Speed Calculations

[Lansonus]

How do you calculate the speed at the ends or the blades on a fan or wind generator?

[Norm]

  Diameter *  3.14 * rpm = ft.per min.

14. ft.diameter * 314=43.96 or about 44ft. so,
    
60. mph is a mile a minute or 5280 ft.per min.
    
5280. /44 = 120....so a 14ft.diameter blade...
      
      

at 120rpm would have tips traveling 60mph.

    Hope this helps...probably didn't explain

it very good?

   A 20inch fan at a 1000rpm. would have the

blade tips traveling about 5338ft per min. or

roughly just about 60mph.

                  ( :>) Norm.

[dinges]

Don't you need to take Tip Speed Ratio (TSR) of the prop in account too?

I.e., wind speed = 10m/s; TSR of turbine = 5

Speed of tip = 10*5 = 50 m/s

From there on, you can calculate RPMs etc if you know the diameter of the prop, like in Norm's explanation.

It's the way I make my calculations, hope I'm not wrong...

Peter,

The Netherlands.