WY125系列摩托车后减震器漏油问题的分析及改进

摩托车后减震器渗漏油问题,除受本身设计、部品结构及总成的耐久性能影响外,还受行驶道路、交通情况等因素影响。减震器中的关键零部件油封,其胶料、结构尺寸及相关部件的接触表面粗糙度和尺寸对漏油影响较大,而且过载使弹簧弯曲对油封单边磨损也会引起渗漏。     

Computing airfare elasticities or opening Pandora's box

Airfare elasticities are crucial for policy instruments for the stakeholders of tourism industry. Modellers attempting to estimate these elasticities face several challenges in the absence of microeconomic data on consumer preferences. The aim of this paper is to offer a critical analysis of the practice of computing airfare elasticities from tourism demand studies. It identifies and discusses potential sources of measurement errors in the data and drawbacks that investigators face and assesses their implications for the estimated parameters in the respective models. The use of price of crude oil and distance between origin and destination as proxies for transportation costs are evaluated. It is recommended that authors be more systematic in reporting their results. They need to comment on the limitations of their elasticity estimates since these have repercussions on policy recommendations made based on their results.     

Modeling gas dissolution in deepwater oil/gas spills

Gases in deepwater oil/gas spills can lose considerable amounts of the gas phase due to dissolution in water. Gas dissolution has a significant impact on the behavior of the oil/gas jet/plume because of its impact on the buoyancy. A method is presented in this paper for computing gas dissolution that covers a broad range of water depth, from shallow water where gases behave as ideal ones under low pressure to deepwater where gases behave as non-ideal ones under high pressures. The method presented also accounts for the spherical and non-spherical shapes of gas bubbles. The gas dissolution computations are validated by comparing the computed results with observed data from previously conducted laboratory experiments. The gas dissolution computation module is then integrated with a model for underwater oil/gas jets/plumes by Yapa and Zheng [J. Hydraul. Res. 35 (5) (1997) 673]. Scenario simulations are presented to show the impacts of gas dissolution on the behavior of jets/plumes. These scenarios show the impact of dissolution on the behavior of the jet/plume. The comparison of results using ideal gas conditions and non-ideal gas conditions is also shown.     

船舶结构疲劳强度分析中的几个问题

讨论了有关确定船舶结构疲劳寿命的几个重要因素;应为周期数、Ｗｅｉｂｕｌｌ分布形状参数ξ与船长关系、热点应力和切口应力等。以２５８,０００ｔ现有超大型油船（ＶＬＣＣ）的舷侧纵骨和甲板纵骨的疲劳强度为例进行了计算,计算结果表明预示的疲劳寿命较好反映了超大型油轮的疲劳寿命。     

离心泵内二维流场的数值模拟

在AutoCAD中建立二维离心泵的几何模型,将模型转入GAMBIT进行网格划分,再利用Fluent数值模拟此离心泵内的二维流动。计算模拟结果显示出离心泵内的速度场、压力场和湍流强度等。采用标准的k-ε模型模拟得到的结果可真实反映离心泵内部的复杂流动,为离心泵的设计改良提供了可靠依据。     

一种新型摩托车发动机副轴油封

在摩托车发动机中,用于密封的副轴油封具有较高的弹性,泄漏率低,耐热、耐压范围广,能起到防尘、防油外漏的作用.但是,当副轴表面质量较差或发动机工作一段时间后,机油质量下降,机油中的异物及未清除的铝屑等杂质易将主唇口划伤,从而影响密封性能,出现渗油现象.笔者设计的在油封主唇外斜面上加倾斜凸筋的副轴油封,可有效防止因主唇口划伤而引起的渗油现象.     

AC-13(改进型)沥青混合料劈裂试验研究

文章结合柳州绕城高速公路AC-13(改进型)沥青混合料矿料级配,利用SGC旋转压实机成型沥青混合料试件并进行劈裂试验,对AC-13(改进型)沥青混合料的间接抗拉强度进行评价,得出沥青混合料的空隙率、油石比、老化这些指标的变化与沥青混合料的力学特性间的密切关系。     

Dispersion of spilled oil by a cavitating jet at sea

This article presents the possibility of using a high-speed water jet for the dispersion of spilled oil at sea. Laboratory experiments showed that a high-speed water jet is very effective in dispersing heavy oil. Two methods were examined and compared using freshwater. The first method was to disperse an oil layer on the water surface using a cavitating jet ejected upward at an angle of 45°. A target plate was placed at the interface of the water and oil layer to enhance the collapse of cavitating bubbles. The second method was to eject a high-speed water jet vertically downward from the air. A guide plate with a guide hole was placed under the oil layer with no target plate as such. The second method showed an improved dispersion ability and thus its effectiveness was examined using an oil layer on seawater. The dispersion of oil was better in seawater than in freshwater, probably because seawater contains natural surfactants.     

双底双壳油轮中横剖面结构优化设计专家系统

本文利用船舶中横剖面设计专家系统外壳[1]，结合专家经验、领域第一原理以及基于数据离散的优化方法，在补充了具体专业知识以后获得了双底双壳油轮中横剖面结构设计专家系统。该系统能够模仿专家的设计过程进行设计，这对于保存和利用专家知识、优化设计结果都有直接意义。     

浅析油品运输中"转换装油"引起的安全问题

从一起油轮爆炸事故，分析了事故的起因主要是由于“转换装油”引发的。后经随机调查发现，现阶段油轮“转换装油”现象非常突出。针对此现象，客观分析了油轮“转换装油”危害性及引发事故的原因，并提出了有效的防范措施，呼吁广大从业人员一定要加强防范意识。