Corrosive wear of diesel engine cylinder bore

Deleterious wear of the cylinder bore in diesel engines can be aggravated by alteration of combustion conditions, such as that brought about by use of Exhaust Gas Recirculation (EGR) equipment and consequent high mileage. This paper describes the influence of combustion products — i.e. sulphuric acid and carbon soot, which can be primarily concerned in corrosive wear — on lubrication under reciprocating sliding of a piston ring and on the bore wear.     

Effects of refined palm oil (RPO) fuel on wear of diesel engine components

In this particular research work, the effects of refined palm oil (RPO), as alternative fuel, on wear of diesel engine components are assessed. Fleet testing is carried for the qualifying candidates diesel fuel replacement, i.e. 100% RPO fuel or 50% RPO and 50% conventional diesel fuel mixture. The base line of the fleet testing is using pure conventional petroleum diesel fuel as an energy source in one of the tested vehicles in the fleet. Analysis of used engine lubrication oil, taken when the oil was changed on the vehicles, was compared to the analysis of used oil samples pulled from 100% diesel fuel engines. The finding suggested that the pure RPO and RPO blended fueled engines were wearing at a normal rate.     

An experimental investigation into the wear of the cylinder liner-piston ring in engines

In order to meet the demands of different engines, various kinds of material are used for the cylinder liners and piston rings. This paper describes a method and the results of wear tests for various liners and rings. These experiments were carried out on a FGM-1 wear simulation testing machine. The results help contribute to the rational selection and pairing of the liners and the rings.     

Soot characterisation and diesel engine wear

The hardness of various types of soot produced by heavy‐ and light‐duty diesel engines of European, Japanese, and North American designs was measured by low‐loss electron energy‐loss spectroscopy (EELS). No clear general trend can be established that shows heavy‐duty diesel engine soot is necessarily harder than light‐duty diesel engine soot. The variation in hardness among individual soot particles produced by the same diesel engine can be as large as differences between the hardest soot particles produced by heavy‐duty diesel engines and the softest soot particles produced by light‐duty diesel engines. There are heavy‐duty diesel engines that can produce soot that is softer than that produced by some light‐duty diesel engines and vice versa. Nevertheless, the hardness of all types of soot studied is close to the range of hardness of metal engine parts. Thus, the results indicate that soot is hard enough to abrade some metal engine parts.     

柴油机滑动轴承磨损试验系统的开发与研制

针对柴油机轴瓦磨损问题,为了研究滑动轴承磨损影响机理且由于现有设备无法满足试验要求,开发研制了一套滑动轴承磨损试验系统。利用该系统可进行主轴瓦和连杆瓦两种滑动轴承在结构、转速、载荷、磨粒、润滑油状态不同条件下磨损状态的模拟试验研究。在完成试验方法研究的基础上,着重介绍了该试验系统的液压模块、机械承载模块、润滑模块、试验控制模块等子系统的开发设计。该系统采用液压伺服的加载方式对模拟轴进行了拉压加载,采用变频器控制驱动电机转速,润滑油的压力及温度可以自由调节,并利用基于美国NI公司的LabVIEW环境的软件实现了对试验系统的自动控制以及试验数据实时显示和存储,实现了不同工况下的轴瓦磨损的模拟试验。研究结果表明,该试验系统可以实现试验功能,具有良好的试验性能,达到了试验系统开发的预期目标。     

Diagnosis and condition monitoring of medium-speed marine diesel engines

Diagnosis of diesel engines is not new and various methods have been proposed in the past for fault diagnosis. The problems relating to marine diesel engines, especially medium- and high-speed engines, are due mainly to their large size, which does not allow the use of trial and error methods, and their high operating speed. The most difficult problem occurs when the engine is not able to produce its maximum power, while there is no obvious fault or error. In the present work a method is described which attempts to offer a solution to such problems. The method is a thermodynamic one based on a simulation model and the processing of measured engine data. Presented is an application of the method to a medium-speed marine diesel engine, which suffered from low power output accompanied by high exhaust gas temperatures. The results from application of the method show that the problem is not a direct one, but is caused by many factors that result in improper operation. With this method, the current engine condition can be discovered, and suggestions made for proper tuning or repair. After conducting such an analysis, a vessel was able to achieve its maximum cruising speed, showing that the proposed method is a promising one.     

