Development and validation of a reduced reaction mechanism with a focus on diesel fuel/syngas co-oxidation

• Published in: Fuel (Guildford) Vol. 185; pp. 663 - 683
• Main Authors: Ra, Youngchul, Chuahy, Flavio, Kokjohn, Sage
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2016
• Subjects: Autoignition; Co-oxidation; Multi-fuel; Reaction mechanism; Reactivity controlled compression ignition; Surrogates; Reaction mechanism; Autoignition; Co-oxidation; Multi-fuel; Surrogates; Reactivity controlled compression ignition
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2016.07.039

•A reduced reaction mechanism for diesel/syngas RCCI engine combustion was developed.•Chemistry interaction of multi-component fuels was considered in mechanism reduction.•Conjugate-alkene and immediate lower level ketohydroperoxides should be retained.•Reactions with OH/HO2 have completing/assisting effects on co-oxidation. A reduced reaction mechanism has been developed for modeling Reactivity Controlled Compression Ignition (RCCI) engine combustion with diesel fuel and syngas. Employing n-heptane as a single representative chemical surrogate for diesel fuel, a comprehensive mechanism was reduced such that the reaction mechanism of syngas oxidation is included as a sub-mechanism with emphasis on the interaction of oxidation reaction pathways of syngas and n-heptane. Important reaction pathways to be kept in the reduced mechanism to maintain the performance of the detailed mechanism were identified through ignition delay curve sensitivity analysis. In addition, reaction steps to which ignition delays of multi-fuel blends are sensitive were identified and the importance of predictability of co-oxidation of multi-fuels in the mechanism reduction process was demonstrated. The reduced mechanism, with 81 species and 312 reactions, was validated against experimental ignition delay times available in the literature. The reduced mechanism was also applied to simulate diesel-syngas RCCI engine combustion, employing a multi-component surrogate model to accurately model the physical properties of diesel fuel sprays. Predicted pressure and heat release rate results were compared with engine experimental data and good agreement was observed. The present reduced mechanism gave reliable performance for combustion predictions of RCCI engine operation to help further the fundamental understanding of the process occurring in reformed-fuel RCCI combustion and increase the computational efficiency of multi-dimensional computational fluid dynamics simulations. The reaction mechanism development outlined highlights the importance of considering co-oxidation in generation of reduced reaction mechanisms for applications to dual-fuel combustion.