Rotational dynamics of piston diesel engine crankshaft with deactivated cylinders at idle

Abstract

Diesel engines have been diagnosed on the basis of a dynamic method. To improve the informativity of the determination of general technical condition of each of the cylinders, it is proposed to apply a well-known test action i.e. termination of operation. In this case, analysis should be given to both the contribution of the cylinder in the operation and the acceleration imparted to the crankshaft by the cylinder in the absence of fuel supply. The paper presents a mathematical model that takes into account the relationship of the dynamics of rotation of the crankshaft with the pressure of gases in the cylinder, including when it is deactivated. The analysis of functional dependences has allowed to receive coupling equations between parameters of tightness of the cylinder and angular crankshaft acceleration. Analytical and experimental study of the crankshaft rotation dynamics with deactivated cylinders at idle speed allowed to conclude that parameters of the crankshaft rotation irregularity allow assessing the engine cylinders’ technical state both in the run mode and in the idle mode. The diagnostic parameter allows determining the leak tightness of the over-piston space at idle speed is suggested. It equals air pressure differential in the cylinder at 50 degrees before TDC and at 50 degrees after TDC over the pressure at 50 degrees before TDC. It was installed, that both extrema of angular accelerations and their average values during compression and expansion can be used to diagnose the technical condition of cylinders.