Lubrication Engineers Research Articles

Experimental study of carbon nanotubes in high viscosity lubricants

Carbon nanotubes (CNTs) beneficial tribological properties were reported in numerous studies performed mostly in idealized tribometer conditions, previously described full engine tests confirmed that CNTs added to the lubricating oil reduced friction significantly. Apparently the engine application requires low CNT concentration in oil, otherwise when increasing the CNT concentration beyond a certain level oil viscosity increases, rapidly forming a greasy substance not suitable for engine lubrication. In this paper we report a study of tribological properties of such a high viscosity lubricant performed in Amsler tribometer in comparison to high quality commercially available lithium grease. The CNT based high viscosity lubricant in its current formulation turned out as not reliable for general application due to its low adhesion to the metal surface. In contrary to some samples made of a polymer widely used in industry as a friction component, we observed wear reduction reaching nearly 50% when replacing the best suitable lithium grease by a CNT based lubricant. This effect was first observed after 30 min into a friction test, suggesting a CNT related mechanism of anti-wear protection which still need to be explained.

Study on heavy-duty journal bearing lubrication based on Elasto-hydrodynamic lubrication method

Main bearing wear failure to become one of the main factors affecting the service-life of the engine, so it is necessary to form the effective analysis of the main bearing lubrication method, which is used in the design of main bearing lubrication and friction. In this paper, the model of substructure of V8 diesel engine is built based on flexible multi-body dynamics, the various nonlinear factors in the process of engine working process are considered, and the EHD of main bearings is analysed by the EXCITE software. On the basis of the V8 engine model, the bearing load and lubrication performances of different poly- condensation of main bearing are compared. The main bearing lubrication properties of the analysis results can be used for the engine lubrication system design and optimization.

Viscosity analysis of enriched SAE50 by nanoparticles as lubricant of heavy-duty engines

In this study, effective parameters on viscosity of a suitable oil for lubrication of heavy-duty engines (vehicles that are in use in construction, farm, and logging equipment, semi-trucks, delivery trucks, etc.) are studied. SAE50 as a single-degree engine oil is examined in present experimental work. The mentioned engine oil is enriched by MgO and MWCNT nanoparticles (NPs). The nanofluid was prepared in six solid volume fractions (SVF) and in temperature range of 25–50 °C. The results showed the viscosity dependence on shear rate, so nanolubricant has a non-Newtonian behavior. 2–4% Viscosity reduction in concentrations of 0.0625% and 0.125% reported in comparison with viscosity of pure fluid. Also sensitivity analysis of viscosity measurement was lower than 1% for all investigated conditions. To lower experimental costs, a mathematical correlation was proposed to predict the viscosity. The R2 was considered as criterion for accuracy of proposed correlation. Having amount of 0.9995 for R2 shows accommodation of correlation predictions with experimental results. Also maximum deviation of < 3% indicates that the proposed correlation has a high accuracy.

The Autoxidation of Alkenyl Succinimides—Mimics for Polyisobutenyl Succinimide Dispersants

Short chain alkenyl succinimides (ASIs) were synthesized and used as high purity chemical models to investigate the autoxidative degradation at 170 °C of polyisobutenyl succinimide dispersants (PIBSIs), a significant additive in automotive engine lubricants. Degradation products were characterized by gas chromatography–electron ionization mass spectrometry and quantified by gas chromatography-flame ionization detection. The rate of autoxidation of ASIs in a model lubricant, squalane, was also investigated. Although this is a complex molecule containing many possible sites of radical attack, all of the autoxidation products identified result from attack at the double bond or the adjacent allylic hydrogen atoms, which indicates the controlling influence of the double bond in the degradation of alkenyl succinimides, and therefore of commercial polyisobutenyl succinimide dispersants. The observed site-selective cleavage of the ASI structure, and by analogy PIBSI dispersants, would yield products that both reduce dispersancy and promote the formation of insoluble products that could have a detrimental effect on lubricant performance.

