Abstract
本文的目的在以數值方法來分析燃氣在平板紊流邊界層之引燃問題，所採用的物理模式包括預混火焰與擴散火焰兩種型式，在預混火焰引燃方面，以預混燃氣流經一高溫熱板，並包括此平板之初始端有否存在一段未加熱區的情況。在擴散火焰引燃方面，則是一高溫之燃料噴流經由一多孔性平板注入空氣流中。有關燃氣流速、壁溫、未加熱區長度及燃料噴流速度對引燃長度的影響，皆在探討的範圍之內。結果顯示在預混火焰引燃方面，引燃長度隨著燃氣流速之增加與壁溫之降低而明顯增長。若平板之初始端存在一段未加熱區時，此未加熱區長度對引燃之影響可忽略不計，而引燃長度幾乎與未加熱區長度呈線性增加的關係。在擴散火焰引燃方面，引燃長度則隨著燃料氣體在壁上之噴流流速的增加而急劇減短。In this report, we investigate numerically the ignition problemin the turbulent boundary layer, including two kinds ofignition structures : premixed flame and diffusion flame. Forthe first kind, a premixed combustible gas flows over anisothermal hot plate with and without unheated starting length.For the second kind, a hot fuel injection is issued into theair stream through a porous plate. The effects of free streamvelocity, plate temperature, unheated starting length andinjection velocity on the ignition are studied. The resultsreveal that, for ignition of a premixed combustible gas, theignition length increases as the free stream velocity increasesand the plate temperature decreases. For the case of anunheated starting length, the effect of the unheated length onthe ignition is negligible, such that the ignition lengthincreases nearly linearly with the unheated length. Forignition of diffusion flame, an increase of the injectionvelocity will shorten the ignition length evidently.