Propeller Efficiency: Ducted Propellers

[dtoshni]

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

[Guest625101138]

With JavaProp:
http://colaco.freeshell.org/mhepperl.../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,

[dtoshni]

Thanks a lot Rick.

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

[Guest625101138]

Originally Posted by dtoshni

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/conten..._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.

[dtoshni]

Thank you Rick.