基于BOOST的摩托车发动机进气系统优化

针对某款摩托车发动机在特定市场需求高速性能的情况下,运用性能先进模拟软件BOOST对该机进行了分析,找出了影响原机高速性能的主要原因。通过优化进气系统的结构,提高了发动机高速性能。对优化后方案进行了台架试验,高速性能提高11％,中低速性能基本不变,达到预期效果。     

350MW汽轮发电机组性能监测系统

】针对３５０ＭＷ汽轮发电机组的热力性能介绍了一种性能监测系统,该系统选用常规测点作为机组性能监测的基本数据,采用了易于评价机组性能和指导运行调整的性能分析方法。现场运行情况表明,整个系统的设计和实施是合理的,对指导现场的机组运行发挥了重要作用。     

进气道生产一致性对汽油机性能影响及设计优化

采用AVL TIPPLEMAN气道稳态试验台对某现生产气道喷射汽油机缸盖气道性能进行批量测试,结果显示该发动机缸盖气道生产一致性较差。选择了其中高中低3种滚流水平缸盖进行发动机性能试验。试验发现,生产偏差造成的滚流差异对性能有较大的影响,低滚流气道有利于该发动机外特性提升。为此进行了进气道性能鲁棒性CFD模拟分析,研究了气道偏移对气道性能的影响,并通过优化气道局部结构,显著改善了缸盖气道性能设计鲁棒性,优化后气道滚流对气道偏移的敏感度降低了50%,并进行了气道试验验证和发动机性能试验。     

消声器性能的试验研究

设计建成了一个消声器模拟试验台,可对各种排气消声器进行消声性能测试。通过在有、无气流两种情况下的消声性能试验,研究了气流速度对消声性能的影响。就消声器的内部结构尺寸及形状对消声性能的影响进行了试验研究,通过对比分析总结了不同结构参数对消声性能的影响。     

汽油发动机喷油器结构改进设计

为进一步提高电控喷油器的工作性能,尤其是电磁响应性能和喷射雾化性能,以阀芯动力学模型为基础,利用Star-CD流体动态模拟软件进行燃油动态模拟分析,对底座结构设计进行了改进,增加燃油在喷口前的横向流动趋势,容易产生流动涡旋,改善了燃油雾化性能。优化阀芯结构可以提高喷油器的电磁响应性能。改进前后喷油器的性能测试对比试验结果表明:改进后的喷油器电磁响应时间缩短了0.3 ms,燃油索特平均直径由95μm降至65μm,有利于排放性能的改善。以球阀结构代替针阀结构,激光焊接工艺代替精密磨削,不但提高了生产效率,还能降低制造成本。     

高弹性联轴器隔振性能预测研究

以LS型高弹性联轴器作为研究对象,采用软件仿真与试验验证相结合的方法对高弹性联轴器隔振性能预测技术进行了研究。基于有限元理论提出了高弹性联轴器隔振性能计算评估方法,计算分析了弹性联轴器的模态特性和隔振性能。通过试验研究得到高弹的模态频率、振型及隔振性能曲线。计算值与实测值吻合较好,验证了高弹性联轴器隔振性能有限元评估方法的可行性。     

不同运行工况下给水加热器端差特性的计算分析

给水加热器端差性能,随机组运行工况的变化而变化。对ASME加热器性能试验标准中采用的加热器性能计算方法进行了介绍,并对利用这种方法进行加热器端差性能的变工况计算进行了说明。针对某一国外机组提供的加热器变工况特性进行了核算,计算结果表明,采用ASME标准中提供的方法进行加热器性能变工况计算后得到的结果,与厂家提供的性能特性能较好的吻合。采用的方法在计算加热器特性时有明显的优势。     

涡轮箱0-0截面对柴油机性能影响的计算研究

针对传统的涡轮箱0-0截面选配方法在发动机性能调试过程中存在的周期长、成本高等问题,利用AVL BOOST发动机性能分析软件建立了不同涡轮箱0-0截面积的某12V150柴油机性能计算模型,分析了涡轮箱0-0截面积对柴油机性能的影响规律,并通过试验进行了验证,为柴油机性能改进奠定了基础。     

