Combustion Characteristics of Biogas Fuel Using Particularly Simplified Reaction Mechanism for HCCI Engines

Abstract

Renewable energy resources like biogas fuel are highly needed to overcome the increasing demands on energy and to allow more efficient power transformation. Biogas is not investigated adequately in homogenous charge compression ignition (HCCI) engines and no specific chemical kinetics were proposed for its combustion in HCCI engines. In this study, a reaction mechanism had been proposed to simulate biogas combustion in HCCI engines. A combined mechanism reduction algorithm, using a graph-based approach and sensitivity analysis, was used to reduce a full detailed mechanism for C1-C4 hydrocarbon fuels. The resulted mechanism consists of 42 species and 328 reactions that were selected to predict the ignition delay time of the HCCI ignition process. The new mechanism was implemented in a modified multizone combustion model using CANTERA flow reactions and MATLAB software. Many combustion parameters, including pressure and temperature profiles, ignition time, produced work, and heat release rate, were estimated. It was found that HCCI engines fueled with biogas can be an effective option for power generation applications at wide range of CH4-CO2 ratios. Furthermore, the reaction mechanism showed high ability in predicting the experimental data at HCCI operation conditions over a wide range of temperature (500–2,000 K) and equivalence ratios (0.4–1.8). This allows further investigations of the mechanism for combustion and emissions prediction at many different operation conditions.