内燃机缸套活塞环系统的摩擦学设计

本文在系统思想的指导下,采用理论分析与润滑计算相结合,对内燃机摩擦副缸套一活塞环系统在正常工作时的摩擦,润滑、磨损等摩擦学行为进行了探讨,并根据研究结果。以桶面环为对象,以Ｓ１９５单缸紫机机的参数为例,编掉了通用内燃机摩这设计软件,以实现对内燃机缸套一活塞环系统的摩擦学设计和使用效果的预测。     

Analysis of ring pack lubrication

This paper describes a method developed for the simulation of ring pack lubrication characteristic in an internal combustion engine. In general, the quantity of oil supply for piston ring lubrication may be insufficient in filling the entire volume formed at the interference between the piston ring and the cylinder liner. Thus the oil starvation condition should be considered in analyzing piston ring lubrication. In order to reasonably estimate the amount of oil left over on the cylinder liner, the flow rate at the posterior portion of the interface should be calculated with an adequate boundary condition that confirms flow continuity condition. In this analysis, oil starvation and open-end boundary conditions are considered at the inlet and outlet of the piston rings. The lubrication characteristic of each piston ring is obtained by an iterative method with sequential steps. It is revealed that piston rings are operated under oil starvation in most operating cycles and the result under these conditions are quite different from that with the fully-flooded assumption.     

内燃机缸套-活塞环摩擦学研究回顾与展望

内燃机缸套-活塞环摩擦副是一个典型的摩擦学系统,其中含有多种类型的摩擦和磨损,润滑、摩擦、磨损的相互作用十分显著。其摩擦学性能对提高内燃机的可靠性和耐久性,保证内燃机经济、可靠地工作具有决定性的作用。其摩擦学问题的研究一直是人们关注的热点之一。     

The use of surface metrology instrumentation to measure rates of wear of internal combustion engine components

A study was made of the effects of operating conditions on internal combustion engine service life. It was found after extensive investigation of major engine components (piston, piston rings, bearings and cylinder liner) that engine service life appears to be more a function of the acceptable wear of the cylinder liner than of any other engine parts.A method was developed to determine the amount of cylinder liner wear; this involved measuring the depth of scratch marks (using Talysurf model 3 or Surtronic 3 instruments). We describe the method employed and the results; these are at least as reliable as and give more details than conventional methods.     

Investigation of heat transfer in an oil cooled piston with and without ceramic insulation on crown face

A numerical method is presented for calculating the temperature fields in a semi-adiabatic diesel engine piston having a cooling oil canal. The crown face of the piston is coated by a 2 mm thick oxide based ceramic insulating material. The non-ideal thermal contacts between the piston circumference and cylinder wall are also considered. A detailed analysis has been given for estimating the boundary conditions of the cylinder-piston assembly of an internal combustion engine. The isothermic distribution in the piston body and the heat flow rate through the different cooling media at four different engine loads have been depicted both for the cases with and without insulation coating. The results indicate a reduction (12–30%) in heat loss through the piston by use of an insulation coating at the piston crown face, assuming that both the heat transfer process from and the temperature of the combustion products remain unchanged.     

Piston Assembly Design for Improved Thermal-Tribological Performance

The tribological system in the piston assembly of an internal combustion engine includes contacts at interfaces of piston/piston ring/cylinder liner, piston skirt/cylinder wall, and piston/piston pin/ connecting rod. The thermal and tribological properties of the piston, piston rings, and cylinder wall are critical to the life and quality of the engine. Severe wear and scuffing failure, especially at the ring/ring groove and ring/liner interfaces, may present a major problem if the piston temperature is too high. Temperature considerations for the piston often limit the effort to increase the engine power.

A new engine piston incorporating the heat pipe cooling technology has been developed for reducing the piston temperature, especially in the ring land and along the piston wall. The current work aims at investigating the effect of reciprocating heat pipes on heat conduction in the piston, and thus the tribological behavior of the piston assembly. Due to the high thermal conductance of the reciprocating heat pipe, a considerably large amount of combustion heat, which is conventionally conducted through the piston wall, is transferred through heat pipes. This new design will result in a lower temperature on the piston wall and a reasonably low temperature distribution in the piston.     

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.     

内燃机活塞环组密封性能研究

为检验活塞环的密封性,进一步研究其摩擦学性能,建立内燃机环组密封数值仿真模型,模型中考虑气室体积、泄漏面积、内燃机运转工况和气室温度变化项等因素对活塞环密封性能的影响.以PA6-280柴油机为例,对活塞环组的密封性能进行仿真计算.结果表明,磨损对环组的密封性能影响很大,而工况对活塞环的密封性影响不是很明显;气室温度变化项对活塞环漏量影响较大,设计时不容忽视.     

