摘要
为准确捕捉小开度流动的瞬态湍流特性,充分了解流场结构,采用滑移网格技术以及基于Vreman亚格子模型的全局动态大涡模拟方法,不仅得到混流式水轮机全流道内速度、压力以及涡量的分布,同时捕捉到了活动导叶周围独特的流动形式和叶道涡的时空演化。计算结果表明:当高转速、小开度工况时,流道内流体的圆周速度占有绝对优势,加强了导叶后尾迹涡的相互影响,致使流道中发生更为剧烈和复杂的漩涡、脱流等各种水力不稳定现象。从蜗壳到转轮室的压力脉动均以低频为主,主要的频率能量成分基本相同,说明小开度低频异常振动与压力波的传递有关。叶道涡是致使叶片疲劳破坏的主要因素。
The large eddy simulation(LES) method base on a Vreman subgrid-scale model and the slide mesh technology of CFD were applied to accurately capture the flowing character in the Francis turbine passage under a small opening condition. Pressure distributions, velocity and vorticity as well as some special flow structures in guide vane near-wall zones and blade passages were gained. The results show that the tangential velocity component of fluid is dominant under a small opening condition. This situation aggravates the interactions between the wake vortices that shed from guide vanes. It leads to strong and complicated turbulent motion and all kinds of hydraulic instability phenomenon. There exists a pressure pulsation with a consistent low frequency, and main frequency energy in each flow passage parts from a spiral case to a runner computational domain, inducing the swirl vortex in a blade passage. Thusly, the non-uniform flow around a guide vane combined with thetransmission of stress wave has a critical influence on the balance of a turbine and blade unit. In addition, the inter-Blade vortex is the main factor of blade fatigue failure.
出处
《工程力学》
EI
CSCD
北大核心
2015年第6期222-230,共9页
Engineering Mechanics
基金
国家自然科学基金项目(51309128
51279071)
教育部高等学校博士学科点专项科研基金(优先发展领域)资助项目(20135314130002)
关键词
混流式水轮机
小开度流动
叶道涡
vreman亚格子模型
湍流特性
francis turbine
small opening flow
inter-blade vortex
vreman subgrid-scale model
turbulence characteristics
