Lab Manual - Darshan Institute of Engineering &

Lab Manual
Elements of Mechanical Engineering
(2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering and
Technology, Rajkot.
Darshan Institute of Engineering & Technology
Certificate
This is to certify that Mr./Ms.____________________________________
Enrollment No. ________________Branch_____________________________
Semester 1st & 2nd has satisfactory completed the course in the subject Elements
of Mechanical Engineering in this institute.
Date of Submission: -___ / ___ / ______
Staff in Charge
Head of Department
DARSHAN INSTITUTE OF ENGG. & TECH.
Department of Mechanical Engineering
B.E. Semester – I
Elements of Mechanical Engineering(2110006)
List of Experiments
Sr.
No.
Title
1
To understand construction and
working of various types of boilers.
2
To learn about various Boiler
Mountings & Accessories.
3
To understand construction and
working of I. C. Engines.
4
To study about engine performance
parameters.
5
To understand construction and
working of different types of pumps.
6
To understand construction and
working of different types of air
compressors.
7
Demonstration of domestic
refrigerator.
8
To understand construction, working
and applications of different types of
coupling, clutch and brake.
9
Demonstration of various types of
power transmission elements.
Date of
Date of
Performance submission
Sign
Marks
(Out of10)
EXPERIMENT-1
Objective
To understand construction and working of various types of boilers
1.1 Introduction
Steam boiler may be defined as “A closed pressure vessel in which steam is generated with
capacity exceeding 25 liters gauge pressure greater than or equal to 1 kg/cm2, and water Is
heated at 100°C or above. The steam produced may be supplied:
1) For generating power in steam Engine or steam turbines.
2) At low pressures for industrial process work in cotton mills, sugar factories, etc.
3) For producing hot water for supply of hot water and for heating the buildings in cold
weather.
1.2 Classification of Steam Boilers
1.2.1 According to relative position of water and hot gases.
Fire Tube boiler - hot gases pass through fire tubes which are surrounded by water
Water tube - water flows inside the tubes and the hot flue gases flow outside the tubes.
1.2.2 According to the axis of the shell
Vertical boiler – the axis of the shell is vertical.
Horizontal boiler – the axis of the shell is horizontal
Inclined boiler – the axis of the boilers is inclined.
1.2.3According to the method of firing
Externally fired boilers – furnace is located outside the shell.
Internally fired boilers – furnace is located inside the shell, means combustion takes place
inside the boiler shell.
1.2.4 According to the Method of Water circulation
Forced Circulation boilers - water is circulated by pumps which is driven by motor and
Natural Circulation boilers - water is circulated by natural convection currents which are
set up due to the temperature difference produced by the application of heat.
1.2.5 According to the Pressure of steam
High pressure – boilers working pressure is more than 25 bars. Example: Babcock and
Wilcox boiler
Medium pressure boilers – working pressure is 10 to 25 bars. Example: Lancashire and
locomotive boiler
Low pressure boilers – working pressure is 3.5 to 10 bars. Example: Cochran and Cornish
boiler.
1.2.6 According to the mobility of boiler
Stationary boilers – it is used for stationary plants.
Mobile boilers – it can move from one place to another.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 1
1.2.7According to the number of tubes in the boiler
Single tube boilers – they have only one fire or water tube.
Multi tube boilers – they have more than one fire or water tubes.
1.3. General terms (parts) used in Steam Boiler
1.3.1Cylindrical shell
It is made up of steel plates bent into cylindrical form and rewetted and welded together.
The ends of shell are closed by means of plates in different shapes. It should have sufficient
capacity to contain water and steam.
1.3.2 Combustion chamber
It is the space, generally below the boiler shell, meant for burning fuel in order to produce
steam from the water contained in the shell.
1.3.3 Grate
It is a platform, in the combustion chamber, upon which fuel is burnt. The grate consists of
cast iron bars which are spaced apart so that air can pass through them.
1.3.4 Furnace
It is a chamber formed by the space above grate and bellows the boiler shell in which
combustion take place. It is also called a Fire box.
1.3.5 Fire Hole
It is the hole through which coal is added to the furnace.
1.3.6 Ash Pit (ash pan)
It is the area in which the ash of burnt coal is collected.
1.3.7 Smoke chamber (smoke box)
The waste gases are collected here and then releases to the chimney and then to
atmosphere.
1.3.8 Man Hole
It is a hole provided on to the boiler shell so that a workman can go inside the boiler for
inspection.
1.3.9 Hand Holes
It is a hole provided on the shell to give to give east access for the purpose of cleaning the
water tubes or some other internal parts of boiler.
1.3.10 Mud box
It collects all impurities present in the water. It is at the bottom of the barrel or shell. These
impurities are removed time to time by help of blow off cock.
1.3.11 Steam collecting pipe
When the steam leaving the boiler, it contains certain amount of water.Antipriming pipe is
used to separate water particles from the steam and to collect dry steam from boiler.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 2
Questions:
(1) Explain Working of following boiler with neat sketch:
a) Cochran boiler
b) Babcock and Wilcox boiler
c) Lancashire boiler
(2) Give difference between fire tube (Cochran) and water tube (Babcock Wilcox) boiler.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
Page 6
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Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 7
Conclusion:
Sign
Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 8
EXPERIMENT – 2
Objective
To learn about various Boiler Mountings & Accessories
Mountings
These are the safety devices for the safe working of steam boiler and they are mounted on the
steam boiler like Water indicator valve, pressure gauge, fusible plug, etc.
Accessories
These devices are used for increasing the efficiency of boilers. They are integral parts of the
boiler and are not mounted on the boiler. They include Super heater, Economizer, etc.
2.1 List of Boiler Mountings & Accessories
According to IBR the following mountings should be fitted to the boilers’
1) Two Safety valves
2) Two water level indicators
3) A pressure gauge
4) A Steam stop valve
5) A feed check valve
6) A blow off cock
7) An attachment of inspector’s test gauge
8) A man hole
9) Mud holes or sight holes
Commonly used boiler accessories are as
1) Feed pumps
2) Injector
3) Economizer
4) Air preheater
5) Superheater
6) Steam separator
7) Steam trap
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 9
Questions:
(1) What are the purposes of mounting? Explain working of following with neat sketch.
a) Water level indicators
b) Fusible plug
c) Pressure gauge
d) Spring loaded safety valve
e) Feed check valve
(2) What are the purposes of accessories? Explain working of following with neat sketch.
a) Economiser
b) Super heater
c) Air pre-heater
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 17
Conclusion:
Sign
Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 18
EXPERIMENT - 3
Objective
To understand construction and working of I. C. Engines
3.1 Introduction
In 1876 four stroke engine based on Otto cycle was developed by a German engineer
Nikolous Otto, Which revolutionized the development of internal combustion engines and
are even used till date. Diesel engine was developed by another German engineer Rudolf
Diesel in the year 1892.
Engine refers to a device which transforms one form of energy into the other form. “Heat
engine is a modified form of engine used for transforming chemical energy of fuel into
thermal energy and subsequently for producing work."
Heat engines may be classified based on where the combustion of fuel takes place. i.e.
whether outside the working cylinder or inside the working cylinder.
(a) External Combustion Engines (E.C. Engines)
(b) Internal Combustion Engines (I.C. Engines)
3.2 Comparison of I.C. Engines and E.C. Engines
Sr.N0
1.
