大型低扬程泵优化设计及内部流动特性研究

发布时间：2018-01-15 12:08

本文关键词：大型低扬程泵优化设计及内部流动特性研究　出处：《江苏大学》2015年博士论文　论文类型：学位论文

【摘要】：能源问题是当今全球普遍关注的问题,也是发展国民经济,改善国民生活水平的重要物质基础。据不完全统计,泵的耗电量约占全国总发电量的17%。因此提高泵的设计水平对构建环境友好型,资源节约型社会的作用显著。低扬程泵站在长江中下游平原、黄淮海平原、东北平原和珠江三角洲等经济发达地区的水资源调配、水环境改善、城市防洪和灌溉排水等领域应用广泛,对提高防御自然灾害的能力、促进我国社会经济的快速和可持续发展发挥了重要作用。我国低扬程泵站的总量及规模居世界第一,每年消耗的电能相当可观。在能源日益紧张的今天,进一步提高低扬程泵装置的效率对降低泵站运行成本和节能减排具有十分重要的意义。大型低扬程立式泵相对于其它类型的泵有如下优点：1)叶轮淹没在水里,有利于保证不发生空化；2)启动时不必灌引水(排气),上水快,有利于实现自动运行；3)占地面积小。虽然离心泵的水力性能好,但结构复杂。因此除在各个泵站应用于生产外,轴流泵和混流泵也广泛应用于经济社会各个领域中。轴流泵的叶间匹配问题严重影响到泵的性能,应进一步通过研究轴流泵导叶体与叶轮的流场优化匹配来提高泵的性能,但从水泵的平稳运行、空化以及效率等不同方面综合考虑,轴流泵的高效区不够宽广,不能适用于扬程变化较大的场合。相对于轴流泵,混流泵不仅高效区较宽,并且具有流量、扬程变化范围大,运行稳定等特点,是一种较为理想的泵型。本文采用理论分析、数值模拟计算以及模型试验等方法研究了低扬程轴流的导叶体与叶轮的流场优化匹配问题,同时也优化设计出了一台高比转数双蜗壳式混流泵,并对混流泵模型进行了非定常压力脉动特性研究、流动诱导噪声分析以及空化特性预测。本文的主要研究工作及创新性成果有：1、提出并解决了轴流泵导叶体与叶轮的流场优化匹配问题,创造性地将导叶体的导叶片分为进口段、中段和出口段3个部分,中段和出口段固定,起到固定支撑水泵导轴承座的作用。2、首次提出轴流泵导叶片进口段进口角度可调,实现与叶轮叶片出口水流流场的匹配,以减小导叶进口在非设计工况下的冲击损失；研究了轴流泵导叶片进口角度对泵装置水力性能的影响规律。导叶片进口角度的改变影响到导叶体内的流态及其水力损失,从而影响到泵装置的能量性能；在轴流泵导叶片原设计进口角度的基础上,沿顺时针方向旋转适当角度,可扩大低扬程泵装置高效运行的范围,显著提高偏离设计工况点的低扬程、大流量区的效率。3、首次开发了一台高性能的双蜗壳混流泵水力模型。通过对优化前后的混流泵模型进行数值模拟,结果表明最终所采用的双蜗壳结构的混流泵其内部流态优于优化前的单蜗壳结构的混流泵,并且双蜗壳混流泵的径向力也比单蜗壳的小,这也说明相对单蜗壳结构,优化后的双蜗壳混流泵水力模型具有一定的优越性。然后将双蜗壳混流泵模型加工成实体,进行外特性试验,试验结果与数值模拟的结果吻合程度较高,表明本文在优化过程中采用的数值计算方法的准确性,为双蜗壳混流泵的非定常压力脉动特性研究、流动诱导噪声分析以及空化特性预测提供了技术支撑。4、首次对混流泵内部在不同工况下的压力脉动特性进行了研究。对混流泵在不同工况下分别进行了非定常数值计算,分析了混流泵内部不同位置监测点的压力脉动特性,研究表明：混流泵叶轮进出口压力脉动幅值均是沿着轮毂到轮缘呈逐渐递增的趋势,对于轮缘部位进行优化是改善混流泵内压力脉动的关键；混流泵的进口压力脉动幅度最大,进口部位是影响机组稳定运行的关键,在混流泵水力设计过程中应予以重视；叶轮出口和蜗壳隔舌处压力脉动最大。沿着蜗壳周向,蜗壳隔舌处由于受到蜗壳和叶轮的动静干涉作用,此处压力脉动最大,随着监测点远离隔舌,各点的压力脉动逐渐减小,受动静干涉的影响也逐步减弱；蜗壳内侧流道的压力脉动幅度高于外侧；不同工况下,混流泵各处的压力脉动主频均为叶频,大流量工况下各监测点压力脉动幅值较小；叶轮出口处以及蜗壳隔舌处由于受到动静干涉作用,其压力脉动频域特性比较复杂,相对于其它部位,这两处压力脉动高频成分比较明显。5、首次采用基于CFD/CA的方法对混流泵在不同工况下由叶片旋转偶极子源作用的噪声进行了研究。结果表明：混流泵叶轮和蜗壳隔舌部位的动静干涉作用是混流泵流动诱导噪声的主要来源；压力脉动的主频与外场噪声的主频并不一致,压力脉动的主频对于噪声的辐射水平有影响但不能直接决定其大小,混流泵的结构振动模态对于噪声辐射水平也起着关键作用,尤其是当泵体的固有频率与压力脉动主频相接近时,容易引起共振,会导致外场噪声辐射值的明显增加；流量对于噪声的指向性几乎无影响,但是对于噪声的辐射能力影响比较明显,小流量工况下(0.8 Qd)噪声辐射能力最强,设计工况(Qd)次之,大流量工况下(1.29)噪声辐射能力最弱,这与非定常压力脉动研究所得到的随着流量的增大,压力脉动幅值逐渐减小的结论相吻合,说明不同工况下压力脉动的幅值对噪声的辐射水平有着直接的影响,这对研究混流泵内部压力脉动对于流动噪声影响的研究具有参考作用。6、研究了空化工况下混流泵扬程下降的机理,获得了混流泵叶轮内的空化现象初步规律。对泵空化的基本参数以及空化余量的测量作了分析,然后通过CFD技术对混流泵的模型进行了空化特性预测,初步揭示了空化工况下混流泵扬程下降的机理：混流泵叶轮内的空化现象最初发生在叶轮流道进口处偏向轮缘一侧,随着空化余量的降低,叶片背面靠近轮缘处开始出现空化,该空化区域从轮缘向轮毂方向延伸,并且逐渐向叶片中部扩散,在空化严重时,空化会对叶轮流道流体的正常流动造成堵塞,导致混流泵扬程的下降。
[Abstract]:The energy problem is a worldwide problem, but also the development of the national economy, improve the important material basis of the national standard of living. According to incomplete statistics, the power consumption of the pump of the total generating capacity of 17%. and improve the design level of the pump to build environment-friendly and resource-saving society. The role of low lift pumping stations downstream in the Yangtze River Plain, North China Plain, the allocation of water resources in economically developed areas of Northeast Plain and the Pearl River Delta, to improve the water environment, the application of city flood control and irrigation drainage and other fields widely, to improve the ability of preventing natural disasters, has played an important role in promoting the rapid and sustainable development of social economy in China. The total scale and I in low lift pumping stations ranked first in the world, the annual consumption of electricity is considerable. In today's increasingly tense energy, to further improve the efficiency of low lift pump system to reduce It is of great significance to the cost of pumping operation and energy saving of large low lift vertical pump. Compared with other types of pumps have the following advantages: 1) impeller submerged in the water, to ensure that no cavitation; 