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Journal Article

A Multiscale Cylinder Bore Honing Pattern Lubrication Model for Improved Engine Friction

2019-07-02
Abstract Three-dimensional patterns representing crosshatched plateau-honed cylinder bores based on two-dimensional Fast Fourier Transform (FFT) of measured surfaces were generated and used to calculate pressure flow, shear-driven flow, and shear stress factors. Later, the flow and shear stress factors obtained by numerical simulations for various surface patterns were used to calculate lubricant film thickness and friction force between piston ring and cylinder bore contact in typical diesel engine conditions using a mixed lubrication model. The effects of various crosshatch honing angles, such as 30°, 45°, and 60°, and texture heights on engine friction losses, wear, and oil consumption were discussed in detail. It is observed from numerical results that lower lubricant film thickness values are generated with higher honing angles, particularly in mixed lubrication regime where lubricant film thickness is close to the roughness level, mainly due to lower resistance to pressure flow.
Journal Article

Dynamic Particle Generation/Shedding in Lubricating Greases Used in Aerospace Applications

2018-08-03
Abstract The purpose of this study is to examine the phenomenon of Dynamic Particle Generation in lubricating greases that are used in a variety of critical Aerospace mechanisms. Particle Generation occurs in bearings, ball screws, and other mechanical devices where dynamic conditions are present. This should not be confused with outgassing as particle generation is unrelated to the pressure effects on a system. This is a critical factor in many systems as particle generation can contaminate systems or processes causing them to fail. These failures can lead to excessive costs, production failure, and equipment damage. In this study, several greases made from Multiplyalkylated Cyclopentane and Perfluoropolyether base fluids were tested to evaluate their particle generation properties. This particle generation phenomenon was studied using a custom test rig utilizing a high precision cleanroom ball-screw to simulate true application conditions.
Journal Article

Elasto-Hydrodynamic Bearing Model in Powertrain Multi-Body Simulation

2018-04-18
Abstract Multi-body simulation is a well-established simulation technique in the analysis of internal combustion engines dynamics. The enhancement of multi-body simulation especially regarding flexible structures included effects of structural dynamics in the analysis and helped not only to broaden the field of application but also improved quality of the results. In connection to that there is a steady increase in the need for enhanced and refined modeling approaches for technical subsystems such as journal bearings. The paper on hand will present the elasto-hydrodynamic journal bearing module for the software FEV Virtual Engine which is a vertical application to the generic multi-body simulation suite Adams.
Journal Article

Exploring Engine Oil Reactivity Effects on End Gas Knock in a Direct-Injection Spark Ignition Engine

2018-03-07
Abstract An experimental study was conducted in a direct-injection (DI) spark-ignited engine to determine the extent to which oil reactivity impacts combustion phasing and knock propensity. Three engine oils were examined: a baseline 20W30 oil from conventional base stock, a 5W30 oil from a synthetic base stock, and a jet oil from a hindered ester base stock. The engine was operated at a constant fueling rate of 24.7 mg/injection for two engine speed conditions (1500 and 2000 rpm) using two cam profile conditions (high and low lift), for a total of four operating conditions. Spark timing sweeps were conducted at each of the four operating conditions. Results were analyzed for an engine oil impact on combustion phasing, cycle-to-cycle variability, combustion duration, knock propensity, and knock intensity. No correlation between engine oil type and any of these performance metrics could be identified.
Journal Article

Improvement in DCT Shaft Lubrication through CFD Method

2018-10-25
Abstract Dual-clutch transmission (DCT) output shaft 1 (OS1) mount position is higher than the transmission lubricant level. Needle bearings and idler gears on OS1-insufficient lubrication issues and the transmission lubrication system were investigated. In the design model, the transmission housing lubrication channel and oil guide component design were studied. For numerical analysis, the STAR-CCM+ software was used to simulate transmission internal complex oil-gas multiphase transient flow morphology that monitored the four bore oil churning volumes of OS1. Finally, lubrication test results affirm simulation predictions that idler gears, needle bearings, and synchronizer rings on OS1 obtain sufficient lubrication provided that a reliable method to inspect lubrication design functions is available.
Journal Article

Interference between Tin Sulfides, Graphite and Novolak Oxidation

2017-03-07
Abstract Tin sulfides (SnS and SnS2), represent a safer and greener alternative to other metal sulfides such as copper sulfides, and MoS2 etc. Their behavior is usually associated to that of solid lubricants such as graphite. A mixture of tin sulfides, with the 65 wt% of SnS2, has been characterized by scanning electron microscopy and by thermal gravimetric analysis (TGA). In order to investigate the effect of tin sulfides upon two crucial friction material ingredients, two mixtures were prepared: the former was made by mixing tin sulfides with a natural flake graphite and the latter was made mixing tin sulfides with a straight novolak. They were analyzed by TGA and differential thermal analysis (DTA) in both nitrogen and air. Some interferences were detected between tin sulfides and graphite in air.
Journal Article

LSPI Durability, a Study of LSPI over the Life of a Vehicle

2018-03-01
Abstract Increasingly stringent emissions standards and the related efforts to increase vehicle fuel economy have forced the development and implementation of many new technologies. In the light-duty, passenger vehicle segment, one key strategy has been downsized, down-sped, boosted engines. Gasoline direct injection, coupled with turbocharging, have allowed for a drastic reduction in engine size while maintaining or improving engine performance. However, obtaining more power from a smaller engine has produced some consequences. One major consequence is the uncontrolled combustion known as Low Speed Pre-Ignition (LSPI). LSPI and the high energy knocking event which frequently follows have been known to result in fractured pistons and catastrophic engine failure. The propensity at which LSPI occurs has been linked to engine oil formulation.
Journal Article

Thermohydrodynamic Modeling of Squeeze Film Dampers in High-Speed Turbomachinery

2018-04-07
Abstract This work develops a comprehensive thermohydrodynamic (THD) model for high-speed squeeze film dampers (SFDs) in the presence of lubricant inertia effects. Firstly, the generalized expression for Reynolds equation is developed. Additionally, in order to reduce the complexity of the hydrodynamic equations, an average radial viscosity is defined and integrated into the equations. Subsequently, an inertial correction to the pressure is incorporated by using a first-order perturbation technique to represent the effect of lubricant inertia on the hydrodynamic pressure distribution. Furthermore, a thermal model, including the energy equation, the Laplace heat conduction equations in the surrounding solids (i.e. the journal and the bush), and the thermal boundary conditions at the interfaces is constructed. Moreover, the system of partial differential hydrodynamic and thermal equations is simultaneously solved by using an iterative numerical algorithm.
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