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Engine Operation & Construction
History
1876 - Nikolaus Otto, working with Gottlieb Daimler developed the four-cycle engine. (Otto Cycle)
1893 – Rudolf Diesel patents the compression ignition engine. (Diesel Engine)
1902 – Daimler-Mercedes begins production on the first gasoline powered car
One of the FIRST!
Where we use them
Brainstorm
Basic Engine Operation & ConstructionPurpose of an engine - To create power for a specific use!Use for What?How do you create Power?A Potato Gun !!! How does it work!!
Easy !!
Purpose of a piston type engine - To create power for a specific use and convert reciprocating power to rotary power
Basic Engine Operation & Construction
Converting reciprocating power to rotary power is done with three basic parts
It’s just like riding a bike !
Basic Engine Terminology
Connecting Rod: Connects the piston to the crankshaft
Crankshaft: Converts the vertical motion of the piston into usable rotary motion
Parts
Piston: Moves up and down in the cylinder to pump air and fuel into and out of the motor
Valves: Open and close to allow air and fuel into and out of the combustion chamber
Parts that make you go Hmmm.
Camshaft: Opens valves by pressing down on them (or via a lifter). A valve spring then closes the valve as the Lobe of the cam rotates off of the valve.
Cylinder Head: Holds the valves in place, provides a spot for the spark plug, controls combustion, and helps cool the engine.
Parts that make you go Hmmm.
More information on slides # 36 & 37
External Combustion
Combustion: the act or process of burning, creating pressure for a specific use!
External Combustion: Pressure/Power created outside of the engineEx: Steam Engines
The slide valve allows high-pressure steam to act alternately on both sides of the piston
Internal Combustion: Pressure/Power created inside of the engine
Ex: Four Stroke Engines
Internal Combustion
Pull a tiny amount of high energy fuel into a small space (INTAKE), COMPRESS it to an even smaller space, ignite it & BOOM!
The POWER stroke takes place and EXHAUST is forced out of the cylinder
Creating Internal Combustion
Intake Valve Opens while piston moves down creating a low pressure area (vacuum) inside the cylinder pulling in an air/fuel mixture
INTAKE STROKE
Creating Internal Combustion
Compressing theA/F mixture
makes it more volatile! Why?
Compression Creates-Energy-Heat
-A super activeA/F mixture
Compress the A/F to much and…
Pre-Ignition!
COMPRESSION STROKE
Piston moves up, both valves are closedA/F mixture gets compressed into a smaller
space (ex. Compression ratio of 9:1
Creating Internal Combustion
Both valves are closed
Spark plug Ignites A/F mixture
A/F mixture starts to burn
Burning gases force the piston down in the cylinder
POWER STROKE
Creating Internal Combustion
Start Over!
Piston moves up forcing the burnt A/F Mixture out of the cylinder via the exhaust valve through pressure
Done!
EXHAUST STROKE
Welcome to the Four Stroke Cycle
Intake Compression Power Exhaust
What were they again?
The Four Stroke Cycle
Intake - Intake valve opens, piston travels from TDC to BDC, creating a vacuum, drawing in air/fuel mixture into the combustion chamber. Intake valve closes.
Compression - Both valves closed, piston travels from BDC to TDC compressing the air/fuel mixture. A volatile mixture, and heat are created.
Power - air/fuel mixture is ignited and begins to burn, and expand. The pressure forces the piston down from TDC to BDC causing the crankshaft to turn.