How much mixed/boundary friction is there in an engine — and where is it?

Automotive engines are believed to operate predominantly in the hydrodynamic regime, as evidenced by the (1) the successful strategy of reducing lubricant viscosity to reduce engine friction and improve vehicle fuel consumption, and (2) for most engine operating conditions, direct measurements of engine friction (either motored or fired) find that engine friction increases with increasing engine speed. However, certain components in an engine are known to operate mainly in the mixed/boundary lubrication (e.g. the valve train) and other components (such as the piston rings) operate in the mixed/boundary regime for a portion of the time. In order to quantify the amount of mixed/boundary lubrication in an engine, and in the individual components of the engine, motored and fired friction tests have been carried out for a range of lubricants (of differing viscosity grade, and with/without friction modifier additives). A full discussion of the implications of this work, which includes the impact of fuel dilution and “running-in” is included with insights given into how the work reported here guides the development of future fuel-efficient engine lubricants.

Effect of cold start on engine performance and emissions from diesel engines using IMO-Compliant distillate fuels

Emissions from ships at berth are small compared to the total ship emissions; however, they are one of the main contributors to pollutants in the air of densely-populated areas, consequently heavily affecting public health. This is due to auxiliary marine engines being used to generate electric power and steam for heating and providing services. The present study has been conducted on an engine representative of a marine auxiliary, which was a heavy duty, six-cylinder, turbocharged and after-cooled engine with a high pressure common rail injection system. Engine performance and emission characterisations during cold start are the focus of this paper, since cold start is significantly influential. Three tested fuels were used, including the reference diesel and two IMO (International Maritime Organization) compliant spiked fuels. The research engine was operated at a constant speed and 25% load condition after 12 h cooled soak. Results show that during cold start, significant heat generated from combustion is used to heat the engine block, coolant and lubricant. During the first minute, compared to the second minute, emissions of particle number (PN), carbon monoxide (CO), particulate matter (PM), and nitrogen oxides (NOx) were approximately 10, 4, 2 and 1.5 times higher, respectively. The engine control unit (ECU) plays a vital role in reducing engine emissions by changing the engine injection strategy based on the engine coolant temperature. IMO-compliant fuels, which were higher viscosity fuels associated with high sulphur content, resulted in an engine emission increase during cold start. It should be taken into account that auxiliary marine diesel engines, working at partial load conditions during cold start, contribute considerably to emissions in coastal areas. It demonstrates a need to implement practical measures, such as engine pre-heating, to obtain both environmental and public health advantages in coastal areas.

Modelling Transitions in Regimes of Lubrication for Rough Surface Contact

Accurately predicting frictional performance of lubrication systems requires mathematical predictive tools with reliable lubricant shear-related input parameters, which might not be easily accessible. Therefore, the study proposes a semi-empirical framework to predict accurately the friction performance of lubricant systems operating across a wide range of lubricant regimes. The semi-analytical framework integrates laboratory-scale experimental measurements from a pin-on-disk tribometer with a unified numerical iterative scheme. The numerical scheme couples the effect of hydrodynamic pressure generated from the lubricant and interacting asperity pressure, essential along the mixed lubrication regime. The lubricant viscosity-pressure coefficient is determined using a free-volume approach, requiring only the lubricant viscosity-temperature relation as the input. The simulated rough surface contact shows transition in lubricant regimes, from the boundary to the elastohydrodynamic lubrication regime with increasing sliding velocity. Through correlation with pin-on-disk frictional measurements, the slope of the limiting shear stress-pressure relation γ and the pressure coefficient of boundary shear strength m for the studied engine lubricants are determined. Thus, the proposed approach presents an effective and robust semi-empirical framework to determine shear properties of fully-formulated engine lubricants. These parameters are essential for application in mathematical tools to predict more accurately the frictional performance of lubrication systems operating across a wide range of lubrication regimes.

