Turbines
RAKESH V. ADAKANE
DEPARTMENT OF MECHANICAL
ENGINEERING
YCCE NAGPUR
HYDRAULIC TURBINES
The device which converts hydraulic energy into
mechanical energy or vice versa is known as
Hydraulic Machines.
The hydraulic machines which convert hydraulic
energy into mechanical energy are known as
Turbines and that convert mechanical energy
into hydraulic energy is known as Pumps.
Different type of turbine use in hydro power station
1.High head schemes. (Impulse turbine-pelton wheel)
( < 300 m.)
2.Medium head schemes.(reaction turbine ) (60m to 300 m.)
3.Low head schemes. (propeller turbine ) ( > 60m.)
IMPULSE TURBINE
(PELTON WHEEL)
GE Hydro
construction of penstock in hydro power station.`
Pelton to Francis
Pelton to Francis
UNIT 02
Reaction Turbines
Reaction turbines are those turbines which
operate under hydraulic pressure energy and
part of kinetic energy. In this case, the water
reacts with the vanes as it moves through the
vanes and transfers its pressure energy to the
vanes so that the vanes move in turn rotating
the runner on which they are mounted.
Reaction Turbines
Types
1. Radially outward flow reaction turbine
2. Radially inward flow reaction turbine
The main component parts of a reaction turbine are:
• (1) Casing, (2) Guide vanes (3) Runner with vanes (4) Draft tube
COMPONENT PARTS OF A REACTION
TURBINE
•
•
•
•
Casing: This is a tube of decreasing cross-sectional area with the axis of the
tube being of geometric shape of volute or a spiral. The water first fills the
casing and then enters the guide vanes from all sides radially inwards. The
decreasing cross-sectional area helps the velocity of the entering water from all
sides being kept equal. The geometric shape helps the entering water avoiding
or preventing the creation of eddies.
Guide vanes
Runner with vanes: The runner is mounted on a shaft and the blades are fixed
on the runner at equal distances. The vanes are so shaped that the water
reacting with them will pass through them thereby passing their pressure
energy to make it rotate the runner.
Draft tube: This is a divergent tube fixed at the end of the outlet of the turbine
and the other end is submerged under the water level in the tail race. The water
after working on the turbine, transfers the pressure energy there by losing all its
pressure and falling below atmospheric pressure. The draft tube accepts this
water at the upper end and increases its pressure as the water flows through the
tube and increases more than atmospheric pressure before it reaches the
tailrace.
The Francis Turbine
Francis turbines
•
It is a reaction turbine developed by an English born American Engineer, Sir J.B.
Francis.
•
The water enters the turbine through the outer periphery of the runner in the radial
direction and leaves the runner in the axial direction, and hence it is called ‘mixed flow
turbine’.
•
It is a reaction turbine and therefore only a part of the available head is converted into
the velocity head before water enters the runner.
•
The pressure head goes on decreasing as the water flows over the runner blades.
•
The static pressure at the runner exit may be less than the atmospheric pressure and as
such, water fills all the passages of the runner blades.
•
The change in pressure while water is gliding over the blades is called ‘reaction pressure’
and is partly responsible for the rotation of the runner.
•
A Francis turbine is suitable for medium heads (45 to 400 m) and requires a relatively
large quantity of water.
The Francis Installation
View of Draft tube in Hydro electric power plant.`
FORMULAE
1.
Speed ratio =
2.
Flow ratio =
u1
2g H
V
f 1
where H is the Head on turbine
where Vf1 is the velocity of flow at inlet
2 g H
3.
Discharge flowing through the reaction turbine is given by
Q =  D1 B1 Vf1 =  D2 B2 Vf2
Where D1 and D2 are the diameters of runner at inlet and exit
B1 and B2 are the widths of runner at inlet and exit
Vf1 and Vf2 are the Velocity of flow at inlet and exit
If the thickness (t) of the vane is to be considered, then the area
through which flow takes place is given by ( D1 nt) where n is the
number of vanes mounted on the runner.
Discharge flowing through the reaction turbine is given by
Q = ( D1 nt) B1 Vf1 = ( D2 nt) B2 Vf2
4.
The Head on the turbine is given by
Where p1 is the pressure at inlet.
2
H 
V2
2g

1
H 
p1
 g

V1
2
2 g
(V w 1u 1  V w 2 u 2 )
g
5. Work done per second on the runner =  a V1 (Vw1u1 Vw2u2)
=  Q (Vw1u1 Vw2u2)
 D1 N
6. u1 
60
7.
u2 
 D2 N
60
8. Work done per unit weight
W ork done per second
=
W eight of w ater striking per second
 Q  V w 1u 1  V w 2 u 2 
=
Qg

1
g
 V w 1u 1  V w 2 u 2 
9. If the discharge at the exit is radial, then Vw2 = 0 and hence
Work done per unit weight = 1  V u 
g
10. . Hydraulic efficiency =
R .P .
W .P .

w1
1
 Q  V w 1u 1  V w 2 u 2 
 gQH

1
gH
 V w 1u 1  V w 2 u 2 
11. If the discharge at the exit is radial, then Vw2 = 0 and hence
Hydraulic efficiency = 1  V u 
gH
w1
1
The Francis Installation
Working diagram Hydro electric power plant.`
Axial flow (Kaplan) Turbine (Reaction)