BLOW UP
TURBO MACHINERY
Turbo means spinning or whirling around. Turbo
machinery, in mechanical engineering, describes
machines that
transfer fluid energy to
a rotating wheel, including both turbines and compressors. While a
turbine transfers energy from a fluid to a rotor and compressor transfers
energy from a rotor to a fluid. The two types of machines are governed by the
same basic relationships including Newton's second Law of Motion and Euler's
energy equation for compressible fluids.
Centrifugal
pumps are also turbo machines that transfer energy from a rotor to a fluid,
usually a liquid, while turbines and compressors usually work with a gas.
UNIT1
ENERGY TRANSFER IN TURBO MACHINES
FIRST LAW OF THERMODYNAMICS
The law states that if a system executes a cycle
transferring work and heat through its boundary, then the net work(W) transfer
is equivalent to the net heat(Q) transfer. Therefore,
Application of First law to turbo machines: When a
machine system executes a process, the change in stored energy of the system is
numerically equal to the net heat interactions minus the net work interaction
during the process.
E2 – E1 = Q –
W
ΔE = Q – W
Where, E represents the total internal energy. In
the absence of electric, magnetic and chemical energy, neglecting the change in
Potential Energy (PE) and Kinetic Energy (KE) for a closed system, the equation
can be written as
ΔU = Q – W=U1 –U2
Entropy ( Second law of thermodynamics) – The second law of thermodynamics states that
for a fluid undergoing a reversible adiabatic process, the entropy change is
zero. Due to the increase in entropy, the power developed by a turbine is less
than the ideal isentropic power developed. Similarly, the work input to a pump
is greater than the isentropic or ideal work input.
MOMENT OF MOMENTUM EQUATION AND EULER TURBINE
EQUATION:
According to Newton’s law of motion, the sum of all
the forces acting on a control volume in a particular direction is equal to the
rate of change of linear momentum of the fluids across the control volume.
m =
mass of the body (Kg)
V_{1}
= initial velocity of fluid (m/s)
V_{2}
= Final velocity of fluid (m/s)
This equation is a modified form of Newton’s second
law of motion. The left hand side of this equation represents the impulse
acting on the body. The Right hand side equation represents the change in
momentum of the body in the time period dt (short time interval). Hence, this
equation is known as impulse momentum equation. It is used to study the impact
of fluid jet striking a stationary or moving plate and also to study the flow
characteristics, namely the head loss in a pipe due to change in area,
hydraulic jump, etc.
EULER TURBINE EQUATION: Consider the adiabatic flow of a fluid as
shown in Fig.1 The fluid in a stream
tube enters a control volume at radius r _{i} with tangential
velocity v _{i} and exits at r _{e} with
tangential velocity v _{e}. For a compressor or pump with steady
flow, the applied torque is equal to the
change in angular momentum of the fluid, or
The input power of a general turbine is 



This equation is often referred to as the Euler
pump equation. Application of the first law of thermodynamics to
the flow through the control volume gives
Combining this expression with Eq. gives


Likewise, for a steadyflow turbine, the output
torque is equal to the change in angular momentum of the fluid, or

