Propeller design software (for ROV thruster)

I am designing a low cost thruster for ROV's to be used in secondary and university courses. Being an electrical designer, I have limited hydrodynamics skills (about all I know is "water is wet" ) I do however have extensive 3D modeling skills using SolidWorks.

Is there a software package that I can use to match the RPM/torque curves of the thruster that will help design (or indeed select) the best propeller for the job?

Is there a "propeller 101" book that an engineer can use to come up to speed on propeller characteristics and uses?

Thanks in advance for your guidance, even if it is an admonishment to "RTFM" as long as you direct me to the relevant "FM".

David W.

[Guest625101138]

The propeller part of it is quite easy using JavaProp. It does all the hard work. It has a limited selection of foils and the default settings are for air prop but these are easily set to water parameters in the Options page.

Google JavaProp and run the applet. If you get to this point and get confounded then just post questions here. The real value of JavaProp is that it is an analytical approach so covers a very wide spectrum of use. It is based on the fundamental physics not some measured set of parameters. There is also a lot of information on prop design on the web site but you do not need to take all this in to use the tool to get good results.

The hard part is likely to be determining the drag on the ROV?? My brain is not all that clear at the moment but the TLA eludes me. In any event it is impossible to design a prop correctly unless you know what thrust it requires and this is simply the opposite of the drag on the ROV hull.


Rick W

[dk-info]

Originally Posted by Rick Willoughby

Google JavaProp and run the applet. If you get to this point and get confounded then just post questions here. The real value of JavaProp is that it is an analytical approach so covers a very wide spectrum of use. It is based on the fundamental physics not some measured set of parameters.Rick W

OK, JavaProp is very cool for creating a prop according to the design parameters. I do have a few questions:

1. What rule of thumb can I use for the "Power" setting? I have a standard 540 size RC motor, connected to a speed reducer.
2. How do I characterize my motor-gearbox selection for this analysis? Stall Current? No-Load Current?
3. Once I have a design, what is the easiest way to import it into Solidworks? I have imported the curves generated but can't loft them into a solid, I tried 3D sketches with the same problem. Any SolidWorks jocks out there?
4. How do I set the chord at each station?
5. What are reasonable "airfoil" profiles for water?

A lot of questions, but consider this. I have access to a 3D printing machine that can render this design into a real ABS plastic prop. The machine time is being donated to this school project, so I need to make every prop count.

Thanks again for the excellent forum, I look forward to your ideas (and criticisms if constructive)
David W.

[jehardiman]

First, is the thruster to be bi-directional?

If it is, then Java prop will not work because it is designed for ahead direction only.

Second, is it in a tube?

If it is in a tube, then you should look at a Kaplan blade type. Most likely something with a blade area ratio of ~35-45% and a P/D =1.0.

As far as the motor is concerned, is it brushed or brushless? Power controler?A propeller will absorb all the power provided to it until it reaches the operating point. If you have a RPM torque curve for the motor and a desired speed, we could improve the wheel.

So for the questions..
1) Get the motor spec, it should have a stall torque and knowing the winding type will give a power curve.
2) The ROV will always speed up or slow down until the power absorbed by the wheel is indentically equal to the power required for the ROV at that condition. This is why you need to know motor power and vehicle drag before designing an optimum wheel. Any wheel will work, but it will not be optimum.
3) IMHO, Solidworks is for simple mechanical parts, not really for naval architecture. Get a copy of Rhino but you will still need to hand fair the root fillets.
4) That falls out of the blade loading analysis, which if you know your motor torque curve and if you use a tube, you can optimize cord distribution along the blade.
5) Depends if the unit is to be di-directional or ahead only.