往复式低温制冷机的气体润滑

对低温机械应用气体润滑技术的情况进行了综述及讨论,重点针对往复式低温机械活塞密封的气体润滑,分析了低温活塞膨胀机气体润滑活塞密封的结构特点、性能及使用,介绍了低温制冷机迷宫密封的应用概况,反映了微型制冷机中最新研发气体轴承活塞的结构特点及动态.     

润滑油对R134a冰箱压缩机性能的影响

分析了润滑油粘度对冰箱压缩机功率消耗的影响,探讨了冰箱压缩机活塞与气缸间隙对其润滑与密封的影响。通过试验证明,在合理的活塞与气缸间隙下,将通常所用的润滑油改为更低粘度的润滑油,不仅可以显著提高冰箱压缩机的性能指标,而且满足可靠性的要求。     

电液锤活塞密封窜漏的原因分析及改进

电液锤液气缸活塞密封采用由PTFE制造的格莱圈密封，在使用中液压油会窜入气腔，导致气体压力升高。分析了发生窜漏的两种原因：流过密封环的液膜在气腔积聚和收锤造成的压力冲击使得缸体膨胀，密封失效，并提出了在格莱圈后安装Yx圈的改进措施。     

超高压活塞压缩机的液封性能分析

基于层流运动的N-S方程,建立了密封液在活塞和气缸间隙内的流体模型,并对其流场进行计算分析,推导出注油压力、耗油量等参数;通过对计算结果、液压密封重要参数与压缩机结构参数之间的关系分析,提出了超高压活塞压缩机的液压密封机构设计的方法。     

气浮式无摩擦气缸设计

简述了无摩擦气缸的定义与应用,根据圆柱活塞间隙密封与带径向两排节流小孔圆柱活塞的密封模型,指出了影响其内泄漏量的主要参数。结合理论分析与经验,设计了一种新型无摩擦气缸及其带径向节流孔与轴向密封槽的气浮活塞,应用计算机仿真技术分析了活塞与缸壁间隙处的气流压力与流速分布,研究表明活塞上密封槽具有提高密封与支撑作用。另外为获取无摩擦气缸的摩擦性能,研究了两种测试方法与装置,根据实验可得活塞表面带密封槽与节流小孔的气浮式气缸活塞向上运动时摩擦力极小,实现了气悬浮。     

电液锤活塞密封窜漏的原因分析及改进

电液锤液气缸活塞密封采用由PTFE制造的格莱圈密封,在使用中液压油会窜入气腔,导致气体压力升高。本文分析了由于缸体膨胀、密封失效而发生窜漏的两种原因,即液膜流过密封环时在气腔积聚和收锤造成的压力冲击。并提出了在格莱圈后安装Yx圈的改进措施。     

热固耦合形变对BOG压缩机迷宫密封间隙的影响

大型BOG往复压缩机的压缩介质温度很低,气缸和活塞体在工作中承受着较大的应力载荷和温度负荷,变量对密封间隙的影响。结果表明:在热固耦合作用下,活塞和气缸两者变形量最大值均发生在活塞向上压缩的行程末端,其中,气缸变形量最大发生在缸体顶沿位置,活塞最大变形发生在活塞顶部端面中间环形部位。模拟分析表明,活塞与气缸产生的变形可使该大型BOG往复式压缩机压缩过程中密檿檿檿檿檿檿檿对活塞与气缸的间隙产生显著影响,并间接影响迷宫密封性能。为研究热固耦合形变对迷宫密封的影响,以某大型BOG往复式压缩机为例,以ANSYS Workbench为仿真平台,采用热固耦合方法对气缸和活塞进行仿真分析,得到气缸与活塞在热固耦合作用下的形变规律,确定其形封间隙增加0. 1～0. 15 mm的变形量。     

双作用斯特林热机活塞密封流阻特性数值计算

考虑活塞前部环形间隙的影响,建立斯特林发动机活塞密封结构的流阻模型,分别展开动、静态下数值计算,得到活塞各密封段内压力与流量的关系,分析工质随结构参数变化的流动特性。结果表明：动、静态下活塞密封处流阻呈现不同特点,动态时流阻随流量增加而增大,静态时流阻为一恒定值;活塞环泄漏面积对流阻的影响较大,可以通过使用组合式活塞环以增大流阻而减小泄漏;而前部间隙宽度对流阻的影响较小,适当加大间隙宽度能在不影响密封的前提下减小活塞与气缸的摩擦。     

全液压电液锤锤杆活塞结构及密封研究

介绍了全液压电液锤锤杆活塞结构及密封的关键技术,讨论了全液压锻锤锤杆活塞结构及密封如何设计和选择,及大吨位全液压锻锤锤杆活塞和密封在生产中出现的新问题和解决方法,指出全液压锻锤的发展是一个不断提高和完善的过程.     

