水力空化论文：水力空化及CFD数值模拟

【英文摘要】Cavitation is the phenomenon that microbubbles (or called gas nucleus) suddenly grow due to local lower pressure in the liquid and then collapse. Based on the cavitation generation,the cavitation is classified into four types, including acoustic cavitation, optic cavitation, particle cavitation and hydrodynamic cavitation. Hydrodynamic cavitation can occur in the sudden change of piping diameter, hydraulic machinery and so on. The process intensification can be accomplished by energy release in an instant of bubbles collapse.To investigate the mechanism of hydrodynamic cavitation and the fundamentals of its intensificaion law, the detailed studies has been made. The experimental equipments of hydrodynamic cavitation were built. The CFD software FULENT was used to simulate the flow fields of cavitation based oncomputer fluid dynamics. The hydroxyl radical induced by hydrodynamic cavitation was measured with methylene blue as the catcher. Three types of equipments of hydrodynamic cavitation including orifice plate, composite equipment of orifice plate and cantilever reed, rotating cavitation equipment were studied to obtain the optimum hydrodynamic cavitation condititions.From the studies, the conclusions can be drawn. (1) In FLUENT, the hydrodynamic cavitation with orifice plate was simulated with the standard k ?? model and the cavitation bubble dynamics model. The results showed that the increase of inlet pressure could enhance cavitation effect when outlet pressure was invarible. The strength of cavitation also increased with the increase of diameter and amount of orifices, and it decreased with the increase of liquid density and liquid viscosity. When the initial gas fraction increased, the strength of cavitation increased first but then droped.(2) The relationship between the amount of hydroxl radicals induced in hydrodynamic cavitation and the strength of hydrodynamic cavitation was quantitatively established. And methylene blue was used as the catcher for hydroxyl radicals and an ultraviolet-visible spectrophotometer was used to measurethe amount of induced hydroxyl radicals.(3) The strength of hydodynamic cavitation of orifice plate increased with the increase of the inlet pressure. And decreased with the increase of the diameter and amount of orifices. When the liquid rate was invarible, the strength of cavitation increased with the ratio of total perimeter of holes to the total area of the holes.(4) The strength of cavitation of composite equipment of orifice plate and cantilever reed increased with reduction in the cavitation number. When the inlet pressure increased, the strength of cavitation also increased. Compared with single- hole orifice plate, the strength of cavitation of composite equipment increased obviously, which may reach 26.7% most greatly. When the distance of reed to orifice plate and the free reed length decreased, the amount of hydroxyl radical increased, the strength of cavitation also increased.(5) The strength of cavitation of rotating cavitation equipment increased firstly, and then decreased with the increase of the liquid rate . The results showed that optimum flow existed to reach the maximum strength of cavitation.
