Sizing of reactive silencers with non-perforated tubes is a subject that acousticians are far from having covered.

The approach for the prediction of acoustic and aerodynamic performance of reactive silencers, involving the consideration of various input data (e.g. thermodynamic parameters, noise reduction criteria, back pressure criteria, size of the soundproofing device), is computationally intensive, what is a serious obstacle for the design of tailor made solutions in a short period of time, as, howether, often needed in industrial contexts where soundproofing devices different from those in use for automotive applications are envisaged.

Therefore, the sizing of a reactive silencer able to control the exhaust noise emissions of a big industrial thermal engine’s (e.g. for a genset) is often performed by the selection (among a more or less wide standard range of products) of a unit already fully engineered (i.e. of which performance is known with certainty, and sufficient, even if not very close from the need of a given project), what prevents in general performance optimization, with sometimes unfavorable consequences in terms of pricing.

Indeed, each shape detail & each decimeter of all the components of a reactive silencer can influence its performance in a significant way and there is a need for simulations easy to be conducted to evaluate quickly one or several possible designs for a given project (for which the combination of all the parameters to be accounted simultaneously is rarely reproducible).

ITS has integrated the sizing of reactive silencers with non-perforated tubes to the acoustics calculation software SILDIS®.

Mountings for which simulations are possible are combinations of uniform tubes, extended tubes, side tubes, transverse tubes and variable tubes as frequently used for the construction of industrial reactive silencers.

Preconfigured mountings involving long expansion chambers & short expansion chambers as well have been integrated to cover usual configurations like in-line expansion chambers, expansion chambers with side inlet and/or with side outlet, and expansion chambers with overlapping tubes (with flow reversal), with one or more connecting tube(s) between expansion chambers (from 1 to 3 chambers).

Existence of a gas flow, source impedance and exhaust line end radiation are also considered, to get a comprehensive picture of a given situation for which one wishes to identify the best means to limit noise.

Calculation routines have been implemented to calculate for reactive silencers: total pressure loss, transmission loss, insertion loss with a substitution duct and noise reduction with an additional duct.

Following the operations of development of a new module (Module 1B) of the software SILDIS® (including the sizing of reactive silencers with non-perforated tubes), comparison of simulation results with bibliographic data (measurement results, results of calculation by others, ...) showed good agreement for many combinations of the parameters which are fundamentals to properly assess a situation in terms of exhaust noise abatement.

The expected consequence of the implementation in SILDIS® software of those new features is the ability to refine the performance prediction of specific equipment e.g. for the sizing of industrial (and marine) silencers for reciprocating internal combustion engines.