Introduction And Application

Question 1

What are the two types of engine?

Answer 1

Petrol.

Diesel.

Question 2

Whats the difference between petrol and diesel engines?

Answer 2

Petrol - draws in fuel and air which is ignited by a spark.
Diesel - drawns in fresh air which is compressed, then atomised fuel is added, heat from the compressed air ignited the mixture.

Question 3

Name 4 applications of diesel engines.

Answer 3

Diesel generators.
Main engines & motor boats.
Air compressors.
Fire pumps.

Question 4

Explain the operation of a diesel engine.

Answer 4

The piston moves from TDC to BDC, drawing in air via the inlet valve. Inlet valve then closes.
Piston moves from BDC to TDC, compressing the air above it. Just before TDC, fuel is injected into the cylinder and the hot compressed air causes it to ignite.
Combustion cause rapid increase in pressure, forcing piston down to BDC.
Exhaust valve opens and piston moves back to TDC, pushing out the waste gases.

Question 5

What are the 4 strokes of a diesel engine?

Answer 5

Induction.
Compression.
Power.
Exhaust.

Question 6

Explain valve overlap.

Answer 6

Promoted charge exchange (fresh air in, exhaust gasses out)
Intake valve opens just before TDC, exhaust shuts just after TDC.
Momentum of exhaust fumes leaving pulls in fresh air entering.
Fresh air entering helps to push out remaining exhaust fumes.
Small amount of fresh air passes by exhaust valve, cooling it down.