THERMAL ENGINEERING LAB MANUAL (For III Year B. Tech I Semester (R-14), Mechanical Engineering)

DEPARTMENT OF MECHANICAL ENGINEERING SRI VENKATESWARA COLLEGE OF ENGINEERING AND TECHNOLOGY (AUTONOMOUS) R. V. S. NAGAR, CHITTOOR-517127.

Name of the student: _____________________________ Roll Number: ______________ Branch: ______________ Name of the Laboratory: __________________________ Year & Sem: _______________ Academic Year: _______

THERMAL ENGINEERING LAB MANUAL LIST OF EXPERIMENTS 1. Determination of Viscosity of lubricating oil using i. Redwood Viscometer –I ii. Redwood Viscometer –I iii. Say bolt Viscometer. 2. Determination of Flash point and fire point of sample fluid using i. Abel’s apparatus ii. Pensky Marten’s apparatus. 3. Study of Bomb and Junker’s gas calorimeter to determine the Calorific value of fuels. 4. Study of the constructional details & working principles of two-stroke/ four stroke petrol/diesel engine and to draw i.Valve Timing Diagram ii. Port Timing Diagram 5. Performance test on two stage reciprocating Air compressor. 6. Performance test and Preparation of Heat balance sheet on 4-stroke, single cylinder diesel engine. 7. Retardation test on 4-stroke, single cylinder diesel engine 8. Morse test on 4-stroke, 4- cylinder petrol engine. 9. Performance test on 2- stroke, single cylinder petrol engine. 10. Performance test on refrigeration test rig. 11. Assembly and Disassembly of IC engines.

INDEX S. No

Date

Name of the Experiment

Page No:

Signature of the Faculty

RED WOOD VISCOMETER- I AIM To determine the viscosity in Redwood seconds of the given sample of oil and to plot the variation of Redwood seconds, kinematic and dynamic viscosity with temperature. APPARATUS o Redwood viscometer-I, o Stopwatch, o Thermometer (0-1100C) o Measuring flask. (50 c.c.) THEORY The viscosity of given oil is determined as the time of flow in Redwood seconds. The viscosity of a fluid indicates the resistance offered to shear under laminar condition. Dynamic viscosity of a fluid is the tangential force on unit area of either of two parallel planes at unit distance apart when the space between the plates is filled with the fluid and one of the plate’s moves relative to the other with unit velocity in its own plane. The unit of dynamic viscosity is dyne-sec/cm2. Kinematic viscosity of a fluid is equal to the ratio of the dynamic viscosity and density of the fluid. The unit of kinematic viscosity is cm2/sec. DESCRIPTION Redwood viscometer-I consists of a water bath and oil bath, both provided with two thermometers inside them. There is a ball valve, which is located at center of oil bath to flow of oil through the orifice. A heater with regulator is fixed for heating purpose. PROCEDURE 1. Clean the oil cup with a suitable solvent thoroughly and dry it using soft tissue paper. 2. Keep the ball valve in its position so as to keep the orifice closed.

3.

The water is taken into the water bath and the oil whose viscosity is to be determined is taken into the oil cup up to the mark.

4. Note down the time taken in Redwood seconds for a collection of 50 cc . of oil with a stopwatch at the room temperature without supply of electric supply. 5. Heat the bath and continuously stir it taking care to see that heating of the bath is done in a careful and controlled manner. 6. When the desired temperature is reached, place the cleaned 50 c.c. Flask below the orifice in position. 7. Remove the ball valve and simultaneously start a stopwatch. Note the time of collection of oil up to the 50 c.c. Mark. 8. During the collection of oil don’t stir the bath. Repeat the process at various temperatures. OBSERVATIONS Time for

S. No.

Oil

collecting

Temperature O C

50 c.c. of oil sec

Kinematic viscosity  B    A  t     t  cm 2/ sec

Absolute Density ()

Viscosity



gm

sec

dyne  sec/ cm 2

Where A

= 0.0026 cm2/sec2

B

= 1.72 cm 2

GRAPHS TO BE DRAWN 1.

Redwood seconds Vs . temperature

2.

Kinematic Viscosity Vs . temperature

3.

Absolute Viscosity Vs . temperature

Temp

MODEL GRAPHS

Redwood seconds

Kinematic Viscosity

Absolute Viscosity

PRECAUTIONS 1. Stir the water continuously so that the temperature of the oil and water are equal. 2. Before collecting the oil at a temperature, check whether the oil is up to the Indicator in the oil cup. 3. Always take the readings at a stable temperature 4. Ensure proper setting of the ball valve to avoid leakage RESULT Variation of Redwood seconds, absolute viscosity and Kinematic viscosity with temperature, were observed and found to be decreasing with temperature.

RED WOOD VISCOMETER- II

AIM To determine the viscosity in redwood second of the given samples of oil and to plot the variation of Redwood seconds, kinematic and dynamic viscosity with temperature. INSTRUMENTS: Redwood viscometer-II, Stopwatch, Thermometer (0-1100C), Measuring flask. (50 c.c.)

THEORY The viscosity of given oil is determined as the time of flow in redwood seconds. The viscosity of a fluid indicates the resistance offered to shear under laminar condition. Dynamic viscosity of a fluid is the tangential force on unit area of either of two parallel planes at unit distance apart when the space between the plates is filled with the fluid and one of the plate’s moves relative to the other with unit velocity in its own plane. The unit of dynamic viscosity is dyne-sec/cm2. Kinematic viscosity of a fluid is equal to the ratio of the dynamic viscosity and density of the fluid. The unit of kinematic viscosity is cm 2 sec DESCRIPTION Redwood viscometer-II consists of a water bath and oil bath, both provided with two thermometers inside them. There is a ball valve, which is located at center of oil bath to flow of oil through the orifice. A heater with regulator is fixed for heating purpose. PROCEDURE 1. Clean the oil cup with a suitable solvent thoroughly and dry it using soft tissue paper. 2. Keep the ball valve in its position so as to keep the orifice closed. 3. The water is taken into the water bath and the oil whose viscosity is to be determined is taken into the oil cup up to the mark.

4. Before switch on the electric supply, at room temperature note down the time taken in Redwood seconds for a collection of 50 c.c. of oil with a stopwatch. 5. Heat the bath and continuously stir it taking care to see that heating of the bath is done in a careful and controlled manner. 6. When the desired temperature is reached, place the cleaned 50 c.c. flask below the orifice in position. 7. Remove the ball valve and simultaneously start a stopwatch. 8. Note the time of collection of oil up to the 50 c.c. Mark. 9. During the collection of oil don’t stir the bath. 10. Repeat the process at various temperatures. OBSERVATIONS \ Time for

S. No.

Oil

collecting

Temperature

50 c.c. of

C

oil

0

sec

Kinematic viscosity B    A  t      t 

cm 2/ sec

Absolute Density

Viscosity

()



gm/sec

dyne  sec/ cm 2

Where cm2/sec2

A = 0.0272 B = 11.2 cm 2

GRAPHS TO BE DRAWN 1.

Redwood seconds vs. temperature

2.

Kinematic Viscosity vs. temperature

3.

Absolute Viscosity vs. temperature

Temp

MODEL GRAPHS

Redwood seconds

Kinematic Viscosity

Absolute Viscosity

PRECAUTIONS 1.

Stir the water continuously so that the temperature of the oil and water are equal.

2.

Before collecting the oil at a temperature, check whether the oil is up to the Indicator in the oil cup.

3.

Always take the readings at a stable temperature

4.

Ensure proper setting of the ball valve to avoid leakage

RESULTS Variation of Redwood seconds -II, absolute viscosity and Kinematic viscosity with temperature, were observed and found to be decreasing with temperature

SAYBOLT VISCOMETER AIM To determine the viscosity in Saybolt seconds of the given sample of oil and to plot the variation of Saybolt seconds, kinematic and dynamic viscosity with temperature. INSTRUMENTS o Saybolt viscometer, o Stop watch, o Thermometer (0-1100C), o Measuring flask (60 cc) THEORY The viscosity of given oil is determined as the time of flow in Saybolt seconds. The viscosity of a fluid indicates the resistance offered to shear under laminar condition. Dynamic viscosity of a fluid is the tangential force on unit area of either of two parallel planes at unit distance apart when the space between the plates is filled with the fluid and one of the plate’s moves relative to the other with unit velocity in its own plane. The unit of dynamic viscosity is dyne-sec/cm2. Kinematic viscosity of a fluid is equal to the ratio of the dynamic viscosity and density of the fluid. The unit of kinematic viscosity is

cm 2

sec .

DESCRIPTION Saybolt viscometer consists of a water bath and oil bath, both provided with two thermometers inside them. There is a ball valve, which is located at center of oil bath to flow of oil through the orifice. A heater with regulator is fixed for heating purpose. PROCEDURE 1. Clean the oil cup with a suitable solvent thoroughly and dry it using soft tissue paper. 2. Keep the cork in its position so as to keep the orifice closed. 3. The water is taken into the water bath and the oil whose viscosity is to be determined is taken into the oil cup up to the mark.

4. Before switch on the electric supply, at room temperature note down the time taken in Saybolt seconds for a collection of 60 c.c. of oil with a stop watch. 5. Heat the bath and continuously stir it taking care to see that heating of the bath is done in a careful and controlled manner. 6. When the desired temperature is reached, place the cleaned 60 c.c. flask below the orifice in position. 7. Remove the cork valve and simultaneously start a stopwatch. Note the time of collection of oil up to the 60 c.c. Mark. 8. During the collection of oil don’t stir the bath. 9. Repeat the process at various temperatures. OBSERVATIONS

Time for

S. No.

Oil

collecting

Temperature

50 c.c. of

C

oil

0

Kinematic viscosity B    A  t    

 t 

Absolute Density () gm sec

sec

cm 2/sec

Viscosity

 dyne  sec/ cm 2

Where A= 0.00226 cm2/sec2 B=1.8 cm 2 GRAPHS TO BE DRAWN 1.