2) start without irrigation water (exhaust), fast water, conducive to the realization of automatic operation; 3) small area. Although the hydraulic performance of centrifugal pump, but the structure is complex. Therefore except in various pumping stations used in production, axial and mixed flow pump is widely used in economic and social fields. The axial flow pump blade matching problems seriously affect the performance of the pump, should be further studied by axial flow pump guide vane and impeller flow field optimization, to improve the performance of the pump, but the smooth operation of the pump, cavitation and efficiency from the aspects of comprehensive consideration, high efficiency of axial flow pump is not wide enough, not suitable for large changes in the relative lift occasion. In the axial flow pump, mixed flow pump not only high efficiency area is wide, and has a large range of flow, lift, stable operation characteristics, is an ideal type of pump. By theoretical analysis, numerical simulation and model test method of low lift axial guide vane and impeller matching problem flow field optimization, also designed a high speed double volute mixed flow pump, and the mixed flow pump model of unsteady pressure fluctuation characteristics of the flow induced noise, analysis and prediction of cavitation performance. The main research work and innovative achievements are: 1, put forward and solved the axial flow pump vane and impeller, guide vane flow field optimization problems, creatively divided into the guide vane inlet section, 3 middle part and the outlet section, middle section and exit section is fixed, play the role of the.2 fixed support pump guide bearing for the first time. The axial flow pump inlet guide vane inlet angle adjustable, matching and impeller blade outlet flow, to reduce the impact loss of guide vane inlet in non design conditions; Study on influence of axial flow pump of guide vane inlet angle on the hydraulic performance of pump system. Influence of guide vane inlet angle to guide flow pattern and hydraulic loss in leaf, which affects the energy performance of the pump device; based on the original design of the guide vane inlet angle of axial flow pump, clockwise the appropriate angle, can expand the efficient operation of low lift pump system range, significantly improve the low head deviation from the design point, the efficiency of.3 flow area, double volute mixed flow pump hydraulic model was developed for the first time a high performance. By numerical simulation of mixed flow pump model before and after the optimization. The results show that the double volute mixed flow structure of the final Mixed flow pump with single volute pump internal flow structure is better than before optimization, and the radial force of the double volute mixed flow pump is better than single scroll, which also shows that the relative single volute structure, double volute mixed flow pump hydraulic model after optimization has certain advantages. Then the double volute mixed flow pump model processing entity. External characteristic test, test results and numerical simulation results show that the accuracy degree is high, the numerical calculation method in the optimization process by the study of unsteady pressure pulsation characteristics for double volute mixed flow pump, induced by noise analysis and prediction of cavitation flow and provides technical support for the first time on.4, pressure fluctuation the internal mixed flow pump under different working conditions were studied. The mixed flow pump under different working conditions were unsteady numerical calculation, analysis of different monitoring point of mixed flow pump internal pressure