電漿對合成氣體層流火焰速度之影響

Abstract

本研究之目的為了解於標準條件下 (T = 298 K, P = 1 atm) 合成氣體 (H2 : CO = 1:1) 有電漿影響與未加電漿之條件下的層流火焰速度。本研究使用本生燈量測法，量測之當量比範圍介於0.7≤ ϕ ≤ 1.6。經由與文獻之比較，結果大致相同，差異約略為5~18%；本研究亦添加稀釋氣體N2 (20% & 40%)，結果與文獻之差異約介於5~10%。 本文最後探討電漿對火焰速度之影響。本研究採用同心圓介電質放電裝置，電極使用M3與M8牙條，接地則使用不同長度銅片與不同目數之不銹鋼網。經實驗分析，以M3為電極，並使用相同長度接地的銅片所上升之火焰速度較不銹鋼網高2.6~5.7%，O3 濃度亦高於不銹鋼網5.6~26.3%；使用1及2公分銅片之增益無明顯差別，量測之O3 濃度亦相差無幾。以M8為電極，P = 220及250瓦之火焰速度的增益與O3 濃度無顯著差異；使用10網目之增益則略大於2網目，O3 濃度也僅有些微差距。 由火焰速度之增益得知，增益隨著當量比越大而減少。當量比越大，則空氣流量越大，所以空氣停留在放電區的時間也隨之縮短，空氣被解離的程度較不完全，因此產生之O3 濃度也較低。由本研究之能量密度亦可證明，空氣之流量越大，能量密度越小，O3 濃度也較低。 本研究中探討電漿對火焰速度之影響。電漿會解離出許多不同氣體，O3 僅是影響火焰度的原因之一，而本研究目前僅針對O3 的影響進行探討。

The study was to investigate the laminar flame speed of the premixed syngas mixtures (Syngas, H2 : CO = 1:1) at ambient condition (T = 298 K，P = 1atm), in particularly, the effects of plasma discharges on the flame speed. The Bunsen burner approach was chosen as measurement technique, and the equivalence ratio ranged from Φ = 0.7 to Φ = 1.6. In general, when the plasma was not present, our results were in good agreement (with 18%) literature studies. When nitrogen was mixed with the mixture, the flame speed decreased due to the increase in heat capacity, resulting in a decrease in temperature, consistent with the observation by others. The plasma was generated with a co-axial electrode configuration. It was shown that the discharge had an impact on both of the premixed flame structure and the flame speed. With the presence of plasma, the flame was less sooting and the flame speed was seen to increase. The increase in flame speed correlated with the concentration of ozone generated in plasma. The concentration of ozone was influenced by the electrode configuration and the power density. A copper sheet used as an electrode produced more ozone than a mesh, thus leading to the higher flame speed. The larger the power density was, the higher the ozone concentration was and thus the more enhancement on the flame speed.