Tribological performance of three advanced piston rings in the presence of MoDTC-modified GF-3 oils

The piston assembly (piston ring and cylinder bore) is one of the key parts of the internal combustion (IC) engine. Its performance will directly determine the performance of the whole engine. The piston assemblys tribological performance will be influenced by both its mechanical properties and the tribochemical interactions that take place on their surfaces. In this paper, three kinds of advanced stainless steel piston rings with a single nitrided layer, CrN coating on the nitrided layer and a B₄C and CrN binary-layer coating on the nitrided layer, respectively, were employed. Their frictional behavior and wear performance, when sliding against the cast iron cylinder bore materials lubricated with two kinds of GF-3 category mineral-based engine oils (one of them blended with MoDTC friction modifier), were investigated on a SRV tribotester. The test conditions were set and maintained to simulate engine-operating conditions. SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray spectroscopy) were employed to characterize the morphology and elemental composition of the wear tracks. Tribotests and analysis results indicate that changes in both the mechanical properties of the tribomate (piston coatings) and tribochemical interactions (formulation of engine oils) have an impact on the tribological performance of the piston assembly. Tribochemical interactions will have a more obvious influence on friction coefficients while the mechanical properties of the tribomate have a more obvious influence on wear.     

Tribological characteristics of one-process and two-process cylinder liner honed surfaces under reciprocating sliding conditions

This paper reports an experimental study of the effect of surface texture on cylinder liner wear. This research is important because the conjunction between piston rings and cylinder liner is one of the major sources to frictional losses in internal combustion engines. Experiments were conducted on a reciprocating tester. Specimens were cut from cylinder liners honed or plateau honed made of grey cast iron of hardness 218 HB. The honing operation was performed in order to obtain very similar values of the Sq parameter of one-process and two-process surfaces. In addition, one-process specimens characterised by different Sq parameter values were tested. Counter-specimens were made from chromium-coated steel C45. It was found that wear of two-process surfaces was lower than that of one-process surfaces characterized by the same Sq parameter. Linear wear of specimens was proportional to initial Sq parameter value. The effect of additional oil pockets created by the burnishing technique on cylinder liner wear was negligible.     

The piston ring or the piston seal?

Improvement in the efficiency of piston compression rings is considered. By taking account of the gas dynamics in determining piston-ring geometry and developing a system of piston rings and piston seals for various internal combustion engines, their basic performance and environmental characteristics may be improved.     

活塞气缸拍击特性及其磨损间隙变化关系

以某发动机气缸-活塞组为例,模拟了发动机气缸-活塞组中活塞的二阶拍击运动,根据二阶运动参数的模拟结果预测了气缸-活塞组件表面的磨损状态及磨损间隙。在此基础上,分析了气缸-活塞组间的间隙变化对活塞二阶运动的影响,获得了不同气缸套活塞磨损间隙的变化情况下,活塞在气缸套里做二阶运动时各种动态参数的变化规律。分析结果表明,所提出的方法能够有效预测因内燃机缸套活塞磨损间隙变化所引起活塞拍击特性的变化规律。     

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.     

Vortex motion induced by the piston of an internal combustion engine

A theory is developed for the calculation of the shear area of the vortex generated by a piston sliding on a stationary surface. The results are compared with those obtained experimentally from a test rig using water as the working fluid. Reasonable agreement has been obtained between theory and experiment. The work is of relevance to the study of gas motion in the cylinder of an internal combustion engine. It is concluded that the vortex motion is not important at high engine speeds.     

Numerical simulation of piston ring lubrication

This paper describes a numerical method that can be used to model the lubrication of piston rings. Classical lubrication theory is based on the Reynolds equation which is applicable to confined geometries and open geometries where the flooding conditions are known. Lubrication of piston rings, however, fall outside this category of problems since the piston rings might suffer from starved running conditions. This means that the computational domain where the Reynolds equation is applicable (including a cavitation criteria) is unknown. In order to overcome this problem the computational domain is extended to include also the oil film outside the piston rings.The numerical model consists of a 2D free surface code that solves the time dependent compressible Navier–Stokes equations. The equations are cast in Lagrangian form and discretized by a meshfree moving least squares method using the primitive variables u, v, ρ for the velocity components and density, respectively. Time integration is performed by a third order Runge–Kutta method. The set of equations is closed by the Dowson–Higginson equation for the relation between density and pressure. Boundary conditions are the non-slip condition on solids and the equilibrium of stresses on the free surface. It is assumed that the surrounding gas phase has zero viscosity. Surface tension can be included in the model if necessary. The contact point where the three phases solid, liquid, and gas intersect is updated based on the velocity of the solid and the angle between the normals of the solid and the free surface.The numerical model is compared with the results from an analytical solution of the Reynolds equation for a fixed incline slider bearing. Then results from a more complicated simulation of piston ring lubrication are given and discussed.     

