Page 26 - Introduction to Marine Engineering

14 Diesel engines

linear up-and-down movement of the piston is converted into rotary
movement of the crankshaft. The crankshaft is arranged to drive
through gears the camshaft, which either directly or through pushrods
operates rocker arms which open the inlet and exhaust valves. The
camshaft is 'timed' to open the valves at the correct point in the cycle. The
crankshaft is surrounded by the crankcase and the engine framework
which supports the cylinders and houses the crankshaft bearings. The
cylinder and cylinder head are arranged with water-cooling passages
around them.

The two-stroke engine

A cross-section of a two-stroke cycle engine is shown in Figure 2.7. The
piston is solidly connected to a piston rod whkh is attached to a
crosshead bearing at the other end. The top end of the connecting rod is

Exhaust
manifold

Turboblower

Air inlet
ports

Crosshead Connecting rod

Bottom end A-frame
bearing

Bedplate
Crankshaft

Figure 2.7 Cross-section of a two-stroke diesel engine