为了减小轴向的热传递,应用于超流氦低温制冷系统的冷压缩机转子采用局部中空薄壁的结构型式.为保证该转子系统在高速运行时的稳定性,利用有限元分析软件 ANSYS对某中空薄壁结构型式冷压缩机转子进行模态以及不平衡响应分析,同时探讨了所采用的电磁轴承的刚度与阻尼比对转子动态特性的影响.结果表明,与一般实心结构转子相比,采用局部中空薄壁结构的冷压缩机转子低阶刚性临界转速及其峰值振幅几乎相同;但高阶弯曲型临界转速大幅下降,峰值振幅大幅提高,同时大幅振动所对应的频域更宽;并且对于叶轮端的平衡品质等级和不平衡量位置尤其敏感.采用的中空薄壁转子在一定的电磁轴承的刚度与阻尼比范围内可以实现所要求的动态特性.%To decrease the heat transfer in axial direction, the local hollow thin-walled structure was used in the rotor of cold compressor which was applied in super fluid helium cryogenic refrigeration system.In order to ensure the stability of rotor system at high speed, the modal and unbalance response analysis on this type of rotor were completed by Ansys which was based on the finite element method.Furthermore, the influence of the stiffness and damping ratio of the electromagnetic bearing on the dynamic characteristics of the rotor was discussed.The results showed that, compared with the general solid structure rotor, the cold compressor rotor with local hollow thin-walled structure have nearly same low-order rigid critical speed and vibration amplitude; however, the high-order bending critical speed decreases significantly while the vibration amplitude of the impeller increases significantly and what's more frequency domain of the large amplitude vibration is wider.Furthermore, it is especially sensitive to the grade and location of mass unbalance on the impeller.Thus, the dynamic characteristics analysis of the local hollow thin-walled rotor provides important reference significance for the design of rotor used in cryogenic rotating machinery which may need axial heat insulation, such as cold compressor.The designed local hollow thin-walled rotor could achieve requested dynamic characteristics in a certain electromagnetic bearing stiffness and damping ratio range.
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