Effect of rotating unbalance and engine excitations on the nonlinear dynamic response of turbocharger flexible rotor system supported on floating ring bearings

摘要

In practical conditions, turbochargers are supported by floating ring bearings and mounted on engines. In this paper, the effect of rotating unbalance and engine excitations on turbocharger is studied. The finite element model of turbocharger system is developed considering flexible rotor, using Timoshenko beam elements. The nonlinear fluid film forces generated in floating ring bearings are derived analytically in dimensional form using short bearing approximation. A new MATLAB (R)documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$hbox {MATLAB}^{{circledR }}$$end{document} code has been constructed to solve the governing differential equations of motion of system using implicit Newmark-betadocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$upbeta $$end{document} numerical integration scheme along with Newton-Raphson convergence method, and dynamic response of the system is computed. The orbital plots, Poincare maps, and frequency spectrum are developed to show the nonlinear behaviour of the turbocharger system. At low rotor speeds, the system exhibits chaotic behaviour and has a wide range of sub-synchronous vibrations. As the speed of turbocharger increases, the forces due to unbalance dominate over engine excitations and nonlinear bearing forces and frequency spectrum become narrow. The behaviour of compressor and turbine disc centre is governed by their respective bearing nodes.