List of Experiments
1) To study different components and working of a four stroke petrol engine.
2) To study the construction and working of four stroke diesel engine.
3) To study different components and working of a two stroke petrol Engine.
4) To study the construction and working of two stroke diesel engine.
5) To study the construction and working of a carburetor.
6) To study the construction and working of fuel injection pump and injector.
7) By load test to check the performance of a diesel generator set.
8) To perform emission test on petrol engine and record the readings.
EXPERIMENT NO- 1
Aim: To study different components and working of a four stroke petrol engine.
Tools & Equipments: Hand Tools, Engine.
Theory: In four stroke engine, we get one power in two revolution of crankshaft. The air fuel mixture is sent in combustion chamber a spark is, compressed and ignited with a spark plug. The expansion takes place and gases expand pushing piston downward.
Cylinder Head: It is the top portion Of engine. In this two or three valves and one spark plug is fitted per cylinder.
Cylinder Block: It is fitted below the cylinder head. In this the piston reciprocates
Crankcase: It is the lowest portion of engine and is filled with oil. It also houses Crankshaft.
Valves and camshaft: Inlet and exhaust valves act as a gate for inlet fresh mixture and for exhaust for throwing out exhaust gases.
Piston: Piston reciprocates in block and is fitted with piston rings to prevent Leakage of hot gases during expansion.
Connecting rod: It is fitted between piston and crankshaft, converts reciprocating motion in rotary motion.
Crankshaft: This shafts rotates by connecting rod and transmits power to transmission system.
Spark plug: Hot type spark plug is fitted to initiate spark. The spark plug gap is maintained 0.7mm.
Working: The working of a 4 stroke engine can be understood by knowing the four strokes.
1) Inlet Stroke: In this the piston moves from top dead centre to bottom dead centre. The inlet valve is opened by cam mechanism. The inlet valve is opened by cam mechanism. The air fuel mixture is drawn inside due to vacuum as long as piston moves to bottom dead centre.
2) Compression stroke: The piston from BDC starts moving to TDC. At this point inlet valve is closed and air fuel mixture is compressed in the ratio of 1:7. The temperature increases to 250 degree. Just before the piston reaches TDC the spark plug generates a spark.
3) Expansion Stroke: The air fuel mixture burns and hot gases start expanding. Both inlet and exhaust valves are in closed condition. There is a rapid rise in temperature and pressure. The piston receives a thrust and piston moves from TDC to BDC with a great amount of power. This stroke is called power stroke. This power from piston is transmitted to crankshaft by connecting rod.
4) Exhaust Stroke: During this stroke the piston starts moving from BDC to TDC. The exhaust valve is opened and the upward movement of piston pushes out the product of combustion from the engine through the exhaust valve into the atmosphere. The piston again reaches the TDC and again the inlet stroke is repeated completing the one full cycle.
1) How much temperature is developed in S.I. Engine after compression stroke?
2) How much is the spark plug gap is maintained during service?
3) What do you mean by hot and cold type spark plug?
4) What is the spark timing in S.I. Engine?
5) How will you differentiate between inlet and exhaust valve.
6) What is O.H.C.?
I EXPERIMENT NO- 2
Aim: To study the construction and working of four stroke diesel engine.
Tools and equipments: Hand tools, engine.
Theory: The four stroke diesel engine is very much similar to four stroke petrol engine except that only atmospheric air is drawn in inlet stroke instead of air fuel
mixture as in petrol engine. The spark plug is missing and injector is fitted for fuel supply.
Important Components: As in petrol engine it also has cylinder head, cylinder block ,crankcase, piston, connecting rod, valves. The new parts are fuel injection pump and injectors fitted on cylinder head.
Working: The working of petrol engine can be understood with the help of four strokes.
1) Inlet stroke: As we crank the engine by hand or self starter the piston moves from T.D.C. to B.D.C. The inlet valve is opened by cam mechanism. The suction is generated in cylinder and fresh air is sucked inside after filtering from air cleaner. As piston crosses D.D.C. the inlet valve is closed. The exhaust valve is kept closed
in this stroke.
