A Parametric Analysis of Exhaust Emissions Prediction during Transient Turbocharged Diesel Engine Operation

The modeling of turbocharged diesel engine transient operation appeared in the early 1970s and continues to be in the focal point of research due to the importance of transient response in the everyday operating conditions of engines. Simulations of various levels of complexity have been used so far to study engine performance during transients. On the other hand, the very important issue of exhaust emissions has been studied mainly on an experimental rather than simulation basis, owing to the high computational time required for the analysis of many cycles. The study of transient emissions from turbocharged diesel engines is extremely important for the manufacturers, since newly produced engines must meet the stringent regulations concerning exhaust emissions levels. In the present work, a comprehensive two-zone transient diesel combustion model is used for a parametric analysis of exhaust emissions prediction during load changes. The parameters studied are the load characteristics (magnitude and change schedule), the exhaust manifold volume, the geometric turbine inlet area as well as the exhaust valve opening timing. Also, the very interesting case of insulated cylinder walls is investigated. Analytical diagrams are provided for the time histories of nitric oxide (NO) and soot emissions, which depict the effect of each parameter considered. Moreover, the peculiarities of each case are discussed mainly in relation to turbocharger lag effects.