Modern requirements imposed in modern and actual agriculture-related goals of improve the technologically processes efficiency. Efficiency of specific work processes to agriculture is directly related to energy sources efficiency, energy sources used agricultural machinery and equipment. Importance is given by the contemporary massive growth of the degree of mechanization and automation of agricultural equipment. Energy sources (IC engines) efficiency is defined in general by the quality of transforming the fuels energy into useful heat energy and by the value of mechanical losses due to friction between the mechanisms relative moving. Using adequate lubrication oils can reduce friction losses. Rheological characteristics of lubricating oil directly influence the friction losses due to mechanical friction of IC engines internal mechanisms (piston group, valve train, fuel pump, crankshaft, bearings and seals etc.). The paper aims to determine by computer simulation process (numerical investigation) the influence of the different classes lubricating oils characteristics on lubricating process of the friction losses in valve train system. The friction losses due to camshaft bearing hydrodynamics, between cams and cam followers, due to oscillating valve train hydrodynamics and due to oscillating mixed valve train lubrication was considered. Valve train system has a poor lubrication during cold startup process of an IC diesel engine and thus is necessary a proper lubricating oil to full fit the complex demands of all engine components and subassemblies. The results were obtained according to consideration of constructive parameters and design particularities of tractor diesel engine D-110 type, and were compared with data obtained by experimental measurements. The difference between the total friction losses in valve train system using a SAE10 class lubricating oil and a SAE40 class lubricating oil is 0.16 kW(-7.3 %). Considering these results, is worth to note that if will use a higher SAE viscosity class (e.g. SAE40), is a greatly reduce the friction of the valve train system, but this may negatively influence the engine crankshaft lubrication. High viscosity oil poses to achieve a proper lubrication system, especially at low temperatures engine start process. There are different trends of variation of mechanical losses in components of valve train system for changing the SAE viscosity class of lubricating oil, trends that must be taken into account in the redesign and optimization of the valve train system components.

lubrication; oil; friction; losses; valve train; simulation.

Presentation: oral