【作者】 马静先；

【导师】 杨军虎；

【作者基本信息】 兰州理工大学 ， 流体机械与工程， 2007， 硕士

【摘要】 轴流泵叶轮叶顶间隙的大小，叶轮叶片外缘的几何形状及间隙内流场分布是影响轴流泵效率、空化余量的重要因素之一，也关系到轴流泵安全可靠运行。本文首先对国产定型产品ZQ287OC-4型轴流式潜水泵，通过改变泵壳外径的方法取得七种不同的叶轮叶顶间隙值：0mm、0.65mm、1mm、1.5mm、2mm、3mm、5mm。在设计工况下（Q=1.85m³／s，H=9.19m，n=735r／min）利用FLUENT6.1软件，采用标准κ-ε双方程紊流模型和SIMPLE算法，对不同叶顶间隙值下的流道内部流场进行了计算。通过分析计算结果发现：1)叶片背面、叶片顶面是受间隙流场影响最严重的区域；2)间隙内部低压中心随着叶轮叶顶间隙值增大沿叶片外缘向叶轮出口方向转移；3)间隙内轴向速度沿叶轮外缘弦长方向分布不一致，泄露流动最严重的区域在叶轮外缘15％-20％轴向弦长处；4)通过对间隙内轴面流场进行分析，观察到了泄漏涡的形成与发展；当间隙值增大到5mm（0.77％D₂）时，间隙内部出现旋涡；5)利用计算结果对泵的扬程和水力效率做了预测，发现扬程和水力效率均随间隙值增大而下降；在叶轮叶顶间隙取值不大于1.5mm即0.23％D₂，该泵的扬程和水力效率下降不大。因此当仅考虑扬程和水力效率时，推荐叶轮叶顶间隙取值在此范围内，此值比设计手册推荐值稍大。其次，以1.5mm叶轮叶顶间隙值为例，研究了修圆叶轮叶片外缘在改善间隙流场方面的作用。根据设计、运行经验，分别以两倍间隙值、叶片外缘厚度一半、叶片外缘厚度三分之二为半径修圆叶片工作面外缘：在修圆叶片工作面外缘基础上尝试了修圆叶片背面外缘。结果表明以两倍叶顶间隙值为半径修圆叶片工作面外缘能提高间隙内最低压力，降低了间隙空化空蚀发生的可能性；另外，此种修圆方案下叶轮水力效率比其它修圆方案高。因此建议采用以间隙值的两倍为半径修圆叶片工作面外缘，以达到降低间隙空化空蚀发生的目的。为了验证数值模拟的准确性，分别计算了该泵在不同流量下的扬程。计算值和实验值比较发现在0.8-1.2Q_d（设计流量）范围内误差小于6％。由此说明数值模拟结果较准确。更多还原

【Abstract】 The value of axial flow pump’s tip clearance, the shape of blade tip and the flow in the blade tip clearance have great influence on the efficiency of axial flow pump and even affect its running.First, select the product of submersible axial flow pump ZQ2870C-4 as the study object. And get seven kinds of pump models with different tip clearance gap width by changing the diameter of the pump casing. The value of tip clearance is as follow:0mm、 0.65mm、 1mm、 1.5mm、 2mm、 3mm 、 5mm. The standard k-e turbulence model and SIMPLE algorithm are applied to analyze the flow passage of the pump at design condition （Q=1.85m³/s,H=9.19m,n=735r/min） under different schemes by FLUENT6.1 in this thesis. The result indicates that: 1) The tip clearance flow has great influence on the surface of suction and blade tip; 2) The center of low pressure in the tip area moves to the outlet of the pump through the blade tip with the tip clearance enhance; 3) Axial velocity distribution shows that the tip clearance leakage flow is asymmetric and the worst leakage flow area is at 15%-20% chord of the blade tip; 4) The analysis on the flow of axial plan indicates the development of leakage vortex. And when the clearance gap width reaches to 5mm（0.77%D2） there appears vortex in the tip clearance; 5) The head and hydraulic efficiency are forecasted and the results indicate that the head and hydraulic efficiency decline with the tip clearance enhancing. But the head and hydraulic efficiency don’t decline too much when the tip clearance is not large than 1.5mm（0.23%D₂） . So the tip clearance is suggested not larger than 0.23%D₂ which is a little big than the value recommended in the design manual.Then, the submersible axial flow pump with tip clearance of 1.5mm is adopted to study the interior flow by smoothing the blade tip. According to the experience four kinds of smoothing schemes are adopted. The smoothing radius includes double of the tip clearance width, half of the blade flange thickness and two-thirds of the blade flange thickness. The results indicate that smoothing the pressure side flange can improve the tip clearance flow condition and reduce the property of gap cavitation. And under this scheme the hydraulic efficiency is the best. So the best smoothing scheme is choosing the double thickness of the tip clearance width to smooth the pressure side of the blade.This pump’s head at different flowrates are calculated to analyze the veracity ofnumerical simulation. It is found that the error is less than 6% compared with the experiment results under 0.8-1.2Q_d （design flowrate）. This result indicates the result of numerical simulation is acceptable.更多还原