两种非对称翼风力机性能的试验研究

在低速风洞中对两种非对称翼型(3734和GOE382)小型垂直轴风力机的自启动性能和功率输出性能进行了测试,研究了叶片数和来流风速对两种翼型的风力机性能的影响。结果显示,非对称翼3734风力机的静态自启动性能劣于GOE382,但功率输出性能优于GOE382风力机。     

对9FA燃气轮机联合循环机组性能试验的思考

对9FA燃机联合循环性能试验中的一些问题进行了分析,如性能的修正、余热锅炉的性能考核、责任分摊等,并给出了作者的看法,供同行参考。     

氟利昂引射式制冷机的性能研究

本文研究了引射式制冷机的性能,当工质采用氟利昂时,可以利用低位热能来制冷,编制了计算机仿真程序,分析了状态参数对制冷机性能的影响。计算结果表明这一装置适合于空调系统。     

Study on performance of solar assisted air source heat pump systems for hot water production in Hong Kong

This paper reports the investigation results on application of the solar assisted air source heat pump systems for hot water production in Hong Kong. A mathematical model of the system is developed to predict its operating performance under specified weather conditions. The optimum flow rate from the load water tank to the condenser is proposed considering both the appropriate outlet water temperature and system performance. The effect of various parameters, including circulation flow rate, solar collector area, tilt angle of solar collector array and initial water temperature in the preheating solar tank is investigated, and the results show that the system performance is governed strongly by the change of circulation flow rate, solar collector area and initial water temperature in the preheating solar tank.     

Model-based optimal control of a dedicated outdoor air-chilled ceiling system using liquid desiccant and membrane-based total heat recovery

This study presents a model-based control strategy for a novel dedicated outdoor air-chilled ceiling (DOAS-CC) system with the aim of optimizing the overall system performance. The DOAS-CC system incorporates liquid desiccant dehumidification and membrane-based total heat recovery technologies. Simplified but reliable models of major components in the DOAS-CC system are firstly developed to predict the system performance. A cost function is then constructed to minimize total energy consumption while properly maintaining thermal comfort reflected by indoor air temperature and relative humidity. Genetic algorithm is used to search for optimal set-points of the supply air temperature and humidity ratio of the dedicated outdoor air subsystem as well as the supply water temperature. The performance of this strategy is tested and evaluated with different control settings in a simulated multi-zone space served by the DOAS-CC system under various weather conditions. The results show that optimized control variables produced by the optimal strategy can improve the system energy performance and maintain indoor thermal comfort.     

Thermal performance of a direct expansion solar-assisted heat pump

A direct expansion solar assisted heat pump, in which a bare flat plate collector also acts as the evaporator for the refrigerant, Freon-12, is designed and operated. The system components, e.g. the collector and the compressor, are properly matched so as to result in system operating conditions wherein the collector/evaporator temperature ranges from 0 to 10°C above ambient temperature under favorable solar conditions. This operating temperature range is particularly favorable to improved heat pump and solar collector performance. The system thermal performance is determined by measuring refrigerant flow rate, temperature and pressure at various points in the system. The heat pump COP_H and the solar collector efficiency ranged from 2.0 to 3.0 and from 40 to 70 per cent, respectively, for widely ranging ambient and operating conditions. Experimental results indicate that the proposed system offers significant advantage in terms of superior thermal performance when compared with results gotten by replacing the solar evaporator with a standard outdoor fan-coil unit.     

Performance of ejector heat pumps

An ejector-compression heat pump can use low-grade thermal energy in the neighbourhood of 93.3°C (200°F) to provide space cooling and heating. This paper applies the existing ejector theory to estimate the performance of an ejector heat pump system at various operating conditions. The study includes parametric, sensitivity and off-design analyses of the heat pump performance. The performance enhancement options and desired ejector geometry are also examined. Refrigerants 11, 113 and 114 are three of the halocarbons most suitable for the ejector heat pump system. The estimated coefficients of performance for a simple ejector heat pump are 0.3 for the cooling mode and 1.3 for the heating mode at a sample operating condition in which the refrigerant (R-11) boiling temperature is 93.3°C (200°F), condensing temperature 43.3°C (110°F) and evaporating temperature 10°C (50°F). A 24 per cent performance improvement is predicted for a heat pump with two-stage ejectors and regenerative heat exchangers. The off-design performance is relatively insensitive to the evaporator temperature variations.     

