Comparative Investigation of the High Pressure Autoignition of the Butanol Isomers

TL;DR

This study compares the autoignition delays of butanol isomers at high pressures and varying temperatures, revealing differences in reactivity and unique pre-ignition behavior of tert-butanol under specific conditions.

Contribution

It provides new insights into the autoignition characteristics of butanol isomers at elevated pressures, including reactivity rankings and heat release phenomena.

Findings

Reactivity ranking varies with pressure: n-butanol > sec-butanol ~ iso-butanol > tert-butanol at 15 bar.

At 30 bar, the ranking shifts to n-butanol > tert-butanol > sec-butanol > iso-butanol.

Tert-butanol exhibits unique pre-ignition heat release behavior under studied conditions.

Abstract

Investigation of the autoignition delay of the butanol isomers has been performed at elevated pressures of 15 bar and 30 bar and low to intermediate temperatures of 680-860 K. The reactivity of the stoichiometric isomers of butanol, in terms of inverse ignition delay, was ranked as n-butanol > sec-butanol ~ iso-butanol > tert-butanol at a compressed pressure of 15 bar but changed to n-butanol > tert-butanol > sec-butanol > iso-butanol at 30 bar. For the temperature and pressure conditions in this study, no NTC or two-stage ignition behavior were observed. However, for both of the compressed pressures studied in this work, tert-butanol exhibited unique pre-ignition heat release characteristics. As such, tert-butanol was further studied at two additional equivalence ratios ($\phi$ = 0.5 and 2.0) to help determine the cause of the heat release.