Analysis and control of noise emissions of a small single cylinder D.I. Diesel engine.

Comfort requirements, government regulations as well as consumer action groups are pressing the automotive industry to produce less noisy vehicles than in the past. These circumstances become more and more important for off-road and human operating machines forcing engine developers to investigate new and more effective control strategies of noise emissions. This paper concerns with the experimental vibro-acoustic analysis of a small (224 cc) single-cylinder direct-injection diesel engine used for agricultural and industrial applications as well as off road small vehicles. In order to evaluate the engine acoustic behaviour, experimental identification and localization of noise sources were performed at different speed and load engine conditions by several investigating tools. Within them, the intensity technique was chosen because of its peculiarities to be performed "in situ" without a specific anechoic test environment. Vibration measurements were also performed by accelerometer sensors. It is an alternative investigating tools for both source location and global sound power determination. To improve the spatial matching with the acoustical data and for better data interpolation, during these tests a 55-measurement points grid was used. A good correlation of data was determined and very useful information about noise sources location and relative transmission path were defined.