CIESC Journal ›› 2018, Vol. 69 ›› Issue (6): 2455-2462.DOI: 10.11949/j.issn.0438-1157.20171302

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Visualization study on pressure drop and superimposed oscillations under low pressure natural circulation in rectangular channel

ZHANG Wenchao, JIAO Qi, ZHOU Yunlong, YANG Mei, JIN Guangyuan, DU Lipeng   

  1. School of Energy and Power Engineering, Northeast Electric Power University, Jilin 132012, Jilin, China
  • Received:2017-09-27 Revised:2017-12-20 Online:2018-06-05 Published:2018-06-05
  • Supported by:

    supported by the National Natural Science Foundation of China (51776033) and the Education Department of Jilin Province Science and Technology Research Project of "13th Five-Year" (2016-79).

矩形通道内低压自然循环压降型脉动及其复合型脉动可视化研究

张文超, 焦琦, 周云龙, 杨美, 金光远, 杜利鹏   

  1. 东北电力大学能源与动力工程学院, 吉林省 吉林市 132012
  • 通讯作者: 焦琦
  • 基金资助:

    国家自然科学基金项目(51776033);吉林省教育厅“十三五”科学技术研究项目(2016-79)。

Abstract:

With deionized water as working fluid, visualization technique was used to study pressure drop and superimposed oscillations of low pressure natural circulation in rectangular channel. Gas-phase distribution images captured during oscillation processes were compared with flow pulsation curve to assess physical process and mechanism of flow oscillation. Four types of dynamic instabilities were found in the study, i.e., density wave oscillation by gravity (DWO), pressure drop oscillation (PDO), superimposed oscillation (SPO), and density wave oscillation by friction (DWO). Due to squeezing effect of rectangular channel and compressible space limitation within surge tank, working fluid flew cyclically between surge tank and circulation circuit and generated pressure drop oscillation (PDO). With increase of heating power, superimposed oscillation was formed by overlapping PDO and DWO. The onset points of both oscillations tended to diverge with increase of inlet overcooling degree, and such diverging tendency enlarged when system pressure was increased. DPO instability boundary curve was plotted against dimensionless parameters, such as overcooling degree and phase change.

Key words: instability, gas-liquid flow, rectangular channel, pressure drop oscillation, visualization method

摘要:

以去离子水为工质,对矩形通道内低压自然循环压降型脉动及其复合型脉动进行可视化实验研究,利用可视化手段拍摄脉动过程气相分布状态图像。通过流量脉动曲线与图像进行对照,分析流量脉动的物理过程及产生机理。实验过程中发现4类动态不稳定性:第Ⅰ类密度波(DWO)、压降型脉动(PDO)、复合型脉动(SPO)及第Ⅱ类密度波(DWO)。重点分析了压降型脉动与复合型脉动产生机理、影响因素及流动不稳定性边界。实验研究发现,受矩形通道挤压效应及稳压器内部可压缩空间影响,工质在稳压器和循环回路之间往复波动,形成压降型脉动,增大加热功率压降型脉动会叠加第Ⅱ类密度波形成复合型脉动。两类脉动的起始点会随入口过冷度增加呈现偏离趋势,并且压力增加,偏离趋势会随之增大。通过相变数、过冷度数等无量纲参数绘制了压降型脉动不稳定性边界。

关键词: 不稳定性, 气液两相流, 矩形通道, 压降型脉动, 可视化方法

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