Abstract
The present article is concerned with the investigation of the combustion noise of passenger car diesel engines, which, especially in part load conditions, is clearly perceptible for passengers and passers-by. On the one hand, the state-of-the-art is shown by comparing three actual passenger cars on an acoustic roller test bench. On the other hand, a profound analysis of the combustion process is performed on an engine test bed, with the main focus on the illustration of dependencies between several operation parameters and the combustion noise as well as the transmission from the combustion chamber to the environment. Beside steady-state operating points the transient behavior is also investigated.
Highlights
Driven by the increasing demand of customers for comfort, the subject of automotive and engine acoustics is rising in its importance in the process of vehicle development
A profound analysis of the combustion process is performed on an engine test bed, with the main focus on the illustration of dependencies between several operation parameters and the combustion noise as well as the transmission from the combustion chamber to the environment
The focus of the carried out engine test bench measurements was put on a profound variation of various engine parameters to develop the influences on the combustion noise behavior
Summary
Driven by the increasing demand of customers for comfort, the subject of automotive and engine acoustics is rising in its importance in the process of vehicle development. A well-targeted improvement of the sound characteristics has replaced a simple reduction of the noise level. In case of directly injected diesel engines, the excitation generated by the combustion process affects the overall noise level notably. In view of the combustion noise, the SI-engine can be seen as reference based on its smooth cylinder pressure curve. In the acoustically relevant part-load range, actual diesel engines show notable peaks in the noise characteristics, which are often sensed as ‘‘diesel knock’’. The target of the investigation is the optimization of the typical combustion noise of diesel engines by performing a profound and systematic analysis to show up coherencies and release mechanisms and to develop corrective actions and possible improvements
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