液力偶合器非定常漩涡流场多尺度演化特征及能量损失机理研究

The performance of hydrodynamic coupling is determined by its internal flow characteristics.In order to improve the performance and design structure optimally, it is important to study its internal flow mechanism and understand internal flow characteristics deeply.Hydrodynamic coupling is full of disorder and multi-scale vortex flow under different conditions. The generation, evolution of multi-scale vortex flows and the interaction between them dominate the internal overall flow of hydrodynamic coupling. Flow field distribution and flow characteristics of full-filled hydrodynamic coupling are the object of study. Basic scientific research about multi-scale evolution characteristics of unsteady vortex flow field and mechanism of energy loss is carried on. The concrete contents include: New RANS/LES hybrid calculation method with physical constraint condition is researched, moreover, internal unsteady vortex flow field of hydrodynamic coupling is simulated by this new method;dynamic calibration algorithm of PIV measurement is developed and extraction methods of characteristic parameters in vortex flow field are studied; generating mechanism of unsteady vortex flow field and nonlinear evolution law of multi-scale vortices are analyzed; mechanism of energy loss is studied and the composition and distribution of energy loss is analyzed, basis on this, the methods and ways to reduce energy loss is given. This project is for the purpose of revealing internal flow mechanism of hydrodynamic coupling by PIV-CFD interactive research method. Futhermore,it will lay a theoretical foundations for the design and development of high performance hydrodynamic coupling.

液力偶合器的工作性能是由其内部流动特性所决定的，深入研究其内部流动机理及流动特性对于液力偶合器性能改进和结构优化设计极为重要。在不同工况下液力偶合器内部充满紊乱且多尺度的漩涡流动，多尺度漩涡流动的产生、演化以及彼此之间的相互作用支配着液力偶合器内部整体流动。本项目以液力偶合器满充液状态下流场结构分布和流动特性为研究对象，对非定常漩涡流场多尺度演化特征及能量损失机理进行基础科学研究。具体内容包括：研究带物理约束条件的新型RANS/LES混合计算方法模拟液力偶合器内部非定常漩涡流场；开发PIV测量动态标定算法并研究漩涡流场特征参数提取方法；分析非定常漩涡流场产生机理及多尺度涡旋非线性演化规律；研究能量损失机理并分析能量损失的组成及分布，探索实现能量损失降减的方法和途径。本项目旨在通过PIV-CFD交互式研究手段揭示液力偶合器内部流动机理，为高性能液力偶合器设计和开发奠定理论基础。

液力偶合器的工作性能是由其内部流动特性所决定的，深入研究其内部流动机理及流动特性对于液力偶合器性能改进和结构优化设计极为重要。在不同工况下，液力偶合器内部充满紊乱且多尺度的非定常漩涡流动，多尺度漩涡流动的产生、演化以及彼此之间的相互作用支配着液力偶合器内部整体流动。本项目通过理论研究、数值模拟和试验测量的交互式研究手段分析满充液状态下液力偶合器内部非定常漩涡流场多尺度演化特征，并揭示能量损失机理。在数值模拟方面，本项目研究并发展了新型RANS/LES 混合计算方法，并应用新的计算方法提高了液力偶合器内部漩涡流场数值模拟的计算精度。采用3种RANS/LES湍流模型及LES湍流模型仿真制动工况和牵引工况下液力偶合器内部漩涡流场，分析了非定常漩涡流场产生机理及多尺度涡旋非线性演化规律。在制动工况下，LES模型对主流区域多尺度漩涡流场结构仿真结果趋于真实；IDDES模型对叶片近壁面区域流速场仿真表现卓越，DES模型对叶片近壁面区域上涡量场仿真效果较好。在牵引工况下，DDES和IDDES模型仿真结果失真，DES模型针对主流区域漩涡流场结构细节仿真效果不佳，而LES模型仿真结果与PIV试验结果更吻合，能够体现沿圆周方向运动的多尺度涡旋之间的相互混合作用。在试验测量方面，设计并试制了适合流场试验的液力偶合器试验样机，搭建了液力偶合器流场可视化试验测量系统，基于该试验系统完成了多种工况下液力偶合器高分辨率漩涡流场图像采集，提出了漩涡流场图像特征识别与提取方法，依据提取的动态流场结构信息（流速场、涡量场）分析了液力偶合器内部漩涡流场结构演化规律及能量损失机理。为了实现液力偶合器漩涡流场高精度试验测量，研究了PIV流场试验测量环节中的主要误差来源，分析了示踪粒子选择、图像采集策略、流场图像标定和流速提取算法对流场测量与计算精度的影响，并提出降减和消除试验方面误差的途径与方法。本项目通过PIV-CFD交互式研究手段揭示了液力偶合器内部流动机理，为高性能液力偶合器设计和开发奠定了理论基础。