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Effects of ventilation and hydrogen blending ratio on confined combustion dynamics of leaked hydrogen-blended natural gas in utility tunnels.

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Title: Effects of ventilation and hydrogen blending ratio on confined combustion dynamics of leaked hydrogen-blended natural gas in utility tunnels.
Authors: Zhong, Wei1 (AUTHOR), Wang, Wenxue1 (AUTHOR), Liang, Tianshui1 (AUTHOR), Fu, Huiming2 (AUTHOR), Wang, Jiabang2 (AUTHOR), Song, Yifan1 (AUTHOR) syfsyf@zzu.edu.cn
Source: International Communications in Heat & Mass Transfer. Dec2025:Part B, Vol. 169, pN.PAG-N.PAG. 1p.
Subjects: Ventilation, Natural gas, Flame spread, Leakage, Combustion engineering, Tunnels, Detonation waves, Combustion kinetics
Abstract: Hydrogen-blended natural gas (HBNG) transport via existing natural gas pipelines introduces unique buoyancy-driven leakage and combustion challenges within confined underground infrastructure such as utility tunnels. This study numerically investigates ventilation rate and hydrogen blending ratio (HBR) effects on leaked HBNG dispersion and explosions using a full-scale tunnel model. After 190 s of leakage, the dispersion stabilizes. The HBNG accumulates downstream and forms a vertically stratified concentration, decreasing from the ceiling to the floor due to buoyancy. Increased hydrogen blending ratios elevate the stabilized mixture concentration, while higher ventilation rates accelerate stabilization through enhanced convective mixing and dilution. Upon ignition, flame propagation exhibits distinct wall-attachment, intensifying with higher HBRs and ventilation rates due to altered flow-flame interaction. Explosion overpressure curves show a characteristic double-peak pattern. This pattern is attributed to sequential combustion near walls and within the core flow. Maximum overpressure decreases with increasing ventilation rate, reaching a minimum value of 0.137 MPa at 24 times/h and a 40 % HBR. The location of peak overpressure shifts upstream toward the leak source as ventilation intensifies, highlighting the impact of flow conditions on explosion wave development. These findings quantify fundamental heat and mass transfer processes governing HBNG safety, informing ventilation design and structural protection. • Buoyancy-driven stratification dominates HBNG dispersion. • Ventilation controls flammability through convective dilution. • Flame-wall interaction intensifies with HBR and ventilation. • Ventilation reduces overpressure and shifts peak location. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Hydrogen-blended natural gas (HBNG) transport via existing natural gas pipelines introduces unique buoyancy-driven leakage and combustion challenges within confined underground infrastructure such as utility tunnels. This study numerically investigates ventilation rate and hydrogen blending ratio (HBR) effects on leaked HBNG dispersion and explosions using a full-scale tunnel model. After 190 s of leakage, the dispersion stabilizes. The HBNG accumulates downstream and forms a vertically stratified concentration, decreasing from the ceiling to the floor due to buoyancy. Increased hydrogen blending ratios elevate the stabilized mixture concentration, while higher ventilation rates accelerate stabilization through enhanced convective mixing and dilution. Upon ignition, flame propagation exhibits distinct wall-attachment, intensifying with higher HBRs and ventilation rates due to altered flow-flame interaction. Explosion overpressure curves show a characteristic double-peak pattern. This pattern is attributed to sequential combustion near walls and within the core flow. Maximum overpressure decreases with increasing ventilation rate, reaching a minimum value of 0.137 MPa at 24 times/h and a 40 % HBR. The location of peak overpressure shifts upstream toward the leak source as ventilation intensifies, highlighting the impact of flow conditions on explosion wave development. These findings quantify fundamental heat and mass transfer processes governing HBNG safety, informing ventilation design and structural protection. • Buoyancy-driven stratification dominates HBNG dispersion. • Ventilation controls flammability through convective dilution. • Flame-wall interaction intensifies with HBR and ventilation. • Ventilation reduces overpressure and shifts peak location. [ABSTRACT FROM AUTHOR]
ISSN:07351933
DOI:10.1016/j.icheatmasstransfer.2025.109686