P.A COLLEGE OF ENGINEERING AND TECHNOLOGY POLLACHI, COIMBATORE - 642 002
DEPARTMENT OF MECHANICAL ENGINEERING YEAR/SEMESTER-III/IV
THERMAL ENGINEERING LABORATORY MANUAL
P.A COLLEGE OF ENGINEERING AND TECHNOLOGY POLLACHI, COIMBATORE - 642 002
BONAFIDE CERTIFICATE
Registration No
Certified
that
this
is
the
bonafide
record
of
work
done
by
Mr.………………………………………………. of …………. - semester B.E. Mechanical Engineering Branch / Batch during the academic year …………………………. in the Thermal Engineering laboratory.
Head of the Department
Staff In-Charge
Submitted
for
the
University
practical
examination
held
on…………………… at P.A College of Engineering and Technology, Pollachi.
Internal Examiner
External Examiner
Date: ………………
Date: ………………
THERMAL ENGINEERING LABORATORY
•
Study of IC Engines
•
Determination of Valve Timing and Port Timing Diagrams.
•
Conducting performance Test on 4-stroke Diesel Engine.
•
Conducting heat Balance Test on 4-stroke Diesel Engine.
•
Conducting Morse Test on Multi cylinder Petrol Engine.
•
Conducting retardation Test to find Frictional Power of a Diesel Engine.
•
Study of Steam Boilers and Turbines.
•
Determination of Viscosity using Red Wood Viscometer.
•
Determination of Flash Point and Fire Point.
•
Conducting performance Test on Steam Turbine.
•
Conducting performance test on reciprocating air compressor
•
Conducting performance test on centrifugal blower
VALVE TIMING DIAGRAM OF FOUR STOKE DIESEL ENGINE Ex No:
Date:
Aim: To draw the valve timing diagram of the given four stroke cycle diesel engine.
Apparatus Required:
•
Four stroke cycle diesel engine
•
Measuring tape
•
Chalk
•
Piece of paper
Theory and Description: The diagram which shows the position of crank of four stroke cycle engine at the beginning and at the end of suction, compression, expansion, and exhaust of the engine are called as Valve Timing Diagram.
The extreme position of the bottom of the cylinder is called “Bottom Dead Centre” [BDC].IN the case of horizontal engine, this is known as “Outer Dead Centre” [ODC]. The position of the piston at the top of the cylinder is called “Top Dead Centre” [TDC].In case of horizontal engine this is known as “Inner Dead Centre” [TDC]. In case of horizontal engine this is known as “inner dead centre “[IDC] In an ideal engine, the inlet valve opens at TDC and closes at BDC. The exhaust valve opens at BDC and closes at TDC. The fuel is injected into the cylinder when the piston is at TDC and at the end of compression stroke but in actual practise it will differ. Inlet Valve opening and closing: In an actual engine, the inlet valve begins to open 5°C to 20 °C before the piston reaches the TDC during the end of exhaust stroke. This is necessary to ensure that the valve will be fully open when the piston reaches the TDC. If the inlet valve is allowed to close at BDC , the cylinder would receive less amount of air than its capacity and the pressure at the end of suction will be below the atmospheric pressure . To avoid this inlet valve is kept open for 25° to 40°after BDC. Exhaust valve opening and closing
Complete clearing of the burned gases from the cylinder is necessary to take in more air into the cylinder. To achieve this exhaust valve is opens at 35° to 45° before BDC and closes at 10° to 20° after the TCC. It is clear from the diagram, for certain period both inlet valve and exhaust valve remains in open condition. The crank angles for which the both
Valves are open are called as overlapping period. This overlapping is more than the petrol engine.
Fuel valve opening and closing: The fuel valve opens at 10° to 15 °before TDC and closes at 15° to 20 ° after TDC. This is because better evaporation and mixing fuel.
Procedure: •
Remove the cylinder head cover and identify the inlet valve, exhaust valve and piston of particular cylinder.
•
Mark the BDC and TDC position of flywheel This is done by Rotating the crank in usual direction of rotation and observe the position of the fly wheel, when the piston is moving downwards at which the piston begins to move in opposite direction. i.e. from down to upward direction. Make the mark on the flywheel with reference to fixed point on the body of the engine. That point is the BDC for that cylinder .Measure the circumference. That point is TDC and is diametrically opposite to the BDC.
•
Insert the paper in the tappet clearance of both inlet and exhaust valves
•
Slowly rotate the crank until the paper in the tappet clearance of inlet valve is gripped .make the mark on fly wheel against fixed reference. This position represent the inlet valve open (IVO). Measure the distance from TDC and tabulate the distance.
