离心泵内部流动不稳定机理及其控制策略研究

Centrifugal pump is of vital importance in aerospace, nuclear power, and petrochemical industries, etc. Unstable operation of the device is the main problem affecting its industrial application. The main reason is the emergence of various unstable flow structures in pumps such as vortices, secondary flows and separations. However, so far researches in these fields are not sufficient in China and overseas. Some key scientific problems need to be resolved, which include the accurate numerical solution of the full flow field under small flow rate condition, the characterization of instability of internal flow, and the relationship between the internal flow instability and the unstable external performance of pumps. .The project is based on the background of centrifugal pumps used in aerospace engines and petroleum chemical industries. The purpose is to carry out systematic and in-depth study on the internal flow instability of centrifugal pumps from theoretical analysis, numerical simulation and experiments; to construct the dynamic subgrid stress model for large eddy simulation based on the Reynolds stress constraints and Lagrange track average; to carry out numerical solution of the entire flow field of centrifugal pump in the whole flow range; to establish parametric characterization and criterion of flow instability of internal flow based on the energy gradient function; to determine the mapping relationship between unstable external characteristics and internal flow instability; to further reveal the mechanism of internal flow instability and decide the control strategy; to provide technical support for improving the design theory of high performance centrifugal pumps. Therefore, this project would lay theoretical foundation for the design and development of high-end centrifugal pump unit and reliable operation of devices in China, and provide technical reserves for the design method of rotary fluid machinery.

离心泵在航天、核电、石油化工等领域至关重要，运行不稳定是影响其设计应用的最主要难题，其主要原因是内部流动中出现旋涡、分离和二次流等不稳定流动结构所致。但目前国内外研究不够充分，小流量工况下全流场数值精确求解、内部流动不稳定表征及其与外特性不稳定的关联等关键科学问题未能有效解决。.项目以航天发动机和石油化工流程离心泵为研究背景，从理论分析、数值模拟和物理实验等方面对离心泵内部流动不稳定及控制策略开展系统深入的研究，构建基于雷诺应力约束和拉格朗日轨迹平均的动态亚格子应力模式，开展离心泵全工况全流场大涡模拟计算，建立基于能量梯度函数的内部流动不稳定参数化表征和判断准则，确定外特性不稳定与内部流动不稳定之间的映射关系，从而揭示离心泵内部流动不稳定机理并确定控制策略，为完善高性能离心泵设计理论提供技术支撑，为我国高端离心泵机组设计开发和可靠运行奠定理论基础，为丰富旋转流体机械设计方法提供技术储备。

离心泵在航天、核电、石油化工等领域至关重要，运行不稳定是影响其设计应用的最主要难题，其主要原因是内部流动中出现旋涡、分离和二次流等不稳定流动结构所致。但目前国内外研究不够充分，小流量工况下全流场数值精确求解、内部流动不稳定表征及其与外特性不稳定的关联等关键科学问题未能有效解决。.项目围绕离心泵内瞬态旋转湍流的LES模型构建及数值计算、离心泵内部流动不稳定参数化表征及预判、离心泵外特性不稳定及其控制策略研究开展了深入研究。在复杂流动的湍流模型构建方面，通过引入螺旋度约束构建非线性亚格子模型，通过引入动态系数完成PANS方法的修正，以及针对RANS湍流模型进行旋转曲率修正，最终完成了离心泵内部适用模型构建。其次在离心泵内部流动不稳定参数化表征及预判研究方面，完成了适用于离心泵的能量梯度公式推导，并将其用于离心泵内部不稳定流动表征；基于熵产分析方法进行了离心泵内外特性的关联研究，并揭示了离心泵进口不稳定流动的产生演化机理，及其对离心泵不稳定的影响；基于涡变化率与拉格朗日拟序结构完成翼型和离心泵的不稳定流动分析；同时还基于全局敏感性方法完成对复杂钝体系统绕流的稳定性分析。最后在离心泵内外特性关联机理方面，描述了离心泵的能量损失及其与内外特性的关联关系，揭示了能量损失和不稳定流动结构与叶片载荷分布的关系，基于欧拉扬程分布提出了叶轮“极限外径”的概念，发现欧拉扬程的最大值（即极限外径）与顺时针旋涡中心的径向位置一致，并随流量的减小向叶轮进口移动，最终基于叶片载荷分布对叶片边界涡量流的正负峰值区进行了几何优化，极大改善了小流量区的流动分离，并提高了全流量范围的水力效率。.研究成果完善了高性能离心泵设计理论，现已用于航空发动机离心泵和多款流程离心泵的性能预测和设计开发中，取得良好效果，极大提高效率，降低实验和生产成本。