Study on variable inertia torsional vibration of crankshaft based on instantaneous kinetic energy equivalence

Considering the variable inertia of the reciprocating parts, free torsional vibration characteristics of crankshaft are studied. Based on instantaneous kinetic energy equivalent principle, a kind of accurate calculating method of single-cylinder diesel engine's variable inertia is presented. Free torsional vibration differential equations of the single- and multi-cylinder diesel engine crankshaft systems are established, and torsional vibration characteristics of the system are also analyzed theoretically. Numerical calculation of the free vibration of a certain multi-cylinder diesel engine is completed. The results indicate that the introduction of variable inertia has a great effect on the torsional vibration characteristics, such as the free frequency, critical speed zone, and torsional vibration angular displacement, of the crankshaft system.