發(fā)布時間：2018-05-23 14:17

  本文選題：氣液分散 + 攪拌槳設(shè)計��； 參考：《江南大學(xué)》2017年碩士論文

【摘要】：很多涉及氧化反應(yīng)或氫化反應(yīng)的過程都需要用到氣液分散攪拌槳,如生物發(fā)酵過程中需要維持一定量空氣以滿足微生物對氧的需求。徑向流攪拌槳是應(yīng)用最廣泛的氣液分散攪拌槳,是通氣式機械攪拌罐中的關(guān)鍵裝置,也是攪拌系統(tǒng)中的主要耗能部件。隨著工業(yè)生產(chǎn)規(guī)模擴大以及能源逐漸短缺,設(shè)計開發(fā)一種低功耗、高效率的新型氣液分散攪拌槳變得尤為重要。本文通過理論分析、計算流體力學(xué)(CFD)模擬和實驗測試相結(jié)合的手段設(shè)計開發(fā)一種新型氣液分散攪拌槳,并對其進(jìn)行性能表征。通過CFD模擬分析平直葉槳(RT)、半圓弧槳(CD)和非對稱拋物線形槳(BT)三種傳統(tǒng)徑向流攪拌槳結(jié)構(gòu)和性能特點,發(fā)現(xiàn)其演化趨勢是功率準(zhǔn)數(shù)更低、泵送效率更高、軸向覆蓋面積更大。同時研究不同槳葉外緣結(jié)構(gòu)和尺寸對攪拌性能的影響,結(jié)果表明槳葉外邊緣頂點曲率增大可減小功率準(zhǔn)數(shù)和提高泵送效率,軸向高度減小可使功率準(zhǔn)數(shù)減小但對泵送效率提升不明顯。然后提出新穎的扇環(huán)拋物面形槳葉結(jié)構(gòu)設(shè)計,發(fā)現(xiàn)裝配該槳葉的扇環(huán)形攪拌槳(FT)表現(xiàn)出最佳操作性能,與傳統(tǒng)槳中效果較好的非對稱拋物線形槳(BT)相比,其功率準(zhǔn)數(shù)下降30.8%,泵送效率提高22.6%,軸向投影面積率增加21.5%,具有應(yīng)用于氣液操作時高效傳質(zhì)的潛力�；�3D打印技術(shù)加工制作新型FT槳和工業(yè)上常用的氣液分散攪拌槳RT和BT。實驗測試新型FT槳在通氣條件下操作性能,并與另外兩種攪拌槳對比。結(jié)果表明:FT槳功率準(zhǔn)數(shù)較低,為1.7左右;相對功率需求(RPD)更高,高轉(zhuǎn)速攪拌時接近1.0;臨界分散轉(zhuǎn)速比BT略低,明顯高于RT;氣含率和體積傳質(zhì)系數(shù)與BT相近,均高于RT;FT槳氧傳質(zhì)效率明顯高于RT和BT,約比RT提升40~70%,比BT提升17~40%。使用粒子成像測速技術(shù)(PIV)測試流場速度,并結(jié)合其他實驗數(shù)據(jù)驗證所建立CFD計算模型可靠性。然后基于CFD手段分析新型FT槳的微觀特性,并在相同條件下同RT和BT對比。結(jié)果表明:FT槳速度分布規(guī)律與BT槳相近,不同于RT槳;在大部分位置上,FT槳的流場速度、剪切力、湍動能和湍動能耗散率的值均小于RT槳,但FT槳特性參數(shù)值分布更加均勻,BT槳特性介于RT槳和FT槳之間。通過氣液兩相流模擬得到,BT槳流場中氣泡數(shù)量最多,FT槳次之,RT槳最少,但FT槳流場中的小尺寸氣泡占比最高。
[Abstract]:Many processes involving oxidation or hydrogenation require the use of gas-liquid dispersed agitators, such as maintaining a certain amount of air during biological fermentation to meet the oxygen requirements of microorganisms. Radial flow impeller is the most widely used gas-liquid dispersed agitator. It is the key device in the aerated mechanical agitator and the main energy consuming part in the mixing system. With the expansion of industrial production and the gradual shortage of energy, it is particularly important to design and develop a new type of gas-liquid dispersed agitator with low power consumption and high efficiency. In this paper, a new type of gas-liquid dispersed agitator is designed and developed by theoretical analysis, computational fluid dynamics (CFD) simulation and experimental test, and its performance is characterized. The structure and performance characteristics of three kinds of traditional radial flow impellers are analyzed by CFD simulation. It is found that the evolution trend is lower power criterion, higher pumping efficiency and larger axial coverage area. At the same time, the influence of the structure and size of the outer edge of the blade on the agitation performance is studied. The results show that the increase of the curvature of the outer edge of the blade can reduce the power standard number and improve the pumping efficiency. The decrease of axial height can reduce the number of power standards, but it can not improve the pumping efficiency obviously. Then a novel structural design of the fan ring paraboloid propeller blade is proposed. It is found that the fan annular impeller (FTF) assembled with the blade exhibits the best operating performance, compared with the asymmetric parabola propeller (BTT), which has a better effect in the traditional propeller. Its power standard number is reduced by 30.8, pumping efficiency is increased by 22.6and axial projection area ratio is increased by 21.5. it has the potential of high efficiency mass transfer in gas-liquid operation. Based on 3D printing technology, a new type of FT propeller and gas liquid dispersed agitator RT and BT are fabricated. The operating performance of the new FT propeller under aeration condition was tested and compared with the other two kinds of impellers. The results show that the power standard number of the rotor is lower (about 1.7), the relative power demand is higher, the critical dispersion speed is slightly lower than BT, and the volume mass transfer coefficient is close to BT, the critical dispersion speed is slightly lower than BT, and the volume mass transfer coefficient is close to BT. The oxygen mass transfer efficiency was significantly higher than that of RT and BTT, about 40 / 70 than RT and 17 / 40 than BT. The particle imaging velocimetry (PIV) is used to measure the velocity of the flow field, and the reliability of the established CFD model is verified by other experimental data. Then the microcosmic characteristics of the new FT propeller are analyzed based on CFD and compared with RT and BT under the same conditions. The results show that the velocity distribution of the rotor is similar to that of BT propeller and is different from that of RT propeller, and the velocity of flow field, shear force, turbulent kinetic energy and turbulent kinetic energy dissipation rate of FT propeller are all smaller than those of RT propeller in most positions. However, the characteristics of FT propeller are more uniform and the characteristics of BT propeller are between RT propeller and FT propeller. Through the simulation of gas-liquid two-phase flow, it is found that the number of bubbles in the flow field of BT propeller is the most, and that of FT propeller is the least, but the fraction of small bubble is the highest in the flow field of FT propeller.
【學(xué)位授予單位】：江南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ051.72

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