VAV空调系统

文章介绍了一种简易的VAV（Variable Air Volume）空调系统，此 房间温度控制采用数字式温控器结合风阀执行器来实现，空调送风机采用变频控制，固定新风量比，保证新风量在设定范围之内，实现运行证明与常规的VAV空调系统比较，这种系统不但初投资小，而且筒易可行，是一种较好的空调节能系统。     

A two-stage burner

This new design of burner achieves improved fuel combustion by combining (i) a primary diffusion-flame from a wick with (ii) a secondary premixed-flame. The latter occurs as a result of fuel being vaporized by radiant heat from the diffusion flame and that vapour being mixed by convection with air entrained through an orifice. The efficiency of the diffusion-flame combustion is improved because the entrained air is introduced near the centre of the annular flame, so increasing the air/flame interface available for combustion.     

A review on roughness geometry used in solar air heaters

The use of an artificial roughness on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the duct of a solar air heater. Number of geometries of roughness elements has been investigated on the heat transfer and friction characteristics of solar air heater ducts. In this paper an attempt has been made to review on element geometries used as artificial roughness in solar air heaters in order to improve the heat transfer capability of solar air heater ducts. The correlations developed for heat transfer and friction factor in roughened ducts of solar air heaters by various investigators have been reviewed and presented.     

竖直通道内相邻气泡对上升的直接数值模拟

采用Level Set方法和耦合表面张力模型的Navier-Stokes方程,结合ALE数值算法,直接模拟了竖直通道内两个相邻气泡的上升。重点研究不同空间布置的8mm气泡对后面的尾迹流及其相互作用。数值模拟准确再现气泡对的变形、吸引及排斥行为,气泡上升速度计算结果与经验式吻合。模拟结果表明,两个气泡后面的尾迹流及其相互作用决定了上升气泡对的行为。并排上升的气泡对,由于尾流区被一个射流流动分隔,气泡对没有聚并;然而当垂直上升气泡对中的尾随气泡有超过50%的投影面积进入到前头气泡的尾流区,聚并现象发生。