INTERNAL COMBUSTION ENGINES:
Heat Engines:
Any kind of engine or machine that derives heat from the combustion of fuel or
any other supply and converts this energy into mechanical work is termed as an engine.
Heat engines could also be classified into 2 main categories as follows :
1. External Combustion Engine.
2. combustion Engine.
1. External Combustion Engines (E.C. Engines):
In this case, the combustion of fuel takes place outside the cylinder as just in case of steam engines
where the warmth of combustion is used to come up with steam that is employed to maneuver a piston in a very cylinder. different samples of external combustion engines ar hot air engines, turbines, and closed-cycle turbines. These engines are usually required for driving locomotives, ships, generation of electrical power, etc.
2. Combustion Engines (I.C. Engines):
In this case, the combustion of the fuel with O of the air happens at intervals the cylinder of the
engine. the interior combustion engines cluster includes engines using mixtures of flammable gases and air, called gas engines, that exploitation lighter liquid fuel or spirit called gas
engines and people exploitation heavier liquid fuels, called oil compression-ignition or diesel engines.
Development of I.C. Engines:
Many experimental engines were made around 1878. the primary very victorious engine
did not seem, but till 1879, once a German engineer Dr. Otto engineered his notable Otto gas
engine. The operation cycle of this engine was based mostly upon principles 1st ordered down in 1860 by a French engineer named Bea Delaware Rochas. the bulk of contemporary I.C. engines operate in step with these principles.
The development of the renowned internal-combustion engine began regarding 1883 by Rudoff Diesel. though this differs in several necessary respects from the otto engine, the in operation cycle of contemporary high-speed Diesel engines is thermodynamically terribly the same as the Otto cycle.
Completely different elements of I.C. Engines:
1.Cylinder
2.Plate three.
3.Piston
4.Piston rings five.
5.Pin half dozen. rod
7.Rotating shaft eight.
8.Crank
9.Engine bearing
10.Crankcase eleven.
11.Regulator twelve.
12.Governor
13.Valves and valve in operation mechanism.
B. elements for gas engines solely
1. Spark plugs two. mechanical device three.
2.Fuel pump.
C. elements for internal-combustion engine solely
1. Fuel pump. 2. Injector.
Spark Ignition (S.I.) Engines:
These engines may go on either four-stroke cycle or 2 stroke cycle, majority of them, of
course, operate a four-stroke cycle.
Four-stroke gas engine:
illustrates the varied strokes/series of operations that crop up in a very four-stroke
petrol (Otto cycle) engine.
Suction stroke:
Throughout the suction stroke, a mix of air and fuel (petrol) is sucked through the body of the water valve (I.V.). The valve remains closed throughout this operation.
Compression stroke:
Throughout compression stroke, each the valves stay closed, and the
pressure and temperature of the mixture increase. close to the top of the compression stroke, the fuel is ignited by means that of an electrical spark within the plug, inflicting the combustion of fuel at the moment of ignition.
Working stroke:
Next is that the operating (also referred to as power or expansion) stroke. throughout this stroke, each the valves stay closed. close to the top of the growth stroke, solely the valve opens and also the pressure within the cylinder at this stage forces most of the gases to go away the cylinder.
Exhaust stroke:
Next follows the exhaust stroke, once all the remaining gases ar drove away from the cylinder, whereas the body of the water valve remains closed and also the piston returns to the highest dead center. The cycle is then recurrent.
Two-stroke gas engine:
In 1878, Dugald-clerk, a British engineer introduced a cycle that might be completed in
two strokes of the piston instead of four strokes as is that the case with the four-stroke cycle engines. The engine exploitation of this cycle was referred to as 2 stroke cycle engines. during this engine suction and exhaust strokes, are eliminated. Here rather than valves, ports ar used.
The exhaust gases are driven out from the engine cylinder by the recent modification of fuel getting into the cylinder nearly at the top of the working stroke. The cylinder L is connected to a closed crank chamber C.C. throughout the upward stroke of the piston M, the gases in L ar compressed and at an equivalent time recent air and fuel (petrol) mixture enters the crank chamber through the valve V.
once the piston moves downwardly, V closes and also the mixture in the crank chamber is compressed. The piston is moving upwards and is compressing associate explosive modification that has antecedently been provided to L. Ignition takes place at the end of the stroke.
The piston then travels downwardly because of the growth of the gases and close to the top of this stroke the piston uncovers the exhaust port (E.P.) and also the burnt exhaust gases escape through this port.
The transfer port (T.P.) then is uncovered straight off, and the compressed charge from the crank chamber flows into the cylinder and is deflected upwards by the hump provided on the top of the piston. it should be noted that the incoming air gas mixture helps the removal of gases from the engine-cylinder; if just in case these exhaust gases don’t leave the cylinder, the recent charge gets diluted and potency of the engine can decrease.
The piston, however, starts moving from bottom dead center (B.D.C.) to prime dead center (T.D.C.) and also the charge gets compressed once E.P. (exhaust port) and T.P. are lined by the piston; therefore the cycle is recurrent. The power obtained from a two-stroke cycle engine is in theory doubly the ability available from a four-stroke cycle engine.
Compression-Ignition (C.I.) Engines:
The operation of C.I. engines (or diesel engines) is practically the same as those of S.I.
engines. The cycle in both types consists of suction, compression, ignition, expansion, and
exhaust. However, the combustion process in a C.I. engine is different from that of an S.I. an engine as given below :
In the C.I. engine, only air is sucked during the stroke and the fuel is injected in the cylinder
near the end of the compression stroke. Since the compression ratio is very high (between 14: 1 to
22: 1), the temperature of the air after compression is quite high. So when fuel is injected in the
form of a spray at this stage, it ignites and burns almost as soon as it is introduced. The burnt
gases are expanded and exhausted in the same way as is done in an S.I. engine.
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