Experimental and Numerical Investigation into the Effect of Fuel Type and Fuel/Air Molar Concentration on Autoignition Temperature of n-Heptane, Methanol, Ethanol, and Butanol

Abstract

The effect of fuel type, fuel molar concentration, and air molar concentration on the autoignition temperature (AIT) of n-heptane, methanol, ethanol, and butanol, under a wide range of conditions (φ = 0.4–2.0, Pinit = 80–500 psi), is investigated using a constant volume bomb. The results indicate that the AIT generally decreases as the chain length and molecular weight each increase. The AIT decreases as the fuel molar concentration, as well as air molar concentration, increase. The AIT of n-heptane remains approximately constant (280 °C) as the fuel/air molar concentration increase. While the AIT of methanol, ethanol, and butanol decrease from 548 °C to 479 °C, from 450 °C to ∼371 °C, and from 401 to 342 °C, respectively, with increasing fuel/air molar concentration. Numerical study is performed to identify the cause of AIT variation using validated comprehensive reaction mechanisms of n-heptane and methanol. The AIT of n-heptane remains almost constant under wide parameters, because of the low activatio...