Flammability limits of iso-butanol/iso-octane/n-heptane blends

A set of experiments was carried out to determine the flammability limits (FL) of blends of iso-butanol and a surrogate fuel for gasoline at 154 +/- 11 degrees C and approximate to 91.4 kPa. The surrogate gasoline was a binary PRF mixture of 87% iso-octane and 13% n-heptane (PRF 87). The volumetric fraction of iso-butanol in the liquid fuel was varied from 0 to 0.25 at a step of 0.05. Flammability tests with pure fuels were also performed to confirm the reliability of the applied experimental procedure. The homogeneous air/fuel mixtures were defined as flammable when formed a self-sustained flame able to travel upward a 0.3 m long open combustion tube. The lower FL of the blends of iso-butanol and PRF 87 (0.80-0.98%) were estimated correctly with the mixing rule of La Chatelier, but the same simplified model failed to reproduce the measured upper flammability limits (5.10-5.61%).