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研究生:李浩然
研究生(外文):Lee, Haw Ran
論文名稱:無負載急加速測試中柴油車黑煙濃度之量測與分析
論文名稱(外文):The Measurement and Analysis of Diesel Engine Smoke in the Rapid Acceleration Test
指導教授:盧昭暉盧昭暉引用關係
指導教授(外文):Jau-Huai Lu
學位類別:碩士
校院名稱:國立中興大學
系所名稱:機械工程學系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:1998
畢業學年度:86
語文別:中文
論文頁數:105
中文關鍵詞:無負載急加速黑煙
外文關鍵詞:Rapid Acceleration TestSmoke
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柴油引擎由於熱效率高、省油、使得柴油車的應用範圍日漸增加,尤其是
行走里程較長的公共汽車及貨卡車都是使用柴油引擎。而黑煙是柴油引擎
所排放汙染中最明顯的一部份,由於可用肉眼明顯的分辨出來,為一般民
眾所厭惡,而降低柴油引擎的黑煙排放也成為民眾一致的訴求。目前我國
柴油車的排煙檢測方法分成無負載急加速檢測及全負載定轉速檢測兩部份
,以污染度為單位。依交通工具空氣污染物排放標準規定,柴油車在目前
所實行的二期標準中,新車型審驗與新車抽驗的黑煙標準為不得超過40%
污染度。在無負載急加速檢測中,依照CNS 11644之規定,煙度計之取樣
時間為1~2秒,但此1~2秒之容許偏差可能引致測試結果不同,本文首先探
討檢驗人員的操作方式對測試結果的影響,其中有兩項操作參數,一是開
始取樣時間,一是踩油門速度。本研究分別量測引擎在急加速過程中引擎
轉速,油門位移,排氣管壓力,及排氣不透光率的變化,並記錄污染度。
此外,本文並以熱線測速儀來量測煙度計在取樣過程中的動作時間與瞬時
吸取流量。由量測結果可知排氣不透光率的變化是先有一段遲滯期,
約0.3 秒,然後上升到最高點,又開始下降,整個變化共約1.0sec。量測
結果發現踩油門速度越快則污染度越高,且其間的關係並非線性,而是呈
"S" 的變化。而不同檢驗人員的踩油門方式對所量測的污染度也會有影響
,但在一般常踩的速度範圍內影響不大。 黑煙主要是在引擎燃燒過程
中所產生,再由排氣管排出。在排氣管內來自各氣缸的黑煙會互相混合與
擴散,而這混合與擴散的效應又與排氣管的體積,長度,及岐管的幾何形
狀有關。本文接著建立柴油引擎排氣管內的黑煙傳播模式,以探討排氣系
統設計參數對柴油引擎黑煙量測的影響。本文將排氣管內的流速分成等速
與加速兩種情況,分別對應引擎定轉速與急加速兩種測試方法。當排氣管
內的流速為等速時,排氣管對黑煙傳播的主要效果是延遲作用,對黑煙濃
度沒有影響,最重要的參數是總體積;而消音器對黑煙傳播的主要效果是
降低黑煙瞬間的最高濃度,並拉長變化的時間,最重要的參數也是總體積
。當排氣管內的流速為加速時,排氣直管對黑煙傳播的效果主要是延遲作
用及壓縮作用,對黑煙濃度則沒有影響。消音器對黑煙傳播的效果與在引
擎等速的情況下類似,但由於同時具有黑煙與質量的混合作用,故效果更
顯著。最後本研究共設計了八隻不同體積的消音器以及不同長度的排氣管
來探討不同總體積及長度的變化對黑煙量測的影響。量測結果顯示實驗值
與理論值的變化趨勢幾乎完全相同,只是實驗值的變化量比理論值大。
Smoke is the most obvious part of the exhaust emitted from
Diesel engines. The methods for smoke testing currently used in
Taiwan are the rapid acceleration test under no load and the
constant speed test under full load. The smoke concentration is
measured with the light reflection method. According to the
test procedure, the smoke meter sampling time in the rapid
acceleration test is 1~2 seconds. The current range in sampling
time may cause discrepancies in test results. In these tests,
free acceleration of engine is achieved by actuating the pedal
rapidly. However, the speed of engine acceleration has not been
defined clearly in the test procedure. The objective of this
research is to study the effect of the operating conditions upon
the results of smoke tests. There are two operating factor
during smoke test , one is sampling time , the other is pedal
speed. Experiments were carried out in this study. The results
of measurements showed that the opacity of the engine exhaust
increased rapidly after a delay of about 0.3 seconds and then
fell. The entire period of smoke variation was about 1 second.
Because the extraction rate of the smoke meter was not uniform,
the smoke particles contained in the sampled exhaust may have
been affected by changes in the sampling time. As for the effect
of pedal actuation speed, results showed that the faster the
pedal speed, the higher the smoke level. However, the
relationship between the smoke level and the pedal speed is
nonlinear. The graphic representation is "S" shaped. A smoke
transport model was developed in this research to study the
effect of exhaust system configuration on smoke measurements.
It was found that under a constant engine speed condition, a
straight pipe has a delay effect and the muffler has a mixing
effect on smoke transport. In the case of engine acceleration,
smoke transported along a straight pipe is compressed, but the
peak concentration remains the same. The effects of a muffler on
smoke measurements are similar to those under a constant speed
condition. At last, we design eight exhaust pipes in response
to the condition of engine acceleration. During these results,
we prove that the experimental value is similar to theoretic
value, but the variation of experimental value is more than
theoretic value.
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