Optimization of Combustion Noise of Modern Diesel Engines for Passenger Cars 2007-01-2379

For a considerable time now, the reduction of noise and vibration is one of the priorities of Renault for its Diesel engines. For example, the target for the latest 2.0 L Diesel engine was to be in the top class category in terms of the noise and vibration. In order to reach this target, combustion noise has been improved at each stage of engine development process, and special methodologies have been developed either for combustion noise characterization or for combustion noise optimization. This paper describes some of the methodologies developed in Renault and illustrates some examples of results obtained.

For measuring combustion noise in chambers, the combustion Noisemeter has been improved by introducing realistic engine structure attenuation. By comparison with other standard tools, it has been shown that the improved Noisemeter gives the best results with respect to the engine radiating noise, as well as to the subjective perception. Indeed, this improved Noisemeter gives more accurate results in the high frequency range.

For measuring combustion noise radiated by engines, a new source separation method has been developed using advanced signal processing tools based on synchronous Wiener filter. This method requires less instrumentation and shorter measurement time compared to other existing solutions, whilst also yielding high quality results for Diesel engines. It also enables fast and reliable results to be obtained for engine structure attenuation of combustion noise. Consequently, any tentative solution for improving engine structure attenuation can be tested and its effects quantified quickly. Moreover, engine structure attenuation is optimized during the early stages of engine development by FE calculation, thus making it possible to choose the best engine structure design such as cylinder block, ladder frame and oil pan.