活塞环加工凸轮仿形失真问题的研究

本文从偏形原理分析入手,提出了活塞环仿形凸轮参数计算中应予以重视的“包络问题”,同时为解决这一问题提出了计算方法。     

含钼水基切削液在活塞环内外仿加工中的应用

本文介绍了一种用于活塞环内外仿加工切削液--水溶钼（TM-04）添加剂,对活塞环内外仿形工序在加工过程中起到了抗磨减摩作用,可节约内外仿加工用成型刀具,同时提高活塞环外圆加工光洁度,延长切削液的使用寿命和换水周期,现已经用于正常生产。     

浅论活塞环立式内外圆仿形加工车床

仿形车加工是活塞环机械加工的关键工序,其加工质量对活塞环的性能有着重要影响。立式内外圆仿形车床,起初由瑞士DIMACO公司研发,该设备是集活塞环内外圆同时仿形加工、开口于一体的组合机床。其仿形凸轮进行了系列化处理,创新设计了框式滑架车头,机床加工产品质量稳定,精度好,效率高。虽然其性能优异,但因价格昂贵,国内仅有两家活塞环企业引进了3台。近年来,国内一些设备制造厂也自主研发了活塞环立式内外圆仿形车床,并日趋成熟,将会有越来越多的活塞环生产企业采用。     

活塞环内外圆数控仿形立式车床的设计

本文介绍一种活塞环内外圆数控立式车床的硬件和软件设计，其基本原理是运用活塞环自由形线数据处理程序对活塞环数据进行处理，生成活塞环自由形线数据文件和伺服电机位置控制文件进行活塞环加工，主轴和数控仿形刀架均为伺服电机驱动，采用电子凸轮控制模式，控制刀具的径向进给运动与主轴转角位的伺服关系，活塞环叠内外圆同时加工。     

活塞环理论压力的加工再现误差探讨

本文就活塞环型线的加工，进行了理论方面的探讨，对近似椭圆理论的运用进行了阐述，并对内外圆仿形技术进行了推导，旨在强调未来内外圆仿形技术在活塞环加工过程中的重要性。     

活塞环工艺设计软件的开发

本文就活塞环工艺软件的编制思路进行了阐述,并对工艺软件编制进行的技术处理及软件操作作了简要的说明。     

活塞环数控车床控制系统设计

针对活塞环自由型线的加工特点,介绍了笔者研制的新型活塞环全数控加工设备的控制系统工作原理和结构方案。     

活塞环内外圆表面残余拉应力浅析

本文介绍了活塞环内外圆表面残余拉应力产生的原因，以及其对活塞环径向压力分布的影响。     

椭圆筒体活塞环仿形车割机床研制

由我公司研制并获得国家实用新型专利(专利号87213091.6)的《椭圆筒体活塞环仿形车割机床》已由我公司与江苏环洋组合机床厂合作开发成功,并投入小批量生产.这为我国活塞环行业提供了一种加工性能优良的椭圆筒体活塞环的关键设备.愿它为行业的发展能起到应有的作用.椭圆筒体活塞环以它独具的特点,在我国活塞环生产行业中诞生,它是一种在国内处于领先地位的、很有发展前途的新产品、它既保留了筒体铸造弹性模量高,机械性能好,金相组织易于控制,弹力保持率高,硬度适中,对缸壁的磨损小,寿命长,铸造废品率低,成本低,能适应     

天然气发动机活塞环的设计与开发

针对天然气发动机的特点及目前存在的问题,提出了天然气发动机活塞环在材料、结构、表面处理、参数选择等方面的设计理念,并成功应用到生产实际中.     

