Effects of Propane on the Flammability Limits and Chemical Kinetics of Methane–Air Explosions

This work presents a comprehensive account of how adding C3H8 impacts the possibility of explosion for CH4–air mixtures. A series of experiments was carried out to determine the upper and lower flammability limits (UFL and LFL, respectively), and the explosive risk value for different mixtures of CH4 and C3H8. The critical oxygen concentration, the concentrations of CH4 and N2 at the point where the LFL and UFL merge, and the CH4 explosive triangle were obtained for nitrogen-diluted mixtures. In addition, we used a detailed mechanism (GRI-Mech3.0) in the CHEMKIN software package to acquire the impacts of adding C3H8 on the chemical kinetics of the explosion of CH4. The flammable limits of CH4 decrease linearly with the addition of C3H8 while the flammable range increases slightly. The explosive risk value for CH4 in air increases greatly upon adding C3H8 following a parabolic relationship. Nitrogen dilution noticeably decreases the UFL and slightly increases the LFL, ultimately resulting in these points merging. The concentration of CH4 and nitrogen at this merging point varies linearly when the C3H8 concentration is varied between 0% and 2.0%. The addition of C3H8 also expands and shifts leftwards and downwards CH4’s explosive triangle. Numerical analysis reveals that the maximum temperature and pressure during the explosion, and the formation rates of CO and NOx, noticeably increase after adding C3H8. Sensitivity coefficients of key dominant reactions show that overall more •H, •O, and •OH are consumed when C3H8 is added. Furthermore, the time between ignition and maximum pressure (the burning time) is evidently shortened by the addition of C3H8, which also shortens the explosion duration.