02. Piston Engine: Principle of Operation Flashcards
How do piston engines produce power?
By converting ____ energy into ____ energy
- CHEMICAL
- MECHANICAL
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Burning fuel with air within a cylinder release what sort of energy?
HEAT ENERGY
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Gas absorbs the heat released from burning fuel with air.
What energy does this create?
PRESSURE ENERGY
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What component converts pressure energy into mechanical energy?
PISTON
As mixture is ignited and heated, pressure increases forcing the piston down the cylinder.
The piston is connected to the crankshaft via connection rod which forces it to turn, converting the downwards linear motion into rotary motion.
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What is the working fluid of an internal combustion engine?
AIR
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Air mixed with fuel is known as what
MIXTURE
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The gas produced from burning mixture is known as what
EXHAUST
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How does mixture enter into the cylinder
INLET PORT
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What is an inlet port
Allows mixture into cylinder
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What is an inlet valve
CLOSES INLET PORT
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What component seals an inlet port
INLET VALVE
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What is THE CHARGE
Total mixture drawn into cylinder
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The total mixture drawn into the cylinder is known as what
THE CHARGE
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How is the charge ignited
SPARK PLUG
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- What causes the pressure increase within a cylinder after combustion.
- What is the result
- Hot air attempts to expand within the sealed cylinder
- Piston forced down the cylinder
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What does the CRANKSHAFT do in terms of converting motion
Converts LINEAR motion into ROTARY motion
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What is the piston connected to
CRANKSHAFT
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What is the UP/ DOWN motion of the piston known as
RECIPROCAL MOVEMENT
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What is a name given to a piston engine based on the UP / DOWN movement of the piston
RECIPROCATING ENGINE
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How does gas exit the cylinder
EXHAUST PORT
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What seals the exhaust port closed
EXHAUST VALVE
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The piston is connected to the crankshaft. The crankshaft is connected either directly or indirectly to what
PROPELLER
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The 4 strokes of a piston engine are commonly known as what
4 STROKE CYCLE
Otto cycle
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What are the 4 strokes of the 4-stroke cycle
- Induction
- Compression
- Power
- Exhaust
Suck, Squeeze, Band, Blow
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The distance the piston travels within the cylinder is referred to as what
STROKE
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What is a STROKE
DISTANCE PISTON TRAVELS IN CYLINDER
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The topmost limit the piston can travel is referred to as what
TOP DEAD CENTER
(TDC)
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The bottom most limit the piston can travel is referred to as what
BOTTOM DEAD CENTER
(BDC)
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Ignition occurrs between which 2 strokes of the otto cycle
COMPRESSION and POWER
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In a non optimised otto cycle, when will the INLET VALVE open and in which phase
- PISTON TDC
- INDUCTION
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During the induction stroke, as the piston travels down the cylinder, the pressure and temperature INCREASE or DECREASE
DECREASE
Decrease in pressure and temperature cause the mixture to be sucked into the cylinder
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In a non optimised otto cycle, when will the INLET VALVE close and in which phase
- PISTON BDC
- INDUCTION
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An engine that draws in fuel by sucking the mixture into the cylinder is known as what
NORMALLY ASPIRATED
Piston travels down the cylinder, temperature and pressure decreases, which causes the mixture to be sucked in
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During the compression stroke in a non optimised otto cycle;
1. The inlet valve is OPEN or CLOSED
2. The exhaust valve is OPEN or CLOSED
- CLOSED
- CLOSED
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During which stroke of a non optimised otto cycle does the spark plug ignite the mixture
COMPRESSION STROKE
Piston is near or at TDC
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What position will the piston be in when combustion occurs in a non optimised otto cycle. What is there a large increase in as combustion occurs
- TOP DEAD CENTER (TDC)
- PRESSURE & TEMPERATURE
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During combustion, pressure and temperature in the cylinder INCREASE or DECREASE
INCREASES
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During the combustion stage, which 2 elements increase within the cylinder
- TEMPERATURE
- PRESSURE
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During the power stroke, the ____ and ____ of the combusted gas INCREASE or DECREASE
- TEMPERATURE
- PRESSURE
- DECREASE
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During the exhaust stroke, the ____ and ____ of the combusted gas INCREASE or DECREASE
- TEMPERATURE
- PRESSURE
- INCREASE
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During a non optimised otto cycle, where is the piston as the exhaust stroke begins
BOTTOM DEAD CENTER
(BDC)
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What is RPM a measure of
REVOLUTIONS PER MINUTE of CRANKSHAFT
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What force creates the inertia that makes air flow inside of a piston engine
PRESSURE CHANGES
Changes of pressure within the cylinder as a result of the volume changing
i.e. when piston is UP or DOWN, volume of cylinder is changing and subsequently, the pressure inside changes
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What is the term used to define the little linear movement when the piston is near or at TDC or BDC
INEFFECTIVE CRANK ANGLE
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Ineffective crank angle marks periods where there is little what
Change in cylinder VOLUME and PRESSURE
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What is the name given to optimize when the inlet and exhaust valves open and close
VALVE TIMING
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What is the name given to optimize the point when ignition occurs
IGNITION TIMING
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What is the name given to the process of opening the inlet valve before TDC
INLET VALVE LEAD
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During which stroke does inlet valve lead occur
As EXHAUST stroke comes to an end
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What is the definition of INLET VALVE LAG
INLET VALVE remains open slightly after BDC
Inlet valve remains open slightly after piston reaches BDC and starts to travel up the cylinder again during the compression stroke
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How is valve lead and valve lag measured
DEGREES
Degrees of crankshaft rotation
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When does the exhaust valve open during an optimized otto cycle
JUST BEFORE POWER STROKE ENDS
AKA exhaust valve lead
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During an optimized otto cycle, what position is the piston in when exhaust lag is experienced
SLIGHTLY AFTER TDC
Piston is once again in the induction stroke, cycle has started over again
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What is VALVE OVERLAP
The term used to explain when the inlet and exhaust valves are both open at the same time
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What is SCAVENGING
During valve overlap period, exhaust gases flowing out of the cylinder helps draw mixture in through the inlet valve
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During valve overlap, when exhaust gases leave the cylinder, this helps draw mixture in. This is known as what
SCAVENGING
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The opening and closing of the valves in the cylinder is dictated by what
CAMS on the CAMSHAFT
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What is the purpose of the CAMSHAFT
DETERMINES VALVE OPENING and CLOSING
CAMS connected to CAMSHAFT. As CAMSHAFT turns, this determines when the valves open and close
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During an optimzed otto cycle, what position will the piston be, and during which stroke, when ignition timing occurs
- Slightly BEFORE TDC
- COMPRESSION stroke
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What is the benefit/purpose of ignition timing being optimized
MAXIMISE PRESSURE PRODUCED
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A spark timed to occur just before the piston is at TDC is known as what
ADVANCED IGNITION
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Ignition timing must be ADVANCED or RETARDED as RPM increases
ADVANCED
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Ignition timing must be ADVANCED or RETARDED as RPM decreases
RETARDED
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During engine start, ignition timing is ADVANCED or RETARDED to when the piston is in what position
- RETARDED
- TDC
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