Experimental study and theoretical calculation of flammability limits of methane/air mixture at elevated temperatures and pressures

• The flammability limits of methane/air mixture are investigated experimentally.
• The calculated LFL results are valid by using limiting flame temperature concept.
• The temperature dependence of geometric mean G is constant at a certain pressure.
• The UFLs are predicted accurately using temperature dependence of geometric mean G.

The flammability limits of methane/air mixture were experimentally studied at a temperature range of 30–150 °C and a pressure range of 0.1–0.9 MPa. The lower flammability limit (LFL) was calculated using a limiting flame temperature concept (White's role) and the temperature dependence of geometric mean G was also defined to predict the upper flammability limit (UFL). The results show that in our experiment, the influence of temperature and pressure on flammability limits show accordance with previous studies. The calculated LFL results using limiting flame temperature concept shows good agreement with the experimental values. The temperature dependence of geometric mean G remains unchanged at a certain pressure no matter what the temperature is. Within the temperature range examined in this paper, the UFL results can be predicted very accurately using the temperature dependence of geometric mean G. However, it is worth noting that with the increase of the initial temperature, the difference between experimental UFL and calculated UFL using geometric mean G becomes larger.