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Study of Hydraulic Machines
Reaction Turbines
DEPARTMENT OF CIVIL ENGINEERING
SWEDISH COLLEGE OF ENGINEERING AND TECHNOLOGY
WAH CANTT.
Department of Civil Engineering
Reaction Turbines

The other main type of energy-producing hydroturbine is
the reaction turbine, which consists of

Fixed guide vanes called stay vanes,

Adjustable guide vanes called wicket gates,

and rotating blades called runner blades
Working Mechanism
Flow enters tangentially at high pressure, is turned toward the runner
by the stay vanes as it moves along the spiral casing or volute, and
then passes through the wicket gates with a large tangential velocity
component. Momentum is exchanged between the fluid and the
runner as the runner rotates, and there is a large pressure drop.
Department of Civil Engineering
Reaction Turbines
There are two main types of reaction turbine - Francis and Kaplan.
Francis Turbine


Kaplan Turbine
Francis turbine is somewhat similar in
geometry to a centrifugal pump, but with
the flow in the opposite direction.

In contrast, the Kaplan turbine is somewhat
like an axial-flow fan running backward.

If you have ever seen a window fan start
spinning in the wrong direction when wind
blows hard into the window, you can
visualize the basic operating principle of a
Kaplan turbine.
The Francis turbine is named in honor of
James B. Francis (1815–1892), who
developed the design in the 1840s.

The Kaplan turbine is named in honor of its
inventor, Viktor Kaplan (1876–1934).
Department of Civil Engineering
Classification of Reaction Turbines
We classify reaction turbines according to the angle that the flow enters the runner.
1)
2)
If the flow enters the runner radially as in Fig., the turbine is called a Francis radial-flow turbine

Inward flow turbines: In such turbines, the water enters the runner at the outer periphery and the flows
inwards ( i.e., towards the center of the runner)

Outward flow turbines: In such turbines, the water enters at the center of the runner and then flows
outwards (i.e., towards the outer periphery of the runner)
If the flow enters the runner at some angle between radial and axial, the turbine is called a
Francis mixed-flow turbine.
Francis radial-flow turbine
Francis
mixed-flow
turbine
Department of Civil Engineering
Classification of Reaction Turbines
3)
If the flow is turned completely axially before entering the runner, the turbine is called an axialflow turbine.
The main difference between Francis
mixed-flow and propeller mixed-flow
runners is that the runners of the former
have a band that rotates with
the runner, while the runners of the latter
do not. There are two types of
propeller mixed-flow turbines: Kaplan
Turbines have adjustable pitch blades,
while propeller turbines do not.
Propeller mixed flow
Propeller axial flow
Reaction Turbines

Francis turbines are most suited for heads that lie between the high heads of Pelton wheel
turbines and the low heads of Kaplan turbines.

A typical large Francis turbine may have 16 or more runner blades and can achieve a turbine
efficiency of 90 to 95 percent.

Compared to the Pelton and Francis turbines, Kaplan turbines and propeller turbines are most
suited for low head, high volume flow rate conditions. Their efficiencies rival those of Francis turbines and may be as high as 94 percent.

In Francis’ turbine runner, the number of the blades is generally between
Francis
Radial (Centrifugal)
1. Inward flow turbine
2. Outward flow turbine
Reaction Turbines
Mixed flow
1. Kaplan
2. Propeller
Axial flow
1. Kaplan
2. Propeller
 Kaplan turbines are called double regulated because the flow rate is controlled in two
ways—by turning the wicket gates and by adjusting the pitch on the runner blades.
 Propeller turbines are nearly identical to Kaplan turbines except that the blades are
fixed (pitch is not adjustable), and the flow rate is regulated only by the wicket gates
(single regulated).
Department of Civil Engineering
Difference b/w an Impulse Turbine and
Reaction Turbine
Impulse Turbine
Reaction Turbine
1)
The entire available energy of the water is
first converted into kinetic energy.
1)
The available energy of the water is not
converted from one form to another.
2)
The water flows through the nozzles and
impinges on the buckets which are fixed to
the outer periphery of the wheel.
2)
The water is guided by guide blades to flow
over the moving vanes.
3)
The water impinges on the buckets with
kinetic energy
3)
The water glides over the moving vanes with
pressure energy.
4)
The pressure of the flowing water remains
unchanged and is equal to the atmospheric
pressure.
4)
The pressure of the flowing water is reduced
after gliding over the vanes.
Department of Civil Engineering
Difference b/w an Impulse Turbine and
Reaction Turbine
Impulse Turbine
5)
It is not essential that wheel should run full.
Moreover, there should be free access of air
between the vanes and the wheel.
6)
The water may be admitted over a part of
the circumference or over the whole
circumference of the wheel.
7)
The work is done by the change in kinetic
energy.
Reaction Turbine
5)
It is essential that the wheel should always
full and kept full of water.
6)
The water must be admitted over the whole
circumference of the wheel.
7)
The work is done partly by the change in the
velocity head but almost entirely by the
change in pressure head.
Study of Hydraulic Machines
Pumps
DEPARTMENT OF CIVIL ENGINEERING
SWEDISH COLLEGE OF ENGINEERING AND TECHNOLOGY
WAH CANTT.
Department of Civil Engineering
Pumps

