摘要:

AbstractThe effects of surface roughness on the static characteristics of finite porous journal bearings under hydrodynamic lubrication conditions are investigated in this paper. The well‐established Christensen stochastic theory of hydrodynamic lubrication of rough surfaces is used to incorporate the effects of surface roughness into the Reynolds equation. The analysis takes into account the flexibility of the porous liner by using a thin liner model. The effects of velocity slip at the surface of the porous medium are considered in the analysis by using the Beavers‐Joseph criterion. The mathematical model is then solved numerically by finite‐difference methods for mean hydrodynamic pressure, which in turn gives the hydrodynamic load. The effects of the surface roughness parameter, surface pattern, eccentricity ratio, length‐to‐diameter ratio, permeability parameter, and flexibility parameter on the hydrodynamic load‐carrying capacity, attitude angle, and friction factor ar

ISSN:0954-0075    

DOI:10.1002/ls.3010170402

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThis paper presents the results of an experimental investigation into the wear and lubrication characteristics of a diesel engine using ordinary coconut oil (COIL)‐blended fuels. The blended fuels consisted of 10, 20, 30, 40, and 50% COIL with diesel fuel (DF2). Pure DF2 was used for comparison purposes. The engine was operated with 50% throttle setting at a constant speed of 2000 rpm for a period of 100 h with each fuel. The same lubricating oil, equivalent to SAE 40, was used for all fuel systems. A multi‐element oil analyser was used to measure wear metals (Fe, Cr, Cu, Al, and Pb), contaminant elements (Si, B, and V), and additive elements (Zn, Ca, P, and Mg) in the used lubricating oil. Fourier transform infrared analysis was performed to measure the degradation products (soot, oxidation, nitration, and sulphation products) in the used lubricant. Karl Fischer (ASTM D 1744) and potentiometric titrations (ASTM D 2896) were used to measure water concentration and total base number (TBN), respectively. An automatic viscometer (ASTM D 445) was used to measure lubricant viscosity.The results show that wear metals and contaminant elements increase with an increasing amount of COIL in DF2. An increasing amount of COIL in the blends reduces additive elements, with the reduction for blends of up to 30% COIL being quite similar to that for DF2. Soot and sulphation decrease with increasing COIL in the blended fuels due to reduced aromatics and sulphur in comparison to DF2. The water concentration increases for blended fuels with more than 30% COIL. The TBN and viscosity changes are found to be almost normal. The engine did not appear to have any starting and combustion problems when operating with the COIL‐blended fuels. The lubricating oil analysis data from this study will help in the selection of tribological components and compatible lubricating oils for coconut oil‐ or biofuel‐operated diese

ISSN:0954-0075    

DOI:10.1002/ls.3010170403

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractTo investigate the performance of a traction‐drive toroidal continuously variable transmission, the traction characteristics under partial elastohydrodynamic lubrication contact were calculated theoretically based on roller test results. A calculation model was constructed for considering the effects of surface roughness on performance. The model incorporated a viscoelastic and elastic‐plastic model using a nonlinear Maxwell model to represent the rheological behaviour of the traction fluid. The validity of the model was confirmed by its good agreement with the experimental results described in Part 1 of this paper. Various calculations were made to investigate the effect of surface roughness on traction under the operating conditions of an actual traction drive. The results indicated that the effect of surface roughness on durability could not be igno

ISSN:0954-0075    

DOI:10.1002/ls.3010170404

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractOil‐soluble stannous oleate (SO) has been synthesised using oleic acid and SnO and its molecular structure confirmed. The tribological performances of SO and of complexes of SO with organosulphur or organophosphate compounds as lubricant additives in a VG26 white oil have been evaluated using a fourball friction and wear tester. The results show that SO exhibits good antiwear, load‐carrying, and friction‐reducing properties in the base stock, which are better than those of ZDDP. When 2.0% SO is added, the wear‐scar diameter reduced to 70% of that for the base stock alone, and the maximum non‐seizure load increased by 2.4 times. The friction coefficient was clearly reduced when SO was added. Synergistic effects were observed between SO and tricresol phosphate as regards the antiwear and load‐carrying properties, while a synergistic effect occurred only in terms of the antiwear properties for SO and a sulphurbased olefin. The elemental composition of the boundary lubricating film was examined by means of Auger electron spectroscopy (AES). The analytical results of AES indicate that the good performance of SO is attributable to the formation of a boundary lubricating film containing Sn on the rub

ISSN:0954-0075    

DOI:10.1002/ls.3010170405

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractSome rheological properties of mineral lubricating oils containing polyolefin (OCP) (ethylene/propylene copolymer) and poly(alkyl methacrylate) (PAMA) mixed additives over a wide composition range have been examined. Increasing the OCP content significantly increases the viscosity and shear stability of solutions, whereas the viscosity index is directly proportional to the PAMA content. The pour point values of the additive solutions investigated are lower than −30°C even for the smallest concentration of PAMA in the polymer mixture of 15 wt.% (at a total polymer mixture concentration in oil of 2 wt.%). The viscosities of dilute mixed additive solutions obey the typical Krigbaum‐Wall equation and, due to the negative viscometric interaction parameter values (Δb12<0), the OCP/PAMA mixture is found to be immiscible. The immiscibility becomes more pronounced on increasing the overall polymer concentrations. The viscosities of concentrated mixed additive solutions decrease significantly with an increase of OCP content, showing a minimum of half the initial value at a polymer ratio of about 50/50. On decreasing the polymer concentration to practical levels as well as increasing the temperature, the viscosity values approach the ideal additivity law. Based on the ratio of specific viscosities at 40 and 100°C (Q), the OCP additive solution shows a better thickening effect at lower temperatures (Q1) with more coherent thickening with temperature change. The mixed polymer additive, containing ∼10 wt.% OCP and ∼90 wt.% PAMA, is a nearly optimal viscosity‐index improver showing the same thickening effect at different temperatures. The results obtained are promising as regards the design of lubricant formulations with mixed polymer

ISSN:0954-0075    

DOI:10.1002/ls.3010170406

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractA four‐ball tester was used to evaluate the antiwear performance of cadmium dialkyldithiophosphate as an additive in mineral oil. The results indicate that it exhibits good antiwear properties and load‐carrying capacity. Surface analysis was performed to investigate the topography of test specimens and the presence and chemical states of elements such as sulphur, phosphorus, and cadmium and their compounds on rubbing surfaces. The tribological performance and antiwear mechanism of the additive are discussed, and a scheme for the formation of atomic cadmium is propo

ISSN:0954-0075    

DOI:10.1002/ls.3010170407

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010170401

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY