Insight into the spontaneous combustion mechanism and characteristics of the hydrogen-blended natural gas during the leakage process: A numerical study

This paper uses Fluent software to develop a multi-field-coupled model for HBNG pipeline leakage. Flow characteristics, chemical reactions, and electrostatic interactions on the spontaneous combustion mechanism are investigated. The criterion is determined by temperature and OH-mass fraction. Considering different conditions (hydrogen volume fraction 0-30 %, leakage pressure 4-10 MPa, leakage hole diameter 5-100 mm, pipe wall thickness 15-35 mm, static electricity intensity 0-0.5V), this paper studies 28 cases and explores the effects of diffusion ignition and electrostatic ignition mechanism on HBNG spontaneous combustion. Results show that: with the increasing of hydrogen volume fraction, leakage pressure, leakage hole diameter, and pipe wall thickness, the temperature, OH-mass fraction and the possibility of self-ignition in the leakage process increase. The effect of electrostatic intensity on spontaneous combustion is relatively small. HBNG satisfies the spontaneous combustion criterion in the extreme spontaneous combustion condition. The maximum temperature and OH-mass fraction respectively reach 1632.6 K and 6.15 x 10-4.