Four stroke-diesel engine :
The 4 stroke operations in a diesel engine are: induction stroke, compression stroke, ignition and power stroke and exhaust stroke.
(1) Induction stroke: While the inlet valve is open the descending piston draws in fresh air.
(2)Compression stroke: While the valves are closed, the air is compressed to a pressure of upto 25 bar
(3) Ignition and power stroke : Fuel is injected, while the valves are closed (fuel injection actually starts at the end of the previous stroke, the fuel ignites spontaneously and the piston is forced downwards by the combustion gases.
(4)Exhaust stroke : The exhaust valve is open and the rising piston discharges the spent gases from the cylinder.
Since power is developed during only one stroke, the single cylinder four-stroke engine has a low degree of uniformity.
Smooth running is obtained with multi cylinder engines because the cranks are staggered in relation to one another on the crankshaft.
There are many variations of engine configuration e.g. 4 or 6 cylinder, in-line, horizontally opposed, radial configurations.