Impact of Engine Lubricant Volatility on Oil and Particle Emissions

Impact of Engine Lubricant Volatility on Oil and Particle Emissions

Comparison of hydrogenated vegetable oil and biodiesel effects on combustion, unregulated and regulated gaseous pollutants and DPF regeneration procedure in a Euro6 car

The effects of traditional biodiesel (fatty acid methyl-esters, FAME) and a hydrotreated vegetable oil (HVO) were comprehensively investigated on a production Euro 6 diesel car, including fuel injection rate and timing, combustion analysis, emissions of regulated and unregulated pollutants, and regeneration of the diesel particle filter. The use of both biofuels is a part of the efforts to reduce emissions of greenhouse gases and health-relevant pollutants and to improve energy security and sustainability. HVO, albeit more expensive, offers benefits relative to FAME in terms of oxidation stability, injector fouling, energy content and cetane number. The car was fitted with an on-board instrumentation and subjected to a range of driving cycles on a chassis dynamometer. The fuel consumption calculated from instantaneous emissions data based on exhaust gas composition measured by an on-board FTIR and calculated exhaust flow matched directly measured fuel consumption within several percent on all fuels; differences in the consumption among the fuels correspond to different heating values. The combustion onset and maximum heat release rate were comparable for diesel and FAME but were advanced on HVO due to its higher cetane number, causing, at times, multiple distinct heat release peaks, suggesting that optimization of fuel injection timing for HVO might be beneficial. Emissions of methane and ammonia were negligible, of N2O were measurable and slightly lower for HVO than for other fuels, of formaldehyde were limited to cold engine accelerations and highest for FAME and negligible for HVO, of NO and NO2 were high on all fuels during all operating conditions except for the type approval test. The results confirm several relative advantages of HVO over RME, with penetration into engine lubricating oil during particle filter regeneration to be further investigated. The effects of HVO lubricity and other long-term effects were not evaluated here.

Influence of piston ring profiles and oil temperature distribution on cylinder liner lubrication of a marine two-stroke engine

In the paper a comprehensive model of a piston-ring-cylinder (PRC) system has been presented. The local thickness of the oil film can be compared to height of the combined surface roughness of a cylinder liner and piston rings. Equations describing the mixed lubri-cation problem based on the empirical mathematical model formulated in works of Patir, Cheng and Greenwood, Tripp have been ap-plied. The main parts of the model have been experimentally verified abroad by the author at the marine engine designing centre. In contrast to the previous papers of the author concerning the PRC system of combustion engines, new calculation results for a ma-rine two-stroke engine have been presented. Firstly the right selection of barrel-shaped sliding surface of piston rings has been analysed. Secondly the influence of oil temperature distribution along the cylinder liner on the lubrication of the PRC system has been assessed. The developed model and software can be useful for optimization of the PRC system design.

Afault Diagnosis Model of Marine Diesel Engine Lubrication System Based on Improvedextreme Learning Machine

The lubrication system provides lubrication oil to various moving parts in the marine diesel engine. Once faults occurred in lubrication system, it can result in dramatically damage to the diesel engine. Development of fast and accurate fault diagnosis method of lubrication system is therefore highly urged. In this paper, we present a novel intelligent fault diagnosis methodbased on improved extreme learning machine (ELM). Firstly, we use chaotic mapping to enhance capability of the particle swarm optimization (PSO) algorithm; Then, an enhanced PSO algorithm is used to determine initial input weights (connecting input layer nodes and hidden layer nodes) and thresholds of ELM. Finally, we carry out fault diagnosis experiment on the marine diesel engine lubrication system. The experiments demonstrated that the proposed model could achieve more ideal performance.

