Effect of Transient Conditions on Combustion Noise of NA-DI Diesel Engines

The combustion noise of four NA-DI Diesel engines (with two different DI combustion systems) was investigated under transient conditions, because generally the combustion noise is higher during acceleration than at steady state as known from experience. The work carried out included basic investigations on transient conditions, variation of important parameters such as initial load, acceleration time, temperature of coolant, temperature of intake air, static injection timing and cetane number, and finally tests of some counteracting measures such as exhaust gas recirculation and pilot injection. According to their effects the parameters investigated are classified and their basic correlation with combustion noise is described.