Analysis of combustion and pollutants formation in a direct injection diesel engine using a multi-zone model

Abstract

A two-dimensional multi-zone model for the calculation of the closed cycle of a direct injection (DI) diesel engine is presented. The fuel spray is divided into small packages and the effect of air velocity pattern on spray development is taken into account. The calculation of swirl intensity variations during the cycle is based on hybrid solid body-boundary layer rotation scheme. Application of the mass, energy and state equations in each zone yields local temperatures and cylinder pressure histories. For calculating the concentration of constituents in the exhaust gases, a chemical equilibrium scheme is adopted for the C-H-O system of the eleven species considered, together with chemical rate equations for the calculation of nitric oxide (NO). A model for the evaluation of soot formation and oxidation rates is incorporated. A comparison is made between the theoretical results from the computer program implementing the analysis, with experimental results from a vast experimental investigation conducted on a direct injection, Lister-Petter diesel engine, with very encouraging results. Plots of temperature, equivalence ratio, NO and soot distributions inside the combustion chamber are presented, elucidating the physical mechanisms governing combustion and pollutants formation.