Department of Mechanical Engineering
Thermal Engineering Lab
EXPERIMENT NO: 1
a) Valve timing Diagrams of I.C. Engines
AIM:
To draw the valve timing diagram of the four stroke cycle diesel engine.
Apparatus:
i) Four stroke cycle diesel engine
ii) Measuring tape
iii) Chuck
iv) Piece of paper
THEORY:-
The diagram which shows the position of chuck of four stroke cycle engine at the beginning and at the end of suction, compression and expansion and exhaust of the engine are called as valve timing diagram.
The extreme position of the piston at the bottom of the cylinder is called bottom dead centre (BDC) in the case of centre (ODC) the extreme position of the piston at the top of the cylinder is called top dead centre (TDC) in the case of horizontal engine this is known as inner dead centre (IDC).
In an ideal engine the inlet valve open at TDC and closed at BDC. The exhaust valve opens at BDC and closes at TDC the fuel is injected in to the cylinder when the position is at TDC and at the end of the compression stroke but in actual practice it will differ.
Inlet Valve opening and closing:
In an actual engine the inlet valve begins to open 500 to 200. Before the position 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 TDC. If the inlet valve is allowed to close at BDC the cylinder would receive less amount of air then its capacity and the pressure at the end of the suction will be below the atmospheric pressure to avoid this the inlet valve is kept open for 250 to 400 after BDC.
Exhaust valve opening and closing:
Complete clearing of the burned gases from the cylinder is necessary to taken in move air in to the cylinder to achieve this the exhaust valve opens at 350 to 450 before BDC and closes at 100 to 200 after the TDC. It is clear from the diagram for certain period. Both inlet and exhaust valve remains in open condition the crack angle for which both are the valves are open called as overlapping period this overlapping is move than the petrol engine.
Fuel valve opening and closing:
The fuel valve opens at 100 to 150 before TDC and closes at 150 to 200 after TDC this is because better evaporation and mixing fuel.
PROCEDURE:
1. Remove the cylinder head cover and identify the inlet valve, exhaust valve and piston of the particular cylinder.
2. Mark the BDC and TDC position of the flywheel. This is done by rotating the crack in the usual direction of the rotation and observe the position of the flywheel when the piston is moving downwards at which the piston begins to move in opposite direction i.e from down to up word direction make the mark on the flywheel with reference to fixed point on the body of the engine that point is the BDC for the flywheel and mark the point from BDC at a distance of the half of the circumference that point is TDC and is diametrically opposite to the BDC.
3. Insert the paper in the tappet clearance of both inlet and exhaust valves.
4. Slowly rotate the crank until the paper in the tappet clearance of the inlet valve is gripped make the mark on flywheel against fixed reference this position represents the inlet valve open (IVO) measure the distance from TDC and tabulated the distance.
5. 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 closing (IVC) measure the distance.
6. Rotate the crank further till the paper in the tappet clearance of the exhaust valve is gripped reference this position represents exhaust valve open (EVO) measure the distance from BDC and tabulated it.
7. Rotate the crank further, till the paper in the tappet clearance of exhaust valve is just free to move make the marking on flywheel against fixed reference this position represents the fixed reference this position represents the exhaust valve close (EVC) measure the distance from TDC and tabulated it
8. Then converted the measure distance in to angle decrease.
FORMULAE USED:-
Θ = Length / Circumference x 3600
Observation &Tabulation:-
Sl. No. / Event / Position of crank to TDC or BDC / Distance in CM / Angle in degree1 / IVO / Before TDC
2 / IVC / After BDC
3 / EVO / Before BDC
4 / EVC / After TDC
Result:- The valve timing diagram for the given four stroke diesel engine was drawn.
EXPERIMENT NO: 1
b) Port timing Diagrams of I.C. Engines
AIM:
To draw the Port timing diagram of the four stroke cycle diesel engine.
Apparatus:
v) Four stroke cycle diesel engine
vi) Measuring tape
vii) Chuck
viii) Piece of paper
THEORY:-
The diagram which shows the position of chuck of four stroke cycle engine at the beginning and at the end of suction, compression and expansion and exhaust of the engine are called as valve timing diagram.
