An Experimental Investigation of a Mini-Scale Porous Mmedia Combustor for Hydrogen Combustion

小型多孔介質燃燒器之氫氧燃燒實驗探討

蘇脩聖(Siou-Sheng Su) ； 賴維祥(Wai-Hsiang Lai) ； 黃聖杰(Sheng-Jye Hwang)

《中國機械工程學刊》 38卷4期 (2017/08) Pp. 373-380

摘要

This study discusses low thermal load and NO emissions in a mini-scale porous media combustor, as well as stable combustion were examined via quartz tube observation. The materials of porous media were OB-SiC, Al_2O_3 and ZrO_2, and three types of porous media arrangement were examined in this experiments. The results showed that stable combustion of hydrogen fuel was obtained under different equivalence ratios and thermal loads. The hydrogen conversion rate and NO concentration in the exhaust gas depended on the flame position and thermal loads. When surface combustion occurred, the hydrogen flame was located on the surface of downstream porous medium, and the reaction temperature and residence time were lower under a low equivalence ratio and thermal load, and the conversion rate of hydrogen and NO concentration were also lower. When interior combustion and a conical flame occurred, hydrogen flame was located on the interface of two porous media and a divergent section of the combustor. The reaction temperature and residence time were both higher with interior combustions than with surface combustion. With a higher equivalence ratio and thermal load, the conversion rate of hydrogen also rose due to the longer reaction time. High temperature conditions prompted the thermal mechanism of NO formation. The NO concentration of the exhaust gas was kept low due to the low temperature and residence time under lower thermal loads and equivalence ratios. In contrast, the NO concentration of the exhaust gas increased under a higher thermal load and equivalence ratio. Overall, the results show that stable combustion performance and low NO emissions can be achieved by using hydrogen fuel and a porous medium arrangement in a mini-scale combustor.

關鍵字

Mini-scale combustor ； Low NO emission ； Hydrogen ； Porous media

並列摘要

本研究為探討小型多孔介質燃燒器之氫氣燃燒實驗探討。透過軸向溫度分佈量測與一石英管燃燒室，進行觀察氫氣火焰穩駐位置。氫氣流率分別為1.0、2.0、3.0、4.0與5.0 L/min，當量比為0.2-0.5。多孔介質材料為碳化矽(OB-SiC)、三氧化二鋁(Al_2O_3)與二氧化鋯(ZrO_2)。透過實驗得知，在較高的當量比與輸入熱能時(Thermal load)，氫氣火焰為錐型火焰。火焰位於燃燒室較上游處，具有較長的反應距離，因此氫氣轉換率較高。並且燃燒產物中NO的濃度亦較高。在較低當量比與氫氣流率下，氫氣火焰為表面與內部燃燒。火焰位於燃燒室的中間與下游處，其滯留時間較短。燃燒產物未能有充足的反應時間，因此氫氣轉換率與NO的濃度較低。此外，在Type I的配置下(上、下游:碳化矽)，因碳化矽的熱傳導係數高，熱能較容易消散。NO的主要產生機制(Thermal mechanism)較不易發生，整體而言NO濃度較其他兩者配置低。