无润滑活塞氧压机气缸的封存

无润滑活塞氧压机是中小型空分设备中主要的机组之一。制造厂在产品出厂前,经试运转合格后,都要解体清洗,进行油封、包装,然后发往用户。大型无润滑活塞氧压机大多采用按部件解体,油封后分箱单独包装。而中小型无润滑活塞氧压机则采用部分解体的方法,将活塞、气阀、填料密封器单独油封包装,气缸与机身、传动部件组装在一起进行油封包装。     

基于Fluent的无摩擦气缸活塞结构设计仿真

针对现有气缸-活塞结构径向承载力低、耗气量大以及工作失稳等问题,结合空气轴承的设计思路,提出了一种新颖的无摩擦气缸活塞的设计方法.利用流体仿真软件Fluent,建立了无摩擦气缸活塞的流体模型,并得到了气膜沿活塞轴向的压力分布情况;同时,采用传统理论计算与Fluent仿真计算进行了对比研究,得到了活塞偏心率与径向承载力的关系.研究结果表明,传统理论计算与Fluent仿真计算结果基本吻合,后者在偏心率处于(0.1～0.3)范围内时,承载力计算误差低于3.2％;并且偏心率越小,仿真计算误差越小,说明利用Fluent对气缸活塞结构设计具有正确性以及可靠性.     

关于无曲轴发动机结构的设想

提出了一种无曲轴发动机的新型结构的设计,利用四连杆机构与齿轮机构将气缸的往复运动转化为圆周运动,然后进行输出,而且在工作过程中,利用四连杆机构与齿轮机构的配合,可以实现转矩的增大,利用adams对系统进行了运动学仿真,仿真结果表明,系统能够实现平稳运行.     

新颖的无杆双作用气缸

无杆双作用气缸具有结构紧凑,所占空间小等优点。所以,目前已应用在传送机构上。下面将无杆双作用气缸的结构以及设计制造中的几个主要问题说明如下。一、气缸的结构和特点无杆双作用气缸在长度方向上,它所占的空间尺寸仅为普通型有杆气缸的二分之一。其结构如图1所示。其主要特点如下。1.气缸的活塞是装配式的结构。它有一个径向伸出部份。该部份与负载相连接。2.气缸缸体7全长上有一个轴向通槽。活塞的伸出部份就是通过该槽伸到缸体外面。     

无活塞杆气缸

介绍曲轭式、磁铁式和钢索式三类无活塞杆气缸的工作原理、特点及应用要点。     

航空活塞发动机气缸磨合的建议

主要介绍航空活塞发动机磨合中胀圈和气缸壁的工作机理和作用,分析磨合中的重要环节和不利因素,提出发动机磨合过程的注意事项和要求,从发动机的磨合原理、磨合过程以及如何进行磨合三个方面进行介绍,强调磨合过程对发动机的品质和使用寿命的直接影响.     

磁性无活塞杆气缸介绍

简要介绍磁性无活塞杆气缸结构、优点、磁保持力的计算、关键零件的选择及其应用。     

气缸座精镗曲轴孔组合刀具的设计

介绍了精镗曲轴孔组合刀具的设计与计算,该组合刀具将制冷压缩机气缸座生产加工中的精镗曲轴孔、刮削轴肩台面和倒角三道工序在同把刀体上一次性加工出来,既提高了生产效率,又保证了产品质量,取得了良好的经济效果。     

用有限元法分析曲轴过渡圆弧的磨削加工

一、前言曲轴是动力机上一个关键零件，其结构往往是多招面又复杂、刚性差，但在工作中却要承受很大的转矩和交变弯曲应力。因此容易产生扭振，疲劳断裂及轴径磨损。连杆轴须是曲轴要害部位，它直接承受连杆传来的巨大冲击力，特别是连杆轴须两侧的过渡圆弧与曲轴的疲劳寿命息息相关。这是因为在磨削加工过渡圆弧时，此处散热条件差，磨创高温将留下残余应力，而在工作时，随着连杆轴颈绕主轴顿转动，其受力的大小，方向都在周期性的变化，曲轴受到交变力的作用下，在过渡圆弧处产生较大的应力集中区，严重时甚至发生断裂现象。因此，合理选…     

气缸中心线与曲轴回转中心线不共面结构的设计

在气缸中心线和曲轴回转中心线之间设置偏心距,在惯性力公式中用(α-β_0)代替α,回转角同惯性力之间关系得到改变,采用此结构后,侧压力、倾复力距、轴功率将相应减小,从而减小基础振动。     

无杆活塞气压缸驱动的二次正交铰杆增力压力机

介绍了无杆活塞式气压缸驱动的的二次正交铰杆增力压力机,给出了具体的工作原理和压头输出力计算公式.在某些场合下,基于气动一机械复合传动的二次铰杆增力压力机可取代容易产生空气及地面污染的液压压力机.在此基础上提出了两点浮动压力机,具体分析了相对于单点输出压力机的不同之处.     