The word pump is a general term for any fluid machine that adds energy to a fluid.
Some authors call pumps energy absorbing devices since energy is supplied to them,
and they transfer most of that energy to the fluid, usually via a rotating shaft.

Fluid machines may also be broadly classified as either positive-displacement
machines or dynamic machines, based on the manner in which energy transfer
occurs.

In positive-displacement machines, fluid is directed into a closed volume. Energy transfer to the
fluid is accomplished by movement of the boundary of the closed volume, causing the volume
to expand or con-tract, thereby sucking fluid in or squeezing fluid out, respectively. Your heart is a
good example of a positive-displacement pump

In dynamic machines, there is no closed volume; instead, rotating blades supply or extract
energy to or from the fluid. For pumps, these rotating blades are called impeller blades, while for
turbines, the rotating blades are called runner blades or buckets
Department of Civil Engineering
Pumps

Some fundamental parameters are used to analyze the performance of a pump. The mass
flow rate of fluid through the pump, m, is an obvious primary pump performance parameter.
For incompressible flow, it is more common to use volume flow rate rather than mass flow rate.
In the turbo-machinery industry, volume flow rate is called capacity and is simply mass flow rate
divided by fluid density,

The performance of a pump is characterized additionally by its net head H, defined as the
change in Bernoulli head between the inlet and outlet of the pump,
Department of Civil Engineering
Pumps

For the case in which a liquid is being pumped, the Bernoulli head
at the inlet is equivalent to the energy grade line at the inlet,
EGLin, obtained by aligning a Pitot probe in the center of the flow
as illustrated in Fig.

The energy grade line at the outlet EGLout is obtained in the same
manner, as also illustrated in the figure. In the general case, the
outlet of the pump may be at a different elevation than the inlet,
and its diameter and average speed may not be the same as
those at the inlet.
Department of Civil Engineering
Pumps

Net head is proportional to the useful power actually delivered to the fluid. It is traditional to call
this power the water horsepower, even if the fluid being pumped is not water, and even if the
power is not measured in units of horsepower. By dimensional reasoning, we must multiply the
net head of Eq. by mass flow rate and gravitational acceleration to obtain dimensions of
power. Thus,

All pumps suffer from irreversible losses due to friction, internal leakage, flow separation on
blade surfaces, turbulent dissipation, etc. Therefore, the mechanical energy supplied to the
pump must be larger than W water horsepower. In pump terminology, the external power
supplied to the pump is called the brake horsepower, which we abbreviate as bhp. For the
typical case of a rotating shaft supplying the brake horsepower,
where ω the rotational speed of the shaft (rad/s) and Tshaft is the torque supplied to the shaft.
Department of Civil Engineering
Efficiency of Hydraulic Machines

ηturbine is defined as the ratio of brake horsepower output
(actual turbine output shaft power) to water horsepower
(power extracted from the water flowing through the turbine)

Note that turbine efficiency ηturbine is the reciprocal of pump
efficiency ηpump, since bhp is the actual output instead of the
required input
Department of Civil Engineering

FLUID MECHANICS BY YUNUS A.
CENGEL. 2TH EDITION. (MCGRAW
HILL)(AVAILABLE IN SCET LIB.)

FLUID MECHANICS BY JOHN F.
DOUGLAS. 5TH EDITION. (PEARSON)
(AVAILABLE IN SCET LIB.)

FLUID MECHANICS BY E. JOHN
FRANZINI. 10TH EDITION. (MCGRAW
HILL) (AVAILABLE IN SCET LIB.)

A TEXT BOOK OF HYDRAULICS,
FLUID MECHANICS AND
HYDRAULIC MACHINES BY R. S.
KHURMI
Reference

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