A Novel NOx Correlation for CI Engine Using Multidimensional Detailed Chemistry

Abstract

This paper presents a numerical investigation on a single cylinder direct injection compression ignition engine. Calculations are achieved with kiva3v2 code involving a reduced C7H16 reaction mechanism and a set of sixty species. The study has been carried out on predicted NO and NOx emission levels at the exhaust phase during the late slow diffusion combustion using the asymptotic approach. Simulations have been achieved for five loads (20%, 40%, 60%, 80% and 100%) at 1500 rpm. Predicted values of averaged pressures, O2, CO and CO2 levels in the exhaust manifold have been validated by the ones measured on engine test bench. Algebraic correlations proposed for predicted NO and NOx levels use fuel, O2, N2 concentrations and the maximum in-cylinder temperature. The numerical results of NO and NOx concentrations at the exhaust are in perfect concordance with the measured ones. In addition, numerical investigations help analyzing and predicting the injection timing effect on engine performances as well as NOx emissions. According to the results obtained, the closer the start of injection is to top dead center, the lower the NOx levels at the exhaust are.