本文選題：自激振蕩射流　切入點：湍流混合　出處：《大連海事大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：優(yōu)化噴嘴結(jié)構(gòu),改善摻混性能,不僅具有深刻的科學(xué)意義,而且對于工業(yè)燃燒器、混合器、反應(yīng)器等設(shè)備研發(fā)具有重要的指導(dǎo)價值。流體射入特定結(jié)構(gòu)的突擴腔體會發(fā)生整體低頻振蕩,稱為自激振蕩射流。在歐美眾多工業(yè)應(yīng)用結(jié)果表明,相比于傳統(tǒng)多射流燃燒器,自激振蕩射流燃燒器可降低NOx排放30%-50%,燃料消耗減少5%-10%。為了進一步優(yōu)化自激振蕩射流燃燒器性能,本文對矩形自激振蕩射流進行了實驗研究。首先,研究矩形自激振蕩射流的流動特性。通過絲帶曝光實驗、熱線實驗和煙線實驗,測量了不同腔體長度和不同矩形孔口長寬比條件下的射流擴散角、速度場和流場結(jié)構(gòu)。研究發(fā)現(xiàn)：長寬比越大,矩形射流二維性越強,越容易產(chǎn)生自激振蕩,但是當(dāng)矩形短邊與腔體壁面足夠接近時,射流發(fā)生偏斜。另外,射流發(fā)生振蕩還需要在一定的腔體長度范圍內(nèi)。其次,對矩形自激振蕩射流的混合特性進行了分析。主要對比分析了射流橫截面平均速度、中心線平均速度、脈動速度、湍流度和頻譜等湍流統(tǒng)計量。結(jié)果表明：相比于自由射流,自激振蕩射流的中心線速度衰減更快、擴散角更大、湍流度更高,矩形自激振蕩射流的低頻能量更多,表明矩形自激振蕩射流大尺度混合性能增強。然而通過對比矩形自由射流與自激振蕩射流能譜高頻區(qū)域發(fā)現(xiàn),自激振蕩射流小尺度脈動能量更低,表明自激振蕩射流小尺度能量被傳遞到尺度,小尺度混合被抑制。
[Abstract]:Optimizing the nozzle structure and improving the mixing performance not only have profound scientific significance, but also for industrial burners, mixers, The research and development of reactor and other equipment have important guiding value. The whole low frequency oscillation will occur when the fluid is injected into the sudden expansion chamber with a specific structure, which is called self-excited oscillating jet. The results of many industrial applications in Europe and America show that compared with the traditional multi-jet burner, Self-excited oscillating jet burner can reduce NOx emission by 30-50 and fuel consumption by 5- 10. In order to further optimize the performance of self-excited oscillating jet burner, the rectangular self-excited oscillating jet is experimentally studied in this paper. The flow characteristics of rectangular self-excited oscillating jet were studied. The jet diffusion angles were measured under the conditions of different cavity length and different ratio of length to width of rectangular orifice by ribbon exposure test, hot wire experiment and smoke line experiment. Velocity field and flow field structure. It is found that the larger the aspect ratio, the stronger the two-dimensional characteristics of the rectangular jet, and the easier it is to produce self-excited oscillation, but when the rectangular short edge is close enough to the wall of the cavity, the jet deflects. The mixing characteristics of rectangular self-excited oscillating jet are analyzed. The average velocity of cross section, mean velocity of center line, pulsation velocity are compared and analyzed. The results show that compared with the free jet, the central linear velocity of the self-excited oscillating jet attenuates more rapidly, the diffusion angle is larger, the turbulence degree is higher, and the low frequency energy of the rectangular self-excited oscillating jet is higher than that of the free jet. The results show that the large scale mixing energy of the rectangular self-excited oscillating jet is enhanced. However, by comparing the high frequency region of the energy spectrum of the rectangular free jet with the self-excited oscillating jet, it is found that the small scale pulsating energy of the self-excited oscillating jet is lower. It is shown that the small scale energy of the self excited oscillating jet is transferred to the scale and the small scale mixing is suppressed.
【學(xué)位授予單位】：大連海事大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U664

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本文編號：1631069