In recent years comfort has become an important factor when evaluating the performance of modern automobiles. One important aspect that has negative ramifications on the perception of the quality is the generated noise. Therefore, an important goal in current research activities is to minimize the acoustic noise that is radiated by a combustion engine. It is possible to improve the noise vibration harshness (NVH) behavior by using active or passive methods. One promising passive method is an encapsulation. The paper presents simulation approaches of a thermo-acoustic encapsulation of an engine block, which completely wraps the engine block. In general, thermoacoustic encapsulations are able to reduce the radiated sound significantly. Furthermore, they also increase the heat storage capacity and thus the efficiency of the engine. As a consequence the exhaust emission isreduced by avoiding so-called cold starts. To evaluate the influence of a thermo-acoustic encapsulated engine regarding the radiated noise appropriate finite element models are commonly employed. Additionally, it is necessary to consider the surrounding air and the air between the engine and the encapsulation. That is to say, a coupled structural-acoustic simulation has to be applied to obtain sufficiently accurate results. One has to take into consideration that fully coupled numerical simulation approaches are very time-consuming and computationally expensive. In early stages of the design process it is desirable to minimize the computational costs. The paper at hand presents first results in that regard. The numerical effort is significantly reduced by applying prediction based approaches known from civil engineering, such as the sound reduction index. The solutions of the prediction based approach are compared and evaluated with results obtained with a full scale finite element model of the encapsulated engine.
Thesound reduction index applied to automotive problems
2014
10 Seiten, Bilder, 9 Quellen
Aufsatz (Konferenz)
Englisch
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