Exhaust - exhaust valve opens, piston moves from BDC to TDC forcing out the burnt gases remaining from the created power. Exhaust valve closes
CYCLE REPEATS
Number of Cylinders & Cylinder Arrangements
Inline V-Type Opposed / Boxer
1, 2, 3, 4, 5, 6, 8 2, 4,6, 8, 10,12, 16 2, 4, 6
Cylinder Numbering
Firing Order: the order in which each cylinder begins its power stroke
Other Piston Cylinder Arrangements
Radial W12
Fuel Types
Gasoline
Propane
Natural Gas
Alcohol
Diesel
Advantages Disadvantages
- different octane levels- availability
- highest polluting
- cost- low polluting
- power loss 10%- availability
- cost, cheapest- very low polluting
- power loss 20%- availability- carrying danger
- high octane- Very low polluting
- high cost- poor fuel economy
- cost, better fuel economy- lots power/torque- long lasting
- high polluting- engine cost- noise / low RPM
Cooling System / Ignition Type
AirCooled Spark
LiquidCooled Compression
Diesel Fuel - rated by cetane number - difficult to ignite
IntakeAir Only
CompressionAir Only
Creating Heat
PowerHot Air IgnitesInjected Diesel
ExhaustBurnt A/F
Pushed Out
Other Engine TypesDiesel Engine
Other Engine TypesDiesel Engine
Diesel Injectors must:-Enter correct amount of fuel-Be at the right time-Control the rate of fuel-Start and stop abruptly
Advantages- cost, better fuel economy- lots power/torque- long lasting
Disadvantages- slow acceleration- low RPM- engine cost- fuel system repairs- noise
Two Stroke CycleBasic operating principles- similar to a 4 stroke, operating principles of Intake, Compression, Power and Exhaust. - the above principles are completed in two strokes instead of four; strokes are combined
How do you combine4 strokes into 2?
Other Engine Types
1. Intake- Starts while piston is moving down(Finishes with Piston moving up)- Intake port is cleared by the piston- Air/Fuel mixture is pushed intothe combustion chamber.
2. Compression- Piston is moving up- Only occurs for approx. 1/2 of the stroke (the first half of
the stroke the intake and exhaust ports are still open –siphoning occurs)
Two Stroke CycleOther Engine Types
3. Power- Piston moving down.- Only occurs for approx. the first 1/2 of the stroke (during the second half the exhaust and intake ports open and the cycles start to repeat)
4. Exhaust- Starts while piston is moving down from Power stroke- Exhaust port is cleared by the piston.- Exhaust escapes from the combustion chamber before full power stroke is complete
Operating Principles
-A/F/Oil mixture is drawn into the crankcase by a vacuum as the piston moves up during the compression stage
As the moves down on the power stage, pressure is created in the crankcase, therefore forcing the A/F/Oil mixture into the combustion camber
How is the A/F pushed into the combustion camber?
Two Stroke CycleOther Engine Types
Disadvantages- high wear rate- low torque- lubrication needs to be mixed or injected- high in pollutants
Advantages- less moving parts,no valves
- runs at any angle- high revving- fast acceleration
Two Stroke CycleOther Engine Types
Similar operating principle of the two stoke gasoline engine.However: the crankcase is not used to create pressure!
Air is forced by a blower!
Two Stroke DieselOther Engine Types
Disadvantages
- engine cost- fuel system repairs- noise
Advantages
- better fuel economy- lots power/torque- long lasting- less moving parts- higher revving- faster acceleration
Two Stroke DieselOther Engine Types
Rotary / Wankel
Other Engine Types
Other Engine TypesRotary Combustion
Basic Operating Principles – Stages
Stage 1 - rotor clears intake port, chamber increases in size, creating a vacuum drawing in A/F mixtureStage 2 - rotor continues to rotate, intake port closed off, chamber begins to compress A/F mixtureStage 3 - A/F mixture ignited by spark plug, burning creating power against rotor continuing rotary motion
Stage 4 - turning rotor uncovers exhaust port, forcing out exhaust gases as chamber is decreasing
Other operating principles
- Three chambers acting at the same time doing different stages
- Some motors with two rotors therefore six power thrust for one revolution
- Power to crankshaft done with gears on an eccentric
- 3 to 1 ratio of rotor to crankshaft rotation
Other Engine TypesRotary Combustion
Advantages
- fewer moving parts- less power loss to friction- 1/2 size / hp of piston engine- almost vibration less- quite running- great acceleration- constant torque - high RPM obtained
Disadvantages
-rapid wear of appex seals- repair costs- poor fuel economy- high in air pollutants
Other Engine TypesRotary Combustion
Turbine / Jet engines
Other Engine Types
How valves Open and Close
Mechanically withA Cam Lobe
Valve Timing with gear ratio’s
1 : 1 1 : 2
Camshaft CamshaftCrankshaft Crankshaft
How valves Open and Close
DOHCDouble Over Head Cam
Overhead Camshaft
Carburetion – Air passes through a Venturiwhich causes an area of low pressure. The fuel is drawn into the Venturi where it mixes with the moving air.