基于NX的凸轮曲线设计及两种凸轮机构参数转换

凸轮机构是一种由凸轮、从动件和机架组成的传动机构,常用于机械设备中,可以获得较复杂的运动规律。在发动机的结构中,凸轮机构是配气系统的重要组成部分,凸轮轮廓曲面的形状及其加工精度直接影响到进、排气的流量变化。本文主要讲述应用NX进行凸轮轮廓曲线的设计及通过运动仿真分析不同凸轮机构参数转换的方法,为凸轮轴车铣复合加工中心及数控凸轮轴磨床凸轮外形加工提供重要技术依据。     

Thermodynamic analysis of direct internal reforming of methane and butane in proton and oxygen conducting fuel cells

We present results of a thermodynamic analysis of direct internal reforming fuel cells, based on either a proton conducting fuel cell (FC-H⁺) or an oxygen ion conducting fuel cell (FC-O²⁻). We analyze the option of methane as fuel as well as butane. The model self-consistently combines all chemical equilibria in both the anode and cathode compartments with the proton or oxygen transfer rates through the membrane without predefining fuel utilization.     

内燃机活塞拍击表面振动与燃烧噪声的关系

通过测量噪声和表面振动信号，用时间窗获取的噪声信号主要为活塞拍击噪声和燃烧噪声，并对表面振动信号进行频谱分析和时频分析，确定该噪声信号中活塞拍击噪声可能出现的频率范围和对整个噪声分析频率带能量的贡献，不加区别地把燃烧噪声和活塞拍击噪声看作是燃烧噪声进行燃烧噪声机理研究的方法是不可取的。     

Numerical modeling of manifold design and flow uniformity analysis of an external manifold solid oxide fuel cell stack

Computational fluid dynamics (CFD) technique and experimental measurement are combined to investigate the effects of several geometric parameters on flow uniformity and pressure distribution in an external manifold solid oxide fuel cell (SOFC) stack. The model of numerical simulation is composed of channels, tubes and manifolds based on a realistic 20-cell stack. Analysis results show that gas resistance in the channel can improve the flow uniformity. However, channel resistance only has a limited effect under high mass flow rate. With the increase of inlet tube diameter, the flow uniformity improves gradually but this has little impact on pressure drop. On contrary, the larger diameter of outlet tube reduces the pressure drop effectively with minor improvement on flow uniformity. The dimensions of the flared inlet tube and the round perforated sheet in the manifold are designed to optimize both flow uniformity and pressure drop. Practical experimental stack is established and the velocity in the outlet of the channel is measured. The trends of the experimental measurements are corresponding well with the numerical results. The investigation emphasizes the importance of geometric parameters to gas flow and provides optimized strategies for external manifold SOFC stack.     

Design and analysis of SOFC stack with different types of external manifolds

In this study, a four-cell stack of anode-supported planar solid oxide fuel cells (SOFCs) was designed and simulated to investigate the flow/heat transport phenomena and the performance of the SOFC stack. This SOFC stack was designed based on the external manifold types with one side open toward the cathode inlet and components such as base station, manifold, end plate, press jig, and housing. To investigate the performance of the SOFC stack, a step-by-step heat and flow analysis was conducted. First, the separator, functioning as a current collector and a gas channel, was designed to have repeated convex shapes. As the boundary of the flow passage was periodic in both streamwise and transverse directions, only a small part of the flow channel was simulated. In the case of simple homogeneous porous media, the computational results for flow resistance could be expressed by following Darcy's Law. Subsequently, these calculation results from the separator flow analysis were used in the housing and stack analysis. Second, the flow of the cathode region in the housing of SOFC stack was analyzed to verify the flow uniformity in the cathode channel of the separators. Finally, a stack analysis was executed using the electrochemical reaction model to investigate the performance and transport phenomena of the stack. Owing to the uniformity in flow and temperature, each SOFC cell exhibited similar contours of reactant gases, temperature, and current density. In the case of two different fuel utilizations with different flow rates, the low fuel utilization performed slightly better than the high fuel utilization.     

On the physical differences between tensile testing of type 304 and 316 austenitic stainless steels with internal hydrogen and in external hydrogen

Seventeen metastable austenitic stainless steels (type 304 and 316 alloys) were tested in tension both with internal hydrogen and in external hydrogen. Hydrogen-assisted fracture in both environments is a competition between hydrogen-affected ductile overload and hydrogen-assisted crack propagation. In general, hydrogen localizes the fracture process, which results in crack propagation of particularly susceptible materials at an apparent engineering stress that is less than the tensile strength of the material. Hydrogen-assisted crack propagation in this class of alloys becomes more prevalent at lower nickel content and lower temperature. In addition, for the tests in this study, external hydrogen reduces tensile ductility more than internal hydrogen. External hydrogen promotes crack initiation and propagation at the surface, while with internal hydrogen surface cracking is largely absent, thus preempting hydrogen-assisted crack propagation from the surface. This is not a general result, however, because the reduction of ductility with internal and external hydrogen depends on the specifics of the testing conditions that are compared (e.g., hydrogen gas pressure); in addition, internal hydrogen can promote the formation of internal cracks, which can propagate similar to surface cracks.     

