Diesel Engines

Question 1

Principle of operation Diesel engine

Answer 1

Compressed to a high temp so that when a fine mist of diesel it’s injected into the cylinder it ignites under the high temp

Engine is built stronger than a piston due to high temps

Uses direct fuel injection

Question 2

Compression ratio and thermal efficiency of Diesel engine

Answer 2

Compression = 22

Thermal efficiency = 45%

Question 3

Glow plug

Answer 3

Used to heat the condensation chamber an improve fuel vaporisation when the engine is started from cold

Question 4

4 strokes in a Diesel engine

Answer 4

Induction - only air drawn in

Compression - air is compressed and at precisely the right moment fuel is injected and ignited

Power - no risk of detonation, diesel runs leaner, power output controlled by the amount of fuel injection into the cylinder

Exhaust - as per petrol engine

Question 5

3 types of fuel injection n

Answer 5

Indirect

Direct

Common rail

Question 6

Electric fuel pump functions - diesel

Answer 6

Vapour suppression - when operating at high ambient temps

Back up in the event of failure of the engine driven pump

Engine priming during start

Question 7

Engine control unit |(ECU) receives inputs from

Answer 7

Throttle posn
Mix lever
Engine RPM
Temp

Controls the common rail injector about timing, amount and for how long

Question 8

Adv and disadv of liquid cooling

Answer 8

Adv - equalises the cooling of all barrels and cylinder heads
Consistent regulating of engine generating temp
Use of second heat exchanger

Disadv - greater mass, complexity, maintenance
Leaks in system = overheat