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.     

Effect of laser textured dimples on the lubrication performance of cylinder liner in diesel engine

Laser surface texturing (LST) technique was utilised on a cylinder liner in a diesel engine. In order to analyse the effect of LST micro‐dimples on the lubrication and friction properties of cylinder liner–piston ring (CL–PR), we developed a new mixed lubrication model on the basis of the average Reynolds equation and asperity contacts equation. The model can consider the coupling effects between the surface roughness of non‐texturing regions and micro‐dimples and the synergistic effects of multi‐micro‐dimples. The results show that cylinder liner surface by LST can form effective hydrodynamic lubrication effect in most regions of the strokes, only near the dead points, the friction pair is in mixed lubrication state, asperity contact plays a major role in balancing the external load and the asperity friction force is obvious. The micro‐dimple parameters were optimised to obtain a better lubrication effect with the following optimised results: r_p = 30–60 µm, S_p = 0.2–0.4 and e = 0.03–0.1. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

发动机汽缸壁耐磨性非概率可靠性评估和寿命预测

针对现有的可靠性分析方法的缺陷与不足,将发动机汽缸壁允许的磨损量和其实际的磨损量用区间变量来进行描述,在确定出发动机汽缸壁磨损失效功能函数的基础上,建立起发动机汽缸壁耐磨性非概率集合可靠性的计算模型;利用稳健回归方法对发动机汽缸壁的实际磨损量拟合出相应的预测方程,基于非概率集合可靠性模型,提出了发动机汽缸壁磨损寿命的预测方法。通过对工程实例的分析与计算,表明了所提出方法的可行性和合理性,此方法具有一定的工程应用价值。     

Estimation for fatigue limit reliability of a metal with inhomogeneities under stress ratio

In this paper, by using statistical characteristics of hardness in a small region and statistical characteristics of mechanical condition in a small region based on a defect size distribution and a certain stress which is applied to a defect, a quantitative prediction method for fatigue limit reliability of a metal with inhomogeneities is proposed. Also rotating bending and push–pull fatigue tests under R=-1 are carried out on quenched-tempered 0.5% carbon steels, whose average hardness is about H_V600. Comparing a predicted fatigue limit reliability with experimental data, the applicability of the present proposed method is examined and confirmed.     

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.     

Frictional evaluation of thermally sprayed coatings applied on the cylinder liner of a heavy duty diesel engine: Pilot tribometer analysis and full scale engine test

The piston system accounts for roughly half of the mechanical friction of an internal combustion engine, thus it is important to optimize. Different thermally sprayed cylinder liners were investigated in order to optimize the frictional impact of the contact between cylinder liner and piston ring/piston. A novel tribometer test setup was used to scan through different materials at different running conditions. Two cylinder liner materials showed significantly lower friction than the other tested materials, CrC–NiCr and MMC. All the thermally sprayed cylinder liners were worn significantly less than the reference material. Based on these results a full-scale single cylinder test was performed to validate the results from the rig. Comparing the thermally sprayed cylinder liner MMC with reference cylinder liner the test showed higher friction torque for the MMC cylinder liner except in one case; at low speed and high pressure. An analysis of the results between the tribometer and the engine points at the importance of the ratio between viscous and mechanical friction losses. The most probable cause of higher friction torque for the thermally sprayed coating (MMC) is that the functional surface of the cylinder liner promotes an increase in viscous friction.     

The effect of variable amplitude loading on stress distribution within a cylindrical contact subjected to fretting fatigue

A finite element model of a cylindrical Hertzian contact on a test sample subjected to alternating shear loading has been developed. The model has been used to investigate shear stress distributions at the contact during variable amplitude fretting fatigue for a load configuration in which the sample cyclic stress is applied in phase with shear force on the cylindrical contact. It has been found that during constant amplitude cyclic loading, shear stress distributions and positions of the stick-slip boundary at load maxima and minima remain fixed. Application of overloads changes the stress distribution and the position of the stick-slip boundary attained by loading of subsequent cycles. The largest cycle maximum stress determines the position of the stick-slip boundary adopted by subsequent smaller amplitude cycles. In general variable amplitude fretting fatigue the position of the stick-slip boundary will be changing with each load cycle. Hence fatigue initiation processes will occur at locations dispersed over an extended region over the contact. The implications of this behaviour for models for fretting fatigue life calculation are explored.     

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.     

