Transient modal analysis of the non-linear dynamics of a turbocharger on floating ring bearings

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Abstract
Floating ring bearings (FRBs) used to support turbochargers are well known to be highly non-linear elements that introduce self-excitation. The prediction of such vibration is of utmost importance to turbocharger designers. This article presents an original computational method for the non-linear dynamic analysis of a turbocharger on FRBs, which is used in a novel study of the self-excited vibration of a realistic turbocharger model. The proposed method is designed to overcome restrictions of current rotordynamic software packages relating to structural and bearing modelling and computational implementation. The equations of motion are formulated in modal space and integrated for the response. The program uses the modal parameters of the generic linear part of the structure, which can be pre-computed by using standard finite-element software. The non-linear computation of the full assembly is itself efficiently implemented on standard mathematical software. Both fully floating and semi-floating rings are considered in the simulations, and the findings of the simulations indicate that the latter configuration may lead to significant reduction of self-excited vibration.