•
Rotate the crank further, till the paper is just free to move. Make the marking on the flywheel against the fixed reference. This position represents the inlet valve close (IVC). Measure the distance from BDC and tabulate the distance. Rotate the crank further, till the paper in the tappet clearance of exhaust valve is gripped. Make the marking on the flywheel against fixed reference. This position represents the exhaust valve open (EVO). Measure the distance from BDC and tabulate.
•
Then convert the measured distances into angle in degrees
Result: The valve timing diagram for the given four stroke Diesel engine was drawn.
PORT TIMING DIAGRAM OF TWO STROKE CYCLE PERTROL ENGINE Ex. No:
Date:
Aim: To draw the port timing diagram of given two stroke cycle petrol engine.
Apparatus Required:
• • •
Two stroke petrol engine Measuring tape Chalk
Theory and Description: In the case of two stroke cycle engines the inlet and exhaust valves are not present . Instead, the slots are cut on the cylinder itself at different elevation and they are called ports. There are three ports are present in the two stroke cycle engine . 1. Inlet port 2. Transfer port 3.
Exhaust port
The diagram which shows the position of crank at which the above ports are open and close are called as port timing diagram
The extreme position of the piston at the bottom of the cylinder is called “Bottom Dead centre “[BDC]. The extreme position of the piston at the top of the cylinder is called “TOP dead centre “[TDC]. In two stroke petrol engine the inlet port open when the piston moves from BDC to TDC and is closed when the piston moves from TDC to BDC. The transfer port is opened when the piston is moved from TDC to BDC and the fuel enters into the cylinder through this transport from the crank case of the engine. The transfer port is closed when piston moves from BDC to TDC. The transfer port opening and closing are measured with respect to the BDC.
The exhaust port is opened, when the piston moves from TDC to BDC and is closed when piston moves from BDC to TDC. The exhaust port opening and closing are measured with respect to the BDC.
Procedure:
•
Remove the ports cover and identify the three ports.
•
Mark the TDC and BDC position of the fly wheel. To mark this position follow the same procedure as followed in valve timing diagram.
•
Rotate the flywheel slowly in usual direction (usually clockwise ) and observe the movement of the piston
•
When the piston moves from BDC to TDC observe when the bottom edge of the piston . Just uncover the bottom end of the inlet port . This is the inlet port opening (IPO) condition , make the mark on the flywheel and measure the distance from TDC
•
When piston moves from TDC to BDC observe when the bottom edge of the piston completely covers the inlet port . This is the inlet port closing (IPC) condition. Make the mark on the flywheel and measure the distance from TDC.
•
When the piston moves from TDC to BDC, observe, when the top edge of the piston just uncover the exhaust port . This is the exhaust port opening [EPO] condition, Make the mark on the flywheel and measure the distance from BDC.
•
When the piston moves from BDC to TDC, observe, when the piston completely cover the exhaust port ,. This is the exhaust port closing condition [EPC]. Make the mark on the flywheel and measure the distance from BDC.
•
When the piston moves from TDC to BDC observe, when the top edge of the piston just uncover the transfer port. This is the transfer port opening [TPO] condition. Make the mark on the flywheel and measure the distance from BDC
•
When the piston moves from BDC to TDC, observe, when the piston completely covers the transfer port. This is the transfer port closing [TPC] condition. Make the mark on the flywheel and measure the distance from BDC.
Note:
1. 2.
The inlet port opening distance and closing distance from TDC are equal. The exhaust port opening distance and closing distance from BDC are equal.
3.
The transfer port opening distance and closing distance from BDC are equal.
Result: The port timing diagram for the given two stroke cycle petrol engine was drawn.
PERFORMANCE TEST ON DIESEL ENGINE Ex. No:
Date:
Aim:
To conduct performance test on given diesel engine in order to determine: • Brake power of the engine
•
Indicated power of the engine
•
Total fuel consumption
•
Specific fuel consumption
•
Mechanical efficiency
•
Break thermal efficiency or overall efficiency
•
Indicated thermal efficiency
Apparatus Required:
• • •
Diesel engine with loading arrangement Thread and scale (or) measuring tape Stop watch
•
Tachometer
Theory and Description: In diesel engine the diesel is used as the fuel. The diesel engine may be either two stroke engine or four stroke engine. In two stroke engine there is a one power stroke for each revolution of the crank shaft. In four stroke engine there is a one power stroke for every two revolution of the crank shaft, Most of the heavy duty engines are four stroke engines . The engine is provided with suitable loading arrangement to apple and measure the load. The provisions are also available to measure the fuel consumption and speed.