This equation is often referred to as the Euler
turbine equation. Application of the first law of thermodynamics
to the flow through the control volume gives
PRINCIPLES OF IMPULSE AND REACTION MACHINES: An impulse stage is one in which the static
pressure at the rotor inlet is the same as that at the rotor outlet. Then, it
is defined as one where the relative velocity of fluid flow is constant on the
rotor. These two definitions are very nearly equivalent since there is very
little pressure drop during flow through a rotor when the relative velocity is
constant. A reaction stage is one where
a change of static pressure occurs during flow over each rotor stage. The
machine containing such stages is termed as reaction machine.
Figure 2 Working of Impulse and Reaction Turbine
DEGREE OF REACTION: The degree of reaction is parameter which
describes the relation between the energy transfers due to static pressure
change and energy transfer due to dynamic pressure change.
ONE DIMENSIONAL ANALYSIS: Dimensional Analysis uses our knowledge
of the systems of measuring units and the dimensions of physical quantities in
the solution of engineering problems. If we have a theory, dimensional analysis
complements it, but we can also get close to the answer without one.
Dimensional Analysis allows us to:
Convert from one system of units to another.
Check the units of an equation.
Simplify problems by reducing the number of
parameters.
Plan experiments so as to reduce the effort required
to investigate the situation under consideration.
Design and use models for experimental tests.
Correlate experimental data.
Graphically present the results of experimentation
or analysis more concisely
UNIT2
STEAM TURBINE
STEAM TURBINE;  Steam turbine is a powergenerating
machine in which the pressure energy of the fluid is converted into mechanical
energy. This conversion of energy is due to the dynamic action of steam flowing
over the blade (Figure 3).
Figure
3: Schematic Diagram of an Impuse Turbine
Figure 3:Velocity Diagram of Impulse Turbine
Compounding of impulse turbine:
This is done to reduce the rotational speed of the impulse turbine to
practical limits. (A rotor speed of 30,000 rpm is possible, which is pretty
high for practical uses.)  Compounding is achieved by using more than one set
of nozzles, blades, rotors, in a series, keyed to a common shaft; so that
either the steam pressure or the jet velocity is absorbed by the turbine in
stages.
Three main types of compounded impulse turbines are:
a) Pressure compounded, b)
velocity compounded and c) pressure and velocity compounded impulse turbines.
Figure
4: Variation of
Diagram/ Blade Efficiency with Speed Ratio
Blade efficiency or Diagram efficiency
or Utilization factor is given by
Diagram/Blade
Efficiency=