2.
3.
4.
5.
6.
7.
8.
I.C. Engine
Combustion of fuel takes place inside the
cylinder.
Working fluid may be Petrol, Diesel &
Various types of gases.
Require less space
Capital cost is relatively low.
Starting of this engine is easy & quick
Thermal efficiency is high.
Power developed per unit weight of these
engines is high.
Fuel cost is relatively high.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
E.C. Engine
Combustion of fuel takes place
outside the cylinder
Working fluid is steam
Require large space
Capital cost is relatively high.
Starting of this engine requires time.
Thermal Efficiency is low.
Power Developed per unit weight of
these engines is low
Fuel cost is relatively low.
Page 19
3.3 Classification of I.C. Engines
I.C. Engines may be classified according to,
a) Type of the fuel used as :
(1) Petrol engine
(2) Diesel engine
(3)Gas engine
(4) Bi-fuel engine (Two fuel engine)
b) Nature of thermodynamic cycle as :
(1) Otto cycle engine
(2) Diesel cycle engine
(3) Duel or mixed cycle engine
c) Number of strokes per cycle as :
(1) Four stroke engine
(2) Two stroke engine
d) Method of ignition as :
(1) Spark ignition engine (S.I. engine)
Mixture of air and fuel is ignited by electric spark.
(2) Compression ignition engine (C.I. engine)
The fuel is ignited as it comes in contact with hot compressed air.
e) Method of cooling as :
(1) Air cooled engine
(2) Water cooled engine
f) Speed of the engine as :
(1) Low speed
(2) Medium speed
(3) High speed
g) Number of cylinder as :
(1) Single cylinder engine
(2) Multi cylinder engine
h) Position of the cylinder as :
(1) Inline engines
(2) V – engines
(3) Radial engines
(4) Opposed cylinder engine
(5) Opposed piston engine
3.4
Engine details
The various important parts of an I.C. engine are shown in figure.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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3.4.1. Cylinder
It is the heart of the engine in which the fuel is burnt and the power is developed. Cylinder
has to withstand very high pressure and temperature because the combustion of fuel is
carried out within the cylinder. Therefore cylinder must be cooled. The inside diameter is
called bore. To prevent the wearing of the cylinder block, a sleeve will be fitted tightly in
the cylinder. The piston reciprocates inside the cylinder.
3.4.2 Cylinder head
Cylinder head covers top end of cylinder. It provides space for valve mechanism, spark
plug, fuel injector etc.
3.4.3 Piston
The piston is a close fitting hollow cylindrical plunger reciprocating inside the cylinder.
The power developed by the combustion of the fuel is transmitted by the piston to the crank
shaft through connecting rod.
3.4.4 Piston Rings
The piston rings are the metallic rings inserted into the circumferential grooves provided at
the top end of the piston. These rings maintain a gas-tight joint between the piston and the
cylinder while the piston is reciprocating in the cylinder.
3.4.5 Piston pin or Gudgeon pin
It is the pin joining small end of the connecting rod and piston. This is made of steel by
forging process.
3.4.6 Connecting Rod
It is the member connecting piston through piston pin and crank shaft through crank pin. It
converts the reciprocating motion of the piston into rotary motion of the crankshaft. It is
made of steel by forging process.
3.4.7 Crank and Crankshaft
The crank is a lever that is connected to the big end of the connecting rod by a pin joint
with its other end connected rigidly to a shaft, called crankshaft. It rotates about the axis of
the crank shaft and causes the connecting rod to oscillate.
3.4.8 Valves
Engine has both intake and exhaust type of valves which are operated by valve operating
mechanism (Refer Fig. 3.5). The valves are the device which controls the flow of the intake
and the exhaust gases to and from the engine cylinder.
3.4.9 Flywheel
It is a heavy wheel mounted on the crankshaft of the engine. It minimizes cyclic variation
in speed by storing the energy during power stroke, and same is released during other
stroke.
3.4.10 Crankcase
It is the lower part of the engine, serving as an enclosure of the crankshaft and also as a
sump for the lubricating oil.
3.4.11 Carburetor
Carburetor is used in petrol engine for proper mixing of air and petrol.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 21
3.4.12 Fuel pump
Fuel pump is used in diesel engine for increasing pressure and controlling the quantity of
fuel supplied to the injector.
3.4.13 Fuel injector
Fuel injector is used to inject diesel fuel in the form of fine atomized spray under pressure
at the end of compression stroke.
3.4.14 Spark plug
Spark plug is used in petrol engine to produce a high intensity spark for ignition of air
fuel mixture in the cylinder.
3.5 Engine Terminologies
3.5.1 Bore:
The inner diameter of the engine cylinder is called a bore.
3.5.2 Stroke:
It is the linear distance traveled by the piston when it moves from one end of the
cylinder to the other end. It is equal to twice the radius of the crank.
3.5.3 Dead Centers:
In the vertical engines, top most position of the piston is called Top Dead Centre (TDC).
When the piston is at bottom most position, it is called Bottom Dead Centre (BDC).
In horizontal engine, the extreme position of the piston near to cylinder head is called Inner
Dead Centre (I.D.C.) and the extreme position of the piston near the crank is called Outer
Dead Centre (O.D.C.).
3.5.4 Clearance Volume (Vc)
It is the volume contained between the piston top and cylinder head when the piston is at
top or inner dead centre.
3.5.5 Stroke volume (swept volume)
It is volume displaced by the piston in one stroke is known as stroke volume or swept
volume.
Let, Vs = stroke volume, L = stroke length, d = Bore
=
4
3.5.6 Compression Ratio
The ratio of total cylinder volume to clearance volume is called the compression ratio (r)
of the engine.
Total cylinder volume = Vc + Vs
Compression Ratio,
=
∴
=
+
For petrol engine r varies from 6 to 10 and for Diesel engine r varies from 14 to 20.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 22
3.5.7 Piston speed
It is average speed of piston. It is equal to 2LN, where N is speed of crank shaft in rev/sec.
∴
Where,
L = Stroke length, m
N = Speed of crank shaft, RPM
,
=
2
60
Questions:
(1) Explain Four stroke petrol engine (Spark ignition four stroke engine OR Otto four
stroke engine ) with sketch.
(2) Explain working of two stroke petrol engine with diagram.
(3) Explain working of four stroke diesel engine (compression ignition engine ) with
sketch.
(4) Give difference between petrol and diesel engine.
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Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
Page 28
Conclusion:
Sign
Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 29
EXPERIMENT - 4
Objective
To study about engine performance parameters
4.1 Indicated power
The power produced inside the engine cylinder by burning of fuel is known as Indicated
power (I.P.) of engine. It is calculated by finding the actual mean effective pressure.
,
Where,
=
a = Area of the actual indicator diagram, cm2
l = Base width of the indicator diagram, cm
s = spring value of the spring used in the indicator, N/m2/cm
4.1.1 Indicated power of a Four-stroke engine
Let,
Pm = Mean effective pressure, N/m2
L = Length of stroke, m
A = Area of cross section of the cylinder, m2
N = RPM of the engine crank shaft
n = Number of power strokes per minute
Work produced by the engine per cycle,
= [Mean force acting on the piston] X [Piston displacement in one stroke]
×
Work produced by the engine per minute,
×
.
