4 - Multiple injection diesel combustion process in the high-speed direct injection diesel engine

Abstract

In the diesel engine, the fuel injection system is the heart and it has become one of the critical emissions control technologies with the advance of electronically controlled fuel injection. it is one of the important keys to fulfil the stringent exhaust emissions standards, even if incorrect injection can cause reduced efficiency. In recent years, new injection systems with electronic control have been promoted as the future standard in fuel injection systems for diesel engines, maintaining fuel economy which is directly correlated to the reduction of CO2. among the new injection systems, the advantages claimed of the common rail ones have been the injection rate shaping, the variable timing and the duration of the injection, in addition to variable injection pressure, enabling high injection pressure even at low engine loads and mainly the split of total fuel amount. The split of injection or, better, the use of multiple injection can be considered as the most important aspect of modern diesel injection systems development. With the application of multiple injection technology, improved injection scheme design and better control of engine combustion have been achieved. Moreover, they have been effective in reducing not only NOx and particulate matter but also diesel combustion noise. This chapter presents a few examples of researches carried out on both production and optical engines in combination in order to evaluate the effect of pilot, post- and multiple fuel injection strategies on engine performance and emissions.