Selection of Hydro Turbine Main for turbine .ppt

HYDRO POWER GENERATION
Rajneesh Vachaspati
Dy. Director
NPTI,Faridabad

• A big advantage of hydroelectric power is the ability to quickly and
readily vary the amount of energy generated, depending on the load
presented at that moment.
• It utilizes a renewable energy source as “fuel” (water)
• The generation process is environmentally clean
• High reliability
Disadvantage of HYDROPOWER
• It requires large initial investments
• Long transmission lines
• Social and environmental impacts for large-scale schemes
ADVANTAGE OF HYDROPOWER GENERATION

Hydro Power Plant
Contents
Introduction
Types of hydro plants
Major components
Performance
Summary

•Flowing water is
directed at a turbine.
•The flowing water
causes the turbine
to rotate, converting
the water’s kinetic
energy into
mechanical energy.
WORKING OF HYDRO TURBINE

• The mechanical energy produced by the
turbine is converted into electric energy
using a turbine generator.
• Inside the generator, the shaft of the
turbine spins a magnet inside coils of
copper wire.
• It is a fact of nature that moving a magnet
near a conductor causes an electric
current.

HOW POWER IS GENERATED
1. Important hydro turbine parameters:
2. Power generated from hydro plant is given by:
H
Q
P 


P = Power
Q = Rate of water flow
H = head
 = efficiency
3. Specific speed:
a. Speed of turbine when delivers 1
horsepower under 1 metre head
Power Head Efficiency Specific speed Discharge
b. Independent of shape and size of turbine
c. Helps in selecting suitable type of turbine
4
/
5
H
P
N
Ns  N = Turbine speed

Components of Hydropower Plant

HYDRO TURBINES
Advantages:
 Water => cheapest source of energy
 Low operation & maintenance cost
 Quick in starting up
 Quick respond to load variation
 Plant has longer life
 Less labour requirement
 No emission
 Has other useful functions
 Reliable=> less trippings
Disadvantages:
 High initial construction cost
 Located far from load centres
 Dependent on water availability
 Long construction time
 Environmental issue e.g. deforestration

CLASSIFICATION OF HYDRO POWER
SCHEMES
• Based on Head Available
Ultra Low Head H < 3 M
Medium Head Scheme H <75 M
High Head Scheme H > 75 M

CLASSIFICATION OF HYDRO POWER
SCHEMES
• Based on Generation Capacity
CLASSIFICATION POWER RATING
MICRO-HYDRO < 100 kW
MINI-HYDRO 100 kW – 3MW
SMALL-SCALE HYDRO 3 MW – 25 MW

OTHER HYDRO POWER SCHEMES
1. Hydro plants can be classified according to water flow/storage
characteristics
2. Types:
Run of river plants (mini hydro)
Storage/reservoir plants
Pump storage plants
3. Type 1: Run of river plants:
a. Utilize the water flow as it runs through the year
b. No significant storage/dam for power generation
c. Typical for mini-hydro scheme => suitable for low
consumption at remote areas
d. Typical size : 10 - 1600 kW

3. Type 2: Storage/reservoir plants:
a. Large size reservoirs (dams) => large generation capacity
b. Most common type for commercial power generation

• GROSS HEAD of a hydropower facility is the
difference between headwater elevation and
tailwater elevation.
• NET HEAD is the effective head on the turbine
and is equal to the gross head minus the
hydraulic losses before entrance to the turbine
and outlet losses
Hydraulic Head

4. Pump storage plants:
b. Water storage obtained by pumping back from tail race
=> utilize low value, off-peak power (usually surplus)
a. Used only for short duration=> to meet peak load
c. Improves overall efficiency & reliablity of system grid

Reservoir Dam Inlet water ways Power house Tailrace
COMPONENTS OF HYDRO POWER PLANT

MAJOR COMPONENTS
1. Reservoir:
a. Includes catchment area and water reservoir
c. Head race => water surface level of the reservoir
d. Reservoir can be natural or artificial (i.e. with dam)
b. Purpose: to store water
2. Dam:
a. A structure of masonry and/or rock fill built across a river
b. Purpose: i) to provide head of water
ii) to create storage or pondage

MAJOR COMPONENTS
3. Inlet water ways:
a. Passages through which is conveyed from dam to power house
c. Penstock => closed pressure pipes made
of reinforced concrete or steel
b. Includes: Penstock/tunnel, spillways
d. Tunnel => made by cutting mountains
e. Spillways => provide discharge of surplus water from
storage reservoir into river
SPILLWAYS

MAJOR COMPONENTS
4. Power House:
Building that houses turbines, generators and other auxiliaries
5. Tail race:
a. Passage for discharging
water leaving the turbine
TAIL RACE

Surge tank
• Located near the beginning of the penstock.
• As the load on the turbine decreases or during load rejection
by the turbine the surge tank provides space for holding water.

