臺灣博碩士論文加值系統

隨著風機效能地持續提升導致其衍生噪音也不斷增加，而風機所產生的特徵頻率噪音十分尖銳，係由葉輪旋轉衝擊氣體所造成，因此降低風機特徵頻率噪音即成為本研究重點；在此結合透過數值模擬以及實驗驗證方式，系統地評估三種常用風機之性能及噪音，並透過加裝亥姆霍茲共振器來降低風機所產生之特徵頻率噪音。本論文首先依據各式風機原型之幾何參數建模，並利用CFD 模擬軟體進行數值分析，透過穩態流場之可視化及暫態聲場模擬分析，探討流場與噪音之關連以找出風機噪音源，再藉由加裝亥姆霍茲共振器以期對風機所產生特徵頻噪音有所改善，最後整合比較各式風機有/無加裝共振器之效果；實驗部分則透過 CNC 加工技術製作共振器，以及利用3D 列印進行複雜的風機葉輪與外殼製作，接著搭配各式基準風扇進行相關之性能實驗，透過量測結果驗證數值模擬準確度。
模擬結果彙整顯示，於軸流風機上，針對第一特徵頻設計的共振器降低目標特徵頻噪音11~19 dB，而目標第二特徵頻率的共振器則降低第二特徵頻噪音20~23 dB；而在斜流風機模擬結果，針對第一特徵頻設計的共振器約降低此特徵頻噪音2~7 dB，而目標為第二特徵頻的共振器能降低此特徵頻噪音4~9 dB；至於在離心風機上，以第一特徵頻設計之兩種共振器則分別可降低此特徵頻噪音3.3 dB及4.6 dB。至於實驗測試部分，軸流風機設計之共振器，所呈現之減噪效果最好，於第二特徵頻率可降噪20 dB，而整體噪音也降1.0 dB；實驗結果與模擬趨勢相符，但減噪量仍有所誤差，至於共振器應用於斜流風機上，針對兩種頻率的共振器設計之測試發現，最佳效果令兩個頻率下降5.4與6.9 dB；而於離心風機針對第一特徵頻所設計的兩共振器，能有效降低此特徵頻1.5~1.9 dB。綜整本研究所建立之數值模擬與實驗驗證方式，已建立一套共振器應用於風機噪音改良與評估之系統，能提供完整且可靠的設計系統以有效地降低風機的特徵頻噪音問題。

This study intends to apply Helmholtz resonator on the axial-flow, the mix-flow, and the centrifugal fans for improving their narrow-band noises by an integrated effort of numerical simulation, mockup fabrication, and experimental test. At first, the cascade and design theories are utilized to generate the three-dimensional configuration of each fan type for serving as the reference basis. Next, the flow fields and the acoustic features associated with these fans are simulated and evaluated systematically with the aids of the commercial CFD software Fluent. Subsequently, the thorough understanding on the flow and acoustic features of these fans can be attained and utilized to design proper Helmholtz resonators, which are manufactured via CNC technology and installed on the appropriate location for assessing the associated noise-reduction outcomes via both CFD and experimental techniques. For the axial-flow fan, CFD simulation indicates that the noise reductions caused by resonators designed for the 1st and 2nd harmonic frequencies are 11-19 dB and 20-23 dB on their target frequencies, respectively. Also, the experiments present that resonator designed for the first characteristic frequency has the best noise-reduction effects, which are 20.0 and 1.0 dB on the 2nd harmonics and the overall noise, respectively.
Regarding the mix-flow fan, numerical calculation predicts that the noise reductions caused by Helmholtz resonators designed for the 1st and the 2nd harmonic frequencies are 2-7 dB and 4-9 dB on their target frequencies, respectively. Also, the experiments illustrate the best noise-reduction effects on the 1st and the 2nd harmonics are 5.4 and 6.9 dB, which are not deviated too much from CFD result. However, the application of resonator on the centrifugal fan is not as effective as the above two fan types. CFD outcomes show that the noise decreases of 3.3 dB and 4.6 dB are achieved on the 1st characteristic frequency by the installation of two resonator designs aimed at the first harmonics. In addition. the smaller noise -reduction effects are found as 1.5 dB and 1.9 dB via the acoustic test inside a semi-anechoic chamber. Generally, the trend and deviation between CFD and test results are correlated and within an acceptable range. In conclusion, the accomplishment of this study provides a systematic design scheme for the application of Helmholtz resonator on three common-used fan types. Several design parameters and installation locations of Helmholtz resonator are analyzed and discussed in a rigorous manner here.

摘 要 I
Abstract III
致 謝 V
目錄 VI
圖索引 X
表索引 XIV
符號索引 XVI
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 3
1.2.1 風機噪音研究 4
1.2.2 數值模擬 5
1.2.3 共振器之發展 8
1.3 研究動機與流程 13
1.4 本文大綱 17
第二章 風機氣動噪音及共振器介紹 19
2.1 氣動噪音理論 21
2.1.1 氣動噪音 21
2.1.2 風機窄頻帶噪音 25
2.2 共振器之介紹及設計 27
第三章 數值方法 37
3.1 統御方程式 37
3.2 紊流模組 39
3.2.1 雷諾數平均數值模擬法 40
3.2.2 大尺度渦漩模擬法 41
3.2.3 聲學模式 43
3.3 數值計算方法 46
3.3.1 數值模擬分析之求解流程 47
3.3.2 離散化方程式 51
3.3.3 速度與壓力耦合 54
3.4 邊界條件 55
第四章 實驗設備與規劃 58
4.1 風機噪音之實驗設備 58
4.2 風機之性能量測設備 66
4.3 實驗規劃 70
第五章 亥姆霍茲共振器於軸流風機之應用分析 73
5.1 基準軸流風機之數值模型 73
5.2基準軸流風機之模擬結果 78
5.2.1 穩態模擬之流場分析 78
5.2.2 暫態模擬之流場分析 86
5.3軸流風機共振器的設計與配置 88
5.4裝配共振器之軸流風機的噪音模擬分析 92
5.5 軸流式風機裝配共振器之實驗測試結果 102
第六章 亥姆霍茲共振器於斜流風機之應用分析 113
6.1 基準斜流風機之數值模型 113
6.2 基準斜流式風機之模擬結果 119
6.2.1 穩態模擬之流場分析 119
6.2.2 暫態模擬之流場分析 122
6.3 斜流風機共振器的設計與配置 124
6.4 裝配共振器之斜流風機的噪音模擬分析 128
6.5 斜流風機裝配共振器之實驗測試結果 135
第七章 亥姆霍茲共振器於離心風機之應用分析 145
7.1 基準離心式風機之數值模型 145
7.2 基準離心式風機之模擬結果 152
7.2.1 穩態模擬之流場分析 152
7.2.2 暫態模擬之流場分析 155
7.3 離心風機共振器的設計與配置 158
7.4 裝配共振器之離心風機的噪音模擬分析 162
7.5 離心風機裝配共振器之實驗測試結果 169
第八章 結論與建議 177
8.1結論 177
8.1.1 軸流式風機 178
8.1.2 斜流式風機 179
8.1.3 離心式風機 180
8.2建議 181
參考文獻 183

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