基于CFD的低比转速离心泵叶轮切割对其性能影响的研究

发布时间：2018-03-05 22:10

本文选题：低比转速离心泵　切入点：切割　出处：《兰州理工大学》2012年硕士论文　论文类型：学位论文

【摘要】：通常定义30n_s80的离心泵为低比转速离心泵，它因具有流量小、扬程高的特点被广泛应用在石油、化工、矿山等领域。低比转速离心泵内部流动十分复杂，它是带有旋涡运动的三维不可压湍流流动，采用一般的实验方法很难对其内部流动进行分析研究。目前，利用CFD对离心泵内部流场进行数值模拟是一种有效的研究方法。为了达到对离心泵性能的需求，扩大离心泵的使用范围，通常对离心泵叶轮外径采取切割的方式。常规的切割方法是选取性能高于所需性能的离心泵，对其叶轮外径按照现行的切割公式进行计算、修正，然后实施切割。离心泵叶轮外径经过切割之后叶轮几何参数发生了变化，使得其内部流动与原型泵相比存在一定的差异。本文对MH-47-100型低比转速离心泵在D'_2/D_20.9和0.8D'_2/D_20.9 情况下共进行了五次切割，得到了切割之后离心泵的性能曲线。对五次切割后的各性能曲线进行了分析对比，讨论了低比转速离心泵叶轮外径切割后的离心泵性能的变化。本文对MH-47-100型低比转速离心泵开展研究主要为：1：对离心泵叶轮外径进行了5次切割，利用CFD对原型泵及切割后的各个模型进行了定常数值模拟计算，分析了叶轮外径变化对离心泵内部流动带来的影响。2：计算了切割前和切割后各模型的面积比，根据现有文献对面积比高效区的统计，得出了切割之后的各模型均落入高效区的特点。 3.在定常计算基础上对原型泵及经8mm和40mm切割后的两模型共计三模型进行了非定常数值模拟计算，分析不同叶轮外径下泵内部流动的变化。 4.在叶轮出口及隔舌设置共设置9个监测点，分析了不同外径下的叶轮出口面和蜗壳出口压力脉动。通过研究得出的主要结论有： 1：低比转速离心泵叶轮外径经少量切割后，切割后的泵与原型泵内部流动较为相似；叶轮外径经大量切割后，两者流动不再相似。 2：在少量切割（低于10%切割量）下，离心泵外特性曲线较为相似，经大量切割后，泵的外特性曲线不再相似。 3：通过各模型均落入面积比高效区的现象，说明了面积比高效区的统计规律具有一定的参考价值。 4：叶轮外径切割后对离心泵蜗壳内部静压值的影响要大于对叶轮内部的静压值。随着切割的增大，，泵内各点的静压值均下降。 5：通过非定常计算得到了三模型不同时刻的压力脉动，并通过对比分析得到，叶轮外径减小，压力脉动强度变小。
[Abstract]:Usually, 30ns80 centrifugal pump is defined as low specific speed centrifugal pump. It is widely used in petroleum, chemical industry, mine and other fields because of its small flow rate and high lift. The internal flow of low specific speed centrifugal pump is very complicated. It is a three-dimensional incompressible turbulent flow with vortex motion. It is difficult to analyze and study the internal flow by using general experimental methods. At present, numerical simulation of flow field in centrifugal pump by CFD is an effective method. In order to meet the demand of centrifugal pump performance and expand the use range of centrifugal pump, the outside diameter of impeller of centrifugal pump is usually cut. The conventional cutting method is to select the centrifugal pump whose performance is better than the required performance. The outer diameter of the impeller is calculated and corrected according to the current cutting formula, and then it is cut. The geometric parameters of the impeller are changed after the impeller outer diameter of the centrifugal pump has been cut. In this paper, the MH-47-100 type low specific speed centrifugal pump is compared with the prototype pump. In this paper, we compare the two types of MH-47-100 low specific speed centrifugal pump with two parts: 20 / 20. 9 and 0. 8 D / D 20. 9 in D / D _ 2 / D _ 2 / D _ (20. 9). The performance curve of centrifugal pump after cutting was obtained. The performance curves are analyzed and compared, and the change of centrifugal pump performance after cutting impeller outer diameter of low specific speed centrifugal pump is discussed. In this paper, the research on MH-47-100 centrifugal pump with low specific speed is mainly carried out as follows: 1: cutting the outer diameter of centrifugal pump impeller five times. Using CFD for prototype pump and after cutting. The model is calculated by steady numerical simulation, and the influence of impeller outer diameter change on the flow inside centrifugal pump is analyzed. The area ratio of each model before and after cutting is calculated. According to the statistics of the area ratio high efficiency region in the existing literature, the characteristics of each model falling into the high efficiency region after cutting are obtained. 3. On the basis of steady calculation, the unsteady numerical simulation of the prototype pump and the total three models after 8 mm and 40 mm cutting are carried out, and the variation of the flow inside the pump under different impeller diameter is analyzed. 4. Nine monitoring points were set up at the outlet of impeller and tongue, and the pressure pulsation of the outlet surface and volute outlet of impeller under different external diameters were analyzed. The main findings of the study are:. 1: the inner flow of the impeller of the centrifugal pump with low specific speed is similar to that of the prototype pump after a small amount of cutting, but the flow of the impeller is no longer the same after a large number of external diameters of the impeller are cut. 2: in a small amount of cutting (less than 10% cutting volume), the external characteristic curve of centrifugal pump is similar, after a lot of cutting, the external characteristic curve of pump is no longer similar. 3. Through the phenomenon that all the models fall into the area ratio high efficiency region, it is proved that the statistical law of the area ratio efficiency region has certain reference value. 4: the influence of the outer diameter of impeller on the internal static pressure of the volute of centrifugal pump is greater than that on the impeller. With the increase of cutting, the static pressure of each point in the pump decreases. 5: through unsteady calculation, the pressure pulsation of three models at different times are obtained, and by comparison and analysis, it is found that the impeller outer diameter decreases and the pressure pulsation intensity becomes smaller.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH311

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