Thermal and Hydraulic Machines as per AKTU

1. Simple Rankine cycle
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2. The main components of steam power plant are
i. BOILER
ii. TURBINE
iii. CONDENSER
iv. COOLING TOWER
v. PUMP .
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3. From graph
1-2 = isentropic process
2-3 = isobaric process
3-4 = isentropic process
4-1 = isobaric process .
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4. Boiler :-
Boiler is used to produce steam .
Heat energy produced by coal is used to produce steam.
Water is allowed to heat until it becomes into vapor state.
Vapor is sent into turbine.
TURBINE :-
Turbine produces the work.
Work produced is used to run the generator.
The enthalpies at the enter and exit of the turbine are different.
Then Vapor is sent into the condenser.
CONDENSER :-
The vapor is condensed to water in the condenser and sent into the pump.
PUMP :-
Pump send the water again into the Boiler and the cycle repeats again.
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5. By considering the devices as steady flow devices and by applying the energy
balance we get
Steam turbine :
W turbine = h1 - h2
Condenser :-
Q rejected = h2 – h3
Pump :-
W pump = h4 – h3
Boiler :-
Q added = h1 – h4
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6.  Turbine produces the more work if the water is heated to super heated region.
 If the water is heated to super heated then the turbine will produce the more
work .
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7.  But there is a problem if water is heated to super heated i.e. when it is condensed the
vapor is not converted into water completely . It remains still as a mixture.
 It is difficult for the pump to handle both liquid and water which leads to CAVITATION
.
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8. INTRODUCTION What is IC Engine?
An internal combustion engine is a thermal system (power plant) that
converts heat obtained from chemical energy sources (gasoline, natural gas)
into mechanical work.
Where are IC Engines Used?
IC engines are used as the propulsion systems for land transport vehicles
such as automobiles (cars, etc.), marine vehicles (boats, etc.) and small
airplanes. IC engines are also used in portable electrical generators and as
prime mover in grass cutting machine, etc.
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Basic Components of IC Engines
• Cylinder, piston, inlet valve and exhaust
valve.
• Piston moves from the top dead center
(TDC) to the bottom dead center (BDC).
• Clearance volume, Vc is a spacing
between the top of the piston and the
valve’s heads when the piston is at the end
of the delivery stroke.
• Swept volume or displacement volume,
Vs is the volume between TDC and BDC.

10. Classifications:
Internal Combustion Engines (IC Engines)
External Combustion Engines (EC Engines)
Internal Combustion Engines (IC Engines):
IC Engines are those in which combustion of fuels take places inside engine
cylinder (Example: Petrol, Diesel, GAS)
External Combustion Engines (EC Engines):
EC Engines are those in which combustion of fuels take places outside engine
cylinder (Example: Steam Engine, Steam turbine)
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11. Classification of IC Engines:
a. According to the cycle of operation
Spark ignition engines(Petrol or Constant volume or Otto cycle)
Compression ignition engines(Diesel or Constant Pressure)
b. According to the type of fuel used
Petrol, Diesel, Gas Engine.
c. According to the method of fuel
SI & CI
d. According to the Process of combustion
Otto cycle, Diesel cycle, Dual combustion cycle06/10/17 JIT 11

12. About Petrol Engine:
A petrol engine (also known as a gasoline engine in North America) is an
internal combustion engine with spark-ignition, designed to run on petrol (gasoline).
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13. Working Cycles Four Stroke Petrol Engine:
 It is also known as Otto cycle or constant volume cycle.
 Cycle of operation is completed in 4-strokes of the piston or 2 revolutions of
the crankshaft.
 Each stroke consists of 180°, of crankshaft rotation and hence a cycle
consists of 720°of crankshaft rotation.
2-stroke: 1 power stroke per 1 crankshaft rev
4-stroke: 1 power stroke per 2 crankshaft rev
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14. Principle of Operation:
The series of operations of an ideal four-stroke SI engine are as follows
Suction Stroke or charging stroke
Compression Stroke
Expansion or Power Stroke or working stroke
Exhaust Stroke
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15. Principle of Operation
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16. Principle of Operation:
Stroke Valve Position
Suction Stroke
Suction Valve open
Exhaust Valve closed
Compression Stroke Both Valves closed
Expansion or Power Stroke Both Valves closed
Exhaust Stroke
Exhaust Valve open
Suction Valve closed
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17. Working Principles of Four Stroke Diesel Engine:
Increased pressure of combustion gases acts on piston -> converted to rotary motion
Can be 2 or 4 stroke engines
2-stroke: 1 power stroke per 1 crankshaft rev
4-stroke: 1 power stroke per 2 crankshaft rev
Engine stroke:
A stroke is a single traverse of the cylinder by the piston (from TDC to BDC)
1 revolution of crankshaft = 2 strokes of piston
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18. Exhaust
Suction Compression Ign.-Combn. Expansion Exhaust
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19. Working Principles Of Four Stroke Diesel Engine:
Intake stroke
Intake valve open, exhaust valve shut
Piston travels from TDC to BDC
Air drawn in
Compression stroke
Intake and exhaust valves shut
Piston travels from BDC to TDC
Temperature and pressure of air increase
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20. Working Principles Of Four Stroke Diesel Engine:
Power stroke
Intake and exhaust valves shut
Fuel injected into cylinder and ignites
Piston forced from TDC to BDC
Exhaust stroke
Intake valve shut, exhaust valve open
Piston moves from BDC to TDC
Combustion gases expelled06/10/17 JIT 20

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Two Stroke Cycle Petrol Engine
Construction :
•A piston reciprocates inside the cylinder
•It is connected to the crankshaft by means of connecting rod and crank
•There are no valves in two stroke engines, instead of valves ports are cut
on the cylinder walls.
•There are three ports, namely inlet, exhaust and transfer ports.
•The closing and opening of the ports are obtained by the movement of
piston. The crown of piston is made in to a shape to perform this.
•A spark plug is also provided.