2)Compression stroke: The piston starts from B.D.C. to T.D.C.
Now both the valves are closed. The trapped air is compressed in the ratio of 1:22. The temp. of air raises approx. to 500 Celsius. The piston reaches to T.D.C.
3) Power stroke: At the end of the compression stroke, fuel at high pressure 250 kg/cm2 is injected in combustion chamber by atomizer. In practical fuel is injected20
degree before piston reaches to T.D.C. to reduce delay period. The explosion takes place and hot gases expand creating a thrust on the crown of the piston. Both the valves are in closed condition in this stroke. Due to thrust the piston moves from T.D.C. to B.D.C. generating a power.
4) Exhaust Stroke: At the end of the power stroke, burnt gases are inside cylinder and the same is needed to be thrown out. The exhaust valve is opened and piston moves upward from B.DC.to T.D.C. sweeping out of burnt gases out of the engine through the silencer.
1) Check air cleaner.
2) Check valve clearance.
3) Check engine oil.
4) Check coolant level.
1) What are the additional parts in diesel engine compared to petrol engine?
2) What is compression ration of four stroke diesel engine?
3) What is the grade of engine oil used in this engine?
4) How much is the temp. developed in combustion chamber?
5) What is the ratio between crankshaft and camshaft gear?
Aim: To study the construction and working of two stroke petrol engine.
Equipments: Hand tools, engine.
Important components: It consists of cylinder block, cylinder piston, piston, rings, connecting rod, crankshaft etc.
Working: There is a complete of cam and valve mechanism. The piston covers both the ports. There is an inlet port, exhaust port, and one or two transfer ports. The piston covers both the ports in the cylinder when it is at top dead centre. The four operations are 1) Charge induction 2) air compression and introduction of spark 3) expansion and exhaust stroke.
During the upward motion of the piston, there is suction in the crankcase through the inlet port. Thus for full 180 degree of the crankshaft rotation, the suction will continue below the piston in the crankcase. Above the piston the compression will start only after both the ports has been covered by the piston thus trapping the charge above it. On further upward motion of the piston the air above piston is compressed. Just before the end of the compression spark is generated by spark plug and explosion in combustion chamber takes place. The hot gases start expanding and we get power stroke. The piston starts moving downward.
On downward movement of the piston the air below it gets start compressing. Just before BDC the exhaust port gets exposed and hot gases start escaping from exhaust port. After some time the transfer port get exposed and fresh air fuel mixture moves inside combustion chamber.
Piston movement Process
1) From B.D.C to T.D.C. suction in crankcase below piston And compression of charge above Piston.
2) From T.D.C to B.D.C. Compressed charge ignited and Power stroke takes place and Exhaust stroke also just at the end Of B.D.C. Fresh charge enters in Combustion chamber through Transfer port.
1) Absence of cam mechanism.
1) How much temp is developed at the end of the compression stroke in two stroke petrol engine?
2) How to differentiate between two stroke and four stroke petrol engine from appearance?
3) When piston moves from T.D.C to B.D.C which port is exposed first?
4) What are hot and cold type spark plugs?
5) What are the drawbacks of 2 stroke petrol engine?
Aim: To study the construction and working of 2 Stroke diesel Engine.
Equipments required: Hand Tools
Theory: In a 2 Stroke diesel engine the cycle is completed in one revolution of crankshaft. The main difference between the 2 Stroke and 4 Stroke engine is the method of filling fresh charge and removing the burnt gases from the cylinder. In 4 Stroke engine these operations are performed by the engine piston during the suction and exhaust strokes respectively, but in 2 stroke engine the filling process is accomplished by the charge compressed in the crankcase. The induction of the compressed charges moves out the product of combustion through ports. Therefore no piston strokes are required for these 2 operations. Two strokes are sufficient to complete the cycle, one for compressing the fresh charge and the other for expansion/ power stroke.
