Effect of N 2 and CO 2 on explosion behavior of H 2 -Liquefied petroleum gas-air mixtures in a confined space

In this study, the explosion behaviors of H 2 -LPG-air mixtures with 30% H 2 fraction under the action of N 2 and CO 2 were experimentally investigated respectively under the initial conditions of 1 atm and 298 K. Furthermore, the mole fraction and the rate of production (ROP) of free radicals were analyzed with reference to the detailed USC-Mech II mechanism. The results show that the addition of N 2 and CO 2 reduces the maximum explosion pressure and maximum rate of pressure rise of H 2 -LPG-air mixtures; it also postpones the arrival of explosion peak. The minimum suppression concentrations of inert gases are 35% N 2 and 25% CO 2, respectively. Compared with the addition of N 2, the addition of CO 2 with the same volume fraction boasts a better inhibitory effect on H 2 -LPG-air mixture explosion. The reason is as follows: N 2 mainly inhibits explosion by its physical properties. In contrast, CO 2 also participates in the chemical elementary reactions R31: CO + OH CO 2 +H, consumes free radical H and reduces its concentration. Meanwhile, the main elementary reactions affecting the generation and consumption of free radicals H, O and OH are R1, R3 and R31. The addition of N 2 and CO 2 decreases the maximum ROP of free radicals H, O and OH, and CO 2 with a high concentration has a significant effect on the maximum ROP of the elementary reaction R31.