潜水泵缩比模型的相似性验证与内部流场分析

相似换算设计法是离心泵设计中最常用的方法之一。为了验证缩比模型的相似性,该文选取一典型井用潜水泵作为模型泵,基于缩比模型换算法获得设计泵,借助数值模拟与性能试验的方法,研究设计泵与模型泵的相似性,并分析两者内部流场的差异与规律。采用Ansys CFX软件分别对设计泵和模型泵进行数值模拟,以两级泵模型建立计算域,划分结构化网格,基于标准k-?湍流模型和标准壁面函数进行多工况数值模拟,分别对设计泵和模型泵进行了性能预测,并对预测结果进行了对比分析。结果表明:较于模型泵,设计泵的最大功率点向大流量工况偏移,且最大功率与额定功率的比值有所上升,但其仍具有较好的无过载特性。模型泵数值预测与试验结果的对比表明,在额定流量下,数值模拟预测的扬程低于试验结果 0.79%,功率低于试验值5.2%,效率高于试验值2.78%,且两者随流量变化的趋势基本一致,说明该文的数值计算结果具有一定的准确性。缩比模型在0.4~1.6倍额定流量工况范围内,扬程、效率和功率随流量变化趋势基本一致,设计泵与模型泵满足相似换算准则,模型等比例缩放法能够满足深井离心泵的水力设计要求。

Verification of comparability and analysis of inner flow fields on scaling models of submersible well pump

Similar transformation design method is one of the most frequently-used ways of centrifugal pump design.In order to verify the similarity of the scaling model,a typical submersible well pump was chosen as the model pump in this paper,and based on the scaling model conversion algorithm,the designed pump was obtained.And the designed pump model was directly scaled without any factor correction by the model pump with a scaling factor of 0.66.By the numerical simulation and the experiments,both the comparability between the model pump and the designed pump and the difference between their inner flow fields were analyzed.Ansys CFX software was adopted to simulate the flow fields of the designed pump and the model pump.The calculation domains were created based on two-stage pump models,which were meshed with the structured grids.The numerical simulations under multi-conditions were performed based on standard k-ω turbulence and standard wall function.Also,different number of grids were divided both for the model pump and the designed pump in this paper to determine the unrelated relationship between the number of meshes used in the calculation and the calculated results.The flow filed of liquid in the main flow passage were analyzed emphatically.The streamline on blade to blade surface and the turbulent kinetic energy distributions on middle section of the impeller were analyzed to get the flow state and the hydraulic loss inside the impellers for both the model pump and the designed pump.In the meantime,the static pressure distributions and the vortex core region inside the diffusers were investigated.By the comparative analysis between performance predicted,it was found that the designed pump and the model pump had basically consistent variation tendency of their head,efficiency and shaft power under 0.4-1.6 times rated flow conditions,Which meant the performance predicted meet the similar conversion rules.The designed pump and the model pump both have wide high efficiency area,and the highest efficiency points are both at 1.2 times rated flow rate condition.Compared to the model pump,the maximum shaft power point of designed pump shifted to the heavy flow rate conditions,and the ratio of maximum power and the rated power increased.But the designed pump still has better performance of non-overload.The streamline on blade to blade surface and the turbulent kinetic energy distributions on middle section of the impellers showed that the fluid flow field and the vortex area inside the impeller were consistent.Also,the static pressure distributions and the vortex core region inside the diffusers showed that the pressure distributions inside the diffusers were similar,but the vortex core area inside the designed pump was smaller than the model pump.So,the liquid inside the designed pump had a good internal flow state,which would make the designed pump having a hydraulic efficiency.By the comparison between results of numerical calculation and experiment of model pump,the head and power of numerical simulation predicted were slightly lower than the test results,the predicted efficiency was slightly higher than the test results,but the changing trend were almost the same.The results of this study could provide a basis and reference for the improvement of submersible well pump performance.As we can see,the designed pump narrowed by the model pump had good hydraulic performance,which meant that the model direct scaling method can meet the design requirements of deep well centrifugal pumps.