Saybolt seconds vs. temperature

2.

Kinematic Viscosity vs. temperature

3.

Dynamic Viscosity vs. temperature

Temp

MODEL GRAPHS

Redwood seconds

Kinematic Viscosity

Absolute Viscosity

Tem p

PRECAUTIONS 1. Stir the water continuously so that the temperature of the oil and water are equal. 2. Before collecting the oil at a temperature, check whether the oil is up to the level. 3. Always take the readings at a stable temperature. 4. Ensure proper setting of the cork to avoid leakage. RESULT Variation of Saybolt Seconds, Absolute viscosity and Kinematic viscosity with temperature, were observed and found to be decreasing with temperature.

ABEL’S FLASH AND FIRE POINT TEST

AIM To determine the flash and fire point of the given sample of oil using Abel’s apparatus closed cup methods. APPARATUS Abel’s apparatus, Thermo meter (0-110oC). THEORY This method determines the closed cup flash and fire points of petroleum products and mixtures to ascertain whether they give off inflammable vapours below a certain temperature. FLASH POINT: It is the lowest temperatures of the oil, at which, application of test flame causes the vapour above the sample to ignite with a distinct flash inside the cup. FIRE POINT: It is the lowest temperature of the oil, at which, application of test flame causes burning for a period of about five seconds. DESCRIPTION The apparatus consists of a brass cup and cover fitted with shutter mechanism, test flame arrangement, hand stirrer, thermometer socket. The brass cup is heated by water bath (with energy regulator), fitted with a funnel and overflow pipe. PROCEDURE 1. Clean the oil cup and fill the up to the mark with the sample oil. 2. Insert the thermometer into the oil cup through the provision to note down the oil temperature. 3. Using the Energy regulator, control the power supply given to the heater and rate of heating 4. The oil is heated slowly when temperature of oil rises; it is checked for the flash point for every one-degree rise in temperature.

5. After determining the flash point, the heating shall be further continued. The temperature at which time of flame application that causes burning for a period at least 5 seconds shall be recorded as the fire point. 6. Repeat the experiment 2 or 3 times with fresh sample of the same oil 7. Take the average value of flash and fire points. PRECAUTIONS: 1. Stir the oil bath continuously to maintain the uniform temperature of sample oil. 2. The bluish halo that some time surrounds the test flame should not be confused with true flash. OBSERVATIONS: Sample oil

Flash Point,

RESULT The flash point is observed at _____ 0 C The fire point is observed at ______ 0 C

0

C

Fire Point,

0

C

PENSKY MARTEN’S FLASH AND FIRE POINT

AIM To determine the flash and fire point of the given sample of oil using Pensky Marten’s apparatus by both open and closed cup methods. APPARATUS o Pensky Marten’s apparatus, o Thermometer (0-110oC). THEORY This method determines the closed cup and open cup flash and fire points of petroleum products and mixtures to ascertain whether they give off inflammable vapours below a certain temperature. Flash Point: It is the lowest temperatures of the oil at which application of test flame causes the vapour above the sample to ignite with a distinct flash inside the cup. Fire point It is the lowest temperature of the oil, at which, application of test flame causes burning for a period of about five seconds. DESCRIPTION The apparatus consists of a brass cup and cover fitted with shutter mechanism without shutter mechanism (open cup), test flame arrangement, hand stirrer (closed cup), thermometer socket, etc., heated with energy regulator, a thermometer socket made of copper. PROCEDURE 1. Clean the oil cup thoroughly and fill the oil cup with the sample oil to be tested up to the mark. 2. Insert the thermometer into the oil cup through a provision, which measures the rise of oil temperature. 3. Using the Energy regulator, control the power supply given to the heater and rate of heating 4. The oil is heated slowly when temperature of oil rises, it is checked for the flash point for every one degree rise in temperature.

5. After determining the flash point, the heating shall be further continued. The temperature at which time of flame application which causes burning for a period at least 5 seconds shall be recorded as the fire point. 6. Repeat the experiment 2 or 3 times with fresh sample of the same oil 7. Take the average value of flash and fire points. PRECAUTIONS 1. Stir the oil bath continuously to maintain the uniform temperature of sample oil. 2. The bluish halo that some time surrounds the test flame should not be confused with true flash. OBSERVATIONS

Sample oil

Flash Point,

0

C

RESULT The flash point is observed at _________ 0 C The fire point is observed at _____________ 0 C

Fire Point,

0

C

BOMB CALORIMETER AIM To determine the water equivalent of the calorimeter using the given sample of solid or liquid fuel of known calorific value (or) To determine the calorific value of the given solid or liquid fuel if the water equivalent of the calorimeter known. APPARATUS Bomb, water jacket, stirrer, calorimeter vessel, combined lid, sensitive thermometer, analytical balance with weight box, oxygen cylinder with pressure gauge, fuse wire, cotton thread, firing unit, regulating valve and crucible hand pellet press PRINCIPLE OF OPERATION A Bomb Calorimeter will measure the amount of heat generated when matter is burnt in a sealed chamber (Bomb) in an atmosphere of pure oxygen gas. A known amount of the sample of fuel is burnt in the sealed bomb, the air in the bomb being replaced by pure oxygen under pressure. The sample is ignited electrically. As the sample burns heat is produced and rises in the temperature. Since the amount of heat produced by burning the sample must be equal to the amount of heat absorbed by the calorimeter assembly, and rise in temperature enables the determination of heat of the combustion of the sample. If W = Water equivalent of the calorimeter assembly in calories per degree centigrade. T = Rise in temperature (registered by a sensitive thermometer) in degrees centigrade. H = Heat of combustion of material in calories per gram. M = Mass of sample burnt in grams. Then W  T  H  M

If the water equivalent of the calorimeter is to be determined, a substance like Benzoic acid has a stable calorific value can be burnt in the bomb. Assuming the calorific value of Benzoic acid and water equivalent can be determined.

CALORIFIC VALUE Gross or higher calorific value: The total amount of heat produced when one unit mass of fuel has been burnt completely and the products of combustion have been cooled to room temperature. Net or Lower Calorific Value: The net heat produced when unit mass of fuel is burnt completely and the products are permitted to escape. LCV = HCV – Latent heat of water vapour formed DESCRIPTION i.

BOMB The bomb consists of three parts i.e. bomb body, lid and the cap. Bomb Body and the lid are made of corrosion resistant stainless steel containing Chromium, Nickel and Molybdenum. The bomb body is cylindrical vessel having a capacity of 300 ml. The walls are strong enough to withstand the normal operating pressure (30atm) to extreme high pressures (300 atm.). During burning at high pressure the nitrogen and sulphur contents are oxidized to nitric acid and sulphuric acid respectively. The corrosion resistant nature of the bomb material protects it from corrosive vapors. The bomb has lid, which is provided with two terminals. The metallic rods pass through the terminals one of which are provided with a ring for placing the crucible with a small hook and the other with a groove. Each rod is also provided with a ring to press the fuse wire attached to it. The upper side of the lid also provided with a small hook rod lifting and with a Schrader valve for filling oxygen in the bomb

ii.

WATER JACKET The water jacket is made of copper and is highly chromium plated on the inside and outside to minimize radiative losses. The jacket is filled with water.

iii.

STIRRER UNIT A stirrer is provided which is driven directly by an electric motor. The stirrer is immersed in the water. The water is continuously stirred during the experiment for uniform heat distribution.

iv.

COMBINED LID This is made of Borolite sheet and is provided with a hole for to keep the stirrer unit in fixed position and hole to insert the temperature sensor. It has also

another hole to take out the connecting wires from the terminals on the bomb lid to firing unit. v.

HAND PELLET PRESS It is used for pressing the powder into a pellet.

vi.

CRUCIBLE It is made of stainless steel. The fuel to be burnt is weighed in this crucible.

vii.

IGNITION WIRE It is recommended that platinum wire used but an alternative nichrome wire is also being offered.

viii.

FIRING UNIT It consists of the firing key, provision to give power to the stirrer motor, a switch for operating the stirrer motor, two indicating lamps. When the circuit is completed the indicating lamp glows. After the firing key is closed on, the fuse wire burns, the indicating lamp stops glowing indicating the burning of the fuse wire.

PROCEDURE  About 0.5 to 1 grm of finely ground benzoic acid (Preferably compressed into a 

pellet) is accurately weighed and taken into crucible.  Place the bomb lid on the stand provided and stretch pieces of fuse wire across the electrodes (metal rods) provided in the lid tie about 5 cm of sewing cotton round the wire.  Place the crucible in position and arrange the loose end of the cotton thread to contact the Benzoic acid pellet in the crucible.  About 10 ml of distilled water are introduced into the bomb to absorb vapors of sulphuric acid and nitric acids formed during the combustion and lid of the bomb is



screwed  Charge the bomb slowly with oxygen from the oxygen cylinder to a pressure of 25 atm. close the value and detach the bomb from the oxygen supply.

 Fill the calorimeter vessel with sufficient water to submerge the cap of the bomb to a depth of at least 2mm leaving the terminals projecting lower the bomb carefully in

the calorimeter vessel and after ascertaining that it is gas tight, connect the terminals to the ignition circuit.  Adjust the stirrer and place the temperature sensor and cover in position. Start the stirring mechanism, which must be kept in continuous operation during the experiment after stirring for 5 minutes note the temperature reading of the calorimeter. Close the circuit momentarily to fire the charge and continue the observations of the temperature at an interval of one minute till the rate of change of temperature becomes constant.  Afterwards stop the stirrer and remove the power supply to the firing unit. Remove the bomb from the calorimeter and relax the pressure by opening the value. Verify that the combustion is complete and washout the contents of the bomb clean and dry.  Calculate the calorific value of the fuel or water equivalent of the calorimeter.

