Fuels And Additives Flashcards
(28 cards)
What are hydrocarbons?
Fuels for internal combustion engines are basically substances that can be made to vaporise and burn
What is crude oil?
It’s found it’s earths crust and hydrocarbons are processed from it
What dose LPGstand for?
Liquefied petroleum gas
What are bio fuels?
Alcohols (methanol and Ethanol) are produced from vegetable matter
How would you describe crude oil?
Unprocessed oil
What dose crude oil contain?
Hundreds of different types of hydrocarbon all mixed together
What is fraction distillation?
Is used for separating a mixture of substances with narrow differences
What is cracking?
Breaking large hydrocarbons into smaller pieces
What is unification?
The combination of smaller hydrocarbons to make larger ones
What is alteration?
The structures of molecules in one fraction are rearranged to produce another
What are some properties of good fuel?
High calorific value High octane number Low freezing point High latent heat Easy evaporation High flash point High density Must not absorb water
What are the side effects of having a RICH fuel mixture?
High power
Less efficient combustion
What are the side effects of having a WEAK fuel mixture?
Lower power
More efficient combustion
Lower fuel consumption
What is detonation?
When burning takes place in many parts of the combustion chamber almost at same time and a powerful shockwave occurs
What dose detonation cause?
Knocking
Pinking
What are the effects of detonation?
Erosion and burning
Damage
Power loss
Pre ignition
What factors could affect detonation?
Poor fuel quality High compression ratio Ignition timing Under heavy load Accusation of carbon
What is pre ignition?
It’s the ignition of the mixture before the spark at the spark plug, it is ignited by some hot spot in the cylinder
What are the effects of pre ignition?
Seizure - due to high cylinder pressure oil tends to be forced out the piston grooves and then ignites
Effects affecting pre ignition?
Carbon deposits
Detonation - heavy detonation causes local overheating giving rise to pre ignition
What is the octane number?
It’s a measure of a fuels resistance to detonation
What is flash point?
Lowest temp at which vapours ignite in air when exposed to a flame
What is volatility?
The ability of the fuel to change into a vapour form
What is the cetane number?
For diesel only
It’s readiness for self ignition