= [Work produced by the piston per cycle] X [Number of power stroke per minute]
×
× ×
In four-stroke I.C. engines, number of power stroke per minute will be equal to half of
RPM because we get one power stroke in two revolutions of the crank shaft.
i.e.
=
⁄2
Work produced by the engine per minute,
×
( . .) =
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
× ×
2
60 × 2
Page 30
∴ . .=
60000 × 2
4.1.2 Indicated power of a two stroke I.C. engine
In two stroke I.C. engine, the number of power strokes per minute will be equal to RPM of
crank shaft
i.e. n = N
Indicated power of a two stroke I.C. engine is given by
∴ . .=
60000
4.2 Brake Power (B.P.)
It is the power available at engine crank shaft for doing useful work. It is also known as
engine output power. It is measured by dynamometer.
It can be calculated as follows:
Let,
W = Net load acting on the brake drum, N
R = Radius of the brake drum, m
N = RPM of the crank shaft
T = Resisting torque, Nm
Pmb = Brake mean effective pressure
And
∴
. .=
=
×
2
=
60000
60000
The piston connecting rod and crank are mechanical parts, moving relative to each other.
They offer resistance due to friction. Therefore a certain fraction of power is lost due to
friction of the moving parts. The amount of the power lost in friction is called friction
power. The friction power is the difference between the I.P. and B.P.
= . .− . .
4.3 Efficiencies
4.3.1 Mechanical efficiency:
It is defined as the ratio of the brake power and the indicated power. Mechanical
efficiency is indicator of losses due to friction.
=
. .
. .
4.3.2 Thermal efficiency:
It is the efficiency of conversion of the heat energy produced by the actual combustion of
the fuel into the power output of the engine. It is the ratio of work done to heat supplied by
fuel.
i)Indicated thermal efficiency = Indicated Power/ Heat supplied by fuel
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 31
. .
×
=
Where, mf = mass of fuel supplied, Kg/sec and CV = calorific value of fuel, J/kg
ii) Brake thermal efficiency = Brake Power/ Heat supplied by fuel
=
Also
. .
×
=
×
4.3.3 Relative efficiency:
It is the ratio of indicated thermal efficiency of an engine to air standard cycle efficiency
=
4.3.4 Air standard efficiency:
It is the efficiency of the thermodynamic cycle of the engine.
For petrol engine,
=1−
For diesel engine,
=1−
1
( )
1
( )
−1
( − 1)
4.3.5 Volumetric efficiency:
It is the ratio of the volume of charge/air actually sucked at atmospheric condition to
swept volume of engine. It indicates breathing capacity of the engine.
=
ℎ
∨
.
4.3.6 Specific output:
The specific output of the engine is defined as the power output per unit area.
=
. .
4.3.7 Specific fuel consumption:
Specific fuel consumption (SFC) is defined as the amount of fuel consumed by an engine
for one unit of power production. SFC is used to express the fuel efficiency of an I.C.
engine.
=
. .
⁄
ℎ
Where,
mf = Mass of fuel consumed in kg/hr and B.P. = Power produced in KW
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 32
Conclusion:
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Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 33
EXPERIMENT-5
Objective
To understand construction and working of different types of pumps
5.1 Centrifugal Pumps
A pump which employs centrifugal force for conveying liquid from one place to another is
called centrifugal pump. The centrifugal pumps are of roto dynamic type pump.
Types of centrifugal pump
(A) According to type of casing,
a. Volute or spiral casing type pump
b. Vortex or whirlpool chamber type pump
c. Diffuser type (casing with guide blades) pump
(B) According to number of stages,
a. Single stage
b. Multi-stage

Impeller in series

Impeller in parallel
5.2 Rotary pumps
Rotary pumps are positive displacement pumps. It consists of fixed casing with a rotor which
may be in the form of gears, vanes, lobes, screws, cams etc.
Centrifugal pump operates on principle of centrifugal action of rotation; the pressure is
developed by the centrifugal action of liquid while rotary pumps the pressure is developed by
positive displacement of the liquid.
Rotary pump is suitable for pumping viscous fluids like vegetable oil, lubricating oil, alcohol,
grease, tar etc.
Types of rotary pumps
There are main three types of rotary pumps as,
a. Gear pump
b. Vane pump
c. Screw pump
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 34
Questions:
(1) Explain working of single acting reciprocating pump with neat sketch.
(2) Explain working principle of centrifugal pump.
(3) Explain main parts of centrifugal pump with sketch.
(4) Why priming is required in centrifugal pump? List methods of priming and explain any one
of them.
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Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
Page 39
Conclusion:
Sign
Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 40
EXPERIMENT – 6
Objective
To understand construction and working of different types of air compressors
6.1 Introduction
“The machines which take in air or any other gas at low pressure and compress it to high
pressure are called compressors. Compressors are driven by electric motors, I.C. engines gas
turbines.”
6.2 Classification of Compressor
1) According to method of compression
 Reciprocating compressor
 Rotary Compressor
 Centrifugal compressor
(2) According to delivery pressure
 Low pressure - up to 1.1 bar
 Medium pressure - 1.1. to 8 bar
 High pressure – 8 to 10 bar
 Very high pressure - above 10bar
(3) According to principle of operation
 Positive displacement
 Rotodynamic or steady flow compressor
(4) According to the number of stages
 Single stage compressor
 Multistage compressor
(5) According to number of cylinder
 Single cylinder
 Multi cylinder
(6) According the pressure limit
 Fans - pressure ratio 1 to 1.1
 Blowers - pressure ratio 1.1 to 2.5
 Compressor - pressure ratio above 2.5
(7) According to volume of air delivered
 Low capacity - volume flow rate up to 10 m3/min
 Medium capacity - volume flow rate 10 m3/min to 300 m3/min
 High capacity: Volume flow rate above 300 m3/min.
(8) According to fluid to be compressed
 Air compressor
 Gas compressor
 Vapour compressor
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 41
Questions:
(1) What is air compressor? Give application of compressed air.
(2) Explain operation of reciprocating compressor without clearance.
(3) Explain concept of multistage reciprocating compressor.
(4) Explain Vane compressor with sketch.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Darshan Institute of Engineering & Technology
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Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 45
Conclusion:
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Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
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Page 46
EXPERIMENT – 7
Objective
Demonstration of domestic refrigerator
7.1 Introduction
Refrigeration can be defined as the method of reducing the temperature of a system below
surrounding temperature and maintaining it at the lower temperature by continuously
abstracting the heat from it.
Refrigerator is a device which removes heat from cold body and reject to hot body
(surrounding) and maintains low temperature for useful purpose. In this device, external
work is required to convey heat from cold body to hot body.
Refrigerant is a heat carrying medium which absorbs heat from space (desired to cool) and
rejects heat to outside the refrigerator (in atmosphere).
7.2 Unit of Refrigeration
It is defined as "refrigerating effect produced by melting of 1 ton of ice from and at 0°C in
24 hours."
OR
Amount of heat required to be removed in order to form one ton of ice in 24 hours from
water at temperature 0 oC.
7.3 Coefficient of Performance
It is defined as the ratio of refrigerating effect to work required for compressing the
refrigerant in the compressor. It is the reciprocal of the efficiency of a heat engine. Thus the
value of COP is always greater than unity.
7.4 Domestic Refrigerator
The refrigerator is usually specified in terms of volumetric capacity of inside cooling space.