UTILIZATION FACTOR:  The utilization factor is the
ratio of the ideal work output to the energy available for conversion into
work.
VANE EFFICIENCY:  The ratio of the work output from
the rotor to the kinetic energy of the fluid at the inlet is called the rotor
efficiency or vane efficiency
STAGE EFFICIENCY:  It is the ratio of work done per
kg of steam to theoretical enthalpy drop in the nozzle per kg of steam.
REACTION STAGE:  A reaction stage in that stage
when pressure drops occurs in both the fixed blades and moving blades.
PARSON’S STAGE:  The reactions stage having a
degree of reaction of 50% is called Parson’s stage.
NOZZLE EFFICIENCY:  It is the actual enthalpy drop
in the nozzle to isentropic enthalpy drop in the nozzle.
MERITS OF STEAM TURBINES:
·
Ability
to utilize high pressure and high temperature steam.
·
High
component efficiency.
·
High
rotational speed.
·
High
capacity/weight ratio.
·
Smooth,
nearly vibrationfree operation.
·
No
internal lubrication.
·
Oil
free exhaust steam.
·
Can
be built in small or very large units (up to 1200 MW).
DEMERITS OF STEAM
TURBINE:
·
For
slow speed application reduction gears are required.
·
The
steam turbine cannot be made reversible.
·
The
efficiency of small simple steam turbines is poor.
LOSSES IN STEAM TURBINE
Profile loss: Due to formation of boundary layer
on blade surfaces. Profile loss is a boundary layer phenomenon and therefore
subject to factors that influence boundary layer development.
These
factors are Reynolds number, surface roughness, exit Mach number and trailing
edge thickness.
Secondary loss: Due to friction on the casing wall
and on the blade root and tip. It is a boundary boundary layer effect and
dependent dependent upon the same considerations considerations as those of
profile loss.
Tip leakage loss: Due to steam passing through the
small clearances required between t he moving tip an d casing or between the
moving blade tip and rotating shaft. The extent of leakage depends on the
whether the turbine is impulse or reaction. Due to pressure drop in moving
blades of reaction turbine they are more prone to leakages.
Disc windage loss: Due to surface friction created on
the discs of an impulse turbine as the disc rotates in steam atmosphere. The
result is the forfeiture of shaft power for an increase in kinetic energy and
heat energy of steam.
UNIT – 3
HYDRAULIC/WATER TURBINES
A
hydraulic turbine uses potential energy and kinetic energy of water and
converts it into usable mechanical energy.The mechanical energy made available
at the turbine shaft is used to run an electric power generator which is
directly coupled to the turbine shaft
The electric power which is obtained from the hydraulic energy is known
as Hydro electric energy.
CLASSIFICATION OF WATER TURBINES: 
Hydraulic turbines are classified into various kinds
according to: (i) the action of water on the blades, (ii) the direction of
fluid flew through the runner and (ii) the specific speed of the machine. Note
that the first and second categorization is similar to those of compressible
flow fluid machines.
PELTON WHEEL:  The Pelton wheel or Pelton turbine
is a tangential flow impulse turbine. The water strikes the bucket along the
tangent of the runner. The energy available at the inlet of the turbine is only
kinetic energy.
Figure 5: Pelton Turbine
Figure 6: Francis Turbine
FRANCIS TURBINE:  Francis turbines are the most
common water turbine in use today. They operate in a head range of
ten meters to six hundred and fifty meters and are primarily used for
electrical power production. The power output ranges from 10 to 750MW,
minihydro excluded. Runner diameters are between 1 and 10 meters. The speed
range of the turbine is from 83 to 1000 rpm. Medium size and larger Francis
turbines are most often arranged with a vertical shaft. Vertical shaft may also
be used for small size turbines, but normally they have horizontal shaft.
KAPLAN TURBINE:  The Kaplan turbine is a
propellertype water turbine which has adjustable blades. It
was developed in 1913 by the Austrian professor Viktor Kaplan, who
combined automatically adjusted propeller blades with automatically adjusted
wicket gates to achieve efficiency over a wide range of flow and water level.
DRAFT TUBES:  The simplest and most efficient,
turbine draft tube is the conical shaped draft tube. It is usually vertical and
is designed with a truncated cone similar to an inverted ice cream cone.
Originally, turbines were designed without draft tubes. In order to work on the
runner, stop logs were inserted into the tailrace training walls and the
discharge pit was pumped out.
CENTRIFUGAL PUMPS:  A centrifugal pump is a rotodynamic
pump that uses a rotating impeller to create
flow by the addition of energy to a fluid. Centrifugal pumps are commonly used
to move liquids through piping. The fluid enters the pump impeller along or
near to the rotating axis and is accelerated by the impeller, flowing radially
