Emission characteristics and combustion simulation of biodiesel−diesel blends using a reduced mechanism

Abstract The study presents the development and validation of a reduced biodiesel combustion mechanism consisting of 168 species and 1018 reactions, derived from the Lawrence Livermore National Laboratory (LLNL) detailed mechanism containing 3299 species and 10,806 reactions. The reduction process, employing Directed Relation Graph with Error Propagation (DRGEP) and Path Flux Analysis (PFA), is based on a surrogate blend of methyl decanoate (MD), methyl‐9‐decenoate (MD9D), and n‐heptane, which effectively represents the molecular structure of biodiesel's key constituents with varying degrees of unsaturation. The reduced mechanism is evaluated through homogeneous auto‐ignition and perfectly stirred reactor (PSR) combustion simulations under distinct combustion conditions. The combustion simulations of three biodiesel‐diesel blends—100% biodiesel, 50% biodiesel‐50% diesel, and 100% diesel—were performed using the reduced mechanism mentioned above to analyze pollutant emissions, including carbon monoxide (CO), unburned hydrocarbons (UHC), acetylene (C 2 H 2 ), and nitrous oxides (NO, and NO 2 ). The results indicate that 100% diesel generates the highest emissions, while 100% biodiesel produces the lowest due to its higher oxygen content, which enhances combustion efficiency. However, 100% biodiesel's widespread usage is constrained by its high cost, poor low‐temperature performance, and compatibility issues. The optimal balance between emissions reduction, cost, cold‐weather performance, and engine compatibility was achieved with a 50% biodiesel‐50% diesel blend, as its emission values fall between those of pure biodiesel and pure diesel. This study underscores the potential of biodiesel‐diesel blends in reducing pollutant emissions while addressing practical limitations associated with pure biodiesel usage.