Experimental Study on Methane Explosion Suppression in Pipelines by Mixed Systems of Inert Gases (CO2/N2) and HFC-227ea

Abstract To address the high inert gas demand and cost of heptafluoropropane (HFC-227ea) in gas explosion prevention, a custom-built pipeline experimental platform was employed to investigate the suppression effects of CO2, N2, and HFC-227ea on 9.5% methane explosions. A BOPP film separated the explosion and suppression zones to simulate nonpremixed conditions. The peak overpressure and average flame propagation speed were analyzed to evaluate suppression characteristics and the influence of film-breaking. Results show that CO2 outperforms N2 at equal volume fractions; both achieve the optimal suppression effect within the tested concentration range at 40%, reducing the peak overpressure by 25.8% and 24.4% and the flame speed by 40.1% and 34.0%, respectively. HFC-227ea exhibits strong chemical inhibition at low concentrations (2–8%), achieving 51.4% flame speed reduction at 8%. In mixtures with the total concentration fixed at 40%, suppression performance improves with higher HFC-227ea proportion. The 32% CO2/8% HFC-227ea mixture reduces the peak overpressure by 35.3% and the flame speed by 62.9%, outperforming pure CO2 at the same total concentration. No marked synergy is observed at low HFC-227ea ratios, likely due to film-breaking effects induced by BOPP membrane rupture. These findings provide theoretical and technical support for optimizing explosion suppression media in confined industrial spaces, suggesting a potentially cost-effective solution for engineering applications.