Propeller Efficiency: Ducted Propellers

Hey there!

Can you please help me out. I need to find out how to calculate the efficiency of a ducted propeller for the light weight vehicle I'm building. If you can please post a method of hoe to do this, it'd be great. And also I seem to have lost my PNA. I think it has a section regarding this. If someone can please post the images of the section, I'd be really grateful to the person.

Thanks.

Daniel T

 

With JavaProp:
http://colaco.freeshell.org/mhepperle/javaprop/jp_applet.htm
you simply tick the "shrouded rotor" tick box on the design page. I have attached an example showing shrouded and unshrouded.

A shrouded prop reduces the losses to induced drag. If you have a heavily loaded prop with low aspects blades then shrouding makes a difference. As the blade aspect increases and loading is reduced the advantage of shrouding is reduced.

Rick W,

 

Thanks a lot Rick.

Can you please just help me out a little more. I need to know what the spinner dia. dsp. is?

 

This is normally the prop hub diameter. Spinners are fairing pieces that promote streamline flow over and behind the hub. With a boat there is rarely a nose spinner but often a tail cone:
http://www.propellerpages.com/content/nozzles/images/nozzle_prop_back.jpg
simply ensures streamline flow to reduce drag.

Attached image shows a small diameter faired hub with both nose cone and and tail cone. These reduce the prop losses and are assumed to be installed for using Javaprop.

Rick W.

 

Thank you Rick.