OBSERVATIONS: Weight of the empty crucible W1 

=

gm

Weight of the empty crucible + Benzoic acid pellet W2 

=

gm

Weight of the benzoic acid pellet W2  W1 

=

gm

Weight of water taken in the calorimeter W3 

=

gm

Temperature of the water just before firing t1 

=

0C

t3 

=

0C

Temperature of the water after firing CALCULATIONS

Heat produced by burning of benzoic acid + Heat produced by burning of fuse wire and cotton wire etc = Heat absorbed by calorimeter.

W2

 W1  Cv  W3  We t2  t1 

PRECAUTIONS Sample should not exceed 1 gms . Don’t charge with more oxygen than is necessary. Don’t fire the bomb if gas bubbles are leaking from the bomb when it is submerged in water. RESULT Water equivalent of calorimeter We 

=

Calorific value of sample Cv 

=

gm Cal/ gm

RESULT Water equivalent of calorimeter We 

=

Calorific value of sample Cv 

=

gm Cal/gm

JUNKER’S GAS CALORIMETER AIM To find the calorific value of given gaseous fuel. APPARATUS i) Calorimeter a) Main calorimeter body b) Three thermometers ii) Gas flow meter a) Main gas flow meter body b) Inlet / outlet nozzles c) Union net with washer for thermometers iii) Pressure governor a) Pressure governor body b) Balancing beam arrangement c) Counter balance tube d) Inlet and outlet union nuts with washers and iv) Jars 2000 ml & 50 ml

PROCEDURE 1. Pour water into the governor till water starts overflowing through the overflow passage. 2. Replace and tighten the over flow nut. 3. Insert three thermometers provided with calorimeter into the rubber corks. 4. Insert rubber corks with thermometers into their places in calorimeter. 5. Insert burner into its support rod in the bottom of the calorimeter and turn the knurled knob so that the burner is fixed tightly. The burner must go into the center of the calorimeter body. 6. Connect the calorimeter, the flow meter and the pressure governor as shown in figure using rubber tubing provided. Do not connect gas supply line. Take care to see that the water regulator of calorimeter is in OFF position.

7. Turn water regulator knob on calorimeter to ON position. Allow water to flow through the calorimeter from overhead tank/ tap. Allow water to flow for 3 to 4 min into laboratory sink, through the calorimeter. 8. Ensure that outlet tap of governor is closed. Connect gas supply line to governor inlet. Remove burner from calorimeter then open governor outlet tap. Allow gas to pass through the burner. 9. Light up the burner by holding a lighted match stick near the mesh at the top. 10. Adjust the air regulator sleeve at the bottom of the burner to get a blue, non-luminous flame. Fix the lighted burner back into position. 11. Adjust water regulator on calorimeter to get a temperature difference 15 0 C between the inlet water & outlet water as indicated by the

of 12 0 C to respective

Thermometers at the top of the calorimeter. 12. Allow 20 to 30 min for outlet water temperature to become steady. 13. Measure the water flow rate with the help of measuring jar. Simultaneously, note the flow meter reading. 14. Note down the inlet &outlet water temperatures. 15. Repeat the test with same volume of gas 3 or 4 times and take average temperatures of inlet and outlet water. CALCULATIONS The formula to be used to calculate the calorific value to the test gas is as follows

CV=

VW x (T2-T1)x1000 VG

Where C.V = calorific value of gas in

Kcal

m3

VG = volume of gas in liters consume during test period Vw = volume of water in liters passed during test period

VALVE TIMING DIAGRAM

VALVE TIMING DIAGRAM ON SECTIONAL MODEL OF 4-STROKE SINGLE CYLINDER DIESEL ENGINE

AIM:-To draw the actual valve timing diagram of a four-stroke single cylinder vertical diesel engine. APPARATUS:-Thread, scale, sectional four stroke single cylinder diesel engine test rig.

THEORY:Valve timing is the regulation of the points in the cycle at which the valves are set to open and close. While the intake and exhaust valves should open, theoretically, at dead centers, almost all SI engines employ an intake and exhaust valves opening and closing a few degrees before dead centers .There are two factors: Mechanical and Dynamic for the actual valve timing to be different from the theoretical valve timing. a) Mechanical factor:The valves of a reciprocating engine are operated by cam mechanism. To avoid noise and wear, the valve should be lifted slowly. For the same reason the valve cannot be closed abruptly else it will bounce on its seat. Then the opening and closing periods are spread over a considerable number of crank shaft degrees. As a result the opening of the valve must commence a head of time at which it is fully opened. The same reason applied for the closing time and valve must close after dead centers. b) Dynamic factor:Besides the mechanical factor the actual valve timing is set taking the dynamic effects of gas flow into consideration. As the piston moves all in the suction stroke, the fresh air is drawn into the cylinder through the inlet valve when the piston reaches the BDC and to move towards TDC in the compression stroke, the inertia of the entering fresh air tends to cause to continue to move in the cylinder after BDC. The exhaust valve is set to open before BDC. By earlier opening of the exhaust valve, the scavenging period is increased. Also earlier opening means that exhaust pressure is higher than the atmospheric pressure, which helps in scavenging process. The exhaust valve is closed a few degrees after TDC. The inertia of the exhaust gases tends to scavenge the cylinder by carrying out a greater mass gas lift in Clearance volume. For some period there is valve overlapping i.e., the kinetic energy of fresh charge helps in forcing out at exhaust gases.

WORKING PRINCIPLE:In a four stroke engine, the thermodynamic cycle of operations is completed in two revolutions of the crank shaft or four strokes of the piston. During the four strokes, there are five events to be completed, viz., suction, compression, combustion, expansion and exhaust. Suction stroke starts when the piston is at TDC and about to move downwards. The inlet valve is open at this time and exhaust valve is closed. Due to the suction created by the motion of the piston towards the BDC, air is drawn into the cylinder. When the piston reaches the BDC the suction stroke ends and the inlet valve closes.

The air taken into the cylinder during the suction stroke is compressed by the return stroke of the piston. During this stroke both inlet and exhaust valves are in closed position. The air is now compressed to the clearance volume. At the end of the compression stroke a metered quantity of fuel (diesel) is injected into the hot compressed air in fine sprays by the fuel injector and it starts burning. During burning process the chemical energy of the fuel is converted into heat energy.

The high pressure of the burnt gases forces the piston towards the BDC. Both the valves are in closed position. Of the four-strokes only during this stroke, power is produced. Both pressure and temperature decreases during expansion.

At the end of the expansion stroke the exhaust valve opens and the inlet valve remains closed. The pressure falls to atmospheric level as a part of the burnt gases escape. The piston starts moving from BDC to TDC and sweeps the burnt gases out from the cylinder. The exhaust valve closes when the piston reaches TDC.

PROCEDURE:1. T.D.C. is identified and marked on the fly wheel with respect to one fixed point in the engine. 2. The circumference of fly wheel is measured using thread and scale. 3. The BDC is marked on the flywheel by taking half the circumference.

4. By slowly cranking the camshaft in the direction of rotation the opening of inlet valve is marked on the fly wheel w.r.t. fixed point when the push rod of inlet valve becomes tight to move. 5. Mark a point on the fly wheel where the inlet valve is completely closed. 6. In the same way mark the points where the exhaust valve open and close. 7. The distance of opening of inlet valve and closing of exhaust valve from TDC and closing of inlet valve and opening of the exhaust valve from BDC are measured using thread and scale. 8. The angles of opening and closing of inlet and exhaust valves are calculated w.r.t. TDC and BDC. PRECAUTIONS:1. The decompression lever must be checked (Should be in disengaged position) when conducting the test. 2. Cranking should be done carefully and slowly so that the salient points are located carefully. OBSERVATIONS: circumference of the fly wheel = 2  R Sl.No.

Distance from nearest dead center

Event

1

IVO

2

IVC

3

EVO

4

EVC

5

FI

IVO

= Inlet valve open

IVC

= Inlet valve close

EVO

= Exhaust valve open

EVC

= Exhaust valve close

FI

= Fuel Injection

Angle

1 cm

= (1 rev of fly wheel / circumference of fly wheel) 0

X cm

= X * (360/ π D) 0

Where D= diameter of the fly wheel in cm

Model Calculations: 1. Inlet valve opens at ……. cm before TDC =….. X 30 = …..0 2. Inlet valve closes at ……. 3. Exhaust valve opens at 4. Exhaust valve closes at 5. Total suction process = IVO to IVC = 6. Total compression = BDC to TDC = 7. Total expansion = TDC to EVO = 8. Total exhaust = EVO to EVC = RESULT:1. Total suction process : 2. Total compression process : 3. Total expansion process : 4. Total exhaust process : 5. Fuel Injection at :

PORT TIMING DIAGRAM

PORT TIMING DIAGRAM ON SECTIONAL MODEL OF 2-STROKE SINGLE CYLINDER PETROL ENGINE AIM: To draw the actual port timing diagram of a two stroke single cylinder petrol engine. APPARATUS: Thread, scale, sectional single cylinder two stroke petrol engine test rig. THEORY: Port timing is the determination of points in the cycle at which the ports are set to open and close. In the ideal cycle inlet, exhaust and transfer port opens and closes at dead centers, but there is a difference between actual and ideal cycle. WORKING PRINCIPLE:In two-stroke engine the cycle is completed in one revolution of the crankshaft. The main difference between two-stroke and four stroke engines is in the method of filling the fresh charge and removing the burnt gases from the cylinder. In the four-stroke engine these operations are performed by the engine piston during the suction and exhaust strokes respectively. In a two-stroke engine, the filling process is accomplished by the charge compressed in crankcase or by a blower. The induction of the compressed charge moves out of the product of combustion through exhaust ports. Therefore, no piston strokes are required for these two operations. Two strokes are sufficient to complete the cycle, one for compressing the fresh charge and the other for expansion or power stroke. The air or charge is inducted into the crankcase through the spring loaded inlet port when the pressure in the crankcase is reduced due to the upward motion of the piston during compression stroke. After compression and ignition, expansion takes place in the usual way. During the expansion stroke the charge in the crankcase is compressed. Near the end of the expansion stroke, the piston uncovers the exhaust ports and the cylinder pressure drops to atmospheric pressure as the combustion products leave the cylinder. Further movement of the piston uncovers the transfer port, permitting the slightly compressed charge in the crankcase to enter the engine cylinder.

