POOR EFFICIENCY FAN

[Jinder]

I have an axial fan rig that has a new rotor and stator design. I have tested it and the efficiency of the new rotor is only about 30% max when it should be about 80%

My question is, what are the reasons for poor efficiency, why is the new rotor not very good? I t is run at 2000rpm.

Could some-one please also put me into the right direction to where I could learn some basics on Turbomachinery (only Axial fans) and Velocity Triangles and how these are used to look at the performance of a fan. All the neccessary detail around them. Good detail on pressure differences, and how this works etc.

Thanks

 

[Ralph2]

Is the fan mounted with the right rotation? Are the blades adjustable and need to be set to a specified angle? Is there shrouding that allows internal circulation?
Just a few thoughts ;-)
Ralph

 

[electricpete]

Good thoughts by Ralph. I don't know anything about velocity triangles, but I wouldn't think you have to sharpen your pencil with that tool to figure out that something is way out of whack.

I would think you need to check with the manufacturer to determine what are the conditions under which their efficiency is computed. Air temperature, axial alignment, upstream and downstream configuration, inlet vanes, speed, load, etc. And inspect your installation carefully.

Probably not much help. Just my two cents.

 

[electricpete]

... Also the 80% is likely the efficiency of the fan only. When you compute yours if you measured the motor input power or worse yet electronic drive input power, then you are including other losses beside the fan. I would ask the manufacturer for a test report and look closely at his test method to compare all paremeters and calculations to your method.

Also don't overlook the possibility of instrument error. You are presumably measuring flow and a small dp. Do you have a way to independently check those quantities?

 

[Ralph2]

Just how are you checking the "efficiency" of the rotor? The simplest is to measure the amperage draw of the electric motor. If it is not at the rated amperage then something is wrong with the fan and I would suspect that the vanes are not set to the correct angle. If the motor is drawing the rated amperage then perhaps you have a damper control problem.
Good luck
Ralph

 

[okanataman]

hi jinder
ý dont know whether you solved your problem but if you tell any information about your flow rate(m^3/s) and head (m) ý can tell something about your efficiency
And for reference check Karassik 's book it is pretty good.
good luck