Examples…available in capacities of 65 litres, 100 litres, 165 litres, 275Iitres,1000 litres.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 47
Domestic refrigerator
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
Page 48
Questions:
(1) Give properties of good refrigerant.
(2) Explain Vapour compression refrigeration system (VCRS) with P-H diagram.
(3) Explain Vapour absorption refrigeration system with diagram.
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology
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Elements of Mechanical Engineering (2110006)
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Conclusion:
Sign
Date
Elements of Mechanical Engineering (2110006)
Department of Mechanical Engineering
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EXPERIMENT-8
Objective
To understand construction, working and applications of different types of
coupling, clutch and brake.
8.1 Introduction
Coupling and clutches are power transmission elements. It is used for transmitting power
from one shaft to the other shaft.
A coupling is a device used to connect or couple two shafts while clutch is device which
facilitate engage and disengage of driving shaft and driven shaft whenever required even it
may rotate.
The brake is frictional device whose primary function is to control the motion of machine
member. It is used to bring machine member into rest or slow down.
8.2Couplings
Shafts are mostly available up to 7 meter length due to transport difficulty. To get a greater
length, it is necessary to joint two or more pieces of the shaft using coupling.
Purposes of Coupling used are,
1. To connect shafts of motor and generator which are manufactured separately and to
provide for disconnection for repairs.
2. To reduce the transmission of shock loads from one shaft to another.
3. To allow misalignment of the shaft or to introduce mechanical flexibility.
4. To introduce protection against overloads.
8.2.1 Types of couplings
Couplings are divided into two main groups as follows,
Rigid coupling
It is used to connect two shafts which are perfectly in axial alignment. These couplings do
not allow any relative rotation between the two shafts.
There are basic three types of rigid coupling as follows,
a. Sleeve or muff coupling
b. Clamp or split muff or compression coupling
c. Flange coupling: (1) Unprotected type (2) protected type
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8.3 Clutches
The clutch is a mechanical device used to connect or disconnect from the driving shaft at
wheel of the operator while power is transmitted from driving to driven shaft.
In automobiles, where vehicle can be stopped for a while or to change the gear, requirement
is that the driven shaft should stop but the engine should run naturally under the no load
condition. This is achieved by using clutch mounted between engine shaft and gearbox shaft
and which is operated by a lever.
Classification of Clutch
a) Friction Clutch - 1) Single plate clutch 2) Multi plate clutch 3) Cone clutch
4) Centrifugal clutch
b) Positive Contact -1) Jaw clutch
8.4 Brakes
Brake is a device by means of which an artificial frictional resistance is applied to a moving
body in order to retard or stop the motion of a body. Clutches and brakes work on the same
principle of friction but the functional difference between clutch and brake is that the clutch
connects one moving part to another moving part, whereas the brake connects one moving
part to another stationary part.
During braking process, the brake absorbs either kinetic energy or potential energy or both
by an object. In automobiles brake absorbs kinetic energy of moving vehicles. In case of
elevators and hoists brake absorb potential energy released by the objects during braking
period.
The energy absorbed by the brake is converted in the form of heat which is dissipated to the
surrounding air or water which is circulated through the passage in the brake drum.
Classification of brake
a) Block or Shoe brake
1) Single block brake 2 ) Double block brake
b) Band brake
1) Simple band brake 2) Differential band brake
c) Internal expanding shoe brake
d) Disc brake
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Questions:
(1) Give classification of coupling. Explain Oldham’s coupling with sketch.
(2) Explain Single plate clutch (Disc clutch).
(3) Explain Internal expanding shoe brake with sketch.
(4) Give the difference between clutch and brake.
(5) Explain working of Centrifugal clutch.
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Conclusion
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Date
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Department of Mechanical Engineering
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EXPERIMENT – 9
Objective
Demonstration of various types of power transmission elements
9.1 Gear drive and friction drive
In case of rope and belt drives we have seen that the velocity ratio transmitted cannot be exact
due to the slip of rope or belt on the pulley. Also due to frictional losses the efficiency of power
transmission in such drives is less. The power may be transmitted from one shaft to another by
means of mating gears with high transmission efficiency.
In early days, friction discs as shown in figure 10.1 were used for transmitting the power from
one shaft to another shaft. In such a case, the power transmission capacity depends on friction
between surfaces of two discs. Therefore, this method is not suitable for transmitting higher
power as slip occurs between the discs.
(a) Frictional disc
(b) Gear drive
In order to transmit a definite power from one shaft to another shaft to the projection on one disc
and recesses on another disc can be made which can mesh with each other. This leads to the
formation of teeth on both discs and the discs with teeth on their periphery are known as "Gears".
 Advantages
1. It is a positive drive (no slip) i.e. it transmits exact velocity ratio from one shaft to
another shaft.
2. It can transmit very large power.
3. High transmission efficiency.
4. Requires less space.
5. Reliable.
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 Disadvantages
1. Manufacturing cost of gear is high, since special tools and machinery is required for gear
manufacturing.
2. Maintenance cost of gear drive is also high due to lubrication requirements.
3. The error in cutting teeth may cause vibrations and noise during operation.
4. It requires precise alignment of shafts.
Spur gear
 Use
When the axis of two shafts are parallel to each other. These gears have teeth parallel to the
axis of the shaft.
Helical gear
 In helical gears the teeth are at some angle called helix angle with respect to axis of the shaft.
 Advantages
1. It runs quieter as compared to spur gears since the contact between teeth is gradual.
2. Transmission of load is gradual which results in low impact stresses and reduction in
noise. Thus they are used for high speed transmission.
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 Disadvantage
They induce axial thrust in one direction on the bearings.
Rack and pinion
 It is a special case of spur gear in which one gear is having infinite diameter called "Rack".
 Use
To transmit the rotary motion into reciprocating motion or vice-versa.
 Application
Lathe machine, drilling machine and measuring instrument.
Bevel gear
 Use
When power is required to be transmitted from one shaft to another shaft which are intersecting
to each other then bevel gears are used. Generally, the angle between two shafts is 90⁰.
The bevel gears are of two types,
1. Straight bevel gear
2. Spiral bevel gear
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(1) Straight bevel gears
In straight bevel gears the teeth are formed straight on the cones, and they are parallel to the axis
of the gear.
(2) Spiral bevel gears
In a spiral bevel gear, the teeth are formed at an angle with respect to its axis. The contact
between two meshing teeth is gradual and smooth from start to end, as in case of helical gears.
 Application
Automobile differential
Spiral Gears (Skew gears or Crossed helical gears)
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 Use
To transmit power from one shaft to another shaft which are non parallel and non intersecting.
For low load transmission only since they have point contact between mating teeth.
Worm and worm wheel
 Use
To transmit power from one shaft to another shaft which are non intersecting and their axes
are normally at right angles to each other.
 Application
Lathe machine to get large speed reduction.
Questions:
(1) What is belt drive? Explain types of belt drive with sketch.
(2) Give comparison between individual drive and group drive.
(3) Give classification of gear and explain any three with sketch.
(4) Give comparison between belt drive, chain drive and gear drive.
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Conclusion:
Sign
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Properties of Gases
C1 .
An air vessel contains 9 kg of air at initial pressure and temperature are 6 bar and
20˚C respectively. After heat supplied pressure of air becomes 12 bar. Take value of
characteristic gas constant is 0.287 KJ/kg K and Cv= 0.718 KJ/kg K.