PROCEDURE: 1. The circumference of the flywheel is measured using thread and scale. 2. T.D.C. is identified and marked on the flywheel with respect to one fixed point in the engine. 3. The B.D.C. is measured on the fly wheel by taking half of the circumference. 4. Mark various points on the flywheel relative to the opening and closing of ports.

OBSERVATIONS:S.NO

Event

1.

IPO

2.

IPC

3.

TPO

4.

TPC

5.

EPO

6.

EPC

Distance From Nearest dead center

I.P.O

= Inlet port open

I.P.C

= Inlet port close

T.P.O

= Transfer port open

T.P.C

= Transfer port close

E.P.O

= Exhaust port open

E.P.C

= Exhaust port close

1 cm

= (1 rev of fly wheel / circumference of fly wheel) 0

X cm

= X * (360/ ∏ D)

0

Crank angle

Model Calculations: 1. Transfer port opens at ….. cm before BDC = …… 0 before BDC. 2. Transfer port closes at 3. Exhaust port opens at 4. Exhaust port closes at 5. Spark ignition is produced at

RESULT:1. Total suction process: 2. Total compression process: 3. Total expansion process: 4. Total exhaust process

PERFORMANCE TEST ON TWO STAGE RECIPROCATING AIR COMPRESSOR

PERFORMANCE TEST ON TWO STAGE RECIPROCATING AIR COMPRESSOR AIM: To conduct performance test on reciprocating air compressor, to determine its volumetric efficiency and Isothermal efficiency. EQUIPMENT /APPARATUS: 1. Two stage air compressor 2. Tachometer 0-2000 rpm 3. Stop watch SPECIFICATIONS: Make

: Altech

Dia. of low pressure piston

: 70 mm

Dia. of High Pressure Piston

: 50 mm

Stroke

: 90 mm

Operating Pressure

: 8 kgf / cm2

Speed

: 700 rpm

Diameter of orifice

: 20 mm

Power

: 3 HP

Energy Meter Constant

: 300 rev/kwh

DESCRIPTION: The air compressor is a two stage, reciprocating type. The air is sucked from atmosphere and compressed in the first cylinder. The compressed air then passes through an inter cooler into the second stage cylinder, the compressed air then goes to reservoir through safety valve. This valve operates an electrical switch that shuts off the motor when pressure exceeds the set limit. The test consists of an air chamber containing an orifice plate and a u-tube manometer, the compressor and an induction motor. PROCEDURE: 1) Open the discharge valve of the compressor and drain off air completely and Close the valve. 2) Start the compressor, by starting the compressor motor & observe the pressure developing slowly

3) At the particular test pressure, the outlet valve is opened slowly and adjusted so that the pressure in the tank maintained constant. 4) At the particular test pressure, note the following reading (i) Manometer, (ii) Speed of the compressor, (iii) Pressure, (Iv) Time taken for 10 revolutions of energy meter. 5) Close the discharge valve so that pressure increases. 6) Repeat the above procedure for different pressures. 7) Switch off the power supply and stop the compressor.

PRECAUTIONS: 1. Check oil level in the compressor crank case 2. The orifice should never be closed 3. At the end of the experiment the outlet valve at of the reservoir should be opened as the compressor is to be started again at low pressure to prevent undue strain on the piston. OBSERVATIONS:

S.No.

1. 2. 3. 4. 5. `

Gauge Pressure (kgf/cm2)

manometer readings in m of water

h1

h2

hw

Air head causing flow in m of water

Speed

Actual Volume Va m3 / Sec

Theoretical Volume, Vt m3 / Sec

vol

%

S.No.

Gauge Pressure (kgf/cm2)

Motor input=

Time for ‘n’ no: of revolutions of Energy meter ‘s’

3600  n k t

Motor output=

Compress or input=

motorinput

motorinput

0.8

 0.8  0.95

KW

KW

KW

Compress or output= Pa  Va  ln C KW

1. 2. 3. 4. 5.

CALCULATIONS: 1.

Actual Air intake: Manometer reading h1 = …………..mm of water Manometer reading h2 = …………..mm of water Difference in water level, hw =

Equivalent air column, ha =

h1 h2 m of water 1000

hw  Density of water Density of Air



hw  1000 ….m. of air 1.16

Where hw = m. of water column ha =m. of air column w =Density of water in kg/m3 (1000 kg/m3) a =Density of air in kg/m3 (1.16 kg/m3) 2. The actual volume of air compressed, Va = Cd  a  Where Cd=co efficient of discharge for the orifice =0.62 Orifice diameter = 0.02 m Area of orifice, a =

  ( 0.02 )2 4

= …..m2

ha= equivalent air column in ‘m’ of water

2 gha …..m3 / Sec

iso

%

  2   D  L N 4 3. Theoretical volume of air compressed, Vt =   …..m3 / Sec 60

Diameter of piston, D = 0.07 m Stroke length, L = 0.09 m Speed of the compressor, N = ……..rpm

Va  100 Vt 5. Compressor input = Motor input  0.8  0.95 …..KW 4. Volumetric efficiency =

Where Energy meter constant, K= 300 Rev/KWh Time for ‘n’ number of rev.

= t sec

3600 n …….. KW K t

Motor input

=

Efficiency of motor

= 80%

Output of motor

= Motor input  0.8

Belt transmission efficiency = 95 %( assumed) Compressor input

= Motor input  0.8  0.95 …..KW = Pa  Va  ln C

6. Compressor output Compression ratio, C

…….Kw

=

Gauge pressure Atm. pressure Atm. pressure

=

Gauge pressure  1.01325 1.01325

Note: Gauge pressure in Kgf/cm2 Pa= Atmospheric pressure = 101.325 KPa Va= Actual volume of air compressed m3/sec 7. Isothermal efficiency

=

Compressoroutput  100 Compressorinput

Result:

Isothermal Efficiency

Volumetric Efficiency

Model Graphs:

Pressure Pressure

PERFORMANCE TEST ON 4-STROKE, SINGLE CYLINDER DIESEL ENGINE

PERFORMANCE TEST ON 4-STROKE SINGLE CYLINDER DIESEL ENGINE AIM: To conduct a performance test on 4-stroke single cylinder diesel engine under various loads. EQUIPMENT/APPARATUS: 1. 4-Stroke, single cylinder Diesel engine with a rope brake dynamometer Test rig 2. Stopwatch. SPECIFICATIONS: Make

:

Kirloskar

Bore

:

80mm

Stroke

:

110 mm

Rated Speed

:

1500 rpm

Max. B.P

:

3.7KW (5 H.P)

Compression Ratio

:

16.5:1

Orifice Diameter

:

20 mm

Fuel

:

Diesel

Density of Diesel

:

827 Kg/m3

Specific gravity of Diesel

:

0.827

Calorific Value of Diesel

:

43400 KJ / kg

Brake drum diameter

:

360 mm

Rope diameter

:

15 mm

Equivalent diameter

:

375 mm

Coefficient of discharge

:

0.62

DESCRIPTION: This is a water cooled single cylinder vertical diesel engine. It is coupled to a rope pulley brake arrangement to absorb the power produced. Necessary weights and spring balances are included to apply load on the brake drum. Suitable cooling water arrangement for the brake drum is provided. Separate cooling water lines are provided for the engine cooling. Thermocouples are provided for measuring temperature. A fuel measuring system consists of a fuel tank mounted on a stand, burette, and a 3-way cork. Air consumption is measured by using a M.S. tank, which is fitted with a standard orifice and a U-tube water manometer that measures the pressures inside the tank..

THEORY: Single cylinder stationary, constant speed diesel engines are generally quality governed. As such the air supplied to the engine is not throttled as in the case of S.I. engines. To meet the power requirements of the shaft, the quantity of fuel injected into the cylinder is varied by the rack in the fuel pump. The rack is usually controlled by a governor or by a hand. The air flow rate of single cylinder engine operating at constant speed does not vary appreciably with the output of the engine. Since the fuel flow rate varies more or less linearly with output, the fuel air ratio increases with output. Performance tests can be conducted either at constant speed (or) at constant throttle. The constant speed method yields the F.P. of the engine. The engine performance is indicated by the term “efficiency”. Five important engine efficiencies and other related engine performance parameters are: 1. Indicated thermal efficiency

2.Brake thermal efficiency

3. Mechanical efficiency

4.Volumetric efficiency

5. Relative efficiency

6.Mean effective pressure

7. Specific power output

8.Specific fuel consumption

9. Fuel-air ratio

10.Calorific value of the fuel

STARTING THE ENGINE: 1. Engage de-compression lever before cranking. 2. Crank the engine and disengage the de-compression lever. 3. Adjust the governor to attain the rated speed.

PROCEDURE: 1. Open the three way cork so that fuel flows to the engine directly from the tank. 2. Open the cooling water valves and ensure water flows through the engine. 3. Start the engine and allow running on no load condition for few minutes. 4. Load engine by adding weights upon the hanger.

5. Allow the cooling water in the brake drum and adjust it to avoid spilling. 6. Allow the engine to run at this load for few minutes. 7. Note the following readings a) Engine speed. b) W eight on the hanger. c) Spring balance d) Manometer e) Time for 10 cc of fuel consumption 8. Repeat the above procedure at different loads. 9. Stop the engine after removing load on the engine. PRECAUTIONS: 1. Before stating the engine check all the systems such as cooling, lubrication and fuel system 2. Ensure oil level is maintained in the engine up to recommended level always. Never run the engine with insufficient oil. 3. Never run the engine with insufficient engine cooling water and exhaust gas calorimeter cooling water. 4. For stopping the engine, load on the engine should be removed.

GRAPHS 1. T.F.C Vs B .P

4. I th Vs B .P

2. S.F.C Vs B .P

5. m Vs B .P

3. Bth Vs B .P

W1 kg

1

2

3

4

5

6 S kg W kg

RPM

S. N O h1 h2 h1~h2 Sec kg/hr

F.P I.P

kW

B.P

Heat Input

T.F.C

Time for 10 cc of fuel

Air head causing flow (Ha) m of air

Manometer reading

Speed

Load on the brake drum

OBSERVATIONS:

kW kW kW

I.S.F.C

B.S.F.C

kg/kw-h

kg/kw-h

S.NO

Actual volume Mass of air of air Va

Theoretical volume of air Vth

kg/s

m3/s

m3/s

1 2 3 4 5 6

SAMPLE CALCULATIONS: 1. Manometer Reading h1= mm h2 = mm h1~h2 =h= ………….mm of air 2. Air head causing flow: Ha =

h  water = air  1000

3. Engine output (Brake Power) [B.P] W here, N

=

…. m of water

2 NT …… KW 60  1000

= Rated speed ….. Rpm,

W1

= W eight on hanger ………. kg

S

= spring balance reading ……….kg

Re

= Effective brake drum radius = (R + r) … m W here R is Brake drum radius r is Rope radius

W

= Net Load = (W 1-S)  9.81 ……… N

T

= Torque = (W * Re)…………N-m

Time for 10cc of fuel consumption, t = ……. Sec,

Efficiencies

v

 B th

 I th

m

Mass of fuel consumption per sec, mf =

10 Sp.Gravity of diesel  t 1000

kg/sec

4. Total Fuel consumption, TFC = … mf  3600….kg / hr. TFC  CV …….KW 60 60 W here CV is calorific value of Diesel = 43400 KJ / kg

5. Heat Input, HI =

6. F. P = Frictional Power from W illiam’s line diagram. (TFC Vs B.P) 7. Indicated Power, I.P = B.P + F.P T .F .C ……..Kg /Kw-hr B.P T .F .C 9. Indicated specific fuel consumption, ISFC = ……Kg /Kw-hr I .P

8. Brake specific fuel consumption, BSFC =

10. Actual volume of air intake=Va= Cd A0 W here Cd= 0.62 A0= 3.14 X 10-4 m2 11. Mass of air intake ma =

2 g  Ha =

…. m3

  Va …. Kg. air

 D 2  Ls  N 12. Theoretical volume of air = Vth = 4 2  60

m3/Sec

Va  100 % Vth B.P  100 14. Brake thermal efficiency, B th = H .I I .P  100 15. Indicated thermal efficiency, I th = HI 16 . B.P  100 17. Mechanical efficiency, m = I .P MODEL GRAPHS:

SFC Kg/KW-hr

B th, %

13. Volumetric efficiency =

B.P , KW

ith, %

 mech ,%

B.P, KW

B.P, KW

TFC, Kg / hr

B.P, KW

F. P, KW

RESULT:-

B.P, KW

HEAT BALANCE SHEET PREPARATION ON 4STROKE, SINGLE CYLINDER DIESEL ENGINE TEST RIG

HEAT BALANCE SHEET PREPARATION ON 4-STROKE, SINGLE CYLINDER DIESEL ENGINE TEST RIG AIM: To conduct a Heat Balance Test on a 4- stroke single cylinder vertical diesel engine at different loads and to draw up a heat balance sheet on minute basis. EQUIPMENT / APPARATUS: 1. 4-Stroke Single cylinder Diesel engine with a rope brake dynamometer. 2. Tachometer (0-2000 rpm.) 3. Stopwatch. SPECIFICATIONS Make

:

Kirloskar model AVI

Bore

:

80 mm

Stroke

:

110 mm

Rated Speed

:

1 500 r pm

Max. B.P

:

3.7 KW

Compression Ratio

:

1 6 .5 :1

Orifice diameter

:

20 mm

Fuel

:

Diesel

Specific gravity of Diesel

:

0 .8 2 7

Calorific Value of Diesel

:

43400 KJ / kg

Brake drum diameter

:

360 mm

Rope diameter

:

15 mm

Equivalent diameter

:

375 mm

DESCRIPTION: This is a water cooled four stroke single cylinder vertical diesel engine is coupled to a rope pulley brake arrangement to absorb the power produced, Necessary weights and spring balances are included to apply load on the brake drum. Suitable cooling water arrangement for the brake drum is provided. Separate cooling water lines are provided for the engine cooling. Thermocouples are provided for measuring temperature.

A fu e l

measuring system consists of a fuel tank mounted on a stand, burette, and a 3-way cork. Air consumption is measured by using a M.S. tank, which is fitted with a standard orifice and a U-tube water manometer that measures the pressures inside the tank.

Test Rig is provided with exhaust gas calorimeter.

The exhaust gas pipe is

connected to a heat exchanger wherein,the gases are cooled by a cooling water line. Thermocouples are provided to measure the inlet and outlet temperatures of exhaust gas as well as cooling water for the calorimeter. THEORY: Part of the heat supplied to an I.C. engine through the fuel is utilized in doing useful work, and the rest is wasted in overcoming friction, in exhaust gases and in engine cooling water. A statement of the supplied heat, useful work and heat wasted in overcoming friction, exhaust gases, engine cooling is called heat balance sheet. It may be drawn on the basis of unit time or cycle of operation. The heat balance thus gives a picture about the utility of heat supplied through the fuel. The losses depends up on type of the engine, service to which it is employed, load, atmospheric conditions etc. A designer is interested to keep the losses as low as possible in order to maxi mize the rated power. Two important factors that influence the losses are speed and output of an engine. The loss due to friction increases considerably more due to increase in engine speed than by an increase in load. Heat carried away by engine water increases slowly with load while heat carried away by exhaust gases increases abruptly beyond 80% of the rated power output due to higher combustion temperatures, inefficient combustion etc. STARTING THE ENGINE: 1. Engage de-compression lever before cranking. 2. Crank the engine and disengage the de-compression lever. 3. Adjust the governor to attain the rated speed.

PROCEDURE: 1. Open the three way cork so that fuel flows to the engine directly from the tank. 2. Open the cooling water valves and ensure water flows through the engine. 3. Start the engine and allow running on no load condition for few minutes. 4. Load engine by adding weights upon the hanger. 5. Allow the cooling water in the brake drum and adjust it to avoid spilling. 6. Allow the engine to run at this load for few minutes. 7. Adjust the cooling water regulators such that the temperature raise of Cooling water for engine jacket is around 50C and for calorimeter around 250C. 8. Note the following readings a) Engine Speed b) W eight on the hanger c) Spring balance d) Manometer e) Time for 10cc of fuel consumption f) Flow of Cooling water through Calorimeter. g) Flow of Cooling water through Engine. h) Inlet and outlet temperatures of engine cooling water i) Inlet and outlet temperatures of calorimeter cooling water j) Inlet and outlet temperatures of exhaust gases k) Ambient temperate 9. Repeat the above procedure for different loads. 10. Stop the engine after removing load on the engine.

W1 kg

S kg

W kg

Manometer reading

h1

h2

h1-h2

Air head causing flow (Ha) m of air

S. N O

RPM

Load on the brake drum

Speed

OBSERVATIONS: Time fo r 10 cc of fuel

Sec

Engine cooling water temperature I/P

O/P

T1OC

T2OC

O/P

I/P

O/P

Amb ient T em pera ture T 6OC

T3OC

T4OC

T5OC

T6OC

Calorimeter water temperature I/P T10 C

Calorimeter exhaust gases temperature

1 2 3 4 5 6

PRECAUTIONS: 1. Before stating the engine check all the systems such as cooling , lubrication and fuel system 2. Ensure oil level is maintained in the engine upto recommended level always. Never run the engine with insufficient oil. 3. Never run the engine with insufficient engine cooling water and exhaust gas calorimeter cooling water. 4. Before stopping the engine, load on the engine should be removed.

CALCULATIONS: 1. Engine output (Brake Power) [B.P] W here, N

=

2 NT …… kW 60  1000

= Rated speed ….. Rpm,

W0

= W eight of hanger

W1

= W eight on hanger ………. kg

W2

= spring balance reading ……….kg

Re

= Effective brake drum radius = (R+r) … m W here R is Brake drum radius r is Rope radius

W

= Net Load = [(W 1-W 2)+ W 0]  9.81 ……… N

T

= (W * Re)…………N-m

2. Mass of fuel consumption per min, mf =

10 Sp.Gravity of diesel  X 60 kg/ min. t 1000

t = Time for 10cc of fuel consumption……Sec 3. Heat Input, H/I = mf x Cv ……. kJ/ min CV is calorific value of given fuel = 43400 KJ / kg 4. Actual Air intake: Manometer reading h1 = …………..mm of water Manometer reading h2 = …………..mm of water Difference in water level, hw =

h1  h2 1000

Equivalent air column, ha = hw 

……….m of water

Density of water Density of air

= hw 

1000 ...m. of air 1.16

Orifice diameter, d = 0.02 m Area of orifice, a =

 (0.02) 2 ……..m2 4

5. Actual Volume of air intake, Va = Cd  a 

2 gha …… m3 / sec.