Definitions: Break power:
The useful power available at the crank shaft of the engine is called brake power (BP ) . The brake power of the engine are determined by • BP = 2NT kW • 60 x 1000 • Rope brake dynamometer ( T = WRe ) and
•
Prony brake dynamometer (T = WL ) and
•
Hydraulic dynamometer BP = WN / C kW
•
Electrical dynamometer
Indicated power: The power actually developed inside the cylinder due to the combustion of fuel are called indicated power (IP) (Or) IP = F.P + B.P Where F.P = Frictional Power
Specific Fuel Consumption: It is defined as the mass of the fuel consumed per hour per brake power of the engine . Its unit is Kg / KW – hr SFC = TFC B.P Where TFC = Total Fuel consumption in kg / hr
Total Fuel Consumption: It is the mass of fuel consumed at particular load consumed at particular load per hour .It is expressed in kg / hr
Mechanical Efficiency: It is defined as the ratio of Brake power to indicated power = ___B.P x 100 mech Heat Supplied
Brake thermal efficiency or overall efficiency: It is defined as the ratio of brake power to heat supplied by the combustion of fuel . B.T
or
overall
=
B.P Heat Supplied
Heat supplied = mass of the fuel consumed per sec x calorific value of fuel = mf x C.V. mf
= TFC Kg 3600 sec The calorific value of the diesel ranges from 42,000 KJ / Kg to 45,000 KJ/Kg depends on the quality of the fuel . The calorific value of petrol ranges from 41000 KJ/Kg to 44000 KJ/Kg
Indicated thermal efficiency or Thermal efficiency It is defined as the ratio of indicated power to heat supplied by the combustion of fuel = I.P x 100 I.T Heat supplied
=
I.P mf x C.V
x 100 ;
mf = TFC kg/sec 3600
Procedure:
• • •
From the name plate details calculate the maximum load that can be applied on the given engine. Check the engine for fuel availability, lubricant and cooling water connection. Release the load on the engine and start the engine with no load condition. Allow the engine to run for few minute to attain rated speed
• Note the speed of the engine and time taken for consumption of 10 cc of fuel •
Increase the load on the engine and note the speed of the engine and time taken for 10cc of fuel consumption
•
Repeat the procedure „5‟ up to 75% of the maximum load and tabulate the readings.
Graph: The following graphs has to be drawn
• •
Results:
B.P Vs TFC B.P Vs SFC
•
B.P Vs mech
•
B.P Vs B.T
•
B.P Vs I.T
Load test on given diesel engine were conducted and the TFC, BP, IP, SFC, determined at different loads.
mech, B.T and I.T
were
HEAT BALANCE SHEET ON IC ENGINE Ex. No:
Date:
Aim: To conduct the test on the given IC engine and to prepare the heat balance sheet
Apparatus Required:
• •
Given IC engine with loading arrangement measuring tape or Thread and scale
•
Tachometer
•
Stop watch
•
Bucket
•
Spring balance
•
Thermometer (3 No‟s)
Theory and Description:
A heat balance sheet is an account of heat supplied and heat utilised in various ways in the system. Necessary information concerning the performance of the engine is obtained from
the heat balance sheet. The heat balance sheet is generally done on second basis or minute basis or hour basis. The engine should equip with suitable loading arrangement to measure the brake power of the engine. Provisions are also made to measure the amount of air intake. Amount of fuel consumed, temperature of cooling water at inlet and outlet of the engine amount of cooling water circulated and temperature of exhaust gases. The heat supplied to the engine is only in the form of fuel – heat and is equal to . Qs
= mf x C.V Where, mf = mass of fuel used in kg/min C.V = Calorific value of fuel in KJ /kg
The various ways in which the heat is utilised are
•
Heat equivalent to brake power of the engine.
•
Heat carried away by the cooling water
•
Heat carried away by the exhaust gases
•
Unaccounted heat losses.
