Question

Type of characteristic curves for turbines

Answer 1

Characteristic curves of hydraulic turbines are are the curves with the help of which the exact behaviour and performance of the turbine under different working conditions can be known. These are plotted from the results of the tests performed..the important parameters which are varied during a test are -1.speed 2.head 3.discharge 4.power 5.overall efficiency 6.Gate opening..

There are 3 main and very important curves 
1. Constant Head Curve
2. Constant Speed Curve
3. Constant Efficiency Curve.

1.Constant Head Curve-
In this head and gate opening is kept constant ..thus for every value of speed we get corresponding values of power and discharge..thus overall efficiency can be calculated

2.Constant Speed Curve -
In this speed and head is kept constant.thus we can find out variation in power and efficiency wrt discharge...it also helps tells us about the minimum discharge needed to overcome the friction

3.Constant Efficiency Curve -
Obtained at different gate openings.thus for a given efficiency there are two values of discharge and  speeds. If efficiency is maximum then we get only one value.
They are helpful in determining the zone of  constant efficiency  and for prediction of performance of turbines at different efficiencies