Research on the mechanism of explosion wave and flame evolution of green H2- blended natural gas pipeline leakage

Abstract

Green hydrogen (H₂) as a renewable energy has been developing in recent years. Natural gas blended with H₂ is often burned at a distance following leaking, which is a low-equivalent combustion with unclear combustion and explosion characteristics and coupling mechanisms. The problem is solved by determining the parameters of explosion and flame for natural gas/H₂/air using experimentation with high-speed cameras and sensors and simulation with GRI-Mesh 3.0. Results show that the explosion wave evolution is divided into intensification and steady development stage. The flame propagation undergoes a “bimodal” pattern of primary acceleration and deceleration and secondary acceleration and deceleration. H₂ enhances the reaction rate and strengthens the positive feedback mechanism, creating the enhancement of overpressure (43.69 %), explosion wave velocity (17.31 %), and flame propagation velocity (80.96 %). In the low-equivalent case, the H₂ capture reaction depletes the H in the reaction system, reducing the intensity of the explosion hazard. Repeated coupling and decoupling occur during the propagation of the explosion wave and flame, causing flame acceleration, deceleration, flame compression, and oscillatory propagation. The prediction model of explosion overpressure, flame temperature, and flame velocity is obtained. It provides a valuable reference for the safe transportation and emergency response of H₂.