What is the function of tsr

[joelhacker]

I've seen a lot of postings where folks will post their tip speed ratio, but I have yet to figure out what it represents and how this is important to the design of a HAWT.  can you guys please help out?

[RP]

Its the ratio of tip speed to wind speed.  If the wind is going 10mph and the tips of the blades are swinging around at 70 mph, this is a TSR of seven.

[farmerfrank]

A high TRS relies on high speed to create power ,but very high speeds present the problems of centifugal forces, noise and blade wear. Low TSR blades make power from higher torque but the blades must be wider,and thus heavier. Like everything else in life,there are always trade offs.

[richhagen]

I believe the following is correct, however, I'm sure someone will correct me if I am in error.

The tip speed ratio is a dimentionless number, it represents the ratio of the speed of the tips of the blades to the speed of the wind.  If the assembled rotor had a tip speed ration of 6 and the wind was blowing at 10 miles per hour, then the tips would be traveling at 60Mph.  It is interesting to note that the distance traveled in one revolution of the blades is Pi multiplied by the blade diameter.  This means that a 1 meter blade with a TSR of 6 would have to spin at twice the rpm of a 2 meter diameter blade with the same TSR.  While blades are often optimized to provide the maximum power (have maximum lift from the airfoil design)at a specific TSR - hence RPM and wind speed, the Actual TSR of the assembled rotor will depend upon the loading of the alternator and friction upon the blades, and most likely will not remain constant over a wide range of wind speeds.  The tip speed ratio is a usefull number to know when comparing blades for an alternator for which the power generated/rpm curve is known.  Rich Hagen