Flammability envelopes for methanol, ethanol, acetonitrile and toluene

The flammability envelope was experimentally determined up to the point of vapor saturation for four flammable liquids: methanol, ethanol, acetonitrile, and toluene. The experimental apparatus consisted of a 20-L spherical chamber with a centrally located 10 J fuse wire igniter. The liquid was injected and vaporized into the chamber via a septum and a precision syringe. Nitrogen and oxygen were mixed from pure components using a precision pressure gauge. Pressure versus time data were measured for each ignition test. Flammability was defined as any ignition resulting in an increase in pressure of 7% over the initial pressure, as per ASTM E 918–83. All data were obtained at an initial temperature of 298 K and 1 atm. The experimental values of the LFL agreed well with published values. Limiting oxygen concentrations (LOC) were also determined—although these were somewhat lower than published values. The calculated adiabatic flame temperature (CAFT) method was used to model the data using a threshold temperature of 1200 K. A reasonable fit of the flammability envelope was obtained, although this could be improved with a higher threshold temperature.