Effect of initial temperature on the explosion pressure of various liquid fuels and their blends

In this work, the effect of initial temperature on the explosion pressure, Pex, of various liquid fuels (isooctane, toluene and methanol) and their blends (isooctane-toluene and methanol-toluene, with three different fuel-fuel ratios) was investigated by performing experiments in a 20-l sphere at different concentrations of vaporized fuel in air. The initial temperature was varied from 333 K to 413 K. Results show that, as the fuel-air equivalence ratio, phi, is increased, a transition occurs from a "thermodynamics-driven" explosion regime to a "radiant heat losses-driven" explosion regime. The maximum pressure, Pmax, is found in the former regime (phi < 3), which is characterized by a trend of decreasing Pex with increasing initial temperature. This trend has been explained by thermodynamics. In the latter regime (phi > 3), Pex increases with increasing initial temperature. This trend has been addressed to the decrease in emissivity (and, thus, radiant heat losses) with the increase in temperature.