Analysis of the design of a pressurized SOFC hybrid system using a fixed gas turbine design

Design characteristics and performance of a pressurized solid oxide fuel cell (SOFC) hybrid system using a fixed gas turbine (GT) design are analyzed. The gas turbine is assumed to exist prior to the hybrid system design and all the other components such as the SOFC module and auxiliary parts are assumed to be newly designed for the hybrid system. The off-design operation of the GT is modeled by the performance characteristics of the compressor and the turbine. In the SOFC module, internal reforming with anode gas recirculation is adopted. Variations of both the hybrid system performance and operating condition of the gas turbine with the design temperature of the SOFC were investigated. Special focus is directed on the shift of the gas turbine operating points from the original points. It is found that pressure loss at the fuel cell module and other components, located between the compressor and the turbine, shifts the operating point. This results in a decrease of the turbine inlet temperature at each compressor operating condition relative to the original temperature for the GT only system. Thus, it is difficult to obtain the original GT power. Two cell voltage cases and various degrees of temperature difference at the cell are considered and their influences on the system design characteristics and performance are comparatively analyzed.     

An analysis of a packed bed latent heat thermal energy storage system using PCM capsules: Numerical investigation

This paper is aimed at analyzing the behavior of a packed bed latent heat thermal energy storage system. The packed bed is composed of spherical capsules filled with paraffin wax as PCM usable with a solar water heating system. The model developed in this study uses the fundamental equations similar to those of Schumann, except that the phase change phenomena of PCM inside the capsules are analyzed by using enthalpy method. The equations are numerically solved, and the results obtained are used for the thermal performance analysis of both charging and discharging processes. The effects of the inlet heat transfer fluid temperature (Stefan number), mass flow rate and phase change temperature range on the thermal performance of the capsules of various radii have been investigated. The results indicate that for the proper modeling of performance of the system the phase change temperature range of the PCM must be accurately known, and should be taken into account.     

Transient simulation of a capacity-modulated, direct-expansion, solar-assisted heat pump

The long-term thermal performance of a direct-expansion, solar-assisted heat pump is determined from the transient simulation of the system. The system employs a bare collector that also acts as the heat pump evaporator. Of particular interest in this study is the configuration in which the compressor and the collector area are properly matched from the long-term thermal performance point of view. This matching is achieved through multistep as well as two-step compressor capacity modulation. In addition to examining the effects of compressor capacity modulation, the effects of various system parameters such as collector area, storage volume, load temperature, wind speed, collector slope, and refrigerant properties are also studied in detail.Monthly averaged thermal performance parameters such as the heat pump system coefficient of performance are determined by executing a computer simulation program that uses the typical meterological year (TMY) solar data for Norfolk, Virginia. Results indicate that the system performance is governed strongly by collector area, compressor RPM, load temperature, and refrigerant properties. The remaining parameters have only weak influence on the long-term system performance of direct expansion solar-assisted heat pump (SAHP) system considered in this study.     

Thermal performance of a packed bed reactor for a high‐temperature chemical heat pump

The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high‐temperature heat above 800°C, is studied experimentally. The thermal performance of a packed‐bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high‐temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high‐temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high‐temperature process is proposed for high‐efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd.     

Analysis of optimization in an OTEC plant using organic Rankine cycle

This study quantified the effects of evaporation temperature, condensation temperature, and the inlet- and outlet-temperature differences of deep cold seawater and warm seawater on the performance of an ocean thermal energy conversion (OTEC) plant using an organic Rankine cycle (ORC), and also investigated the optimal operations required for the performance. A finite-temperature-difference heat transfer method is developed to evaluate the objective parameter, which is the ratio of net power output to the total heat transfer area of heat exchanger in the system, and R717, R600a, R245fa, R152a, and R134a were used as the working fluids. The optimal evaporation and condensation temperatures were obtained under various conditions for maximal objective parameters in an OTEC system.The results show that R717 performed optimally in objective parameter evaluation among the five working fluids, and that R600a performed better than other fluids in thermal efficiency analysis. The optimal seawater temperature differences between the inlet and outlet of the evaporator and condenser are proposed. Furthermore, the influences of inlet temperatures of warm and cold seawater in the ORC are presented for an OTEC plant. The simulation results should enable the performance of an ORC system to be compared when using various organic working fluids.