Formulae Used: Heat equivalent to B.P:
The brake power in KW is converted into KJ/min QB.P = B.P x 60 = _________ KJ/min
Heat carried away by the cooling water : (Qw) Qw = Mw x CPw (Two – Twi ) in KJ/min Where, Mw = mass of cooling water circulated in kg/min CPw = Specific heat of cooling water = 4.186 KJ/kgK Twi = Temperature of cooling water at inlet in °C Two = Temperature of cooling water at outlet of the engine in °C Heat carried away by the exhaust gases : (Qg) Qg mg ma mf C pg Tg TR
= mg CPg (Tg – TR ) = mass of the exhaust gases in kg/min = mass of air consumed in kg/min = mass of fuel consumed in kg/min = Specific heat of exhaust gases = 1.005 KJ/kgK = Temperature of exhaust gases in °C = Room temperature in °C
Unaccounted heat losses : Qun
= Qs - (Q.B.P + Qw + Qg ) in KJ / min
Procedure:
• •
From the name plate details, calculate the maximum load that can be applied on the given engine. Check the engine for fuel availability , lubricant and cooling water connection
•
Release the load on engine completely and start the engine with no load condition. Allow the engine to run for few minute to attain the rated speed
•
Adjust the cooling water flow and maintain steady flow of water.
•
Apply the load, from no load to required load slowly. At required load slowly. At required load note the following.
•
Load on the engine
•
Speed of the engine in Rpm
•
Time taken for 10 cc of fuel consumption
•
Manometer readings
•
Temperature of cooling water at engine inlet and engine outlet in °C
•
Time taken for collection of 5 lit or 10 lit of cooling water
•
Room temperature and temperature of exhaust gases
Heat Balance Sheet: S No
Particulars
1 2 3 4 5
Qs QBP Qw Qg Qun Total
Credits KJ/min
Debits %
KJ/min
%
Result: The test was conducted on the given IC engine and the heat balance sheet was prepared for the particular load.
MORSE TEST ON MULTI CYLINDER PETROL ENGINE
Ex. No:
Date:
Aim: To conduct mores test on given multi cylinder petrol engine in order to determine the indicated power developed in the each cylinder of the engine and to determine the mechanical efficiency.
Apparatus Required:
•
Multi cylinder petrol engine with ignition cut off arrangement
•
Loading arrangements
•
Tachometer
Theory and Description: For slow speed engine the indicated power is directly calculated from the indicator diagram. But in modern high speed engines, it is difficult to obtain accurate indicator diagram due to inertia forces, and therefore , this method cannot be applied . In such cases the mores test can be used to measure the indicated power and mechanical efficiency of multi cylinder engines. The engines test is carried out as follows. The engine is run at maximum load at certain speed. The B.P is then measured when all cylinders are working. Then one cylinder is made in operative by cutting off the ignition to that cylinder. As a result of this the speed of the engine will decrease. Therefore, the load on the engine is reduced so that the engine speed is restored to its initial value. The assumption made on the test is that frictional power is depends on the speed and not upon the load on the engine.
Definitions: Break power: (BP) The useful power available at the crank shaft of the engine is called brake power of the engine. The brake power of the engine are determined by
•
Rope brake dynamometer. T = WRe W = net load Re = effective radius of the brake drum
•
Prony brake dynamometer T = WL W = Load L = Distance at which the load is applied
Observation and Tabulation:
•
Brake power B.P =........... KW
•
Rated Speed N =...........Rpm
•
Type of loading : =...........
•
Radius of brake drum : R =........... „m‟
•
Radius of Rope r = =........... „m‟
• Number of cylinders = 4
S No
Conditions
Loading W1 kg
1
All cylinders are working
2
First cylinder was cut off and remaining are in working
3
Second cylinder was cut off and remaining are in working
4
Third cylinder was cut off and remaining are in working
5
Fourth cylinder was cut off and remaining are in working
Speed Rpm W2 kg
Note: The speed should be same for all readings
W1 kg
–
W2
Net load W in ‘N’
BP ‘KW’
•
Hydraulic dynamometer B.P = WN C W = Load N = Speed in RPM C = Dynamometer constant
•
Electrical dynamometer
Indicated power: (IP)
The power actually developed inside the engine cylinder due to the combustion of the fuel are called indicated power . IP = FP + BP ;
FP = Frictional power
Frictional power (FP) The power loss due to friction between the moving parts is called as frictional power.
Mechanical efficiency: ( mech) It is defined as the ratio of Brake power to indicated power. Mech
=
B.P
x 100
I.P
Procedure:
•
From the name plate details, determine the maximum load that can be given to the engine
• For example: B.P = 12.5 kw , N = 2000 rpm
B.P
=
2πNT__ __ 2πNT__ 60 x 1000
T
=
60 x 1000 x 12.5
=
59.68 N-m
2 π x 2000 T
=
.
