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EnginSoft - Conference Abstracts
EnginSoft International Conference 2009 |
Analysis of a scooter muffler internal geometry for the optimization of tailpipe noise soundquality at idle condition using modeFRONTIER coupled with 1D wave build 3D |
Ciacci Alessandro - Piaggio |
Abstract |
The optimization of the acoustic performances of the exhaust silencer of an internal combustion engine is a problem requiring the determination of the value of many parameters: the overall muffler volume, the subdivision of the internal volume in several chambers, the diameter and length of the transfer and primary piping. The traditional trial & error approach has many limitations: the time needed to explore a single configuration is quite long, since it includes the in-series usage of several software applications; moreover the search of the optimal solution is entrusted to the experience of the technician that modifies the values of each single parameter, on the basis of their individual influence, in order to reach the target. Obviously this kind of approach is not only time- and effort-consuming, but it does not guarantees that the real optimal solution will be actually found. The use of modeFRONTIER allows to automate the search process of the optimal solution, with a remarkable time saving, permitting to reach the fixed targets, thanks to the multi-objective and multi-parametric optimization algorithms. The starting point of this work has been the experimentally validated base model of an existing muffler. An objective curve, based on subjective jury panel analyses, has been superimposed on the acoustic transfer function FRF (frequency response function). The model has been optimized by modeFRONTIER, which has iteratively modified the available parameters, to drive its response towards the target. A physical prototype has been consequently realized, based on the optimal configuration generated by this study, and bench measurements have been performed to verify its compliance with the requirements. As a final verification, the prototype has been tested on the vehicle, providing evidence of the improvement of the sound quality, with reference to the initial solution. The described acoustic optimization procedure will undergo further future developments. In particular it will be possible to evaluate the acoustic performances using the engine source instead of the white noise source and to develop an optimization procedure able to evaluate at the same time the acoustic and performance outputs, in order to determine the best trade-off. |
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