【目录】水力空化及CFD数值模拟
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摘要4-6ABSTRACT6-8第一章 绪论12-211.1 引言12-131.2 水力空化及空蚀问题13-141.3 课题的工程和学科背景14-161.4 国内外研究进展16-181.4.1 水力空化在生物化工中的强化作用161.4.2 水力空化在环境保护废水处理中的应用16-171.4.3 水力空化对混合的强化171.4.4 水力空化在石油和矿业的钻井工程中的应用171.4.5 水力空化装置动力特性数值模拟研究17-181.5 应用前景、存在问题与发展趋势18-191.5.1 应用前景及存在问题18-191.5.2 发展趋势191.6 课题研究内容和意义19-21第二章 水力空化基本理论21-402.1 引言212.2 空化机理21-252.3 水力空化的发生与发展25-322.3.1 空化初生及空化数26-292.3.2 空化的发展292.3.3 空化泡的溃灭29-322.4 空化引发的效应32-352.4.1 空泡溃灭产生的能量32-352.4.2 空化的能量效应352.5 空泡动力学及汽液两相流35-382.6 空化的分类38-40第三章 孔板水力空化数值模拟40-603.1 引言403.2 模拟软件FLUENT 简介40-423.3 空泡动力学模型42-483.3.1 空泡的静力平衡条件42-433.3.2 空泡运动方程43-453.3.3 蒸汽空泡的突然膨胀45-463.3.4 蒸汽空泡的突然压缩46-473.3.5 纯气体的绝热膨胀和压缩47-483.4 数学模型与计算方法48-533.4.1 湍流数值方法48-493.4.2 k-ω 湍流模型493.4.3 多相流空化模型49-513.4.4 计算方法51-533.5 模拟结果与分析53-593.5.1 初步分析54-553.5.2 沿管轴汽含率553.5.3 操作条件的影响55-573.5.4 物性参数的影响57-593.6 本章小结59-60第四章 孔板水力空化实验60-734.1 引言604.2 实验装置60-614.3 实验原理61-674.3.1 羟自由基捕捉剂61-634.3.2 测定方法63-674.4 实验方法67-684.4.1 实验过程674.4.2 对比实验67-684.5 实验结果分析68-724.5.1 入口压力的影响68-694.5.2 孔径的影响694.5.3 小孔个数的影响69-704.5.4 孔板比周长α的影响70-714.5.5 实验汽含率分布71-724.6 本章小结72-73第五章 孔板—液哨型组合水力空化理论及实验73-835.1 引言735.2 实验装置73-745.3 悬臂式簧片哨振动空化机理74-755.4 悬臂式簧片哨振动空化的可能性分析75-775.4.1 液体的强度75-765.4.2 空化阀765.4.3 气泡的运动76-775.5 实验结果分析77-825.5.1 簧片哨性能研究77-795.5.2 水流空化数的影响79-805.5.3 入口压力的影响80-815.5.4 簧片尖端到孔板距离的影响81-825.5.5 簧片自由端长度的影响825.6 本章小结82-83第六章 尾涡旋转空化发生器实验研究83-876.1 引言836.2 实验装置83-846.3 实验原理846.4 实验结果分析84-856.5 本章小结85-87第七章 结论与展望87-89参考文献89-96致谢96-97攻读学位期间发表的学术论文97
【关键词】水力空化 孔板 数值模拟 亚甲基蓝 悬臂式簧片哨 羟自由基 旋转空化器
【英文关键词】Hydrodynamic cavitation Orifice plate Numerical simulation Mythylene blue Hydroxyl free radical Cantilever reed Rotating cavitation
水力空化论文：水力空化及CFD数值模拟
【中文摘要】空化是由于液体中的局部低压(低于相应温度下该液体的饱和蒸汽压)使液体汽化而引发的微气泡(或称气核)爆发性生长而后又溃灭的现象。根据空化产生的方法一般可以分为四种类型:声空化,光空化,粒子空化和水力空化。其中,水力空化现象发生在很多场合,例如在管径急剧变化的管道中和水力机械中。水力空化发生时伴随空化泡溃灭瞬间产生的能量释放,可以实现过程的强化。为了探究水力空化强化效应的机制和效果,寻求影响空化强化效应的基本规律,本论文就此开展了如下研究工作:设计建立实用有效的水力空化实验装置;根据计算流体力学理论,Байду номын сангаасCFD软件FLUENT对空化流场进行数值模拟;采用空化自由基捕捉方法,定量检测水力空化羟自由基;在此基础上,研究了孔板、孔板—液哨型组合空化器及尾涡旋转空化器的各种参数对空化自由基产量的影响,以寻求最佳空化条件。研究结果表明:(1)在FLUENT中,可以采用标准k ??模型和空泡动力学模型对孔板式水力空化器进行数值模拟,模拟结果表明:当出口压力一定时,入口压力越大,空化强度越剧烈;增加孔径及小孔个数使空化强度减弱;增大液体密度和粘度使空化强度减弱;增大液体初始含气量使空化强度先增大后减小;(2)利用亚甲基蓝溶液能够成功捕捉水力空化产生的羟自由基,然后可以采用紫外分光光度计定量检测空化羟自由基;(3)孔板式水力空化器的空化效应随入口压力的增大而增强;孔径及小孔个数增加,空化效应减弱;流量相同的情况下,空化效应随孔板比周长的增加而增强。(4)孔板—液哨型组合空化器的空化效应随空化数减小而增强;入口压力增大,空化效应增强;与单孔孔板相比,加入悬臂式簧片哨后的组合水力空化器空化效应明显增强,最大可提高26.7%,且簧片尖端到孔板距离较短、簧片自由端较短时,·OH产量更高,空化效应更剧烈。(5)尾涡空化旋转发生器的空化效应随入口流量的增加而先增大后减小,即流量存在一个最佳值使空化效应最强。