Effect of N2 and CO2 on explosion behavior of H2-Liquefied petroleum gas-air mixtures in a confined space

Abstract

In this study, the explosion behaviors of H2-LPG-air mixtures with 30% H2 fraction under the action of N2 and CO2 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 N2 and CO2 reduces the maximum explosion pressure and maximum rate of pressure rise of H2-LPG-air mixtures; it also postpones the arrival of explosion peak. The minimum suppression concentrations of inert gases are 35% N2 and 25% CO2, respectively. Compared with the addition of N2, the addition of CO2 with the same volume fraction boasts a better inhibitory effect on H2-LPG-air mixture explosion. The reason is as follows: N2 mainly inhibits explosion by its physical properties. In contrast, CO2 also participates in the chemical elementary reactions R31: CO + OHCO2+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 N2 and CO2 decreases the maximum ROP of free radicals H, O and OH, and CO2 with a high concentration has a significant effect on the maximum ROP of the elementary reaction R31.