离心泵叶轮特殊切割方法的研究与探讨

发布时间：2018-01-14 17:16

本文关键词：离心泵叶轮特殊切割方法的研究与探讨　出处：《浙江工业大学》2012年硕士论文　论文类型：学位论文

【摘要】：低比转速离心泵的H-Q性能曲线比较平坦,容易产生驼峰。驼峰特性曲线的关死点扬程低于泵的最大扬程值,在运转中不稳定,特别是在小流量工况,泵和管路系统内可能会产生振动和噪声,具有较大的危害性。因此寻找简单易行的消除泵特性曲线驼峰的方法具有重要的意义。斜切叶轮外径、叶片出口边三角形切割等一些特殊的叶轮切割方法可以消除离心泵特性曲线驼峰,但这些切割方法的应用大多依赖于经验,切割尺寸的选择缺少理论依据。为此,本文在这两种特殊切割方法的基础上,提出一种新型的半圆形切割方法,以这三种叶轮特殊切割方法为研究对象,采用CFD数值模拟方法,对叶轮及蜗壳内部流动状态进行计算和分析,同时对不同的叶轮切割方法及其切割尺寸与离心泵性能曲线驼峰之间的关系进行了理论分析,并制造样机对模拟结果进行试验验证。最终得到了几种优秀的切割模型,为离心泵叶轮特殊切割方法的使用提供了科学依据。本文的主要研究工作包括： (1)查阅了大量国内外研究离心泵叶轮切割的文献,综述了叶轮切割定律以及叶轮切割方法的研究现状,为提出新型叶轮切割方法提供理论依据和前期准备工作。 (2)系统地介绍了利用CFD数值模拟计算离心泵流场分布的研究方法,包括离心泵的Pro/E三维建模方法、Gambit网格生成方法、Fluent求解器参数定义和离散化方法的选择。并利用该方法对IS80-50-250型单级单吸清水离心泵内流场进行CFD数值模拟。 (3)对三角形切割、半圆形切割和斜切叶轮外径方法进行详细的描述,制定多组研究方案对三种叶轮特殊切割方法进行研究。介绍了基于CFD数值模拟的离心泵性能曲线预测方法,并利用该方法预测模型泵及各切割方案的离心泵性能曲线。比较各种切割方案对性能曲线的改善情况,确定三角形切割、半圆形切割和斜切叶轮外径方法的最佳切割尺寸。 (4)根据数值模拟结果,利用Fluent后处理工具,分析离心泵的内部流动规律。结果表明,在小流量工况时,离心泵叶轮出口以及蜗壳内部存在较大的压力梯度,速度分布不均匀,由此产生的混合冲击损失导致关死点扬程降低,并使泵特性曲线产生驼峰。对叶轮叶片出口边进行特殊形状的切割可以改善小流量工况泵内部湍流流动状态,从而消除泵特性曲线驼峰。 (5)对模型泵及三角形最佳切割方案进行离心泵性能试验,验证数值模拟结果的准确性。试验表明扬程预测误差为-3.02%～1.69%,效率预测误差为1.46%～4.72%,最大误低于5%,模拟结果和试验结果符合良好。
[Abstract]:The H-Q performance curve of the centrifugal pump with low specific speed is flat and easy to produce hump. The dead point head of the hump characteristic curve is lower than the maximum lift value of the pump and is unstable in operation especially in the small flow condition. The vibration and noise may occur in the pump and pipeline system, which is harmful. Therefore, it is of great significance to find a simple and feasible method to eliminate the hump of the pump characteristic curve. Some special impeller cutting methods, such as external diameter of oblique impeller and triangular cutting of blade outlet edge, can eliminate the hump of characteristic curve of centrifugal pump, but the application of these cutting methods mostly depends on experience. The selection of cutting size is lack of theoretical basis. Therefore, based on the two special cutting methods, this paper proposes a new semi-circular cutting method, taking these three special impeller cutting methods as the research object. The flow state of impeller and volute is calculated and analyzed by CFD numerical simulation method. At the same time, the relationship between different impeller cutting methods and the relationship between the cutting size and the hump of centrifugal pump performance curve is analyzed theoretically. Finally, several excellent cutting models are obtained, which provide a scientific basis for the use of special cutting methods for centrifugal pump impeller. The main research work of this paper includes: 1) A large number of literatures on centrifugal pump impeller cutting are reviewed, and the current research status of impeller cutting law and impeller cutting method is summarized. It provides theoretical basis and preparatory work for the new impeller cutting method. This paper introduces the research method of calculating flow field distribution of centrifugal pump by CFD numerical simulation, including Pro/E 3D modeling method of centrifugal pump and Gambit mesh generation method. The parameter definition of Fluent solver and the choice of discretization method are used to simulate the flow field in IS80-50-250 single-stage single-suction centrifugal pump with CFD. 3) the methods of triangle cutting, semicircle cutting and oblique cutting impeller outer diameter are described in detail. Three kinds of special impeller cutting methods are studied in this paper. The prediction method of centrifugal pump performance curve based on CFD numerical simulation is introduced. This method is used to predict the performance curve of the model pump and the centrifugal pump of each cutting scheme. The triangle cutting is determined by comparing the improvement of the performance curve of various cutting schemes. Optimum cutting size of semicircle and oblique cutting impeller outer diameter method. 4) according to the numerical simulation results, the internal flow law of centrifugal pump is analyzed by using Fluent post-processing tool. The results show that the flow rate is small in the case of small flow rate. There is a large pressure gradient and uneven velocity distribution in the outlet of centrifugal pump impeller as well as inside the volute. The resulting mixed impact loss results in the decrease of closed dead point head. The special shape cutting of the impeller blade outlet edge can improve the turbulent flow state of the pump under small flow conditions, thus eliminating the hump of the pump characteristic curve. The model pump and triangle optimum cutting scheme are tested to verify the accuracy of numerical simulation results. The results show that the error of lift prediction is -3.02% and 1.69%. The efficiency prediction error is 1.46 and 4.72, and the maximum error is less than 5. The simulation results are in good agreement with the test results.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH311

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