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首页» 过刊浏览» 2017» Vol. 2» Issue (2) 228-239     DOI : 10.3969/j.issn.2096-1693.2017.02.021
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淹没空化射流空泡云动态变化规律研究
彭炽,李根生,田守嶒
中国石油大学(北京)油气资源与工程国家重点实验室,北京 102249
Dynamics of cavitation cloud in submerged cavitation water jet
PENG Chi, LI Gensheng, TIAN Shouceng
State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum-Beijing, Beijing 102249, China

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摘要  淹没空化射流具有很强的空化冲蚀能力,在石油钻井、储层改造等方面有着广泛的应用,空化射流中空泡云的动态变化与射流冲蚀过程密切相关。本文开展了高速摄影拍摄淹没空化射流实验,利用图像差分法对空泡云动态规律进行了深入分析,讨论了空泡云周期性脱落的机理,并首次研究了变量类型(空泡云长度、面积、宽度、射流中心点灰度值、灰度均值)和取值位置对确定空泡云脱落频率的影响,优化了确定空泡云脱落频率的方法。研究结果表明,淹没空化射流中的空泡云具有明显的周期性,一个周期主要包括产生—发展—脱落—溃灭4个阶段。空泡云周期性脱落与剪切层内涡的周期性脱落、喷嘴结构以及空泡云导致的喷嘴过流面积变化(“憋压效应”)有关。灰度均值是计算空泡云脱落频率的最佳变量,只有在射流中游一定区域内才能得到一致稳定的脱落频率。本研究有助于加深对淹没空化射流中空泡云动态变化规律的认识,为优化喷嘴结构建立基础。
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关键词 : 淹没空化射流, 空泡云, 动态变化, 脱落频率, 高速摄影, FFT, FDM
Abstract

  Submerged cavitation water jet, with intensive cavitation erosion ability, has been extensively applied for various engineering purposes such as petroleum well drilling and reservoir stimulation. The dynamics of cavitation cloud are closely related to the erosion process of cavitation jet. In this paper, high-speed photography is utilized to visualize the cavitation jet. The dynamic features of cavitation cloud are illustrated using Frame Difference Method; the mechanism of periodic cavitation cloud shedding is discussed; and for the first time, the influences of variable type (the length, area, width of cavitation cloud, the gray level of points in jet center line and the average gray level) and variable position on determining the shedding frequency of cavitation cloud are clarified, based on which the optimal method to decide the shedding frequency is derived. The results show that cavitation cloud in submerged cavitation has evident periodicity. One cycle contains incubation, developing, shedding and collapse phases. The periodic shedding of cavitation cloud seems to be closely related to the shedding of vortex in the shear layer, the nozzle structure and the variety of nozzle open area as a result of the cavitation appearance and its ‘chock effect’. Average gray level is believed to be the optimal viable for determining the shedding frequency of cavitation cloud. Under the experimental conditions in this paper, the shedding frequency of cavitation cloud is decided to be 1 350 Hz. The region where shedding frequency is stable ranges from 17.6 mm to 28.16 mm from the nozzle outlet. This paper provides an important supplement for understanding the dynamics of cavitation cloud in submerged cavitation jet and builds the foundation of optimizing the nozzle geometry based on shedding frequency.

Key words: submerged cavitation jet cavitation cloud dynamic change shedding frequency high-speed photography FFT frame difference method
收稿日期: 2016-12-07     
PACS:    
基金资助:国家自然科学基金“深层高温高压油气井安全高效钻完井基础研究,U1562212”和中英研究与创新桥计划合作项目“地热智能井钻完井关键技术与优化设计平台,S2016G7261”联合资助
通讯作者: 田守嶒, tscsydx@163.com
引用本文:   
彭炽,李根生,田守嶒. 淹没空化射流空泡云动态变化规律研究[J]. 石油科学通报, 2017, 2(2): 228-239. PENG Chi, LI Gensheng, TIAN Shouceng. Dynamics of cavitation cloud in submerged cavitation water jet. Petroleum Science Bulletin, 2017, 2(2): 228-239.
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