摘要
开敞式进水池是中小型泵站中重要的水工建筑,其在结构尺寸设计不合理时易出现空气吸入涡(air-en-trained vortex,简称吸气涡),严重时会发生空蚀,从而严重影响泵站安全稳定运行。在开敞式进水池中,喇叭口悬空高度C对进水池流动影响较大。本文根据泵站设计规范中给定的悬空高取值范围,采用简化的耦合水平集与流体体积方法(simple coupled level-set and volume-of-fluid method,S-CLSVOF)捕捉水气交界面,并基于分叉模型(bifurcation model,BM)进行数值模拟,分析了吸气涡随喇叭口悬空高度的变化规律,并从喇叭口处涡量及涡拟能的角度,分析了产生该规律的机理。结果表明:吸气涡的大小和进水管内相对吸气率β呈正相关,且平均相对吸气率在3×10^(-4)~7×10^(-4)之间;平均相对吸气率基本随悬空高度的增加呈下降趋势,但在C=0.35D(D为喇叭口直径)处出现突降的情况;每个方案涡量随时间的变化规律表明涡量可定量体现吸气涡的强度;通过对涡拟能输运方程中的分析,发现漩涡受到的拉伸作用决定了平均相对吸气率的变化规律,且与吸气率的变化规律一致,揭示了吸气率突降的机理。同时,分析研究结果发现,在设计进水池时,考虑到吸气涡程度与泵的安装,C=0.35D的悬空高度为最优选择。本文结论对进水池的设计具有指导意义。
Open intake is an important hydraulic structure in small and medium-size pump stations.The air-entrained vortex is prone to occur in the open intake when the structural size design is unreasonable,and cavitation may occur in serious cases,affecting the safe and stable operation of the pumping station.The previous studies have revealed that the floor clearance C has a great influence on the flow in the intake,but the influ-ence on the air-entrained vortex is not given.According to the value range of floor clearance given in the design code of pump station,this paper uses the S-CLSVOF method to capture the water air interface,and carries out numerical simulation based on Bifurcation model,and analyzes the variation law of air-entrained vortex with the floor clearance of bell mouth.Combining the vorticity at the bell mouth and the Reynolds-averaged enstrophy,the mechanism of this variation law is analyzed.The results show that the size of air-entrained vortex is related to the relative air-en-trainment rateβin the inlet pipe,the average of which was 3×10^(-4)~7×10^(-4).The value ofβbasically decreased with the increase of floor clear-ance,but there was a sudden drop at C=0.35D(D is the bell mouth diameter).The variation law of vorticity with time in each scheme is analyzed,and the vorticity can quantitatively reflect the intensity of air-entrained vortex.Through the analysis of Reynolds-averaged enstrophy transport equation,it is found that the tilting effect of the vortex determines the variation of the average relative air-entrainment rate,which is consistent with the change law of the air-entrainment rate,and also reveals the mechanism of the sudden drop.When designing the intake,by considering the degree of air-entrained vortex and the installation of pump,C=0.35D is the optimal choice.
作者
黄先北
方涛
郭嫱
陈徐睿
庞凯文
仇宝云
HUANG Xianbei;FANG Tao;GUO Qiang;CHEN Xurui;PANG Kaiwen;QIU Baoyun(College of Electrical,Energy and Power Eng.,Yangzhou Univ.,Yangzhou 225127,China)
出处
《工程科学与技术》
EI
CAS
CSCD
北大核心
2023年第5期161-168,共8页
Advanced Engineering Sciences
基金
国家自然科学基金项目(51909231,51806187,52179091)
江苏省研究生科研与实践创新计划项目(SJCX21_1577)
江苏省水利科技项目(2019019,2019017)。
作者简介
黄先北(1991—),男,副教授,博士.研究方向:机械内部流动,CFD理论.E-mail:znhuang@163.com;通信作者:庞凯文,E-mail:pangkw@163.com。
