首页 | 本学科首页   官方微博 | 高级检索  
     

定向凝固过程中的流动效应
引用本文:张国志, 冯妍卉, 张欣欣, 聂红. 定向凝固过程中的流动效应[J]. 工程科学学报, 2008, 30(5): 548-552. DOI: 10.13374/j.issn1001-053x.2008.05.008
作者姓名:张国志  冯妍卉  张欣欣  聂红
作者单位:1.北京科技大学机械工程学院, 北京 100083
摘    要:在类合金(NH4Cl-H2O溶液)定向凝固晶体生长实验装置上,利用ϕ30μm煤粉作示踪粒子,再现糊状区内微通道流以及通道出口处的流体流动,并测算了各处流体的瞬时速率.分析认为:凝固初期,糊状区内固相体积分数较大,内部流体流动受阻;随着固相体积分数减少,糊状区孔隙率增大,流体充分发展;当平均固相体积分数降至0.42,接近最小值0.38时,当量雷诺数达到临界值(247),糊状区内形成微通道;随着通道宽度逐渐扩大,液相区内热流体进入微通道.微通道内稀冷液体向上流,浓热液体向下流,促使通道内溶液再结晶.

关 键 词:定向凝固  流动效应  临界雷诺数  微通道  再结晶
收稿时间:2007-03-04
修稿时间:2007-09-10

Convective effects during unidirectional solidification
ZHANG Guozhi, FENG Yanhui, ZHANG Xinxin, NIE Hong. Convective effects during unidirectional solidification[J]. Chinese Journal of Engineering, 2008, 30(5): 548-552. DOI: 10.13374/j.issn1001-053x.2008.05.008
Authors:ZHANG Guozhi  FENG Yanhui  ZHANG Xinxin  NIE Hong
Affiliation:1.School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
Abstract:Directional solidification experiments were carried out using the analogue casting system of NH4Cl-H2O solution by cooling it from below. The transient velocities of fluid flow within the micro-channel of mushy layer were measured by using observation facility and tracer coal particles of 30 μm in diameter. It turned out that during the solidification process, the mean solid fraction of mushy layer descended rapidly at first, so the mushy layer got more permeable and natural convection was more likely to occur. When the mean solid fraction was down to 0.42, and closed to the smallest value of 0.38, and the equivalent Reynolds number exceeded the critical value, about 247, plume convection with associated micro-channel occurred in the mush. With the expanding of channel width, the solution of liquid region, whose temperature was higher than that of mushy layer, flowed into the micro-channel. The convection within the channel was found to consist of upward flow and downward flow. The counter flow advected heat away and solute which was favorable to solidification, so that solution within the channel recrystallized.
Keywords:unidirectional solidification  convective effect  critical Reynolds number  micro-channel  recrystallization
本文献已被 万方数据 等数据库收录!
点击此处可从《工程科学学报》浏览原始摘要信息
点击此处可从《工程科学学报》下载全文
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号