Types of diesel engine and TWO STROKE cycle of marine diesel engine.

Types of diesel engine:

Based on speed:

• Slow speed engine ranging from 100 to 150 RPM.
• Medium speed engine ranging from 300 to 1000 RPM.
• High speed engine ranging above 1000 RPM 

Based on piston connection

• Trunk type
• Crosshead type

Based on method of charging :

• Naturally aspirated
• Super charged

Based on Combustion cycle

• Otto cycle
• Diesel cycle.
• Dual combustion cycle

Based on ignition

• Spark ignition
• Compression ignition

Two stroke cycle

• Two stroke engine take two strokes of piston or one complete revolution of cranckshaft to complete one cycle.
• In two stroke engine suction, compression, expansion and exhaust take place in two stroke thus fuel injected and exhaust valve open in each stroke.
• Two stroke engine are provided with blower for charging fresh air.

• Intake begins when the piston is at bottom dead centre. Air is admitted into the cylinder by scavenge ports as there is no inlet valve. Two stroke deisel engine require artificial aspiration to operate. The use mechanically driven blower or turbocharger to push in charge air. The charged air pushed in is also used to push out exhaust gases. This process of removing exhaust using fresh air is termed as scavenging.

• As the piston is about to reach TDC atomotised fuel is injected into the system. This fuel ignites due to high pressure and heat created by compression of air.
• At about 110° after TDC the exhaust valve open and hence the exhaust gases produce by the fuel injected begin to discharged through exhaust manifold.
• At about 140° after TDC scavenge ports are uncovered. The uncovering of scavenge ports result in charge of fresh air introduced to the system this will also flush out the remaining exhaust gases present in the system.
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