The Autoignition Chemistry of Isobutane: A Motored Engine Study

Isobutane autoignition chemistry was examined in a motored, single-cylinder engine by measuring stable intermediate species, performing heat release analyses, and measuring visible emissions. The engine was motored at speeds of 600 and 1600 r/min, and compression ratio was varied to affect different levels of chemical activity.

At 1600 r/min, species measurements, heat release and visible emissions all exhibited a “negative-temperature” coefficient region; thus, “intermediate-temperature” chemistry controls autoignition at 1600 r/min. By implication, classic “low-temperature” chemistry controls at 600 r/min. Experimental measurements are compared with isobutane literature values, with previous n-butane results, and specific isobutane autoignition chemistry is discussed an light of the measurements.