Diesel Engines

Question 1

What is the difference between petrol and Diesel engines

Answer 1

Petrol Engine- takes in a mixture of air and fuel into the cylinder before the mixture is compressed and then ignited with a spark plug

Diesel Engine- just takes in air into the cylinder- compressed the air and fuel injected into the compressed air and combustion occurs

Question 2

What is the applications/purposes of a Diesel engine?

Answer 2

Diesel Generators
Air Compressors
Fire Pumps
Main propulsion engines and motor boats

Question 3

What is cylinder numbering

Answer 3

Cylinders are numbered in order from the free end

Question 4

What are the components of a Diesel Engine?

Answer 4

Engine, Cylinder head, Cylinder head Joint/Gasket, Sump, Piston, Piston Rings, Connecting Rod, Crankshaft, Camshaft, Valves, Push Rod, Rocker arms, Injector and Flywheel

Question 5

What is a Cylinder head?

Answer 5

Closes the cylinder at the top
Forms part of combustion chamber
Accommodates fuel injector
Houses inlet and exhaust valves

Question 6

What is a cylinder head joint/gasket?

Answer 6

Seal between cylinder head and engine block

Protects from air,gas,water and oil

Question 7

What is a sump

Answer 7

Drain tank

Reservoir of lub oil draining from other parts of the engine

Question 8

What is a piston

Answer 8

Reciprocating motion, enables and receives compression, transfers force via gudgeon pin to crankshaft

Question 9

What are Piston rings

Answer 9

Compression rings which provides sliding seal to stop air/exhaust fumes leaking
Transfers heat from piston to cylinder
Assists with lubrications
Oil control rings which stops oil getting into combustion chamber

Question 10

What is the connecting rod?

Answer 10

Connects piston to crankshaft
Small end - piston
Big end - crankshaft

Question 11

What does a crankshaft do?

Answer 11

Turns reciprocating motion into rotary motion

Question 12

What does a Camshaft do ?

Answer 12

Controls the opening and closing of the inlet and exhaust valve in correct sequence and is driven off the crankshaft at half the speed

Question 13

What do valves do ?

Answer 13

Responsible for letting fuel/air in/out for combustion

Question 14

What does a push rod do?

Answer 14

Transfers motion from camshaft to the rocker arms

Question 15

What is the role of the rocker arms?

Answer 15

Transmits the movement of the camshaft towards the intake and exhaust valves of engine

Question 16

What does the injector do?

Answer 16

Injects a measured amount of high pressure atomised fuel into the combustion chamber

Question 17

What does the flywheel do?

Answer 17

Promotes smooth running during the non power strokes by storing kinetic energy

Question 18

What is the 4 stroke cycle ?

Answer 18

Induction
Compression
Power
Exhaust

Question 19

What is the induction stroke?

Answer 19

Inlet valve is open and exhaust is shut
Piston moves from top dead centre to bottom dead centre
Increase in volume causes depression which draws air into the cylinder

Question 20

What is the compression stroke ?

Answer 20

Both valves are shut
Piston moves from bottom dead centre to top dead centre which compresses the air trapped in the cylinder
A rise in pressure and temperature
Piston is almost at top dead the injector sprays high pressure atomised fuel

Question 21

What is the power stroke?

Answer 21

Both valves still shut
As piston passes top dead centre and starts to descend towards bottom dead centre and then combustion occurs
Burning air/fuel causes rapid increase in temp and pressure which forces piston down

Question 22

What is the exhaust stroke

Answer 22

Exhaust valve is open and inlet closed

Piston rises from bottom dead to top dead centre which pushes waste gas through the exhaust

Question 23

What is valve overlap?

Answer 23

Inlet valve starts to open just before top dead centre on exhaust stroke
Exhaust valve then remains open until slightly after top dead centre on the start of the induction stroke
Short period = 10-12 degrees of crankshaft rotation

This aids cylinder charging of fresh air for it to start again

Question 24

What are the components of basic fuel system?

Answer 24

Fuel headed tank
Fuel lift pump
Fuel filters
Fuel injection pump
Fuel injector 
Fuel spill return

Question 25

What are the components of a lubricating oil system?

Answer 25

Sump strainer
Priming pump
3 way cock
Non-return valve
Pump
Filters 
Reducing valve
Lub oil cooler

Question 26

Name oil tests carried out

Answer 26

TBN- acidity
Viscosity
Water in oil
Insolubles

Question 27

Components of salt water cooling system

Answer 27

Sea cock
Strainer
Salt water pump 
Lub Oil Cooler/heat exchanger
Discharge Overboard Valve

Question 28

Components of fresh water cooling

Answer 28

Engine block
Thermostat
Headed tank
Heat exchanger 
FW pump

Question 29

What is coolant ?

Answer 29

50/50 fresh water and AL39

AL39 is antifreeze and corrosion inhibitor

Question 30

What are the coolant tests?

Answer 30

Salinity- salt water content
Density
Acidity

Question 31

Name the engine safety devices

Answer 31

Low Lub oil pressure
Low Coolant pressure
High Lub oil temperature
Engine overspeed

Question 32

What are the resetting trips

Answer 32

Investigate the cause
Rectify the fault
Reset the trip

Question 33

What are the hazards when working with/around Diesel engines ?

Answer 33

Fire/heat
Noise
Rotating machinery
Personal hygiene