导叶叶片数对LNG四级潜液泵轴向力及首级叶轮流场的影响研究

The Influence of Guide Vane Blade Number on the Pressure and Axial Force of the First Stage Impeller of LNG Four Stage Submersible Pump

应用CFD技术研究了导叶叶片数对LNG潜液泵首级叶轮压力和轴向力分布的影响,对一、三级导叶同时设计7、8、9三种叶片数,采用K-epsilon湍流模型进行了多工况数值模拟,并采用液氮工质进行了相关外特性试验验证,得到LNG泵内部首级叶轮压力分布以及轴向力特性。结果表明:潜液泵所受总轴向力在导叶数为8时最小,泵的整体效率最优。作用在首级叶轮上后盖板的轴向力大于前盖板。其中,导叶数为8时首级叶轮前后盖板轴向力最小,压力分布最均匀;而导叶数为9时,与叶轮叶片数9相同,运转时会有共同的倍频出现,在相同的倍频上振动累加,并诱发共振,导致前后盖板的轴向受力最大,叶轮前盖板所受轴向力相对于其他方案平均增加了3.45%;后盖板轴向受力绝对值平均增加1.88%。综上,导叶数为8时潜液泵的水力效率最优。

The influence of the number of guide vane blades on the pressure and axial force distribution of the first stage impeller of LNG submersible pump was studied by CFD technology.Three kinds of blade numbers of 7,8 and 9 were designed for the first and third stage guide vanes at the same time.The K-epsilon turbulence model was used to simulate the multi-condition numerical simulation,and the liquid nitrogen working fluid was used to verify the relevant external characteristics test.The pressure distribution and axial force characteristics of the first stage impeller inside the LNG pump were obtained.The results show that the total axial force of the submersible pump is the smallest when the number of guide vanes is 8,and the overall efficiency of the pump is the best.The axial force acting on the back cover plate on the first stage impeller is greater than that on the front cover plate.When the number of guide vanes is 8,the axial force of the front and rear cover plates of the first stage impeller is the smallest and the pressure distribution is the most uniform.When the number of guide vanes is 9 and the number of impeller blades is 9,there will be a common frequency doubling during operation.The vibration accumulates on the same frequency doubling and induces resonance,resulting in the maximum axial force of the front and rear cover plates.The axial force of the front cover plate of the impeller is increased by 3.45%on average compared with other schemes.The absolute value of the axial force of the rear cover plate increases by 1.88%on average.In summary,the hydraulic efficiency of the submersible pump is optimal when the number of guide vanes is 8.