基于POD/DMD降阶模型的离心泵蜗壳内非稳态流动分析

Analysis of unsteady flows in the volute casing of a centrifugal pump based on POD/DMD reduced order models

为深入研究离心泵蜗壳内非线性耦合流动的本质流动特征,本文以一单级单吸式离心泵蜗壳为研究对象,分别采用本征正交分解和动态模态分解2种降阶模型对蜗壳内非定常流场数据进行模态分析,获取流场主导流动结构,并对原流场进行重构。研究发现:蜗壳内流结构主要由速度正负交错,并且周期性特征与叶频及其倍频相关的成对涡旋组成。本征正交分解和动态模态分解方法均可以捕捉流场主要流动结构,并对原流场进行准确还原,两者重构流场与原流场的均方根误差均在0.4%以内。尽管本征正交分解方法在重构流场时整体均方根误差更小,但无法获取单频率流动结构,而动态模态分解方法可以获得不同频率流动结构对流场的贡献,从而捕捉到复杂流场中的不稳定模态。研究成果可以为增强离心泵全局流动的认知、关键水力部件优化设计及发展主/被动流动控制提供理论参考。

As the main component of centrifugal pump,the non-axisymmetric structure of volute casing has great influence on flow field and unit performance.Taking a single stage and single suction centrifugal pump volute casing as the research object,POD and DMD reduced order models were used to analyze the unsteady flow field in the volute casing based on the numerical calculation results,and the dominant flow structure was obtained,and the original flow field was reconstructed.It is found that the flow in the volute casing has obvious periodic characteristics,and the flow is mainly composed of paired vortices with interleaved velocity,and the dominant flow characteristics are related to the blade frequency and its frequency doubling.Both POD and DMD method can capture the main flow structure of the flow field and accurately restore the original flow field.The root mean square error of the reconstructed flow field and the original flow field is within 0.4%.In contrast,POD method cannot obtain single-frequency flow structures,while DMD method can observe the contribution of flow structures at different frequencies to the flow field,and can predict the flow field,with spatio-temporal coupling characteristics.The research results can provide theoretical reference for the analysis of complex coupled flow in centrifugal pumps and the optimization design of key hydraulic components.