本文選題：軸流式通風機 + 內(nèi)部流場　； 參考：《東北石油大學》2017年碩士論文

【摘要】：風機主要是用于輸送氣體的葉輪機械,被廣泛應用于國民經(jīng)濟的各個生產(chǎn)部門,尤其是在礦山、冶金、石油、化工、航天航空、船舶機械、能源以及車輛工程等領(lǐng)域。由于石油化工涉及的氣體往往是有毒、易燃、易爆的介質(zhì),對通風機的要求就更加苛刻,必須在結(jié)構(gòu)、操作條件和安全防范措施方面保障通風機運行安全可靠。因此改善風機內(nèi)部流場分布、提高風機P-Q性能以及降低風機氣動噪聲逐漸受到廣大學者的重視。本文的研究對象為軸流式通風機,采用商用計算流體軟件FLUENT14.5對該軸流式通風機的內(nèi)部流場進行數(shù)值計算,分析不同葉輪轉(zhuǎn)速下風機內(nèi)部流場分布變化規(guī)律,以及風機性能曲線變化規(guī)律;采用相同的數(shù)值計算方法分析存在分流葉片時風機內(nèi)流場分布,并分析不同分流葉片尺寸對軸流式通風機內(nèi)部流場分布影響。軸流式通風機在運行過程中往往伴隨著強烈的噪聲,其主要有兩部分組成:一是由于風機葉輪旋轉(zhuǎn)時葉片產(chǎn)生周期噪聲;二是由于空氣流過葉輪流道時,出現(xiàn)附面層分離和尾跡流現(xiàn)象而產(chǎn)生的空氣渦流擾動噪聲。本文采用Lighthill聲比擬法,并結(jié)合LES和FW-H混合模型,對該軸流式通風機進行三維非定常流動噪聲數(shù)值求解,得出葉輪轉(zhuǎn)速對風機噪聲頻譜分布及總聲壓級值的影響;并分析分流葉片對風機噪聲頻譜分布及總聲壓級值的影響。為今后軸流式通風機結(jié)構(gòu)設(shè)計以及風機降噪處理提供理論依據(jù)。通過數(shù)值計算表明,風機葉輪的壓力面靜壓遠高于吸力面靜壓,壓力面靜壓為正壓,而吸力面靜壓為負壓,這是葉輪做功的標志;氣流經(jīng)軸流式通風機葉輪做功,其速度沿軸向方向逐漸增大,動能也隨之提高;而靜壓沿軸向方向逐漸減小,靜壓能轉(zhuǎn)化為氣體動能。另外,由于葉輪尾部邊界流動受到橫向壓力作用,使氣流產(chǎn)生平行于邊界的偏移,從而在風機葉輪尾部產(chǎn)生二次渦流。當存在分流葉片時,氣體流經(jīng)分流流道,靜壓能轉(zhuǎn)為氣體動能,氣體流速增大而靜壓降低;隨著分流葉片尺寸變窄,與葉輪之間的流道變寬,氣體流速降低而靜壓再次升高;另外,分流葉片可使風機內(nèi)靜壓分布更加均勻,減少壓力脈動,從而有效抑制了氣體與葉輪吸力面的流動分離現(xiàn)象;也可削弱葉輪尾部邊界流動受橫向壓力作用而引起的二次流,大大改善葉輪末端尾流擾動。風機入口處的總聲壓級值較低,其主要是葉輪旋轉(zhuǎn)引起葉片附近氣流擾動的旋轉(zhuǎn)噪聲;而風機出口處總聲壓級值較高,其處于葉輪尾跡流和分離脫渦流動區(qū)域,渦流擾動強烈,在旋轉(zhuǎn)噪聲的基礎(chǔ)上疊加渦流噪聲。另外,分流葉片可降低氣體在風機流道內(nèi)的流阻,使葉輪吸力面低能區(qū)靜壓上升,減少脫渦流的產(chǎn)生并沖刷葉輪末端二次尾流,從而降低渦流噪聲;若分流葉片尺寸過短,葉輪吸力面附近靜壓較無分流葉片時低,增強風機流道內(nèi)的分離損失,葉輪吸力面脫渦嚴重,渦流噪聲增強。
[Abstract]:Fan is mainly used for conveying gas impeller machinery, which is widely used in various production sectors of the national economy, especially in mining, metallurgy, petroleum, chemical, aerospace, marine machinery, energy and vehicle engineering and other fields.Since the gases involved in petrochemical industry are often toxic, flammable and explosive medium, the requirements for ventilators are more stringent. It is necessary to ensure the safe and reliable operation of ventilators in terms of structure, operating conditions and safety precautions.Therefore, to improve the flow field distribution, to improve the performance of the fan P-Q and to reduce the fan aerodynamic noise has been paid more and more attention by many scholars.The research object of this paper is axial flow fan. The internal flow field of axial flow fan is numerically calculated by commercial computational fluid software FLUENT14.5, and the variation law of flow field is analyzed under different impeller speed.With the same numerical calculation method, the distribution of flow field in the fan with shunt blade is analyzed, and the influence of different shunt blade size on the flow field distribution in axial fan is analyzed.The axial flow fan is usually accompanied by strong noise during operation, which mainly consists of two parts: one is that the blade produces periodic noise when the fan impeller rotates, the other is because the air flows through the impeller runner,Eddy current disturbance noise caused by boundary layer separation and wake flow.In this paper, by using Lighthill sound analogy method and LES and FW-H mixed model, the three-dimensional