Working: The piston moves from BDC to TDC. The fresh charge is sucked inside the crankcase. The piston is moving upward and compressing the charge above piston. Just near TDC the diesel is injected in combustion chamber and air fuel burns, hot gases expand and power stroke takes place. The piston with a force moves from TDC to BDC. At this time the fresh air inside crankcase is compressed by downward movement of piston. Before piston reaches BDC the exhaust port is exposed and then the transfer port is exposed. The transfer port is at a lower height than exhaust port to avoid mixing of fresh and exhaust charges. The compressed air enters the cylinder pushing the burnt gases out of the exhaust port.
The top of the piston is made of a particular shape that facilitates the deflection of fresh charges upward and thus avoids its escape along with the burnt gases. After reaching the bdc when the piston moves up, it firsts closes transfer port and then the exhaust port. The upward movement of piston compresses air above piston simultaneously the re is a fall of pressure in crankcase creating g a partial vacuum and sucking of fresh charge takes place.
1) Absence of cam mechanism.
2) Injector in place of spark plug.
3) Carburettor is replaced by fuel injection pump.
1) What is compression ration of 2 stroke diesel engine?
2) Why T.P is at lesser height than E.P?
3) Where are such engines used?
4) How do we lubricate such engines?
5) What is the main drawback of this engine?
EXPERIMENT NO- 5
Aim: To study the construction and working of a carburetor.
Tools and Equipments: Carburetor, screw driver, hand tools.
Important components: carburetor, slow jet, main jet, floats.
Theory: In order to have the engine produce the greatest amount of power most economically it is important that the fuel which is to be the source of energy, be made into a most combustible condition before being charged in the engine. The condition of this air fuel mixture will therefore have a very great affect on the engine performance and fuel consumption and for the reason the carburetor is used.
Construction and working:
Carburetor is a device which is used for atomizing and vaporizing the fuel and mixing it with air in varying proportion, to suit the changing operating conditions of the engine. Atomization is the breaking of liquid fuel into very small particles so that is properly mixed with air, but vaporization is the change of state of fuel from liquid to vapor. Carburetor performs both processes of atomization and vaporization of fuel. The carburetor consists of five circuits as described below.
1) Float Circuit: It consists of float and float chamber. Here petrol is supplied to the float chamber from the fuel tank through the filter and fuel pump. The arrangement in float chamber is such that when the petrol reaches a particular level , the needle valve blocks the inlet passage and stops the supply of fuel and as the petrol level falls below the float descends down and inlet passage opens again. The petrol is supplied to the chamber again. Thus a constant fuel level is maintained in the float chamber. The float chamber supplies the fuel to the main jet. The level of the fuel in the float chamber is kept slightly below the top of the jet. The difference of level between the top of the jet and level of fuel is 1 to 1.5mm. An air vent is also provided in the float chamber in order to provide continuous air pressure above petrol in float chamber otherwise the fuel lock can take place.
2) Venturi circuit: The main body consists of a narrow passage at its centre. This passage is called as venturi. One end of the carburetor is mounted on the inlet manifold of the engine. On the other end an air cleaner is fitted on the carburetor. The carburetor can of downward draft, upward draft, side draft type depending upon the direction of flow of air and mounting.
During the suction stroke air is drawn through the carburetor. The velocity of air increases as it passes through the venturi. Due to this the pressure at the venturi decreases. Hence the outlet of the main jet which is located at the venturi is in zone of low pressure. The fuel is sucked up and sprayed and mixed with air and the mixture is supplied to the inlet manifold of the engine.
3) Acceleration circuit: It consists of a throttle valve placed between the mixing chamber and the intake manifold of the engine. It controls the supply of air. As the throttle valve is opened by pressing accelerator, the amount of air flow increase and the velocity of air in the passage increases subsequently the pressure in the venturi reduces more and thus reduction of air pressure increases the amount of fuel discharging out from the main jet.
4) Idle circuit: For a low speed operation or for idling, the engine requirement a rich Mixture is required. To accomplish this, an idling circuit is used.
The low speed circuit is comprised mainly of the low speed jet, air bleeder and idle port. Its function is to supply gasoline to the engine at low speed. Since
the accelerator is not pressed while idling, the throttle valve is practically close.
