Short Notes: Hydraulic Turbines & Hydro Machines | Short Notes for Mechanical Engineering PDF Download

 Page 1


Hydraulic Turbines and Hydro Machines 
Hydraulic Turbines and Hydro Machines is the section of Fluid Mechanics which 
deals with topics such as Turbines, pumps and their working. This section includes 
all the aspects regarding application of fluid mechanics in the real world.
H y d r a u lic M a c h in e s
• 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.
In a Hydroelectric plant as shown above
Page 2


Hydraulic Turbines and Hydro Machines 
Hydraulic Turbines and Hydro Machines is the section of Fluid Mechanics which 
deals with topics such as Turbines, pumps and their working. This section includes 
all the aspects regarding application of fluid mechanics in the real world.
H y d r a u lic M a c h in e s
• 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.
In a Hydroelectric plant as shown above
• A Dam constructed across a river or a channel to store water. The reservoir id 
also known as Headrace.
• Pipes of large diameter called Penstocks which carry water under pressure 
from the storage reservoir to the turbines. These pipes are usually made of 
steel or reinforced concrete.
• Turbines having different types of vanes or buckets or blades mounted on a 
wheel called a runner.
• Tailrace which is a channel carrying water away from the turbine after the 
water has worked on the turbines. The water surface in the tailrace is also 
referred to as tailrace.
Important Terms
• Gross Head (Hg ): It is the vertical difference between headrace and tailrace.
• Net Head (H): Net head or effective head is the actual head available at the 
inlet of the to work on the turbine.
H = Hg-hL
Where h L is the total head loss during the transit of water from the headrace to 
tailrace which is mainly head loss due to friction and is given by, 
hf = 4 f LV 2 / 2 g d
Where f is the coefficient of friction of penstock depending on the type of material 
of penstock L is the total length of penstock V is the mean flow velocity of water 
through the penstock D is the diameter of penstock and g is the acceleration due to 
gravity.
Types of Efficiencies
Depending on the considerations of input and output, the efficiencies can be 
classified as: •
• Hydraulic Efficiency^/,)
° It is the ratio of the power developed by the runner of a turbine to the 
power supplied at the inlet Inlet of the turbine of a turbine.
° Since the power supplied is hydraulic, and the probable loss is between 
the striking jet and vane it is rightly called hydraulic efficiency.
° If R .P . is the Runner Power and W .P. is the Water Power, /? /, = R.P/W.P.
• Mechanical Efficiency(/7m )
° It is the ratio of the power available at the shaft to the power developed 
by the runner of a turbine.
° This depends on the slips and other mechanical problems that will 
create a loss of energy between the runner in the annular area between 
the nozzle and spear
° The amount of water reduces as the spear is pushed forward and vice - 
versa and shaft which is purely mechanical and hence mechanical 
efficiency.
° If S.P . is the Shaft Power, r)m = S.P/R.P.
• Overall Efficiency^)
° It is the ratio of the power available at the shaft to the power supplied to 
the inlet of a turbine.
Page 3


Hydraulic Turbines and Hydro Machines 
Hydraulic Turbines and Hydro Machines is the section of Fluid Mechanics which 
deals with topics such as Turbines, pumps and their working. This section includes 
all the aspects regarding application of fluid mechanics in the real world.
H y d r a u lic M a c h in e s
• 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.
In a Hydroelectric plant as shown above
• A Dam constructed across a river or a channel to store water. The reservoir id 
also known as Headrace.
• Pipes of large diameter called Penstocks which carry water under pressure 
from the storage reservoir to the turbines. These pipes are usually made of 
steel or reinforced concrete.
• Turbines having different types of vanes or buckets or blades mounted on a 
wheel called a runner.
• Tailrace which is a channel carrying water away from the turbine after the 
water has worked on the turbines. The water surface in the tailrace is also 
referred to as tailrace.
Important Terms
• Gross Head (Hg ): It is the vertical difference between headrace and tailrace.
• Net Head (H): Net head or effective head is the actual head available at the 
inlet of the to work on the turbine.
H = Hg-hL
Where h L is the total head loss during the transit of water from the headrace to 
tailrace which is mainly head loss due to friction and is given by, 
hf = 4 f LV 2 / 2 g d
Where f is the coefficient of friction of penstock depending on the type of material 
of penstock L is the total length of penstock V is the mean flow velocity of water 
through the penstock D is the diameter of penstock and g is the acceleration due to 
gravity.
Types of Efficiencies
Depending on the considerations of input and output, the efficiencies can be 
classified as: •
• Hydraulic Efficiency^/,)
° It is the ratio of the power developed by the runner of a turbine to the 
power supplied at the inlet Inlet of the turbine of a turbine.
