基于热流固耦合的LNG低温潜液泵转子部件模态分析

Modal analysis of rotor parts of LNG low temperature submersible pump based on thermo-fluid-structure coupling

利用UG对LNG潜液泵进行三维造型,再以ANSYS Workbench为平台,对LNG低温潜液泵的转子部件进行热流固耦合计算,得出流场对固体结构部分的热流固耦合力,把热流固耦合力作为预应力添加到转子部件上.分别对转子部件进行无预应力和有预应力作用下的模态分析,基于计算结果,提取了转子部件的前10阶模态,并把2种情况下的模态进行比较.结果表明:除了七阶、八阶振动为轴的摆动,其他各阶的振动变形都表现在叶轮上;添加预应力之后,转子部件的各阶振型没有发生变化,但每一阶的固有频率都有轻微的变化,预应力对转子部件各阶固有频率的影响很小;九阶和十阶的固有频率比较接近泵的3倍叶频,有发生共振的危险,需要对转子部件进行优化设计,使前3倍叶频都能远离各阶固有频率,从而避免泵在运行过程中发生共振;在预应力的作用下,转子部件的各阶振幅也都有小幅度的变化.

The LNG low temperature submersible pump was modeled by UG and the thermo-fluid-structure coupling of the rotor components were calculated by ANSYS Workbench.The thermodynamic coupling force of the flow field to the solid structure was obtained.The modes of the rotor components were analyzed with or without prestressing force.Based on the results,the first ten order modes were extracted and the modes in the two cases were compared.The results show that except for the seventh order and eighth order vibrations,the vibration of the other stages is expressed on the impeller.After the prestressing force is added,the various modes of the rotor component do not change.But the natural frequency of each order has a slight change,the prestressing force has little effect on the natural frequencies of the rotor components.The natural frequencies of the ninth and tenth order are close to the three times the blade frequency of the pump,so there is the danger of resonance.It is necessary to optimize the design of the rotor components so that the front three times the blade frequency can be far away from the natural frequencies of the various stages,thereby avoiding the resonance of the pump during operation.Under the influence of prestressing force,the amplitude of the rotor parts also has a small change.