A REVIEW OF BASIC DESIGN PRINCIPLES FOR LOW-NOISE DIESEL ENGINES

In accordance with the main efforts of research and development in noise control of diesel engines measures which are essential for a noise reduction of more than 10 dB(A) and results achieved with an advanced direct injection combustion system are described. In general the noise of external engine parts can be reduced to a large extent only by vibration isolation or sound reducing shells. Considering economic aspects the attenuation of the total engine noise by more than 10 dB(A) requires a complete encapsulation of the engine which can with newly designed engines at least be partly integrated into the engine structure. Outgoing from some fundamentals about sound reducing shells the different approaches for low noise engines based on these principles and developed in the last decade are discussed. Specific measures applied with the advanced D.I. combustion system are discussed resulting, in comparison with optimized I.D.I. combustion systems, in equivalent exhaust emission, acceptable combustion noise and, regarding small diesel engines, in the same power output and speed maintaining the big advantage in fuel consumption.