高速涡轮增压器轴承-转子系统不平衡响应及稳定性分析

汽车涡轮增压器广泛采用浮环轴承支承的小型轻质转子系统，以实现100 000~300 000 r/min的工作转速，提高发动机功率和动力性能，并降低燃油消耗和排放. 在此超高速工况下，动压油膜的强非线性作用和转子固有的不平衡效应使该系统呈现出复杂的动力学现象，其中油膜涡动、振荡、跳跃、倍周期分岔和混沌等非线性动力学行为对增压器的健康运转意义重大，因而备受关注. 本文作者从摩擦学动力学耦合的角度出发，基于流体动压轴承润滑理论和有限差分法计算非稳态油膜压力，结合达朗贝尔原理和传递矩阵法建立了转子离散化动力学方程，提出了一种由双油膜浮环支承的涡轮增压器转子系统动力学模型，并从转子轨迹、轴承偏心率、频谱响应、庞加莱映射和分岔特性等方面比较分析，描述了该非线性轴承-转子系统的不平衡效应及油膜失稳特征. 结果表明：转子一般在相对低速下作稳定的单周期不平衡振动，在高转速下其被油膜失稳引起的次同步涡动所抑制，但不平衡量的增加可阻碍转子以拟周期运动通向混沌运动的路径；适当不平衡补偿下，由于内、外油膜间交互的非线性刚度和阻尼作用，在油膜失稳区间之间的中高速区会出现适合增压器健康运转的稳定区间.

Automotive turbochargers widely adopt small lightweight rotor systems supported by floating ring bearings to achieve operating speeds ranging from 100,000 to 300,000 r/min, thereby improving engine power and dynamic performance while reducing fuel consumption and emissions. Under such ultra-high-speed operating conditions, the strong nonlinear effects of the hydrodynamic oil film and the inherent unbalance effect of the rotor give rise to complex dynamic phenomena in this system. Nonlinear dynamic behaviors such as oil film whirl, oscillation, jump, period-doubling bifurcation, and chaos are of great significance to the healthy operation of turbochargers, thus attracting widespread attention. From the perspective of tribological-dynamic coupling, the authors of this paper establish the discretized dynamic equations of the rotor based on the lubrication theory of hydrodynamic bearings and the finite difference method for calculating unsteady oil film pressure, combined with d'Alembert's principle and the transfer matrix method. They propose a dynamic model of the turbocharger rotor system supported by double oil-film floating rings, and conduct a comparative analysis from aspects including rotor trajectory, bearing eccentricity ratio, spectral response, Poincaré map, and bifurcation characteristics to describe the unbalance effect and oil film instability characteristics of this nonlinear bearing-rotor system. The results show that the rotor generally performs stable single-period unbalance vibration at relatively low speeds, and is suppressed by subsynchronous whirl induced by oil film instability at high speeds. However, an increase in unbalance amount can hinder the path from quasi-periodic motion to chaotic motion. Under appropriate unbalance compensation, due to the nonlinear stiffness and damping effects of the interaction between the inner and outer oil films, stable operating regions suitable for the healthy operation of turbochargers appear in the medium-high speed range between the oil film instability intervals.