Reducing the unwanted deflagration enhancement of C3HF7 on fuel-lean hydrogen-air mixture by diluting CO2: An experimental and numerical research

To prevent the explosion hazards of hydrogen energy, in this work, the deflagration behaviors of H2-air mixtures at equivalence ratios from 0.6 to 1.4 under the effects of C3HF7 and CO2 are experimentally investigated. Deflagration pressure and time indexes at ambient pressure and temperature are obtained. The characteristic parameters of chemical kinetics are analyzed according to a detailed mechanism. The results suggest that C3HF7 has dual effects of pressure enhancement and suppression with the rising volume ratio in fuel-lean H2-air mixtures. It is the F-involved reactions that govern the exothermic process, facilitate the comprehensive conversion of crucial free radicals, and augment the exothermicity of the principal reaction, leading to the elevation in peak pressure. Dilution of CO2 would decrease the heat release rate of the F-involved reactions and reduce the explosion enhancement effect of C3HF7. The results of this work are beneficial to the formulation of mitigation measures for hydrogen explosions.