What is an Exhaust Silencer (baffle, splitter, panel)? Whenever air or some gases like exhaust gas from the internal combustion engine in the industrial unit are emitted to the atmosphere under high pressure, they cause high sound/noise levels. An exhaust silencer is installed in the exhaust system to suppress the sound so as to safeguard the workforce in the industrial unit or public against noise pollution. It is basically used as a soundproofing device. The main disadvantage of an exhaust silencer is that it increases back pressure and this reduces the efficiency of the engine. How does a silencer work: Acoustic absorption refers to the process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy. In general, soft, pliable, or porous materials serve as good acoustic insulators - absorbing most sound, whereas dense, hard, impenetrable materials (such as metals) reflect most. Typical Industrial Silencer Makeup: Consists of outer metal (perforated) so the “holes” allow the sound waves in. Internally there are multiple layers of protection cloth, and acoustic fill materials.
Exhaust Silencer Design (refers to the overall design of the “acoustic attenuation” system) Horizontal & Vertical Exhaust Silencer Baffles (Splitters, Silencers, and Panels). An overall Exhaust Silencer design has many critical inputs in order to create a system that is thermally and acoustically adequate. We evaluate location, Exhaust Gas temperature, OEM Turbine Sound Power levels (sound omitted by GT), Velocity, pressure drop, site required attenuation (how much we should “dampen” the noise).
Location in Exhaust Typically the OEM determines the Exhaust Silencer position within the Exhaust System. Once this location is established, retrofit work is limited in flexibility for position. The location also can have an effect on the types of materials we use due to velocity or turbulent flow.
Sound Power Levels The sound power levels is the actual “sound” the Gas Turbine omits by Octave band or frequency. This sound is commonly measured on a scale from 31.5 Hz to 8000Hz.
Site required attenuation This is commonly referred “acoustical performance” of the Silencer system, or “how well they absorb sound”. This is generally measured in the near field and far field.
Size of Silencers Once the location is established, our Acoustic Engineers determine the quantity, length, and thickness of the Silencers. To achieve a certain level of attenuation, the Engineer will apply a certain amount of total square feet of attenuated surface. The Engineer takes into account velocity & pressure drop to optimize a silencer design for attenuation and economics.
Exhaust Panel Design (refers to the actual individual panel design) Once we have size, quantity, and GT inputs we select the proper materials to achieve the desired lifetime thermal cycles. As the Gas Turbine starts, the External “skin” or perforated material heats up from ambient conditions to 1000+F. The center of the Exhaust Panel is protected by thermal/acoustic insulation, so this process is slower. When the GT shuts off, the process reverses. As this thermal cycle completes, the Exhaust Silencer metals are thermally moving, stressing the materials, welds, and connections.
Exhaust Panel supports, guides and brackets. It is imperative that the Exhaust silencer remains in position but is designed to allow thermal growth during operation. These all act together to control predicted movement but provide stability.