弹性箔片动压径向气体轴承动特性的实验研究

Experimental Study on Dynamic Performance of Compliant Aerodynamic Foil Journal Air Bearings

建立了新型弹性箔片动压气体轴承性能测试实验台,在静载60 N、转速9 000 r/m in条件下进行轴承性能测试试验,通过中心插值法获得轴承中心的扰动速度和加速度,采用时域最小二乘法计算不同激振频率下的8个轴承动态线性刚度和阻尼系数,考察了激振频率对轴承动特性系数的影响.结果表明:轴颈中心扰动轨迹为椭圆形且振幅随动态激振频率增加而增大;刚度和阻尼系数的直接项随动态激振频率增加而减小;交叉刚度和阻尼相对激振频率的变化较小,且其值小于直接项;当激振频率与轴颈转动频率相同时,工频成分的影响较大,轴心扰动幅值明显增大,刚度和阻尼的直接项小于其它频率时的值.

A test rig was built to study the performances of new compliant aerodynamic foil journal air bearings. This paper introduced an experimental method to identify eight linear dynamic coefficients of the foil gas bearings under different excitation frequencies. The experiment was performed when the static load and the rotating speed were 60 N and 9 000 rpm, respectively. The disturbed speed and acceleration of the journal center were obtained by the method of center difference of its displacement. In time domain, the linear stiffness and damping coefficients of each excitation frequency were calculated by means of least mean square. Finally, the effect of the excitation frequency on the dynamic characteristics of the bearing was investigated. Experimental results show that the vibration orbit of the journal center is elliptic. And with the excitation frequency increasing, the perturbation amplitudes of the journal center increase, but the direct terms of the stiffness and damping coefficients of the bearing decrease. The cross-coupling terms change little with the changes of dynamic excitation frequency, and their values are much smaller than those of the direct terms. When the excitation frequency is equal to the working frequency of the rotor, because of the effect of the components of the working frequency, the perturbation amplitude of the journal center increase significantly and the direct terms of the stiffness and damping coefficients are much smaller than those of other excitation frequencies.