UIUC data for propeller design

[Beth]

Hi Emilio,

You mentioned on the Tail-sitter UAV Tutorial video how UIUC data can be used to define the propeller design - I've tried this but struggled as my propellers aren't being written to OpenVSP.

Is defining their properties in the way below correct? (I appreciate it would be tidier to extract the data from an input file!) Or do I also need to run it through the propeller_design( ) script also?

Here I've used the data for the 11x7  thin electric APC propellor:

When defining this as well, I also noticed a propeller analysis can be run through the script:

SUAVE.Components.Energy.Converters.Rotor.spin(lift_rotor, conditions)

This appears to output Power/Thrust Coefficients etc. when a rotor geometry is inputted - do you have any advice on how to set up the 'conditions' input, as several parameters for this are needed

Really appreciate any help on this topic!

Thanks,

Beth

[Emilio]

Hi Beth,

Yeah, this is easy. I agree we should have an import script. We used to have one....

For copying and pasting in data, you're close. Instead do this:

lift_rotor.twist_distribution = np.array(41.81, 45.76,.... )]    * Units.degrees

Similarly the chord distribution and radius distribution will require it to be an np.array as well.

For conditions, you can use this method to setup everything for you. Basically it just takes a prop from a network and runs it at a point (altitude, airspeed, rpm). Don't spend time figuring out conditions, that's way too much work.

-Emilio

[Beth]

Hi Emilio,

Thanks so much for getting back to me, yep that method seems to work really well!

I gave the propeller_single_point script you suggested a try but the results I'm getting aren't really lining up with what the UIUC propeller database is suggesting.

For this I've tried modelling the Thin Electric APC 11x7 Propeller, and I'm pretty sure I've set everything up okay but the numbers aren't aligning at all (and for some reason I keep getting 0 for my thrust coefficient output). Are there any glaring errors in how I've set up this propeller that you think might have caused this?

Set up in Python:

Results: 

[First run was with specifying pitch units 'inches/revolution' and Second run is units 'inches'; I was unsure as to which is correct!]

Expected Solution for Omega=3003, J=0.173, 11x7 Propeller:

CT = 0.0948

CP = 0.0452

eta = 0.362

As you can see the outputs don't really match up! Was there anything I've forgotten to include in the setup?

Many thanks,

Beth 

[Emilio]

Hi Beth,

The thing that stands out to me is that the pitch is set to 7 inches. The number 7 is an RC thing that's not super useful. Set that to 0. In SUAVE pitch refers to this. The other thing that looks off is the number of blades, I know they make 4 bladed props, but most are 2.

Let us know how it goes.

-Emilio

[Beth]

Hi Emilio,

Thanks for the extra information on this, thats handy to know about pitch. 

Looking back I'm also not sure why I chose 4 blades, so thanks for the correction! (This seems to affect the numbers a lot!)

I've tried re-running this with the modifications but the numbers still look a little odd:

[[ Again expected are:

eta = 0.362

CT = 0.0948

CP = 0.0452 ]]

Here eta is looking more similar, but Cp is still quite different and Ct remains to be zero.

I'll look into what parameters SUAVE uses to calculate Ct as I may have missed something here, so I'll try report back on this. 

Thanks,

Beth

[Emilio]

I think it's the speed. J = V/nD where n is revolutions per second not rad/s.

The next thing to do would be to use the actual airfoils. We provide them with SUAVE in the regressions folders. Depending on the prop from APC it would probably be a Clark Y.

-Emilio

[Beth]

Thank you for the pointers, I'll give those adaptations a try and hopefully it starts looking a little better!

Beth