outward into a diffuser or volute chamber (casing), from
where it exits into the downstream piping. Centrifugal pumps are used for large
discharge through smaller heads.
CLASSIFICATION OF CENTRIFUGAL PUMPS:  The centrifugal
or rotodynamic pump produce a head and a flow by increasing the
velocity of the liquid through the machine with the help of a rotating vane
impeller. Centrifugal pumps include radial, axial and mixed flow units.
POSITIVE DISPLACEMENT PUMPS:  The positive
displacement pump operates by alternating of filling a cavity and
then displacing a given volume of liquid. The positive displacement pump
delivers a constant volume of liquid for each cycle against varying discharge pressure or
head.
GROSS HEAD:  The difference between the head race
level and tail race level when no water is flowing is known as Gross Head.
Gross Head . It is denoted by ‘H_{g}’ .
NET HEAD:  The net head or the effective head is
the difference in levels between the headrace and the turbine inlet.
MANOMETRIC HEAD :
This is defined by British Standards as the sum of the actual lift (H) +
the friction losses in the pipes + the discharge velocity head. However for
special pumps allowance must also be made for the velocity of flow towards the
suction intake and any pressure differences at the water surfaces in the supply
and receiving tanks. Thus
Commonly the suction and delivery pipes are of equal
diameter.
Figure 7:
Vector Diagram
Work Done Theory
The total energy at outlet = Total energy at input +
Work done  Losses
or
MECHANICAL EFFICIENCY:  The ratio of the power
available at the impeller to the power at the shaft of the centrifugal pump is
known as mechanical efficiency.
OVERALL EFFICIENCY:  It is defined as ratio of
power output of the pump to the power input to the pump. The power output of
the pump in kW.
CAVITATION:  Cavitation is the formation of empty
cavities in a liquid by high forces and the immediate implosion of them. (A
liquid is a continuum and repairs itself if it is torn apart.) Cavitation
occurs when a liquid is subjected to rapid changes of pressure causing the formation
of cavities in the lower pressure regions of the liquid. Cavitations is a
significant cause of wear in some engineering contexts – when entering high
pressure areas these bubbles collapse on a metal surface continuously, causing
cyclic stressing of the metal surface. This result in surface fatigue of the
metal causing a type of wear called cavitations.
UNIT4
ROTARY FANS, BLOWERS, AND COMPRESSORS
The rotodynamic machine is called
a fan when the primary concern is to increase the kinetic energy of the fluid
and all other forms of energy are small or negligible. For example, in a
domestic ceiling fan the comfort by the air velocity is of primary interest.
The machine is termed as blower if the rise in fluid energy both kinetic and
static pressure are important. An example is a blower supply air to an air
conditioning duct, providing a rise in pressure to overcome various flow
resistances and also to provide necessary velocity to the airflow. More often,
the velocity of flow is small enough to consider the flow in the fans and
blower to be incompressible and the density of fluid is taken as a constant
value.
In a compressor, in addition to
increase in kinetic energy and pressure, increase of internal energy is also
significant. Thus, change in enthalpy (internal energy + flow work) is of
interest for the compressor. The pressure rise is quite high in compressor; the
change in pressure is usually expressed by pressure ratio. The density
variations of fluid flow are significant; the flow is considered as
compressible flow in the compressors.
ROTARY FAN:  A fan is a machine used to
create flow within a fluid, typically a gas such as air. A fan consists of a rotating arrangement of
vanes or blades which act on the air. Usually, it is contained within some form
of housing or case. This may direct the airflow or increase safety by
preventing objects from contacting the fan blades. Most fans are powered by electric motors,
but other sources of power may be used, including hydraulic motors and
internal combustion engines and solar power.
CENTRIFUGAL BLOWERS : Blowers can achieve much higher pressures
than fans, as high as 1.20 kg/cm^{2}. They are also used to produce
negative pressures for industrial vacuum systems. Major types are: centrifugal
blower and positivedisplacement blower. Centrifugal blowers look more like
centrifugal pumps than fans. The impeller is typically geardriven and rotates
as fast as 15,000 rpm. In multistage blowers, air is accelerated as it passes
through each impeller. In singlestage blower, air does not take many turns,
and hence it is more efficient. Centrifugal blowers typically operate against
pressures of 0.35 to 0.70 kg/cm^{2}, but can achieve higher pressures.
One characteristic is that airflow tends to drop drastically system pressure.
Equipment