Coefficient of Discharge, Cd = 0.62 6. Mass of air intake, ma =  a  Va  60……kg / min Density of air  a = 1.16 Kg/m3

7. Total mass of Exhaust Gas, mg = ma + mf …. kg/min The specific heat of exhaust gas is determined by equating Heat lost by exhaust gas = Heat carried by calorimeter cooling water 8. Heat lost by exhaust gas in calorimeter Heg = mg  Cpg  (T4 – T5)….. kJ/min 9. Heat gained by calorimeter cooling water Hcw= mc w  Cpw  (T3- T1) kJ/min 10. Heat input, HI = mf  CV…… kJ/min 11. Heat Equivalent of B.P, HB.P = B.P  60 ……….. kJ/min 12. Heat lost by exhaust gas, Heg = mg  Cpg  (T4 - T6) ….. kJ/min 13. Heat Carried by engine Cooling water Hew = mw  Cpw  (T2 – T1)… kJ/min 14. Heat unaccounted loss ,Hu = HI – (HBP + Hew + Heg) …… kJ/min HEAT BALANCE SHEET ON MINUTE BASIS: Heat Supplied

kJ/min

%

Heat

Heat distributed

kJ/ min

%

Heat in B.P

B=

B/ A=

Heat carried by engine Cooling

C=

C/ A=

D=

D/ A=

E=

E/ A=

water

supplied by A=

100

the fuel

Heat Carried by exhaust gases

Unaccounted losses (radiation, friction, etc.,) Total RESULT:-

A=

100

A=

100

RETADATION TEST ON 4-STROKE, SINGLE CYLINDER DIESEL ENGINE TEST RIG

RET ARDATION TEST ON 4-STROKE, SINGLE CYLINDER DIESEL ENGINE TEST RIG AIM: To conduct retardation test on 4-stroke, single cylinder diesel engine, to calculate frictional power developed by the engine EQUIPMENT/APPARATUS: 1. 4- Stroke, single cylinder Diesel engine with rope brake drum dynamometer. 2. Stopwatch. SPECIFICATIONS: Make

:

Kirloskar AV

Bore

:

80mm

Stroke

:

110 mm

Rated Speed

:

1500 rpm

Max. B.P

:

3.7KW (5 H.P)

Compression Ratio

:

16 .5:1

Orifice Diameter

:

20 mm

Fuel Oil

:

Diesel

Specific gravity of Diesel

:

0.827

Calorific Value of Diesel

:

43400 KJ / kg

THEORY: The frictional power of an I.C. engine is determined by the following methods a) Willian’s line method b) Indicator area method c) Retardation test d) Motoring test e) Morse test.

RETARDATION T EST: This test involves the method of retarding the engine by cutting the fuel supply. W hen the engine is stopped suddenly its retardation in speed is directly related to the frictional resistance inside the engine. The engine is made to run at no load and rated speed .when the engine is running under steady operating conditions the supply of fuel is cut off and simultaneously the time of fall in speeds by say 20% , 40%, 60% , 80% of the rated speed is recorded. The tests are repeated once again with 50% load on the engine. A graph connecting time for fall in speed (x- axis ) and speed (y – axis ) at no load as well as 50 % load conditions is drawn as shown in fig.

1 00r pm Speed

t3

t2

Time

Graph for retardation Test In this set up to stop the engine running from supply of fuel a valve is provided. As the engine has run for sufficient time, the valve is cutoff and at the same ti me digital timer is switched on. Time for reduction in speed till a particular speed is noted.

PROCEDURE: 1.

Check the fuel and lubricating oil levels.

2. Supply the fuel to the engine. 3. Open the cut off valve to enter the fuel into the engine 4. Now start the engine. 5. Connect the water supply to the engine for cooling 6. After initial worm up the engine, cut of the fuel supply using (cut off valve) at no load. 7. The supply of fuel is cut off and simultaneously the time of fall in speeds by say 20% , 40%, 60% , 80% of the rated speed is recorded by using digital timer and digital RPM indicator. 8. The above procedure is followed for 50% load (i.e 7Kg). Before STARTING THE ENGINE: 1. Check the Diesel Level in the diesel tank. 2. Check the W ater flow through Engine cylinder. 3. First, switch -ON the MCB ( Mains ) of the control panel at the right bottom side . 4. Ensure that water is flowing through the engine. OBSERVATIONS

S. No L e t,

Drop in speed

Time for fall of speed at no load, Sec

1. 2. 3. 4. 5. t2 and t3 be the time of fall at no load and 50% loads ω = Angular velocity in rad/sec dw α= = Angular acceleration in rad/sec2 dt

Time for fall of speed at 7Kg load, Sec

Torque, T= Moment of inertia ×Angular acceleration dw T=I× dt Moment of inertia of rotating parts is constant throughout the test dw ( I = mk2 ) T=mk2 × dt T (eq1) dw=  dt I Now integrating the equation 1 between the limits ω1 and ω2 w2

t2

 dw =  w1

t1

T  dt I

www12 = T t 2  t1  I Let, TF be the frictional torque and T L be the load torque . At no load condition both frictional and load torques will act. Hence at no load condition T ω2 – ω1= F t 2  0 (eq 2) I Where TF = frictional torque Similarly for load condition

TL t 3  0 I where TL = load torque t3 (Tf+TL) = (ω2 – ω1)mk2 ω2 – ω1=

t 3

(Tf+TL) = Tf×t2

(eq 3)

( fr o m e q 2 )

t 2 TF  TL = t3 I t2 T = 1+ L t3 TF t t TL = 2 3 TF t3 t TF = TL× 3 t 2  t3 PRECAUTIONS: 1. Don’t start or stop the engine with load. 2. Don’t forget supply of cooling water to the engine. 3. After starting the engine remove the handle carefully from the shaft.

4. Take the time carefully for dropping of the speed

SAMPLE CALCULATIONS: = M  r  9.81 N m

Load Torque on drum (TL)

M- Mass in Kg of spring Balance r - Radius of torque arm =

Frictional load Torque ( TF )

=

t3  TL t 2  t3

t 2 t3 Frictional power (F.P) =

Brake power B.P =

Mechanical Efficiency =

RESULT:-

2    N  TF 60

2  N T 60

W

B.P  100 I .P

0.36  0.015 m 2

= Retardation time at no load = Retardation time at 50% load

W

MORSE TEST ON 4-STROKE, 4- CYLINDER PETROL ENGINE TEST RIG

MORSE TEST ON 4-STROKE, 4-CYLINDER PETROL ENGINE AIM: To conduct Morse test on a 4-stroke multi cylinder (4 – cylinder) petrol engine to establish friction power & mechanical efficiency EQUIPMENT REQUIRED: 1. 4-stroke,4 -cylinder petrol engine with a hydraulic dynamometer with provision to cut off ignition to each cylinder independently. 2. Tachometer (0-2000 rpm). 3. Stop watch SPECIFICATIONS: Make

:

Premier

No of cylinders

:

4

Bore

:

68 mm

Stroke

:

75 mm

Rated Speed

:

1500 r p m

B.P

:

7.35 Kw (10 Hp)

Fuel

:

Petrol

Specific Gravity of petrol

:

0 .7 1 6

Calorific value of petrol

:

47100 KJ/kg

Compression Ratio

:

7 .8 :1

Orifice diameter

:

20 mm

DESCRIPTION: The test rig consists of a multi cylinder petrol engine coupled to a hydraulic dynamometer. The engine is 4-cylinder, 4-stroke vertical engine developing 7.35Kw at 1500 rpm. This type of engine is best suited for automobiles which operate at varying speed. The engine is fitted on a rigid bed and is coupled through a flexible coupling to a hydraulic dynamometer that acts as the loading device. All the instruments are mounted on a suitable panel board. Fuel consumption is measured with a burette and a 3-way cork which regulates the flow of fuel from the tank to the engine. Air consumption is measured by using a M.S. tank, which is fitted with a standard orifice and a U-tube water manometer that measures the pressures inside the tank.

To conduct Morse test, an arrangement is provided to cut off the ignition to each spark plug. THEORY: The frictional power of an I.C. engine is determined by the following methods: f) William’s line method g) Indicator area method h) Motoring test i) Morse test The Morse test is applicable for multi cylinder petrol (or) diesel engine. The engine is run at the rated speed and the output is measured. Then one cylinder is made not to fire by Cut-off ignition,

under this condition, the other cylinder operates the engine. As a

consequence the speed of the engine falls. The output is measured by restoring the speed to the original value by decreasing the load. The difference between two outputs gives the indicated power of the cylinder cutout. Thus the indicated power of all cylinders can be evaluated and by deducting brake power from the indicated power of all cylinders, the frictional power of the engine can be estimated. Let I.P of cylinders 1, 2, 3 & 4, be I.P1, I.P2, I.P3&I.P4 respectively. Let Frictional power of the engine be ‘F.P’ at a given load. Thus for a four cylinder engine. I.P1+I.P2+I.P3+I.P4 – F.P = B .P ………. (1) Where B.P= Brake Power of engine when all cylinders are working. When first cylinder is cut out I1 = 0, but Friction power of the engine remains at F.P Then I.P2 + I.P3 + I.P4 - F.P = B.P1 …….. (2) By (1) – (2) we have