• surge tank over comes the abnormal pressure in the conduit
when load on the turbine falls and acts as a reservoir during
increase of load
he
turbine.

TURBINES
• turbines are used to convert the energy water of falling water
into mechanical energy.
• water turbine is a rotary engine that takes energy from
moving water.
• flowing water is directed on to the blades of a turbine runner,
creating a force on the blades

• Since the runner is spinning, the force acts through a distance
n this way, energy is transferred from the water flow to the
turbine.
• The principal types of turbines are:
1) Impulse turbine
2) Reaction Turbine

25
CLASSIFICATION OF TURBINES
Pelton Turbines (Impulse Turbine)
For Head Between 400-1500 Mtrs.
Francis Turbines (Reaction Turbine)
Propeller/kaplan Turbines (Reaction Turbine)

Type of Action on the runner
(a) Impulse Turbine (b) Reaction Turbine
2) Direction of Flow through Runner
(a) Tangential flow (b) Radial flow ( c)
Axial flow
3) Head at inlet of Turbine
(a) High head (b) Medium head ( c ) Low
head
4) According to specific speed
( a) High (b) Medium ( c) Low

Impulse turbines: mainly used in high head plants.
• the entire pressure of water is converted into kinetic
energy in a nozzle and the velocity of the jet drives the
blades of turbine.
• The nozzle consist of a needle, and quantity of water jet
falling on the turbine is controlled this needle placed in
the tip of the nozzle.
• If the load on the turbine decreases, the governor
pushes the needle into the nozzle, thereby reducing the
quantity of water striking the turbine.

Examples of Impulse turbines are:
• Pelton Wheel.
• Turgo
• Michell-Banki (also known as the Cross
flow or Ossberger turbine.

Reaction turbines : are mainly for low and medium
head plants.
• In reaction turbine the water enters the runner
partly with pressure energy and partly with
velocity head.
• Most water turbines in use are reaction turbines
and are used in low (<30m/98 ft) and medium
(30-300m/98–984 ft)head applications.
• In reaction turbine pressure drop occurs in both
fixed and moving blades.

Examples of reaction turbines are:
Francis turbine
Kaplan turbine

34
Schematic of Francis Turbine

38
Fixed-Pitch Propeller Turbine
"Water Turbine," Wikipedia.com

39
Kaplan Turbine Schematic
"Water Turbine," Wikipedia.com

40
Comparison of Impulse & Reaction Turbines
 Experience has shown that under given conditions, wear
will be more in reaction turbines i.e. Propeller, Kaplan and
Francis. This is because water enters under pressure and
the under water components experience a severe erosive
action of water on the metal.
 In case of pelton wheels, water hits the buckets and
because of this impact, buckets wear out but this may not
be much as compared to the reaction turbines, where the
water is made to enter through constrained paths like
vanes and gates.

43
SPECIFIC SPEED
It provides a means of comparing the speed of all
types of hydraulic turbines on the same basis of
head and horse power capacity.
 A single runner having higher specific speed
than another runs at a higher number of
revolutions per minute to deliver the same horse
power under the same head.

Significance of Specific Speed on Turbine Blade Design
1 To determine Turbine Type
1. Low specific speed: Impulse turbines like Pelton turbines are
selected. These turbines operate with high head and low flow rate.
2. Medium specific speed: Francis turbines are used. These work with
medium head and flow rate.
3. High specific speed: Kaplan turbines or propeller turbines are
selected for low head and high flow rate situations.
2. Blade Shape and Curvature:
1. Low Specific Speed: In Pelton turbines, the blades are shaped like
buckets or cups, designed to capture the kinetic energy of water jets.
These are more deeply curved to capture high-velocity water in high-
head conditions.
2. Medium Specific Speed: Francis turbine blades are curved and
shaped to allow water to flow smoothly through the turbine, both radially
and axially. This involves a combination of impulse and reaction forces.
3. High Specific Speed: Kaplan turbines, designed for low head and high
flow, have long, twisted blades that resemble propeller blades,
optimized to work under lower velocities but higher water volume.

3. Blade Size and Number:
•As specific speed increases, the number of blades typically increases, and
the blades become smaller and more streamlined. For example, a Kaplan
turbine may have several thin, long blades, while a Pelton turbine has fewer,
but larger and more robust buckets.
•In low-specific-speed turbines (e.g., Pelton), the blades are larger and fewer
because they need to handle high head with lower flow rates.
•In high-specific-speed turbines (e.g., Kaplan), the blades are numerous and
smaller to manage larger flow rates with lower heads.
4. Efficiency Considerations:
•Specific speed also influences the efficiency of the turbine. Turbines operate
most efficiently at specific speed ranges:
• Pelton turbines (Ns: 10-60) are suited for high-head, low-flow
conditions.
• Francis turbines (Ns: 60-300) operate efficiently at medium head and
medium flow.
• Kaplan turbines (Ns: 300-1000) are efficient in low-head, high-flow
conditions.
•If the specific speed is not well-matched to the site conditions, the turbine
blades won't perform optimally, resulting in reduced efficiency.

