The marketing of exhaust silencers for diesel or gas engines has always been an activity of ITS, whether it comes to construction machinery, traction vehicles (e.g. for trains), boats or (most often) stationary engines (i.e. generator sets, cogeneration units) whose power is sometimes counted in MegaWatts.

In the context of each project, a careful selection (among standard catalogs dedicated to a wide range of applications) or careful sizing (tailor-made, with a calculation program such as the Module 1B of the SILDIS® software [1] or with finite element calculation software [2] - all these tools are at the disposal of the human resource of ITS -) of a noise attenuator must be carried out, taking into account all kinds of considerations, in particular on a technical plan :

  • acoustic data: noise spectrum to be attenuated, overall sound level (and sometimes also: per frequency band) before soundproofing and as to be obtained at the end of the exhaust noise reduction action (in terms of level sound pressure at one or more specified locations or in terms of sound power level) ; the attenuation of various elements of the aeraulic network e.g. straight lengths, elbows, flue pipe and the influence of directivity must sometimes be evaluated to determine the performance required for the silencer
  • thermodynamic and fluid mechanics input data: temperature, flow rate and density of gases, allowed total pressure loss
  • data related to the construction and the modalities of integration into the exhaust line: location of the equipment intended to reduce noise emissions according to the available space (e.g. separate, included in a chimney or even in a more complete set with a catalytic device), number, dimensions and orientation (in relation to the gas flow) of interfaces (with or without connection flanges, whatever the standard to be eventually considered) and supports, need for accessories (e.g. expansion bellows, elbows, valves, terminal vertical ducting, anti-pollution cartridges); the type of fuel (gas possibly: biogas, or diesel) and, where applicable, the temperature of the gases (e.g. downstream of a heat recovery unit) can lead to specific choices in terms of construction material (standard constructions in mild steel with temperature resistant paint being sometimes advantageously - with regard to durability - replaced by stainless steel - various grades are possible - or by other materials e.g. Corten)

Depending on the case, the design of an engine exhaust silencer may include :

  • one or more reactive stages, the sound attenuation (at low and medium frequencies) being based on the presence of chambers (not necessarily all delimited by the outer casing of the silencer) connected by tubes (perforated or not: all dimensions must be chosen on purpose), which causes for the acoustic waves reflection phenomena during their propagation in such ducts (the changes of section are also accompanied by a total pressure loss which must be evaluated in a sufficiently precise manner so as not to not harm engine performance)
  • a dissipative stage, the acoustic performance (in medium and high frequency) being due to the presence of sound-absorbing (porous) materials (e.g. based on mineral fibers or on ceramic fibers when allowed) with respect to which gas velocity and temperature have a significant influence on behavior (just like thickness, active length, surfacing and perforated protection e.g. at high frequencies); the pressure drop is not always negligible, especially in the event of obstacles to the direct passage of gases such as splitters (baflles) often concentric when it does not come to a central pod

Experience has shown that a silencer + chimney assembly is often an efficient and economical solution for limiting the sound levels of diesel or gas engines exhaust, since it allows sufficient space to be fitted out in an autonomous way by the acoustics expert (which the ITS participant is).

ITS has marketed an exhaust silencer for a diesel engine for an installation located in Eastern Europe.

There is no doubt that the quality of design and construction (coexisting with a competitive price, which is significant in the economic situation of mid-2021 impacted by the rise in the price of raw materials, including those used in the manufacture of silencer exhaust for diesel or gas engine) will delight the Customer, who will also benefit from the shortest delivery time (the scope of supply including transport).

[1] cf. https://www.its-acoustique.fr/en/acoustic-aeraulic-construction-cad-calculation-software.html

[2] cf. https://www.its-acoustique.fr/en/updates/acoustic-aerodynamic-finite-element-modeling-silencer.html

Preservation of acoustic environment

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