Theoretical and experimental evaluation of engine bearing performance

Abstract

Measurements of total engine bearing friction have been carried out on a single-cylinder gasoline engine under fired conditions. The bearing friction was measured indirectly by measuring the total engine friction, piston assembly friction, and valve train friction. Total engine friction was measured via pressure-volume (PV) diagram, whereas piston assembly friction measurement was carried out using the indicated mean effective pressure method. Valve train friction was measured using instrumented camshaft drive pulleys. All the engine auxiliaries were independently driven electrically. Engine bearing friction was measured under different engine operating conditions. The hydrodynamic lubrication regime occurred under most of the engine operating conditions, although at lower engine speeds and higher lubricant temperatures a transition from hydrodynamic to boundary/mix lubrication regime occurred. The effect of two different lubricants SAE 0W20 and SAE 5W30 on engine bearing performance was investigated. The adverse effects of viscous oil at low lubricant temperature were notable, as were the benefits at higher lubricant temperature. Predicted results from a number of engine bearing friction mathematical models have been compared with the experimental results. The comparative study showed that the results generated through the short bearing mobility method under cavitation conditions were close to the experimental data. This experimental system can be used to study bearing design parameters, bearing materials, lubricant chemistry, and engine operating conditions on the bearing performance under realistic conditions in its original environment.