Pressure Ratio

Pressure rise (mm H_{2}O)

Fans

Up to 1.1

1136

Blowers

1.1 to 1.2

11362066

FAN LAWS:
The fans operate under a predictable set of laws concerning speed, power
and pressure. A change in speed (RPM) of any fan will predictably change the
pressure rise and power necessary to operate it at the new RPM.
Figure 8: Centrifugal Fan Blades
CENTRIFUGAL COMPRESSOR : Centrifugal compressors increase the kinetic
energy of the gas with a highspeed impeller and then convert this energy into
increased pressure in a divergent outlet passage called the diffuser.
Centrifugal compressors are particularly suited for compressing large volumes
of gas to moderate pressures. In axial compressors the gas flows parallel to
the axis of rotation of the rotor.
IMPELLER:
An impeller is a rotor inside a tube or conduit used to increase the
pressure and flow of a fluid.
DIFFUSER: 
The diffuser pump is a kind
of radial flow centrifugal pump that differentiates itself from other
centrifugal pumps by the fact that it encompasses a ring of fixed vanes. After
leaving the impeller, the fluid is passed through these vanes and diffused. In
this way, a more controlled flow is obtained and the efficiency of the
conversion of velocity head into pressure head is increased.
AXIAL FLOW COMPRESSORS:  Axial compressors are
rotating, airfoil based compressors in which
the working fluid principally flows parallel to the axis of rotation. This is
in contrast with other rotating compressors such as centrifugal, axicentrifugal
and mixedflow compressors where the air may enter axially but will have a
significant radial component on exit.
VELOCITY DIAGRAMS The blade
rows are designed at the first level using velocity diagrams. A velocity
diagram shows the relative velocities of the blade rows and the fluid. The
axial flow through the compressor is kept as close as possible to Mach 1 to
maximize the thrust for a given compressor size. The tangential Mach number
determines the attainable pressure rise. The blade rows turn the flow through
an angle β; larger turning allows a higher temperature ratio, but requires
higher solidity. Modern blades rows have low aspect ratios and high solidity.
SURGE is the point at
which the compressor cannot add enough energy to overcome the system resistance
or back pressure.
ADIABATIC EFFICIENCY:  The
ratio of the isentropic work to the actual work is called the adiabatic
efficiency (or isentropic efficiency).
POLYTROPIC EFFICIENCY:  The
polytrophic efficiency is defined as the ratio of polytrophic work to actual
work.
UNIT5
POWER TRANSMITTING TURBO MACHINES
FLUID COUPLING:
A fluid coupling is a hydrodynamic device
used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a
mechanical clutch. It also
has widespread application in marine and industrial machine drives, where
variable speed operation and/or controlled startup without shock loading of
the power transmission system is essential.
TORQUE CONVERTOR : A torque converter is generally a fluid
coupling that is used to transfer rotating power from a prime mover, such as
an internal combustion engine or electric
motor, to a rotating driven load. Like a basic fluid coupling, the torque
converter normally takes the place of a mechanical clutch, allowing
the load to be separated from the power source.
POSITIVE DISPLACEMENT PUMPS : A positive displacement pump causes a fluid
to move by trapping a fixed amount of it then forcing (displacing) that trapped
volume into the discharge pipe. A positive displacement pump has an expanding
cavity on the suction side and a decreasing cavity on the discharge side.
Liquid flows into the pump as the cavity on the suction side expands and the
liquid flows out of the discharge as the cavity collapses. The volume is
constant given each cycle of operation. A positive displacement pump can be
further classified according to the mechanism used to move the fluid.
HYDROSTATIC SYSTEMS: Hydrostatic systems take the mechanical
rotary output of an engine or electric motor and convert it to a hydraulic
source of power using a hydraulic pump. The hydraulic power is converted back
to mechanical power using a hydraulic motor.
HYDRAULIC INTENSIFIER:  A hydraulic intensifier is
a hydraulic machine for transforming hydraulic
power at low pressure into a reduced volume at higher
pressure.
HYDRAULIC ACCUMULATOR : A hydraulic accumulator is
an energy storage device. It is a pressure storage
reservoir in which a noncompressible hydraulic
fluid is held under pressure by an external source.
HYDRAULIC PRESS:A hydraulic press is a machine (see
machine press) using a hydraulic cylinder to generate a compressive
force.
CRANE :a type of machine used for lifting,
generally equipped with a hoist
(device) or winder (also
called a wire rope drum), wire ropes or chains and sheaves, that can be used both to lift and
lower materials and to move them horizontally. It uses one or more simple
machines like a hoist to create mechanical advantage and thus
move loads beyond the normal capability of a human.
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