Tools & technical notes

This document describes the operation of a venting silencer, explaining how noise is generated when a pressurized fluid is released. It details the different flow regimes (subsonic, sonic, supersonic), the types of noise produced (jet, mixing, shock), and the noise reduction mechanisms used in the silencer, including expansion shoring, sound spectrum shifting and acoustic energy dissipation.

This document details the operation of engine silencers, passive devices that reduce the noise of internal combustion engines. It explains two main mechanisms: reactive attenuation, based on the reflection and interference of sound waves, and dissipative attenuation, using absorbent materials to convert sound energy into heat.

Volumetric rotary compressors, such as Roots-type compressors, can generate high noise levels, reaching up to 135 dBA, and noise can propagate through various pathways. To reduce noise, it is essential to use inlet and discharge silencers, as well as to deal with airborne and solid-borne propagation by methods such as sound insulation, the use of anti-vibration devices and the installation of a hood.

Engine pollution control systems reduce emissions of pollutant gases, using technologies such as oxidation catalytic converters to treat carbon monoxide (CO) and hydrocarbons (HC). Particulate filters (DPF) capture and burn fine particles, while selective catalytic reduction (SCR) converts nitrogen oxides (NOx) into nitrogen, water and carbon dioxide.

This document presents an acoustic simulation study of spark arresters of various diameters (DN150 to DN400), with the aim of determining the acoustic performance of these elements as a function of their configuration. The method uses Ansys Acoustics software with finite element analysis. The results show similar attenuations for given diameters, with variations linked to configuration. Finally, intrinsic attenuations are retained for each configuration.