FLNG多级液力透平转子临界转速的计算与分析

Calculation and Analysis of Rotor's Critical Rotational Speed of FLNG Multi-stage Hydraulic Turbine

为了研究9级FLNG液力透平转子在运行过程中的可靠性,基于ANSYS有限元仿真平台,采用模态分析方法对液力透平转子进行"干态"和"湿态"条件下数值模拟,并分析了轴承刚度、密封环间隙刚度和电机间隙刚度对转子系统的一阶临界转速的影响。结果表明,在"干态"刚性支撑条件下,转子各阶临界转速均大于相应的弹性支撑下的临界转速。"干态"和"湿态"条件下,转子的一阶临界转速分别为9 170r/min和21 179r/min,均超过工作转速2 965r/min,并留有不低于20%的安全裕度,表明所设计的9级FLNG液力透平转子在"干态"和"湿态"条件下均满足实际工程中结构动力学设计要求。此外,即使转子在实际运行过程中发生磨损,密封间隙增大至8倍设计值0.16mm,转子一阶临界转速仍远高于工作转速,不会影响安全运行。

In order to study the stability of the 9-stage FLNG hydraulic turbine’s rotor in the actual operating environment,this paper uses the modal analysis method to simulate the rotor in"dry"and"wet"conditions based on the ANSYS simulation platform.Based on the simulation results,the 4 natural frequencies and the corresponding vibration model diagram are obtained.Besides,the influencing effects of the bearing stiffness,the clearance stiffness and the stator-rotor clearance stiffness to the first-order critical rotational speed are analyzed.The results show that the critical rotational speed under the"dry"rigid support is higher than that under the"dry"elastic support.The first-order critical rotational speed under"dry"and"wet"conditions is respectively9 170 r/min and 21 179 r/min,which are both higher than that under the working environment and have a safety margin bigger than 20%.It is shown that the 9-stage FLNG hydraulic turbine’s rotor satisfies the structural dynamic design requirements under the both"dry"and"wet"conditions.Moreover,even if the sealing clearance is increased to 0.16 mm(8 times the design value)due to the abrasion in the actual operation progress,the first-order critical rotational speed is still well above the working rotational speed.It will not affect the safety of the FLNG hydraulic turbine’s operation.