Auto-ignition and upper explosion limit of rich propane-air mixtures at elevated pressures

The auto-ignition limits of propane-air mixtures at elevated pressures up to 15 bar and for concentrations from 10 mol% up to 70 mol% are investigated. The experiments are performed in a closed spherical vessel with a volume of 8 dm3. The auto-ignition temperatures decrease from 300 °C to 250 °C when increasing the pressure from 1 bar to 14.5 bar. It is shown that the fuel concentration most sensitive to auto-ignition depends on initial pressure. A second series of experiments investigates the upper flammability limit of propane-air mixtures at initial temperatures up to 250 °C and pressures up to 30 bar near the auto-ignition area. Finally the propane auto-oxidation is modelled using several detailed kinetic reaction mechanisms and these numerical calculations are compared with the experimental results.