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.     

A rig test to measure friction and wear of heavy duty diesel engine piston rings and cylinder liners using realistic lubricants

Laboratory tests to evaluate piston ring and cylinder liner materials for their friction and wear behavior in realistic engine oils are described to support the development of new standard test methods. A ring segment was tested against a flat specimen of gray cast iron typical of cylinder liners. A wide range of lubricants including Jet A aviation fuel, mineral oil, and a new and engine-aged, fully formulated 15W40 heavy duty oil were used to evaluate the sensitivity of the tests to lubricant condition. Test temperatures ranged from 25 to 100 °C. A stepped load procedure was used to evaluate friction behavior using a run-in ring segment. At 100 °C, all lubricants showed boundary lubrication behavior, however, differences among the lubricants could be detected. Wear tests were carried out at 240 N for 6 h at 100 °C with new ring segments. The extent of wear was measured by weight loss, wear volume and wear depth using a geometric model that takes into account compound curvatures before and after testing. Wear volume by weight loss compared well with profilometry. Laboratory test results are compared to engine wear rates.     

Scuffing failure analysis and experimental simulation of piston ring–cylinder liner

The scuffing failure phenomenon of piston ring–cylinder liner is studied theoretically and experimentally. The load and bulk temperature when scuffing failure occurs are measured under different engine speed, lubricant, and environmental temperature in a bench test. Based on the experimental results, the asperity capacity when scuffing occurs is evaluated. Surface contact temperature is determined with the measured bulk temperature and the surface flash temperature calculated by Blok theory. The scuffing failure threshold of piston ring–cylinder liner is established by using specific oil film thickness. This revised version was published online in June 2006 with corrections to the Cover Date.     

Real-time diagnostic system using acoustic emission for a cylinder liner in a large two-stroke diesel engine

Damage that originates from abnormal wear in the cylinder liner of marine diesel engines causes a considerable loss of property to manage shipping vessels. However, because multiple factors contribute to such damage, it is difficult to anticipate the damage that is caused by abnormal wear, such as scuffing, by investigating the mechanism of abnormal wear. Therefore, several methods have been explored for predicting the abnormal wear between the cylinder liner and the piston ring in marine diesel engines. For example, methods that are based on an analysis of the temperature, vibration, or cylinder drain oil have been researched. However, the response time of such methods is too slow for an operator to have enough time to promptly cope with severe damage. The implementation of such methods also requires prior modifications to the engine, which cost time and money. To overcome such problems, methods of prediction that use AE (acoustic emission) have been widely investigated. Studies on the relationship between abnormal wear and AE signals have demonstrated that severe damage is preceded by a change in the RMS value of AE and the FFT amplitude of a specific frequency. However, previous studies on the AE technique were based on the offline analysis of stored data due to their focus on the relationship between abnormal wear and AE signals. Thus, for direct implementation of the AE technique in industry, a real-time diagnostic system is needed. This paper focuses on the development of a real-time diagnostic system for analyzing high speed AE signals and examining the wear status of cylinder liners in marine diesel engines.     

A study of the tribological behaviour of piston ring/cylinder liner interaction in diesel engines using acoustic emission

The novel use of non-intrusive acoustic emission (AE) measurements to provide information pertaining to the interaction between piston rings and cylinder liners in a range of diesel engines is investigated in this paper. In doing so, this technique is shown to offer a new method of investigation into this important interface in engine operation.AE generated during normal engine operation is known to consist of contributions from a number of different sources such as injector and valve activity. A recent finding has been the identification of AE signals associated with the ring/liner interface which presents the opportunity for in-service monitoring. This work discusses the possible AE source mechanisms, such as asperity contact, lubricant flow and/or blowby, through reference to a number of tests on motored and in-service small HSDI diesel engines and large, 2-stroke, marine diesel engines. The influence of various factors such as engine speed, load and lubrication is considered.     

柴油机气缸套磨损问题的GM(1,h)模型及其应用

柴油机气缸套磨损的预测与控制一直是一个难于解决的问题,采用GM(1,h)模型对气缸套磨损因素进行灰色关联分析,找出其中的主要因素,同时对气缸套磨损问题进行多因素预测,预测结果可以科学地指导企业在选择气缸套材料、售后服务和加工工艺方案的改进方面进行决策.     

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.     

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.     

柴油机气缸盖的模态分析

利用有限元法对柴油机气缸盖进行了模态分析,获得了气缸盖的基本振型和相关频率,与试验结果进行比较,两者有较好的一致性,因而可利用所建立的有限元模型完成气缸盖的动态响应分析及设计优化.     

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.     

基于有限元方法的柴油机活塞热分析

介绍运用有限元方法对柴油机机活塞进行热分析的方法。具体针对某型号柴油机,分析其活塞稳态温度场和热变形。分析结果表明,活塞最高温度出现在活塞头部,为377.22℃;活塞轮廓的径向变形最大值为0.451mm,也发生在活塞头部。并对活塞热态纵向型线进行拟合,为活塞冷态纵向型线的设计提供参考依据。     

Effect of surface roughness on the lubrication properties of the piston ring and cylinder of an engine,and calculation of lubrication and power loss analysis of piston-ring pack of a S195 diesel engine

The effect of surface roughness on lubrication of piston ring and cylinder is examined. In particular, the temperature effect is considered, and a model proposed to overcome shortcomings in the previous mathematical model. Further, film thickness was measured by transducer capacitance method in a S195 diesel engine. The results found are consistent with theoretical results. In addition, the authors show quantitatively the value of friction power losses of the ring package of a S195 diesel engine.     

柴油机缸套断裂故障的原因分析及对策

针对实习中所见一台柴油发动机气缸套断裂的故障，结合该发动机的结构特点，归纳整理出产生故障的原因，并提出相应的故障诊断和排除方法。     

Analysis of the piston ring lubrication with a new boundary condition

Research on the inlet and outlet lubricational characteristics of the piston ring have been intense and ongoing. Many researchers had considered that the entire surface of the ring was enveloped in an oil film, but much experimental research has discovered that not all the entire surface was soaked. To consider a partially lubricated ring, the following conditions are presupposed; oil starvation is applied to the inlet region and the open-end assumption to the outlet region. This algorithm confirms flow continuity and permits the nadir of the pressure to go down to the saturation pressure. Using these new boundary conditions, the actual effective width participating in ring lubrication is determined and the minimum film thickness and flow rate for the ring pack can be calculated. The effective width is expected to be about 20 to 30 percent of the whole width of the ring, and the minimum film thickness is less than the result obtained by using the Reynolds cavitation boundary condition.     

活塞环-缸套二维润滑特性的研究

基于二维平均流量模型和微凸体接触模型，研究了活塞环的二维润滑特性，并考虑了活塞系统偏摆、润滑油粘度变化及表面粗糙度等因素的影响。通过计算获得了活塞环－缸套间油膜厚度的二维分布。结果表明，油膜厚度沿周向是不均匀的。本文还对活塞环开口位置及偏摆的影响做了定量的分析。     

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.     

Experimental study of wear interaction between piston ring and piston groove in a radial piston hydraulic motor

The wear interaction between piston ring and piston groove in a radial piston hydraulic motor was studied in regard to mass loss and changes in form and surface roughness. A specially developed test rig that simulates the tilting movements of pistons at the end of strokes was used in the test. The results show that wear on the piston ring groove can be up to 10 times greater than the wear on the piston ring. For both interacting surfaces, the dominant wear mechanism was mild wear. The results from a factorial design show that the form of the piston groove significantly influences the amount of wear.     

On the hydrodynamic lubrication analysis of piston rings

A theoretical hydrodynamic lubrication analysis of piston rings is presented. A numerical scheme is developed to solve the Reynolds' equation and the load equilibrium equation simultaneously. The hydrodynamic effects are examined in detail by considering solutions to the problem of lubricating the top compression ring in a two-stroke diesel engine. The minimum film thickness is computed throughout a complete cycle. The pressure profiles and film shapes at different crankshaft angles are presented. In the method proposed, the camtation boundary condition within the lubricated conjunction is included in the analysis.     

Moving textures: Simulation of a ring sliding on a textured liner

Numerical simulations of the ring/liner contact in which the liner exhibits a periodic texture (pockets) are reported. The mass-conservative Elrod–Adams model is used to treat cavitation, and the dynamics of the ring is considered with a linear mass that corresponds to actual engine compression rings. The results, computed at a Stribeck number of 10⁻³ and thus in the hydrodynamic lubrication regime, show that the ring profile determines whether pocketing is beneficial or not. For strongly non-conformal contacts pocketing is detrimental, but for quasi-conformal contacts friction reductions of up to 73% are predicted. The largest reduction in friction was obtained for textures consisting of close-packed arrays of circular pockets of diameter comparable to the size of the contact.     

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.