01-11-2016, 03:08 PM
1463052735-CharCurMNSP.pdf (Size: 23.08 KB / Downloads: 4)
These are curves which are characteristic of a particular turbine which helps in studying
the performance of the turbine under various conditions. These curves pertaining to any
turbine are supplied by its manufacturers based on actual tests.
The data that must be obtained obtained in testing a turbine are the following:
1. The speed of the turbine N
2. The discharge Q
3. The net head H
4. The power developed P
5. The overall efficiency o 6. Gate opening (this refers to the percentage of the inlet passages provided for
water to enter the turbine)
The characteristic curves obtained are the following:
a) Constant head curves or main characteristic curves
b) Constant speed curves or operating characteristic curves
c) Constant efficiency curves or Muschel curves
Constant head curves: Maintaining a constant head, the speed of the turbine is varied by
admitting different rates of flow by adjusting the percentage of gate opening. The power
P developed is measured mechanically. From each test the unit power Pu, the unit speed
Nu, the unit discharge Qu and the overall efficiency o are determined. The characteristic
curves drawn are
a) Unit discharge vs unit speed
b) Unit power vs unit speed
c) Overall efficiency vs unit speed
Constant speed curves: In this case tests are conducted at a constant speed varying the
head H and suitably adjusting the discharge Q. The power developed P is measured
mechanically. The overall efficiency is aimed at its maximum value.
The curves drawn are
P vs Q
o vs Q
o vs Pu o max vs % Full load
Constant efficiency curves: These curves are plotted from data which can be obtained
from the constant head and constant speed curves. The object of obtaining this curve is to
determine the zone of constant efficiency so that we can always run the turbine with
maximum efficiency.
This curve also gives a good idea about the performance of the turbine at various
efficiencies.