Calculating Airflow Decrease of Backward Inclined Centrifugal Fan

[Carl Gearhart]

I'm trying to calculate the air flow decrease of a backward inclined centrifugal fan with inlet bell house with expanded metal installed. The air flow of the fan is 18,400 cfm, 2.6 total static pressure drop, 1540 RPM, 100 deg. air.
Orig. equipment did not have this expanded metal on the inlet but my site wants to install to keep out foreign material.
The % open area of the expanded metal is 79%.
The outer perimeter of the bell house is 26" and reduces to 17.9" dia.
I need to find out the static pressure increase and reduction in CFM.
Any help will be appreciated.
Thank you
Carl

 

[russ_watters]

Is the "expanded metal" a pre-engineered product, designed for the purpose? If not, it will be very difficult to figure out the airflow properties unless you can equate it to a pre-engineered product with known characteristics.

 

[Carl Gearhart]

The expanded metal being installed is a pre-engineered project, it's shaped like a diamond. It's going to be cut into a circle to fit on the inner part of the fan inlet. I'm thinking that there will be an increase in static pressure but not sure how much. The standard information that is available from the vendor of the expanded metal is that it has a % opening of 79. Hope this helps. Thank you

 

[Andy SV]

If you dome the screen or bow it then there will be little restriction
But somehow add more surface in the 3rd dimension to compensate for the restriction
A minimum of 21% more
The inner part of the inlet is the worst possible place
By the way what is the size of the inlet