MODELING OF ENGINE OIL PRESSURE IN SLIDING BEARINGS OF INTERNAL COMBUSTION ENGINE MECHANISMS

Abstract

The results of analytical studies are presented, which allowed to obtain a mathematical expression for calculating the pressure of engine oil at the entrance to the sliding bearing depending on its geometric parameters and the performance of the oil pump of the engine lubrication system. The basis of the analytical studies is the well-known equations of flow continuity and the method of calculating its flow rate through the ends of the sliding bearing. Creating the necessary pressure of engine oil in the entrance chamber of the sliding bearing is necessary to ensure a significant amount of it in the gap, which causes a hydrodynamic effect at high speeds of rotation of the journal (crankshaft) and boundary lubrication of the surfaces when starting the engine. Modeling the influence of the parameters included in the obtained mathematical expression allowed to obtain graphical dependencies, which, according to the physics of the process, make it possible to analyze the pattern of changes in flow pressure at the entrance to the sliding bearing. The obtained results indicate, firstly, the reliability of the approximation of the pressure values, and secondly, the reproduction of the physical meaning of the modeled process – an increase in the diametrical gap causes an increase in oil flow rate, and as a consequence, a decrease in pressure. Comparison of the obtained calculated pressure value of oil p=0.14 MPa at the nominal gap and eccentricity with the operational documentation of cars regarding the technical characteristics of the engine indicated that the obtained value is within the regulated limits. The presented studies did not take into account the viscosity-temperature state of the engine oil, which certainly changes under different engine operating modes and will make appropriate adjustments to the obtained mathematical expression.