.. W
W.Re
=
Say Re = 0.4m
T__ = Re
59.68 =
149.2N
0.4 ~
150 N
Maximum load that can be given to the engine was
75%
w = 75
x
150 = 112.5N
100
Max
= net load = 112.5 =
11.25kg
10 2.
Check the engine for fuel availability, lubricant and cooling water connections.
3.
Release the load completely on the engine and start the engine in no load conditions and allow the engine to run for few minutes to a ttain the rated speed.
4.
Apply the load and increase the load up to maximum load. (All four cylinders should be in working). Now note the load on the engine and speed of the engine say the speed is
„N‟ rpm 5.
Cut-off the ignition of first cylinder, Now the speed of engine decreased. Reduce the load
on the engine and bring the speed of the engine to „N‟ rpm. Now note the load on the engine. 6.
nd
Bring the all four cylinders are in working conditions and cut off the 2 , 3 cylinder in turn and adjust the load to maintain same „N‟ rpm and note the load .
rd
th
and 4
Result: Morse test was conducted on given petrol engine and indicated power developed in each cylinder is determined and mechanical efficiency is also determined.
STUDY OF STEAM BOILERS Ex. No:
Date:
Aim: To study the working of various types of steam boilers
Study of steam generators: Introduction:
A steam boiler is a closed vessel which boiler generator steam by transferring heat produced by burning of fuel to water. The steam boiler produced is used for power generation or process heating.
Selection of steam generators: The selection of type & size of a steam generator depends on the following factors.
• •
The power required & working pressure. The geographical position of power house.
•
The fuel & water available.
•
The probable load factor.
Classification of Boilers: The steam boilers are classified according to the following basic:
•
•
Flow of water & heat gases
•
Fire tube boiler
•
Water Tube boiler
Method of firing • Internally fired
•
•
Externally fired
Method of water circulation
• Natural circulation •
•
Forced circulation
Pressure developed
•
Low pressure boiler
•
High pressure boiler
• Nature of service
•
•
Stationary boiler
•
Mobile boiler
Design of gas passage
•
Single phase
•
Multi phase
High Pressure Boilers: Modern high pressure boilers generate steam at a pressure more than 75 bar. Example: Babcock & Wilcox boiler, Lamont boiler, BHEL boiler.
Lamont Boiler: A forced circulating boiler was first introduced in 1725 by Camont. The arrangement is shown in the figure. The most of sensible heat is supplied to the feed water passing through the Economizer. A centrifugal pump circulates the water equal to 8 to 10 times the weight of steam evaporated tubes and the part of water supplied drum. The large quantity of water circulated prevents the tubes from being overheated.
To secure the uniform flow of feed water through each of parallel boilers circuits a choke is fitted all the enhance to each circuits.
BHELL BOILERS: It consists of feed pump, a economizer a boiler drum, radiant & connective super heaters, FD fan, air pre heaters 1 & 2 .Electro static precipitator 1D fan & chimney. The feed water from the hot well is pumped with the help of a feed pump to boiler from the through economy .In boiler drawn the fed water is circulated to number of valves in the furnaces with fuel is burnt. The feed water is evaporated into wet steam and the wet steam flows back to boiler drawn. In this its supplied to prime mover through steam outlet.
The hot blue gases from the furnace pars over radiant & connective super heaters to super heat the steam, Then it passes through the pre heaters economizer and pre heater .Then the blue gases passes through the electrostatic precipitator.
Result:
Thus the working of various types of steam boiler was studied.
STUDY OF TURBINE Ex No:
Date:
Aim: To study the working of various types of steam turbines
Study of steam turbines: Introduction: A steam turbine is rotary machine which is designed to covert the energy of high temperature steam into mechanical power. In this the steam is first expanded in a set of nozzles or passages up to exit pressure where in the pressure energy of steam is converted into kinetic energy.
Classification of Steam Turbine: Steam turbines are classified according to:
•
Principle of action of steam a. Impulse turbine
•
b. Reaction turbine Direction of steam flow
•
Axial
•
Radial
•
Tangential
• Number of pressure stages
•
•
Single stage
•
Multi stage
Method of governing
•
Throttle
• Nozzle •
By-pass
•
Combination of throttle , nozzle by pass
Impulse Turbine: Velocity compound impulse turbine (Curtic Turbine) Arrangement of velocity compounded impulse turbine is shown in fig. In this type of turbine steam expands in a set of nozzle from the boiler pressure up to the condenser pressure which converts its pressure energy into kinetic energy. T his high velocity steam is passed over the rings of moving blades, each ring of moving blades being separated by a ring of fixed blades.
A part of high velocity steam is absorbed in the first ring of moving blades and remaining in the first ring of moving blades is passed to next ring of fixed blades. The function of fixed blades is to change the direction of flow of steam so that it can guide over the second ring of moving blades. The velocity of steam while passing over the fix blades is particularly constant except last for overcoming the friction losses . Again a part of steam velocity is absorbed in the second ring of moving blades & the process of absorbing the steam velocity continues till it finally wasted in exhaust.
Pressure compounded Impulse Turbine (Rateau Turbine) Arrangement of velocity compounds impulse turbine is steam is shown in fig. In this type of turbine the total pressure drop does not take place in a single ring of nozzle, but it is divided up in between the set of nozzle ring steam from the boiler is partially expanded in the first ring of nozzle and then it is passed over the ring of moving blades till its velocity is absorbed . Exhaust from blades till its velocity is absorbed.
Pressure – Velocity compounded Impulse Turbine: Arrangement of velocity compounded impulse turbine is shown in figure. In this arrangement both the previous method velocity & pressure compounding are utilized. The total pressure drop of steam is due to expansion in each stage is also compounded.
Reaction Turbine: Arrangement of velocity compounded impulse turbine is shown in figure. Unlike impulse turbine nozzle are not provided in this turbine and also there is a continuous pressure drop in the rings of fixed and moving blades. The function of fixed blades, which also get nozzle, is to change the direction of steam. So that it can enter into the ring of moving blades without shock the term reaction is used because the steam expands over the ring of moving blades giving a reaction on moving blades.
Result: Thus the working of various types of turbines are studied
Observation and tabulation
S.No
•
Room temperature T R = ……. °C
•
Density of oil at room temperature = …….. gm/cm 2
Temperature of oil °C
Time taken to fill 50ml flask
in „Sec‟
Kinematic Viscosity in
„Centi Stokes‟
Density in gm/cc
Dynamic (or) Absolute
viscosity „ Centi Poise‟
REDWOOD VISCOMETER
Ex. No:
Date:
Aim : To determine the kinematic viscosity and absolute viscosity of the given lubricating oil at different temperatures using Redwood Viscometer
Apparatus required: Redwood Viscometer Thermometer 0-100°c (2 No‟s) Stop watch 50 ml standard narrow necked flask Given Sample of oil
Description: The redwood viscometer consists of vertical cylindrical oil cup with an orifice in the centre of its base. The orifice can be closed by a ball. A hook pointing upward serves as a guide mark for filling the oil. The cylindrical cup is surrounded by the water bath. The water bath maintains the temperature of the oil to be tested at constant temperature. The oil is heated by heating the water bath by means of an immersed electric heater in the water bath, The provision is made for stirring the water, to maintain the uniform temperature in the water bath and to place the thermometer ti record the temperature of oil and water bath . The cylinder is 47.625mm in diameter and 88.90mm deep. The orifice is 1.70mm in diameter and 12mm in length, This viscometer is used to determine the kinematic viscosity of the oil. From the kinematic viscosity the dynamic viscosity is determined.
Theory and Definition: Viscosity
is the property of fluid. It is defined as “The internal resistance offered by the fluid to the movement of one layer of fluid over an adjacent layer „ . It is due to the Cohesion between the molecules of the fluid. The fluids which obey the Newton law of Viscosity are called as Newtonian fluid. The dynamic viscosity of fluid is defined as the shear required producing unit rate of angular deformation.
Formulae used: Kinematic Viscosity =
γ
At - B t
in stokes or in centi stokes
A = 0.0026 B = 1.72 A = 0.26 B = 172 t = Saybolt second Density of oil at particular temperature
du dy
ρt
ρt
=
ρR - 0.00065 ( T - TR )
T
=
Temperature at which the density is required
TR
=
Room Temperature
ρR
=
Density of oil at room temperature in gm / cm
=
0.84 (or) 0.85 gm/cm3
3
i.e.,
τ
=
μ
=
μ
(or)
τ du/dy
Where μ
=
Co-efficient of viscosity (or) Dynamic viscosity (or) Absolute viscosity
=
Shear stress
=
Angular deformation (velocity gradient)
du dy
τ
The unit of dynamic viscosity in SI system is
N – Sec 2 m
(or)
kg m-sec
(or)
poise
In metric system:
dynes – Sec 2 m 1 N – S m2
= 10 Poise
or
gm __ cm- Sec
The kinematic viscosity of the fluid is defined as the ratio of the dynamic viscosity toss density of
the fluid . Its symbol is „r‟
γ
μ
=
_ _
ρ
;
ρ = mass density of oil
or
Stokes
The unit of kinematic viscosity
2
1m sec
In SI system:
m2/sec
In metric system = 4 2 = 10 cm sec
cm 4 = 10 stokes
2
sec
One hundredth part of stoke is called Centi Stoke.
