臺灣博碩士論文加值系統

近幾年來消音器的運用範圍愈來愈廣泛，而為了要達到良好的消音效能，通常都是將消音器的膨脹室變大或者是由多個膨脹室組合而成。因此，消音器在機器工具上就必需要有足夠的空間去裝載。所以本文以短的偏心單膨脹室切入，藉由出入口管的偏心角度、有無延伸管及不同斷面幾何作為參數，利用電腦數值模擬分析得到各參數下的傳輸損失。從傳輸損失所發生的現象，希望在低頻內能有良好的消音效能，而達到體積小及消音效能高的目的。研究中發現當膨脹室內部聲壓為零的節線落在出口端處的時候，傳輸損失會提高且有峰值的產生;當入口管及出口管距離很接近且呈相對的時候，大約在825Hz膨脹室會產生共振效應，以至於傳輸損失很高且有峰值產生;在偏心角180度下不同斷面的偏心單膨脹室，其第一聲場模態發生愈早第一峰值產生也就愈早。

The applications of mufflers have been more and more extensive in recent years. In order to improve the efficiency of noise reduction, the mufflers either need to be enlarged or connected in series. Hence, the vehicle needs a large space to encompass the muffler. The purpose of this study is to investigate the transmission loss of short expansion mufflers with offset extended tubes by using the boundary element method. The eccentric angle, the extended tube and the different cross areas are used as design parameters in the study. By using computer simulations, the transmission loss of each parameter and the phenomenon can be investigated. Results show that when the nodal line of the acoustic pressure revolves inside the chamber and reaches the outlet tube, it will lead to a higher transmission loss .On the other hand, when the inlet tube is in close proximity with the outlet tube, the chamber acts as a resonator with peak frequency can occur as low as 825 Hertz. Results also show the larger angle of the outlet tube revolves, the lower the peak frequency occurs.

第一章 緒論.............................................1
1.1 研究動機............................................1
1.2 研究方法............................................2
第二章 聲壓在偏心消音器的分佈與變化.....................4
2.1 電腦模擬聲場模態...................................5
2.2 聲壓在偏心單膨脹室消音器的變化.....................5
第三章 偏心單膨脹室消音器在不同參數下的分析.............7
3.1 偏心消音器分析步驟.................................9
3.2 偏心單膨脹室消音器(0°) 之傳輸損失分析與結果.......10
3.3 偏心單膨脹室消音器(45°) 之傳輸損失分析與結果......13
3.4 偏心單膨脹室消音器(90°) 之傳輸損失分析與結果......16
3.5 偏心單膨脹室消音器(135°)之傳輸損失分析與結果......18
3.6 偏心單膨脹室消音器(180°)之傳輸損失分析與結果......21
第四章 不同斷面下偏心單膨脹室消音器的分析..............27
4.1 斷面為正方形、長方形及橢圓的聲場模態...............29
4.2 不同斷面偏心角為0°之傳輸損失分析與結果.............30
4.3 不同斷面偏心角為180°之傳輸損失分析與結果...........32
第五章 結論與未來研究方向..............................38
5.1 結論...........................................38
5.2 未來研究方向...................................39
參考文獻 40
附錄A INAP與SYSNOISE對消音器傳輸損失的傳輸損失的分析比 對.....................................................42
附錄B 圓管聲場模態....................................44
附錄C 方管聲場模態....................................46
附錄D 不同斷面在偏心角180度含左右延伸管825Hz場點聲壓比較圖.....................................................53
致謝 ................................................55

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