Experimental and mechanism research on the upper flammability limit of H₂/C₂H₅OH mixture at various temperatures and pressures

The study of the upper flammability limit (UFL) of hydrogen/ethanol mixture at various pressures and temperatures is crucial for the safe production of the ethanol-to-hydrogen process. In this paper, the influences of hydrogen blending ratio, temperature and pressure on the UFL were discussed. Findings indicate that as the mixture system's hydrogen concentration rises, the UFL grows exponentially at various pressures and temperatures. Moreover, the influence of temperature and pressure on the UFL is lessened by the rise in hydrogen content. In addition, high pressure and high temperature have a synergistic effect on the UFL that is not only much more than the amplification of the individual single components but also greater than the sum of their mathematical values. On flame temperature and the main elementary reactions, the impacts of starting pressure and initial temperature have been investigated. The effect of initial temperature on the primary elementary reactions at the UFL is slight. As the pressure increases, the most important elementary reactions that promote temperature rise and those that inhibit temperature rise are changed. Finally, the UFL prediction model for hydrogen/ethanol mixture at elevated temperature and pressure is developed by machine learning. The research results are of great significance to enrich the theory of mixture explosion and to prevent explosion accidents in hydrogen production plants.