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Engine Silencers

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Click here to use the engine silencer sizing program.

Information On Engine Silencers

All internal combustion engines produce noise, some more or less than the others. The intensity and magnitude of the noise will vary greatly depending upon engine type i.e. naturally aspirated or turbocharged, horse power developed, means of scavanging, type of fuel used, number of cycles whether 2 cycle or 4 cycle engine etc.

Among the pre-dominant sources that makes up the engine noise are the engine intake and exhaust.

For the purpose of noise control on engines, it is common practise to use silencers at intake and exhaust for treating the airborne noise. We have detailed various models of silencers in this catalogue that will cover most silencing requirements.

In cases where standard construction silencers do not meet the particular application, the special silencers can be designed to suit specific requirements.

In silencing internal combustion engines, the most widely used silencers are the reactive type, or chamber construction silencers. This type is largely dependent on area change to reflect sound energy back to the source and utilizes the attenuation properties of expansion chambers and perforated tubes.

The GE SERIES MULTI CHAMBER silencers covered herein are suitable for almost all the type of engines and operating conditions and provides maximum noise attenuation within the specified pressure drop limitations. Most of the naturally aspirated and turbocharged engines are best silenced with these silencers.

The GER SERIES STRAIGHT THRU CHAMBER RESONATOR type silencers are also described herein which are most suitable for very low exhaust system backpressure requirements. Many two cycle turbocharged and some naturally aspirated engines which requires very low back pressure for maximum engine performance will need this type of silencers. These are straight thru reactive type silencers in which exhaust gas flows through a ported tube and resonator which provides adequate silencing without imposing much restriction on the gas flow.

While the standard construction silencers are shown here, we specialize in custom designs for meeting specific requirements. Various nozzle orientations, dual inlets / outlets, different material requirements and special silencers with insulated shell with high heat absorptive packing are available to reduce radiated noise and also serves the purpose of heat blanket.

The silencers described here will cover most applications such as diesel generator sets, stationary natural gas and diesel engines, engine driven packages, stationary industrial engines etc.

Selection Of Silencer Type And Size

The proper selection and sizing of the silencer is of utmost importance to ensure that pressure drop, acoustical performance and other specific design criteria are met.

The selection of the correct type of engine intake and exhaust silencer is determined by the type of engine, the end use of the engine and the degree of silencing required. Also, the silencer size selected must accommodate the specified volume of exhaust gas flow keeping the back pressure within the limits specified by the engine manufacturer.

Generally, engine silencers are broadly classified into following categories depending on the end use.

Commercial Grade — GE1 Series

Industrial Grade — GE2 Series

Semi Residential Grade — GE3 Series

Residential Grade — GE4 Series

Critical Grade — GE5 Series

Super Critical or Hospital Grade — GE6 Series

The attenuation curves shown for each model indicates the insertion loss in dB at different frequencies. These curves represents the expected dynamic insertion loss at each frequency using the respective silencer. The resultant silenced noise levels may vary to some extent as many factors influence the silenced noise which includes the engine size, type, speed, unsilenced noise levels and frequency distribution. These curves represents the insertion loss for airborne noise only and has no bearing on structure borne mechanical noise or pipe radiated noise. Therefore these curves can be used as a guide line only for evaluating the total system performance.

For sizing the silencer, the important factor to be considered is the volume of exhaust flow. The open flow area within the silencer must be large enough to accommodate the exhaust flow without exceeding the engine manufacturerÕs allowable backpressure. If the silencer is much too large, then the exhaust noise simply passes through using only the initial large expansion for attenuation. On the other hand, insufficient size of silencer may cause loss of power and possible damage to the engine.

The correct silencer size can be determined using following formula:

Data Required:

  • Engine exhaust flow (CFM)
  • Exhaust temperature (°F)
  • Maximum allowable backpressure (inches of water)

Note: Do not exceed 13000 FPM velocity for sizing the silencer irrespective of the allowable backpressure. After calculating the velocity, decide flow area required as follows:


Flow Area Chart

After choosing the silencer size (Table 2) which has flow area equal to or greater than that calculated, the actual backpressure can be calculated as follows:

Silencer Chart
 
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