Determine 1. Final temperature 2. Heat supplied 3. Work done during process 4.
Change in internal energy 5. Change in enthalpy.
ANSWERS: [1] T2 = 586 K [2] Q = 1893.366 KJ [3] W = 0 KJ [4] ∆U = 1893.366 KJ
[5] ∆H = 2650.185 KJ
T1 .
One kg of air at 450 kPa and occupying 0.25m3 is heated at constant volume until the
temperature has risen to 270˚C.
Determine (i) initial te mperature of air, (ii) final pressure, (iii) heat supplied, (iv)
change in internal energy per kg and (v) change in enthalpy during process. Take Cp =
1.005 kJ/kg-K and Cv = 0.710 kJ/kg-K.
ANSWERS: [1] 338.98 K [2] 6.4 bar [3] 144.852 KJ [4] 144.852 KJ/kg [5] 205.037
KJ
H1 .
In a vessel 9 kg of air is heated with non-flow, constant volume process that pressure
of air is increased two times that of the initial value. The initial temperature is 20˚C.
Calculate 1. Final temperature 2. Change in internal energy 3. Change in enthalpy and
4. Heat transfer 5. Work done Take R=0.287 KJ/kg K. and C v=0.718 KJ/kg K for air.
ANSWERS: [1] 586 K [2] 1893.366 KJ [3] 26650.185 KJ [4] 1893.366 KJ [5] 0 KJ
C2 .
A tank filled with 1 kg of gas at init ial pressure and volume are 5 bar and 0.20 m 3 ,
respectively. If 47 KJ heat addition to the gas then its temperature reaches 127˚C.
Take value of characteristic gas constant is 300 Nm/kg K and C p = 1.005 KJ/kg K.
Determine 1.Work done during process 2. Initial temperature 3. Change in internal
energy 4. Change in enthalpy 5. Final volume.
ANSWERS: [1] W = 0 KJ [2] T1 = 333.33 K [3] ∆U = 47.002 KJ [4] ∆H = 67.003 KJ
[5] V2 = 0.20 m3
T2 .
A cylinder vessel of 1 m diameter and 4 m length has hydrogen has at pressure of 100
Kpa and 27˚C
Determine amount of heat to be supplied so as to increased pressure to 125 Kpa. For
hydrogen Cp = 14.3005 KJ/kg K and C v= 10.183 KJ/kg K.
ANSWER: Q = 194.215 KJ
H2 .
A tank contains 3m3 of air at 25 bar absolute pressure. This air is cooled until its
pressure and temperature decrease to 15 bar and 21˚C respectively.
Determine change in internal energy, change in enthalpy and heat transfer. Take C p =
1.005 kJ/kg-K and Cv = 0.718 kJ/kg-K for air.
ANSWERS: [1] -7505.024 KJ [2] -10504.94 KJ [3] -7505.024 KJ
C3 .
5 kg of gas contains in piston cylinder assembly with initial volume, pressure and
temperature are 0.5 m3 , 8 bar and 105˚C respectively. If heating of gas at constant
pressure then its temperature becomes 270˚C. Assume value of C p = 1.005 KJ/kg K and
C v= 0.793 KJ/kg K.
Determine 1.Heat supplied during process 2. Final volume 3. Work done 4. Change in
internal energy 5. Change in enthalpy 6. Final pressure.
ANSWERS: [1] Q = 829.125 KJ [2] V2 = 0.718 m3 [3] W = 174.400 KJ [4] ∆U =
654.225 KJ [5] P2 = 8 bar
T3 .
The cylinder contains gas with initial pressure, volume, and temperatures are 0.7 Mpa,
0.14 m3 , and 15.5˚C respectively. The volume of gas increases up to 0.5 m3 after heat
added at constant pressure. Assume value of characteristic gas constant is 287 J/k g K and
C v= 0.713 KJ/kg K.
Determine 1.Final temperature, Final pressure 2. Heat supplied during process 3.
Work done 4. Change in enthalpy.
ANSWERS: [1] T2 = 1033.36 K, P2 = 700 KN/m2 [2] Q = 881.54 KJ [3] W = 252 KJ
[4] ∆H = 881.54 KJ
H3 .
The gas whose pressure, volume, and temperatures are 2.75 bar, 0.09 m 3 , and 185˚C
respectively has the state changed at constant pressure until its temperature becomes
15˚C. Take R= 0.29 KJ/kgK and C p = 1.005 KJ/kg K.
Calculate 1. Heat transferred 2. Work done during the process.
ANSWERS:[1] Q = -31.829 KJ
[2] w = -9.1867 KJ
C4 .
In an air compressor air enters with initial volume, pressure and temperatures are
0.625 m3 , 0.3 bar and 95˚C respectively. If compression occurs isothermally then
pressure after compression raises up to 0.1 MPa. Assume value of characteristic gas
constant is 287 J/kg K.
Determine 1.Mass of air 2. Final temperature 3. Heat supplied during process 4. Work
done 5. Change in internal energy 6. Change in enthalpy.
ANSWERS: [1] m = 0.1775 kg [2] T2 = 368 K [3] Q = -22.574 KJ [4] W = -22.574 KJ
[5] ∆U = 0 KJ [6] ∆H = 0 KJ
T4 .
0.45 kg of air is sucks in an air compressor with initial pressure and temperature are
20 kN/m2 and 30˚C respectively. If compression is isothermal then volume after
compression reduces up to 0.06 m3 . Assume value of characteristic gas constant is
287 J/kg K.determine 1.Final temperature 2. Init ial volume 3. Work done 4. Heat
supplied during process 5. Change in enthalpy and 6. Change in internal energy.
ANSWERS: [1] T2 = 303 K [2] V1 = 1.957 m3 [3] W = -136.36 KJ [4] Q = -136.36 KJ
[5] ∆U = 0 KJ [6] ∆H = 0 KJ
H4 .
In an air compressor air enters at 1.013 bar and 27˚C having volume 5 m3 /kg and it is
compressed to 12 bar isothermally. Determine 1. Work done 2. Heat transfer and 3.
Change in internal energy.
ANSWERS: [1] W = -1252.063 KJ [2] -1252.063 KJ [3] ∆U = 0 KJ
C5 .
Determine the work done in compressing one kg of air from a volume of 0.15 m 3 at a
pressure of 1 bar to a volume of 0.05 m3 , when the compression is (i) isothermal and
(ii) adiabatic, take γ = 1.4. Also comment on your answer.
ANSWERS: [1] W = -16.479 KJ [2] w = -20.687 KJ
T5 .
One kg of gas at 100 KN/m2 and 17˚C is compressed isothermally to a pressure of
2500 KN/m2 in a cylinder. The characteristic equation of gas is given by the equation
PV= 260T/kg where T is in degree Kelvin. Find out 1. Final temperature 2. Final
volume 3. Compression ratio 4. Change in enthalpy 5. Work done on the gas.
ANSWERS: [1] T2 = 290 K [2] V2 = 0.03016 m3 [3] r = 25 [4] 0 KJ [5] -242.703
KJ
H5 .
0.45 kg of air at a pressure of 0.2 bar and 30°C is compressed is isothermally until its
volume is 0.06 m3 . Determine the final temperature, work done & heat transferred
during process, ∆H and ∆U. Take R=287 J/Kg K.
