臺灣博碩士論文加值系統

提動閥是四行程引擎進氣系統中最主要的氣流限制構件,它攸關每一循環進入汽缸內的空氣質量以及引擎的容積效率.國內外雖有許多針對空氣流經提動閥所做的研究,然而大部份的研究僅限於靜態或低速運轉狀態下的實驗,與實際運轉的引擎有很大差別.本文探討實際引擎運轉下,流經提動閥之瞬時空氣質量流率之變動情形及引擎動態與動態流逸係數之特性,以便能掌握引擎進氣系統設計的關鍵技術.研究結果顯示:所有的引擎轉速下,閥門開啟過程的流逸係數大都穩定的維持在0.3與0.4間,然而在閥門關閉過程的流逸係數卻有隨之增加而有逐漸提升的趨勢.最後,比較所得到的動態與動態流逸係數,即使在進氣埠壓力與汽缸內壓力相同及閥門揚程相同條件下,靜態的流逸係數明顯大於動態流逸係數.

The Poppet Valve is the most important flow restriction in the intake system of four-stroke cycle engines, hence the air flow characteristics throughit is crucial in determining the breathing capacity of an engine.A lot of workconcerning the air flow through Poppet Valves has been done,but most of them are based on ''static'' tests or ''speed''tests.The objective of the present studyis to evaluate the instant air mass flow rate and the discharge coefficients through poppet inlet valve of a real operating engine. The results show that the dynamic discharge coefficient during the valve opening period is larger than that of closing period when engine speed is low,and the dynamic discharge coefficient during the valve opening period is less than that of closing period when engine speed is high.Under the same operatingcondition the dynamic coefficient is lower than the static discharge coefficent.