高比转数双蜗壳混流泵设计及流动特性分析

针对目前比转数超过500的蜗壳混流泵研究较少,该文基于理论分析、CFD技术和模型试验的研究方法,以某高比转数混流泵的叶轮与蜗壳在设计工况下的良好匹配为目标,利用速度系数法对蜗壳结构进行优化设计,设计了一台比转数为585的高比转数双蜗壳混流泵,并对优化后的高比转数双蜗壳混流泵的内部流动特性进行了分析。将外特性试验数据与数值计算结果作对比,验证了该文数值计算模型与方法的准确性。研究结果表明,双蜗壳方案下水泵在偏离设计工况下的效率明显高于单蜗壳方案;双蜗壳结构混流泵的径向力在相同工况下比单蜗壳结构的径向力低,双蜗壳结构在保持原有水力性能的基础上还可以起到减小径向力的作用;不同工况下双蜗壳混流泵叶轮径向力矢量轨迹图分布呈类似正方形的封闭区间分布,径向力合力随时域呈现周期性变化,每个转动周期内有4个波峰和波谷;设计工况下的瞬态径向力合力最小,而小流量工况下的瞬态径向力合力最大且最不稳定,说明当双蜗壳混流泵长期运行在小流量工况下会增加安全事故隐患。研究成果为高比转数双蜗壳混流泵的设计以及内部流动特性研究提供了参考。

Design and internal flow field analysis of high specific mixed-flow pump with double volutes

Global energy issues affect the economic development, it is the base of improving national standard of living conditions. According to incomplete statistics, power consumption of pumps account approximately 17%of total generating capacity. Thereby increasing the efficiency of the pump is necessary to energy conservation which also has a very important significance on creating a resource-saving society. Mixed-flow pumps are more and more widely applied to industrial and agricultural production, the requirement of the performance of the mixed-flow pump become increasingly high. When the working condition deviates from the designed condition, the flow filed at impeller outlet does not match well with the flow field at volute inlet, which will lead to the efficiency drop of mixed-flow pump. Reasonable design of mixed-flow pump impeller and volute can improve the distribution of flow field, and then improve the hydraulic performance of the mixed-flow pump. Based on theoretical analysis, numerical simulation and model experiment research methods, impeller and volute matching optimization of high specific mixed-flow pump with volute were conducted. This paper developed a high-performance mixed-flow pump model with double volutes whose ns equals to 585 with the target of perfect match between impeller and volute under different flow rate conditions. The full three-dimensional numerical calculation internal flow field and radial force of the optimal designed high specific speed mixed-flow pump with double volutes was investigated. Numerical simulation of the pump used the standardκ-εturbulence model. Theκ-εturbulence model was considered to be a model which can predict the hydraulic performance and simulate the internal flow field accurately. The calculation domain contains inlet pipe, runner, volute, outlet pipe. And the mesh of inlet pipe and outlet pipe adopted unstructured mesh, the mesh of runner and volute adopted unstructured mesh. The results of numerical simulation were in agreement with the experimental ones, which indicated that the numerical simulation model and the calculation methods could be used to predict the internal-flow in a double volutes mixed-flow pump. The results showed that: the high efficiency area in the double-volutes pump was significantly broadened compared with the single-volute pump. And the internal flow streamline was very smooth at working condition in the double volutes mixed-flow pump. The pressure distribution in the double volutes pump revealed a increasing trend from impeller inlet from inlet outlet, which could make the impeller do work to the fluid effectively. the efficiency of double-volutes pump at designed flow rate was higher than the single-volute pump; the radial force in the double-volute pump was also smaller than the single-volute pump, which indicated that the double-volutes program not only keeped superior hydraulic performance but also could significantly reduce the radial force in comparison with the single-volute program; The radial force vector trail always presented a square distribution and the radial force fluctuation was always regularly, which contains 4 crests and 4 troughs in one rotating period. The conclusion in this paper had reference value for the design and study of internal flow in the mixed-flow pump.