本文選題：軸流風機 + 數(shù)值模擬��； 參考：《西安理工大學》2017年碩士論文

【摘要】：軸流風機具有成本低、適合大流量場合等優(yōu)點,在焦化、鋼鐵、石油、熱電等行業(yè)的機力通風冷卻塔上廣泛應用,是工業(yè)循環(huán)水系統(tǒng)中的第二大耗能設備。軸流風機運行效率的高低將直接決定風機能耗的大小,同時其氣流脈動特性決定了風機部件及風筒的使用壽命。提高風機的效率、降低氣流的脈動一直是國內外學者、企業(yè)的重要研究課題。本文以在機力通風冷卻塔中廣泛應用的LF92型風機作為研究對象,對其氣動性能進行了現(xiàn)場實驗,并采用三維數(shù)值模擬對風機進行了定常與非定常計算。研究表明,風機外特性的數(shù)值模擬結果與實驗結果一致;實驗及數(shù)值研究均表明,該風機存在運行效率較低,風筒處氣流脈動強度較大的問題。針對上述問題,在總結國內外研究的基礎上,本文通過在風機葉頂處開非通凹槽的方案對葉片進行改型,通過三維數(shù)值模擬研究了開槽系數(shù)k和凹槽深度h對風機性能的影響,開槽系數(shù)取0.3、0.5和0.75,開槽深度取3mm、5mm和8mm,共對比分析了 5種開槽方案。研究結果表明:風機葉頂開非通凹槽后,葉頂間隙內的湍流強度明顯提高,在葉頂間隙內,靠近葉片位置出現(xiàn)了與泄漏流流動方向相反的二次流,并形成間隙渦降低了泄漏流的通過截面積,起到降低泄漏流流量的流動控制效果。通過對不同凹槽結構的對比,發(fā)現(xiàn)開槽系數(shù)對風機氣動性能的影響大于開槽深度。在所有改型方案中,k為0.75、A等于5mm的流動控制方案最佳,葉頂間隙泄漏量較原型風機下降15.79%,輸入功率下降5.49%,同時壓力脈動最明顯的監(jiān)控點的主頻幅值下降43%。為了進一步改善風機的氣動性能,在上述研究基礎上,將氣動性能最優(yōu)的k0.75h5非通凹槽模型改為非通單排篦齒模型,并進行了定常及非定常數(shù)值模擬。研究結果表明:篦齒型開槽的氣動性能較k0.75 h5又有了明顯的提升,輸入功率較原型風機下降7.96%。由于間隙渦移動至葉頂間隙內靠近葉片壓力面的位置,且間隙渦的湍動能強度增加,進一步增強了對泄漏流的控制效果,使泄漏量較原型風機下降19.74%,壓力脈動最明顯監(jiān)控點的壓力變化幅度、壓力脈動強度及主頻幅值下降超過90%,風機氣動性能得到了進一步提高。
[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.
【學位授予單位】：西安理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH43

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