Diesel engines

Question 1

What is the difference between a diesel and petrol engine

Answer 1

Petrol engines use an air fuel mixture before compressing and and igniting with a spark plug. A diesel takes air and fuel which is compressed and the hot compressed air spontaneously combusts.

Question 2

Main 4 uses of diesel engines

Answer 2

Generators, air compressors, fire pumps & main propulsion engines

Question 3

State the numbering system for a diesel engine

Answer 3

From free end starting with cylinder 1 moving across numerally to the drive end (fly wheel). Can be departed into 2 banks A & B

Question 4

What is the largest part of a diesel engine

Answer 4

Engine block

Question 5

What is the function of an engine block

Answer 5

Main body of engine. The structure itself. Holds everything together

Question 6

Where is the cylinder block located and what is its function

Answer 6

Above the engine block and it hold the cylinders where pistons function

Question 7

What is the cylinder head

Answer 7

At the top of the engine accomodates the fuel injectors and closes off the cylinders

Question 8

What is a cylinder head joint and what is it made from

Answer 8

It is a tight seal between cylinder block and cylinder head. Usually made from composite materials and reinforced in high pressure areas with soft metal

Question 9

What is a sump

Answer 9

Acts as a reservoir for Lub oil draining down at the bottoms of the engine

Question 10

What is a piston in a diesel engine

Answer 10

Moving component of engine. Moves in up-down motion. Enables compression of air inside the cylinder and to revive forces that arise from combustion transferring forces to crankshaft enabling rotation

Question 11

Piston rings what are they

Answer 11

Provide a sliding seal between outer edge of piston and inner edge of cylinder

Question 12

How many piston rings are there

Answer 12

3

Question 13

What are the 3 piston rings functions

Answer 13

2 rings are for dealing in pressure. 1 ring is for oil control

Question 14

What is the connecting rod

Answer 14

Connects the pistons to the crankshaft. Exposes to high tension

Question 15

Where is the Gudgeon pin

Answer 15

Is connected to the piston via the connecting rod at the small end.

Question 16

What is the role of the Gudgeon pin

Answer 16

Transfers load from the piston to the con-rod

Question 17

What does a crankshaft do

Answer 17

Turns reciprocating motion into rotary motion

Question 18

What does the camshaft do

Answer 18

Controls the opening and closing of the inlet and exhaust valves in the correct sequence

Question 19

What is the function of the fly wheel

Answer 19

Promoted the smooth running during the non-power strokes by storing kinetic energy

Question 20

What do valves do in a diesel engine

Answer 20

Open and close at top of engine

Question 21

What do pushrods do

Answer 21

Transfer motion from the camshaft to the rocker arms

Question 22

What is a rocker arm

Answer 22

Pivoting arm that transfers motion from the pushrod to activate the valves

Question 23

Where is the fuel injectors located

Answer 23

In the cylinder head

Question 24

What does the fuel injector do

Answer 24

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

Question 25

Name the 4 strokes in the 4 stroke cycle

Answer 25

Induction (suck), compression (squeeze), power (bang) & exhaust (blow)

Question 26

Describe the induction stroke

Answer 26

Inlet valve is open and exhaust is closed. Piston moves from TDC to BDC. Increase in volume causes a depression drawing air into the cylinder. The inlet valve closes just after BDC

Question 27

Describe the compression stroke

Answer 27

Inlet and exhaust valves are both closed. Piston moves from BDC to TDC compressing the air trapped in the cylinder which causes a rise in pressure and temp. When piston is almost at TDC the injector sprays fuel. This allows for an ignition delay of the fuel ignition

Question 28

Describe the power stroke

Answer 28

Both valves are closed. Just the piston passes TDC and starts to descend toward BDC the file has ignited and combustion occurs. The burning air/fuel mix causes rapid increase in temp and pressure and the piston down to BDC

Question 29

Describe the exhaust stroke

Answer 29

The exhaust valve is open, the inlet valve is closed. Piston rises from BDC to TDC pushing waste gasses through the exhaust

Question 30

What is valve overlep

Answer 30

Inlet valve starts to open just before TDC on the exhaust stroke and the exhaust valve remains open until slightly after TDC on the start of the induction stroke this short period is know as valve overlap.

Question 31

What does valve overlap aid

Answer 31

Cylinder charging of fresh air for the induction stroke, and the fresh air entering the cylinder helps purge exhaust gasses and cools the exhaust valve

Question 32

What are the 3 oil tests

Answer 32

Acidity, viscosity & water in oil

Question 33

Name the 5 engine safety devices

Answer 33

Low Lub oil pressure, Low coolant pressure, high coolant temp, high Lub oil temp & engine over speed

Question 34

Major working hazards of a diesel engine

Answer 34

Fire/heat, noise, rotating machinery and personal hygiene

Question 35

What must be done if an engine trips

Answer 35

Investigate the cause, rectify the fault and reset the trip