4 Quadrant propeller power curve

[kistinie]

Hi

A motor boat uses 2 opposite quadrants (vectors) on the prop:
Forward - Torque +
Reverse - Torque -

A sailing boat doing recovery uses up to 4 quadrant
Forward - Torque +
Reverse - Torque -
Forward - Torque +
Reverse - Torque -

Power curve i have seen where all 1 or 2 quadrant


I would like look at 4 quadrant propeller power curves to choose a propeller
Any idea to get theses curves ?

Develop them!

YOU are the Hybrid Corsair..........

[fcfc]

The post from Joakim energy recovery while sailing give you

forward torque + (motoring)
forward torque - (electrical generation).

If you want reverse too, your best bet is CFD like this : http://mh.mec.upt.ro/accord-fluid/wo...moraritei2.pdf

[baeckmo]

In pumping technology, all four quadrants are of interest and have been studied. If you search the net for "sutercurves", you may find info on high-specific speed machines (~propellers).

[jehardiman]

Actually, most ships props are tested in all 4 quadrants. This is why you will see warning plates at the throttle wheel such as "Do not exceed XXX astern RPM while moving ahead or XXX ahead RPM while moving astern".

As to what happens in the other quadrants, look at the normal Kt, Kq vs J curves. When J is negative (i.e. RPM ahead, Va astern), Kt, and Kq increase until stall occurs. At this point Kt drops precipitiously while Kq remains approximately constant. In this quadrant, blade bending stress is a concern. For the other quadrant (i.e. J positive, RPM ahead, Va ahead), if you continue to increase J beyond the point the Kt = 0 there will be a region where Kt is negative, but Kq is positive. In this region, when trailing a shaft, the prop is not developing enough torque to turn the shaft. If you continue to increase J, eventualy you get to a region where both Kt and Kq are negative. It is only in this region that you can extract power from a trailed shaft. The size of this region is dependent on blade shape and section, but generally, again you will reach a point where the blade stalls so negative Kt will decrease and negative Kq will max out. This of course is all for RPM ahead. There is a similar set of curves for RPM astern( I.e. J positive RPM astern Va astern; J negative RPM astern Va ahead), but generally you get much poorer performance from the wheel becase the blade is generally optimized for "ahead" operation (and again, depending on blade shape, bending stress may limit operation). It is possible to build a prop with symetric blade shape and sections (think a Kaplan thruster) but it will be poorer performing as both a propeller and generator.

Bit exhaustive, but nice! Thank you!

Our girlie will not get it anyway...........

[kistinie]

Most of the time, when i have asked about a prop efficient on 4 quadrant , i've been answered that it was not possible and a separate prop for regen was compulsory and info you give of course go in that way.

But on another hand, i have searched for 4Q power curve, a symmetric blade probably and found nothing for the moment so i think it is a little precipitated to clear this option of an efficient symmetrical 4Q prop
Can anybody find us a 4Q power curve of a symmetrical or near symmetrical prop in order to see the KW we get for what drag and prop efficiency cost...

Anyway, great contributions ! Thanks

[kistinie]

Sorry to pull up my question again.

Is it possible to find on earth a pic and power curve of a symmetrical or close to symmetrical prop that fits a rotating shaft ?

Could a symmetric prop could look like this ?
Source : http://www.rexresearch.com/boats/1boat.htm#spiral

[gonzo]

It could look like that. You could also install hexagonal wheels in your car.

Do´nt talk him into sensible solutions Gonzo! He likes it the hard way.

[kistinie]

Gonzo, Ape x , once again, your troll and look down on subjects you do not want to understand.
Never tired to spoil !

Does the owners of this site realize you bring all the forum quality down with your condescending behaviour ?

Hmm, ja sister.

Hybrid corsair, what is that? Pirate by profession, half ox, half girl?

We are the trolls ja..........

[kistinie]

These lines are for 4Q propeller.
I am not the subject of the study here.

If my case interest you that much, please create another "KISTINIE" subject in the bar section.

Many thanks

[Asleep Helmsman]

Originally Posted by gonzo

It could look like that. You could also install hexagonal wheels in your car.

I think you're giving it too much credit. More like square wheels if you asked me.

Remember the longer the legth to width ratio the more effecient. (Well mostly anyway.)

[kistinie]

Yes, mostly
In case of dual prop, no
In case of a symmetrical jet turbine or just a ducted prop with a stator, no


As long as your design prevents rotation of water, length is not a reduction factor

I Prefer triangle wheels, please.
Squared are less homogeneous and lead to frustration !

And when i see the reputation tool and the way it is used, i guess frustration is really meaning something here !

Triangle wheels, please
Green with an eye inside, an eagle, two 0, and an hidden RFID tag to burn in kitchen microwave :-)