I.P1 = B.P – B.P1

Similarly

I.P2 = B.P – B.P2 I.P3 = B.P – B.P3 I.P4 = B.P – B.P4

I.P. of the engine

I.P = I.P1 + I.P2 + I.P3 + I.P4

F.P. of the engine

F.P = I.P – B.P

STARTING THE ENGINE: 1. Disengage the clutch and start the engine using the ignition key. 2. Engage the clutch slowly. 3. Adjust the throttle valve, so that the engine attains rated speed. PROCEDURE: 1. Open the three- way cork so that fuel flows to the engine directly from the tank 2. Open the cooling water valves and ensure water flows through the engine 3. Open the water line to the hydraulic dynamometer 4. Start the engine and allow to run on No Load condition for few minutes 5. Operate the throttle valve so that the engine picks up the rated speed 6. Load the engine at full load and maintain the speed at rated rpm i.e., 1500 rpm by adjusting the throttle and dynamometer loading wheel. 7. Allow the engine to run at this load for a few minutes. 8. Cut-off ignition to the first cylinder, and thus speed is decreased. 9. Without disturbing the throttle valve position, decrease the load on the engine, until the original speed is restored. 10. Note the dynamometer reading, restore the ignition to the first cylinder 11. Repeat the above procedure by cutting off ignition to each of the cylinders. 12. Note the dynamometer readings for each cylinder when they are cut -off. 13. Engine stopped after removing the load. PRECAUTIONS: 1. Before stating the engine check all the systems such as cooling , lubrication and fuel system

2. Ensure oil level is maintained in the engine upto recommended level always. Never run the engine with insufficient oil. 3. Never run the engine with insufficient engine cooling water and exhaust gas calorimeter cooling water. 4. For stopping the engine, load on the engine should be removed. OBSERVATIONS:

Rated Speed=1500 rpm S. No

Condition

Dynamometer load (W) Kg

1

All cylinders working

W=

2

1st cylinder cut-off

W 1=

3

2nd cylinder cut-off

W 2=

4

3rd cylinder cut-off

W 3=

5

4th cylinder cut-off

W 4=

B.P, KW

I.P, KW

SAMPLE CALCULATIONS: `B.P =

2  N  T ……. KW 60000

(where T= torque = W ×R)

B.P1=

2  N  T1 ……. KW 60000

(R=320mm)

B.P2=

2  N  T2 .…… KW 60000

B.P3=

2  N  T3 …… KW 60000

B.P4=

2  N  T4 …… KW 60000

I.P1 = B.P-B.P1 ……

KW

F.P KW

I.P2 = B.P-B.P2……

KW

I.P3 = B.P-B.P3 ……

KW

I.P4 = B.P-B.P4…..

KW

I.P = I.P1+I.P2+I.P3+I.P4 . .KW

F.P = I.P-B.P……

Kw

Frictional power, F.P =

KW

Mechanical efficiency  m

=

RESULT:-

B .P  100 I .P

PERFORMANCE TEST ON 2- STROKE, SINGLE CYLINDER PETROL ENGINE TEST RIG

PERFORMANCE TEST ON 2- STROKE, SINGLE CYLINDER PETROL ENGINE TEST RIG AIM: To conduct a load test on a single cylinder, 2- Stroke petrol engine and study its performance under various loads. EQUIPMENT / APPARATUS: 1. 2-Stroke, Single Cylinder Petrol Engine with Resistance load bank 2. Tachometer 3. Stop Watch SPECIFICATIONS: Make

:

Bajaj

Stroke

:

57mm

Bore

:

57mm

Rated R.P.M

:

3000rpm

Output

:

3 hp

Fuel

:

Petrol

Specific Gravity of petrol :

0.716

Calorific Value of petrol

:

47100 KJ/Kg

Lubrication

:

3% mixture of self mixing oil

and

petrol DESCRIPTION: This Petrol engine is an air cooled, single cylinder, Vertical, 2-stroke engine. The engine is kick started. The petrol engine is coupled to a Resistance load dynamometer to absorb the power produced. The dynamometer is provided with load controller switches for varying the load. Fuel consumption is measured with a burette and a stop watch. A threeway cork, which regulates the flow of petrol from the tank to the engine.

PROCEDURE: 1. Open the three way cork so that fuel flows to the engine directly from the tank. 2. Start the engine and allow running on no load condition for few minutes. 3. Load the engine, by switching on the resistance from the load bank. 4. Note the following readings a) Speed. b) Voltage and Current. c) Time taken for 10 cc of petrol consumption. 5. Repeat the above procedure at different loads. 6. Stop the engine after removing load on the engine PRECAUTIONS 1. Use only petrol mixed with 2T oil – use higher oil /petrol ratio to compensate for the lack of cooling air ( air flow over the engine while moving ) in the stationary test rig 2. Changing gear oil regularly. 3. Never run the engine with insufficient fuel

SFC Kg/KW-hr

B th, %

MODEL GRAPHS:

B.P, KW

ith, %

 mech ,%

B.P , KW

B.P, KW

B.P, KW

TFC, Kg / hr F. P, KW

1 2 3 4

5

6

h2

h1~h2 cm

kg / h r

Heat Input

T.F.C

Time for 10 cc of fuel Se c

kW

F.P

(amp)

h1

B.P

(Volts)

RPM

I.P

Current

Manometer reading

Air head causing flow (Ha) m of air

Voltage

Speed

S.NO

Load on the resistance load bank

B.P, KW

kW

kW

kW

I.S.F.C

B.S.F.C

Actual volume of air Va

kg/kw-h

kg/kw-h

m3/s

S. NO

Mass of air

Theoreti cal volume of air Vth

kg/s

m3/s

Efficiencies

Vol

Bth

1 2 3 4 5. 6. SAMPLE CALCULATIONS:

h  water …………. m of air air  100

1. Air head causing flow =

2. Actual volume of air intake=Va= Cd A0 W here Cd= 0.62 A0= 3.14 X 10-4

2 gHa =

 D 2  Ls  N 3. Theoretical volume of air = Vth = 4 m3/Sec 60 4. Volumetric efficiency =

Va  100 Vth

Q  0.71 m/sec 1000 Q = 10 cc/ sec

5. Mass of fuel = t

6. Brake power B.P =

g = 80 %

V I

g

 100

W

7. Brake specific fuel consumption, BSFC = 8. Indicated power I.P = B.P + F.P

T .F .C ……..Kg /Kw-hr B.P

 I th

m

9. Indicated specific fuel consumption, ISFC = 10. Brake thermal efficiency, B th =

B. P

mf  Cv I .P 11. Indicated thermal efficiency, I th = m C f

12. Mechanical efficiency, m =

RESULT::-

B.P  100 I .P

v

T .F .C ……Kg /Kw-hr I .P

PERFORMANCE TEST ON REFRIGERATION TEST RIG AIM: To conduct a performance test on a refrigerator with Freon 12 refrigerant to determine the coefficient of performance. EQUIPMENT /APPARATUS: 1. Refrigeration test rig 2. Measuring jar 3. Stop watch SPRCIFICATIONS: Make

:

Altech

Compressor

:

1 / 3 Ton of refrigeration

Condenser

:

Air Cooled

Expansion Device

:

i ) Capillary Tube ii) Solenoid Valve

Evaporator Coil

:

Immersed in water Tank of stainless steel

Refrigerant

:

Freon – 22.

DESCRIPTION: The test rig consists of a hermetically sealed compressor. The compressed refrigerant from the compressor is sent to an air cooled condenser and the condensate in liquid form is sent to the expansion valve /capillary tube for throttling. Due to throttling temperature of the refrigerant falls and the cold refrigerant absorbs heat from the water in the evaporator tank. The refrigerant is then returned to the compressor. A suitable filter and a transparent rotameter to visually observe the liquid. Refrigerant is fitted in the refrigerant line from condenser to evaporator. A thermocouple is provided to measure the temperature of the water in the evaporator tank. An energy meter is provided to measure the energy input to the compressor. Suitable pressure gauges are provided at the compressor inlet (evaporator outlet),

Condenser inlet (compressor outlet), condenser outlet (before throttling) and evaporator inlet (after throttling) to study the refrigeration cycle operating between the two pressures. A thermostat is provided for the cutting off the power to compressor when the water temperature reaches asset value. A voltmeter and an ammeter are provided to monitor the inlet power supply. A voltage stabilizer is provided for the protection of compressor. Provisions are provided in the refrigerant pipe lines for charging the test rig with additional refrigerant if necessary. Additional 4 No’s of thermocouples are fitted at the condenser and evaporator inlet and outlet for studying the temperature at the 4 points in the refrigeration cycle THEORY: A refrigerator consists of a compressor connected by suitable pipelines to a condenser, a capillary tube and an evaporator. Refrigerant (Freon12) in vapor state from the evaporator is compressed in the compressor and sent to the condenser. Here it condenses’s in to liquid and it is then throttled. Due to throttling temperature of refrigerant drops and the cold refrigerant passes through the evaporator absorbing heat from the object to be cooled. The refrigerant is then returned to the compressor and the cycle is completed PROCEDURE: 1. Fill up the evaporator tank with a know quantity of water (say 10-15 litres). 2. Switch on the compressor. 3. After about 5 minutes (after steady state had set in) note the initial energy meter reading and water temperature in the evaporator. 4. After a known period of time, say 30 minutes note down the energy meter reading and water temperature. 5. Calculate the actual COP. 6. Note the Refrigerant pressures at compressor inlet (evaporator outlet), condenser inlet (compressor outlet), condenser outlet (before throttling) and evaporator inlet (after throttling) using the pressure gauges.

7. Note the Temperatures at compressor inlet (evaporator outlet), condenser inlet (compressor outlet), condenser outlet (before throttling) and evaporator inlet (after throttling) using the thermocouples provided. 8. Draw pressure- enthalpy diagram. 9. Calculate the theoretical COP 10. Calculate the relative cop PRECAUTIONS: 1.

Before noting the water temperature, physically Stir the water to ensure that the temperature is uniform in the water tank

2.

Since COP depends upon the evaporator temperature and condenser temperature, the calculated COP (which is an average value) will be different for varying evaporator, condenser and water temperatures.

