旋转超空泡蒸发器叶片参数优化的数值模拟研究

发布时间：2018-02-15 04:18

本文关键词： 海水淡化污水处理旋转超空泡蒸发器数值模拟平面对称空化器蒸汽抽取　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着地球淡水资源的枯竭,海水淡化将是未来获取淡水资源的重要途径。传统的热方法海水淡化方式受结垢和传热系数的限制,导致系统体积庞大、建设和维修困难。而在超空泡的汽液界面上也有液相的汽化过程,其与壁面沸腾过程类似,但具有更大传热系数。将超空泡技术引入到海水淡化中,克服了传统热方法传热系数限制的问题。旋转超空泡蒸发器(RSCE)的提出,使得热方法的海水淡化系统的小型化成为可能。由于其高效的汽液相变方式,RSCE在污水处理等领域也有很好的应用前景。本课题采用CFD数值模拟软件FLUENT对超空泡进行了数值模拟研究。首先,对以RSCE叶片为代表的平面对称空化器和以水下航行体为代表的轴对称空化器形成超空泡规律进行了对比,获得了两者形成超空泡的差异。然后,对等腰三角形和曲线函数形状的平面对称空化器形成超空泡规律进行了二维数值模拟研究。对比了不同形状的平面对称空化器形成超空泡的差异,获得了不同形状的平面对称空化器在不同空化数下形成超空泡的尺寸与所受阻力的拟合公式。其次,利用平面对称空化器二维数值模拟得到的拟合公式,设计出RSCE的三维叶片,对所设计的叶片形成超空泡的规律进行了研究。获得了所设计叶片在不同转速下形成超空泡的规律,发现叶片形成超空泡尺寸与设计值存在差异,并分析了差异产生的原因。获得了抽汽对叶片超空泡的影响规律,发现工作温度的提高对蒸汽抽取量有明显的提升。建立了叶片工作过程中受阻力矩的估算方法,估算误差小于2%。最后,改进了叶片设计方法,设计出新的旋转叶片,对RSCE热力学性能进行了数值模拟研究。得到了抽汽对整个流域温度分布的影响规律,以及汽化过程中超空泡内部的温度变化,初步了解了RSCE的热力学特性。
[Abstract]:With the depletion of the freshwater resources of the earth, seawater desalination will be an important way to obtain fresh water resources in the future. The traditional method of seawater desalination is limited by scaling and heat transfer coefficient, resulting in the huge volume of the system. It is difficult to construct and maintain. The vaporization process of liquid phase is also found at the vapor-liquid interface of the supercavitation, which is similar to the boiling process on the wall, but has a larger heat transfer coefficient. The supercavitation technology is introduced into seawater desalination. It overcomes the limitation of heat transfer coefficient of traditional thermal method. It is possible to miniaturize the seawater desalination system by thermal method. Because of its high efficiency vapor-liquid phase transition, RSCE also has a good application prospect in sewage treatment and other fields. In this paper, the CFD numerical simulation software FLUENT is used to simulate the supercavitation. Numerical simulation is carried out. First of all, The law of forming supercavitation between plane symmetric cavitation apparatus represented by RSCE blade and axisymmetric cavitation apparatus represented by underwater vehicle is compared, and the difference between them in forming supercavitation is obtained. A two-dimensional numerical simulation study on the formation of supercavitation in plane symmetric cavitators with isosceles triangle and curve function shapes is carried out, and the differences of the formation of supercavitation in plane symmetric cavitators with different shapes are compared. The fitting formula of the size of supercavitation and the resistance to the formation of supercavitation in plane symmetric cavitation with different shapes are obtained. Secondly, the three-dimensional blade of RSCE is designed by using the fitting formula obtained by two-dimensional numerical simulation of plane symmetric cavitation. In this paper, the law of supercavitation formation of the designed blade is studied, and the law of supercavitation formation at different rotational speeds is obtained. It is found that the size of the blade forming supercavitation is different from the design value. The influence of extraction steam on the supercavitation of the blade is obtained, and it is found that the increase of working temperature can obviously increase the amount of steam extraction. The method of estimating the impingement moment in the working process of the blade is established. The estimation error is less than 2. Finally, the blade design method is improved, a new rotating blade is designed, and the thermodynamic performance of RSCE is numerically simulated. The effect of extraction steam on the temperature distribution of the whole basin is obtained. The thermodynamic properties of RSCE were preliminarily understood by the temperature change in the supercavitation.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P747

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