Nozzle Control in Turbines

I will try and explain the working of the controls of a Pelton or impulse turbine.

The power available in a turbine is proportional to the volume and speed of water passing through the nozzle

The volume of water (and speed) at the nozzle is controlled by moving the needle forward and backwards in the nozzle and increasing or decreasing the area of the nozzle. allowing more or less water to pass.

The mechanical output of the governor is depended on speed and is used to move the needle in and out.

What happen is that as the load is decreased the turbine will tend to run faster which will move the needle forward and thus reducing the area and volume. until the volume of water is in balances with the load. Increasing the load will decrease the speed which will open the nozzle further.

This governing action is dampened and therefore not very fast and another method of fast governing was introduced. A deflecting scoop is moved into the stream of the nozzle to quickly reflect the surplus water away from the buckets. This works very fine but reduces the water to power efficiency. It is therefore only used for very short periods.

I cannot provide a link but you can google for - Voith (pelton) impulse turbine.

Steam or Gas Turbine?

The function and practice of Nozzle control is very different in each type.

Right! I forgot to add hydroturbine to the list, please forgive me!

More input! says number 5, er Turbotroll3.

TT3