Integrated 1D-chemical kinetics model of a diesel and biodiesel fuelled light-duty diesel engine

Abstract

In recent years, advances in numerical modelling of engines have led to the integration of 3-dimensional computational fluid dynamics with chemistry to calculate both the physical flow field and complex chemical reactions. However, it is only feasible to simulate the combustion chamber, but not the entire engine due to simulation runtime limitations. Onedimensional (1D) simulations of an entire engine are rapid yet comprehensive, but focus only on the applied thermodynamics with rudimentary global reaction chemistry. In this study, a compact combined biodiesel-diesel chemical kinetics reaction mechanism is integrated into the 1D modelling of a complete engine. Entire engine cycle from air intake to exhaust product is simulated using commercial software, AVL Boost. This allows for rapid system-level simulation which takes into account applied thermodynamics with complex chemical kinetics to account for combustion and pollutant formation. The integrated 1D-chemical kinetics model is successfully validated against experimental data with both the diesel and palm biodiesel fuel for key combustion parameters. The model would be able to simulate any dieselbiodiesel mixture of any blend levels and also biodiesel produced from different feedstock. This is due to the reaction mechanism comprising of n-Heptane, methyl butanoate and methyl crotonate which are the surrogate fuel models of straight chain hydrocarbon, saturated fatty acid methyl ester (FAME) and unsaturated FAME, respectively. Thus, CME, PME, and SME, are selected for blending due to their innate FAME proportions to represent the high, medium, and low saturated:unsaturated biodiesel, respectively. In all, through 100 simulated cases, this study demonstrated the feasibility of integrating chemical kinetics into 1D numerical model for a complete engine. Ultimately, the use of an integrated 1D-chemical kinetics model for engine simulations can greatly reduce optimisation time for emissions reduction.