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Buoyancy effects on hydrogen diffusion flames confined in a small tube
International Journal of Hydrogen Energy ( IF 7.2 ) Pub Date : 2020-05-25 , DOI: 10.1016/j.ijhydene.2020.05.010
Ming Zhao , Aiwu Fan

In this work, buoyancy effects on hydrogen jet flames confined in a small tube without air co-flow were numerically investigated. The results show that the extinction limit of fuel velocity under buoyant condition is much lower than that without buoyancy. Moreover, hydrogen flames under buoyant condition attatch the nozzle exit for all fuel velocities investigated; however, the flames without buoyancy surround the lower wall at low fuel velocity. In addition, combustion is nearly complete in the presence of buoyancy, whereas the combustion efficiency under non-buoyant condition is below 45%. Furthermore, flame temperature under buoyant condition is much higher compared to the counterpart under non-buoyant condition at low and moderate fuel velocities. Analysis reveals that in the case without buoyancy, the negative gauge pressure in the annular space is unable to entrain sufficient air from the ambient. Hence, hydrogen has to diffuse downwards to sustain the flame and complete combustion is unrealizable.



中文翻译:

浮力对封闭在小管中的氢扩散火焰的影响

在这项工作中,数值研究了在没有空气共流的情况下,密闭在小管中的氢喷射火焰的浮力效应。结果表明,在浮力条件下,燃料速度的消光极限远低于无浮力条件。此外,对于所有研究的燃料速度,在浮力条件下的氢火焰都在喷嘴出口处。但是,没有浮力的火焰以较低的燃料速度围绕着下壁。另外,在有浮力的情况下燃烧几乎完成,而在非浮力条件下的燃烧效率低于45%。此外,在低和中等燃料速度下,浮力条件下的火焰温度比非浮力条件下的火焰温度高得多。分析表明,在没有浮力的情况下,环形空间中的负表压无法从周围环境带走足够的空气。因此,氢必须向下扩散以维持火焰,并且完全燃烧是无法实现的。

更新日期:2020-07-21
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