The analysis for the efficiency properties of the fuel cell engine

In this paper, the efficiency properties of the single fuel cell and the fuel cell stack have been analyzed theoretically, and the efficiency models of the fuel cell stack and fuel cell engine (FCE) are developed. Through experimental studies, we analyze the relationships between (1) the efficiency of the fuel cell stack and its current, (2) the efficiency of the fuel cell stack and its power, (3) the efficiency of the fuel cell stack and the hydrogen consumption ratio, (4) the efficiency of the FCE and the fuel cell stack current, (5) the efficiency of the FCE and its power, and (6) the efficiency of the FCE and the hydrogen consumption ratio. The factors which affect the efficiency of the fuel cell stack and that of the FCE are discussed. Finally, the efficiency models of the fuel cell stack and the FCE discussed in this paper are verified by test data. The results show that the simulation values fit well with the test data, and they can be applied in the fuel cell vehicle simulation studies.     

供气系统参数变化对双燃料发动机低负荷排放的影响

对空气和天然气供气系统的2个参数-进气温度和空燃比进行了发动机试验,空燃比的调节包括进气节流和停缸2种方式。试验结果表明,适当提高进气温度和合适的进气节流量都可以降低THC和CO排放,但NOx排放会增加,在低负荷时采用停缸技术,可以很好地改善发动机的排放。     

小功率航空活塞发动机重油技术进展

小功率航空活塞发动机是微型无人机系统的主要动力型式,单一燃料的重油使用是未来无人机动力系统发展的必然趋势。结合国内外无人机发展趋势和动力系统型式选择,分析了小功率航空重油活塞发动机的应用需求特点;根据航空燃料发展的单一化趋势,指出了小功率航空活塞发动机采用重油的发展趋势和面临的技术瓶颈;整理了现阶段国内外在小功率航空重油技术方面的不同创新思路和实现型式,分析评估了不同技术路线的应用特点和技术难度。     

氢燃料在汽车上的应用

本文作者结合自己在氢发动机方面的研究结果,分析了氢在汽车上应用时的特点,总结了汽车燃用氢时所存在的问题及解决方法。并介绍了目前世界各国在此方面的研究情况。     

基于高压共轨TBD620柴油机的两种不同喷嘴在低负荷性能下喷射特性和燃烧性能分析

利用hydsim软件,建立具有高压共轨燃油喷射系统的TBD620柴油机仿真模型,对其采用的两种喷油嘴在低负荷工况下的燃烧性能进行了仿真计算,分析研究实行高压共轨燃油喷射系统时两种喷油嘴对柴油机燃油喷射特性和燃烧性能的影响。结果表明采用高压共轨燃油喷射系统后标准喷油嘴在低负荷下仍具有良好的性能。     

Performance analysis of proton-exchange membrane fuel cell stacks used in Beijing urban-route buses trial project

Fuel cell hybrid vehicles' sustained development and commercialization are contingent on the reliability and durability of the fuel cell engines. In August 2008, official trial of the three proton-exchange membrane (PEM) fuel cell hybrid city buses commenced in a commercial-operation urban-route in Beijing for one year. In this paper, data from the performance analysis of the automotive fuel cells used in those city buses are presented and analyzed. The durability and reliability of the fuel cell engines under realistic conditions were evaluated by analyzing the standard deviation of the single-cell fuel cell voltages and by estimating the voltage vs. current characteristics obtained using the recursive least squares fitting method. After studying the degradation status by analyzing fitted results from the measured data, it is concluded that the fuel cell engines' performance meets the standard imposed by the driving conditions of the Beijing urban-routes, but that their performance degradation necessitates maintenance in order to ensure normal operation.     

直喷式LPG/柴油混合燃料压燃发动机的研究

基于液态LPG／柴油混合燃料在油泵前按一定比例混合和缸内直喷压燃的构想,开发了液态LPG／柴油比例混合电子控制系统。对该控制系统进行的一系列性能测试结果表明,它能根据发动机不同工况的需要,任意调节液态LPG／柴油的混合比,且调整精度较高。应用该系统,进行了直喷式LPC／柴油混合燃料压燃发动机的性能试验。试验结果表明：直喷式LPG／柴油混合燃料压燃发动机具有与柴油机相同的动力性与燃料经济性,而其烟度、NOx和HC排放均优于原柴油机。     

三孔喷油嘴柴油机燃烧系统的试验研究

摘要本文介绍一种三孔喷油嘴直喷式柴油机燃烧系统.试验证明,只要该系统的油束、燃烧室、缸内空气运动匹配合理,就可获得良好的经济性能指标.     

基于超声波雾化的发动机燃油供给系统设计

针对化油器式摩托车发动机油耗高、排放不好,电喷式价格贵等特点,笔者设计了一套基于超声波雾化的燃油供给系统代替化油器。新系统采用超声波雾化系统提供燃油,雾化后的燃油成微米级雾粒,增大燃油与空气接触混合的面积,使燃油混合更加均匀。实验结果显示,使用新系统发动机比原化油器式发动机尾气中HC、CO浓度明显降低,CO2增大,从而表明燃油燃烧更加充分,达到节能减排的效果,成本与化油器式相当。     

Dynamic modeling and simulation of hydrogen supply capacity from a metal hydride tank

