Louvre Sizing for air inlet to diesel engine sound enclosure 1

[charlieng]

Hi,
I am designing a sound enclosure for a drill rig engine. The engine is a cummins 5.5L of about 180 hp. The engine runs a compressor and hydraulic pumps for rig hydraulic system. There is an integrated cooler pack at the front of the sound enclosure which cools engine coolant, compressor fluid and hydraulic oil. The cooler pack fan sucks air across the engine and blows in through the cooler pack. The air from the coolerpack is diverted upwards in a plenum chamber after emerging from cooler pack. The cooler pack size, fan size has already been designed and sized by cooler pack manufacturer.

I am putting baffles in panels to the rear and front of the engine for air flow into the enclosure. These baffles change the direction of air inflow so as to attenuate sound coming from engine. I am trying to determine the area of the cutouts for the baffles. Has anyone any suggestions on going about sizing the cutouts.

I was thinking of sizing total cutout area slightly larger than fan swept area.

Any suggestions would be much appreciated.
Thanks,
Charlie

 

[charlieng]

Hi,
Here is a better sketch of the enclosure.

Charlie

 

[waross]

My rule of thumb for air entry into generator rooms has been twice the area of the radiator. I have never had a problem. Sometimes the customer overrides my recommendation and I get less area. Fortunately those few installations have run at less than rated capacity.
As to fan swept area, I suggest using radiator area. The ducting on many radiator fans makes this a more realistic value.
Remember, if you make it too large by mistake no-one will ever know.
If you make it too small by mistake everyone will know and it may get expensive to change.
Not much engineering in this reply but quite a bit of field experience.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[NomLaser]

You will need to know the fan CFM, a desired air speed through your baffles and the free area of the baffles.

 

[Bribyk]

Figure out how much air is coming into and out of the enclosure and then size your louvers based on allowable pressure drop (don't forget about the air being ingested by the engine if you're drawing it from inside - about 2.5 cfm per horsepower). You could use manufactured louvers or just get the manufacturer's data for these louvers an reverse engineer your own. Engineeringtoolbox.com has flow loss coefficients for expanded mesh, if that's what you're using on your openings (don't forget to include it in your calcs, the losses are shocking).

0.5 inWC maximum vacuum inside the enclosure is a typical design value, aim for less. Make your outlet louvers bigger than the inlets to compensate for the air heating up and expanding on its way through. If you can get your hands on Caterpillar's Oil and Gas Application and Installation Guides (there's one dedicated to engine room ventilation) you will find it very useful for your project (ask your local Cat rep/dealer they may give it to you).

Don't forget that people are going to have to work in this room and that the engine shouldn't be drawing in air hotter than 38-40 degC (typical). Local temps more than 50 degC is not recommended as it is damaging to generator couplings and crankshaft dampers.

You're going to have to do an in-depth analysis on this including heat and airflow balances if you want a quality design. If not, you're asking for issues.

 

[plasgears]

Do not neglect to add absorption material in the plenum.