不同工况下活塞二阶运动和活塞裙部润滑研究

目前研究内燃机活塞二阶运动和活塞裙-缸套摩擦副润滑时一般仅针对标定工况进行,不考虑实际使用内燃机工作中工况的不断变化。另外,分析中一般都假设活塞裙-缸套摩擦副在一个内燃机工作循环中处于充分润滑状况。以某四行程内燃机为研究对象,基于实测的气缸压力,考虑实际润滑油流动确定摩擦副的润滑状况,进行不同内燃机工况下的活塞二阶运动和活塞裙-缸套摩擦副润滑分析。结果表明,不同工况下的活塞二阶运动性能和活塞裙-缸套摩擦副润滑性能都存在差异,活塞二阶运动性能和活塞裙-缸套摩擦副润滑性能的最不利情况不一定出现在标定工况。因此,内燃机活塞组件设计时,如果仅分析标定工况下的活塞二阶运动和活塞裙-缸套摩擦副润滑性能将不够全面合理,需要进行不同工况下活塞二阶运动和活塞裙-缸套摩擦副润滑性能的分析计算。     

基于FLUENT的两种管道内流体分析

径向柱塞泵具有工作压力大、效率高、维修方便等优点,越来越受到市场的欢迎.四缸径向柱塞式往复泵,采用单拐偶缸径向对称专利技术设计.为了验证接在柱塞泵外部的两种管道分布的合理性,分析了四缸柱塞泵出口管道的两种布局方式,应用FLUENT软件进行建模,然后对模型划分网格和仿真分析,因为速度为非定常流量,所以在VC中进行了速度的...     

Dynamic behavior analysis of reciprocating compressor with subsidence fault considering flexible piston rod

Subsidence wear is inevitable in a reciprocating compressor system, but how to induce body vibration is not clear. We investigated the dynamic behavior of a reciprocating compressor system with subsidence fault considering a flexible piston rod. The flexible piston rod was modeled as a cantilever beam. The dynamic model, in which the influence of the subsidence size, variational cylinder pressure, impact effects and piston rod flexibility are taken into account, was established. Influences of the four parameters including subsidence size, vertical force of flexible piston rod, cylinder pressure and crankshaft speed were analyzed in the dynamic response. Numerical results reveal that with the change of the four parameters, the existence of subsidence fault has a significant effect on the displacement, velocity and acceleration of the crosshead in the transverse direction, but only conspicuously affects the acceleration in the longitudinal direction. In addition to cylinder pressure, the larger the values of the other three parameters, the greater the influences. The cylinder pressure is a time-varying working load. Not only the cylinder pressure but also the open/close time of the valves and change rate of the pressure all affect the dynamic behavior of the system with subsidence. Meanwhile, the change in the vertical force of the flexible piston rod has a remarkable effect on the jump position of the crosshead, but the effect of other parameters is not obvious. In addition, the changes of parameters produce obvious influences on the impact force and the impact range of the crosshead. The stability of the reciprocating compressor system was studied using Poincaré portraits method. The result shows that the system with subsidence fault has chaotic behavior.     

转速对EHA泵柱塞副柱塞位姿及泄漏量影响仿真分析

斜轴式轴向柱塞泵作为电动静液压作动器（Electro-hydrostatic actuator,EHA）液压系统的重要元件,高转速、高工作压力是实现其小型化、轻量化的重要手段。柱塞副是斜轴式轴向柱塞泵中重要的两对摩擦副之一,对斜轴式轴向柱塞泵的工作状况起着直接影响。随着缸体转动,柱塞在缸体柱塞孔中的位姿朝着各个方向不断变化,柱塞副泄漏量也随之变化。为准确得到高速高压下柱塞副的泄漏量并给出解释,充分考虑柱塞受力情况,通过对离散化的柱塞副油膜雷诺方程和力平衡方程进行迭代求解,使用柱塞端面偏移量来确切描述了柱塞在缸体柱塞孔中的位姿随转速的变化情况,据此给出了柱塞副泄漏量模型,分析了转速变化对柱塞位姿和柱塞副泄漏量的变化的影响。结论为EHA泵的设计提供了适当的理论指导。     

表面形貌对活塞环密封及摩擦性能的影响

综合考虑活塞环表面形貌、弹性变形、运动面型线影响,建立柴油机活塞环-缸套摩擦副的弹性流体动压润滑计算模型,分析活塞环表面纹理方向及粗糙度大小对活塞环窜气及摩擦功耗的影响。研究发现,随着转速的提升,活塞的窜气量及摩擦功耗会加剧,导致发动机效率降低;活塞环-缸套摩擦副的表面纹理方向影响窜气量和摩擦功耗,采用活塞环横向纹理和缸套纵向纹理配合时,对活塞环窜气量及摩擦功耗的改善效果较好;活塞环和缸套的表面粗糙度对密封和润滑特性有较大影响,当缸套表面粗糙度增大时,窜气量先减小后增大,摩擦功耗先增大后减小,而在一定范围内,当活塞环表面粗糙度增大时,窜气量和摩擦功耗都减小。     

