Dispersion Behavior after Leakage of Hydrogen-Blended Natural Gas

Hydrogen exhibits high diffusivity, a wide flammable range, and strong chemical reactivity.When mixed with natural gas, hydrogen substantially intensifies the dispersion risk during leakage events and increases the probability of explosions, posing serious threats to industrial operations as well as the safety of nearby personnel and infrastructure.In order to investigate the dispersion behavior and associated safety risks of hydrogen-blended natural gas (HBNG) under pipeline failure scenarios, this study developed a three-dimensional numerical model simulating HBNG leakage and dispersion.The model employed the standard k-ε turbulence framework coupled with species transport equations and was validated against existing experimental data.Using this model, the study systematically examined the influence of key factors, including hydrogen blending ratio, leakage rate, leakage direction, ventilation conditions, and the presence of obstacles, on the dispersion process.The spatiotemporal evolution of gas concentrations reaching the alarm concentration and the lower explosive limit was comprehensively analyzed.Results demonstrate a significant negative correlation between the hydrogen blending ratio, leakage rate, and emergency response time.At a constant mass leakage rate, increasing the hydrogen content to 20% shortens the alarm response time by 22%, compared to a 17.5% reduction under constant volumetric leakage conditions.Additionally, impaired ventilation conditions reduce the response time from 500 s to only 25 s, while the presence of obstacles decreases it by 50 s, notably exacerbating safety hazards.This study reveals the mechanisms behind the multifactor coupling effects on HBNG dispersion in complex environments and provides theoretical insights and technical support for safety assessment and risk mitigation strategies in industrial applications.