自吸泵自吸过程气液两相流动试验研究

发布时间：2018-01-11 02:09

本文关键词：自吸泵自吸过程气液两相流动试验研究　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：泵的自吸过程包含了气液混合、气液分离等气液两相间复杂的物理变化,特别是自吸过程中泵内气泡的分布和运动规律等与泵的自吸性能和自吸机理有着密切的联系。目前国内外对自吸泵的研究着重于水力性能参数的变化对自吸性能的影响等宏观自吸现象,缺乏对泵内气液两相流态变化的微观研究,没有深入研究自吸机理。本文通过水力性能试验、自吸性能试验、自吸过程的瞬态测试和高速摄影试验研究,外混式自吸离心泵在不同水力性能参数下的自吸过程,建立自吸过程中气泡数量、大小和运动轨迹与自吸性能之间的关系,进一步揭示泵的自吸机理,为自吸泵的自吸结构设计提供理论基础。本文主要的研究内容和成果如下:1.以65ZB-40C型外混式自吸离心泵为基础,根据自吸泵设计理论,设计了有机玻璃样机,设计了可移动的隔舌部件。搭建了自吸泵水力性能闭式试验台,对自吸泵样机进行水力性能试验研究叶轮出口圆周速度以及隔舌间隙对自吸性能的影响,结果表明泵自吸时间随着叶轮圆周速度的增大或者隔舌间隙的减小而缩短。2.搭建自吸泵的高速摄影试验系统,测量不同隔舌间隙以及叶轮出口圆周速度条件下,转速、泵进出口压力和流量等参数的变化,同时拍摄自吸过程叶轮、气液分离室、蜗壳等关键部件内气液两相流态的变化。结果表明自吸过程可以分为自吸启动阶段、自吸稳定阶段和自吸突变阶段,自吸稳定阶段是一个动态稳定的过程,这个过程占整个自吸过程的时间的比例最大,对自吸过程的影响最大。叶轮外缘的气液混合层以及气液分离室内的气相空穴是自吸稳定进行的必要条件。3.通过滤波去噪、图像的二值化和图像填充等方法对高速摄影拍摄到的自吸过程的中气泡的数字图像进行预处理。本文使用了差影法去除背景噪声,比较中值滤波、高斯滤波和Wiener滤波三种平滑去噪方式,并将这三种方式得到的结果图像分别使用最大类间方差法和迭代法求阈值进行图像的二值化比较效果,选择高斯滤波和最大类间方差法的处理过程,再用MATLAB的imfill函数进行图像填充,重新获得因二值化丢失的气泡中心的信息。4.在图像预处理的基础上,提取二值图像中气泡的数量、大小、运动轨迹和运动速度等信息,研究微观自吸过程的气泡特征与宏观的自吸性能变化的内在联系。结果表明,蜗壳扩散段靠近气液分离室的左边区域的气泡群对比右边区域显得直径小而且数量密集。直径较小的气泡群相比于直径较大的更容易排出泵体,即减小气液两相流中气泡的尺寸,把更多的停滞气泡转化为移动气泡是一个缩短自吸时间,提高自吸性能的有效途径,这也是泵的自吸时间随着隔舌间隙的减小而缩短的原因。
[Abstract]:The self-priming process includes gas-liquid mixing, gas-liquid separation and other physical changes of gas-liquid two phase complex, especially since the bubble pump suction in the process of distribution and movement law and pump self-priming performance of self-priming and mechanism are closely linked. At home and abroad to study the change of emphasis on self suction pump the hydraulic parameters of the self-priming performance influence of macro self absorption phenomenon, lack of microscopic study on the changes of the gas-liquid two-phase flow pattern inside the pump, there is no in-depth study of self suction mechanism. The hydraulic performance test, self-priming performance test, experimental study on the transient test and high speed photography absorption process, external mixing type self suction the process of suction centrifugal pump in different hydraulic performance parameters, the establishment of self absorption in the process of bubble size and quantity, relationship between trajectory and self-priming performance, self suction pump to further reveal the mechanism, structure design of self suction self suction pump For the theoretical basis. The main research contents and results are as follows: 1. to 65ZB-40C outside the mixed type self-priming centrifugal pump based on self-priming pump design theory, design a prototype design of organic glass, the tongue part can be moved. To build a self suction pump hydraulic performance test rig, the self suction the pump prototype test on the hydraulic performance of outlet circumferential speed of impeller and volute tongue clearance effect on the performance of self-priming pump self-priming time, results show that with the decrease of the circumference of the impeller speed increases or tongue clearance and shorten the.2. to build a self suction pump with high speed photography test system, measuring different separation tongue gap and impeller circumferential velocity under the condition of changing speed, pump inlet and outlet pressure and flow parameters, while filming the self-priming process of impeller, gas-liquid separation chamber, the gas-liquid two-phase flow pattern changes in key parts of the volute. The results show that the self absorption process can Divided into self suction start-up stage, stable stage and self suction self suction self suction mutation stage, stable stage is a dynamic stabilization process, this process accounted for the entire process of self absorption time was the highest, the greatest impact on the process of self absorption. The outer edge of the impeller gas-liquid mixing layer and separation chamber gas hole is a necessary condition for self absorption of the stability of.3. by filtering, self suction process of the air bubbles in the digital image binarization and image filling method of image of high-speed photography to the pretreatment. The removal of background noise subtraction method, comparison of median filter, Gauss filter and Wiener filter three denoising method, and will be the three kinds of results using the two value image Otsu method and iterative threshold method for image comparison, Gauss filtering and Otsu method. Process, the imfill function with MATLAB for image filling, to regain lost due to binarization bubble center information.4. based on image preprocessing, extracting two value image, bubble size, trajectory and velocity information of micro and macro bubble characteristics of self suction self relation suction performance change process. The results show that the bubble group compared the right area of the left area of volute diffuser near the gas-liquid separation chamber is small in diameter and quantity. The smaller diameter bubble group compared to the larger diameter more easily out of the pump body, which reduce the air liquid two-phase flow in bubble size, the more stagnant bubble into mobile bubble is a shortened self-priming time, improve the effective way of self suction performance, self-priming time shortened with decreasing separation tongue gap this also is the cause of the pump.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH317

【参考文献】