活塞偏心倾斜对双筒液压减振器动态阻尼特性影响分析*

考虑活塞偏心和倾斜后活塞与缸筒之间的摩擦与润滑因素,研究充气式双筒液压减振器动态阻尼特性;建立活塞偏心和倾斜的双筒式液压减振器的动态阻尼特性数学模型和动压润滑方程,求解减振器动态阻尼特性数学方程;采用雷诺空化边界条件,对Reynolds方程采用五点差分法进行离散,利用超松弛迭代法(SOR)迭代求解,得到摩擦阻尼力;分析活塞偏心距比、活塞倾斜角度,活塞倾斜时活塞运动速度、活塞半径、活塞宽度等因素对摩擦阻尼的影响,以及各摩擦因素对减振器动态阻尼特性的影响。结果表明:活塞偏心和倾斜时,随活塞速度、偏心距比、活塞倾斜角度、活塞宽度等的增加,减振器活塞与缸筒之间的油膜摩擦力均增加,而随活塞半径的增加,油膜摩擦力减小。减振器活塞发生倾斜时,会造成阻尼力的大幅增加,严重影响车辆行驶的舒适性能,且活塞速度越快,对舒适性影响越严重。     

A study of thermal and lubrication phenomena in the piston‐ring and cylinder‐sleeve tribosystem of an internal combustion engine and flash temperature calculation

The piston ring is one of the main elements in an internal combustion engine. Together with the cylinder sleeve, the piston ring has two basic functions: (1) contacting the cylinder sleeve to prevent the gases formed above the piston from migrating to the crankcase and (2) as a translation couple, formed of the piston‐ring and cylinder‐sleeve assembly. Complex tribological phenomena occur in the piston‐ring and cylinder‐sleeve tribosystem, according to variations in sliding speed, gas pressure, and temperature. This paper presents a method of calculation of the thickness of the lubricant film in the piston‐ring and cylinder‐sleeve tribosystem, using the Reynolds equation, integrated in specific conditions. According to the Newtonian behaviour of the lubricant, the shear stresses in the lubricant film between the piston ring and cylinder sleeve are determined. A computational procedure to determine flash temperatures in the piston‐ring and cylinder‐sleeve tribosystem is presented. The theoretical results, including film thickness, sliding speed, gas pressure, and flash temperatures for a complete crankshaft cycle are also presented.     

A study on effects of recirculated exhaust gas upon wear of cylinder liner and piston in diesel engines

The effects of recirculated exhaust gas on the wear of cylinder liner and piston were experimentally investigated by a two-cylinder, four cycle, indirect injection diesel engine operating at 75% load and 1600 rpm. For the purpose of comparison between the wear rates of the two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot in exhaust emissions was removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors (A water injector has 144 nozzles of mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out with the fuel injection timing fixed at 15.3° BTDC. It was found that the mean wear rate of cylinder liner with EGR was greater in the measurement positions of the second half than those of the first half, that the mean wear rate without EGR was almost uniform regardless of measurement positions, and that the wear rate of piston skirt with EGR increased a little bit, but the piston head diameter increased, rather than decreased, owing to soot adhesion and erosion wear, and especially larger with EGR.     

The Friction Reducing Properties of Molybdenum Dialkyldithiocarbamate Additives: Part II - Durability of Friction Reducing Capability

Material characterization and wear evaluation of the original and replacement pistons and cylinder liners from a Tiger 131 are reported. The original piston and cylinder liner were operative in the Tiger engine during WWII. The replacement piston and cylinder liner were used as substitutes and were obtained after failure in 2 h of operation in the actual engine. Material characterization revealed that the original piston was aluminum silicon hypereutectic alloy approximately matching the specification of RSA-419 AE, with a silicon content of 19.92 wt%. The replacement piston was aluminum copper alloy with a low silicon content of 0.73 wt%, approximately satisfying specifications of Al 2031 and Al 2618-T6. Scuffing, material removal, and ploughing were observed in the replacement piston and cylinder liner. These failures were attributed to inadequate piston material and design. The replacement piston average surface roughness was 9.09 μm and for the replacement cylinder liner it was 5.78 μm. Characterization results showed that both the original and replacement cylinder liners consisted of mostly iron, which is indicative of cast iron, a common material for this application.     

基于斜盘式轴向柱塞泵结构优化的应用研究

针对应用于工程机械上某型号斜盘式轴向柱塞泵滑靴与柱塞组件及缸体试验出现局部严重磨损及干涉故障,从滑靴与柱塞组件及缸体的力平衡关系、滑靴与柱塞组件工艺与结构以及缸体配合间隙三个方面进行失效分析,在保证柱塞泵容积效率的前提下,提出以下改进措施：优化设计了滑靴内外辅助支撑面与中心通油孔的固定节流器结构、利用回程盘与滑靴联动配合理论进行结构优化尝试对比应用薄壁空心柱塞,将这些措施运用于产品批量制造,取得较好效果。为斜盘式轴向柱塞泵的结构优化、提高效率和性能方面提供实用经验,具有一定的综合效益和推广价值。     

柴油机缸套内径和活塞外径测量装置的研制

采用电涡流位移传感器和工控机数据采集系统研制了缸套内径和活塞外径测量装置。并钭检测结果输入计算机，由专用的活塞－缸套优化选配软件进行处理，从而得到活塞－缸套最优匹配结果。