Experimental and modeling study of C2-C4 alcohol autoignition at intermediate temperature conditions

C2–C4 alcohols are advantageous blendstocks towards enabling efficient, boosted Spark-Ignition (SI) engines. Their use in advanced engine applications requires a comprehensive understanding of their intermediate-temperature autoignition behavior. An experimental and modeling study covering their fundamental autoignition characteristics in a twin-piston rapid compression machine at pressures of 20 and 40 bar, intermediate temperatures from 750 to 980 K, and two fuel loading conditions representative of boosted SI engines was conducted. Direct comparison between these alcohols was made, where the order of reactivity is established across different thermodynamic and fuel loading conditions. Changes in preliminary exothermicity (or intermediate-temperature heat release) displayed in single-stage autoignition across different alcohols and conditions were quantified, providing insight into fuel-to-fuel differences, and how these could affect advanced combustion concepts. Kinetic models were used to simulate the experiments, and reasonable agreement was obtained. The sensitivity analysis results demonstrated the importance of accurately capturing the autoignition kinetics, particularly H-abstraction reactions on the parent fuels by OH and HO₂, and the branching ratio associated with these.