Fluid friction in elastohydrodynamically lubricated (EHL) contacts depends strongly on the lubricant considered. Synthetic oils can have significantly lower fluid friction than mineral oils. Water-containing fluids have the potential to significantly reduce fluid friction further. The aim of this study is to investigate the film formation and frictional behavior of highly-loaded EHL contacts with water-containing fluids. Comparisons are made with mineral and polyalphaolefin oils. Measurements at an optical EHL tribometer show good lubricant film formation of the considered water-containing gear fluids. Measurements at a twin-disk test rig show coefficients of friction smaller than 0.01, which is referred to as superlubricity, for all considered operating conditions.

Different lubrication methods such as oil dip or injection lubrication are used in gearboxes to lubricate tribological contacts and to dissipate frictional heat. To improve resource and energy efficiency, novel needs-based lubrication methods like the drop-on-demand lubrication are being developed. It includes an ink-jet nozzle driven by a piezo element to generate picoliter droplets injected to tribological contacts. This study evaluates the feasibility of drop-on-demand lubrication of gears. Friction measurements in rolling-sliding contacts indicate the formation of typical elastohydrodynamic contacts. Power loss measurements of gears show a similar behavior compared to continuous minimum quantity lubrication. Hence, the study confirms that the operation of gears with drop-on-demand lubrication is possible. It introduces the possibility of dynamic and flexible oil supply on a contact needs-based level.

An experimental study has been conducted of the wall sprays produced afer impaction on a j a t surface by the pulsed sprayfrom a single hole nozzle. The experiments are of relevance to direct injection diesel engines and they extend the range of boundary conditions covered in previous work, with variation of gas density, spray wall angle, gas cross-Jlow velocity and cross-Jlow turbulence level. The initial and boundary conditions are documented to provide a database which is suitable for computational Puid dynamics (CFD) model validation of an important aspect of diesel engine in-chamber Jlow. Previous work in the area is described and published empirical correlations are reviewed. The measurements of wall spray penetration as a function of time are presented and described and a correlation equation is proposed whichJits the data with good accuracy.diesel engines, sprays, fuel injectors, wall impaction NOTATION gation of the characteristics of diesel fuel sprays. J . Mech. Engng SOC., Japan, 1980,15,57-64. Coghe, A. and Cossali, G. E. Experimental analysis of wall-spray structure by laser-Doppler techniques. Proc. ILASS-92, 1992, 97-103 (Shell, Amsterdam). 2~10, J. R. and Cbigier, N. Impinging diesel spray dynamics. Atomization and Sprays, 1991,1,303-318. Yule, A. J. and Awl, S. M. Cyclic variations in diesel sprays. Fuel J., 1 9 8 9 , s 1558-1564. Mum, M. R. Studies of diesel sprays with cross-flows and solid boundaries. PhD thesis, sprays produced by a diesel injector: further details of spray structure. To be submitted to Roc. Instn Mech. Engrs, Part D.