Difference between Estimated Torque and LSST in NREL Phase 6

Dear Members,

I have a doubt what is the difference between estimated torque and LSSTorque. Especially I noticed that at high wind speed there is a huge difference between the value.

My BEM results go well with estimated aerodynamic torque but lower than LSST. So the power also goes lower.

Can I compare Power calculated from estimated Aerodynamic Torque instead of LSST.

Regards
Ijaz Fazil

Dear Ijaz,

In the UAE Phase VI datasets, the low-speed shaft torque was both measured via a strain gage (LSSTQ) and estimated based on integration along the blade of the torque coefficients measured via pressure taps (EAEROTQ). See the UAE Phase VI report for more information: nrel.gov/docs/fy02osti/29955.pdf. I would expect the LSSTQ to be more accurate.

Best regards,

Dear Sir
Thank you
But Can I know why there is a difference between estimated torque from integration along the blade span with LSST torque?
Since I’m using BEM theory for stall delay, my computed torque from BEM agrees with estimated torque but not with LSST. So there is a considerable difference in power.

Regards
Ijaz

Dear Ijaz,

As described in the UAE Phase VI report I linked above, the estimate torque is only based on a few pressure tap measurements along one of the two blades–so, clearly only an estimate.

In general, the choice of airfoil coefficients (lift and drag versus angle of attack) has a strong effect on the BEM solution. Inaccuracies in the airfoil coefficients and limitations in BEM theory itself will effect the accuracy of the BEM solution. Often, airfoil coefficients are calibrated to match aerodynamic measurements to get the necessary accuracy out of BEM.

Best regards,

Dear Sir

Thanks,
But my doubt is what brings the difference in estimated torque from pressure measurements and measured torque at high wind speeds?
I’m sorry for keep on asking it.

Dear Ijaz,

The estimated torque is calculated from the use of a few pressure measurements, which are likely not sufficient to fully characterize the aerodynamic loading of the blade.

Best regards,

Hi Sir
Thank you
I have one more doubt, I noticed in Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns" that estimated torque is based on the equation as attached in the image
Can I know
why the conventional BEM formula is not used DQ=0.5densityNo of BladesU_rel^2chordCtorqueradius*dr;
Also
In the formula provided how to find Area (it has been mentioned trapezoidal area, what is it)?
Is the value of rn is just radius from origin?

Dear Ijaz,

The formulas are the same with:

  • QNORM = 0.5densityU_rel^2 and
  • area = chord*dr

The text above Eq. (14) describes how the areas where discretized, when it says:

Yes, r_n is the local radius.

Best regards,

Hi Every one

I am looking for data (Low speed torque) on NREL phase VI turbine rotor for configuration H.

Regards
Sijal Ahmed

Dear Sijal,

As mentioned in the following forum topic: http://forums.nrel.gov/t/nrel-phase-vi-measurement-data/1628/3, Lee Jay Fingersh of NREL (LeeFingershnrelgov) is now responsible for distributing the UAE Phase VI data until a more permanent solution is found.

Best regards,