本文選題：噴流噪聲　切入點(diǎn)：分開(kāi)排氣　出處：《南京航空航天大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：噴流噪聲是發(fā)動(dòng)機(jī)噪聲的主要噪聲源之一。為了適應(yīng)日益嚴(yán)格的飛機(jī)適航噪聲標(biāo)準(zhǔn),降低發(fā)動(dòng)機(jī)噴流噪聲是民用渦扇發(fā)動(dòng)機(jī)設(shè)計(jì)時(shí)必須考慮的主要因素之一。針對(duì)這個(gè)背景,本文采用大渦模擬(LES)以及聲學(xué)軟件ACTRAN中的氣動(dòng)聲學(xué)模塊對(duì)噴流噪聲的斜切噴管降噪進(jìn)行了數(shù)值研究。分別選用分開(kāi)排氣系統(tǒng)和混合排氣系統(tǒng)物理模型,研究分析了邊界條件、斜切角度和斜切位置對(duì)排氣噴流氣動(dòng)和聲學(xué)特性的影響,同時(shí)對(duì)比分析了遠(yuǎn)場(chǎng)和近場(chǎng)噪聲特征。研究結(jié)果表明:1、在分開(kāi)排氣系統(tǒng)中,邊界條件和斜切角度共同影響降噪效果,斜切位置影響聲場(chǎng)分布。噴管斜切后增加噴流與大氣的摻混作用,使湍流核心區(qū)長(zhǎng)度有所縮短,有效的使湍流混合噪聲由低頻段向高頻段轉(zhuǎn)移,內(nèi)涵噴管斜切后總聲壓級(jí)分布降低幅度約2-5d B。外涵噴管斜切后,噴流偏轉(zhuǎn)明顯,使得總聲壓級(jí)分布在上方局部出現(xiàn)升高現(xiàn)象,其余范圍降噪幅值1-6dB�？傮w相較內(nèi)涵斜切比外涵斜切降噪效果好,且斜切角度越大,降噪效果越明顯。2、在混合排氣系統(tǒng)中,當(dāng)噴管斜切時(shí),流場(chǎng)中噴流明顯發(fā)生了偏轉(zhuǎn),且斜切角度越大明顯,湍流核心區(qū)長(zhǎng)度也有所減小�？偮晧杭�(jí)分布也呈現(xiàn)了明顯的不對(duì)稱性,整體噪聲較常規(guī)噴管減小幅值在2-6dB,且下方區(qū)域?qū)Ρ认鄳?yīng)角度的上方總聲壓級(jí)有所減小,達(dá)到了減少噪聲對(duì)地面的輻射作用。隨著斜切角度的增大,降噪效果越明顯。3、通過(guò)遠(yuǎn)場(chǎng)和近場(chǎng)噪聲比較發(fā)現(xiàn),當(dāng)監(jiān)測(cè)點(diǎn)距離增加時(shí)聲波發(fā)生衰減導(dǎo)致噪聲明顯減小,同時(shí)遠(yuǎn)場(chǎng)噪聲更能體現(xiàn)出聲場(chǎng)的指向性。
[Abstract]:Jet noise is one of the main noise source of engine noise. In order to meet the increasingly stringent standards for aircraft airworthiness noise, reduce engine jet noise is one of the main factors to be considered civil turbofan engine design. According to this background, this paper uses large eddy simulation (LES) and acoustic software ACTRAN in Aeroacoustics module of jet noise the scarfed nozzle was numerically studied. Noise reduction were used to separate mixed physical exhaust system and exhaust system model, analyzed the influence of boundary conditions, and oblique position on miscut angle exhaust jet aerodynamic and acoustic characteristics, and comparative analysis of the far field and near field noise characteristics. The results show that: 1, in separate exhaust system in the boundary conditions and the influence of the noise reduction effect of common bevel angle, oblique position affect the sound field distribution. The nozzle and air jet oblique increased after mixing The length, the core area will be shortened, effectively make the turbulent mixing noise transfer from low to high frequency, the connotation of the total sound pressure distribution after oblique nozzle decreased about 2-5d B. by-pass nozzle oblique, jet deflection, the total sound pressure distribution is increased above the local phenomenon, the range of noise amplitude 1-6dB. compared with the overall connotation than the external oblique oblique culvert and good noise reduction effect, oblique angle increases, the noise reduction effect is more obvious in.2, mixed exhaust system, when the nozzle flow field in the jet was oblique, deflected, and oblique angle is more obvious, the length of turbulent core area decreased. The total sound pressure distribution presents the obvious asymmetry, the overall noise amplitude decreased in 2-6dB compared with the conventional nozzle, and the contrast area below the corresponding angle above the total sound pressure level decreases, so as to reduce the noise of the radiation. With the increase of oblique angle, the more obvious effect of noise reduction by.3, the far field and near field noise is found when the monitoring distance increased acoustic attenuation in noise is obviously reduced, reflecting the directivity is also far field noise.

【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：V235.13;TB535
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本文編號(hào)：1633326