[didane]

Hi dear all,

i'm working on VAWT and i managed to get torque values for every RPM. however, the problem is the torque value increases whenever the RPM increased which is not quiet true. Could anybody help me out on this...Thanks in advance

[kaya]

Originally Posted by didane

Hi dear all,

i'm working on VAWT and i managed to get torque values for every RPM. however, the problem is the torque value increases whenever the RPM increased which is not quiet true. Could anybody help me out on this...Thanks in advance

torque is Nm, for a constant wind speed its a function of lift to drag ratio. When you increase the rotational speed what you change is the angle of attack, if your torque jumps up with higher rpms for the same wind speed I'd check angle of attack values that maybe you were operating in a stall region.

[didane]

Thanks Kaya for your reply.
But the thing is i want to obtain the power curve for this wind turbine at only one angle of attack...so, is there any other way to get this done without changing the angle of attack as in the link attached below.

[kaya]

link is not visible.

I don't think I understand you. Power curve is watt vs. wind speed and with increased wind speed often rpm increases depending on the controller setting which allows you to work in some angle of attack range. what do you mean by constant angle of attack?

honestly I have never worked with a VAWT but I find it very useful to look at local angle of attack values to understand what is actually going on over the blade section if you have doubts about the forces.

what are you using? are you resolving the whole geometry or running a blade element method?

[didane]

I am resolving the whole geometry of the turbine and i know the optimum angle of attack of this turbine. Thus i want to get the power curve at this optimum angle of attack. In order to come out with the power curve, u need to use various rotational speed and observe the performance of the turbine. From there u can decide the best tip speed ratio (TSR) of this turbine, which will allow u to choose the right generator for this wind turbine...Thanks anyway

[kaya]

i think you should open up some text books. optimum aoa is a term you d use for a blade section. and its TSR, azimuthal position, incoming velocity defines aoa values for blade sections. when you change TSR, you re actually playing with the velocity triangle

[didane]

I sure would consider your comments..Thanks