Chemical Non-Equilibrium Engineering Model of Advanced Combustion Regimes in a Direct-Injected Diesel Engine 2008-01-0842

Recent investigations of advanced combustion have demonstrated that simultaneous low engine-out nitrogen oxides and particular matter emissions are possible, without a decrease in efficiency. So-named High Efficiency Clean Combustion (HECC) or Modulated Kinetics (MK) modes reduce NOx and PM due to low temperature combustion, including premixed combustion along with prolongation of the ignition delay.

Theoretical research using powerful computational tools looks very promising because of the possibility of performing parametric analyses, incorporating simultaneous variation of an unlimited number of engine parameters. Relatively low temperatures in some zones of the diesel engine cylinder corresponding to the HECC regimes require application of chemical kinetics to the numerical simulation of this advanced mode of combustion because of low rates of the chemical reactions compared to the small residence time of the combustion products in the cylinder.

The study reported in this paper focuses on the description of a multi-zone phenomenological model of the combustion process in the diesel engine based on chemical kinetics, which allows analysis of the finite rates of chemical reactions in any zone of the engine cylinder. Fresh air/fuel mixture regions, injected fuel, flame and post flame regions are simulated by Unsteady Well-Stirred Reactors, with application of detailed chemical kinetics to the simulation of the chemical interaction of the operating medium. Any in-cylinder parameters of interest can be predicted, and any effect of these parameters on the operational performance of the engine can be evaluated. Comparison with experimental data for a Mercedes 1.7 liter engine demonstrates the reliability of the theoretical results, dependability of the model, and the ability to provide thorough parametrical analysis applicable to improving the operational performance of a diesel engine.