【作者】 朱荣生；

【导师】 关醒凡；

【作者基本信息】 江苏大学 ， 流体机械及工程， 2011， 博士

【摘要】 离心泵广泛应用于农业排灌、市政、轻工、化工、建筑、矿山和冶金等部门。随着社会进步和科技发展,人们对泵的高效率、稳定性和低噪声等方面提出了更苛刻的要求。目前广泛采用的离心泵叶轮水力设计方法,主要是以Stepanoff的经验系数方法为基础的相似设计法。这种方法的特点是总结了前人设计制造经验,特别是应用计算机以后,建立了优秀水力模型的数据库,这样,根据所需要的流量、扬程,从数据库选出合适比转数的水力模型设计一台相似泵,满足生产上的需要。但是,随着近年来对离心泵设计工况点的参数(如流量、扬程等)的精度要求越来越高,传统一元理论日益显示出在设计方面的不足。本文通过对3种离心泵方案等扬程设计研究,发现等扬程设计离心泵在叶片出口处流动并不理想,通过采用不等扬程设计方法,分别对3种离心泵方案进行了水力设计,获得了较好的叶片出口总压,静压及流速分布。并结合数值模拟CFD技术,对两种设计结果进行定常和非定常数值模拟,证实了不等扬程设计离心泵叶片方法的优越性,最后分别对等扬程设计的离心泵和不等扬程设计的离心泵进行试验研究和比较分析,进一步证实了不等扬程设计离心泵叶轮理论的正确性。本文主要的研究工作及创新点有：1.全面系统地分析了国内外离心泵水力设计方法的研究现状及进展,对传统离心泵水力设计中的相似换算法、速度系数法、面积比原理、优化设计法、三元理论等进行了较为详细的介绍,阐述了数值模拟技术在离心泵水力设计中的重要性,指出了现有水力设计方法存在的不足,并介绍了不等环量设计法在风机和轴流泵方面的研究及应用情况。2.首次提出了离心泵叶轮不等扬程水力设计方法。通过对传统离心泵水力设计方法的研究发现,传统离心泵水力设计方法会导致叶轮叶片出口处流动不理想,本文首次通过采用不等扬程法进行离心泵水力设计,获得了较好叶片出口总压、静压及流速分布。3.首次运用CFD技术分析了采用不等扬程法设计的离心泵内部定常和非定常流动。定常计算得到了各模型的静压、绝对速度、相对速度、蜗壳断面速度及叶轮出口前后盖板的压力分布,初步揭示了模型泵内的流动规律,分析对比了采用不等扬程设计及等扬程设计的水力性能,总结出采用不等扬程设计优点,并根据不同流量下模型的计算结果进行数据统计,绘制出预测的性能曲线,结果表明采用不等扬程设计中的方案一为最佳设计模型。非定常数值模拟证实了由于叶轮旋转和蜗壳之间的相互作用在离心泵内流动呈现出较强的非定常性,不仅同一时刻叶轮各流道的流动结构有差别,就是同一流道在旋转过程中流动结构也在不断变化,呈现出周期性的波动,致使蜗壳内部沿圆周各位置均存在周期性的压力脉动,压力脉动幅频普的最大幅值对应的频率值为主频与叶片数的乘积,并获得了产生压力脉动的主要影响因素。4.根据数值模拟结果可以实现对泵性能的预测,而通过与外特性试验所得的性能曲线的对比,则又可从一定程度上实现对数值模拟准确性的评估,验证数值预测的可信度。从各个模型数值模拟与实验数据对比表与图中可以看出,模拟结果和实验结果有一定的差距,但总体趋势一致,即在数值模拟中水力性能好的实验结果也比较理想。主要原因：预测值仅为水力效率,未考虑机械效率和容积效率,并且数值模拟把离心泵内的流动理想化了,而实际运行时不可能那么理想且实际运行中可能会产生气泡,所以数值预测的扬程普遍高于试验值。误差的大小与叶片数的多少有关系：叶片数越少,误差越大。5.首次将不等扬程水力设计方法应用于双叶片污水泵、自来水厂取水泵和核电站冷却水循环泵的水力设计,结果表明：(1)设计的双叶片污水泵水力性能很好,扬程曲线呈直线下降,无驼峰,高效区宽。(2)设计的自来水厂取水泵,在设计工况点效率达到最高值,最高效率η=85%,与KSB公司的同类产品效率η=82%相比,提高了3个百分点,效率指标达到国际先进水平。(3)设计的核电站冷却水循环泵水力模型效率高,换算到实型泵最高效率92.3%,额定点效率92%,高效区范围宽,效率指标达到同类泵的国际先进水平。更多还原

