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cesarvi03@yahoo.com
science forum beginner
Joined: 15 Apr 2006
Posts: 1
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 Posted: Sat Apr 15, 2006 4:33 pm Post subject:
Generator Set
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Dear Forum Members,
A member of this group have addressed me to your forum in order to get
some technical help.
I work for a small engineering company in Ecuador, South America and a
client has requested help to reduce noise levels coming from a
generator set.
Client has a 500 KVA caterpillar generator set and in a first approach
to reduce noise levels his company built an "acoustic booth" to
enclosure the generator. The problem they have now is that the alarms
go off because the unit is overheating, probably because of air
restriction.
My question is, could I install extra fans into the booth (there is
space downstream the radiator fan, in order to reduce the flow
restriction the generator set is having? What about if the fans I do
intend to install draw more air than that the radiator is supposed to
move?
Second part: to make things worst the generator set and its booth is
located in a small room with a louvered wall on one side. Air leaving
the radiator is exhausted into another room and from here up to top
where a louvered ceiling has been installed.
I do really need from your expertise on this field. What would you do?
Do you have any other idea?
Kind Regards,
Cesar Villavicencio |
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Angelo Campanella
science forum Guru Wannabe
Joined: 08 May 2005
Posts: 226
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| Posted: Sat Apr 15, 2006 5:34 pm Post subject:
Re: Generator Set
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cesarvi03@yahoo.com wrote:
| Quote: | Client has a 500 KVA caterpillar generator set and in a first approach
to reduce noise levels his company built an "acoustic booth" to
enclosure the generator.
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That's he basic way this has to be done. Sometimes it is sufficient to
only use a perimeter wall open to the sky, but that's for when only a
small reduction of noise is sufficient.
| Quote: | The problem they have now is that the alarms
go off because the unit is overheating, probably because of air
restriction.
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Just use common sense in designing the cooling system.
| Quote: | My question is, could I install extra fans into the booth (there is
space downstream the radiator fan, in order to reduce the flow
restriction the generator set is having? What about if the fans I do
intend to install draw more air than that the radiator is supposed to
move?
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It is common to have sound attenuator installed across the face of a
large opening for inlet and exhaust cooling air. Those fans can provide
only about one inch of water static pressure to move the air through all
attenuators.
This is described on this page in general. Vibro-Acoustics Co. supplies
attenuators that my work. There are many sizes and models to consider,
depending on the frequency range of gratest noise annoyance, the volume
of air flow and the static pressure available from the Caterpillar fans.
This is a genral list of methods:
http://info@vibro-acoustics.com/HVACNoiseControl/Silencers/VASilencingProblemsAndSolutions/18CommonSilencingProblems.htm
And a more pertinent solution; and arangement and design (if you have
plenty of money and time to do it right):
http://vibro-acoustics.com/HVACNoiseControl/Silencers/VASilencingProblemsAndSolutions/pr14main.htm
| Quote: | Second part: to make things worst the generator set and its booth is
located in a small room with a louvered wall on one side. Air leaving
the radiator is exhausted into another room and from here up to top
where a louvered ceiling has been installed.
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That should basically work, depending on how large a plenum you can
make, and the space vailble for a second (dishcarge) plenum.
| Quote: | I do really need from your expertise on this field. What would you do?
Do you have any other idea?
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It is helpful to know the sound level (octave band spectrum from 31Hz
to 4 kHz) of the sound that has arrived at the neighbor.
Apart from that, the method you describe is a "plenum". This is
basically a room whose walls will stop the sound from escaping to the
outdoors, while the inside surfaces of those walls and ceiling are
covered with sound absorbing material. The air must then proceed to a
second chabler wwhich contans the louvers to discahrge the air and
remaining sound to the outdoors. It usually works to vrying degrees.
If you have no acoustical equipment, then you have to try various
arrangements until both the neighbor complaints and the the equipment
overheats stop.
Angelo Campanella |
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Brian Marston
science forum beginner
Joined: 13 May 2005
Posts: 25
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| Posted: Sun Apr 16, 2006 1:14 am Post subject:
Re: Generator Set
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cesarvi03@yahoo.com wrote:
| Quote: | Dear Forum Members,
A member of this group have addressed me to your forum in order to get
some technical help.
I work for a small engineering company in Ecuador, South America and a
client has requested help to reduce noise levels coming from a
generator set.
|
Five noise sources - air intake, exhaust, radiator noise, fan noise &
casing noise emission. The air intake and exhaust are obvious and easily
addressed. The fan and radiator noise appear easy to address until you
realize what they are there for.
The radiator is to get rid of the internal heat of the engine. If the
generator set is open to the air, the casing heat from the generator and
the casing heat from the engine are lost from the outside of the
generator and the engine by convection and radiation. The fan on the
radiator is only dealing with the air flow to remove the heat from the
engine cooling system. The exhaust will carry away the heat of the
exhaust gases but the exhaust pipe radiates heat as well.
You should contact caterpillar and find out what is the casing heat-load
for the 500 KVA unit. The air flow should be such that the air flow
around the the outside of the generator set increases by no more than 10
degrees above ambient temperature. The generator is designed so that the
casing of the generator radiates enough heat (when unenclosed) that
the windings do not exceed 70 degrees above ambient. Any higher and the
insulation starts to break down, shorting out the generator. You need to
find out the heat load (radiator + casing), calculate the minimum air
flows and provide them OR else you will "cook" the electrics.
| Quote: | Client has a 500 KVA caterpillar generator set and in a first approach
to reduce noise levels his company built an "acoustic booth" to
enclosure the generator. The problem they have now is that the alarms
go off because the unit is overheating, probably because of air
restriction.
|
Hopefully the "acoustic booth" is adequately acoustically lined. and the
noise reduction compensates for the noise of the generator set, plus
internal reverberation within the "acoustic booth" (take your standard
calculations and add 10dB for the close fit of the "acoustic booth".
And be very wary of oil vapour. Unless the lining of the "acoustic
booth" is well sealed the acoustic lining will act like a sponge to any
oil vapour and you will end up with an oil soaked fire hazard.
The "open area" of the cooling air inlet area and the cooling air inlet
area should be 1 to 1.5 times the area of the radiator as a first
approximation, otherwise the restriction will push you to higher fan
speeds. The enclosure will need to be partitioned at the radiator to
stop recirculation of hot air. You need the fan curves for the radiator
fan and the static pressure drops for the radiator, the intakes louvres
and the exhaust louvres.
| Quote: |
My question is, could I install extra fans into the booth (there is
space downstream the radiator fan, in order to reduce the flow
restriction the generator set is having? What about if the fans I do
intend to install draw more air than that the radiator is supposed to
move?
|
Radiator noise regeneration is the least of your worries.
| Quote: |
Second part: to make things worst the generator set and its booth is
located in a small room with a louvered wall on one side. Air leaving
the radiator is exhausted into another room and from here up to top
where a louvered ceiling has been installed.
|
This begs the question: why the "acoustic booth", when it might be
simpler to convert the room into a fully lined "plant room" with a fan
forced ducted, cooling air intake, acoustic louvered wall to let the
cooling air out and fully (thermally wrapped) muffler and engine exhaust
pipe ?
You need a mechanical/acoustical engineer to assess the situation and to
design this properly. If you can provide reasonably good engineering
drawings of the layout and noise requirements, the design could be done
remotely. The 1/3 octave band noise levels / sound power levels of the
500 KVA Caterpillar generator sets are readily available from Caterpillar.
| Quote: | I do really need from your expertise on this field. What would you do?
Do you have any other idea?
Kind Regards,
Cesar Villavicencio
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