基于对称双曲柄活塞驱动的空压机

由曲柄连杆机构驱动的普通活塞式空压机存在噪声、振动和缸体磨损等问题,提出双曲柄连杆机构驱动的活塞式空压机来解决这些问题;同时设计了基于对称双曲柄活塞驱动的二次增压双作用空压机和双级双作用空压机,提高了空压机的输出压力和流量,并可实现低压大流量和高压小流量的输出控制;降低空压机的振动和噪声,提高平稳性,降低活塞和气缸缸体的磨损,提高空压机的使用寿命。     

曲轴偏置对汽油机活塞摩擦力的影响

本文分析了曲轴偏置在不同的发动机工况下对活塞摩擦力的影响,并用浮动缸套方法分析了活塞裙部与缸套间的活塞摩擦力,具有一定的指导意义。     

发动机活塞捣缸故障的诊断分析

从缸套与缸体的配合精度、散热冷却、活塞组与缸套的装配 ,分析了活塞捣缸故障发生的原因     

Analysis of oil consumption in cylinder of diesel engine for optimization of piston rings

The performance and particulate emission of a diesel engine are affected by the consumption of lubricating oil.Most studies on oil consumption mechanism of the cylinder have been done by using the experimental method,however they are very costly.Therefore,it is very necessary to study oil consumption mechanism of the cylinder and obtain the accurate results by the calculation method.Firstly,four main modes of lubricating oil consumption in cylinder are analyzed and then the oil consumption rate under common working conditions are calculated for the four modes based on an engine.Then,the factors that affect the lubricating oil consumption such as working conditions,the second ring closed gap,the elastic force of the piston rings are also investigated for the four modes.The calculation results show that most of the lubricating oil is consumed by evaporation on the liner surface.Besides,there are three other findings:(1) The oil evaporation from the liner is determined by the working condition of an engine;(2) The increase of the ring closed gap reduces the oil blow through the top ring end gap but increases blow-by;(3) With the increase of the elastic force of the ring,both the left oil film thickness and the oil throw-off at the top ring decrease.The oil scraping of the piston top edge is consequently reduced while the friction loss between the rings and the liner increases.A neural network prediction model of the lubricating oil consumption in cylinder is established based on the BP neural network theory,and then the model is trained and validated.The main piston rings parameters which affect the oil consumption are optimized by using the BP neural network prediction model and the prediction accuracy of this BP neural network is within 8%,which is acceptable for normal engineering applications.The oil consumption is also measured experimentally.The relative errors of the calculated and experimental values are less than 10%,verifying the validity of the simulation results.Applying the established simulation model and the validated BP network model is able to generate numerical results with sufficient accuracy,which significantly reduces experimental work and provides guidance for the optimal design of the piston rings diesel engines.     

Tribodynamic modeling of piston compression ring and cylinder liner conjunction in high-pressure zone of engine cycle

Piston compression ring and cylinder liner contact contributes a significant part of friction loss in an engine. Most of this loss occurs during compression and power stroke transition (i.e., between 300° to 400° crank position). It is because of the combustion gas pressure is higher in this region to enhance ring–liner contact friction. In this paper, we developed a tribodynamic model to study the transient thermoelastohydrodynamics of ring–liner contact. It takes into account the combined solution of Reynolds equation, energy equation, and elastic deformation equation considering ring–liner conformability and rheology change. We estimate the minimum film profile, friction force, and friction power loss within a high-pressure zone of a high-performance engine. Roughness of the liner is characterized using R _k parameter for better surface representation.     

Oscillations of a cylinder liner of an internal combustion engine with a water cooling system caused by piston group impacts

The forced oscillations of a cylindrical shell surrounded by a liquid layer caused by impacts have been investigated based on the dynamic problem of hydroelasticity. The relationships describing the shell deflection, the pressure in the liquid layer, and the shell amplitude and phase frequency characteristics have been found. An example of calculation of the resonance frequencies of oscillations of a liner of an internal combustion engine with a water cooling system caused by piston group impacts is presented.     

Running-in wear of a compression ignition engine: Factors influencing the conformance between cylinder liner and piston rings

The conformance between the liner and rings of an internal combustion engine depends mainly on their linear wear (dimensional loss) during running-in. Running-in wear studies, using the factorial design of experiments, on a compression ignition engine show that at certain dead centre locations of piston rings the linear wear of the cylinder liner increases with increase in the initial surface roughness of the liner. Rough surfaces wear rapidly without seizure during running-in to promote quick conformance, so an initial surface finish of the liner of 0.8 μm c.l.a. is recommended. The linear wear of the cast iron liner and rings decreases with increasing load but the mass wear increases with increasing load. This discrepancy is due to phase changes in the cast iron accompanied by dimensional growth at higher thermal loads. During running-in the growth of cast iron should be minimised by running the engine at an initial load for which the exhaust gas temperature is approximately 180 °C.     

Influence of load on the tribological conditions in piston ring and cylinder liner contacts in a medium-speed diesel engine

The present work is an attempt to determine the oil film thickness in a medium-speed four-stroke diesel engine with a cylinder diameter of 200 mm. Experimental research on this topic was found necessary due to the limited amount of published information available with reference to engines of the present size. The experimental part of the study was carried out as firing engine tests, with an instrumented piston, equipped with telemetric data transmission, and an instrumented cylinder liner in a 6-in-line test engine. The study was carried out for different parts of the four-stroke working cycle and for different levels of engine power output. The results were compared with the results of computer simulations, carried out using a commercial software package. The conclusions of the study comprise aspects on the formation and development of the oil film between the rings and the liner under a set of load levels together with the periodical fluctuation during different strokes of the working cycle.     

Analysis and computation of the oil film thickness between the piston ring and cylinder liner of an internal combustion engine

A study of the essential features of piston rings in the cylinder liner of an internal combustion engine reveals that the lubrication problem posed by it is basically that of a slider bearing. According to steady-flow-hydrodynamics, viz. the oil film thickness becomes zero at the dead centre positions as the velocity, U = 0. In practice, however, such a phenomenon cannot be supported by consideration of the wear rates of pistion rings and cylinder liners. This can be explained by including the “squeeze” action term in the hydrodynamic theory, viz. .This article introduces the equations of the above theory along with the viscosity variation over the piston stroke length; the piston ring profile is assumed as a double parabola with a central straight portion.The results of this analysis as applied to internal combustion engines are presented and compared with other earlier analysis.