Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity

Junjie Hong, Ming Zhao, Lei Liu, Qiuxiang Shi, Xi Xiao and Aiwu Fan
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Junjie Hong: China Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, China
Ming Zhao: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China
Lei Liu: China Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, China
Qiuxiang Shi: China Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, China
Xi Xiao: China Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, China
Aiwu Fan: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China

Energies, 2021, vol. 14, issue 15, 1-12

Abstract: Microjet hydrogen flames can be directly used as micro heat sources or can be applied in micro propulsion systems. In our previous study, under zero gravity and without an active air supply, the combustion completeness of hydrogen jet flames within a mesoscale tube with an inner diameter of 5 mm was very low. In this study, we were dedicated to improving the combustion efficiency by using a convergent nozzle (tilt angle was around 68°) instead of the previous straight one, and the exit diameter was 0.8 or 0.4 mm. The numerical results demonstrate that the maximum combustion efficiency in the case of d= 0.8 mm was only around 15%; however, the peak value for the case of d = 0.4 mm was around 36%. This happened because with d = 0.4 mm, the fuel jet velocity was around four times that of the d = 0.8 mm case. Hence, the negative pressure in the combustor of d = 0.4 mm decreased to a much lower level compared to that of d = 0.8 mm, which led to an enhancement of the air entrainment ratio. However, the highest combustion efficiency of d = 0.4 mm was still below 36%; therefore, a slightly larger tube or an even smaller nozzle exit diameter will be necessary for further improvements to the combustion efficiency.

Keywords: combustion efficiency; micro-jet flame; air entrainment ratio; flame shape; flame tip opening (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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