Therefore the speed of the air flowing through the venturi will be low so that the main jet will not supply fuel. However, the engine suction will create a large vacuum under the throttle valve. For running the engine an idle port is provided below the throttle which supplies air and fuel. The amount of this mixture can be adjusted by rotating
idle mixture screw.
5) Choke circuit: During starting in cold weather, the engine requires extra rich mixture. For this purpose a choke valve is provided which closes the air passage and a limited supply of air is supplied making the mixture rich. After warm up ensure that the choke valve is in closed condition. Normally it is operated manually.
Inspection and observation:
1) Inspect float height
2) Wear of needle valve
3) Clean main jet
4) Clean float chamber
1) Why air vent is provided in float chamber?
2) What do you mean by venturi?
3) What is most economic ratio of fuel?
4) How many jets are provided in carburettor?
5) What type of carburettor is fitted normally in cars?
Aim: To study the construction and working of fuel injection pump and injector.
Equipment required: Hand Tools, fuel pump, injector.
Theory: Fuel injection pump is used in high compression engine. The fuel injection pump controls the amount of fuel delivered and injects fuel at right time.
Important components: F.I.P. consists of the following parts. P is a rack connected to governor mechanism or accelerator through linkages. Q is the quadrant of the gear to which the hollow cylinder portion with the slots at the bottom is attached. R is a plunger which reciprocates by cam and can be turned or rotated by rack and quadrant.
S is the barrel in which the plunger reciprocates V is a non return valve and seat. W is the delivery pipe from the pump connected to the injector.
Working: The fuel pump is rotated by engine power through a gear mounted on the camshaft. This movement of camshaft is converted in reciprocating movement of plunger. The plunger has a helical groove and a vertical slot. The purpose of the helical groove is to change the quantity of fuel as per demand.
When the plunger moves from bottom to top it covers the inlet port of the barrel, hence the fuel inside the barrel is trapped. Further movement of plunger will compress the fuel. The valve opens against the spring. At high pressure injector opens and fuel is injected in combustion chamber. After some travel this helical and vertical groove will coincide with the inlet port. At this point the port gets exposed and built up pressure reduces suddenly. The position of helix and the time duration during which the fuel was continuously injecting determines the amount of fuel to be injected.
The high pressurized fuel developed at FIP is fed to the injector by connection L . As shown in fig this fuel passes through a drilled hole in the body. This high pressure fuel strikes at the bottom of the nozzle valve. The nozzle valve lifts up lifting the spindle D against the spring force E. As the valve lifts up the fuel escapes through a very fine drilled hole. The fine drilled hole acts as a orifice and atomizes the fuel.
1) In which engine FIP is used?
2) what is the pressure developed in high pressure pipes?
3) What happens when spring looses tension?
4) What happens when leak off pipe is choked?
5) What is the injection timing of diesel engine?
EXPERIMENT NO -7
Aim: By load test to check the performance of a diesel gen-set.
Equipments Required: Genset, Voltmeter, Ammeter, Tachometer, Stopwatch, water, water load resistance, Burette, Diesel tank and diesel.
Speed: 1500 R.P.M.
Output: 7.5 KVA
Volts : 240
Cycles/ Sec: 50 Single phase
Procedure: Fill up the tank with the diesel. Start the engine and open the fuel supply from the fuel tank through 50 ml burette. Start the stop watch. When the fuel level in the burette reaches zero reading. Note down the time taken for 50 ml fuel consumption for a particular load on the engine. Load is applied by a load resistance. Note the voltmeter and ammeter reading also the r.p.m. for a particular load. Change the load on engine and note down the time taken for 50 ml fuel consumption. Also note down the voltmeter and ammeter readings for this particular load and repeat the same procedure to take more readings.
Calculate the load in KW, Fuel consumption in gm/sec, specific fuel consumed and thermal efficiency. Draw graphs between load vs. fuel consumed, Load vs. specific fuel consumed and load vs. fuel efficiency.