Sustainability analysis of the Ahuachapán geothermal field: management and modeling

The Ahuachapán geothermal field (AGF) is located in north western El Salvador. To date, 53 wells (20 producers and 8 injectors) have been drilled in the Ahuachapán geothermal field and the adjacent Chipilapa area. Over the past 33 years, 550 Mtonnes have been extracted from the reservoir, and the reservoir pressure has declined by more than 15 bars. By 1985, the large pressure drawdown due to over-exploitation of the resource reduced the power generation capacity to only 45 MW_e. Several activities were carried out in the period 1997–2005 as part of “stabilization” and “optimization” projects to increase the electric energy generation to 85 MW_e, with a total mass extraction of 850 kg/s.     

面对日益严峻的能源及环境问题论内燃机的发展方向

本文简述了内燃机的发展史及其在国民经济中的重要作用,分析了内燃机的广泛应用对石油资源、环境污染的影响及其发展方向。     

结构参数对活塞环-缸套系统润滑的影响

以某型号直列式6缸机为载体,用数值方法求解活塞环．缸套三维润滑模型,分析了表面粗糙度、活塞环桶面高度和缸套椭圆度等结构参数对润滑状态的影响,给出了不同参数下最小油‘膜厚度的对比,以及几个曲轴转角下油膜压力和油膜厚度的分布情况。结果表明,结构参数对润滑有显著的影响;在做功冲程上止点附近油膜厚度最小,其值为0．559μm,油膜压力最大;在整个运行过程中,凸峰接触主要出现在做功冲程上止点附近。     

Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on performance and emissions of internal combustion engines

Energy security is an important consideration for development of future transport fuels. Among the all gaseous fuels hydrogen or hydroxy (HHO) gas is considered to be one of the clean alternative fuels. Hydrogen is very flammable gas and storing and transporting of hydrogen gas safely is very difficult. Today, vehicles using pure hydrogen as fuel require stations with compressed or liquefied hydrogen stocks at high pressures from hydrogen production centres established with large investments.Different electrode design and different electrolytes have been tested to find the best electrode design and electrolyte for higher amount of HHO production using same electric energy. HHO is used as an additional fuel without storage tanks in the four strokes, 4-cylinder compression ignition engine and two-stroke, one-cylinder spark ignition engine without any structural changes. Later, previously developed commercially available dry cell HHO reactor used as a fuel additive to neat diesel fuel and biodiesel fuel mixtures. HHO gas is used to hydrogenate the compressed natural gas (CNG) and different amounts of HHO-CNG fuel mixtures are used in a pilot injection CI engine. Pure diesel fuel and diesel fuel + biodiesel mixtures with different volumetric flow rates are also used as pilot injection fuel in the test engine. The effects of HHO enrichment on engine performance and emissions in compression-ignition and spark-ignition engines have been examined in detail. It is found from the experiments that plate type reactor with NaOH produced more HHO gas with the same amount of catalyst and electric energy. All experimental results from Gasoline and Diesel Engines show that performance and exhaust emission values have improved with hydroxy gas addition to the fossil fuels except NO_x exhaust emissions. The maximum average improvements in terms of performance and emissions of the gasoline and the diesel engine are both graphically and numerically expressed in results and discussions. The maximum average improvements obtained for brake power, brake torque and BSFC values of the gasoline engine were 27%, 32.4% and 16.3%, respectively. Furthermore, maximum improvements in performance data obtained with the use of HHO enriched biodiesel fuel mixture in diesel engine were 8.31% for brake power, 7.1% for brake torque and 10% for BSFC.