unsteady flow noise of the axial flow fan is numerically solved, and the influence of impeller speed on the noise spectrum distribution and the total sound pressure level of the fan is obtained.The influence of shunt blade on noise spectrum distribution and total sound pressure level of fan is analyzed.It provides the theoretical basis for the structure design of axial flow fan and the noise reduction of fan in the future.The numerical calculation shows that the static pressure of the fan impeller is much higher than that of the suction surface, the static pressure on the pressure surface is positive pressure, and the static pressure on the suction surface is negative pressure, which is the sign of the work done by the impeller.The velocity increases gradually along the axial direction and the kinetic energy increases, while the static pressure decreases along the axial direction, and the static pressure energy is converted into the kinetic energy of the gas.In addition, due to the lateral pressure acting on the tail boundary flow of the impeller, the flow is offset parallel to the boundary, thus the secondary eddy current is produced in the tail of the fan impeller.When there is a shunt blade, the static pressure energy is converted into gas kinetic energy, the gas velocity increases and the static pressure decreases, and with the size of the shunt blade becoming narrower, the passage between the shunt blade and the impeller becomes wider, and the gas velocity decreases and the static pressure increases again.In addition, the shunt blade can make the static pressure distribution in the fan more uniform and reduce the pressure pulsation, thus effectively restrain the flow separation phenomenon between the gas and the suction surface of the impeller.The secondary flow caused by transverse pressure on the tail boundary flow of impeller can also be weakened, and the wake disturbance at the end of impeller can be greatly improved.The total sound pressure level at the inlet of the fan is low, which is mainly the rotating noise caused by the impeller rotation, while the total sound pressure level at the outlet of the fan is higher, which is located in the impeller wake flow and the separation of the eddy current, and the eddy current disturbance is strong.The swirl noise is superimposed on the basis of rotating noise.In addition, the shunt blade can reduce the flow resistance of the gas in the fan channel, increase the static pressure in the low energy area of the suction surface of the impeller, reduce the generation of deswirl and wash the secondary wake at the end of the impeller, thereby reducing the eddy current noise; if the size of the shunt blade is too short,The static pressure near the suction surface of the impeller is lower than that of the blade without shunt, which enhances the separation loss in the fan passage, and the impeller suction surface devortex seriously, and the eddy current noise is enhanced.
【學位授予單位】：東北石油大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH432.1

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