蜷曲式虹吸出水流道泵装置水力特性及优化

发布时间：2018-03-30 20:21

本文选题：数值模拟　切入点：泵装置　出处：《扬州大学》2017年硕士论文

【摘要】：泵站出水流道是泵站工程水工建筑物重要组成部分,对于低扬程的立式轴流泵装置,虹吸出水流道具有断流方式简单、水头损失较小等特点,因此在立式轴流泵装置的泵站工程设计中出水流道常采用虹吸出水流道。本文原泵装置模型是以某大型泵站泵装置模型为原型,其采用的出水流道形式为蜷曲式虹吸出水流道,能够较好的适应当地的地形条件,缩短了泵站纵向长度,从而节省了土建投资,具有较好的站身稳定性。目前,国内外对于蜷曲式虹吸出水流道的研究并不多,所以对该种类型的出水流道的水力特性还有待深入了解。本文采用CFX软件,对原泵装置模型进行数值模拟,计算结果表明:原泵装置模型进水流道轴向流速均匀度较高,流线平顺,但是出水流道流线整体较为紊乱,存在多处漩涡;其出水流道的水头损失主要来源于弯管段产生的水头损失;水流经过出水流道由于涡动能的回收,涡量逐步减小,但是流经出口附近时截面平均涡量有所增加,主要由于出水流道出口附近存在漩涡所致;对原泵装置模型进行外特性预测,将预测的结果与试验数据进行对比,两者整体趋势基本一致,在小流量工况下,预测结果比模型试验数据扬程略微偏小、效率稍微偏高,且差值很小,在设计工况附近及大流量工况高度吻合,表明计算结果可信。针对原泵装置模型出水流道存在的问题进行优化,根据各截面中心之间的距离与截面面积的分布关系,发现原泵装置模型出水流道出口截面明显偏大,可以通过抬高出水流道出口底部高程,从而减小出口截面的面积、改善流态、提高泵站运行的效率,同时可以减少工程量。针对原泵装置模型出水流道下降段进行优化,优化方案1的出水流道下降段流态得到了明显的改善,各典型截面的平均涡量降低,出水流道水头损失降低,出水流道出口截面的轴向流速均匀度提高13个百分点以上,泵装置运行效率在各个工况下,较原泵装置模型提高了 0.19个百分点至2.05个百分点,高效区明显拓宽。对出水流道整体进行进一步优化,改变原泵装置模型驼峰段截面面积,保证了出水流道各截面中心之间的距离与截面面积呈近似线性分布,优化方案2很好的消除了原泵装置模型出水流道存在的多处漩涡,各典型截面的平均涡量得到了进一步的降低,出水流道的水头损失在各个工况下减少0.03m以上,出水流道出口截面的轴向流速均匀度达到了 88%左右,提高了 18个百分点左右,泵装置运行效率在各个工况下,较原泵装置模型提高了 0.23个百分点至3.64个百分点,其中在在大流量工况下,效率提高最为明显。研究了来流扰动对进、出水流道流态和水泵性能的影响,由于机组不对称运行,水流不能平顺的流入进水流道,通过水力特性的对比,来流扰动情况下,进水流道进口截面流态变差,进水流道出口截面轴向流速均匀度有所降低,受其影响原泵装置运行的效率在各个工况下下降了 0.26个百分点至1.24个百分点。出水流道的流态同样受到了影响,相较于原泵装置模型更加紊乱,漩涡范围扩大,各典型截面的平均涡量增大,进、出水流道及泵段水头损失都有所增加,出口截面轴向流速均匀度降低。在泵站的实际运行过程中应尽量避免机组的不对称运行、侧向进水等来流扰动的发生。
[Abstract]:The outlet passage of pumping station is an important part of hydraulic engineering buildings, for low lift vertical axial flow pump, siphon flow props flow mode is simple, the characteristics of small head loss, so the water flow channel is often used in the siphon outlet conduit of pumping station engineering vertical axial-flow pump system design. The original pump device model is a large pump system model as the prototype, the outlet form curled type siphon outlet conduit, can adapt to the local terrain conditions, shorten the length so as to save the station, soil construction investment, has got good stability. At present, the domestic and foreign research on curled type siphon outlet conduit not much, so the hydraulic characteristics of the outlet of this type have to be understood deeply. This paper uses CFX software to simulate the original pump device model, the calculation results Show that the pump model of inlet axial velocity of high evenness, streamline smooth, but the overall outlet streamline is disorder, the existence of multiple vortex; head loss of head loss comes mainly from the outlet pipe section; water flows through the discharge passage due to eddy kinetic energy recovery, the vorticity decreases gradually, but through the near the exit section average vorticity increased, mainly due to the vortex caused by near outlet for export; characteristic prediction of the original pump device model, comparing the prediction results with the experimental data, both overall trend is basically the same, in the small flow rate condition, the prediction results than the model test data of head is slightly smaller, efficiency slightly higher, and the difference is very small, highly identical near the design condition and large flow condition, the calculation results show that the trusted. Aiming at the outlet of the pump device model The problem is optimized according to the distribution relation between distance and sectional area between the center of the section, found that the original pump model of outlet outlet section is too large, can raise through the outlet outlet bottom elevation, thereby reducing the export section of the area, improve the flow, improve the efficiency of pumping station operation, and can reduce the quantity of the original. Pump model of outlet descending optimization, optimization scheme of 1 outlet decline pattern has been significantly improved, the average vorticity of the typical cross-section decreases the amount of water flow, head loss is reduced, the axial velocity of outlet outlet uniformity increased by 13 percentage points, the efficiency of the pumping system under different operating conditions, an increase of 0.19 percentage points to 2.05 percentage points higher than the original pump device model, high efficiency significantly widened. Further optimization of the whole outlet, change the original Pump model of hump section area, the distance and the sectional area between the outlet section of each center is approximately linear distribution, optimization scheme 2 is eliminated more than the original vortex pump model of outlet conduit, the average amount of each typical section vortex has been further reduced, the head loss of the passage reduced by more than 0.03m in different conditions, the axial velocity of outlet outlet uniformity reached about 88%, an increase of 18 percentage points or so, the efficiency of the pumping system under different operating conditions, compared with the original pump model increased by 0.23 percentage points to 3.64 percentage points, which in the large flow rate condition, improve efficiency the most obvious. The flow disturbance on research, affect the water flow and pump performance, because the unit asymmetric operation, water can not be smooth into the inlet, through the hydraulic characteristics By contrast, flow disturbance, inlet inlet flow variation, inlet outlet axial velocity evenness decreased, affected by the efficiency of the original pump operation in different conditions decreased by 0.26 percentage points to 1.24 percentage points. The flow state of outlet conduit was also affected, compared to the original vortex pump device model more disorder, expand the scope of the mean vortex of the typical cross-section quantity increases, outlet and pump head loss increased, outlet axial velocity uniformity decreases. In the actual operation of the pumping station in the process should try to avoid the asymmetric operation of the unit, etc. the side inlet flow perturbation.

【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV136.2

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