Modelling Diesel Combustion

Phenomenology of Diesel Combustion and Modeling Diesel is the most efficient combustion engine today and it plays an important role in transport of goods and passengers on land and on high seas. The emissions must be controlled as stipulated by the society without sacrificing the legendary fuel economy of the diesel engines. These important drivers caused innovations in diesel engineering like re-entrant combustion chambers in the piston, lower swirl support and high pressure injection, in turn reducing the ignition delay and hence the nitric oxides. The limits on emissions are being continually reduced. The- fore, the required accuracy of the models to predict the emissions and efficiency of the engines is high. The phenomenological combustion models based on physical and chemical description of the processes in the engine are practical to describe diesel engine combustion and to carry out parametric studies. This is because the injection process, which can be relatively well predicted, has the dominant effect on mixture formation and subsequent course of combustion. The need for improving these models by incorporating new developments in engine designs is explained in Chapter 2. With “model based control programs” used in the Electronic Control Units of the engines, phenomenological models are assuming more importance now because the detailed CFD based models are too slow to be handled by the Electronic Control Units. Experimental work is necessary to develop the basic understanding of the pr- esses.

The diesel engine is the most efficient combustion engine today and it plays an important role in transport of goods and passengers by land and sea. However, the emissions must be controlled without sacrificing the legendary fuel economy of the diesel engines. These important drivers have caused innovations in diesel engineering like re-entrant combustion chambers in the piston, lower swirl support and high pressure injection, in turn reducing the ignition delay and hence the nitric oxides.

This book is a detailed discussion of diesel combustion phenomena like ignition delay, fuel air mixing, rate of heat release, and emissions of smoke, particulate and nitric oxide. It enables quantitative evaluation of these important phenomena and parameters. Most importantly, it attempts to model them with constants that are independent of engine types.

This work recognises the importance of the spray at the wall in precisely describing the heat release and emissions for most of the engines on and off road. It gives models for heat release and emissions. Every model is thoroughly validated by detailed experiments using a broad range of engines. Throughout the book, the models use constants that are independent of engine type or design and hence they could be applied by the designer and researcher for a general engine. All the models not only describe the trends of important parameters but also quantitatively close to the experimentally observed results.

The enhanced understanding of the phenomena like turbulent flows, high-pressure sprays naturally converges to quantitative prediction using multi-dimensional CFD tools to reveal finer details of in-cylinder processes of diesel combustion. The CFD tools are introduced with case studies in two chapters of the book to help study innovative combustion concepts and improve engine designs in terms of emissions reduction and fuel economy.