The current study presents a modeling of a LaNi₅ metal hydride-based hydrogen storage tank to simulate and control the dynamic processes of hydrogen discharge from a metal hydride tank in various operating conditions. The metal hydride takes a partial volume in the tank and, therefore, hydrogen discharge through the exit of the tank was driven by two factors; one factor is compressibility of pressurized gaseous hydrogen in the tank, i.e. the pressure difference between the interior and the exit of the tank makes hydrogen released. The other factor is desorption of hydrogen from the metal hydride, which is subsequently released through the tank exit. The duration of a supposed full load supply is evaluated, which depends on the initial tank pressure, the circulation water temperature, and the metal hydride volume fraction in the tank. In the high pressure regime, the duration of full load supply is increased with increasing circulation water temperature while, in the low pressure regime where the initial amount of hydrogen absorbed in the metal hydride varies sensitively with the metal hydride temperature, the duration of full load supply is increased and then decreased with increasing circulation water temperature. PID control logic was implemented in the hydrogen supply system to simulate a representative scenario of hydrogen consumption demand for a fuel cell system. The demanded hydrogen consumption rate was controlled adequately by manipulating the discharge valve of the tank at a circulation water temperature not less than a certain limit, which is increased with an increase in the tank exit pressure.     

Some issues on performance analysis of fuel cells in thermodynamic point of view

In order to develop a new fuel cell and/or to enhance fuel cell performance, it is very important to understand clearly what the real performance of a fuel cell is. However, some important issues for the assessment of a fuel cell performance still require additional considerations. For example, the performance of a fuel cell is generally described based on an isothermal condition in spite of the non-uniform cell temperature distributions under real operating conditions. For this purpose, a formulation for the performance of a fuel cell operating at an isentropic condition (e.g., non-uniform cell temperature) is introduced in this study and compared with a reversible isothermal case (e.g., uniform cell temperature). Also, it is necessary to reveal the real difference in the performance of a fuel cell and a heat engine. Understanding of the purpose of the hybridization of a fuel cell with a heat engine is another important issue. In the present study, issues related to the performance of a fuel cell are considered from a thermodynamic point of view.     

Environmental sensor system for expanded capability of PEM fuel cell use in high air contaminant conditions

A novel device called the Environmental Sensor System has been designed and demonstrated to provide real time environmental air contaminant analysis and monitoring to allow fuel cell control systems to protect the integrity of the fuel cell from environmental contaminants. This is accomplished through continuous sampling of the ambient air used to provide oxygen to the fuel cell. Electrochemical sensors are used in this prototype device to monitor hydrogen sulfide, sulfur dioxide, nitric oxide, nitrogen dioxide and volatile organic compounds. The air is monitored before and after the air filter to allow for preventative maintenance and emergency protection. The integration of this ancillary device will allow fuel cell systems to safely and reliably operate in high air contaminant conditions which previously would have resulted in stack poisoning from air contaminants. Preliminary demonstration of this technology to protect the stack on a fuel cell electric bus is reported.     

直喷式柴油机燃油喷雾碰壁与空气卷吸模型的研究

本文提出了一个适合在准维模型中使用的直喷式柴油机喷雾碰壁与空气卷吸的数学模型。采用紊流射流理论推出了新的壁面射流计算公式,并在正确描述喷注贯穿的基础上建立了有涡流作用的空气卷吸模型。该研究结果用于准维模型的理论计算与实测结果吻合很好,证明了模型的实用性。     

Modeling and control of air stream and hydrogen flow with recirculation in a PEM fuel cell system—I. Control-oriented modeling

Transient behavior is one of the key requirements for the vehicular application of proton exchange membrane (PEM) fuel cell. The goal of this study is to develop a dynamic model of PEM fuel cell system (FCS) that is capable of characterizing the mixed effects of gas flow, pressure and humidity. In addition to the model of air supply system, the anode recirculation is also presented in this paper by an analytical model of injection pump. A steady-state, isothermal analytical fuel cell model is adopted to analyze the mass transfer in the diffusion layer and water transportation in the membrane. The liquid water accumulation in the cathode flow channel is described by a finite-rate phase-change model and the cathode flooding in the diffusion layer is also discussed. The transient phenomena in FCS are captured by the mechanical inertia of compressor and flow filling in lumped-parameter volumes of manifolds, anode and cathode.     

未来车用柴油机部分燃油喷射系统的试验研究

本介绍在一台单缸带增压中冷的试验机上，分别采用了具有高喷压力的直列泵喷射系统和电控泵喷嘴系统，对比两对柴油机经济性排放品质的影响，并对其试验结果做了分析。     

进气涡流比对直喷式柴油机油束碰壁过程影响的研究

本采用高速摄影技术，研究了小型直喷式柴油机缸内空气运动对油束碰壁过程的影响。研究结果表明，在小型直喷式柴油机中，燃油壁面喷射的反溅作用是燃油雾化过程中的重要阶段。油束在碰壁过程中，其锥角及贯穿速度均发生变化。不同的进气涡流强度，壁面油束的形状及其发展速度均不同，顺涡流方向壁面油束的扩展速度较快，随着涡流强度的增加，壁面油束只出现在顺涡流方向。空气涡流对燃油与空气混合的促进作用主要发生在油束与燃烧     

降低柴油机排气中氮氧化物含量的催化还原系统的研究

本文提出了一个带二次燃料喷射的NO2催化还原系统，并对其进行了模拟试验。试验中发现，用燃料作还原剂时，以Al3O3为载体的AgAlO2催化剂在NO2的还原反应中表现出较强的活性，是一种较理想的NO2还原反应催化剂。试验中还发现，随着喷入的燃料所产生的醛类的浓度的增加，NO2的转化效率不断增加。