Fuel Systems
Low Pressure Area
Carburetors are “oldschool” Carburetor Video
Engine Measurement - Part 1!! Calculating TORQUE !!
Torque = Force X Distance
T = 40N X 0.3m
Answer: T = 12 Nm
Conversion: 4.44N = 1 lb force
Conversion: 2.54cm = 1 inch
40N = 8.99 lb
30cm = 11.8 inches
12” = 1 foot
T = 8.99lb x 11.8 inchesAnswer: T = 106 inch lbs
In ft lbs ?
! Big Difference between ft lbs and in lbs !
106 / 12 = 8.83 ft lbs
Piston Displacement
PD = the volume the piston displaces or sweeps out from BDC to TDC.
(How much A/F is drawn in?)
Cylinder Volume=
R X H2
PD = ( Bore/2 )2
X Stroke X # of Cylinders
Engine Measurement - Part 2
! Calculating Piston Displacement !
Ex. #1 Bore = 75 mmStroke = 100 mm
PD = (B/2) x S x # of cylinders2
PD = (75 mm/2) x 100 mm x 12
PD = 441563 mm 3
Answer in cm3
1 cm =3
1,000 mm3
Therefore 441563 mm1000 mm 3
3
Answer = 441.5 cm or CC3
1 cm
1 cm
1 cm
1 cm x 1cm x 1cm = 1 cm3
1 cm = 10 mm
Therefore:10mm x 10mm x 10mm = 1000mm3
More Impressive 450 CC !!
Engine Measurement - Part 2
Ex #2 Bore = 3.5”Stroke = 4”8 cyl engine
PD = (B/2) x S x # cyl2
PD = (3.5”/2) x 4” x 82
PD = 307.72 in 3
Answer in CC
1 in =3
16.4 cm3
Therefore : 307.72 in x 16.4 in33
Answer = 5046.7 cm or 5000 CC3
1 in
1 in
1 in
1 in x 1 in x 1 in = 1 in3
or 307 cu in
1 in = 2.54 cm
2.54cm x 2.54cm x 2.54cm = 16.4 cm3 Answer in Liters1 liter =
Therefore:1000 CC
5000 cc = 5.0 L
! Calculating Piston Displacement !
Engine Measurement - Part 2
1 in =3
16.4 cm3
Compression Ratio's
CR = the comparison of the volume at BDC compared to TDC( how much the air fuel mixture is compressed )
Largest determining factor for amount of power a motor producesThe more a A/F mixture is compressed the more Power !!
CR Ratio = Volume at BDCVolume at TDC
PD + Combustion Chamber DisplacementCombustion Chamber Displacement
CR = PD + VCCVCC
=
CombustionChamber
Displacement
PistonDisplacement
CombustionChamber
Displacement
Engine Measurement - Part 2
! Calculating Compression Ratio’s !
Ex #1 PD = 65.6 CCVCC = 8.2 CC
CR = PD + VCCVCC
CR = 65.6 CC + 8.2 CC8.2 CC
CR = 9 to 1 or 9:1
Engine Measurement - Part 2
Engine Measurements Part 2! Calculating Compression Ratio’s !
Ex #2 Bore = 3.5”Stroke = 3.5”4 cylVCC = 4.5 cin
CR = PD + VCCVCC
CR = PD + 4.5 cin4.5 cin
PD = (B/2) x S x # cyl2
PD = (3.5”/2) x 3.5” x 1 cyl2
PD = 33.7 cin
CR = 33.7 cin + 4.5 cin4.5 cin
CR = 8.5 to 1 or 8.5:1
