The effect of engine run irregularity level on oil film over cylinder liner surface

At idle run the engine operates in extremely unfavourable conditions because of vibrations generated by cyclic forces which makes that oil film parameters on liner surface become critical as well. This paper presents one of the crankshaft vibrations results namely the speed that differs from a generally known dependence described with two harmonics rco sin less than p and 1/2Xrco sin2 less than p. Taking into consideration the deterioration of oil film - the thickness in particular - at low idle speed, a further speed decrease could cause the oil film rupture. This means that in the case of piston-cylinder assembly elements the process of abrasive wear occurs first of all at idle run. Avoiding such situations lead to a considerable extension of engine life. The minimum piston speed outside both dead centres could be increased by the rise in idle run speed. Unfortunately, this leads to an increase in fuel consumption, e.g. when waiting for a green light in urban traffic. The only way to improve the oil film parameters at idle run is to improve the engine speed irregularity level 8. Certain possibilities in this field are offered by the hybrid drive. This paper presents an introductory analysis of possible improvement in oil film parameters over cylinder liner achieved by the decrease in speed irregularity level 8.