Measurements of fuel adhesion on cylinder walls and fuel wall-flow behavior with post diesel fuel injections

Post fuel injection in the expansion stroke is used for diesel particulate filter regeneration; however, fuel spray impinges on the cylinder liner due to the low temperature and pressure conditions. Fuel adhesion and fuel flowing down across the cylinder liner, the so-called “wall-flow,” was observed by high-speed video images, and this adhesion is a cause of diesel engine lubricant oil dilution and the deterioration of fuel consumption in diesel engines. In this article, the fuel adhesion and the wall-flow of post diesel fuel injections were investigated with a high pressure-temperature constant volume optical chamber. The in-cylinder temperatures and pressures at 30, 60, and 90 °CA ATDCs, conditions commonly employed in post fuel injection timings, were measured by an actual engine, and similar conditions were created in the constant volume chamber by the combustion of a pre-mixed gas of ethylene, oxygen, and nitrogen. Fuel masses of 0.6, 1.1, and 1.7 mg per hole were injected at each ATDC setting. The weight of the adhered fuel on the wall and the fuel in the piston-cylinder crevice were measured by precision balance, and the liquid–vapor phases in the spray were observed by Mie scattering and shadowgraph methods. To measure the thickness of the adhered fuel on the cylinder wall, the laser-induced fluorescence method was employed. The results show that the fuel spray penetration and adhesion on the cylinder wall were different in the test conditions investigated here. With the early post injection, most of the injected fuel vaporizes without penetrating to the cylinder liner and gaseous diesel fuel is condensed on the cylinder wall. A thin and widely spread out fuel film is formed on the cylinder wall; however, no wall-flow could be confirmed by the high-speed video images. With late post fuel injections, the strong penetration of liquid fuel reaches the cylinder wall, and a thick and widely spread out fuel film was formed on the cylinder wall and the wall-flow phenomenon was observed here. However, the quantity of fuel involved in the wall-flow was smaller than that of the fuel adhering to the cylinder wall. The effects of in-cylinder pressure and temperature on the fuel adhesion on the cylinder wall were investigated. With the increase in pressure and temperature, the quantity of adhering fuel was reduced, suggesting that the boost pressure increase by turbo charging and a higher engine load is effective to reduce fuel adhesion. Furthermore, the effects of multiple post fuel injections on fuel adhesion to the cylinder wall were investigated, maintaining the total fuel injection amounts. With increases in the number of fuel injections, the total percentage of adhering post fuel on the cylinder wall was reduced. In the multiple fuel injections, it was observed that fuel motion takes place during the spray pass after the first and second fuel injections and that the penetration length of the second and third fuel sprays increases.

Artificial neural network approach for locomotive maintenance by monitoring dielectric properties of engine lubricant

In this paper, we proposed an approach for locomotive maintenance systems by observing engine lube oil. The mechanical particles in lube oil give information about locomotive engine system condition. The engine lubricant is monthly monitored by a spectral analyzer (SA) to detect engine system failure and routine maintenance time. However, this old fashioned technique has many disadvantages such as non-real time measuring, high cost and time consumption. A novel approach is proposed to eliminate these disadvantages. The new method determines the lubricant sample conditions with respect to electrical characteristics by using artificial neural network (ANN). The study focuses on a relationship between mechanical particles (in ppm) and dielectric characteristics of the lube oil samples. Therefore, ANN method is applied to observe linear relation between observed and predicted dielectric constant and loss factor values of the engine oil samples. The electrical characteristics of the samples are observed at four frequency points (2.40 GHz, 5.80 GHz, 7.40 GHz and 9.60 GHz). ANN studies are realized by using data at these frequency points. The regression (R) coefficients are obtained as 0.7239, 0.7951, 0.8513 and 0.7463 for dielectric constant and 0.7627, 0.7196, 0.8015 and 0.7334 for dielectric loss, respectively. Moreover, the mean square error (MSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) are calculated and examined. The obtained results are very sufficient and this approach can be applied to a sensor device having low cost and real time working mechanism in the future.

Identification of jet lubrication oil as a major component of aircraft exhaust nanoparticles

Abstract. Jet engine aircraft are ubiquitous and significant sources of atmospheric nanoparticles. Using size-resolved particulate samples collected near a runway of the Narita International Airport, Japan, we clearly demonstrate that organic compounds in the ambient nanoparticles (diameters: &lt; 30 nm) were dominated by nearly intact forms of jet engine lubrication oil. This finding provides direct evidence for the importance of unburned lubrication oil as a source of aircraft exhaust nanoparticles and also has an implication for their environmental impacts near airports and in the upper troposphere.

Optimal Parameters of Grooved Conical Hybrid Journal Bearing With Shear Thinning and Piezo-viscous Lubricant Behavior

To harness higher axial load capacity, a larger cone angle is used in conical bearings, resulting in an increase in the surface area which in turn increases the frictional power loss. The use of microgrooves in journal bearing helps in controlling this loss. Therefore, the present work is aimed to analyze conical hybrid journal bearing (i.e., combination of hydrostatic and hydrodynamic modes of operation) consisting of microgrooves along with shear thinning and piezo-viscous behavior of the lubricant. In this study, the microgroove attributes have been optimized by obtaining the solution of a Reynolds equation using finite element method and generalized minimum residual scheme (GMRES). These optimized groove attributes are used for numerically simulating the performance of the conical bearings. It has been observed that the best features of microgrooves and shear thinning behavior of the lubricant can be extracted to achieve better performance of the bearings. The results presented in this study are believed to be beneficial to the bearing designers and practising lubrication engineers.

Existence and uniqueness results for compressible Reynolds equation with slip boundary conditions

ABSTRACT In this paper a one dimensional system describing the behaviour of a thin film flow (lubrication assumption) is analysed for various non linear slip conditions on the solid surface including Tresca shear limited models. So far, existence results for such problems require an incompressibility assumption. In the present work, this assumption is removed, allowing cavitation to be taken into account. The possibility of considering such models including simultaneously cavitation and slip/no-slip conditions is of practical importance as this corresponds to the actual trend in lubrication engineering.

Pengaruh Penambahan Zat Aditif X terhadap Viskositas, Performa Mesin dan Emisi Gas Buang Sepeda Motor Honda CB150R

&lt;em&gt;Mechanical contact is the process which can not be avoided in machinery system. The way to diminish thrist conditon which caused by the process is to give engine lubricant into that system. The lubricant resistance over the temperature system is influenced by base stock and its additives where contained of. Lubricant oil additives are chemical compounds that will improve or enhance the lubricant performance of base oil. These additives are carefully designed to ensure the functions in machines system. Engine lubricant that used in this research is MPX 1 SAE 10 W-30 and the additives that used is Engine Additive with brand Lupromax. The aim of this research is to analyze the reaction of increasing the additive EA over to viscosity and machine function of Honda All New CB 150R. In this research, it is found that the fusion with EA 5.25% (1200 ml lubricant with 63 ml additives) could: (1) reduce viscosity to 66.56 mm&lt;sup&gt;2&lt;/sup&gt;/s and 9.9 mm&lt;sup&gt;2&lt;/sup&gt;/s at temperatures of 40°C and 100°C, respectively, (2) enhance the torque and energy to 14.5 kW @9000 rpm and 12.23 Nm @7000 rpm with reducing the rate emision of CO to 0.44% vol, HC to 196 ppm vol, CO&lt;sub&gt;2&lt;/sub&gt; to 6.5% vol and enhancing the rate of O&lt;sub&gt;2&lt;/sub&gt; to 10.71%, and (3) reduce fuel consumption to 18.75 ml/km.&lt;/em&gt;

Film Forming Capability of Polymer-Base Oil Lubricants in Elastohydrodynamic and Very Thin Film Regimes

