高温熔盐泵转子系统应力与模态的数值模拟

Numerical simulation of stress and mode of rotor system of high-temperature molten-salt pump

为了提高太阳能光热发电系统高温多级熔盐泵的运行可靠性,基于流固热多场耦合理论系统对熔盐泵在极端高温工况下的结构应力进行研究,对比分析高温转子系统在无预应力和有预应力(流场、质量力和温度载荷)作用下的模态特征.研究结果表明:熔盐介质的密度和黏度对外特性影响较小,清水测试结果可作为高温熔盐泵运行性能的参考;随着叶轮级数增多,各级叶轮温度整体升高,且叶轮的温度变化呈中心对称分布,叶轮最高温度随流量减小整体上升;叶轮受到的主要应力来自流场与质量力载荷,且分布具有对称性;在叶片与盖板交线处有应力集中现象,在叶片尾缘处应力大幅上升至60.000 MPa以上;温度是引起叶轮变形的首要原因,随温度升高,叶轮变形量增大;转子结构的固有频率在有预应力下比无预应力时有较大程度提升,上升幅度为109%~498%,各阶振幅没有明显规律;熔盐泵临界转速值均偏离泵额定转速,避免了转子系统在运行中发生共振.研究结果可为高温熔盐泵设计开发提供一定的理论依据.

In order to improve the operational reliability of high-temperature multi-stage molten-salt pump of the solar thermal power system,the structural stress of molten-salt pump under extreme high temperature condition was analyzed systematically based on the fluid-solid-thermal multi-field coupling theory.The model characteristics of high-temperature rotor system under the action without and with prestress,which contained fluid pressure,inertial force and temperature load,were compared and analyzed respectively.The results show that the density and viscosity of molten-salt medium have little effect on the hydraulic characteristics,and the water test results can be used as a reference for the ope-ration performance of high temperature molten-salt.The temperature of the impellers rises with the increase of the impeller stages.The temperature change of the impeller is distributed symmetrically in the center.The maximum temperature of the impeller increases as the flow rate decreases.The main stress on the impeller comes from the fluid pressure and inertial force load,as well as the distribution is symmetrical.There is stress concentration at the intersection area of front and rear cover plate and blade.The stress at the trailing edge of the blade rises significantly to over 60.000 MPa.Temperature is the main factor of impeller deformation.Impeller deformation increases with temperature rise.The natural frequency of the rotor structure with prestress is higher than that without prestress,whose magnitude of the rise is 109%-498%,and the amplitude change of each step is not obvious.The critical speed of the molten-salt pump deviates from the rated speed of the pump,which avoids the resonance of the rotor system during operation.The research results can provide a theoretical basis for the design and development of high temperature molten-salt pump.