轴承供气压力对静压气体轴承-转子系统动力学特性影响的实验

Experimental Research for Effects of Bearing Supply Gas Pressure on Aerostatic Bearing-rotor System Dynamic Characteristics

关键词:  静压气体轴承  轴承供气压力  临界转速  气膜涡动  气膜振荡

Key words:  Aerostatic bearing  Bearing gas supply pressure  Critical speed  Gas film whirl  Gas film whip

摘要:

为了研究轴承供气压力对气体轴承-转子系统动力学特性的影响，在静压气体轴承支承的压气机与透平同轴结构的涡轮膨胀制冷机试验台上，开展了相应的试验研究。采用分岔图、轴心轨迹、频谱分析等振动测试分析方法，分析了供气压力对临界转速和低频特性的影响。实验结果表明:轴承供气压力为0.80MPa，转子在26000r/min时未出现半速涡动；轴承供气压力为0.75MPa，转子在50000r/min时的低频振动幅值仅为工频振动幅值的5%，远小于相同转速时0.80MPa下的相对值(低频振动幅值与工频振动幅值的比值为34.89%)。因此，供气压力的增大带来气膜直接刚度的增加，能够消除气膜的半速涡动；供气压力的降低带来气膜阻尼比的增加，能够抑制气膜振荡的幅值。

Abstract:

In order to study the effects of bearing gas supply pressure on the dynamic characteristics of aerostatic bearing-rotor system，the corresponding experiments were carried out on the turbo-expander refrigerator test bed with the coaxial centrifugal compressor and a radial turbine rotor structure supported by aerostatic bearings. The effects of bearing supply pressure on the critical speed and low frequency characteristics were analyzed by vibration test and analysis methods including bifurcation diagrams，axis center tracks，and frequency spectrum characteristics. The results show that gas film half-speed whirl disappeared at 26000r/min when the bearing supply pressure was at 0.80MPa，and when the bearing supply pressure was at 0.75MPa，vibration amplitude of low frequency at 50000r/min only accounted for 5 percent of the corresponding operating frequency vibration amplitude，which was far smaller than the relative value (the ratio of low-frequency vibration amplitude and operating frequency vibration amplitude was 34.89 percent) at the same rotational speed for 0.80MPa bearing supply pressure. Consequently，gas film half-speed whirl is eliminated by the increase of bearing supply pressure，which brings the increase of gas film direct stiffness. The vibration amplitude of gas film whip is suppressed by the reduction of bearing supply pressure，which brings the decrease of gas film damping ratio.