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     

用Taylor展开随机无网格法分析齿轮弯曲疲劳强度的可靠性

这里用Taylor展开随机无网格点插值法(TSMPIM)分析了齿轮弯曲疲劳强度的可靠性。数值实例表明在随机结构分析与可靠性计算方面随机无网格法具有明显的优势。     

An evaluation of the influence of cylinder liner finish and synthetic lubricating oil on exhaust hydrocarbon species from an SI engine

As part of the continuing attempt to reduce emissions from automotive engines this paper investigates the effect of cylinder lubrication on hydrocarbon emissions, and shows that the effect of a synthetic oil on total emissions is insignificant. However, more positive results have been obtained using cylinder surface finish to control oil layers in the combustion chamber. Studies of the hydrocarbon species in the emissions showed significant differences due to surface finish profiles.     

船用柴油机气门导管与缸盖压装过程的研究与优化

柴油机缸盖是组成船用柴油机的核心部件之一,气门导管是柴油机气门的导向装置,其准确完成装配才能确保气门能够准确无误地做直线往复运动,气门导管与缸盖之间一般采用过盈联接,因此保证气门导管与缸盖的装配质量是十分重要的。主要分析了在不同过盈量的条件下,气门导管与缸盖装配过程中的压装力及由其引起的应力与位移变化情况,并以被包容件气门导管的内径作为优化参数进行优化,在满足实际工作要求的条件下,设计出最优的气门导管内径尺寸,得到二者过盈配合时的最佳配合尺寸,为气门导管以最小的压装力、应力和最佳过盈量压入缸盖内提供了理论参考,指导实际生产。     

Role of extruded texture on fatigue crack growth in a high strength aluminum alloy thick-walled cylinder

In present study, as a basic step for modeling the fatigue behavior of an extruded Al alloy cylinder, the fatigue crack growth data of the alloy was collected in two orientations. Microstructural analysis revealed that the material had recrystallized grains and clusters of constituent particles aligned in the direction of extrusion. Fatigue life of the samples revealed a shorter fatigue life representing a higher fatigue crack growth rate in transverse direction. The Paris constants C and m were found to be 4 × 10⁻¹¹ and 3.4 for the transverse orientation. The same constants were found to be 2 × 10⁻¹⁰ and 2.6 for the longitudinal direction. Post fracture analysis revealed that the topographical appearance of the fractured surfaces in two orientations was different. The mechanism of crack growth was the formation of striations. The present study revealed that the texture of the constituent particles created during extrusion process has a pronounced effect on the crack growth rate in two orientations. This paper was recommended for publication in revised form by Associate Editor Chongdu Cho Dr. M. A. Malik is a Professor in Department of Mechanical Engineering, College of Electrical and Mechanical Engineering, National University of Sciences and Technology, Rawalpindi, Pakistan. He graduated from Georgia Tech, USA with MS and PhD degrees in nuclear engineering. He has considerable working experience in nuclear research industry. He specializes in impurity transport and modeling and simulation techniques. His current research interests include structural analysis, reliability of materials and modeling and simulation of dynamic engineering systems. He has over 85 publications to his credit.     

A stress analysis of a shaft with a press-fitted hub subjected to cyclic axial loading

This paper presents a calculation of the stress distribution in a shaft with a press-fitted hub subjected to axial fretting fatigue. Both normal contact stresses and frictional shear stresses at the shaft-hub interface are included in the model. The solution of Airy's function is obtained by means of Fourier integrals. The results are presented for different combinations of hub length, shaft radius and non-slip area and for various values of the coefficient of friction. Special consideration was given to the axial component of the stress, σ_z, as this is the most important stress component in the initiation and propagation of fatigue cracks. Finally, the paper deduces the implications arising from the stress analysis on the fretting fatigue of the junction studied.     

大功率电力机车牵引扭矩过盈接触分析及可靠性寿命校验

新型大功率电力机车牵引电动机采用过盈配合传递牵引扭矩。为验证设计可靠性,首先计算完全理想状态下该过盈配合的接触状态,然后利用非线性有限元手段对过盈装配应力进行数值仿真。比较两种方法的计算结果之后,又对过盈装配进行疲劳寿命预测。结果验证了这种新型传力方式的可靠性。     

适合中国国情的发动机缸体与缸盖等箱体零件的敏捷柔性生产线(AFTL)的探讨

1.发动机缸体与缸盖等箱体零件AFTL的目的 (1)满足市场要求 满足当时市场(已知)的需求,同时还能快速适应将来市场(未知)的需求。 (2)满足发动机生产方式的要求 满足汽车发动机的“中品种、大批量、低成本”的生产方式。     

某小型涡喷发动机主轴可靠性分析

建立了某无人机用小型涡喷发动机主轴有限元模型,对该主轴进行有限元分析,得到该主轴的应力分布;采用蒙特卡洛与响应面相结合的方法,利用ANSYS软件,对该主轴进行可靠性分析,得到了不同概率下的主轴应力分布;这种方法可为发动机其它部件可靠性分析提供借鉴。