无油涡轮增压器的设计及其试验研究

对采用空气箔片轴承支承的无油涡轮增压器进行了设计和试验性研究。详细阐述了无油涡轮增压器以及所采用的空气箔片轴承的设计过程。通过静态加载试验预估了空气箔片轴承的名义间隙，采用Link-Spring模型预测了空气箔片轴承支承结构的刚度，结合Link-Spring模型和雷诺方程，采用扰动法对轴承的动态刚度和阻尼系数进行了有效预测。线性转子动力学分析表明设计的无油涡轮增压器转子的前两阶刚体模态临界转速均在所用空气箔片轴承的起飞转速之下，转子的正常运行转速在一阶弯曲模态临界转速之下并具有足够的安全裕度。对整个转子系统进行了转子动力学分析与计算之后，在此基础上搭建了无油涡轮增压器试验台，初步的升降速试验结果表明：转子在20 kr/min~60 kr/min出现较大的次同步振动，但是转子在68 kr/min时次同步振动显著减小，转子在68 kr/min稳速时的轨迹以及FFT分析表明转子在该转速下的主要振动来自同步振动，这表明增压器可以在68 kr/min稳定运行。同时，实时测量了推力轴承和径向轴承的温度，在68 kr/min稳速期间，推力轴承和径向轴承温度分别在52℃和32℃处小幅波动，说明了该转子-轴承系统的相对稳定性。

Design and Experimental Research of the Oil-free Turbocharger

An oil-free turbocharger (TC) supported by the gas foil bearings (GFBs) is designed and an comprehensive experimental studies on the designed oil-free TC is presented.The detail design process of the oil-free TC is described. The nominal clearance is evaluated through the static load test. The structure stiffness of the GFB is predicted based on the Link-Spring model. The bearing dynamic stiffness and damping coefficients are predicted using the perturbation method by coupling the Link-Spring model and the Reynolds' equation. The linear rotordynamic analysis shows the first two rigid mode critical speeds are lower than the lift-off speed of the GFB. Moreover, the oil-free TC operating speed is much smaller than the first bending mode critical speed, which demonstrate the designed rotor have enough safety margin. The oil-free TC test rig is built based on the theoretical analysis of the design. The speed-up and coast-down results show that significant subsynchronous motion is occurred at 20 kr/min~60 kr/min, while the subsynchronous amplitude decreases significantly when the operating speed increases to 68 kr/min. The orbit and FFT analysis results when the rotor operates at 68 kr/min show the synchronous motion dominates the vibrations, which demonstrate the oil-free TC can operate stably at 68 kr/min. Meanwhile, the real-time temperature of the thrust GFB and journal GFB is recorded when the rotor operated at 68 kr/min. The temperature of the thrust GFB and journal GFB almost keep constant at 52℃ and 32℃, respectively, which demonstrate the stability of the designed rotor-bearing system.