Predictions of cam follower wear in diesel engines

The rate of wear of cam followers in a valve train system is mainly a function of contact stress between the cam and the follower, sliding velocity and hydrodynamic film thickness between the two mating surfaces. The problem of surface fatigue wear becomes severe as the contact between cam and follower exceeds the plasticity limit of material. It finally leads to an increase in valve lash and loss of engine performance. The wear is minimised by reducing the coefficient of friction and by minimizing the compressive stress.In this paper, an attempt has been made to estimate the wear of followers quantitatively. The profile of followers resulting from steady and non-catastropic wear processes is computed by combining a linear wear relation and an elasto-hydrodynamic or boundary lubrication transition model with kinematic analysis. The finite element analysis, AVL TYCON simulation program and classical methodology have been effectively used to predict the follower wear. The model was validated on all types of followers widely varying in size, brake mean effective pressure and speed. The predicted wear profiles exhibit satisfactory agreement with experimental observations. At the end of the paper, a design guideline for designing a cam follower for low wear rate is given.     

ULSI制造中铜化学机械抛光的腐蚀磨损机理分析

以超大规模集成电路(ULSI)芯片多层互连结构制造中的关键平坦化工艺——铜化学机械抛光(Cu—CMP)为研究对象，针对Cu—CMP中存在的抛光液的化学腐蚀作用和磨料的机械磨损现象，采用腐蚀磨损理论分析了Cu—CMP材料去除机理。提出铜CMP的材料去除中存在着机械增强的化学腐蚀和化学增强的机械磨损，并分析了Cu—CMP的静态腐蚀材料去除、机械增强的腐蚀去除与化学增强的机械去除机理。     

内燃机气缸磨损量不解体检测方法的研究

基于光强反射能量法,提出了一种不拆缸盖情况下对内燃机气缸磨损量进行测量的系统,应用动态搜索的方法,确定最大磨损量位置,解决了探头空间定位的问题,并进行了实际气缸磨损量的对比测量实验.     

Lubricant related factors controlling oil consumption in diesel engines

Oil consumption control in internal combustion engines is affected by both engine design and lubricant related factors. In an attempt to study the lubricant related factors, an oil consumption measurement engine test, using the Mercedes-Benz OM 364A engine, was developed. The engine test data confirm the effects of viscosity and volatility. In addition, the results indicate that the selection of base oil and viscosity index modifier may have an effect on oil consumption which would not be predicted from the rheological properties of the oil. From various different engine tests, indications were obtained about a possible relationship between oil consumption and viscosity increase. A data search yielded results that confirm this correlation.     

化学复合镀层在NaOH中耐磨蚀性研究

研究了介质中NaOH浓度、镀层Cr2O3含量及热处理条件对低磷N i-P-Cr2O3化学复合镀层耐磨蚀性的影响,并与N i-P化学镀层进行了对比。结果表明:镀层的耐磨蚀性与介质中NaOH浓度呈线性关系,在任何NaOH浓度下复合镀层的耐磨蚀性均优于N i-P镀层;镀层Cr2O3质量分数在8%左右耐磨蚀性达到最佳值;经适当的热处理可显著提升镀层的耐磨蚀性。     

Ostwald ripening: a decisive cause of cylinder corrosive wear

Acids formed from fuel combustion and lubricating oil breakdown can promote corrosive engine wear. Using capillary video-microcopy to investigate the neutralization of sulfuric acid droplets by overbased additives in lubricating oil, we have found that the Ostwald ripening of acid droplets may be a decisive factor of corrosive wear because it prolongs the lifetime of larger acid droplets. This finding provides a new understanding of how acids corrode engine parts, and in particular, why the most corrosive engine wear often occurs at piston top dead center, and may lead to new strategies for engine designs and lubricating oil additives.     

