Preliminary Studies on the Effects of Injection Rate Modulation on the Combustion Noise of a Common Rail Diesel Engine

The present work deals with tests on a DI Diesel engine equipped with two different types of Common Rail injectors, the second one allowing a “smoother” fuel rate in the first stage of injection. The work aims at understanding how injection parameters and different injection rates may affect the combustion process in terms of in-cylinder pressure, noise and vibrations of the engine block. The tests performed for the same engine torque generally showed that engine speed, injection pressure and pilot injection duration are the most significant parameters that affect engine noise emissions. As regards the injection rate modulation, experiments showed that it is possible to reduce combustion noise at low engine speeds if the initial rate of injection is lower during the first stage of injection.