Basics of Two-stroke cycle, How Marine Engine Works?

 Marine main propulsion engine is 2 stroke CI engines i.e., the engine completes its one cycle in 2 strokes .

 2 stroke cycle = 2 stroke of the piston in one cycle

                        = One Compression stroke and One Power stroke.

                        =  Piston going up + piston going down

                       =   One complete  revolution 


> Compression Stroke

             When the piston goes downward exhaust valves open up and the scavenge port is uncovered which allows the fresh air to enter through the scavenge port and  clean the cylinder of the exhaust gases from the previous cycle. The piston then travels upwards closing the scavenge ports and exhaust valves and starts compressing the air. air. At the end of the upward stroke, the air pressure in the cylinder rises from 33 to 43 bar and temperature rises from 660 to 780 deg C. Just before TDC fuel is injected to the hot compressed air, it reaches its self ignition temperature and gets ignited

> Power Stroke

           The combustion causes the expansion o f gases, which push the piston downwards towards BDC. The piston being pushed downwards by the combustion gases is doing work and hence, the stroke is called the Power or Expansion stroke.

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