Dynamics and vibrations of high-speed rotor bearing systems containing camshafts and crankshafts.

摘要

The main objective of this study is to develop accurate finite element models of high speed engine camshafts and crankshafts.;Based on rotordynamics concepts, three main subjects are studied: First, to get a more accurate analysis of high speed rotor bearing systems, the finite element models of a high speed rotating shaft, an unbalanced disk, and a fluid film journal bearing are developed. Second, a V-8 racing engine camshaft is modelled as an unbalanced multiple rotor bearing system, and dynamic behaviors are investigated. Experiments are performed to get the camshaft whirl motions at different speeds. Fatigue analyses are performed using the modified Goodmann's equation. Finally, for a crankshaft with wide webs, a specialized rotating web element is developed. The element includes the gyroscopic and shear effects. Eigenvalues are extracted to get the critical speeds, based on the Sturm sequence property and bisection technique.;The bending effect is found to be dominant in the camshaft. Thus, the weakest part of the camshaft is the mid area of the longest span. In the low speed range, the linearized constant bearing model works well. But, in the high speed range, the time varying nonlinear bearing coefficients should be used for analysis. The critical speeds or natural frequencies of the crankshaft can be classified by the in-plane and out-of-plane modes according to the geometry.