The research shows that: the pulse characteristics of mixed flow pump impeller inlet and outlet pressure pulsation amplitude is the hub to the rim was gradually increasing trend for flange optimization is a key to improve the pressure pulsation in the mixed flow pump; mixed flow pump inlet pressure pulsation amplitude is maximum, the import department key influence the stable operation of the unit should be paid attention to. In the mixed flow pump hydraulic design process; the outlet of impeller and volute tongue. The maximum pressure fluctuation along the volute circumferential, volute tongue due to impeller and volute rotor stator interaction, the maximum pressure fluctuation, with the monitoring point away from the tongue, the pressure fluctuation decreases, affected by the interference of movement gradually weakened; the pressure pulsation amplitude of volute flow above the lateral side; under different conditions, the pressure pulsation frequency of mixed flow pump are all Ye Pin, the large flow rate condition monitoring The pressure fluctuation amplitude is smaller; the outlet of impeller and volute tongue due to rotor stator interaction, the pressure fluctuation frequency characteristics is more complex, relative to other parts, the two pressure pulsation frequency components were.5, for the first time using CFD/CA method based on the noise of mixed flow pump under different operating conditions by the blade rotating dipole source were studied. The results showed that the mixed flow pump impeller and volute tongue position of the rotor stator interaction is the main source of noise induced by mixed flow pump; frequency frequency and field noise of pressure fluctuation is not consistent, the frequency of pressure fluctuation influence but not directly determines the size of the radiation level of noise, modal Francis the pump for the noise radiation also plays a key role, especially the natural frequency and pressure pulsation frequency when the pump body is close, easy to cause The resonance will lead to significant increase of noise emission values of flow field; for the directivity of the noise almost no effect, but the ability of radiation noise impact is more obvious, the small flow rate condition (0.8 Qd) the strongest radiation noise, the design condition (Qd) of the large flow rate condition (1.29) noise radiation weakest this, and the unsteady pressure fluctuation by the study along with the increase of flow rate decreases, the pressure fluctuation amplitude is consistent with the conclusion, that has a direct impact on the level of radiation amplitude of pressure fluctuation under different conditions of noise, the internal pressure pulsation of mixed flow pump with reference for the study of flow noise.6 study on the mechanism of cavitation conditions, mixed flow pump head drop, obtained preliminary rules of cavitation of mixed flow pump impeller. The basic parameters of the pump cavitation and cavitation measurement are analyzed Then, through the model of CFD technology on the mixed flow pump of the cavitation prediction, reveal the mechanism of cavitation conditions of mixed flow pump head drop: cavitation phenomenon of mixed flow pump impeller in the first impeller inlet bias occurs in the rim side, with the decrease of the cavitation, the back of the blade near the rim began to cavitation, the cavitation the regional hub extending to the direction from the rim, and gradually spread to the central leaves, in serious cavitation, cavitation will normally flow on the impeller fluid cause blockage, resulting in a decline in head mixed flow pump.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH31

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