2. HYDROLOGIC CYCLE
The hydrologic cycle begins when water evaporates from the surface of the ocean. As moisture of air is
lifted, it cools down and water vapor condenses to form clouds. Moisture is transported around the globe
until it returns to the surface as precipitation. Once the water reaches the ground, one of two processes
1) some of the water may evaporate back into the atmosphere
2) the water may penetrate the surface and become groundwater. Groundwater either seeps its way to
into the oceans, rivers, and streams, or is released back into the atmosphere through transpiration.
The balance of water that remains on the earth's surface is runoff, which empties into lakes, rivers and
streams and is carried back to the oceans, where the cycle begins again.
5. FLOW IN OF WATER IN RIVERS
• It is only due to hydrologic cycle that formation of rivers is made possible by nature.
• As the water evaporates, it gains potential energy. Water utilizes maximum potential energy when it is
in form of clouds.
• When precipitation occurs, this potential energy is transformed into kinetic energy by the action of
• Flow in river water is produced by this conversion of energy until water flows into seas or oceans.
6. UTILIZING THE FLOW/ENERGY OF WATER
• The energy in flowing water is utilized by obstructing the
flow of water, thus creating a water head and using it
according to current energy requirements.
• The structures used for this purpose are known as Dams.
7. TURBINES AND CATEGORIES OF HYDRAULIC TURBINES
• A turbine is a rotary engine in which the kinetic energy of a moving fluid is converted into mechanical
energy by causing a bladed rotor to rotate.
There are 3 categories of hydraulic turbines such as:
Impulse turbines converts the kinetic energy of a jet of water to mechanical energy.
Reaction turbines converts potential energy in pressurized water to mechanical energy.
Gravity turbines are driven simply by the weight of water entering the top of the turbine.
8. IMPULSE TURBINES
• In an impulse turbine, the head of water is converted into kinetic energy by discharging water through a
carefully shaped nozzle. The jet is discharged into air and is directed onto curved buckets fixed on the
periphery of the runner to extract the water energy and convert it to useful work.
Types of Impulse Turbines
There are 3 types of modern impulse turbines:
1) Pelton Wheel
2) Turgo Turbine
3) Cross flow Turbine
9. PELTON WHEEL
• The Pelton wheel is one of the most efficient type of hydraulic turbine. It was invented by Lester Allan
Pelton (1829–1908) in the 1870. It is an impulse machine, meaning that it uses the principle of
Newton’s second law to extract energy from a jet of fluid.
• Pelton wheel is considered for use in dams where the flow of water is low and medium to high water
head is present.
10. WORKING PRINCIPLE OF PELTON WHEEL
• The Pelton Turbine consists of a wheel with a
series of split buckets set around its rim.
• A high velocity jet of water is directed
tangentially at the wheel.
• The jet hits each bucket and is split in half, so
that each half is turned and deflected back
almost through 180º.
• Nearly all the energy of the water goes into
propelling the bucket and the deflected water
falls into a discharge channel below.
14. TURGO TURBINE
• The Turgo turbine is similar to the Pelton but the jet strikes the plane of the runner at an angle (typically
20° to 25°) so that the water enters the runner on one side and exits on the other.
• Therefore the flow rate is not limited by the discharged fluid interfering with the incoming jet (as is the
case with Pelton turbines).
• As a consequence, a Turgo turbine can have a smaller diameter runner and rotate faster than a Pelton
for an equivalent flow rate.
• The Turgo turbine is an impulse water turbine designed for medium head applications.
• In factory and lab tests Turgo Turbines perform with efficiencies of up to 90%.
• Complex blade design but greater flow possibilities.
16. CROSS FLOW TURBINES
• Cross flow Turbines are also known as Banki Mitchell Ossberger
• A cross-flow turbine is drum-shaped and uses a rectangular-section
nozzle directed against curved vanes on a cylindrically shaped runner.
• The cross-flow turbine allows the water to flow through the blades
twice. In the first pass, the water flows from the outside of the blades
to the inside. The second pass is from the inside back out.
• A guide vane at the entrance to the turbine directs the flow to a
limited portion of the runner.
• The cross-flow was developed to accommodate larger water flows and
lower heads than the Pelton.
19. REACTION TURBINES
• Reaction turbines exploit the oncoming flow of water to generate hydrodynamic lift forces to propel the
runner blades. They are distinguished from the impulse type by having a runner that always functions
within a completely water-filled casing.
• All reaction turbines have a diffuser known as a ‘draft tube’ below the runner through which the water
discharges. The draft tube slows the discharged water and so creates suction below the runner which
increases the effective head.
There are Two main Types of Reaction Turbines :
1) Kaplan Turbine
2) Francis Turbine
20. KAPLAN TURBINE
• Kaplan turbines are suitable for power extraction when water energy
is available at low head and high flow rate.
• Head = 2-25 m
• Flow rate = 70-800 m^3/s
• Flow of water from Kaplan is axial because the absolute velocity of
flow is parallel to the axis of turbine.
• Kaplan have guide vanes which helps meet variable load demands
and the blades of Kaplan also adjusts the angle of attack as the flow
rate of water changes.
• Huge pressure is dropped in Kaplan thus cavitation is most common
in them. It is reduced by using special stainless steel and usage of
21. WORKING PRINCIPLE OF KAPLAN
• In Kaplan turbine flow is entered through a spiral casing.
Decreasing area of casing makes sure that flow is entered to
the central portion almost at uniform velocity throughout the
perimeter. Water after crossing the guide vanes passes over
the runner. Finally it leaves through a draft tube.
• When water flows over it, it will induce a lift force due to
airfoil effect. Tangential component of lift force will make the
runner rotate. This rotation is transferred to a generator for
• When water flows over the runner, it will induce a lift force
due to airfoil effect. Tangential component of lift force will
make the runner rotate. This rotation is transferred to a
generator for electricity production.
23. FRANCIS TURBINE
• Francis turbines are most extensively used because of their wider range of suitable heads,
characteristically from three to 600 meters.
• Flow is through the scroll into guide vanes and onto the runner thus maintaining constant flow
throughout the scroll towards the runner.
• The Francis turbine is essentially a modified form of propeller turbine in which water flows radially
inwards into the runner and is turned to emerge axially.
25. GRAVITY TURBINES
• The Archimedes Screw has been used as a pump for centuries, but has only recently been used in
reverse as a turbine.
• It’s principle of operation is the same as the overshot waterwheel, but the clever shape of the helix
allows the turbine to rotate faster than the equivalent waterwheel and with high efficiency of power
conversion (over 80%).
• However they are still slow-running machines, which require a multi-stage gearbox to drive a standard
• A key advantage of the Screw is that it avoids the need for a fine screen and automatic screen cleaner
because most debris can pass safely through the turbine. The Archimedian screw is proven to be a ‘fish-
• Convert kinetic energy of water jet hitting
• impulse turbines change velocity of a water jet
• No pressure drop across turbines
• Derives power from pressure drop across turbine
• Changes pressure as it moves through the
turbine and gives up its energy
• Totally immersed in water
• Angular & linear motion converted to shaft
30. DESIGN CHANGES FOR FISH PROTECTION
• Alden turbine is designed to minimize injury to fishes in water.
These are the design considerations which were given priority while developing this turbine:
• Limit the relative velocity of the inflow to the blades.
• Have a high minimum pressure.
• Limit negative pressure change rates.
• Limit the maximum flow shear.
• Minimize the number of leading blade edges.
• Maximize the distance between the runner inlet and wicket gates trailing edges and minimize clearances (i.e.,
gaps) between other components.
• Maximize the size of flow passages.