Page 25 - Introduction to Marine Engineering

Diesel engines i 3

The four-stroke engine

A cross-section of a four-stroke cycle engine is shown in Figure 2.6. The
engine is made up of a piston which moves up and down in a cylinder
which is covered at the top by a cylinder head. The fuel injector, through
which fuel enters the cylinder, is located in the cylinder head. The inlet
and exhaust valves are also housed in the cylinder head and held shut by
springs. The piston is joined to the connecting rod by a gudgeon pin.
The bottom end or big end of the connecting rod is joined to the
crankpin which forms part of the crankshaft. With this assembly the

Rocker arm

Cylinder
head

Crankpin
Bottom end
bearing
Crankcase

Figure 2.6 Cross-section of a four-stroke diesel engine