Explosion dynamics of hydrogen-blended natural gas perturbed by CO2 injection in a closed duct

This study investigates flame propagation and overpressure dynamics of hydrogen-blended natural gas (hydrogen blending ratio, X H2 = 0-0.8) perturbed by CO 2 injection in a closed duct. CO 2 was injected with an injection time ( t inject ) varied from 0 to 600 ms, and an initial pressure of 1.00 MPa. Results show that CO 2 injection wrinkles the flame front by turbulent perturbations, promoting flame acceleration. Jet exhibits a stimulating effect, causing the most severe explosion at t inject = 60 ms. As CO 2 injection exceeds 60 ms, the dilution effect gradually increases, weakening the turbulent enhancement and reducing the explosion intensity. CO 2 injection of 300 ms is a critical time, causing a transition from explosion-promoting to explosion-suppressing. For a given X H2 , the maximum overpressure and flame velocity first increase and then decrease with t inject . Lower X H2 requires a shorter injection time to reach the lowest flammability limit and exhibits greater sensitivity to CO 2 injection.