Analytical Studies on Influence of Crankshaft Vibrations on Engine Noise Using Integrated Parametric Finite Element Model: Quick Assessment Tool 1999-01-1769

Torsional and lateral bending vibrations of cylinder block have a large effect on engine noise. Cylinder block vibration not only causes noise to radiate from the cylinder block itself but it is also the major exciting force to the oil pan and timing belt cover.

In order to reduce engine noise, it is important to completely understand the mechanism of cylinder block vibrations. An analysis is conducted using FEM and BEM to compute the influence of crankshaft torsional vibrations on cylinder block vibrations. A crankshaft system for a four cylinder automobile engine was used for analysis. Finite Element model of crankshaft is created using parametric modelling software developed based on ANSYS FEA software. Finite Element model of cylinder block, bearing cap, oil sump is also created using another parametric software developed based on ANSYS FEA software. Both the models are assembled and oil film is simulated at the journal bearings using spring-damper elements with appropriate values for stiffness and damping.

Dynamic analysis presented here focuses on the influence of crankshaft mode shapes on the excitation behaviour in the engine structure under crankshaft resonance conditions.

The influence of the mass and moments of inertia of the front pulley on crankshaft vibrations is studied. Results obtained so far match with the published data available on the subject experimentally. The paper focuses on the parametric tool developed for quick assessment of noise character of the combination of engine block, crankcase, oil sump and crankcase.