Assessment of a Detailed Kinetic Diesel Combustion Model by In-Cylinder Optical Measurements

The main objective of the present paper is the application of a detailed kinetic model to study diesel combustion in an optical accessible engine equipped with a common rail injection system. Three different injection schedules made of one to three consecutive injections are considered from both the numerical and the experimental point of view. The numerical model is assessed in such a way to assure its portability with respect to changing injection strategies.

The employed detailed kinetic mechanism consists of 305 reactions involving 70 species and is included in the KIVA-3V code. The considered fuel has the liquid phase properties of the diesel oil, the vapor phase properties of C14H28. It is subsequently decomposed into n-heptane and toluene. The chemical solver is based on the use of the reference species technique and on the Partially Stirred Reactor (PaSR) hypothesis. These allow maintaining the computational cost within acceptable limits.

A comparison with experimental data is made regarding the in-cylinder pressure, the visualization of the spray evolution, the temperature and OH radical distribution during the combustion process, as well as the time history of the measurable soot amount within the combustion chamber. Tail pipe emissions are also compared with the values of the in-cylinder soot and NO_x amount at the end of the expansion stroke.