Under-expansion jet flame propagation characteristics of premixed H2/air in explosion venting. (11th November 2021)

• Record Type: Journal Article
• Authors: Cao, Weiguo; Zhou, Zhuanghong; Li, Wenjuan; Zhao, Yiming; Yang, Zhenxin; Zhang, Yun; Ouyang, Shin-Mei; Shu, Chi-Min; Tan, Yingxin
• Is Part Of: International journal of hydrogen energy. Volume 46:Number 78(2021)
• Page Start: 38913
• Page End: 38922
• Publication Date: 2021-11-11
• Subjects: Hydrogen safety -- Under-expansion structures -- Hydrogen fraction -- Venting diameter -- Duct length; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2021.09.109
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: In premixed H2 /air explosion venting, an under-expansion jet may be caused by the pressure difference between the inside and outside of the explosion vent. Based upon the under-expansion jet, studying the structure of the under-expansion jet flame and the factors influencing its formation is essential to hydrogen safety in explosion venting. This study explored the basic characteristics of the under-expansion jet flame in premixed H2 /air explosion venting, and discussed the formation of two under-expansion structures (Mach disk and diamond shock wave) of such jet flames by conducting a premixed H2 /air explosion venting experiment. The influences of hydrogen fraction, explosion venting diameter, and duct length on the structure of under-expansion jet flames were evaluated. The results showed that after successful explosion venting, the under-expansion jet flame would be generated when the hydrogen fractions were 30–60 vol.%, and as the hydrogen fractions were 30–50 vol.%, the lengths of the venting duct were 30 and 50 cm. The duration of under-expansion jet flame was the longest when the hydrogen fraction was 40 vol.%. With the explosion venting diameter and hydrogen fraction increased, the spacing between under-expansion jet flame structures ( S ) increased. However, an increase in duct length led to the attenuation of the S . During the explosion venting, the under-expansion jet caused a pressure imbalance near the explosion vent and high-intensity convection forms on both sides of a jet, which can generate two or more explosions. Therefore, understanding the basic characteristics of under-expansion jet flame can aid the effective development of measures to prevent, mitigate, and protect against premixed H2 /air explosions. Graphical abstract: Image 1 Highlights: Under-expansion jet flame structure was discussed in the explosion venting of H2 /air. The duration of under-expansion jet flame was the longest at 40 vol% hydrogen. Spacing of the flame structure was reduced with the increase of the duct length. Spacing of the flame structure raised as H2 fraction and venting diameter were added.