Procedure:
• •
Clean the cylindrical oil cup and ensure the orifice tube is free from dirt. Close the orifice with ball valve.
•
Place the 50 ml flask below the opening of the Orifice.
•
Fill the oil in the cylindrical oil cup up to the mark in the cup.
•
Fill the water in the water bath.
•
Insert the thermometers in their respective places to measure the oil and water bath temperatures.
•
Heat the by heating the water bath, Stirred the water bath and maintain the uniform temperature.
•
At particular temperature lift the bal valve and collect the oil in the 50 ml flask and note the time taken in seconds for the collecting 50 ml of oil. A stop watch is used measure the time taken. This time is called Redwood seconds.
•
Increase the temperature and repeat the procedu re for different temperatures.
„8‟ and note down the Redwood seconds
Graph: The following graph has to be drawn (1)Temperature Vs Redwood seconds (2)Temperature Vs Kinematic Viscosity (3)Temperature Vs Dynamic Viscosity
Result: The kinematic and dynamic viscosity of given oil at different temperatures were determined.
S.No
Temperature of oil in °C
Observation
FLASH AND FIRE POINT [CLEVELAND OPEN CUP APPARATUS]
Ex. No:
Date:
Aim: To determine the flash and fire point temperatures of the given sample of lubricating oil using Cleveland open cup apparatus.
Apparatus Required:
1. Cleveland open cup apparatus 2. Thermometer 3. Splinter sticks 4. Sample of oil
Theory and Definition:
The flash point of the lubricating oil is defined as the lowest temperature at which it forms vapours and produces combustible mixture with air. The higher flash point temperature is always desirable for any lubricating oil. If the oil has the lower value of flash point temperatures, it will burn easily and forms the carbon deposits on the moving parts. The minimum flash temperature of the oil used in IC engines varies from 200°C to 250°C. When the oil is tested using the open cup apparatus, the temperature is slightly more than the above temperatures. The flash and fire point temperatures may differs by 20°C to 60°C when it is tested by open cup apparatus. However, a greater difference may be obtained if some additives are mixed with oil. The flash and fire power point temperatures depends upon the volatility of the oil.
Description:
The Cleveland open cup apparatus consists of a cylindrical cup of standard size. It is held in position in the metallic holder which is placed on a wire gauge. It is heated by means of an electric heater housed inside the metallic holder. A provision is made on the top of the cup to hold the thermometer. A standing filling mark is done on the inner side of the cup and the sample of oil is filled up to the mark. This apparatus will give more accurate results than the pensky martins closed cup apparatus.
Procedure:
•
Clean the cup and fill it with the given sample of oil up to the filling mark.
•
Insert the thermometer in the holder. Make sure that the thermometer should not touch the metallic cup.
•
Heat the oil by the means of electric heater so that the sample of oil gives out vapour at the rate of 10°C per minute.
•
When the oil gives out vapour, introduce the test flame above the oil, without touching the surface of the oil and watch for flash with flickering sound.
•
Introducing the test flame should not continue at regular intervals until the flash is observed with peak flickering sound. The temperature corresponding to this flickering sound is noticed and it is the flash point temperature of the given sample of oil.
•
Continue the process of heating and introducing the test flame until the oil will begins to burn continuously and observe the temperature. This is the fire pint temperature of the given sample of oil.
•
Repeat the test twice or thrice with fresh sample of oil and observe the results.
•
The observations are tabulated.
Result: The flash and fire point temperatures of the given sample of oil were determined using Cleveland open cup apparatus. The flash point temperature of the given sample o f oil is ______°C The fire point temperature is of the given sample of oil is _____ _ °C
TEST ON RECIPROCATING AIR COMPRESSOR Ex. No:
Date:
Aim: To conduct performance test on a two stage reciprocating compressor and to determine the volumetric efficiency
Apparatus Required: The test unit consisting of an air reservoir on air intake tank with an orifice and a U tube manometer, the compressor having pressure gauge, energy meter and stop watch. Specification:
Compressor Model :
2 stage reciprocating
Diameter of low pressure piston
=......
mm
Diameter of high pressure piston
=......
mm
Stoke =...... Speed =......
