P The Diesel Engine Flashcards
What is diesel fuel and what is it known as in aviation?
Kerosene, Jet A1/Jet A
What are its characteristics compared to AvGas?
Less volatile and has a higher flash point
What are the disadvantages of a Diesel engine?
It is a poor lubricant so requires a special fuel pump
Higher operating pressures requires stronger, heavier designs
What are the advantages of a Diesel engine?
- More fuel efficient
- Require less scheduled maintenance
- Ideally suited to turbocharging
- No ignition system, simpler and more reliable
- Kerosene is cheaper and safer than AvGas
What is the key difference between diesel and petrol engines?
Diesel engines do not require a spark for ignition
Why don’t Diesel engines require a spark for ignition?
Air is more compressed than in a petrol engine and therefore hotter, just before TDC fuel is injected into the cylinder and immediately ignites due to the cylinder temperature
Why is compression ignition safer than spark ignition?
No risk of detonation, diesels can run leaner
Do Diesel engines need mixture control?
No, the power output is controlled by the amount of fuel injected
What pressures do the cylinders experience?
Very high, up to 24,000psi
What are the 2 types of diesel fuel injection systems?
- Mechanical injection
2. Common rail injection
What is mechanical injection?
High pressure fuel is fed to each injector from a dedicated, crankshaft driven, fuel pump
What is common rail?
A high pressure pump supplies fuel to a common ail from where fuel is distributed to each electronic injector
Which system do modern Diesel engines use and why?
Common rail, gives more efficient and cleaner combustion
How does an injector work?
Mechanically operated spring loaded poppet valve which opens when fuel pressure exceeds spring force
What is a mechanical injection metering system?
Metering unit sends timed pulses of pressurised fuel to each injector
