a question about tip-speed-ratio
 

Hi, I am modeling wind turbines using Star-CCM+. I have a question about tip-speed-ratio (TSR). I saw a lot of papers using the following equation to calculate the TSR

TSR=R*w/U
R-rotor diameter, m
w-rotational speed, rad/s
U-fluid velocity at the rotor, m/s

The method used is to fix U and vary w so that a series of TSRs will be obtained as a function of w. My question is that the cp-TSR curve (Note: cp is the power coefficient of a turbine) obtained based on the specific U, is it independent of U? In other words, if we use another U, will the cp-TSR curve be the same? I kind of think that this curve should be unique instead of being different. However, I cannot find a reason to convince myself. Anybody can help? Many thanks.

Tsr
 

Hi,

so here is how it works:

1. You pick a design tip speed ratio for your turbine. This depends on blade length, acoustics and other stuff.

2. From the cp-lambda curve you get your theoretical maximum cp.
This really only depends on lambda and not on the wind speed. The trick is

3. Now you have to adjust your rotor speed so you can have the same TSR for every wind speed up to your rated wind speed.

This is the only way to get maximum power output and only smaller turbines are fixed speed because there variable speed is to complicated/expensive.

Makes sense?

Thomas

PS: The rotor speed is adjusted via a torque control that regulates the generator