5. Axial vs Radial Flow:
•At low specific speeds (like Pelton), turbines operate with purely impulse
forces, meaning the blades redirect the water without internal pressure
changes, making the design simpler.
•At higher specific speeds (like Kaplan and Francis turbines), the turbines
rely on reaction forces as well, meaning the blades must allow water to
both enter and exit at carefully controlled angles to manage pressure
changes within the turbine.
Practical Implications:
•Blade Angle and Twist: High-specific-speed turbines like Kaplan have
blades that can be adjusted (variable pitch) to optimize performance
across a range of flow conditions. The blade twist allows better control of
water as it moves axially through the turbine.
•Blade Strength: The higher the specific speed, the more streamlined the
blades, but they must also be strong enough to handle the larger volumes
of water at lower pressures.
•Material Choice: In high-specific-speed turbines, where flow volumes are
large, the blades must be designed with materials that withstand cavitation
(formation of vapor bubbles) and wear.

Conclusion
Specific speed directly dictates the type of turbine and the design of its
blades. It governs the blade's shape, size, curvature, and number,
ensuring that the turbine can operate efficiently under the given head and
flow conditions. Understanding and optimizing specific speed during
design ensures that the turbine maximizes energy extraction while
minimizing wear, cavitation, and inefficiencies.

50
RANGE OF SPECIFIC SPEEDS
 Pelton turbines with one jet Ns upto = 10 to 35
 Pelton turbines with two jets Ns up to = 26 to
40
 Pelton turbines with multiple jets Ns up to = 40 to
67
 Francis turbine Ns = 67 to 450
 Propeller and Kaplan Ns = 364 to 910

The powerhouses contain the turbine, generator, control equipment,
transformers, and supporting auxiliary equipment.
Below the turbines are the draft tubes and their gates
Types of powerhouses:
•Integral intake powerhouse
•Conventional surface powerhouse
•Underground powerhouse
Powerhouses

Conventional Surface Powerhouse

An integral intake powerhouse refers to a type of hydroelectric power station
where the intake structure (where water enters the system) and the powerhouse
(where electricity is generated) are combined into a single, integrated structure. This
design is common in run-of-river hydroelectric plants and smaller-scale hydro
projects where the water intake and the turbine-generating components are co-
located to improve efficiency, reduce construction costs, and minimize environmental
impact.
Key Features:
1.Integrated Design: The intake, which directs water from the river or reservoir, is
built together with the powerhouse. This reduces the need for long penstocks (pipes
or tunnels) and simplifies the layout.
2.Run-of-River Projects: Typically used in low-head hydroelectric projects, where
water flows directly from the river to generate electricity, without the need for large
dams or reservoirs.
3.Compact Structure: The integrated design makes the power station more
compact, which can be especially beneficial in areas where space is limited or
environmental regulations are strict.
4.Efficient Operation: Since the water intake and turbines are co-located, energy
loss from water transport is minimized, leading to greater efficiency.

DRAFT TUBE
• is a pipe or passage of gradually increasing cross sectional
area, which connect to the exit to tail race.
• it reduces high velocity of water discharged by the turbine.
• draft tube permits turbines to be installed at a higher level
than the tail race level, which help the maintenance and repair
of turbines.
• It permits a negative head to be established at the outlet of
the runner and thereby increase the net head on the turbine.
The turbine may be placed above the tail race with out any
loss of net head and hence turbine may be inspected
properly
• It converts a large proportion of the kinetic energy(V2/2g)
rejected at the outlet of the turbine into useful pressure
energy. Without the draft tube, the kinetic energy rejected at
the outlet of the turbine will go waste to the tail race.

Hence by using draft tube, the net head on the turbine
increases. The turbine develops more power and also
the efficiency of the turbine increases.

 Cavitation is formation of vapor bubbles in the liquid
flowing through any Hydraulic Turbine. It describes the
phenomenon of phase changes of liquid-to-gas and gas
-to-liquid that occur when the local fluid dynamic
pressures in areas of accelerated flow drop below the
vapor pressure of the local fluid. the liquid boils and
large number of small bubbles of vapors are formed.
These bubbles mainly formed on account of low
pressure are carried by the stream to higher pressure
zones where the vapors condense and the bubbles
suddenly collapse, as the vapors are condensed to
liquid again.
 Cavitation is most likely to occur near the fast moving
blades of the turbines and in the exit region of the
turbines.
CAVITATION IN HYDRO TURBINE

PROBLEMS DUE TO CAVITATION AND SILT EROSION OF
TURBINE BLADES

IMAGES OF CAVITATIONS NEAR TURBINE BLADE

Thanks
65
For further quarries feel free to contact at
rvachaspati@gmail.com

Selection of Hydro Turbine Main for turbine .ppt

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