Application of Novel Micro-Grooved Elements to Small Engine Silencer 2013-32-9001
Micro-grooved elements (MGEs) represent a novel technology developed for noise control in automotive, aerospace and room acoustics.
The key concept of the MGEs is based on the use of micro-grooved layers forming micro-paths where the energy dissipation of the acoustic waves is primarily originated by viscous friction.
Composed of a multi-layer fiber-less material, the MGEs represent a potential alternative to the traditional fibrous material based solutions as well as to the increasingly popular micro-perforated elements (MPEs). MGEs are designed as cost effective elements, found to be suitable for substitution of fibrous materials, typically present in silencer units.
In this paper, a design procedure for a fiber-less small engine silencer based on MGEs is presented and experimentally validated.
Hereby, the acoustical performance of the MGEs has been modeled by adapting the theoretical models provided by Allard and Maa for rectangular and circular ducts. The simulated impedance and absorption coefficient of a MGE have been compared to the experimentally determined data by following the classical two-port approach.
The absorption coefficients of micro-grooved sample and micro-perforated element have also been analyzed in comparison.
As the first practical noise control implementation of the MGEs the novel acoustic panels have been utilized in a Formula SAE racecar silencer. In this silencer the MGEs are designed to acoustically behave as locally reacting surfaces.
The use of the MGEs is believed to provide the reduction in soot contamination that typically occurs in silencers with micro-perforated internal ducts.
This paper also provides an overview of several silencer configurations equipped with MGEs, tested, together with the results in terms of transmission loss (TL), absorption and reflection coefficients.