Author Topic: engine exhaust and acoustic enclosure  (Read 5413 times)

gmahendru

  • Guest
engine exhaust and acoustic enclosure
« on: March 02, 2006, 07:22:11 AM »
Hi all,

I am working on one project which is assembly of engine and alternator. The assembly is acoustically enclosed by an acoustic enclosure.

For engine exhaust gas, there is silencer.

My question is, if the exhaust gas silencer is separated atleast 10 meters away from the genset and is separated by a fixed boundary. After doing this will exhaust noise and engine-alternator noise interfere with each other??? ??? ???

I hope I made you understand my point.

Help required

Thanks.

johnbergstromslc

  • Guest
Re: engine exhaust and acoustic enclosure
« Reply #1 on: March 04, 2006, 12:54:26 AM »
Well, since the speed of sound at 72 F is about 345 meters per second and the separating distance is 10 meters, theoretically, wave cancellation could occur at 345/10 = 34.5 Hz, and multiples thereof (69 Hz, 103.5 Hz, etc..)  But active noise cancellation only works well for low frequencies, where the sound is omnidirectional, so you can count out anything over 150 Hz.  If you want to go to the trouble and expense of measuring and plotting the noise curve, you might see some attenuation at those narrow frequencies.  But as for all the others, nada.

So, in answer to your question, nope, it's not gonna work.

Gautam Mahendru

  • Guest
Re: engine exhaust and acoustic enclosure
« Reply #2 on: March 06, 2006, 05:31:21 AM »
Thanks Sir for ur reply.

But in actual case, the enclosed DG will be mounted on ship deck and exhaust of same will be taken out of that compartment through ship ducting. Silencers will be mounted one deck over it and is totally enclosed space.

Now in this scenario, with physical boundaries(steel) in between the two, the chances of interference is less, I think.


When i am testing the system in my shop, the problem of separating the two boundaries is very very difficult and expensive. how to convince the customer about the same???

regards

Gautam

johnbergstromslc

  • Guest
Re: engine exhaust and acoustic enclosure
« Reply #3 on: March 06, 2006, 06:38:29 AM »
Guess I really didn't understand what you were trying to say (and still don't).

Gautam Mahendru

  • Guest
Re: engine exhaust and acoustic enclosure
« Reply #4 on: March 06, 2006, 08:42:26 AM »
I am sorry for that.

I will try to explain things in detail...


I am working on one naval project. Its a 1000kWe Diesel Generator. Engine and Alternator coupled on a Baseframe and to reduce noise, Acoustic Enclosure is there...

This whole package is installed in naval ship... on below deck which is known as DG room. Exhaust of this DG goes to upper deck by ship deck. Silencer is mounted on the upper deck to silence exhaust gases before throwing them to atmosphere.

My question is these two noises will be separated by boundary (steel structure).... will they interfere with each other???

regards

Gautam

johnbergstromslc

  • Guest
Re: engine exhaust and acoustic enclosure
« Reply #5 on: March 07, 2006, 04:39:39 AM »
I guess I still don't know what you mean by "interfere".  Obviously, you're trying to get the thing as quiet as possible and if the acoustic enclosure and exhaust silencer were designed correctly, you shouldn't have any problems.  If you're asking whether the steel could resonate and transmit sound, yes, absolutely.  But the baseframe (inertial rafting?), acoustic enclosure and silencer should all be isolated from the steel frame by springs, rubber mounts, etc.. if the system is to work as it should.
Make sure everything is installed properly and fire it up.  See what happens.  If it doesn't work, hire an engineer who specializes in acoustics and vibration to determine the source of noise.  It sounds like your (potential) problem goes way beyond this forum.  Most people here just want to quiet their homes, a comparatively straightforward procedure.

 

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