The extreme position of the piston at the bottom of the cylinder is called bottom dead centre (BDC) in the case of centre (ODC) the extreme position of the piston at the top of the cylinder is called top dead centre (TDC) in the case of horizontal engine this is known as inner dead centre (IDC).
In an ideal engine the inlet valve open at TDC and closed at BDC. The exhaust valve opens at BDC and closes at TDC the fuel is injected in to the cylinder when the position is at TDC and at the end of the compression stroke but in actual practice it will differ.
Inlet Valve opening and closing:
In an actual engine the inlet valve begins to open 500 to 200. Before the position 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 TDC. If the inlet valve is allowed to close at BDC the cylinder would receive less amount of air then its capacity and the pressure at the end of the suction will be below the atmospheric pressure to avoid this the inlet valve is kept open for 250 to 400 after BDC.
Exhaust valve opening and closing:
Complete clearing of the burned gases from the cylinder is necessary to taken in move air in to the cylinder to achieve this the exhaust valve opens at 350 to 450 before BDC and closes at 100 to 200 after the TDC. It is clear from the diagram for certain period. Both inlet and exhaust valve remains in open condition the crack angle for which both are the valves are open called as overlapping period this overlapping is move than the petrol engine.
Fuel valve opening and closing:
The fuel valve opens at 100 to 150 before TDC and closes at 150 to 200 after TDC this is because better evaporation and mixing fuel.
PROCEDURE:
1. Remove the cylinder head cover and identify the inlet valve, exhaust valve and piston of the particular cylinder.
2. Mark the BDC and TDC position of the flywheel. This is done by rotating the crack in the usual direction of the rotation and observe the position of the flywheel when the piston is moving downwards at which the piston begins to move in opposite direction i.e from down to up word direction make the mark on the flywheel with reference to fixed point on the body of the engine that point is the BDC for the flywheel and mark the point from BDC at a distance of the half of the circumference that point is TDC and is diametrically opposite to the BDC.
3. Insert the paper in the tappet clearance of both inlet and exhaust valves.
4. Slowly rotate the crank until the paper in the tappet clearance of the inlet valve is gripped make the mark on flywheel against fixed reference this position represents the inlet valve open (IVO) measure the distance from TDC and tabulated the distance.
5. 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 closing (IVC) measure the distance.
6. Rotate the crank further till the paper in the tappet clearance of the exhaust valve is gripped reference this position represents exhaust valve open (EVO) measure the distance from BDC and tabulated it.
7. Rotate the crank further, till the paper in the tappet clearance of exhaust valve is just free to move make the marking on flywheel against fixed reference this position represents the fixed reference this position represents the exhaust valve close (EVC) measure the distance from TDC and tabulated it
8. Then converted the measure distance in to angle decrease.
FORMULAE USED:-
Θ = Length / Circumference x 3600
Observation &Tabulation:-
Sl. No. / Event / Position of crank to TDC or BDC / Distance in CM / Angle in degree1 / IVO / Before TDC
2 / IVC / After BDC
3 / EVO / Before BDC
4 / EVC / After TDC
Result:-
The valve timing diagram for the given four stroke diesel engine was drawn.
EXPERIMENT NO: 2
PERFORMANCE TEST ON A FOUR STROKE PETROL ENGINE
AIM: To Conduct Performance Test on 4-stroke single cylinder petrol engine and draw performance curves.
APPRATUS REQUIRED:- Four Stroke Engine with electrical loading, Stop watch etc,.
THEORY:-This engine works on 4 strokes which are suction, compression, power and exhaust stroke. Valves are used in this engine to allow and exhaust the working fluids. Using dynamometers can do the performance of the engine. Various types of dynamometers are available, which are rope brake dynamometer, electrical dynamometer, and hydraulic dynamometer.
