What is a 2-stroke diesel engine?
As name suggests, these engines work on reciprocating actions of pistons. One stroke means one linear motion of piston in one direction. When piston moves in opposite direction, that is counted as another stroke.
For a 2-stroke engine, piston has to move up, and then down to complete one cycle of engine. In those 2 strokes of piston, crankshaft will have turned 1 revolution.
The 2 strokes of piston is to complete 4 stages of combustion cycle - air intake, compression, combustion and exhaust. As you might have known, in order for a fire (or explosion) to occur to power engine, we need a fuel, a heat source, and oxygen coming together at same time.
Remember how crankshaft and piston moves in a cylinder? The reciprocating movement of piston is converted to rotary motion by means of a crankshaft. The piston reciprocates between Top Dead Center and Bottom Dead Center inside cylinder liner.
One of most prominent feature of a 2-stroke engine is presence of air intake ports on cylinder liner that will enable fresh air to be led in for combustion.
These air inlet ports are cut into cylinder liner somewhere at lower end of latter. In a typical design, air inlet port are located about 35 degrees from Bottom Dead Center (BDC).
In many designs, fresh air that is introduced into cylinder is also used to drive out spent exhaust gases inside it. Many designs make use of scavenging air fans like electric blowers or turbochargers to slightly pressurize intake air before latter is introduced into cylinder.
In order to allow exhaust gases to be expelled from cylinder, exhaust ports are often cut into cylinder just like air intake ports. A typical design will have exhaust port located about 50 degrees from Bottom Dead Center.