3.

When the compressor turns off (by the thermostat) or is switched off manually, do not turn on the power immediately. Allow a few minutes for the pressure in the compressor inlet and outlet to equalize. The time delay provided in the voltage stabilizer is for this purpose only. Immediate starting will cause under load on the compressor and may even lead to burn out

SAMPLE CALCULATIONS: ACTUAL COP: Quantity of water in evaporator tank, m =…………….. Kg Time taken for experiment, t =………………..hours Initial temperature of water,T0 =………..0C Final temperature of water, Tf = ………..0C Initial energy meter reading, E0 = …………Kwh Initial energy meter reading, Ef = ……….Kwh Refrigerating effect per hour = Energy input

=

m(T0 - T f ) t E f  Eo t

…..KW

Actual Coefficient of Performance, COP =

refrigerating effect Energy input

Actual COP = THEORETICAL COP: Theoretical COP is calculated from the pressure measured from pressure gauges (evaporator and condenser pressures) and the temperatures measured from four thermocouples located at four points of the thermodynamic cycle (refer figure 1).

S.No

Reading

Temperature, 0

1

Condenser inlet

2

Condenser outlet

3

Evaporator inlet

4

Evaporator outlet

C

Pressure, Pressure, Psi

Bar

Note: Bar = Psi +1 14.5 From P-h diagram for R-12

Enthalpy of refrigerant at evaporator outlet, (before compression) h 1 = ….Kj/Kg Enthalpy of refrigerant at condenser inlet, (after compression) h 2 = … …..Kj /kg Enthalpy of refrigerant at condenser outlet, (before throttling) h 3 = ………..Kj/Kg Enthalpy of refrigerant at evaporator inlet, (after throttling) h 4 = …………….Kj/Kg

Theoretical COP =

(h1  h4 ) (h2  h1 ) Actual COP

Relative COP = Theoritical COP

RESULT :

ASSEMBLY AND DISASSEMBLY OF IC ENGINES

Aim: To study the different types of I.C engines, various parts of I.C engines, cycles of operation etc., Introduction: Any type of engine, which derives heat energy from the combustion of fuel and converts this energy into mechanical work, is termed as a heat engine. These are classified as

1. External Combustion engines (E.C) 2. Internal Combustion engines (I.C) If the combustion of fuel takes place outside the working cylinder then the engine is called External Combustion Engine. If the combustion takes place inside the working cylinder the engine is called Internal Combustion Engine. The most common examples of E.C engines are steam engines and steam turbines. I.C engines are used in scooters, cars, locomotives, agriculture and earth moving machinery, power generation and in many industrial applications. The advantages of I.C engines over E.C engines are high efficiency, simplicity, compactness, light weight, easy starting and low cost. Classification of I.C Engines: I.C Engines are classified as follows 1. According to the fuel used: Petrol engine, Diesel engine and Gas engine. 2. According to cycle of operations: 2-stroke engine and 4-stroke engine 3. According to the method of ignition: Spark ignition (S.I) engine, Compression Ignition (C.I) engine. 4. According to the number of cylinders: single cylinder engine, multi cylinder engine. 5. According to the method of cooling the cylinder: Air-cooled engine and Water-cooled engine. 6. According to the arrangement of cylinder: Horizontal engine, Vertical engine and Radial engine.

I.C Engine Parts and their Function: An I.C engine consists of many different parts, however the main components are described below.

1.Cylinder: The heart of the engine is the cylinder and its primary function is to contain the working fuel under pressure and the secondary function is to guide the piston. To avoid the wear of the cylinder block cylinder liners are provided. The cylinder is made of Gray Cast Iron. 2.Cylinder Head: One end of the cylinder is closed by means of a removable cylinder head, which usually contains the inlet valve for admitting fuel and exhaust valve for discharging products of combustion. The valves are operated by means of cams geared to the engine shaft. The cylinder head is usually made of cast iron or alloy cast iron containing Nickel, Chromium and Molybdenum.

3.Piston: The piston used in I.C engines is usually of trunk type and are open at one end. The main function of the piston is to receive the impulse from the expanding gas and transmit the energy to the crankshaft through the connecting rod. At the same time the piston must also disperse a large amount of heat from the combustion chamber to the cylinder walls. Pistons are made of cast iron or Aluminum alloys for lightness. 4. Piston Rings: These are circular rings and made of special steel alloys, which retain elastic properties even at high temperatures. The piston rings are housed in the circumferential grooves provided on the outer surface of the piston. Generally there are two sets of rings mounted on the piston. The function of the upper rings is to provide air tight seal to prevent leakage of the burnt gases into the lower portion. Similarly the function of the lower rings is to provide effective seal to prevent leakage of the oil into the engine cylinder. 5.Connecting Rod: One end of the connecting rod is connected to the piston through piston pin and the other end is connected to the crank through the crank pin. The usual cross section of connecting rod is I-section or H-section and these are made of carbon steel or alloy steel. The main function is to transmit force from the piston to the crankshaft. Moreover, it converts reciprocating motion of the piston into the circular motion of the crank shaft in the working stroke.

6.Crank shaft: crank shaft consists of the shaft part which revolve in the main bearing. The big end of the connecting rod is connected to the crank pin. The crank web connects to the crank pin and shaft part. The function of the crankshaft is to transform reciprocating motion into rotary motion. Crankshafts are made of carbon steel. 7.Cam shaft: It is driven from the crank shaft by timing gears on a chain. It operates the intake valve and the exhaust valve through the cams and followers, push rods and rocker arms. 8.Fly wheel: It is a big wheel mounted on the crank shaft whose function is to reduce the vibrational fluctuations. It stores excess energy during power stroke and releases during the other strokes. Cycle of operation: The number of strokes of the piston required to complete the cycle varies with the type of engine. There are two types of engines namely four stroke cycle engine and two stroke cycle engine. A four-stroke cycle engine requires four strokes of piston or two revolutions of the crankshaft to complete one cycle. In a two-stroke engine there are two strokes of the piston or one revolution of the crankshaft to complete one cycle. The four stroke and two stroke engines are further divided into petrol and diesel engines according to the type of fuel used. Four stroke petrol / Diesel engine: The four stroke engine utilizes four strokes namely suction stroke, compression stroke, power stroke, and exhaust stroke for completion of a cycle and it has two valves, one for the inflow of the air fuel mixture or pure air and the other for the exhaust of burnt gases. At the start of the working cycle, the piston is at the top dead center position (TDC). As the piston begins its outward stroke the inlet valve opens and a mixture of fuel and air in metered proportions flows in, If the engine is of the spark ignition type only, air flows in through the inlet valve. When the piston starts moving back into the cylinder, both inlet and exhaust valves closes. The air or air fuel mixture thus trapped between the piston and the cylinder head is now compressed until the piston reaches the TDC at the end of compression stroke. Just before the end of the compression stroke of the piston ignition occurs due to a spark in case of petrol engines or a spray of oil injected into the cylinder in case of diesel engines. In either case, the thermal energy

released makes the compressed gas expand rapidly and drives the piston outwards. The resulting stroke is called the power stroke. As the piston completes the power stroke and returns T.D.C, the exhaust valve opens and the burnt exhaust gases in the cylinder are driven out. At the instant the, piston reaches the TDC position, the exhaust valve closes and the inlet valve will be ready to open, starting a new cycle of operation again. Two stroke S.I / C.I engines: The two stroke engines utilize only two strokes (Compression stroke and power stroke) for the completion of a cycle. In two-stroke engine there are two ports. One in the inlet and one in the outlet for gasses. The opening and closing of the ports depends on the position of the piston in the cylinder. The piston is at T.D.C both outlet and transfer ports are closed when the compressed air fuel mixture or air in the cylinder is about to be ignited by either a sparking device or fuel injection. When piston travels back during the power stroke, it uncovers the exhaust port first and a moment later the transfer port. The opening of the transfer port puts the cylinder in contact with the crankcase containing a slightly compressed air fuel mixture or air. The incoming fresh charge helps in driving out the burnt gases through the exhaust port. The head of the piston being shaped to assist this scavenging action. As the piston returns into the cylinder, it covers both the transfer and exhausts ports and compresses the trapped gas until it reaches the T.D.C position. At the same time a fresh charge is drawn into the crankcase through the inlet port. A cycle is thus completed with one power stroke in every two-piston strokes. In a two stroke engine a small amount of burnt gas always remains in the cylinder along with the fresh charge when the piston covers the ports and starts compressing the gases trapped inside. Moreover, since both transfer port and exhaust ports are simultaneously open during part of the piston stroke, some of the incoming fresh charge escapes with the burnt gases. As a result the efficiency of a two stroke engine is lower, further two stroke engines consume large amounts of lubricating oil compared with four stroke engines and are likely to be noisier because of the sudden opening of the exhaust ports. Valve Timing Diagram: The valve timing diagram shows the position of the crank when the various operations, i.e. suction, compression, expansion and exhaust begin and end.

The valve timing is the regulation of the positions in the cycle at which the valves are set to open and close. Since the valves requires a finite period of time to open or close without a rupture, a slight ‘lead’ time is necessary for the proper operation. The design of valve operating can provide for smooth transition from one position to the other, while cam setting determines the timing of the valve. Theoretically it may be assumed that the valves open and close and spark (or injection of fuel) occurs at the engine dead centers. However, in actual operation the valves do not operate at it center positions but operate some degrees away on either side of the dead centers. The opening occurs earlier and the exhaust continues even at later crank angles. The ignition is also timed to occur earlier. The injection of fuel in the case of diesel engine is also timed to occur in advance of the completion of compression stroke. The timing of these events referred in terms of crank angles from dead center positions, is presented on a valve-timing diagram. The correct timings are of fundamental importance for the efficient and successful running of the I.C engine.