Ducted Fan blades

[GatorGuy]

We are currently working on a ducted fan design and had a quick question. So far we are setting our sites on a 36 inch four bladed fan inside of a 40-50 duct. Our current question is, would it be any benefit to set a second fan inside the duct behind the first one? Or is this just a waste?

 

[btrueblood]

As with so much else in engineering, "that depends".

If one fan "does the job", why bother with the expense, weight, etc. of 2nd fan.

If 1st fan is running near stall, then you can unload it (move away from stall) by adding a 2nd stage. Usually, you would add a stator stage between the fans, to de-swirl the flow (or counter-rotate the 2nd fan).

 

[GatorGuy]

Thank you for your reply btrueblood. I have been running some rough calculations and I should be able to get away with one set of blades and a stator. I found a company that made a ducted fan with a single set of blades, a stator, and an afterburner. I am currently trying to contact them to see what kind of thrust they are getting from it. With our current aircraft design I would like to target a thrust range of around 400lbs. I have only been able to find calculators for propellers but it has given us a starting point. As far as the number of blades, does having a larger number of smaller blades have an advantage over say 3-4 larger blades?

 

[VTOLaeronautics]

GatorGuy, having more smaller blades is the same as a turbine engine, that type of engine has multiple sets of fans to create heat, haveing 4 or 5 larger blades will work a bit better on duct fans, plus it would cost less. tell me more on your duct fans because I am researching on different types of duct fans for my experamental project I am working on!


~VTOLaeronautics