本研究使用凹槽作為超音速燃燒衝壓引擎燃燒室之駐焰器，探討不同噴注配置之液態燃料霧化混合特性，以及超音速流場之點火特性與駐焰條件分析。燃料的霧化混合特性與凹槽駐焰器之交互作用現象觀察(非反應流場)主要透過反射式震波風洞進行; 燃燒流場(反應流場)因需要較長之觀測時間，主要藉由連續式風洞進行。實驗方法使用視流紋影法搭配高速攝影機進行不同燃料噴注位置與動量通量比之觀察。震波風洞實驗之結果顯示，調整槽內噴注之角度對凹槽內局部之迴流區與燃料空氣比有很大的影響。另外在上游噴注實驗中，液柱背風處以及靠近壁面的位置會形成渦流對，使得遠離凹槽前壁面的噴注位置具有較好的燃料混合與較短的消散長度(dissipation length)。根據上游噴注與槽內噴注之觀察，遠離凹槽前壁面的噴注與斜角度噴注的組合可能為凹槽駐焰器噴注配置之較佳構型。在連管風洞實驗中，成功使用一種新型的液旋式點火器(liquid-cyclonic igniter)於超音速流場中進行燃油點火。因槽內斜角度噴注比起水平噴注具有更好的燃油霧化混合與較大範圍的可燃性極限，僅在斜角度噴射時觀察到火焰穩定駐焰成功之現象。根據穩定駐焰現象觀察可分為連續駐焰(continuous flame stabilization)與斷續駐焰(intermittent flame stabilization)。另外，成功實現利用凹槽內燃料噴注作為母火，在低全溫的狀態下引燃凹槽上游噴注，持續駐焰時間長達15秒。

The mixing characteristics of liquid fuel injected into a supersonic crossflow and the ignition and flame stabilization in scramjet combustor have been investigated in the present study. The geometry, with a cavity downstream of the injector, mimics a supersonic combustor with a cavity flameholder. A variety of injection schemes and cavity configurations were investigated by means of high-speed schlieren photography. To demonstrate the mixing characteristics, a reflected shock tunnel was employed to generate Mach 2 air flow and simulate high-enthalpy environment in the combustor. Owing to the long test time, a direct-connect wind tunnel was employed to observe the ignition and flame stabilization in Mach 2 air flow. JP-4 liquid fuel was injected at different jet-to-crossflow momentum flux ratios upstream of and from the front wall of the cavity. Results in shock tunnel experiments showed that in direct injection into the cavity adjusting the injection angle has significant effect on the local fuel-air ratio. Furthermore, upstream injection far from the leading edge of the cavity yielded more effective fuel mixing and shorter dissipation length (Ld) than closer injection, due to the development of a vortex on the lee side of the jet core. These results suggest that a combination of upstream injection far from the leading edge of the cavity and inclined direct injection into the cavity may be beneficial for effective mixing in a supersonic combustor cavity flameholder. Results in direct-connect wind tunnel showed that a novel liquid-cyclonic igniter can achieve success fuel ignition in both parallel and inclined fuel injection. However, flame stabilization is only observed in inclined fuel injection due to a better air/fuel mixing and higher flammability limit. Based on the phenomenon of flame stabilization, it can be divided into continuous flame stabilization and intermittent flame stabilization. In addition, the direct fuel injection is successfully employed as the pilot flame to ignite the upstream fuel injection at a relatively low total temperature, and the flame holding last as long as 15 seconds.

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