The ricochet of spheres and cylinders from the surface of water

A theory of ricochet is proposed which permits the effect of projectile spin to be accounted for. This effect is not explained by previous theories. The critical angles for ricochet for a sphere and for a spinning cylinder are calculated, and the theory of the spinning cylinder is applied to the Barnes Wallis “bouncing bomb” developed during World War II.     

船舶柴油机气缸套拉缸机理的试验研究

根据模拟试验的相似准则设计磨损试验,研究对船舶航行安全构成严重威胁的异常磨损现象,例如拉缸和咬缸。试验结果表明硬化相的性能和含量与试验所选用的材料耐磨性相一致,且随着载荷的增加,材料发生拉毛的时间呈指数关系下降,本文根据摩擦副三滑磨面接触模型,进而提出摩擦界面温度升高导致粘着以及摩擦副表面的强烈摩擦导致硬化相的碎裂甚至折断等因素是气缸套异常磨损的根本原因,为预防气缸套拉缸或者咬缸提供了理论依据。     

Inverse combustion force estimation based on response measurements outside the combustion chamber and signal processing

Exposure to vibration has various physiological effects on vehicle passengers. Engine is one of the main sources of vehicle vibration. The major causes of engine vibration are combustion forces transmitted through the pistons and connection rods. Evaluation of sources is the first step to attenuate this vibration. Assessment of these sources is not an easy task because internal parts of machinery are not accessible. Often, instrumentation for such systems is costly, time consuming and some modifications would be necessary. Aim of the first part of this paper was to validate an inverse technique and carry out mobility analysis on a vehicle crankshaft to achieve matrix of Frequency Response Functions (FRFs). Outcomes were implemented to reconstruct the applied force for single and multiple-input systems. In the second part, the validated inverse technique and FRFs were used to estimate piston forces of an operating engine. Bearings of crankshaft were chosen as nearest accessible parts to piston connecting rods. Accelerometers were connected to the bearings for response measurement during an ideal engine operation. These responses together with FRFs, which were estimated in the previous part, were utilised in the inverse technique. Tikhonov regularization was used to solve the ill-conditioned inverse system. Two methods, namely L-curve criterion and Generalized Cross Validation (GCV), were employed to find the regularization parameter for the Tikhonov method. The inverse problem was solved and piston forces applied to crankpins were estimated. Results were validated by pressure measurement inside a cylinder and estimating the corresponding combustion force. This validation showed that inverse technique and measurement outcomes were roughly in agreement. In presence of various noise, L-curve criterion conduces to more robust results compared to the GCV method. But in the absence of high correlation between sources (f>600 HzHz), the GCV technique leads to more accurate results. This research shows that inverse techniques have great ability to estimate vibration sources inside the machinery.     

活塞环调质稀土离子渗氮处理耐磨性能试验

为改善活塞环磨损性能,在分析活塞环的基体组织、径向弹力及活塞环与气缸套的匹配状况对其耐磨性影响的基础上,对活塞环调质后表面进行稀土离子渗氮处理进行了试验研究,结果表明,活塞环的失效形式与基体组织有密切的关系,经调质处理获得的回火索氏体组织具有良好的综合力学性能和耐磨性;活塞环的径向弹力控制在235～285N为宜;在满足活塞环足够耐磨性的同时,还应考虑与气缸套硬度的合理匹配;台架试验结果表明,经稀土离子渗氮后的活塞环与渗氮气缸套匹配的耐磨性能明显誊千丘伽．钋弹措云靠．     

影响活塞铸铁环槽加工质量的因素初探

在内燃机技术逐渐发展过程中,发动机对于活塞环在使用寿命方面的要求越来越高,在此情况下,活塞铸铁环槽在进行机械加工时,质量要求也进入到了全新阶段,其中主要体现在对于活塞品种有了更高要求。为了实现活塞铸铁环槽整体加工质量提升,需加强对其机械加工整个过程的研究,运用理论结合实践方式,促进加工质量有效提升。