【作者】 李国栋；

【导师】 王洪杰； 魏显著；

【作者基本信息】 哈尔滨工业大学 ， 流体机械及工程， 2019， 硕士

【摘要】 太阳能、风能等可再生能源受环境影响显著,需要其他能源予以配合调节;此外,居民用电量的日变化规律呈现出典型的周期性,这些因素使得电网对于调节灵活的抽水蓄能机组的需求大大增加,水泵水轮机需要在不同工况下频繁切换。瞬态过程是水泵水轮机运行中为平衡电网负荷所必须经历的过程,特别是启停循环,其复杂的动态不稳定性严重制约了抽水蓄能机组的稳定运行。本文以水泵水轮机停机瞬态过程为研究载体,采用试验研究与数值模拟相结合的方式,探究了停机瞬态过程中的动态特性。为了获得更为真实可靠的流动特性,本文采用外部网格重构法模拟导叶闭合运动,给定试验测定压力作为进出口边界条件,基于转子角动量平衡方程计算更新转轮转速,从而构建了完整的瞬态过程三维数值模拟策略;同时基于上述方案,分别开展了考虑转轮间隙流动与否的水泵水轮机停机瞬态过程数值模拟。采用时域分析和时频分析(短时傅里叶变换等)对试验以及数值模拟获得的压力脉动进行对比分析,明确瞬态过程中压力脉动的复杂频率成分,分析其传播规律;通过分析流场、旋涡结构、涡量场等,探究停机瞬态过程中水泵水轮机内部特殊旋涡流动的演化历程;对比有无转轮间隙流动的停机瞬态过程外特性参数,采用压力脉动分析和内部流动分析相结合的方式探究间隙流动对于瞬态过程动态特性的影响。研究结果表明,本文所采用的三维数值模拟策略能够合理预测停机瞬态过程中的动态特性;在该过程中,双列叶栅流域涡结构存在着复杂的演化特征,随着导叶关闭,涡结构依次经历了依附于活动导叶腹部的马蹄涡和流向涡、反向液流冲击下的复杂破碎涡系、工况稳定后的存在于固定导叶的对涡等形式;相较于不考虑间隙流动,转轮间隙流动在有效降低轴向水推力的同时,破坏了附着在叶片下环边靠近进口处的流向涡,继而推迟了流向涡的生长、运动以至阻塞叶片流道的演化历程,从而造成转矩、流量等外特性参数存在0.7s左右的偏差;反水泵工况流动稳定后,间隙进口环面的径向速度分量锐减,对主流区流态破坏作用减弱,外特性参数偏差消失。更多还原

【Abstract】 Solar energy,wind energy and other renewable energy are significantly affected by the environment and need to be coordinated and adjusted by other energy sources.In addition,the daily variation law of residential electricity consumption presents a typical periodicity.These factors greatly increase the demand of the grid for the pumped storage units with flexible regulation,and the pump turbine needs to be switched frequently under different working conditions.Transient process is a necessary process to balance the power grid load in the operation of pump turbine,especially the start-stop cycle,whose complex dynamic instability seriously restricts the stable operation of pumped storage unit.In this paper,the transient process of pump-turbine shutdown is taken as the research carrier,and the dynamic characteristics of the transient process of pumpturbine shutdown are explored by combining experimental research with numerical simulation.In order to obtain more realistic and reliable flow characteristics,the external mesh reconstruction method is used to simulate the guide vane closing motion.The pressure is used as the inlet and outlet boundary condition for a given test.The rotor rotational momentum balance equation is used to calculate and update the rotational speed of the rotor.The complete three-dimensional numerical simulation strategy of transient process;based on the above scheme,the numerical simulation of the transient process of pump-turbine shutdown considering the flow of runner gap is carried out.Time domain analysis and time-frequency analysis(short-time Fourier transform,etc.)are used to compare the pressure pulsation obtained by experiments and numerical simulations to clarify the complex frequency components of pressure pulsation during transient process and analyze the propagation law.,vortex core distribution,vorticity field analysis,etc.,to explore the evolution history of special vortex flow inside the pump-turbine during the shutdown transient;compare the external characteristic parameters of the shutdown transient process with or without the runner gap flow,using pressure pulsation analysis and internal The combination of flow analysis explores the effect of gap flow on the dynamics of transient processes.The results show that the three-dimensional numerical simulation strategy used in this paper can reasonably predict the dynamic characteristics during the shutdown transient process.In this process,the double-row cascade vortex structure has complex evolution characteristics,with the guide vane closed,the vortex The structure successively undergoes the horseshoe vortex and the flow vortex attached to the abdomen of the movable guide vane,the complex crushing vortex system under the reverse liquid flow impact,and the vortex in the fixed guide vane after the working condition is stabilized;The gap flow,the runner gap flow effectively reduces the axial water thrust,destroys the flow vortex attached to the lower edge of the blade near the inlet,and then delays the growth and movement of the flow vortex,and even blocks the evolution of the blade flow path.As a result,the hysteresis of the external characteristic parameters such as torque and flow rate is 0.724 s.After the flow in the back pump condition is stabilized,the radial velocity component of the gap inlet ring surface is sharply reduced,and the flow damage to the mainstream region is weakened,and the hysteresis disappears.更多还原