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WORKING OF FOUR STROKE CYCLE (DIESEL) C.I ENGINE

 



The working of Four stroke CI Engine is Similar to that of  SI Engine except. Here, fuel injector is placed instead of spark plug and only air is sucked into the cylinder during suction strokes. The operation will be,

1. Suction Stroke : 

During the suction stroke, the piston moves from TDC to BDC. The inlet valve is in open condition where as exhaust valve is closed. When the piston moves from top to bottom, The fresh air is admitted inside the cylinder through inlet valve. 

2. Compression Stroke :

During the compression stroke, both the inlet and exhaust valves are closed. The piston moves from BDC to TDC to compress the air. In case of  CI engine, the compression ratio varies from 12 to 18. The pressure at the end of compression is about 3500 to 4000 kN /m2. The temperature of the compressed air reaches 600 to 700*C 

3. Power Stroke :

In this stroke also, both the inlet and exhaust valves are in closed position. The fuel injector opens just before the beginning of the third stroke, it injects the fuel in atomized form. Ignition of the fuel takes place automatically by means of high pressure and temperature air. The pressure and temperature further will increase due to the combustion, it pushes the piston towards down. thus it produces power stroke. 

4. Exhaust Stroke : 

During this stroke, inlet valve is closed and the exhaust valve is opens. The piston moves from BDC to TDC. It blows out the burnt gases from the cylinder. Thus, one cycle of operation is completed and repeated again and again in the same manner. 



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