Expert: Paul Soderman - 6/8/2011

Question
Hi, im not an aerodynamic expert. but i want to design a squirrel-cage type blower wheel but i dont know what aspects do i have to take in consideration to make my design more efficient. I have notice some differences between my design and another design that performe better, like the material, the weight, the orientation of the blades and the perforated central plate. i want to know which other aspects do i have to take in account to make my design better and more efficient, and how to get the best performance. (sorry for my english, i have blocked the "Check Spelling" button)

Answer
Damian - To design a fan or blower for an application we first have to estimate the system performance curve of pressure head versus mass flow rate.  In other words, we need to know what pressure and flow rate the fan needs to deliver.  Then we can choose or design a blower.  If it is done correctly, the blower will not be near stall nor will it be pumping near the extreme end of high mass flow, low head.  It will be in the relatively flat part of the blower performance curve. It will not be too large nor too small.  The details of the blade shape and flow path are beyond what can be done in this forum.  Choosing a design similar to an existing geometry would be a good place to start.  You can find examples of squirrel-cage type blowers and performance data sheets on line.
Paul