单级双吸离心泵进口边参数对泵性能影响的研究

发布时间：2018-05-01 10:05

本文选题：双吸离心泵 + 叶片进口边　；参考：《兰州理工大学》2012年硕士论文

【摘要】：双吸离心泵具有单机流量大、扬程高、结构简单等特点，是泵类产品中数量多，用途广泛的一种产品。国内目前生产的双吸泵在实际运行时的效率较发达国家低十个百分点左右，为此，有必要对国产双吸泵进行研究和技术改造，以改善其水力性能。本文针对国内某厂生产的ES200-250（ns=185.7）型单级水平中开式双吸泵，依据一元理论对叶轮的轴面流道进行设计检查，发现叶轮轴面流道的过水断面面积沿流道中线的变化规律在进口边附近的变化情况不佳；利用CFD软件对其内部流场进行数值模拟，，发现叶轮的进口处存在较强的漩涡，由此推断导致该双吸泵效率低的主要原因是叶轮进口处的水力设计不尽合理。以此为基础，根据叶片进口边是否位于同一轴面（同一轴面、进口边外缘前掠、后掠）、叶片进口边的位置，以及叶轮前盖板曲率半径的不同设计出了包括原方案在内的共14种模型方案（Aa~Cd、Da、Db，其中Ba为原方案模型）。依据数值计算结果预测每种方案的性能，研究叶片进口边是否位于同一轴面、叶片进口边的位置、叶轮前盖板曲率半径对双吸离心泵性能的影响。通过对这些方案全流场数值模拟结果进行对比分析，获得以下结论： 1.为了研究叶片进口边是否位于同一轴面对离心泵性能的影响，设计了三组模型A、B、C，其中模型A的叶片进口边在同一轴面上，模型B的外缘进口边后掠10o，模型C的外缘进口边前掠10o。由数值模拟结果发现，B、C模型在3组模型中能量性能较为优秀，其中B模型的速度分布与压力分布均优于模型C，抗汽蚀能力更强。因此对于中高比转速的双吸离心泵来说，叶片进口边不放在同一轴面上可以提高泵的效率，将外缘进口边前掠或是后掠均可以获得更高的效率，而外缘进口边后掠则具有更好的抗汽蚀性能。 2.为了研究叶片进口边位置对离心泵性能的影响，对A、 B、 C三组模型的原进口边位置分别进行三次后移，参考木模图，相对于原始进口边位置每次分别后置20o、30o、40o，设计出包括原叶型在内的各四种模型方案（Aa~Cd），其中Ad、Bc、Cd分别为三组模型中能量性能较为优秀的模型，模型Bc的综合性能最好，相对于原方案Ba在最高效率点时的扬程提高了1.53m，水力效率提高了6.10%，且高效点右移。 3.在叶轮径向和轴向尺寸不变的情况下，为了研究叶片间有效流道的进出口面积比对离心泵性能的影响，取B组叶轮为研究对象，Ba、Bb、Bc、Bd四组叶轮的叶片间有效流道的进出口面积比分别为1.70、1.65、1.55和1.41，均高于1~1.3的推荐值。在这四组叶轮中，Bc叶轮的效率最高，Bd、Bb叶轮次之，Ba叶轮的效率最低。这说明在叶轮叶片间有效流道面积比高于1~1.3的推荐值的条件下，仍可以获得能量性能较好的叶轮，也说明叶片的进口边位置对离心泵的性能有一定的影响，叶轮进口边向进口方向延长并不一定能改善其水力性能。 4.对于固定的叶轮入口直径、叶轮外径和叶片进出口角，随着前盖板曲率半径的减小，叶轮的最高效率点增高，高效区变窄，关死点扬程升高；随着流量增大，前盖板曲率半径的变化对扬程的影响较小。
[Abstract]:The double - suction centrifugal pump has the characteristics of large single - machine flow , high lift , simple structure and the like , and is a product with a large quantity and a wide application in the pump product . The efficiency of the double - suction pump currently produced in China is about ten percent lower than that of the developed countries . Therefore , it is necessary to study and technical transformation of the domestic double - suction pump so as to improve the hydraulic performance .

Aiming at the ES200 - 250 ( ns = 185.7 ) single - stage double - suction pump produced in a domestic factory , the axial flow path of the impeller is designed and checked according to the theory of one element , and it is found that the change law of the cross section area along the center line of the flow channel is not good near the inlet side .
The numerical simulation of the internal flow field is carried out by CFD software . It is found that there is a strong vortex at the inlet of the impeller , and it is concluded that the main reason for the low efficiency of the double suction pump is that the hydraulic design at the inlet of the impeller is not reasonable . A total of 14 model schemes ( Aa ~ Cd , Da , Db , where Ba is the original scheme model ) , including the original scheme , are designed according to whether the inlet edge of the blade is located on the same shaft surface ( the same axial surface , the outer edge of the inlet edge is swept , swept ) , the position of the inlet edge of the blade , and the radius of curvature of the front cover plate of the impeller . According to the numerical results , the performance of each scheme is predicted , and whether the inlet edge of the blade is located on the same axial surface , the position of the inlet edge of the blade and the radius of curvature of the front cover plate of the impeller are influenced by the performance of the double - suction centrifugal pump . Through the comparative analysis of the numerical simulation results of the whole flow field of these schemes , the following conclusions are obtained :

1 . In order to study whether the inlet edge of the blade is located on the same axis facing the performance of the centrifugal pump , three sets of models A , B and C are designed .

2 . In order to study the influence of the position of the inlet side of the blade on the performance of the centrifugal pump , the original inlet edge positions of the three groups A , B and C are respectively shifted three times , and the four model schemes ( Aa to Cd ) including the original leaf type are respectively arranged at each time of 20o , 30o and 40o in the position of the original inlet side , and the comprehensive performance of the model bc is better than that of the original scheme Ba at the highest efficiency point . The hydraulic efficiency is improved by 6.10 % , and the high efficiency point is shifted to the right .

3 . In order to study the effect of the ratio of inlet and outlet area ratio on the performance of centrifugal pump , the ratio of inlet / outlet area ratio of impeller to impeller is 1 . 70 , 1 . 65 , 1 . 55 and 1 . 41 respectively , which is higher than that of 1 - 1.3 .

4 . For fixed impeller inlet diameter , impeller outer diameter and blade inlet / outlet angle , with the decrease of radius of curvature of the front cover plate , the highest efficiency point of the impeller is increased , the effective area is narrowed , and the lift of the dead center is increased ;
As the flow increases , the change of the radius of curvature of the front cover plate has little effect on the lift .

【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

【参考文献】