Dynamic stability of unbalance-induced vibration in a turbocharger rotor-bearing system with the nonlinear effect of thermal turbulent lubricating fluid film. (23rd June 2022)

• Record Type: Journal Article
• Authors: Zhang, Yi; Wang, Wei; Wei, Daogao; Wang, Gang; Xu, Jimin; Liu, Kun
• Is Part Of: Journal of sound and vibration. Volume 528(2022)
• Publication Date: 2022-06-23
• Subjects: Turbocharger rotor -- Floating ring bearing -- Lubrication calculation -- Nonlinear vibration -- Oil whirl/whip; Sound -- Periodicals; Vibration -- Periodicals; Son -- Périodiques; Vibration -- Périodiques; Sound; Vibration; Periodicals; Electronic journals; 620.205
• DOI: 10.1016/j.jsv.2022.116909
• Languages: English
• ISSNs: 0022-460X

Abstract

Highlights: A calculation method for the thermal turbulent fluid-film pressure in the FRB is proposed. A transient tribo-dynamic model for the turbocharger rotor-FRB system is developed. A combined numerical analysis of lubrication with nonlinear dynamics is presented. A proper unbalance provides a stable region of synchronous vibration in medium-high speeds. By adjusting the unbalance and bearing clearance, the stable region transfers to different speeds. Abstract: The rotor-bearing system of small size and light weight used in automotive turbochargers can reach the speeds between 100, 000 to 300, 000 rpm, but the undesirable sub-synchronous whirl, whip, bifurcation and chaos probably appear in the response of self-excited unbalance and unsteady fluid-film forces with the high shear rate and low viscosity lubricant. From the perspective of coupling tribology and dynamics, the transient acting pressures in the double fluid-film lubricated bearing are computed by employing the turbulent lubrication theory and finite difference method at various high temperature conditions. Then a nonlinear dynamic model for the floating-ring bearing supported turbocharger rotor is developed through D'Alembert's principle and transfer matrix method in this paper. Comparative analysis of the trajectory, Poincare mapping, frequency-domain response and bifurcation behavior are conducted to investigate how to avoid fluid-induced instabilities via the rotor unbalance effect. The results show that an increase in unbalance can effectively suppress the sub-synchronous oil whirl at relatively low rotor speeds. At high speeds, the effect can also prevent the rotor from entering chaos by the path of quasi-periodic bifurcation, but an excessive unbalance will induce oil whip accompanied by frequency locking. A stable "interval region" of medium-high speeds characterized by the synchronous single-period small-amplitude vibration emerges only with the proper unbalance, which is available to guarantee the healthy operation of a turbocharger rotor.