二行程引擎掃氣效率之數值模擬分析

Numerical Simulation of Scavenging Efficiency of Two-Stroke Engines

何順暉(Shun-Hui Ho)

指導教授 ： 戴昌賢 ； 蔡建雄

國立屏東科技大學/工學院/車輛工程系所/碩士(2008年)

https://doi.org/10.6346/NPUST.2008.00259

摘要

論文摘要內容：
本文以計算流體力學(CFD)方法探討三維二行程引擎之掃氣效率。二行程引擎的性能關鍵是在於掃氣過程的優劣，掃氣的優劣指標為掃氣效率下與捕氣效率。在掃氣過程中活塞的形狀，掃氣口的位置、方向及角度，掃氣口流道角度，將影響引擎的掃氣效率。文中探討CO2由掃氣口進入汽缸內所行經的路徑(短路、廻環掃氣、中心損失、壁面迴路)對掃氣效率及捕氣效率的影響。本研究針對活塞頂面的幾何形狀，掃氣口及掃氣口流道的角度進行分析，結果顯示改變掃氣口流道角度(50°)能提升4%的掃氣效率及捕氣效率。針對改變掃氣口流道(50°)做分析，將排氣行程角度減少9°，能使掃氣效率及捕氣效率均提升13%。經研究結果發現原始引擎性能的關鍵在於排氣角度設計過大。

關鍵字

掃氣效率 ； 捕氣效率 ； 掃氣口

並列摘要

The Contents of Abstract in this Thesis:
In this paper, Computational Fluid Dynamics (CFD) method was used to study the scavenging efficiency by a 3D two-stroke engine. The scavenge process of a two-stroke engine is one of main factor to evaluate the engine performance. The geometry of piston surface, and the angle of transfer port and channel will affect the scavenging efficiency. CO2 flows in to the cylinder from channel are decided by the following four flow paths short-circuiting, loop scavenging, central loss and near-wall flow for scavenging efficiency (SE) and trapping efficiency (TE). In the study, three kinds of geometrics of piston surface, and three different degrees of transfer port and channels. In the results, the 50° channel of transfer port can enhance 4% SE and TE. And to reduced 9° of exhaust process in this case, the SE and TE will enhance 13%. Actually, the exhaust process of the origin engine in too long.

並列關鍵字

scavenging efficiency ； trapping efficiency ； transfer port

參考文獻

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