Application of grey modeling method to fitting and forecasting wear trend of marine diesel engines

Oil monitoring is an important and useful method for predicting wear failure, and has been used in diesel engines successfully. The diesel engine is the key power equipment in ships and it is a complicated tribological system with uncertainty and indetermination. Grey system theory is suitable for systems in which some information is clear and some is not, so it is feasible to study the wear process of diesel engines with this theory. The unequal interval revised grey model (UIRGM) (1,1) is presented in this paper, which is applicable to original series with unequal intervals and sharp variation. The model that is built is applied to fit and predict element concentration as determined by oil spectrometric analysis. It is proved that UIRGM (1,1) determines the exact turning point, and the fitting and prediction results are acceptable.     

Ferrographic analysis of wear debris generated in locomotive diesel engines

A preliminary trial in which ferrography was applied to the condition monitoring of locomotive diesel engines is described in this paper. Typical particles generated by locomotive diesel engines are illustrated. Results of observations of those particles are discussed.     

Effects of cathodic protection on corrosive wear of 304 stainless steel

Corrosive wear involves interaction of electrochemical and mechanical processes. The synergism of these two processes often results in significant material loss, compared to those caused by individual processes. Reduction of either corrosion or wear may effectively decrease material loss under certain circumstances. Since cathodic protection can reduce corrosion of metallic materials, it may also diminish corrosive wear if the corrosion process is suppressed. However, under a cathodic potential (potentiostatic condition) or enforced current (galvanosatic condition), properties of a material could be affected and thus its corrosive wear behavior could be different from what is expected. The present research demonstrated that cathodic protection under potentiostatic condition was beneficial under low wearing force but it became ineffective under higher wearing forces or more negative cathodic potentials. Hydrogen embrittlement could be responsible for this change.     

三缸单作用柱塞泵十字头理论计算及有限元分析

介绍将理论与有限元相结合进行三缸单作用柱塞泵十字头强度分析的方法,以某柱塞泵十字头为例阐述理论分析与有限元分析的过程,并找出它的了危险点位置及应力值,且结果与实际情况相吻合.此研究方法,对同类问题的解决具有一定的参考价值.     

Tribocarbonisation of a synthetic engine oil in lubricated piston ring/cylinder bore sliding contact and its relation to friction and wear

Tribocarbonisation of a fully formulated synthetic engine oil, an API SJ/SAE 5W‐30 containing an organic molybdenum friction modifier, was investigated in an Optimal SRV® tribotester, with a Mo‐coated piston ring and a cast iron cylinder bore tribopair in lubricated sliding contact and under stepwise heating conditions. The friction characteristics were determined by the friction coefficient curve which showed that two local minimum values occurred as the temperature increased stepwise. The local minimum friction coefficient at the lower temperature of 290°C was the result of the formation of MoS₂ and MoO₃, tribochemically generated by MoDTC and ZDTP. For the other local minimum friction coefficient at the higher temperature of 400°C, FT‐IR and Raman spectroscopic examinations of the worn tracks on the cylinder bore samples indicated that tribopyrolysis of the oil components and simultaneous polycondensation into carbonaceous species had occurred. Detailed Raman analyses showed that the carbonaceous species included a disordered phase and an ordered phase characterised, respectively, by the D‐line (1370 cm⁻¹) and G‐line (1580 cm⁻¹). The peak positions and sizes of the graphite crystallites involved varied according to temperature, and were related to the specific points on the friction coefficient versus temperature curve. Tribochemistry could enhance pyrolysis of the oil and facilitate the production of the carbonaceous species and growth of the graphite crystallites.     

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.     

Surface anisotropy for monitoring the wear of IC engine cylinders

The present work proposes a methodology for monitoring the wear of internal combustion engine cylinders. This could be useful in calculating the time at which maintenance should be done on such a tribosystem or in determining its lifetime. On the basis of experimental data obtained using a friction—wear simulator, and through the determination of certain standardised and non‐standardised micro‐geometric parameters of the cylinder surface that change with respect to operating time, it is shown that the characteristic that exhibits the most variation is the cylinder surface anisotropy. This factor participates to a large degree in the partial hydrodynamic lubrication mechanism of the reciprocating piston ring system and, as it is associated with the stage of wear, better expresses the characteristics of the cylinder's worn surface. As a consequence, by prescribing a limit for the maximum acceptable anisotropy as a basic criterion, the ultimate tolerable stage of wear is controlled simultaneously and vice versa.