The development of high-performance lubricants to insure the separation of mechanical parts, to reduce engine friction and consequently fuel consumption remains a major challenge for oil manufacturers. Polymer additives called viscosity index improvers (VII) have been extensively used to reduce the dependency of the lubricant’s viscosity on temperature, to maintain an acceptable hydrodynamic lubrication in extreme conditions. This work focuses on understanding the role of VII in engine lubricants to bridge their tribological response with their rheological behavior. Simplified lubricants are studied, composed of polymers of different chemistries, molecular weights and conformations added to a mineral base oil. Film thickness measurements are carried out in pure rolling and isothermal conditions to quantify and clarify the effect of polymer addition on the lubricants behavior in the elastohydrodynamic (EHD) and very thin film (VTF) regimes. They are compared with accurate analytical predictions based on rheological models which lead to a good agreement with measured film thicknesses in the EHD regime, whereas some polymer solutions present a significant deviation to EHD predictions at lower thickness, i.e. in the VTF regime. Several explanations are considered, among them the non-Newtonian behavior of the lubricants and the adsorption of some polymers on the surface of the solid bodies.

Adsorption properties of molybdenum based FMs on boron-doped DLC

Development of low friction surface materials matched with low friction lubricants is an important route to improving engine efficiency and reducing emissions. Diamond-like carbon (DLC) is a material of interest because it combines the durability of diamond with the low friction properties of graphite. Consequently, various forms of DLC have been studied as durable, low friction surface coatings. At the same time, friction modifiers (FMs) are often used in engine lubricants to produce low friction surface layers. Molybdenum-based friction modifiers are commonly used additives that mechanochemically decompose to cover surfaces with MoS2, a solid lubricant. FMs can also reduce friction on DLC surfaces. However, molybdenum can be harmful to DLC and cause rapid degradation and breakthrough of the DLC surface layer. We have found that the wear debit of molybdenum FMs trends with surface affinity of the additive. The adsorption isotherms of 4 Mo-based FMs on boron-doped diamond-like carbon (BDLC) were measured with a quartz crystal microbalance (QCM). The strongest adsorbate, Mo dithiophosphate (MoDTP), which also forms the thickest film, protects the BDLC surface enabling low friction while keeping wear low. Theoretical predictions based on molecular dynamics simulations combined with molecular-thermodynamic theory (MD-MTT) show that adsorption of MoDTP on BDLC deviates significantly from Langmuir behavior and free energy of adsorption for the first monolayer is significantly more negative than the multilayer adsorption free energy observed experimentally. The relationship between wear and adsorption behavior is consistent with experimental observations in the literature. These results also suggest that additive performance in a fully formulated lubricant is related to fundamental adsorption properties measured on the neat additive.

Study of the influence of emission control strategies on the soot content and fuel dilution in engine oil

Abstract The engine oil contamination by both particulate matter (PM) and fuel is becoming an important problem since strategies to control pollutant emissions in internal combustion engines (ICE) significantly increase their presence in engine oil. As a consequence, the engine oil loses its tribological properties compromising engine lubrication and leading to potential problems in engine such as wear, corrosion, etc. For that reason, the study of the oil degradation and contamination due to these strategies have a special interest to the engine manufacturers and engine oil formulators. In this paper, the engine oil soot content and fuel dilution is analysed under real engine conditions. The study is addressed from two different but complementary points of views. First, on-line measurements at several engine operating conditions are performed in order to further understand how the soot generation correlates with the oil soot content and other derived problems on oil performance. Then, experimental data available after the experimental campaign is used to calibrate a numerical model, based on Computational Fluid Dynamics (CFD), that estimate the amount of soot particles settled in the engine oil. Results show that soot particles are more present in oil when operating high load-speed conditions and during the Diesel Particulate Filter (DPF) regeneration cycles. Regarding the fuel dilution, delayed post-injections are critical since they significantly increase the amount of fuel in the engine oil. Numerical results also show the relationships between the soot particles generated during combustion and the amount of soot in engine oil, giving an enhanced comprehension of soot-in-oil deposition mechanisms.