【Abstract】 Centrifugal pumps are widely used in agricultural irrigation, municipal works, light industry, chemical industry, construction, mining, metallurgy and other departments. With the development of society and technology, people bring forward higher requirements on the pump’s high efficiency, stability and low noise, and other aspects of the more stringent requirements. The hydraulic design methods widely used in centrifugal pump, is mainly based on the experience of Stepanoff similarity coefficient method based design. This method is characterized by a summary of the previous design and manufacturing experience, particularly the application of computer used in building a hydraulic model of the database, then, according to the required flow, head, choose a suitable specific speed hydraulic model from the database to design a similar pump to meet production needs. However, nowadays centrifugal pump operating point parameters (such as flow, head, etc.) increasingly requires high precision, the traditional unitary theory increasingly shows the deficiency of the design.Through the design research programs of three centrifugal pump with the same head, it’s found that the blade outlet flow of centrifugal pump is not ideal; using differ head design method, respectively, in three centrifugal pumps hydraulic design, Good blade export total pressure program were obtained good blade export total pressure, static pressure, static pressure and velocity distribution are obtained. CFD and numerical simulation technology is used in the two design methods for steady and unsteady numerical simulations, confirming the superiority of the design method for centrifugal pump blades. Finally Experimental studies and comparative analysis in the design of centrifugal pumps using differ head design method and equal head method is done, which further confirmed the correctness of the design theory of centrifugal pump impeller. In the paper, the research work and innovations are:1. Comprehensive and systematic analysis of the hydraulic design of centrifugal pumps Research and Development of methods at home and abroad, the traditional centrifugal pump for the hydraulic design of similar algorithms, the speed coefficient, area ratio principle, optimal design method, ternary theories were introduced describing a wide range of application progress of numerical simulation in the hydraulic design of centrifugal pumps, pointing out the current method of hydraulic design deficiencies, and presenting differ chordwis circulation design method in circulation areas such as fans and axial flow Research and Application.2. Differ head design method is introduced in centrifugal pump impeller hydraulic design for the first time. Through the study of traditional method of centrifugal pump hydraulic design,it has been found that the traditional method of hydraulic design of centrifugal impeller will lead to unsatisfactory flow in the blade outlet, while using differ head method in the design of centrifugal pump, can get a good blade outlet total pressure, static pressure and velocity distribution.3. CFD technology is used in the design of the centrifugal pump to analyze the steady and unsteady flow in the centrifugal pump designed by differ head method. In the steady calculation,static pressure of each model, absolute speed, relative speed, scroll speed and impeller outlet section of the pressure distribution before and after the cover were obtained, revealing the flow pattern inside the pump mode. Through analysis and comparison of differ design and equal head design of hydraulic performance, the advantages obtained by differ head method is obvious and according to the flow rate statistics in different models, forecast performance curve has been drawn, summarized the design of programs using differ head method was the best design model.The combination of unsteady numerical simulation verifies that impeller and volute due to the interaction between the flow in centrifugal pump shows a strong unsteady state, not onlye the flow of the impeller respectively passageway structure at the same time is differential, but also flow structure in the rotation process at the same passageway is also changing, and it shows a cyclical fluctuations, which causes that various locations along the circumferential volute exists in the periodic pressure fluctuation,pressure pulse amplitude and frequency the maximum amplitude of the P values corresponding to the main frequency the product of frequency and number of leaves and produce pressure fluctuation is the main factors resulting in pressure fluctuation.4. According to previous simulation results, the pump performance can be predicted, however, compared with the performance curve obtained through the outside performance test, we can also assess the accuracy of numerical simulation certainly to verify the reliability of numerical prediction. The main reason:It only contains the hydraulic efficiency rather than mechanical efficiency and volume efficiency of Predictive value, and the numerical simulation idealized the flow of centrifugal pump,but the actual operation can not be less than ideal and the actual operation may produce bubbles, Therefore, it generally higher than the predicted experimental head. The size of the error number is related with the number of leaf: The more of the leaves, the bigger of the error.5. Differ head hydraulic design method is applied to double- blades sewage pump,water plant and nuclear power plants cooling water circulation pumps for the first time, and the results show that:(1) design of double-blades hydraulic sewage pump has a good hydraulic properties, head curve linear decline, no hump, and efficient district wide. (2) water plant pumps, efficiency in the design of the highest operating point value, the maximum efficiencyη=85%, similar products with the efficiency of the company KSBη=82% compared to 3 percent increase, efficiency indicators reaches international advanced level. (3) nuclear power plant cooling water circulation pump hydraulic model has high efficiency. High pump conversion efficiency to the real pump is 92.3%, efficiency rating points is 92%, effective district is wide.And efficiency indicators have reached international advanced level of similar pumps.更多还原