ANSWERS: [1] 303 K [2] -136.360 KJ [3] -136.360 KJ [4] 0 KJ [5] 0 KJ
Properties of Steam
C1.
T1 .
H1 .
C2.
T2 .
Following data to be observed during test on throttling Calorimeter
Pressure in main before throttling
= 13 bar
Pressure after throttling
= 1 bar
Temperature of steam after throttling
= 135˚C
Specific heat of steam
= 2.1 kJ/kg K
Determine dryness fraction for throttling calorimeter.
ANSWER: X = 0.9818
On a test with throttling calorimeter, to determine dryness fraction of steam, a sample
is taken from main pipe at 11 bar pressure and temperature after throttling are 1 bar
and 130°C respectively. Calculate dryness fraction of steam sample. Take C p= 2.1
kJ/kg K.
ANSWER: X = 0.9797
Following data to be observed during test on throttling calorimeter
Pressure in main before throttling
= 6 bar
Pressure after throttling
= 0.1 MPa
Temperature of steam after throttling
= 122˚C
Specific heat of steam
= 2.1 kJ/kg K
Determine dryness fraction for throttling calorimeter.
ANSWER: X = 0.9841
Combined separating and throttling calorimeter is used to find out dryness fraction of
the steam.
Following readings were taken,
Main Pressure
= 12 bar abs.
Mass of water collected in separating calorimeter = 2 kg
Mass of steam condensed in throttling calorimeter = 20 kg
Temperature of steam after throttling
= 110˚C
Pressure after throttling
= 1 bar abs.
Assume Cp of steam
= 2.1 kJ/kg K
Calculate dryness fraction of steam.
ANSWER: X = 0.8698
The following information is available from test of a combined separating and
throttling calorimeter.
Pressure of steam in a steam main
= 9 bar
Pressure after throttling
= 1 bar
Temperature after throttling
= 115˚C
Mass of steam condensed after throttling
= 1.8 kg
Mass of water collected in the separator
= 0.2 kg
Calculate dryness fraction of steam in the main
ANSWER: X = 0.8713
H2 .
C3.
T3 .
H3 .
C4.
Find the quality of steam supplied in a combined separating and throttling calorimeter
as per below data available.
Initial pressure
= 10 bar
Final pressure
= 1 bar
Water separated
= 1.5 kg
Steam discharged from throttling calorimeter = 20 kg
Temperature of steam after throttling
= 120°C
ANSWER: X = 0.9033
Following data to be monitoring during test on combined separating throttling
Calorimeter
Pressure in main before throttling
= 8 bar
Temperature of steam after throttling
= 110˚C
Barometer reading
= 754 mm of Hg
Manometer reading
= 81.5 mm of Hg
Mass of steam separated
= 60 kg
Mass of moisture (water) separated
= 1.5 kg
Specific heat of steam
= 2.1 kJ/kg K
Determine dryness fraction for combined separating throttling calorimeter.
ANSWER: X = 0.9412
Following data obtained from test on combined separating and throttling calorimeter.
Pressure of steam in pipe
= 7.5 bar
Temperature of steam in throttling calorimeter
= 110°C
Pressure of steam in throttling calorimeter
= 81.5 mm Hg
Barometer reading
= 754 mm of Hg
Steam entering in to separating calorimeter
= 63 kg
Water collecting in separating calorimeter
= 1.5 kg
Calculate dryness fraction of steam entering the calorimeter.
ANSWER: X = 0.9436
Following data to be monitoring during test on combined separating throttling
Calorimeter
Mass of water separated
= 3.5 kg
Mass of steam separated
= 19 kg
Temperature of steam after throttling
= 107˚C
Pressure in main before throttling
= 15 bar
Barometer reading
= 760 mm of Hg
Manometer reading
= 5 mm of Hg
Determine dryness fraction for combined separating throttling calorimeter.
ANSWER: X = 0.8013
Determine dryness fraction of steam supplied to a separating throttling calorimeter.
Water separated in separating calorimeter
= 0.45 kg
Steam discharged from throttling calorimeter
= 7 kg
Steam pressure in a main pipe
= 1.2 MPa
Barometer reading
= 760 mm of Hg
T4 .
H4 .
C5.
T5 .
H5 .
Manometer reading
= 180 mm of Hg
Temperature of steam after throttling
= 140˚C
Take Cps of steam
= 2.1 kJ/kg K
ANSWER: X = 0.9270
Following data obtained during test on combined separating and throttling
calorimeter.
Water separated
= 2 kg
Steam discharged from throttling calorimeter
= 20.5 kg
Temperature of steam after throttling
= 110°C
Initial pressure
= 12 bar
Barometer reading
= 760 mm of Hg
Final pressure
= 5 mm of Hg
Determine the quality of steam supplied.
Take Cp of superheated steam as 2.2 kJ/kg K.
ANSWER: X = 0.8721
The following data were obtained with a separating and throttling calorimeter.
Pressure in pipe line
= 1.6 MPa Condition
after throttling
= 0.1 MPa, 120°C
Moisture collected in separating calorimeter during 5 minutes = 0.18 litre at 70°C
Steam condensed after throttling during 5 minutes = 4 kg
Determine the quality of steam in the pipeline.
ANSWER: X = 0.9213
Following data available for 5 kg of steam at different condition.
Determine 1. Enthalpy and internal energy when steam has dryness fraction 0.9 at 0.8
bar 2. Enthalpy and internal energy when steam is dry at 0.8 bar and 3. Enthalpy and
internal energy when steam is superheated at 300˚C at 20 bar.
ANSWERS: [1] Hwet = 12191.95 kJ, Uwet = 11440.63 kJ [2] Hdry = 13329 kJ, Udry =
12494.24 kJ [3] Hsup = 14905.8 kJ, Usup = 13730.6 kJ
Determine the enthalpy and internal energy of 1 kg of steam at a pressure 10
bar(abs.),(i) When dryness fraction of steam is 0.85 (ii) When steam is dry and
saturated (iii) When the steam is superheated to 300˚C. Neglect the volume of water
and take the specific heat of superheated steam as 2.1 kJ/kg K.
ANSWERS: [1] Hwet = 2474.16 kJ, Uwet = 2309.06 kJ [2] Hdry = 2776.2 KJ, Udry =
2581.9 kJ [3] Hsup = 3028.41 kJ, Usup = 2782.61 kJ
One kg of steam at pressure of 15 bar with dryness fraction of 0.06. Determine
enthalpy, specific volume and internal energy of steam.
ANSWERS: [1] H = 961.318 kJ
[2] v = 0.008984 m3/kg
[3] U = 947.842 kJ
Heat Engine
C1.
An engine working on a Carno t cycle with wo rking flu id as a gas has the max imu m
pressure and temperatures of the cycle as 30 bar and 550k respectively. the expansion and
compression ratios for the isothermal and adiabatic pro cesses are 4 and 6 respectively. The
mass of gas in the system 1 is kg. Calculate the properties o f gas at salient po ints, the work
done during the cycle and thermal efficiency. Take γ=1.4 R=0.3 KJ/kgK.
ANS WERS: [V1 = 0.055 m3 V2 = 0.22 m3 V3 = 1.32 m3 V4 = 0.33 m3 T1 = 550 K T2 =
550 K T3 = 268.55 K T4 = 268.55 K ή = 51.2%]
T1.