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Two stroke cycle Petrol Engines - Working
• The piston moves up from Bottom Dead Centre (BDC) to
Top Dead Centre (TDC)
• Both transfer and exhaust ports are covered by the piston.
• Air fuel mixture which is transferred already into the engine
cylinder is compressed by moving piston.
• The pressure and temperature increases
• at the end of compression.

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Two stroke cycle Petrol Engines - Working
First Stroke : (b) Ignition and Inductance:
• Piston almost reaches the top dead centre
•The air fuel mixture inside the cylinder is ignited by means of an
electric spark produced by a spark plug
•At the same time, the inlet port is uncovered by the plane.
•Fresh air fuel mixture enters the crankcase through the inlet port

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Two stroke cycle Petrol Engines - Working
(c)Expansion and Crankcase compression
•The burning gases expand in the cylinder
•The burning gases force the piston to move down. Thus useful work is
obtained.
•When the piston moves down, the air fuel mixture in the crankcase is
partially compressed.
This compression is known as Crank case compression.

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Two stroke cycle Petrol Engines - Working
(d) Exhaust and transfer:
•At the end of expansion, exhaust port is uncovered.
•Burnt gases escape to the atmosphere.
•Transfer port is also opened. The partially compressed air fuel mixture enters
the cylinder through the transfer port.
•The crown of the piston is made of a deflected shape. So the fresh charge
entering the cylinder is deflected upwards in the cylinder.
•Thus the escape of fresh charge along with the exhaust
gases is reduced

27. Compression
Intake and exhaust valves shut
Piston travels from BDC to TDC
Temperature and pressure of air increase
Power stroke
Intake and exhaust valves shut
Fuel injected into cylinder and ignites
Piston forced from TDC to BDC
Working Principles Of Two Stroke Diesel Engine
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28. Application Of Four stroke Cycle Engine
Used in heavy vehicles
Buses,
Lorries,
Trucks etc.,
Application Of Two stroke Cycle Engine
Used in light vehicles
Bikes,
Scooters,
Mopeds
Ship propulsion
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29. Application Of Four stroke Petrol Engine
Buses ,Trucks
Mobile electric generating sets.
Small pumping sets with side cars
Application Of Four stroke Diesel Engine
30kw-Tractors
40to 100kw – jeeps, buses and trucks
200 to 400kw-Earthmoving m/c
100 to 35000kw-Marine application
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I.C ENGINE TERMINOLGY

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standard terms used in I.C Engines are
1. Bore: Inside diameter of the cylinder is termed as Bore and it is designated by the
letter d and is usually expressed in millimeter (mm)
2. Top Dead Center (TDC): The extreme position reached by the piston at the top of
the cylinder in the vertical engine is called Top Dead center. It is also called the Inner
dead centre (IDC).
3. Bottom Dead Center (BDC): The extreme position reached by the piston at the
Bottom of the cylinder in the vertical engine is called Bottom Dead center. It is also
called the Outer dead centre (ODC).

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5. Compression ratio (r): It is the ratio of Maximum cylinder volume to the
Clearance volume.
6. Cylinder volume (v): It is the sum of swept volume and the Clearance volume.
V = Vs + Vc
7. Displacement (or)Swept volume (Vs): It is the volume of space generated by
the movement of piston from one dead center to another dead center. It is expressed
in terms of cubic centimeter (cc) and given by
VS = A * L = π * d2
* L / 4
8. Clearance Volume( Vc): It is the space in the cylinder, when the piston is at Top
Dead Center It is designated as VC and expressed in cubic centimeter (cc).

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Petrol Engines
* A petrol engine draws a mixture of
petrol and air during suction stroke.
* The carburetor is employed to mix
air and petrol in the required
proportion and to supply it to the
engine during suction stroke.
* Pressure at the end of compression
is about 10 bar.
* The charge (i.e. petrol and air
mixture) is ignited with the help of
spark plug.
Diesel Engines
* A diesel engine draws only air
during suction stroke.
*The injector or atomizer is employed
to inject the fuel at the end of
combustion stroke.
*Pressure at the end of compression is
about 35 bar.
*The fuel is injected in the form of
fine spray. The temperature of the
compressed air is sufficiently high to
ignite the fuel.

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*The maintenance cost is less.
*The thermal efficiency is
about 26%.
*Overheating trouble is more
due to low thermal efficiency.
*These are high speed engines.
*The petrol engines are
generally employed in light
duty vehicle such as scooters,
motorcycles and cars. These
are also used in aeroplanes.
* The maintenance cost is
more.
* The thermal efficiency is
about 40%.
* Overheating trouble is less
due to high thermal
efficiency.
* These are relatively low
speed engines.
* The diesel engines are
generally employed in heavy
duty vehicles like buses,
trucks, and earth moving
machines.