Engines Flashcards
Basic engine design requirements
Lightweight
Small
Powerful
Reliable
Repairable
2 engine classes
Piston type
Reciprocating
Intermittent internal combustion
Gas turbine
Rotating
Continuous internal combustion
4 cylinder Piston configurations
Radial
Loud, unreliable, heavy
In line
Compact (cooling issues) low horsepower
Inverted in line
Prop = higher
Horizontally opposed
Most common/best combination
DA40 engine
Textron lycoming IO-360 M1A
(IO=injected/opposed)
(360 = displacement cubic inches)
(M1A = serial number)
Operating principles for piston engine (diesel)
Compression ignition (no spark plug required) (highly compressed air)
Future/current GA contender
Operating principles for piston engine (2 stroke)
Spark ignition
Pros:
Very simple
Light/high power to weight ratio
Cons:
Requires maintenance often
Unreliable
Inefficient
Burns oil with fuel
Operating principles for piston engine (4stroke)
Spark ignition
More efficient than 2 stroke
Most common GA
4 stroke Components
Cylinder
Cylinder head
Piston
Inlet/exhaust valves
Spark plug
Crankshaft
Conrod/crankcase
Camshaft
Cylinder
Steel (or iron)
House piston
Smooth inner surface
Air cooled by cooling fins
Cylinder head
Air cooled
Fitted at the top of the cylinder
(Spark plug and valves)
Creates enclosed combustion space
Detach from cylinder block (maintenance)
Piston
Aluminium alloy
Housed in cylinder
3ring seal (minimised loss of gases to crank case, improves heat transfer between piston and cylinder wall, scrapes oil on wall back to sump
Inlet and exhaust valves
Allow fuel air mixture into combustion space
Exhaust expels burnt gases
Operated by camshaft
Spark plug
Ignites fuel air mixture
2 per cylinder for redundancy
20000v per
Subjected to 2000 psi pressure
Crankshaft
Connected to piston via conrod
Weights to reduce vibration
Translates linear to rotational
Housed within crankcase
Conrod and crankcase
Conrod connect piston to crankshaft
Crankcase houses crankshaft
Camshaft
Geared to crankshaft
Operated at half the speed
Opens and closes valves at correct time (using rocker arm)
Works in conjunction with spring compress on top of valves
TDC & BDC
Top dead centre and bottom dead centre
Otto cycles (4 strokes)
1 suck: induction stroke
Air fuel mixture in
Piston tdc to bdc
(Reduction in pressure)
2 squeeze: compression stroke
Inlet valve is closed first
Piston BDC to TDC
Compresses fuel air mixture (higher pressure
3 bang: power stroke
End of compression stroke spark plug ignites FA mixture
Controlled combustion, gases expand, piston forced down
4 blow: exhaust stroke
Exhaust valve opens
Piston BDC to TDC
Burnt gases expelled
