Synergistic suppression of hydrogen-air explosions by propane/CO2 and functionalized zeolite powder/CO2

The high CO 2 concentrations required for suppressing confined hydrogen explosions severely limit its practical application. To address this, the synergistic suppression effects of C 3 H 8 /CO 2 and ZPU (zeolite/KH 2 PO 4 /urea)/CO 2 systems were evaluated in a 20 L spherical vessel across hydrogen-air equivalence ratios of ϕ = 0.4-1.6. The results show that 2.0% C 3 H 8 reduces the critical CO 2 concentration at ϕ = 1.0 from 42% to 8%. The maximum synergistic enhancement factor reaches 93%, with an apparent amplification factor of approximately 8.6. Sensitivity analysis suggests CH 3 -mediated radical recombination (R88) contributes to flame inhibition in stoichiometric and fuel-rich mixtures. The gas-solid ZPU/CO 2 system achieves a 65% maximum synergistic enhancement factor. Characteristic-time modeling suggests that CO 2 -induced flame deceleration may provide additional time for powder decomposition. The gas-gas scheme saves 17 g CO 2 per gram of C 3 H 8 , exhibiting Pareto dominance over the gas-solid scheme. Nevertheless, the gas-solid approach remains suitable for scenarios strictly prohibiting combustible components.