Engine Components and Basics Flashcards
Cylinder head
To seal the working fluid
Houses the inlets, outlets, spark plugs
Cast iron or Al in modern cars
Cylinder
Guides the piston
Where combustion occurs
Most be cooled as in contact with hot products
Cylinder liner
Inner wall of the cylinder
Purpose is to maintain heat in combustion chamber
Second purpose to reduce frictional loses
Head gasket
To seal the joint between cylinder head and engine block
Prevent leakage of fluids
Manifold
Supply airfuel mixture and collect exhaust gas
Inlet/Exhaust valves
Regulate flow of fluid in and out of the cylinder
2 inlets and outlet for each cylinder
Sinusoidal operation
Camshaft
Controls valve timings
Ontop of the cylinder head
Driven by the crank via timing belt
Piston
Transfers combustion energy to the connecting rod
Compression of airfuel mixture
Gas tight seal that can slide freely
High thermal and wear resistance
Piston Rings
Top and mid ring = compression rings, stop pressure loss
Bottom ring = oil ring, keeps oil out of combustion chamber and provides cooling
Connecting rod
Connects piston to crank
Must be very strong
Good lubrication required to minimise frictional loses
Crankshaft
Linear into rotational motion
Journals and counterweights for vibration minimisation
Connected to fly wheel and ring gear (used to start engine)
Can rotate freely
Oil sump
Collect oil from engine
Repumps oil into the engine
Bolted to bottom
Timing belt
Links the crank and cam shaft
Cam-crank ratio of 2:1
Engine bearings
Used to reduce frictional loses throughout the engine
allowed to freely rotate
Fly Wheel
Attached to crankshaft
On the other side is the clutch
Ring gear to start the engine
Spark plug (SI only)
Produces spark that ignites airfuel mixture for combustion
1 per cylinder
Carborator (SI only)
Not used anymore
Atomises the liquid fuel
Produces premixed airfuel mixture
Port injectors (SI only)
Fuel injected into the intake manifold
Mechanically or electrically controlled
Direct injectors (SI only)
Fuel injected into the cylinder
Fuel sprayed into combustion chamber at high pressure
Fuel atomiser or injector (CI only)
Direct fuel injection into the cylinder
Different spray patters achievable
Many holes available
Name the main engine layouts
Inline
V type -> more power as more cylinders for same space
Flat - mostly 2 stroke
What is the typical firing order in a 4 cylinder engine
1432 or 1243
This is to achieve good cooling
Cooling systems purpose
Liquid cooling system can be used to remove heat from the engine
Removed heat can be supplied to passengers
Engine Sensors
Engine speed
Determine crank position and piston position
- hall effect and inductive sensors
Micromechanical pressure sensors
Intake manifold pressure
boost pressure
ambient pressure and air density
so the ECU can change AFR for optimum performance depending on these…
High pressure sensors
Measure fuel and break fluid pressure
Rail pressure sensors
Temperature Sensors
Installed in cooling circuit
Air, engine oil, fuel, and exhaust
Important to understand if the engine is overheating
ECU takes measures to cool engine (increase AFR)
Knock sensors
Vibration sensors to detect knock
Send info to ECU to adjust injection timing
Lambda oxygen sensors
Measure oxygen content in the exhuast
Determines if lean or rich combustion
-> too little/no oxygen is stoich or rich
-> too much is lean
Want stoich conditions in SI and fuel lean in CI
Actuators
Final control elements for the interface between electronic signal processor and the actual process
electric signal -> mechanical process
what are the 4 strokes in combustion
intake -> inlet open, outlet closed
compression -> both close and gas is compressed
combustion -> both close, spark or auto-ignition
exhaust -> inlet closed, outlet open
2 stroke engine vs 4 stroke engine
intake and compression together
power and exhaust together
lighter flywheel
no valves, just ports
thermal efficiency is comparatively low
greater cooling and lubrication
initial cost is lower
used in low cost applications
