叶顶开槽对冷却塔风机气动性能影响的数值研究

发布时间：2018-06-03 13:46

本文选题：轴流风机 + 数值模拟　；参考：《西安理工大学》2017年硕士论文

【摘要】：轴流风机具有成本低、适合大流量场合等优点,在焦化、钢铁、石油、热电等行业的机力通风冷却塔上广泛应用,是工业循环水系统中的第二大耗能设备。轴流风机运行效率的高低将直接决定风机能耗的大小,同时其气流脉动特性决定了风机部件及风筒的使用寿命。提高风机的效率、降低气流的脉动一直是国内外学者、企业的重要研究课题。本文以在机力通风冷却塔中广泛应用的LF92型风机作为研究对象,对其气动性能进行了现场实验,并采用三维数值模拟对风机进行了定常与非定常计算。研究表明,风机外特性的数值模拟结果与实验结果一致;实验及数值研究均表明,该风机存在运行效率较低,风筒处气流脉动强度较大的问题。针对上述问题,在总结国内外研究的基础上,本文通过在风机叶顶处开非通凹槽的方案对叶片进行改型,通过三维数值模拟研究了开槽系数k和凹槽深度h对风机性能的影响,开槽系数取0.3、0.5和0.75,开槽深度取3mm、5mm和8mm,共对比分析了 5种开槽方案。研究结果表明:风机叶顶开非通凹槽后,叶顶间隙内的湍流强度明显提高,在叶顶间隙内,靠近叶片位置出现了与泄漏流流动方向相反的二次流,并形成间隙涡降低了泄漏流的通过截面积,起到降低泄漏流流量的流动控制效果。通过对不同凹槽结构的对比,发现开槽系数对风机气动性能的影响大于开槽深度。在所有改型方案中,k为0.75、A等于5mm的流动控制方案最佳,叶顶间隙泄漏量较原型风机下降15.79%,输入功率下降5.49%,同时压力脉动最明显的监控点的主频幅值下降43%。为了进一步改善风机的气动性能,在上述研究基础上,将气动性能最优的k0.75h5非通凹槽模型改为非通单排篦齿模型,并进行了定常及非定常数值模拟。研究结果表明:篦齿型开槽的气动性能较k0.75 h5又有了明显的提升,输入功率较原型风机下降7.96%。由于间隙涡移动至叶顶间隙内靠近叶片压力面的位置,且间隙涡的湍动能强度增加,进一步增强了对泄漏流的控制效果,使泄漏量较原型风机下降19.74%,压力脉动最明显监控点的压力变化幅度、压力脉动强度及主频幅值下降超过90%,风机气动性能得到了进一步提高。
[Abstract]:Axial fan has the advantages of low cost and suitable for large flow situation. It is widely used in the mechanical ventilation cooling tower of coking, steel, oil and thermoelectric industries. It is the second big energy consumption equipment in the industrial circulating water system. The operation efficiency of the axial flow fan will directly determine the size of the wind power consumption, and the air pulsation characteristics determine the wind. The service life of the machine parts and the wind drum, improving the efficiency of the fan and reducing the pulsation of the air flow have been the important research subject of the domestic and foreign scholars and enterprises. In this paper, the LF92 fan, which is widely used in the mechanical ventilation cooling tower, is used as the research object, the aerodynamic performance is tested in the field, and the three dimensional numerical simulation is used to carry out the fan. The results of numerical simulation show that the numerical simulation results of the external characteristics of the fan are in agreement with the experimental results. Both the experimental and numerical studies show that the fan has a low operating efficiency and a larger air flow pulsating intensity in the wind tunnel. On the basis of the above problems, the paper is open to the top of the fan at the top of the fan. The groove is modified to the blade. Through the three-dimensional numerical simulation, the influence of the slot coefficient K and the groove depth h on the fan performance is studied. The slotting coefficient is 0.3,0.5 and 0.75, the slotting depth is 3mm, 5mm and 8mm. A total of 5 slotting schemes are compared and analyzed. The results show that the turbulence intensity in the blade tip clearance after the blower leaves are open. In the tip clearance, the two flow which is opposite to the flow direction of the leakage flow is found near the blade tip clearance, and the clearance vortex is formed to reduce the passage area of the leakage flow and to reduce the flow control effect of the leakage flow. By comparing the different groove structures, it is found that the effect of the slot coefficient on the aerodynamic performance of the fan is greater than that of the blade. In all modification schemes, the flow control scheme with K 0.75 and A equal to 5mm is the best, the leakage of the tip clearance is 15.79%, the input power is decreased by 5.49%, and the main frequency amplitude of the monitoring point is decreased by 43%. to further improve the aerodynamic performance of the fan. On the basis of the above study, the aerodynamic performance will be carried out. The performance of the k0.75h5 non pass groove model is changed to the non pass single grate tooth model, and the steady and unsteady numerical simulation is carried out. The results show that the aerodynamic performance of the labyrinth slotting is significantly higher than that of the k0.75 H5, and the input power is lower than the prototype fan because the gap vortex moves to the blade pressure surface in the gap of the top of the blade. With the increase of the turbulent kinetic energy intensity of the gap vortex, the control effect on the leakage flow is further enhanced. The leakage is reduced by 19.74% than that of the prototype fan. The pressure fluctuation of the pressure pulsation is most obvious, the pressure fluctuation intensity and the main frequency amplitude decrease by more than 90%, and the aerodynamic performance of the fan is further improved.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH43

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