Optimization of injection strategy to reduce fuel consumption for stoichiometric diesel combustion

In the present study, optimization of engine operating conditions was performed to reduce fuel consumption for stoichiometric diesel combustion. Microgenetic algorithms were used, and variations of injection strategy, spray included angle, and initial conditions (such as temperature and pressure) were evaluated. The KIVA code, coupled with the Chemkin chemistry solver, was used for three-dimensional CFD modeling, and the ignition and combustion processes were modeled using a reduced n-heptane mechanism. The KIVA code in use was verified against pressure histories and emissions for stoichiometric diesel combustion obtained experimentally. Optimized engine operating conditions for minimum fuel consumption were found at the 43rd generation. The optimized case includes 50-50% split injection, reduced spray included for reduction of unburned HC in crevices, and lower oxygen concentration to retard combustion phasing. This optimization yielded an 11.8% improvement in fuel consumption, along with simultaneous reductions of soot, NOx, CO, and HC. (C) 2011 Elsevier Ltd. All rights reserved.