OPERATION CYCLE OF 4 STOKE DIESEL ENGINE:

OPERATION CYCLE OF 4 STOKE DIESEL ENGINE:

Inlet valve  open (20degree)before TDC

Inlet valve closed  (60 degree)after BDC

Exhaust valve open(42 degree)before BDC

Exhaust valve closed (60 DEGREE)after  TDC

                 TDC

                BDC

5 Two-stroke diesel engine

Main article: Two-stroke diesel engine

Diesel engines rely solely on the heat of compression

for ignition. In the case of and

loop-scavenged engines, intake  and exhaust happens via

piston-controlled ports. A takes in

air via, and exhaust gases exit through an

overhead. Two-stroke diesels are all scavenged

by forc. Some designs use a mechanically

driven, whilst marine diesel engines

normally use exhaust-driven turbochargers, with electrically

driven auxiliary blowers for low-speed operation

when exhaust turbochargers are unable to deliver enough

air.

Marine two-stroke diesel engines directly coupled to the

propeller are able to start and run in either direction as

4 STROKE  ENGINE OPERATING CYCLE  IS COMPLETED :

*Suction stroke  *compression stroke

*power stroke(expansion)

*exhaust stoke

required. The fuel injection and valve timing is mechanically

readjusted by using a different set of cams on the

camshaft. Thus, the engine can be run in reverse to move

the vessel backwards.

6 Lubrication

Most small petrol two-stroke engines cannot be lubricated

by oil contained in their crankcase and sump, since the

is already being used to pump fuel-air mixture

into the cylinder. Traditionally, the moving parts (both

rotating crankshaft and sliding piston) were lubricated by

a premixed fuel-oil mixture (at a ratio between 16:1 and

100:1). As late as the 1970s, petrol stations would often

have a separate pump to deliver such a premix fuel to

motorcycles. Even then, in many cases, the rider would

carry a bottle of their own two-stroke oil. Taking care

to close the fuel-tap first, he or she would meter in a little

oil (using the cap of the bottle) and then put in the

petrol, this action mixing the two liquids. Two-stroke

oils which became available worldwide in the 1970s are

specifically designed to mix with petrol and be burnt in

the combustion chamber without leaving undue unburnt

oil or ash. This led to a marked reduction in spark plug

fouling, which had been a factor in two-stroke engines.

More recent two-stroke engines might pump lubrication

from a separate tank of two stroke oil. The supply of

this oil is controlled by the throttle position. An example

machine is Yamaha’s PW80 (Pee-wee), a small, 80cc

two stroke dirt bike designed for young children. The

technology is referred to as auto-lube. This is still

CYCCLE: