The Effects of Cylinder Wall Surface Roughness and Bore Distortion on Blow-by in Automotive Engines

A laboratory test device, was developed to study the effects of cylinder wall, surface roughness and bore, distortion on blow-by in automotive engines. The test device was constructed of components from a four-cylinder engine with a test box welded into the engine block to take the place of one of the cylinders. Removable liners used in the lest box were honed to varying surface roughnesses and bore distortion levels, Blow-by, used as a measure of conformance between the piston rings and cylinder walls, was found to increase at the end of the test with increasing initial distortion and initial surface roughness.     

Effect of Initial Cylinder Liner Honing Surface Roughness on Aircraft Piston Engine Performances

Reciprocating piston engines are the major propulsion devices for light aircrafts, helicopters, and essentially all automotive vehicles. They are expected to fulfil both present-day and future demands for engine performance, durability, fuel economy, and exhaust emissions legislation. One of the key factors related to these demands is the need to the limit thermomechanical internal losses, wear, and lubricating oil consumption, which are in turn conditioned by the tribological behavior of the piston–cylinder assembly. Consequently, this latter system requires a multi-directional approach in terms of manufacturing. Apart from various modifying techniques (e.g. laser texturing), a conventional plateau-honing operation is still the standard technology for shaping cylinder liner surface microstructure. This paper describes the distinctions between variations in the performance of the engines in relation to cylinder liner roughness parameters due to different honing settings. Five air-cooled reciprocating aircraft engines (FRANKLIN 4A-235-B31) served as the objects of research. The engines passed durability tests on the dynamometer bed, including operation under artificially intensified wear conditions. The results show a significant impact of the brand-new honed cylinder liner surface microstructure on the engine output parameters. Detailed study proves that some of the cylinder liner roughness parameters, specifically, the slope of the root mean square line (RMS) for valley roughness Rvq and the linear triangle area for valleys A2, are strongly correlated with the engine operational properties. Higher values of Rvq and A2 are associated with an improvement in engine performance but result in a deterioration in the exhaust harmful emission.     

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.     

Engine Wear Monitoring with OLVF

In this article, an on-line visual ferrograph (OLVF) was used to monitor the wear condition of a vehicle engine during a bench test. A quantitative index of particle coverage area (IPCA) and wear debris ferro-image were obtained via OLVF to characterize wear degrees. On-line ferrograph analysis indicated some problems with the engine from about the 17th hour. A linear threshold value method to identify running condition of engines with the OLVF data was proposed. The OLVF data were in a fault zone after running for 25 h, when a base bolt broke and the engine stopped working during the test. The engine was disassembled and inspected after the test. Several wear scars were found on the cylinder walls as well as on the bearing surfaces. The oil was added at the 26th and 55th hours, which was also reflected by the variation of IPCA. Moreover, several off-line analyses were carried out in parallel. Off-line ferrograph data did not give any information about the abnormality and only showed stable wear debris content. Spectrometric oil analysis showed that there was no significant change in contents of metal elements.     

The Effects of Roughness on Piston Ring Lubrication—Part II: The Relationship between Cylinder Wall Surface Topography and Oil Film Thickness

In this investigation, a theoretical piston ring/cylinder wall model has been utilized to study the dependence of the oil film thickness on surface roughness shape and amplitude, as well as on engine operating conditions. For a given roughness, a plateau honed cylinder wall surface was found to produce a thinner oil film. It has also been shown that the small crosshatch angle used when honing the cylinder wall produces surfaces that enhance hydrodynamic action.     

Surface topography and tribology of cast iron in boundary lubrication

This work aims to study and understand the influence of the surface topography on wear of grey cast iron used for heavy duty diesel engine cylinder liners. A micro-alloyed grey cast iron was tested with different surface topographies. These were polished surfaces, honed surfaces (with two different honing parameters) and three model surfaces with well defined grooves on a polished specimen.Reciprocating friction tests using a steel ball rubbing against a flat or a cylindrical sample (extracted from a cylinder liner) were carried out on a Cameron Plint test rig. A commercial synthetic oil for diesel engine was used as the lubricant. The friction coefficient and the electrical contact resistance were measured during the tests. The wear volume of the cylinder liner part was also measured at the end of the test.The influence of the surface topography on the tribochemical film formation and on the wear behaviour of cast iron was established. Surfaces exhibiting lots of surface asperities had the highest wear, mainly due to delayed formation of protective tribochemical film. In our test conditions, the spacing between the grooves on model specimens had no influence on the wear behaviour of the cast iron specimens.     

仿生织构形态对缸套-活塞环摩擦学性能的影响

为了提高缸套-活塞环的摩擦学性能,设计了一种仿生排布的菱形凹坑织构,并通过激光刻蚀技术在缸套表面进行加工;在同一转速和不同载荷下,在MWF-10往复式摩擦磨损试验机上进行试验,以探究仿生排布的菱形织构对缸套-活塞环摩擦副摩擦磨损性能的影响,并与使用阵列排布的纹理的缸套以及未经处理的原始缸套进行比较。结果表明:织构的排布形式对油膜厚度的影响较大,尤其在重载荷工况下,合理地优化排布形式能够实现较好的动压润滑效果;仿生排布的菱形织构实现了往复运动方向上纹理特征的全覆盖,能够极大程度上限制磨屑的移动并对磨屑进行收集,有效降低磨损后的表面粗糙度,从而减少磨粒磨损;仿生排布的菱形织构在各试验工况下能够有效提高油膜厚度,提升表面承载能力,实现最佳的润滑效果。     

Tribological evaluation of coconut oil as an environment-friendly lubricant

Increased concerns about environmental damage caused by mineral oil based lubricants, has created a growing worldwide trend of promoting vegetable oil as base oil for automobile lubricants. Coconut oil, which is abundantly available in southern states of India, is reportedly being widely used as two-stroke engine lubricant (2T oil) by autorikshaw¹ drivers. A survey among the users of coconut oil as 2T oil brought forth complaints of increased engine wear. This paper presents tribological properties of coconut oil evaluated using a four-ball tester and a test rig to test the wear on two stroke engines. The influence of an antiwear/extreme pressure (AW/EP) additive on the tribological performance of coconut oil was also evaluated experimentally. The addition of the AW/EP additive has brought about considerable reduction in wear with coconut oil as 2T oil.     

Wear behavior of polymeric compositions in dry reciprocating sliding

The development of Stirling engines as high efficiency motors for automobiles is critically dependent on the ability of sliding seals to operate for long periods (up to 3500 h) without excessive leakage or wear. Piston rings must run completely dry while sealing against hydrogen leakage under a pressure drop of 5–20 MPa. Main seals, cooled by oil, must seal against similar pressures without admitting any oil which could contaminate the high temperature sections of the engine.The results of an initial search for materials with lower wear rates than the polytetrafluoroethylene (PTFE) polymer compositions currently used in test engines are described in this paper. On the basis of a literature review, the results of engine development tests and experience with solid lubricants, several commercially available formulations were selected for a screening test program. In addition, some custom formulations were prepared by commercial vendors.A reciprocating screening tester, operating at 1200 cycles min^?1 with a stroke of 40 mm, was used to determine material wear rates at a PV factor below the first PV limit of the reference PTFE material. Materials with wear rates in the range of 0.13 × 10^?6–0.16 × 10^?6 mm³ N^?1 m^?1 (the reference material wear rate was 0.40 × 10^?6 mm³ N^?1 were found.Friction coefficients were also measured since friction power loss in the seals represents a significant portion of the total mechanical engine losses. Compositions which significantly reduced the friction coefficient while retaining a low wear rate were found.     

Challenges of simulating ‘fired engine’ ring-liner oil additive/surface interactions in ring-liner bench tribometer

Abstract

This study focuses on evaluating the tribochemical processes occurring in a fired engine test and a bench tribometer with the aim of identifying the challenges related to simulating fired engine oil additive/surface interactions in laboratory conditions. Tribofilms formed in cylinder liner and piston ring surfaces from a fired engine test and a bench tribometer are chemically characterised using the X-ray photoelectron spectroscopy (XPS). This study confirmed that the chemical nature of tribofilms formed in a fired engine and a reciprocating bench tribometer are different, not surprising considering the substantially different lubrication environments between the tests. The factors necessary to be considered to improve the simulation of fired engine tribochemistry processes in laboratory conditions are identified and discussed.     

Sliding wear behavior of protective coatings for diesel engine components

The use of heat-insulating ceramic coatings on the cylinder walls of diesel engines is currently being considered for certain advanced engine designs. Since a major consideration in such an application is the wear resistance of the coatings, a series of tests has been carried out to determine the sliding wear behavior of several pairs of candidate materials systems, initially at room temperature. The tests were performed using a washer-on-disc specimen configuration and an oscillatory rotation movement to simulate the motion of a piston ring on a cylinder wall. It was determined that each material tested had a different pattern of sliding wear behavior. Impregnation of plasma-sprayed Y₂O₃-ZrO₂ with chromia markedly improved its wear resistance.     

Effects of honed cylinder surface topography on the wear of piston-piston ring-cylinder assemblies under artificially increased dustiness conditions

This paper presents results of the measurement of the surface roughness and other physical properties of the outer layer of honed cylinders. The cylinders tested had various surface topographies as a result of honing by abrasive tools of differing design. The results of wear measurements of the cylinders and piston rings mating with them during automotive gasoline Polonez 1500 engine operation under artificially increased dustiness conditions are presented and analysed.     

Influence of Surface Groove Width on Tribological Performance for Cylinder Liner–Piston Ring Components

Surface groove width is of great significance to the performance of the cylinder liner–piston ring (CLPR) with the different surface textures in marine diesel. However, little is understood about the specific application (e.g., the geometric parameters of surface textures and operating conditions) of surface texture in actual marine diesel engines. To address this issue, different surface groove textures including grooves structures with 1-, 2-, 3-, and 4-mm widths were designed based on previous results related to marine diesel engine applications. A series of experimental tests was conducted in a reciprocation tester, and data on the friction characteristics were obtained under different operating conditions. Comparative studies on the friction coefficients, worn surface features, and oil film characteristics were performed. Results showed that the 2-mm groove structure of the cylinder liner was more favorable for improving the wear performances at low speed, whereas a 3-mm groove structure of the cylinder liner was more suitable for improving the wear performance at higher speeds, though its wear performance needs to be improved under high load. These results help to understand the specific application of surface texture on the wear performance of the CLPR pair.     

普通机床加工发动机缸盖球形燃烧室的工艺试验

发动机缸盖是发动机的关键零部件.发动机缸盖的燃烧室容积,直接影响到发动机的工作性能,所以在发动机缸盖制造过程中,最终必须保证发动机缸盖燃烧室的形状、表面粗糙度、尺寸精度、容积等一系列参数,从而保证发动机总机性能.     

用SRV试验机评价柴油机油摩擦磨损性能

采用SRV^?4型摩擦磨损试验机为试验平台,以某商用车公司提供的发动机缸套-活塞环截取件作为摩擦副试验件,以15W-40 CF-4和15W-40 CI-4发动机油为润滑介质,建立评价柴油机油摩擦磨损性能的模拟试验方法,并使用该方法对油品配方中减摩剂的区分性及不同材质活塞环与润滑油的适配性等进行考察。试验结果表明:建立的模拟试验方法能较好地区分出具有优异抗磨性能的柴油机油,同样对油品配方中减摩剂和不同材质活塞环与润滑油适配性等有着较好的区分性,可以作为润滑油品开发者和OEM汽车厂家对油品配方开发和摩擦副材质筛选的模拟评价手段。     

The effects of low sulfated ash,phosphorus and sulfur oils on camshaft/tappet tribocouples with various diamond‐like‐carbon coated tappets in motored and fired engines

This work was conducted as part of an EU FP‐7 project ‘Tailoring of Tribological Interfaces for Clean and Energy‐Efficient Diesel and Gasoline Powertrains’. The primary goal of this work is to reduce fuel consumption in internal combustion engines by the use of bespoke surface coatings and lubricants. Earlier work within the project had defined a series of oils and coatings to be evaluated in the final stage of the project. The results reported in this paper have used the OM646LA engine to evaluate wear and a motored cylinder head manufactured from the same engine type to evaluate the friction performance of coating/oil combinations. The coatings were applied to the tappets in the valvetrain and tested against uncoated camshafts. It will be shown that diamond‐like‐carbons can offer frictional benefits over an all‐steel system and that the choice of lubricant can incrementally reduce friction further. It will also be shown that while some diamond‐like‐carbon coatings are durable enough to survive the fired engine test intact, others are completely removed; interestingly, in all cases, the wear on the counter‐surface, the cam lobes, was in the order of a magnitude lower than for the standard all‐steel system. Copyright © 2014 John Wiley & Sons, Ltd.     

Harmonic Wavelet Packet Analysis of Friction-Induced Vibration

Friction and wear tests of a piston ring against the cylinder of a marine diesel engine were conducted on a pin-on-disc tester. The vibration signals under different wear conditions were studied utilizing the discrete harmonic wavelet packet transform (DHWPT). It was shown that the weak friction-induced vibration signals could be extracted using the DHWPT. When the wear behavior is mild, the friction-induced vibration is linear. When the wear behavior is relatively severe, the friction-induced vibration changes from linear to nonlinear. When the wear behavior is more severe, the friction-induced vibration is nonlinear.     

Study on Influence of Cylinder Liner Surface Texture on Lubrication Performance for Cylinder Liner–Piston Ring Components

A marine diesel engine, where the cylinder liner–piston ring (CLPR) pair is one of the most important rubbing pairs, is the heart of a marine system. Studying the lubrication characteristics of the CLPR will provide a guide for rational design of the CLPR to reduce wear and prolong its service life. The surface texture features have a significant impact on the lubricating performance of the CLPR. In this study, the tribological system of the CLPR was investigated. Different surface textures (such as different sizes of surface concaves and grooves, etc.) were designed and produced on the cylinder liners using surface treatment. A series of experimental tests were then carried out in a specially designed diesel engine tester to investigate the tribological characteristics of the treated CLPR pairs. The comparison analyses of the worn surface texture features, element content of the lubrication oil, and abrasive particle characteristics were conducted under different wear surface texture features and cylinder liner speeds. The analysis results showed that there were significant differences in the tribological and lubrication properties of the rubbing pairs in different wear surface texture features. The wear performance of the CLPR pair with a regular concave texture was superior to that of the concave and groove, and regular groove textures. In addition, the regular concave with a depth-diameter ratio of 0.1 was the most effective surface texture to improve the lubrication and wear properties of the CLPR pairs. It is believed that the knowledge obtained in this study provides the real practical basis for tribological design and manufacturing of CLPR pair in marine diesel engines.     

Demonstrating Improved Fuel Economy Using Subsystem Specific Lubricants on a Modified Diesel Engine

Fuel economy performance in modern internal combustion engines is of increasing importance to lubricant formulators due to regulations targeting global greenhouse gas emissions. Engines typically employ a single lubricant, with a common sump, to service all components. As a result, base oil and additive selection for fuel economy performance is a compromise among competing demands for different engine subsystems. Opportunities for significant fuel economy improvement through targeted formulation of lubricants for specific engine subsystems are presented, with specific emphasis on segregating the lubricant supplies for the valve train and the power cylinder subsystems. A working prototype was developed in a lab environment by modifying a commercially available twin-cylinder diesel engine. Motored valve train and whole-engine fired test results were obtained and compared to model data. Fuel economy benefits were demonstrated using market representative heavy-duty diesel lubricants, including mineral oil and polyalphaolefin (PAO) blends. The fuel economy benefits of a dual-loop lubricant system are demonstrated through significant viscosity reduction in the power cylinder subsystem, achieving overall engine friction reductions of up to 8% for the investigated operating condition. Results suggest that additional gains may be realized through targeted base oil and additive formulation. Implications for incorporation in larger diesel engines are also considered.     

A Model for Wear and Friction in Cylinder Liners and Piston Rings

Abstract

A one-dimensional elstohydrodynamic mixed lubrication wear and friction model is developed. The model can predict the effects of surface roughness, asperity contact, temperature-pressure-viscosity on wear, lubrication, and friction of the piston rings and cylinder liner. Wear is predicted based on the surface asperity contact pressure. The cylinder bore wear and the ring pack friction during an engine break-in are simulated and compared with the experimental results. The influence of cylinder wall temperature and surface roughness on friction and wear is investigated. The ring pack friction due to oil viscous shearing and asperity contact is found to reach its minimum at a certain oil temperature.