° Since the power supplied is hydraulic, and the probable loss is between 
the striking jet and vane it is rightly called hydraulic efficiency.
° If R .P . is the Runner Power and W .P. is the Water Power, /? /, = R.P/W.P.
• Mechanical Efficiency(/7m )
° It is the ratio of the power available at the shaft to the power developed 
by the runner of a turbine.
° This depends on the slips and other mechanical problems that will 
create a loss of energy between the runner in the annular area between 
the nozzle and spear
° The amount of water reduces as the spear is pushed forward and vice - 
versa and shaft which is purely mechanical and hence mechanical 
efficiency.
° If S.P . is the Shaft Power, r)m = S.P/R.P.
• Overall Efficiency^)
° It is the ratio of the power available at the shaft to the power supplied to 
the inlet of a turbine.
° As this covers overall problems of losses in energy, it is known as overall 
efficiency.
° This depends on both the hydraulic losses and the slips and other 
mechanical problems that will create a loss of energy between the jet 
power supplied and the power generated at the shaft available for 
coupling of the generator.
n = nhxnm = r.p/ w.p x s.p/ r.p
• Volumetric Efficiency
Vol. efficiency
Volume of water actually stricking the runner 
Volume of water supplied to the turbine
C la s s ific a tio n o f T u rb in e s
• The hydraulic turbines can be classified based on the type of energy at the 
inlet, the direction of flow through the vanes, head available at the inlet, 
discharge through the vanes and specific speed.
• They are classified as:
Turbine Type of
Head Discharge
Direction Specific
Name type energy
of flow Speed
Pelton
Wheel
Impulse Kinetic
High 
Head > 
250m to 
1000m
Low
Tangential 
to runner
Low
<35 Single jet 
35 - 60 Multiple jet
Francis
Turbine
Medium
Medium
Radial flow Medium
Reaction Kinetic -
60 m to
ISO in
Mixed Flow
60 to 300
Kaplan
Turbine
Turbine Pressure
Low
< 30 m
High
Axial Flow
High
300 to 1000
• P e lto n T u rb in e
~W
Page 4


Hydraulic Turbines and Hydro Machines 
Hydraulic Turbines and Hydro Machines is the section of Fluid Mechanics which 
deals with topics such as Turbines, pumps and their working. This section includes 
all the aspects regarding application of fluid mechanics in the real world.
H y d r a u lic M a c h in e s
• 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.
In a Hydroelectric plant as shown above
• A Dam constructed across a river or a channel to store water. The reservoir id 
also known as Headrace.
• Pipes of large diameter called Penstocks which carry water under pressure 
from the storage reservoir to the turbines. These pipes are usually made of 
steel or reinforced concrete.
• Turbines having different types of vanes or buckets or blades mounted on a 
wheel called a runner.
• Tailrace which is a channel carrying water away from the turbine after the 
water has worked on the turbines. The water surface in the tailrace is also 
referred to as tailrace.
Important Terms
• Gross Head (Hg ): It is the vertical difference between headrace and tailrace.
• Net Head (H): Net head or effective head is the actual head available at the 
inlet of the to work on the turbine.
H = Hg-hL
Where h L is the total head loss during the transit of water from the headrace to 
tailrace which is mainly head loss due to friction and is given by, 
hf = 4 f LV 2 / 2 g d
Where f is the coefficient of friction of penstock depending on the type of material 
of penstock L is the total length of penstock V is the mean flow velocity of water 
through the penstock D is the diameter of penstock and g is the acceleration due to 
gravity.
Types of Efficiencies
Depending on the considerations of input and output, the efficiencies can be 
classified as: •
• Hydraulic Efficiency^/,)
° It is the ratio of the power developed by the runner of a turbine to the 
power supplied at the inlet Inlet of the turbine of a turbine.
° Since the power supplied is hydraulic, and the probable loss is between 
the striking jet and vane it is rightly called hydraulic efficiency.
° If R .P . is the Runner Power and W .P. is the Water Power, /? /, = R.P/W.P.
• Mechanical Efficiency(/7m )
° It is the ratio of the power available at the shaft to the power developed 
by the runner of a turbine.
° This depends on the slips and other mechanical problems that will 
create a loss of energy between the runner in the annular area between 
the nozzle and spear
° The amount of water reduces as the spear is pushed forward and vice - 
versa and shaft which is purely mechanical and hence mechanical 
efficiency.
° If S.P . is the Shaft Power, r)m = S.P/R.P.
• Overall Efficiency^)
° It is the ratio of the power available at the shaft to the power supplied to 
the inlet of a turbine.
° As this covers overall problems of losses in energy, it is known as overall 
efficiency.