Tank Capacity =...... Motor Capacity
=......
mm rpm
litres HP
Formula Used: Volumetric Efficiency =
Va
x 100
Vt
Where : Va - actual volume of air compressor
Vt -Theoretical volume of air Actual volume of air compressed (Va)
Va = Cd x A x √(2gh) m3 / sec Cd - Coefficient of discharge of orifice 2 2 A - Orifice area in m = π d 4 H - Air head causing flow H = h x ρwater = m of oil ρoil x 100 h
= ( h1 ~ h2 ) cm of water
Tabulation:
S.No
Reservoir Pressure gauge reading P 2 kgf/cm
U – tube manometer reading h1
h2
h = (h1 – h2) cm
Time for 5 revolutions of energy meter (sec)
3
ρwater ρair
= = =
1000 kg/m 3 1.162 kg/m at 30°C 1.6 x 1000 = 13.79 m of water 1.16 x 100
H
= = =
h1 ~ h2 cm of water 3 1000 kg/m 3 1.173 kg/m at 29 °C
ρw ρoil Theoretical Volume of air , VT
=
π D2LN
3
m /s
4 x 60 D - Diameter of piston – 0.7 m L - Stroke length – 0.085 m N - Speed – 850 rpm Isothermal – Va x 100 Vt Va - Actual volume of air compressor VT - Theoretical volume of air x - No of revolutions 5 Emc – Energy meter constant – 200 rev/hr t – time for 5 rev in seconds Compressor output = ρa x Va KW
1000 5 2 Pa – Atmospheric Pressure = 1 bar = 1 x 10 N / m 3 Va – Actual volume of air (m / s) C- Compression ratio = gauge pressure + Atmospheric pressure
Procedure: •
Close the outlet valve.
•
Fill up the manometer with water up to half level.
•
Start the compressor and observe the pressure developing slowly.
•
At a particular test, pressure outlet valve is opened slowly and adjuster so that pressure in tank and maintained constant.
•
Observe the following reading time taken for 5 revolution of energy meter disc.
Graph:
•
Manometer level
•
Speed of the compressor in rpm
Thus performance test on a two stage reciprocating air compressor is conducted and graph is drawn for pressure and vol.
Result: The test was conducted and the volumetric efficiency of the compressor was determined. The average volumetric efficiency of the air compressor is__________
CENTRIFUGAL BLOWER TEST RIG Ex. No:
Aim:
Date:
To study the performance characteristics of centrifugal blower test rig.
Apparatus Required:
•
Stopwatch
•
Anemometer
Formulae Used: Total fan efficiency f
=
Power output n-1 n
Power input
•
Power output
=
n
P1V1 [( P2/P1)
n-1
•
Power input
=
Nc x 3600 z x Emc
Where
•
n
=
1.4
P1
-
Air intake pressure N/m
V1
-
Rate of volume of compressed air
P2
-
Delivery pressure in N/mm
Nc
-
No of revolutions of energy meter
z
-
Time in seconds
Emc
-
Energy meter constant
2
2
Pressure from height of water P
=
ρw Hw g
ρw
-
density of water (1000 kg/m3)
Where
-1]
Observation and Tabulation:
Room temperature
:
...........°C
Barometric pressure
:
........... mm
Energy meter constant
S.No
:
to
Hg
........... revolutions / KWh
Diameter of Suction pipe
:
........... mm
Area of Suction Pipe (A)
:
........... m
2
Manometer reading Manometer reading Time in sec Velocity of air in in (mm) for water in mm for water required for 10 m/sec measured inlet side (suction) outlet side rev of energy by anemometer meter (V)
S.No Delivery Pressure
Power Input
Hw
-
Power Output Blower capacity
Height of water in mm
Efficiency ( %)
G
-
Acceleration due to gravity = 9.81 m / s
Suction pressure P1
-
Atm pressure +P1
Delivery pressure P2
-
Atm pressure +P2
Atmospheric pressure -
2
1.0133 bar
Procedure: • Note down the barometric pressure in mm of Hg and room temperature in °C. •
Start the blower.
•
Adjust the delivery pressure by adjusting throttle at outlet side.
•
To measure volume of air flow rate, measure velocity of suction air by using anemometer.
•
Measure speed of blower by tachometer.
• Note the time in sec required for 5 revolutions of energy meter to measure power at inlet. •
Repeat same procedure 3 to 6 times for different pressure.
Result: Power input
=.............
Power output =..............
