Diesel Engines Flashcards
What is the difference between petrol and Diesel engines
Petrol Engine- takes in a mixture of air and fuel into the cylinder before the mixture is compressed and then ignited with a spark plug
Diesel Engine- just takes in air into the cylinder- compressed the air and fuel injected into the compressed air and combustion occurs
What is the applications/purposes of a Diesel engine?
Diesel Generators
Air Compressors
Fire Pumps
Main propulsion engines and motor boats
What is cylinder numbering
Cylinders are numbered in order from the free end
What are the components of a Diesel Engine?
Engine, Cylinder head, Cylinder head Joint/Gasket, Sump, Piston, Piston Rings, Connecting Rod, Crankshaft, Camshaft, Valves, Push Rod, Rocker arms, Injector and Flywheel
What is a Cylinder head?
Closes the cylinder at the top
Forms part of combustion chamber
Accommodates fuel injector
Houses inlet and exhaust valves
What is a cylinder head joint/gasket?
Seal between cylinder head and engine block
Protects from air,gas,water and oil
What is a sump
Drain tank
Reservoir of lub oil draining from other parts of the engine
What is a piston
Reciprocating motion, enables and receives compression, transfers force via gudgeon pin to crankshaft
What are Piston rings
Compression rings which provides sliding seal to stop air/exhaust fumes leaking
Transfers heat from piston to cylinder
Assists with lubrications
Oil control rings which stops oil getting into combustion chamber
What is the connecting rod?
Connects piston to crankshaft
Small end - piston
Big end - crankshaft
What does a crankshaft do?
Turns reciprocating motion into rotary motion
What does a Camshaft do ?
Controls the opening and closing of the inlet and exhaust valve in correct sequence and is driven off the crankshaft at half the speed
What do valves do ?
Responsible for letting fuel/air in/out for combustion
What does a push rod do?
Transfers motion from camshaft to the rocker arms
What is the role of the rocker arms?
Transmits the movement of the camshaft towards the intake and exhaust valves of engine
What does the injector do?
Injects a measured amount of high pressure atomised fuel into the combustion chamber
What does the flywheel do?
Promotes smooth running during the non power strokes by storing kinetic energy
What is the 4 stroke cycle ?
Induction
Compression
Power
Exhaust
What is the induction stroke?
Inlet valve is open and exhaust is shut
Piston moves from top dead centre to bottom dead centre
Increase in volume causes depression which draws air into the cylinder
What is the compression stroke ?
Both valves are shut
Piston moves from bottom dead centre to top dead centre which compresses the air trapped in the cylinder
A rise in pressure and temperature
Piston is almost at top dead the injector sprays high pressure atomised fuel
What is the power stroke?
Both valves still shut
As piston passes top dead centre and starts to descend towards bottom dead centre and then combustion occurs
Burning air/fuel causes rapid increase in temp and pressure which forces piston down
What is the exhaust stroke
Exhaust valve is open and inlet closed
Piston rises from bottom dead to top dead centre which pushes waste gas through the exhaust
What is valve overlap?
Inlet valve starts to open just before top dead centre on exhaust stroke
Exhaust valve then remains open until slightly after top dead centre on the start of the induction stroke
Short period = 10-12 degrees of crankshaft rotation
This aids cylinder charging of fresh air for it to start again
What are the components of basic fuel system?
Fuel headed tank Fuel lift pump Fuel filters Fuel injection pump Fuel injector Fuel spill return
