2 2103471 Two Stroke Engine
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TWO STROKE ENGINE 2103471 Internal Combustion Engine
Transcript of 2 2103471 Two Stroke Engine
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TWO STROKE ENGINE
2103471 Internal Combustion Engine
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Two-Stroke Engines• No separate intake and exhaust
strokes
• One power stroke per revolution
• Two strokes per cycle
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Two Stroke Spark Ignition Engine
Stroke 1: Fuel-air mixture is introduced into the cylinder andis then compressed, combustion initiated at the end of
the stroke
Stroke 2: Combustion products expand doing work and thenexhausted
* Power delivered to the crankshaft on every revolution
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2-StrokeEngines
2-stroke
Reed
Valve
intake
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Two Stroke Spark Ignition Engine
Intake (“Scavenging”)
Compression Ignition
ExhaustExpansion
Fuel-air-oilmixture
Fuel-air-oilmixturecompressed
Crankshaft
Checkvalve
Exhaustport
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EPO – exhaust port openEPC – exhaust port closedIPO – intake port open
IPC – intake port closed
Exhaust area
Intake area
Two-Stroke CI Engine
scavenging
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Where are they used?
Small size engines
• Model engines, scooters, chainsaws,
motorcycles etc
Very large size
• Marine engines, power generationapplications
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Advantages
(Small size SI engines)
- Compact
- Light
- Simple
- Robust
- CHEAP
Disadvantages
-Poor scavenging (gasexchange)
- Short circuiting of fuel
- High thermal stresses
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Scavenging concepts
- Cross scavenging
- Loop scavenging
- Uniflow scavenging (through scavenging)
- Reverse loop scavenging
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Cross Loop Uniflow
Scavenging in Two-Stroke Engine
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Uniflow scavenging
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Reverse loop scavenging
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Scavenging parameters
Delivery ratio, λ d (Λ)Scavenging efficiency, ηsc
Trapping efficiency, ηtr
Charging efficiency, ηch
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Delivery ratio
mdel = mass of delivered fresh charge
m0 = Vd*ρa
o
del
d
m
m
=λ
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Scavenging models
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Scavenging models
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Tuning
Using the pressure waves to charge the cylinder
Expansion wave at EPO
Compression wave at EPC
Major improvement of power!
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Comparison tuned vs. untuned