The Initial pressure and temperature of the air taken through a Carnot cycle are 15 bar and
270 ˚C resp ectively. F rom the init ial conditions, the air is expanded isothermally to three
times its initial volume then the cycle is completed by isothermal compression and adiabatic
comp ression. Take V3 =6V1 . Determine 1) the pressure, volume and temperature at each
corner of the cycle. 2) the thermal efficiency of the cycle 3) the work done per cycle.
ANSWERS: a) V1 = 0.105 m3 V2 = 0.315 m3 V3 = 0.63 m3 V4 = 0.21 m3 T1 = 543K T2 =
543 K T3 = 411.52 K T4 = 411.52 K P1 = 15 bar P2 = 5 bar P3 = 1.89 bar P4 = 5.67 bar b) ή =
24.21% c) W.D =41.9 KJ]
H1.
A hot air engine works on Carnot cycle with thermal efficiency of 70%.if final temp of air
is 20 ⁰C. Determine the initial temp.
ANSWERS: [T1 = 703.667 oC]
C2.
T2.
H2.
An engine is work ing on ideal Otto cycle. The temp o f the beginning and the end
ofcompression is 60˚C and 450 ˚C .Determine the air standard efficiency and compression
ratio.
ANSWERS: [r = 6.94 η = 53.92%]
In air standard Otto C ycle the Maximum and Minimum temperatures are 1673 K and 288K.
The heat supplied per kg of air is 800 KJ. Calculate (i) The Compression Ratio. (ii) Efficiency
(iii) Max & Min Pressures. Take Cv = 0.718 kJ/kg K and γ = 1.4 for air. ANSWERS: [1)
r=5.244, 2) η=48.46%]
Determine the Air Standard Efficiency of an Otto cycle from the Following
Bore of the Cylinder is 14cm, Stroke Length 13 cm, Clearance Volume 290 cm3
ANSWERS: [r = 7.9 η = 56.25%]
C3.
T3.
In an Otto cycle the co mpressio n ratio is 8. The temperatures at the beg inn ing of
compression and at the end of heat supply are 3 10 K and 1600 K respectively. Assume
γ=1.4 and Cv = 0.717 kJ/Kg K. F ind (i) Heat S upplied (ii) Efficiency of the cycle.
ANSWERS: [1) Q = 636.56 kJ/Kg, 2) η = 56.46%]
An engine works o n the constant vo lume cycle. It has a cylinder bore of 90 mm and p
iston stroke of 100mm. the clearance vo lume of the engine is 0.06 litre. The actual
thermal efficiency of the engine is 22%. Determine the relative efficiency o f the engine.
Take γ=1.4.
ANSWERS: [η=35.21%]
H3.
C4.
T4.
H4.
C5.
In an engine working on Otto cycle a ir has a pressure of 1 bar and temp 303 k at the entry.
air is compressed with a compression ratio of 6.the heat is added at constant volume until
the temp rises 1773 k. Determine i) air standard efficiency ii)pressure and temp at the end of
compression iii) heat supplied.
ANSWERS: [i) η=51.16% ii) P2 = 12.286 bar T2 = 620.44 K iii) Q= 827.54 KJ/Kg]
An oil engine working on diesel cycle has cylinder bore of 190 mm and piston stroke of 230
mm. The clearance volume is 290 cm3 .the fuel injection takes place at co nstant pressure
for 6 % of the stroke. Determine the air standard efficiency. Also calculate the percentage of
loss of efficiency if fuel cut off is delayed from 6% to 11% of stroke with same compression
ratio.
ANSWERS: [1) η = 65.46% 2) Loss in efficienc= 6.095
The co mpression ratio of an oil engine wo rk ing on Diesel Cycle is 15. C ut off takes p lace at
12 % of the working stroke. The air is drawn in to cylinder at 100 kPa and 27°C. Assume
Cp =1.006 kJ/kg K and C v =0.717 kJ/kg K. Calculate:(i) Temperature at the end of compressio
n (ii) Pressure at the end of compression (iii) Air std. efficiency of the cycle.
ANSWERS: [ 1) T2 =886.25 2) P2 =44.31 bar 3) η = 57.18% ]
In an ideal diesel cycle, the temperatures at the beginning and at the end of compression are
5 7˚C and 603 ˚C respectively. The temperature at the begining and at the end o f expansion is
1950 ˚C and 870˚C respectively. Determine the ideal efficiency of the cycle. If the pressure at
the beginning is 1 bar .calculate maximum pressure in the cycle. ANSWERS: [ I) η = 56.89%
II) P2 =30.47 bar]
An engine operating a diesel cycle has maximum p ressure and temperature of 45 bars and1500
˚C. Pressure and temperature at the beginning of compression are 1 bar and 27 ˚C. Determine air
standard efficiency of the cycle. Take γ=1.4
ANSWERS: [η = 60.58%]
T5.
H5.
The compression ratio of an oil engine working on Diesel C ycle is 15. C ut off takes place at 6
% of the working stroke, heat add it io n at constant pressure. Determine air standard
efficiency of the cycle. Take γ=1.4
June 06 6 Marks
ANSWERS: [η = 61.19%]
An oil engine works on diesel cycle with temp of 25˚C at the starting of compression if the ratio
of adiabatic compression is 16 and that of adiabatic expansion I 9. F ind the efficiency of cycle
take γ=1.4 for air ANSWERS: [η = 62.449%]
I. C. Engines
C1.
Following readings taken during test on single cylinder four stroke Petrol engine,
Cylinder bore
= 25cm
Stroke length
= 400 mm
Mean effective pressure
= 6.5 bar
Engine speed
= 250 rpm
Net load on brake drum
= 1080 N
Effective diameter of drum
= 1.5 m
Fuel consumption
= 10 kg/hr
Calorific value
= 44300 kJ/kg
Clearance volume
= 1.196 X 10-3m3
Determine 1.Indicated power 2.Brake power 3.Friction power 4.Mechanical efficiency
5.Indicated thermal efficiency
6.Brake thermal efficiency 7.Air standard
efficiency 8.Relative efficiency 9.BSFC and 10. Brake mean effective pressure in bar.
Take γ=1.4.
ANSWERS: [1] I.P = 26.59kW [2] B.P = 21.206 kW [3] F.P = 5.384 kW [4] ηm= 79.75
% [5] ηith= 21.61% [6] ηbth= 17.23 % [7]ηair= 61.67 % [8]ηrel=35.04 % [9] BSFC
= kg/kW hr[10] Pbm= 16.286 bar
T1.
Following results refers to a test on I.C engine,
Indicated Power
= 42 KW
Friction Power
= 7 KW
Engine Speed
= 1800 rpm
Specific fuel consumption per b.p = 0.30 kg/Kwh
Caloric fuel value
= 43000 KJ/Kg
Calculate :- 1) Mechanical efficiency 2) Brake thermal efficiency 3) Indicated thermal
efficiency
ANSWERS: [1]ηm= 83.33 % [2] bth  27.91% [3] ηith= 33.49%
H1.
