Wednesday, December 27, 2017

How to sizing a Kaplan turbine with HPP-Desing

What is a Kaplan turbine?
A Kaplan turbine is the most common type of propeller turbine, in which the angle of the blades and the gates to the flow can be adjusted. This type of turbine is most frequently used in the low- to moderate-head range and medium- to high- discharges.
When to use a Kaplan turbine
A Kaplan turbine can be used for heads ranging 2 to 50 m and discharges 1 to 100 m3/s (see the yellow line in the picture). Multiple turbines allow to increase the total discharge.


How to select a Kaplan turbine in HPP-design?
Just create a new sizing, enter a value of net head [H] and maximum discharge [Q] suitable for Kaplan turbines (e.g. H=20m, Q=10 m3/s), click “create sizing” and select the icon of the Kaplan turbine.

Why is not possible to select the Kaplan icon?
Check the values of net head [H] and maximum discharge [Q] you entered, probably they are out of the range of the Kaplan turbine ( H = 2 to 50 m and Q = 1 to 100 m3/s).

Why there are two numbers on the icon of Kaplan turbines?
The first refers to the number of available turbines without the gearbox while the second, if present, refers to the number of available turbines with the gearbox.
What is the “enable gearbox” switch?
When switched on it allows to use a gearbox between the turbine and the generator in order to better match the optimal speed of the turbine. The switch is enabled only for turbines with nominal power below a given value, when a low rotation speed is suggested for efficiency reasons. For high nominal powers a multiple pole generator is more effective and less expensive.

What is the “Suggested configuration”?
Is the optimal solution in terms of efficiency and it’s highlighted in green in the list.
Once I’ve selected the turbine on the list are there other possible options?
Yes, on the sizing-detail page you can choose the regulation strategy of the turbine and the type of generator.
How does the regulation strategy affects my turbine?
There are different possibilities concerning the regulation strategy:

·         Full Kaplan

·         Semi Kaplan rotor

·         Semi Kaplan stator

·         Helix

From the top to the bottom the equipment becomes cheaper while the efficiency at partial loads decreases, as you can see on the efficiency graph just below the sizing details.
How does the choice of generator affects my turbine?
For small powers only asynchronous generator are available, while for high power only synchronous are adopted. In between the user can choose a synchronous or asynchronous generator, the first one being capable of reactive power control and a bit more efficient, while more expensive than the second one.
HPP- Design will help you in this choice, providing accurate sizing data and energy calculation for every type of turbine!
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