Two stroke & Four stroke Diesel Engine

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1. GOVERMENT ENGINEERING COLLEGE GANDHINAGAR GROUP : MANIYAR DHRUMIL JOSHI HITANSH DIVISON : EC-A2

2. -: TOPIC :- What is I.C. Engine? Basic parts of I.C. Engine. What is stroke ? What is 2-stroke & 4-stroke ? Working of 2-stroke Diesel Engine. Advantages & Disadvantages. Working of 4-stroke Diesel Engine. Advantages & Disadvantages. Comparison of 2-stroke & 4-stroke cycle engine.

3. What is I.C. Engine ? I.C. Engines means internally combustion engines. All those engines in which combustion of the fuel release heat energy inside the engine cylinder are known as “Internal Combustion Engines”. These engines are widely used as prime movers and also in road vehicles, locomotives, industrial applications. Examples : Petrol engines, Diesel engines and Gas engines.

4. Basic parts of I.C. Engine ? Cylinder Cylinder head Piston Connecting rod Crank shaft Cam shaft Fly wheel

5. 1. Cylinder :- It is the important part of this engine in which the piston moves up and down in order to develop power. 2. Cylinder head :- It is fitted one end of the cylinder and act as a cover to close the cylinder. It contains : Inlet valve & Outlet valve. Spark plug or injector. 3. Piston :- It is considered as the heart of I.C engine. Whose main function is to transmit the force exerted by the burning of charge to the connecting rod.

6. 4. Connecting rod :- It is the link between the piston and crank shaft. Whose main function is to transmit force from the piston to the crank shaft. 5. Crank shaft : - It is considered as the backbone of an I.C Engine. Whose function is to convert reciprocating motion of piston in to the rotary motion with the help of connecting rod. 6. Cam shaft :- The shaft which has cams for the opening and closing of inlet & outlet valves.

7. 7. Fly wheel :- It is the big wheel mounted on the crankshaft whose function is to maintain speed at constant. The constant speed is done by storing excess energy during power stroke up to returning of other power stroke.

8. What is Stroke ? Reciprocating motion, used in reciprocating engines and other mechanisms, is back and forth motion. Each cycle of reciprocation consists of two opposite motions : there is a motion in one direction, and then a motion back in the opposite direction. Each of these is called a “Stroke”.

9. What is 2-stroke & 4-stroke? A two stroke diesel engine is an internal combustion engine that completes the process cycle in one revolution of the crank shaft. Thus, one power stroke is obtained in each revolution of the crank shaft. A four stroke diesel engine is an internal combustion engine that completes the process cycle in two revolution of the crank shaft. Thus, one power stroke is obtained in each two revolutions of the crank shaft.

10. 2-Stroke Diesel Engine :- Working :- In this engine the piston moves down on the power stroke. It first uncovers the exhaust port. The cylinder pressure drops to atmospheric pressure as the combustion products leave the cylinder. Further movement of piston uncovers the transfer port. As soon as the transfer port opens, the slightly compressed air in the crank case enters into cylinder . The piston is so shaped that the fresh air will sweep up to the top of the cylinder and push out the remaining gases through exhaust port.

11. During compression stroke, first the transfer port closes and compression of the air begins. This movement lowers the pressure into the crank case. Thus, the atmospheric air enters through inlet valve in the crank case. Before the end of the compression stroke the fuel is injected from the injector into hot air. The ignition of the fuel starts and combustion goes as long as the nozzle is open. When the piston is near the BDC , the piston uncovers exhaust port which permits the gases to floe out of cylinder.

12. Advantages :- One cycle completed in every revolution of crankshaft. Compact, required less space & lighter weight. Design & construction is simpler than 4-stroke engine. Easy to manufacture & low cost. Disadvantages :- High fuel consumption. Compression ratio & thermal efficiency is less than four stroke engine. Consumes more lubricating oil. More wear & tear of moving parts hence it gives loud noise.

13. 4-Stroke Diesel Engine :- Working :- The working of diesel engine based on diesel cycle or constant pressure combustion cycle as the combustion of fuels place at constant pressure. The cycle is completed in 4 strokes. During suction stroke, the inlet valve remains open & exhaust valve remains closed. The piston moves from TDC to BDC. Air from the atmosphere is drawn into the cylinder. During compression stroke, inlet and outlet valve remains closed. Piston moves from BDC to TDC. The air compressed to high pressure & temperature.

14. During expansion stroke, both valve remains closed and the piston moves from TDC to BDC. Fuel injected in the cylinder causes the combustion of the fuel. During exhaust stroke, the exhaust valve remains opened and inlet valve remains closed. Piston moves from BDC to TDC. The products of combustion are swept out through the exhaust valve.

15. Advantages :- High torque output Smooth running Lower emissions output Higher horse power availability Heavier construction Disadvantages :- Heavy in weight More moving parts Exhaust smell Creates more pollution than petrol engine.

16. Comparison :- Two Stroke Engines Four Stroke Engines The cycle of operation is completed in two strokes. The cycle of operation is completed in four strokes. Engines are lighter, compact and require less space. Engine are heavier, larger and require more space. Simple construction. Complicated construction. High mechanical efficiency. Low mechanical efficiency. Produce more noise. Produce less noise. Moving parts are more. Moving parts are less. Better balancing. Balancing is a problem. Gives low vibrations. Gives more vibrations. Compression ratio is low. Compression ratio is more.

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