湍流模型对轴流泵全工况计算精度的影响研究

Comparison of different turbulence models for simulating water flow in axial pump

【目的】研究湍流模型在轴流泵全工况的数值模拟过程中对计算精度的影响。【方法】采用Standardk-ε、RNG k-ε和SST k-ω3种湍流模型对轴流泵进行全工况的数值模拟计算,将计算结果和试验结果进行对比并结合内流场进行分析。【结果】在定常状态下,采用Standardk-ε、RNG k-ε、SST k-ω3种湍流模型计算的扬程曲线与试验曲线的趋势基本一致。在正转逆流制动工况中,采用Standardk-ε和SST k-ω湍流模型计算扬程的精度相近且高于RNG k-ε湍流模型的计算精度,相较于RNG k-ε湍流模型扬程计算最大误差减小了0.13m和0.22m,平均误差减小了0.55m和0.48m。在正转水泵小流量工况中,采用Standardk-ε湍流模型计算的扬程值最大误差和平均误差最小,计算精度相对于其他2种湍流模型显著提高,相较于RNG k-ε和SST k-ω湍流模型扬程计算最大误差减小了1.19m和0.96m,计算的平均误差减小了0.56m和0.68m。在反转顺流制动工况中,采用SST k-ω湍流模型计算扬程的精度更高,相较于Standardk-ε和RNGk-ε湍流模型扬程计算最大误差减小了1.08m和1.63m,计算的平均误差减小了0.6m和0.9m。在反转水泵工况中,采用Standardk-ε湍流模型计算的计算扬程的精度更高,相较于RNG k-ε和SST k-ω湍流模型扬程计算最大误差减小了0.65m和0.74m,计算的平均误差减小了0.34m和0.44m。在正转水泵大流量工况、正转顺流制动工况、正转和反转的水轮机工况中,数值模拟的内流场流态平顺,外特性计算结果较为接近试验值,精度较高,且3种湍流模型的外特性计算结果相互接近。【结论】在实际轴流泵数值模拟计算中,可以根据不同的运行工况选用计算效果更好的湍流模型来保证计算的结果精确度。研究成果为特殊运行工况的轴流泵的数值模拟计算提供了参考。

【Objective】Water flow in pumps is modeled using computational fluid dynamics(CFD).However,the impact of turbulence model on simulation accuracy remains unexplored.This study aims to address this gap.【Method】We simulated axial water flow in a pump using three turbulent models:the Standard k-ε,RNG k-εand SST k-ωmodels.We compared the simulated results with experimental results and analyzed the internal flow fields simulated by different turbulence models.【Result】At steady flow state,the head curves simulated by all three turbulence models were consistent with the experimental curves.Underforward and reverse flow braking conditions,the head calculated by the Standardk-εand SSTk-ωmodel was close to or slightlyhigher than that calculated bytheRNGk-εmodel.Compared to theRNGk-εmodel,the Standardk-εand SSTk-ωmodels reduced the maximum error of calculated head by 0.13 m and 0.22 m,and average error by 0.55 m and 0.48 m,respectively.Under low water flowcondition inthe forward pump,the maximum and average error of the calculated head by the standard k-εmodel were the least;compared to the RNGk-εand SSTk-ωmodel,it reduced the maximum error of the calculated head by 1.19 m and 0.96 m,and the average error by 0.56 m and 0.68 m,respectively.Underreverse downstream braking conditions,the SSTk-ωmodel was most accurate;compared tothe Standardk-εand RNGk-εmodel,it reduced the maximum errors of the calculated head by1.08 m and 1.63 m,and average errors by 0.6 m and 0.9 mrespectively.Underthe reverse pump condition,the Standardk-εwas most accurate;compared to the RNGk-εand SSTk-ωmodels,it reduced the maximum errors of the calculated head by 0.65 m and 0.74 m,and average errors by 0.34 m and 0.44 m,respectively.For other conditions,includingpositive rotating pump,positive rotating downstream braking,positive rotating and reverse rotating turbine,the simulatedinternal flow field in the pump wassmooth,the simulatedexternal characteristics wereclose to experimental observations,and simulated results of all three models were similar.【Conclusion】The accuracy of turbulence models for simulating axial water flow in pumps depends on operating conditions.Our results provide insights into selecting appropriate turbulence model for simulating water flow in pumps.