單缸二行程機車引擎性能模擬與排氣噪音計算

Calculations of the Engine Performance and the Exhaust Noise for Single Cylinder Two Stroke Mopad Engines

許友維(Yoeu-Wei Sheu) ； 盧昭暉(Jau-Huai Lu) ； 鐘證達(Cheng-Ta Chung) ； 魏瑞昌(Ruey-Chang Wei) ； 蔡國隆(Kuo-Long Tsai)

《中華民國振動與噪音工程學會論文集》 1996 (1996/04) Pp. 141-153

https://doi.org/10.30028/CSSVANNUAL.199604.0141

摘要

本文主要是進行單缸二行程機車引擎在穩定運轉時的排氣噪音計算。這是考慮引擎點火運轉時，排氣管內因氣體流動與壓力波動所產生的噪音。在本文中以WAVE軟體來模擬在整個引擎循環中，氣缸與進排氣管內的壓力與流量變化，並以此來計算排氣管出口二公尺外的總噪音量及噪音頻譜分佈。由於真實排氣管是由數個膨脹室及連通管所組成，其中並包含觸媒轉化器，構造相當複雜，本文中以兩種不同方法來建立排氣管模型。第一種模型將排氣管切割成幾個主要的氣室與連通管，而在第二種模型則再將氣室細分成數個小氣室。本文中進行不同轉速下引擎性能與排氣噪音的比較，在引擎性能方面，第二種模型的計算結果與量測較接近；在排氣管內的壓力變化方面，兩種模型的計算結果很接近；而在排氣噪音頻譜方面，在600 Hz以下，兩種模型都能預測基頻噪音及其整倍數的噪音，而在600 Hz以上，則第二種模型所預測的噪音值較高。

並列摘要

The exhaust noise and engine performance of single cylinder two stroke engines were calculated in this paper with the WAVE code. Two models of the exhaust pipe were established. In the first model, the muffler was considered as combinations of junctions and pipes. In the second model, the expansion chamber of the muffler was further divided into small junctions. Comparisons of the calculated engine performance with the measured data showed that the second model is better. As for the exhaust noise, both models predicted noise at the fundamental frequency and some of its high order harmonics. However, the prediction of high frequency components for the second model is higher than that of the first model.