° This depends on both the hydraulic losses and the slips and other 
mechanical problems that will create a loss of energy between the jet 
power supplied and the power generated at the shaft available for 
coupling of the generator.
n = nhxnm = r.p/ w.p x s.p/ r.p
• Volumetric Efficiency
Vol. efficiency
Volume of water actually stricking the runner 
Volume of water supplied to the turbine
C la s s ific a tio n o f T u rb in e s
• The hydraulic turbines can be classified based on the type of energy at the 
inlet, the direction of flow through the vanes, head available at the inlet, 
discharge through the vanes and specific speed.
• They are classified as:
Turbine Type of
Head Discharge
Direction Specific
Name type energy
of flow Speed
Pelton
Wheel
Impulse Kinetic
High 
Head > 
250m to 
1000m
Low
Tangential 
to runner
Low
<35 Single jet 
35 - 60 Multiple jet
Francis
Turbine
Medium
Medium
Radial flow Medium
Reaction Kinetic -
60 m to
ISO in
Mixed Flow
60 to 300
Kaplan
Turbine
Turbine Pressure
Low
< 30 m
High
Axial Flow
High
300 to 1000
• P e lto n T u rb in e
~W
u= wheel velocity, V= Jet velocity, Vr= relative velocity, Vw=whirl velocity, <p=Angle b |y 
relative velocity at outlet and (3 = Guide blade angle at outlet 
U i=u2=u=2t tN/60 where N= no. of rotation of wheel 
Tangential flow Impulse turbine
components 1) Nozzle 2) Runner and buckets 3) Casing 4) Breaking Jet
Power given to pelton turbine = paVt(Vw ± VW i > )u Nm/s
Hydraullic e f f .
_______ Runner Power_______
Water Power ( K . E o f water)
p a V y f V ^ V ^ u
f>aV*
Max hydraullic e f f . ri
J 'm ax
1 + Cos4>
when u = ¦
V,
Point to Remember:-
• The velocity of jet Vi=Cv*V(2gH) where Cv=0.98 to 0.99 and called coefficient 
of velocity
• The velocity of wheel u= 0 V(2gH) where 0 = Speed ratio (u/Vi) (0.43 to 0.48)
• The velocity of wheel u= ttDN (Rps)
• Jet ratio m=D/d (ratio of pitch diameter to jet diameter and usually 12 in most 
cases)
• Number of bucket Z= 15+(D/2d) = 15+0.5m
• Number of jets = total flow rate/ Rate of flow by single jet
Radial Flow Reaction Turbine:-
Page 5


Hydraulic Turbines and Hydro Machines 
Hydraulic Turbines and Hydro Machines is the section of Fluid Mechanics which 
deals with topics such as Turbines, pumps and their working. This section includes 
all the aspects regarding application of fluid mechanics in the real world.
H y d r a u lic M a c h in e s
• 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.
In a Hydroelectric plant as shown above
• A Dam constructed across a river or a channel to store water. The reservoir id 
also known as Headrace.
• Pipes of large diameter called Penstocks which carry water under pressure 
from the storage reservoir to the turbines. These pipes are usually made of 
steel or reinforced concrete.
• Turbines having different types of vanes or buckets or blades mounted on a 
wheel called a runner.
• Tailrace which is a channel carrying water away from the turbine after the 
water has worked on the turbines. The water surface in the tailrace is also 
referred to as tailrace.
Important Terms
• Gross Head (Hg ): It is the vertical difference between headrace and tailrace.
• Net Head (H): Net head or effective head is the actual head available at the 
inlet of the to work on the turbine.
H = Hg-hL
Where h L is the total head loss during the transit of water from the headrace to 
tailrace which is mainly head loss due to friction and is given by, 
hf = 4 f LV 2 / 2 g d
Where f is the coefficient of friction of penstock depending on the type of material 
of penstock L is the total length of penstock V is the mean flow velocity of water 
through the penstock D is the diameter of penstock and g is the acceleration due to 
gravity.
Types of Efficiencies
Depending on the considerations of input and output, the efficiencies can be 
classified as: •
• Hydraulic Efficiency^/,)
° It is the ratio of the power developed by the runner of a turbine to the 
power supplied at the inlet Inlet of the turbine of a turbine.
° Since the power supplied is hydraulic, and the probable loss is between 
the striking jet and vane it is rightly called hydraulic efficiency.
° If R .P . is the Runner Power and W .P. is the Water Power, /? /, = R.P/W.P.
• Mechanical Efficiency(/7m )
° It is the ratio of the power available at the shaft to the power developed 
by the runner of a turbine.
° This depends on the slips and other mechanical problems that will 
create a loss of energy between the runner in the annular area between 
the nozzle and spear
° The amount of water reduces as the spear is pushed forward and vice - 
versa and shaft which is purely mechanical and hence mechanical 
efficiency.
° If S.P . is the Shaft Power, r)m = S.P/R.P.
