摘要
管道中固液两相流水击对管道和输送系统可能产生严重的破坏,而固液两相在这种非恒定流中的运动特性是计算最大水击压力变化的重要依据。采用粒子图像测速技术(Particle Image Velocimetry,PIV),通过试验研究水击发生时,水平圆管中不同平均流速、颗粒粒径条件下,流体介质和粗颗粒在管道断面的速度分布以及粗颗粒跟随性的变化规律。研究结果表明:(1)在水击发生的不同时刻,圆管流中粗颗粒的流速在管道断面分布呈不规则的抛物线型分布,主要表现为靠近管道壁面底部的颗粒流速略小于靠近管道顶部流速,当颗粒粒径大于1.5 mm,平均流速小于2.5 m/s时,粗颗粒表现出明显的沉降特性;(2)粗颗粒的跟随性与颗粒受力有密切关系,其中颗粒速度与流体速度的变化量是影响颗粒受力的重要参数;(3)基于试验数据拟合得到了水击条件下粗颗粒跟随性系数k的经验公式,并分析了颗粒粒径、管道直径、两相流平均流速以及水击发生时间等不同参数对粗颗粒跟随性系数的影响,公式计算值与实测值之间的误差在5%以内。
Water hammer phenomena within solid-liquid two phases flow may cause serious damage to pipeline and transportation system, the motion characteristics of such unsteady flow are important values for calculating maximum pressure of water hammer. In this research paper, under water hummer condition, with various average flow rate and particle sizes in vertical pipe section, Particle Image Velocimetry （PIV） technique is utilized to study variation law of the velocity distribution of fluid medium and coarse particles as well as variation law of coarse particles followability. The following results are obtained： （~） At the different moments of water hammer, the flow rate of coarse particles in the pipe flow is shown as irregular parabolic distribution in the cross section of the pipeline, mainly presented as the velocity of the particles near the bottom of the pipe wall is slightly less than the velocity near the top of the pipe, when the particle size is greater than 1.5 mm and the average flow rate is less than 2.5 m/s, coarse particles exhibit signifi- cant sedimentation characteristics; ~） The followability of coarse particles is closely related to the force on particles, the change of particle velocity and fluid velocity are important parameters that affect the force on partlcles; （~） Based on the experimental data, the empirical formula of coarse particle followability coefficient k is obtained under water hammer, and the effects of different parameters such as particle size, pipe diameter, average flow velocity of two- phase flow and time of water hammer on the coherence coefficient of coarse particles were analyzed. The error between the calculated value and the measured value is less than 5%.
出处
《水科学进展》
EI
CAS
CSCD
北大核心
2017年第3期356-363,共8页
Advances in Water Science
基金
国家自然科学基金资助项目(51339008
51209238)~~
关键词
非恒定流
低浓度
粗颗粒
跟随性
unsteady flow
low concentration
coarse particles
foll0wability