OBSERVATIONS:
1. Cylinder bore D : 70 mm
2. Stroke length L : 66.7 mm
3. Water density ρw : 1000 kg/m3
4. Calorific value of petrol CV : 41,000 Kj/kg
5. Acceleration due to gravity g : 9.81 m/sec 2
6. Petrol density ρf : 0.8 Kg/lit
7. Air Density ρa : 1.2 Kg/ m3
PROCEDURE:
a. Check all electrical connections and check petrol and oil in the engine.
b. Open valves of 3 way manifold, make fuel flow to engine directly
c. With the help of rope start the engine
d. Wait until it stabilizes for rated speed
e. Now take readings of manometer, temperature, Voltage and current
f. Close valve of 3 way block, now fuel flows to engine from burette
g. Note down time taken for 10 cc of fuel
h. Now switch ON first two switches for load.
i. Note down readings of fuel Consumption, Volts, Current, and Temperature.
j. Continue loading the engine step by step for different load condition, by switching on the load switches.
k. Tabulate all the readings and calculate brake power, Brake thermal efficiency, Brake specific fuel consumption and plot the graph Qin v/sBP,SFC v/s BP, hb v/s BP.
FORMULAE USED:
01. Mass flow rate of Air: Ma in kg/s
Ma = Ao x Cd x ra x Ö (2 x g x Ha) kg/s
Where : Area of Orifice, Ao = {p /4 x do2} m2
do (Orifice diameter) = 20 mm ( 0.02 m)
Head of Air, Ha = {(h1 ~ h2) x rw} /ra m
h1 and h2 from manometer in m
ra = Air density = 1.2 kg/m3
rw = Water density = 1,000 kg/m3
Cd = 0.64
02. Mass of fuel consumed: mf in kg/s
mf = [V x rf] / [1000 x t] kg/s
Where V = fuel consumed in cc (10cc)
rf = Fuel density = 0.85 kg / lit
t = Time in seconds for 10cc of petrol
03. BRAKE POWER: BP
BP = (V x I) / (1000 x ηg) in kW
Where V = Voltage, Volts
I = Current, amps
ηg = Generator Efficiency = 0.68
04. HEAT SUPPLIED Qi in kW
Qi = mf x C V kW
Where C V is calorific value of the fuel =41,500 kJ/kg
05. AIR FUEL RATIO : A/F
A/F = ma / mf
06. BRAKE THERMAL EFFICIENCY: hb in %
hb = {BP / Qi } x 100 %
07. SPECIFIC FUEL CONSUMPTION: SFC
SFC = [mf x3600] / [BP] kg/kWh
TABULAR COLUMN:
SLNo / Manometer Reading / Speed
in RPM / Voltage
In volts / Current in amps / Time for 10cc fuel consumption in sec / Air-Fuel ratio / Brake power
In kW / Brake Thermal efficiency / Specific fuel consumpion
h1 / h2 / N / V / I / t / A/F / BP / hb / BSFC
1.
2.
3.
RESULT:
Performance Test on 4-stroke single cylinder petrol engine and draw performance curves.
verall heat transfer coefficient of the composite wall.
EXPERIMENT NO: 4
Evaluation of engine friction by conducting Morse test on 4-Stroke Multi cylinder engine.
AIM: To Conduct Performance Test and Morse Test on 4-stroke Multi cylinder (3) petrol engine and draw performance graphs.
APPARATUS: Four stroke multi cylinder (3) petrol engine with hydraulic loading, stop watch.
THEORY:
Indicated power is the power produced inside the cylinder due to burning of the fuel. IP can be obtained by knowing the mean effective pressure or conducting Morse test. Morse test is applicable to multi cylinder petrol or diesel engine. In petrol engine IP can be obtained by knowing the IP of the individual cylinder by cut off the power supply to the spark plug of that cylinder. Friction power (FP) can be calculated after knowing IP and BP of engine when all cylinders are working.
DESCRIPTION OF THE TEST RIG:
The engine is four stroke, three cylinder, water cooled petrol driven automobile (Maruti) engine coupled to a hydraulic dynamometer mounted on strong base, and is complete with air, fuel temperature, load and speed measurement system the specifications are