In our last publication, we touched a bit on 4-stroke diesel engine. Today, let's touch on 2-strokes.

What is a 2-stroke diesel engine?

As the name suggests, these engines work on reciprocating actions of pistons. One stroke means one linear motion of the piston in one direction. When the piston moves in the opposite direction, that is counted as another stroke.
For a 2-stroke engine, the piston has to move up, and then down to complete one cycle of the engine. In those 2 strokes of the piston, the crankshaft will have turned 1 revolution.

The 2 strokes of the piston is to complete 4 stages of the combustion cycle - air intake, compression, combustion and exhaust. As you might have known, in order for a fire (or explosion) to occur to power the engine, we need a fuel, a heat source, and oxygen coming together at the same time.

Remember how the crankshaft and the piston moves in a cylinder? The reciprocating movement of the piston is converted to rotary motion by means of a crankshaft. The piston reciprocates between Top Dead Center and Bottom Dead Center inside the cylinder liner.

One of the most prominent feature of a 2-stroke engine is the presence of air intake ports on the cylinder liner that will enable fresh air to be led in for combustion.

These air inlet ports are cut into the cylinder liner somewhere at the lower end of the latter. In a typical design, the air inlet port are located about 35 degrees from the Bottom Dead Center (BDC).

In many designs, the fresh air that is introduced into the cylinder is also used to drive out the spent exhaust gases inside it. Many designs make use of scavenging air fans like electric blowers or turbochargers to slightly pressurize the intake air before the latter is introduced into the cylinder.

In order to allow the exhaust gases to be expelled from the cylinder, exhaust ports are often cut into the cylinder just like the air intake ports. A typical design will have the exhaust port located about 50 degrees from Bottom Dead Center.