• Overall Efficiency^)
° It is the ratio of the power available at the shaft to the power supplied to 
the inlet of a turbine.
° As this covers overall problems of losses in energy, it is known as overall 
efficiency.
° This depends on both the hydraulic losses and the slips and other 
mechanical problems that will create a loss of energy between the jet 
power supplied and the power generated at the shaft available for 
coupling of the generator.
n = nhxnm = r.p/ w.p x s.p/ r.p
• Volumetric Efficiency
Vol. efficiency
Volume of water actually stricking the runner 
Volume of water supplied to the turbine
C la s s ific a tio n o f T u rb in e s
• The hydraulic turbines can be classified based on the type of energy at the 
inlet, the direction of flow through the vanes, head available at the inlet, 
discharge through the vanes and specific speed.
• They are classified as:
Turbine Type of
Head Discharge
Direction Specific
Name type energy
of flow Speed
Pelton
Wheel
Impulse Kinetic
High 
Head > 
250m to 
1000m
Low
Tangential 
to runner
Low
<35 Single jet 
35 - 60 Multiple jet
Francis
Turbine
Medium
Medium
Radial flow Medium
Reaction Kinetic -
60 m to
ISO in
Mixed Flow
60 to 300
Kaplan
Turbine
Turbine Pressure
Low
< 30 m
High
Axial Flow
High
300 to 1000
• P e lto n T u rb in e
~W
u= wheel velocity, V= Jet velocity, Vr= relative velocity, Vw=whirl velocity, <p=Angle b |y 
relative velocity at outlet and (3 = Guide blade angle at outlet 
U i=u2=u=2t tN/60 where N= no. of rotation of wheel 
Tangential flow Impulse turbine
components 1) Nozzle 2) Runner and buckets 3) Casing 4) Breaking Jet
Power given to pelton turbine = paVt(Vw ± VW i > )u Nm/s
Hydraullic e f f .
_______ Runner Power_______
Water Power ( K . E o f water)
p a V y f V ^ V ^ u
f>aV*
Max hydraullic e f f . ri
J 'm ax
1 + Cos4>
when u = ¦
V,
Point to Remember:-
• The velocity of jet Vi=Cv*V(2gH) where Cv=0.98 to 0.99 and called coefficient 
of velocity
• The velocity of wheel u= 0 V(2gH) where 0 = Speed ratio (u/Vi) (0.43 to 0.48)
• The velocity of wheel u= ttDN (Rps)
• Jet ratio m=D/d (ratio of pitch diameter to jet diameter and usually 12 in most 
cases)
• Number of bucket Z= 15+(D/2d) = 15+0.5m
• Number of jets = total flow rate/ Rate of flow by single jet
Radial Flow Reaction Turbine:-
U,
V e lo c ity tria n g le
A t in le t tria n g le :
U i = v e lo c ity o f th e b la d e 
a t in le t
V i = a b s o lu te v e lo c ity o f 
e n te rin g w a te r
VTl = re la tiv e v e lo c ity o f 
e n te rin g w a te r
V r = v e lo c ity o f flo w a t 
in le t
a x = g u id e b la d e a n g le 
= v a n e a n g le
A t o u tle t tria n g le :
U 2 = v e lo c ity o f th e
b la d e a t o u tle t
Vr = re la tiv e v e lo c ity o f
le a v in g w a te r
Vf2 — V2 = v e lo c ity o f
flo w a t o u tle t
a 2 = g u id e b la d e a n g le
P 2 = v a n e a n g le
I S
Work Done/sec = paVjjV^Uj ± Vw2u2J = pQjV^Uj i V ^u,J 
t t DjN t t D0N
u' = _ ^ (rp,n)' ,,2= _ i r (r|>m)
If a2 =90°, V ^ O 
so work done /sec =paV1(V[0lu1 )
Degree of Reaction (R):-
^ Change of pressure energy inside the runner 
Change in total energy inlet
• For Pelton turbine R=0 
Draft Tube:-
A draft tube is a pipe of a gradually increasing area which connects the outlet of 
the runner to the tailrace and is used to discharge water from the turbine exit to the 
tailrace. One end of the draft tube is connected to the outlet of the runner while the 
other end is submerged below the level of water in the tailrace.
Functions:
• It permits a negative head to be established to be established at the outlet of 
the runner and thereby increasing the NET HEAD on the turbine.
• It converts a large proportion of kinetic energy which was being rejected at 
the outlet if the turbine into useful pressure energy.
Specific Speed:-
The specific speed value for a turbine is the speed of a geometrically 
similar turbine which would produce unit power (one kilowatt) under unit head (one 
meter). The specific speed of a turbine is given by the manufacturer (along with 
other ratings) and will always refer to the point of maximum efficiency.