Cap 8 The Diesel Eng

Question 1

Diesel fuel

Answer 1

~Kerosene (jetA1 /jetA)
~specific gravity about 0.8 /0.9
~less volatile and has higher flash point than AVGAS
~is a poor lubricator and so requires a specifically designed fuel pump

Question 2

Advantages and disadvantegese

Kerosene vs gaosilne

Answer 2

~more fuel efficient than gasoline
~ideally for turbocharging( bc no worried about detonation or pre ignition)
~without an ignition sys are simpler and more reliable
~Kerosene is safer and cheaper than AVGAS

Disadvantages
~ the higher operating pressure requires a stronger ,heavier designs

Question 3

Compression

Answer 3

The air si more compressed than in a spark ignition eng

Just before TDC,a precisely metered quantity of fuel is injected into the cylinder,it immediately ignites due to cylinder temperature(compression ignition)

Question 4

Compression ration

Answer 4

Total volume/clearance volume

Petrol 10:1
Deisel 20:1

Question 5

Power

Answer 5

At the point of ignition ,the charge is very much more compressed and contained in a much smaller volume

No risk detonation so diesel operate much leaner

No mixture control lever required (power out is controlled by the amount of fuel injected into the cylinder)

Question 6

Exhaust

Answer 6

Is the same a s petrol engine

Question 7

Diesel fuel injection sys

Answer 7

Injectors must operate at anything up to 1600bar (24000PSI)

Question 8

Diesel fuel injection sys

Answer 8

~mechanican injectin ,high pressure fuel is fed to each injector from a dedicated fuel pump (crankshaft driven)

~common rail ,a high pressure pump supply ,fuel is distribuites to each electronic injector
Manifold connector together and an electronic signal is sent to vary the fual quantity
Most disel use rail system bc it gives more efficient combustion,cleaner emissions and quiter operation

Question 9

COMMON RAIL

Question 10

Injectors

Answer 10

Metering sys >metering unit sends timed pulses of pressurised fuel to each injector

Common rail sys: EEC electrically signals each solenoid injector to open and close

Question 11

Glow plugs

Answer 11

~The sheathed glow plug contains an electrically heated coil
~powered from the battery .a cockpit warining light indicates their operation

Question 12

Power to weight ration diesel eng

Answer 12

Low power to weight ratio

Question 13

Liquid cooling

Answer 13

An air cooled heat exchanger disperes the heat energy absorbed by the coolant

Question 14

Swept volume

Answer 14

Volume between TDC and BDC