Simulation and Experimental Measurement of Flow Field within Four-Stroke Motorcycle Engines

四行程引擎氣缸內流場數值模擬與量測

朱力民(Li-Ming Chu) ； 張敏興(Min-Hsing Chang) ； 徐祥禎(Hsiang-Chen Hsu) ； 簡文通(Wen-Tung Chien) ； 劉建亨(Chien-Heng Liu)

《中國機械工程學刊》 29卷2期 (2008/04) Pp. 149-158

https://doi.org/10.29979/JCSME.200804.0007

摘要

四行程引擎氣缸內的流場現象影響到整個引擎的性能與廢氣排放，因此本文針對四行程引擎氣缸內流場與壓力場做模擬與分析。本文在初步設計時使用電腦輔助設計(CAD)軟體設計出四行程引擎氣缸，再運用電腦繪圖軟體來建構氣缸內部網格型態，配合計算流體力學(CFD)分析軟體計算出氣缸內部流場的變化，再運用流量測試檯來比較理論值與實驗值的差異，以確認本文分析之合適性與準確性。經由結果比較顯示，模擬值皆大於實驗值。在雙閥門引擎部分，模擬值與實驗值的最大誤差為7.56%；在進氣門開啟昇程相等之四閥門引擎部分，模擬值與實驗值的最大誤差為8.54%；在進氣門開啟昇程不相等之四閥門引擎部分，模擬值與實驗值的最大誤差為9.71%。因此本文所建立的計算流體力學分析模式可預估流量隨壓差變化的關係，這些分析的結果可提供給工程師作為設計引擎的效率與性能時的參考。

並列摘要

The flow characteristics inside four-stroke motorcycle engines are investigated in the present study due to their significant influences on the engine performance and exhaust gas. The four-stroke engine was designed using CAD software and its internal grid pattern was constructed by the software GAMBIT. Next, the flow field inside the engine was analyzed by the CFD software (i.e. Fluent) and a flow bench was used to measure the practical performance of the engine. Both simulated and experimental results are compared together to evaluate the practicability and accuracy of the theoretical model. The results show that the simulated data always exceeds those of experimental measurements. For a two-valve engine, the maximum difference between simulation and experiment is 7.56% based on the experimental results. As for a four-valve engine with equivalent lift strokes of intake valves, the maximum difference is 8.54%, while for the case of unequal lift strokes, the maximum difference is 9.71%. Accordingly, the established model in this work could provide a valuable tool to predict the relationship between the flow rate and pressure difference and thus the performance of four-stroke motorcycle engine.

並列關鍵字

Four-stroke motorcycle engine ； Flow field analysis