大功率液力偶合器多流动耦合域气液两相瞬变流场演化机理及特性研究

Due to the excellent transmission performance and significant energy savings governor, hydrodynamic coupling is widely used in large-scale power plant equipment .With the increasing load power and speed, transient effects of flow field can lead to decrease capacity, reduce efficiency, instability of output characteristics, increase vibration of system and other issues when hydrodynamic coupling works in the dynamic matching speed. Present the study of internal flow field characteristic of hydrodynamic coupling is limited to steady conditions, but the evolution mechanism of field structure and instantaneous change of inside and outside properties are not clear under instantaneous conditions, especially internal causes and mechanisms of energy loss of transient flow field excitation vibration for high Reynolds numbers are lack of theoretical guidance, which limits the development and application of hydrodynamic speed control technology. This project researches calculation model of gas-liquid two phase transient flow field in multi-domain flow coupling field, traces changing of gas-liquid two-phase interface in multi-domain flow coupling field, analyzes structure transition mechanism of gas-liquid two-phase and its dynamic characteristic, discriminates phase interactions and structure transient energy evolution mechanism of flow characteristic between multi-scale turbulence vortex and bubble, grasps energy loss mechanisms and pressure pulsation properties caused by transient flow, reveals influence law of action between internal and external characteristics. The study will provide the necessary theoretical foundation for design and development of high-power hydrodynamic coupling

液力偶合器凭借其优良的传动性能和显著的调速节能水平在大型电站装备中有着广泛的应用。随着负载功率和转速的不断提高，液力偶合器在动态匹配调速工作中由于流场的瞬变效应导致能容下降、效率降低、输出特性失稳及系统振动加剧等问题。目前对液力偶合器内部流场特性研究局限于稳态工况，瞬态工况下流场结构的演变机理及内外特性瞬时变化尚不明确，尤其对高雷诺数条件下瞬变流场激发振动的内部成因及能量损失机理缺少理论指导，限制了液力调速技术的发展和应用。本项目研究多流动耦合域内气液两相瞬变流场计算模型，追踪多流动耦合域内的气-液两相界面，分析两相流型结构转变机理及其动力学特性，辨析多尺度湍涡与气泡的相间作用和流动特征结构瞬变耗能演化机理，阐明瞬变流动引发的能量损耗机制和流体激振成因，揭示内、外部特性之间的瞬态作用影响规律。本项目的研究将为高性能大功率液力偶合器设计和开发提供必要的理论基础。

大功率液力偶合器是大型核/火电站系统锅炉主给水泵重要的调速节能装备。随着负载功率和转速的不断提高，与常规工况相比较，其动态调速性能发生很大变化，出现能容下降、效率降低、输出特性失稳及系统振动加剧等问题，影响了系统的安全稳定运行。因此，本课题从大功率液力偶合器高雷诺数条件下气液两相瞬变流场研究入手，分析瞬态工况下流场结构的演变机理及内外特性瞬时变化对应关系，总结瞬变流动引发的能量损耗机理。.本课题首先搭建了一套液力偶合器两相流场可视化/外部特性同步测试组合试验平台。完成了液力偶合器内部气液两相流场可视化/外部特性同步测试试验和动态调速工况时域内/外特性的对应标定工作。基于数字图像处理技术，辨识和提取速度流动特征参数的演化信息，总结中低雷诺数下稳态工况和动态调速工况偶合器气液两相流场特性。在此基础上，建立以混合RANS/LES方法为基础的液力偶合器多流动域耦合气液两相瞬变流动高精度数值计算模型，采用UDF瞬态边界条件加载方法，实现对动态工况气液两相瞬变流场流动细节和外部特性的预测。以影响雷诺数的外部工况特征参数—泵轮输入转速为切入点，研究特征雷诺数对动态调速工况下偶合器瞬态流场的影响规律，实现了对大功率液力偶合器瞬态性能波动成因和主要影响因素的把握。针对大功率液力偶合器结构强度设计这一关键问题，以本课题数值计算模型得到的瞬态压力流场数据为载荷，建立了一套基于单相流固耦合算法的大功率液力偶合器叶轮装配体结构强度分析方法，实现了对典型工况下叶轮装配体结构强度的全面分析。在大功率液力偶合器结构基础上布置无内环的导轮创新性的提出一款新型液力变矩偶合器流道结构方案，应用本课题的数值计算方法预测并研究关键流道结构参数对其性能的影响规律，通过与试验结果的对比，验证了数值计算方法的有效性。.本课题的工作为高性能大功率液力偶合器及其它相似液力元件流道结构参数设计提供理论支撑。