APPLIED HYDRAULICS ENGINEERING
Budget: ₹600 – ₹1,500 INR
TURBINE CHARACTERISTIC CURVE
Introduction
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:
ž1. The speed of the turbine N
ž2. The discharge Q
ž3. The net head H
ž4. The power developed P
ž5. The overall efficiency n
ž6. Gate opening (this refers to the percentage of the inlet passages provided for water
to enter the turbine)
CONSTANT HEAD CHARACTERISTICS CURVES
žHead and gate opening are kept constant.
žSpeed is varied by changing water flow through inlet opening.
Overall efficiency and unit quantities are calculated and plotted against speed as abscissa.
Significances of main characteristics curve
žDischarge of pelton wheel depends only on gate opening.
žDischarge decreases and increases respectively for francis and kaplan turbines with increase in speed.
žPower is max at a particular speed and so is efficiency.
žMax efficiency of pelton wheel occurs at same speed irrespective of %of GO.
Constant speed characteristics curves
žIn 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.
žThe overall efficiency is aimed at its maximum value.
žThe curves drawn are
P vs Q
no vs Q
no vs Pu
no max vs % Full load
Significances of constant speed characteristics curves
žAt 100% full load overall efficiency is near about maximum efficiency .
žThe max. overall efficiency of all turbines is same.
žA min discharge is required to set turbine runner into motion.
žOutput power is directly proportional to discharge for constant head.
žOverall efficiency remains nearly constant beyond a particular value of discharge.
Constant efficiency curves
žThese curves are plotted from data which can be obtained from the constant head and constant speed curves.
žThe object of obtaining this curve is to determine the zone of constant efficiency so that we can always run the turbine with maximum efficiency.
žThis curve also gives a good idea about the performance of the turbine at various efficiencies.
Model Testing of Turbines:
The performance of a prototype turbine can be determined by model analysis. Tests are conducted on a dynamically similar model and from the properties of the model turbine, the corresponding properties of the prototype turbine can be determined.
The data that must be 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 ƞ0
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:
(i) Constant head curves or main characteristic curves
(ii) Constant speed curves or operating characteristic curves
(iii) Constant efficiency curves, or Muschel curves.
(i) Constant Head Curves or Main Characteristic 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 quantity Qu and the overall efficiency ƞ0 are determined.
The characteristic curves drawn are:
(a) Unit quantity vs unit speed
(b) Unit power vs unit speed
(c) Overall efficiency vs unit speed
(ii) Constant Speed Curves or Operating Characteristic 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.
These curves are plotted from data which can be obtained from the constant head.....
Introduction
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:
ž1. The speed of the turbine N
ž2. The discharge Q
ž3. The net head H
ž4. The power developed P
ž5. The overall efficiency n
ž6. Gate opening (this refers to the percentage of the inlet passages provided for water
to enter the turbine)
CONSTANT HEAD CHARACTERISTICS CURVES
žHead and gate opening are kept constant.
žSpeed is varied by changing water flow through inlet opening.
Overall efficiency and unit quantities are calculated and plotted against speed as abscissa.
Significances of main characteristics curve
žDischarge of pelton wheel depends only on gate opening.
žDischarge decreases and increases respectively for francis and kaplan turbines with increase in speed.
žPower is max at a particular speed and so is efficiency.
žMax efficiency of pelton wheel occurs at same speed irrespective of %of GO.
Constant speed characteristics curves
žIn 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.
žThe overall efficiency is aimed at its maximum value.
žThe curves drawn are
P vs Q
no vs Q
no vs Pu
no max vs % Full load
Significances of constant speed characteristics curves
žAt 100% full load overall efficiency is near about maximum efficiency .
žThe max. overall efficiency of all turbines is same.
žA min discharge is required to set turbine runner into motion.
žOutput power is directly proportional to discharge for constant head.
žOverall efficiency remains nearly constant beyond a particular value of discharge.
Constant efficiency curves
žThese curves are plotted from data which can be obtained from the constant head and constant speed curves.
žThe object of obtaining this curve is to determine the zone of constant efficiency so that we can always run the turbine with maximum efficiency.
žThis curve also gives a good idea about the performance of the turbine at various efficiencies.
Model Testing of Turbines:
The performance of a prototype turbine can be determined by model analysis. Tests are conducted on a dynamically similar model and from the properties of the model turbine, the corresponding properties of the prototype turbine can be determined.
The data that must be 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 ƞ0
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:
(i) Constant head curves or main characteristic curves
(ii) Constant speed curves or operating characteristic curves
(iii) Constant efficiency curves, or Muschel curves.
(i) Constant Head Curves or Main Characteristic 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 quantity Qu and the overall efficiency ƞ0 are determined.
The characteristic curves drawn are:
(a) Unit quantity vs unit speed
(b) Unit power vs unit speed
(c) Overall efficiency vs unit speed
(ii) Constant Speed Curves or Operating Characteristic 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.
These curves are plotted from data which can be obtained from the constant head.....