Following readings taken during test of four stroke single cylinder Petrol engine,
Load on the brake Drum
= 50 kg
Spring balance reading
= 7 kg
Fuel consumption
= 4 kg/hr
Diameter of brake drum
= 1250 mm
Engine speed
= 450 rpm
Calorific valueof the fuel
= 43000 kJ/kg
Calculate 1. Indicated thermal efficiency
2. Brake thermal efficiency.
Assumemechanical efficiency as 70 %.
ANSWERS: [1]ηith=37.14 %
[2]ηbth= 26 %
C2.
Following readings taken during test on single cylinder four stroke Petrol engine,
Stoke length
= 40 cm
Cylinder bore
= 25 cm
Mean effective pressure
= 4 bar
Engine speed
= 1400 rpm
Friction power
= 10 kW
Fuel consumption
= 20 litres/hr
Calorific value
= 45000 kJ/kg
Specific gravity
= 0.8
Determine: 1. indicated thermal efficiency 2.brake thermal efficiency.
ANSWERS: [1]ηith= 45.85%
[2]ηbth=40.85%
T2.
Following observations were recorded during test ona single cylinder oil engine,
Bore
= 300 mm
Stoke length
= 450 mm
Engine speed
= 300 rpm
I.M.E.P
= 6 bar
Net brake load
= 1.5 kN
Brake Drum diameter
= 1.8 m
Brake Rope diameter
= 2 cm
Calculate 1. Indicated Power2. Brake power and 3. Mechanical efficiency.
ANSWERS: [1] I.P= 47.713 kW [2] B.P= 42.883 kW [3]ηm= 89.88%
H2.
During testing of on single cylinder two stroke petrol engine following data is obtained.
Brake Torque
= 640 N m
Cylinder diameter
= 21 cm
Engine speed
= 350 rpm
Stoke length
= 28 cm
M.E.P
= 5.6 bar
Oil consumption
= 8.16 kg/hr
Calorific value
= 42705 kJ/kg
Determine 1. Mechanical efficiency 2. Brake thermal efficiency and 3. Brake specific
fuel consumption.
ANSWERS: [1]ηm= 74.04 %
[2]ηbth= 24.23 %
[3] BSFC= 0.348 kg/kWh
C3. Following readings taken during test on single cylinder four stroke Diesel engine,
Load on brake drum
= 55 kg
Spring reading
= 9 kg
Diameter of drum
= 1.4 m
Diameter of rope
= 0.8 m
Fuel consumption
= 3.8 kg/hr
Calorific value
= 42500 kJ/kg
Engine speed
= 600 rpm
Mechanical efficiency
= 83 %
Compression ratio
=7
Stroke to bore ratio
= 1.25
Determine 1.Brake thermal efficiency
2.Indicated thermal efficiency 3.Air standard
efficiency.
ANSWERS: [1]ηbth= 69.47 %[2] ηith= 83.70%[3] ηair= 83.70%
T3.
Following readings were taken during test on a single cylinder four stroke oil engine,
Cylinder diameter
= 270 mm
Stoke length
= 380 mm
Mean effective pressure
= 6 bar
Engine speed
= 250 rpm
Net load on brake
= 1000 N
Effective mean diameter of brake
= 1.5 m
Fuel used
= 10 kg/hr
C.V of fuel
= 44400 kJ/kg
Calculate 1. Brake power 2. Indicated Power 3. Mechanical efficiency and 4. Indicated
thermal efficiency.
ANSWERS: [1] B.P= 19.635 KW [2] I.P= 27.196kW[3]η m= 72.20 % [4]ηith= 22.05%
H3.
Following results refers to a test on C.I engine,
Indicated Power
= 37 kW
Frictional Power
= 6 kW
Brake Specific fuel consumption
= 0.28 kg/kWh
Calorific value of fuel
= 44300 kJ/kg
Calculate 1. Mechanical efficiency , 2. Overall efficiency and, 3. Indicated thermal
efficiency
ANSWERS: [1]ηm= 83.78 % [2]ηo= 29.02 %
[3] ηith=34.64 %
C4.
Following readings taken during test on two cylinder four stroke Petrol engine,
Swept volume
= 1.3 X 10-3 m3
Brake power
= 110 kW
Engine speed
= 1000 rpm
Fuel consumption
= 2.8 kg/hr
Mean effective pressure
= 900 kN/m2
Calorific value
= 42800 kJ/kg
Piston speed
= 5 m/s
If clearance volume is 10 % of swept volume. Take γ = 1.4. Determine 1.Stoke length
and diameter 3.Indicated thermal efficiency and 3.Relative efficiency.
ANSWERS:[1]l = 0.15 m, d = 0.105 m [2] ηith= 58.58 % [3] ηrel= 94.98%
T4.
A six cylinder 4 stroke IC engine is to develop 89.5 kW indicated power at 800 rpm. The
stroke to bore ratio is 1.25:1. Assuming mechanical efficiency of 80 % and brake mean
effective pressure of 5 bar. Determine diameter and stroke length of the engine.
ANSWERS:[1]d = 0.154m [2] l = 0.193 m
H4.
During test on a single cylinder four stroke engine having compression ratio of 6,
following data is recorded.
Bore
= 10 cm
Stoke length
= 12.5 cm
IMEP
= 2.6 bar
Dead load on Dynamometer
= 60 N
Spring balance reading
= 19 N
Effective radius of flywheel
= 40 cm
Fuel consumption
= 1 kg/hr
C.V of fuel
= 42000 kJ/kg
Engine speed
= 2000 rpm
Determine its, 1. Indicated Power2. Brake power 3. Mechanical efficiency 4. Air standard
efficiency and 5. Relative efficiency.
ANSWERS: [1] I.P = 4.254 kW [2] B.P= 3.435 kW [3]η m= 80.75% [4]ηair= 51.16 %
[5]ηrel=71.27 %
C5.
T5.
H5.
Following readings taken during test on six cylinder four stroke Petrol engine,
Brake Power
= 300 kW
Engine speed
= 2500 rpm
Stroke to bore ratio
= 1.25
Mean effective pressure
= 0.9 MPa
Mechanical efficiency
= 80 %
Indicated thermal efficiency
= 30 %
Calorific value
= 41900 kJ/kg
Determine stroke length, diameter and fuel consumption.
ANSWERS: [1] d = 0.150 m
[2] l = 0.187 m
[3] mf= 108 kg/hr
Following readings were taken during test on single cylinder four stroke oil engine,
Cylinder diameter
= 250 mm
Stoke length
= 400 mm
Mean effective pressure
= 6.5 bar
Engine speed
= 250 rpm
Net load on brake
= 1080 N
Effective diameter of brake
= 1.5 m
Fuel used per hour
= 10 kg
Calorific value of fuel
= 44300 kJ/kg
Calculate 1. Indicated Power 2. Brake power 3. Mechanical efficiency 4. Indicated
thermal efficiency.
ANSWERS: [1] I.P= 26.589 kW [2] B.P= 21.206 kW [3]η m= 79.75 %
[4]ηith= 21.61 %
A four cylinder four stroke petrol engine develops 200 kW brake power at 2500 rpm.
Stroke to bore ratio 1.2. If mean effective pressure is 10 bar and mechanical efficiency is
81%. Calculate bore and stroke of the engine. Also calculate indicated thermal efficiency and
brake thermal efficiency if 65 kg/hr of petrol is consumed having calorific value of 42000 kJ/kg.
ANSWERS: [1] d = 0.146 m, l = 0.175 m [2]ηith=32.56 %
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