OBSERVATIONS AND CALCULATIONS:
|S.No||Current (Amps)||Voltage (Volts)||RPM||Fuel
|Time (sec)||Fuel Consumed
Calorific Value of Diesel =44,000 KJ/Kg
Density of fuel =0.82 gm/sec
Fuel Consumed =50×0.82=41gm
FUEL CONSUMPTION (mf) :
1) mf = 50×0.82 = 0.1745 gm/sec
2) mf = 50×0.82 = 0.2278 gm/sec
3) mf = 50×0.82 = 0.3083 gm/sec
4) mf = 50×0.82 = 0.4227 gm/sec
5) mf = 50×0.82 = 0.4659 gm/sec
6) mf = 50×0.82 = 0.5467 gm/sec
7) mf = 50×0.82 = 0.6833 gm/sec
nth = Output = V x I
Input C.V. x mf
2) nth = 1.20 x 1000 = 0.1197 = 11.97 %
44000 x 0.2278
3) nth = 2.38 x 1000 = 0.1754 = 17.54 %
44000 x 0.3083
4) nth = 3.57 x 1000 = 0.1919 = 19.19 %
44000 x 0.4227
5) nth = 4.28 x 1000 = 0.2088 = 20.88 %
44000 x 0.4659
6) nth = 4.40 x 1000 = 0.1829 = 18.29 %
44000 x 0.5467
7) nth = 4.66 x 1000 = 0.1550 = 15.50 %
44000 x 0.6833
SPECIFIC FUEL CONSUMPTION ( KG/KW-Hr) :
1) 0.1745 x 3600 = infinity
2) 0.2278 x 3600 = 0.6834 Kg/ Kw-hr
1.20 x 1000
3) 0.3083 x 3600 = 0.4663 Kg/ Kw-hr
2.38 x 1000
4) 0.4227 x 3600 = 0.4262 Kg/ Kw-hr
3.57 x 1000
5) 0.4659 x 3600 = 0.3919 Kg/ Kw-hr
4.28 x 1000
6) 0.5467 x 3600 = 0.4473 Kg/ Kw-hr
4.40 x 1000
7) 0.6833 x 3600 = 0.5279 Kg/ Kw-hr
4.66 x 1000
Maximum thermal efficiency is found to 20.88 at a load of 4.28 Kw. The various characteristics can be seen from the graphs.
EXPERIMENT NO -8
Aim: To perform emission test on petrol engine and record the readings.
Equipments: Petrol engine, Gas analyzer.
Related theory: The importance of checking smoke is because the pollutants present in smoke adversely affect health. Before measuring we should know the main pollutants released by petrol engine.
Hydrocarbon: HC emissions are caused by incomplete combustion. These emissions are actually molecules of the unburned gasoline.
Carbon monoxide: CO is a by product of combustion. CO is a poisonous chemical compound of carbon and oxygen. It forms in the engine when there is not enough oxygen to combine with the carbon during combustion.
Oxides of nitrogen: The formation of oxides of nitrogen is the result of high combustion temperature at above 1370 degree. Nitrogen present in the air reacts with oxygen to form NOX.
Carbon dioxide: CO2 although is not a pollutant however it has been linked with another environment concerns like global warming.
Important checks: Before running engine or measuring pollutants ensure air cleaner ok fuel setting ok, engine compression ok.
1) Make sure that exhaust analyzer is fitted with clean filter elements, dust filter and strainer.
2) Connect power cables
3) Turn switch on and the analyzer will go on stand by mode.
4) Press the purge key and keep the probe exposed to clean air.
5) Allow system to warm for about 10 minutes.
6) Check that any mark is not flashing in screen and then press stand by.
7) Do not leave the probe on shop floor.
8) Unplug the drain separator from the sample inlet and let the analyzer take clean air.
9) Press the auto zero key until the meter reading is zero.
10) Plug the drain separator into o the sample inlet.
11) Insert the probe in exhaust silencer and Press the measure key.
12) Read the value on the meter.
13) Remove the probe from the tail pipe and leave it exposed in clean air until the meter shows zero. Press the purge key.
|Pollutant gas||At zero load||At 1000kw load||At 2000kw load||At 3000kw loat|
1) Why probe is not left on ground?
2) What is euro 3 norms?
3) What are the harmfull effects of gases?
4) How can we reduce pollutants?
5) On what principle gas analyzer works?