In the present paper, the algorithm proposed by Giacopini et. al. [1], based on a mass-conserving formulation of the Reynolds equation using the concept of complementarity is suitably extended to include the effects of compressibility, piezoviscosity and shear-thinning on the lubricant properties. This improved algorithm is employed to analyse the performance of the lubricated small end and big end bearings of a connecting rod of a high performance motorbike engine. The application of the algorithm proposed to both the small end and the big end of a con-rod is challenging because of the different causes that sustain the hydrodynamic lubrication in the two cases. In the con-rod big end, the fluid film is mainly generated by the relative high speed rotation between the rod and the crankshaft. The relative speed between the two races forms a wedge of fluid that assures appropriate lubrication and avoids undesired direct contacts. On the contrary, at the con-rod small end the relative rotational speed is low and a complete rotation between the mating surfaces does not occurs since the con-rod only oscillates around its vertical axis. Thus, at every revolution of the crankshaft, there are two different moments in which the relative rotational speed between the con-rod and the piston pin is null. Therefore, the dominant effect in the lubrication is the squeeze caused by the high loads transmitted through the piston pin. In particular both combustion forces and inertial forces contribute to the squeeze effect. This work shows how the formulation developed by the authors is capable of predicting the performance of journal bearings in the unsteady regime, where cavitation and reformation occur several times. Moreover, the effects of the pressure and the shear rate on the density and on the viscosity of the lubricant are taken into account.

In order to reduce friction losses and vibrations in main engine bearings, fluid film lubrication is combined to controllable radial oil injection. This work evaluates different geometric hybrid bearing configurations and control pressure rules for applying radial oil injection in main engine bearings of internal combustion engines. The conventional hydrodynamic lubrication ( CHL ) is combined with hydrostatic lubrication which is actively modified by radially injecting oil at controllable pressures, through orifices circumferentially located around the bearing surface. The behaviour of a main bearing of a medium size combustion engine, operating with radial oil injection and with four different control strategies is analyzed, giving some insights into the minimum fluid film thickness ( OFT ) and reduction of viscous friction losses. The behaviour of such parameters is compared to the case when the bearing operates with conventional hydrodynamic lubrication.

A significant part of the total parasitic loss in an internal combustion (IC) engine is due to the piston ring and cylinder liner friction. In this work, a piston ring-liner reciprocating test rig combined with non-invasive ultrasonic film thickness measurement system was used to understand frictional characteristic of the lubricant and the lubrication regime in the contact. Two test procedures were performed for three lubricants with different viscosities. These procedures were a step load increment at a constant speed and a step speed increment at a constant load. The results showed that minimum oil film thickness under the ring increased with speed and decreased with load but friction coefficient followed various trends depending on the viscosity of the lubricant.

The current paper investigates the correlation between oil film formation, cavitation and starvation during inlet reversal of an Internal Combustion (IC) engine piston-ring conjunction. Piston ring lubrication is critical in the vicinity of Top Dead Center (TDC) and Bottom Dead Center (BDC) where low entrainment velocity leads to very thin films. The current study predicts that cavities formed at the trailing edge of the contact before the entrainment reversal briefly survive at the leading edge after the reversal. This contributes to contact starvation and thinner films than previously thought.

To improve calculation of the oil supply to the main and conrod bearings in the combustion engine, it is possible to simulate plain bearings on a coupled elasto-hydrodynamic basis while allowing for partial-fill states. In an effort to advance the extended simulation technique, software has been developed by the Institute for Machine Components and Design (IMK) at the University of Kassel and validated in experiments. This paper describes the simulation software that has been developed, including the resultant findings on the lubricating oil requirement.

More than ever, the development process in the field of automotive engineering requires shorter development cycles for a higher range of vehicles. In order to meet the ambitious goals of the automotive industry regarding CO 2 reduction and at the same time increasing the vehicle requirements in view of comfort and dynamics, it is necessary to decrease the drivetrain weight. Parallel, research and development in the field of automotive engineering is e.g. characterized by power upgraded combustion engines and by higher transmission ratios in the drive train. As a result, the rising of the weight specific power should not involve a reduction of the drivetrain reliability and the related increase of the failure probability. These demands lead to the conclusion that lightweight and robust designs have to be applied for all drivetrain components. All these factors affect the dimensioning of today’s clutch systems and step up the demands for future clutch systems. Thus, organic friction facings are getting closer to their limits due to temperature resistance. Within the frame work of the Centre of Excellence in Research CER 483 “High performance sliding and friction systems based on advanced ceramics” one approach is to apply advanced ceramics as friction material for e.g. a dry running motor vehicle clutch using the ceramic specific benefits as wear and temperature resistance combined with lightweight design to fulfill today’s demands.

More and more attention has been paid to alternative fuel in internal combustion engine. One of alternative fuels is to convert straw biomass to biomass fuel. Various methods and apparatuses used for converting straw biomass to bio-fuel were invented and developed. However, alternative fuel from biomass can not be used well in internal combustion engine. The reason is complicated and relative with the separation technology of bio-fuel and corrosion, wear, lubrication and combustion chemical reaction between bio-fuel and the surface of combustion room. It is necessary to study the tribological properties of bio-fuel in order to instead the current gasoline or diesel oil in internal combustion engine in the future. In the present study, the straw based bio-oil obtained by liquidizing process was chosen to evaluate its lubrication by MQ-800 fourball tribometer, in which extreme pressure and friction coefficient and wear resistance were measured respectively. The experimental results showed that the extreme pressure of the bio-fuel was up to 392 N, and the extreme pressure of diesel oil was 333 N. The frictional coefficient of bio-fuel varies between 0.08 and 0.11. The wear scar diameter increased with load slowly in 30min. SEM images indicate that lots of thin and dense belt-like ploughs were presented on the rubbed ball surface. The chemical compositions of the worn zone on the ball surface were analyzed by XPS, the thermal property and variation of chemical compositions of bio-fuel before and after friction and wear tests were studied by TGA and GC-MS, respectively. It was shown that the rubbing surface film was composed of FeS, FeSO 4 and organic compounds with C-C, −COH and −COOH groups.

This research project investigated the wheel wear and tribological characteristics in wet, dry and minimum quantity lubrication (MQL) grinding of cast iron. Water-based Al 2 O 3 and diamond nanofluids were applied in MQL grinding process and the results were compared with those of pure water. During the MQL grinding using nanofluids, a dense and hard slurry layer was formed on the wheel surface and could benefit the grinding performance. Experimental results showed that G-ratio, volume of wear of the grinding wheel vs. the volume of material removed, could be improved with high concentration nanofluids. Nanofluids showed the benefits to reduce grinding forces, improve surface roughness, and avoid workpiece burning. Compared to dry grinding, MQL grinding could significantly reduce the grinding temperature.

Recently, a number of sensor principles to measure physical and chemical properties of lubricating oils were investigated. The crucial property of lubricating oils for some applications is the degree of acidification as there is a correlation to corrosive wear of engine components. Corrosiveness is of particular importance for biogas engines due to the fact that bio-fuels are forming more aggressive components during the combustion process as in comparison with conventional fuels. Recent research showed that the corrosiveness of oil cannot be described sufficiently by conventional oil parameters such as total acid number and neutralization number. We propose a sensor concept using the effect of material loss of a thin metal film due to corrosion. The signal of the sensor being immersed in used gas engine oils with corrosive compounds showed good correlation with selected oil properties determined in the laboratory.