4 stroke engine working principle

4 stroke engine working principle

1. EME-505 I.C.ENGINES AND COMPRESSORS
UNIT-1
Engine Cycle Animation
Prepared by:
V.K.Yadav
GLBITM
20-May-21

2. 4-Stroke Engines
exhaust
intake
20-May-21

3. 4-stroke Cycle SI Engine
Principle of Operation
•Cycleofoperationiscompletedin4-
strokesofthepistonor2revolutionsofthe
crankshaft.
•Eachstrokeconsistsof180°,ofcrankshaft
rotationandhenceacycleconsistsof
720°ofcrankshaftrotation.
20-May-21

4. Contd..
4-stroke SI Engine Principle of Operation
•Theseriesofoperationsofanidealfour-
strokeSIengineareasfollows
1-SuctionStroke
2-CompressionStroke
3-ExpansionorPowerStroke
4-ExhaustStroke
20-May-21

5. Contd..
Principle of Operation
20-May-21

6. injector injector injector injector injector
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7. SuctionCompressionIgn.-Combn.ExpansionExhaust
4-stroke Cycle
SI Engine
Principle of Operation
20-May-21

8. Contd..
Principle of Operation
Stroke Valve Position
Suction Stroke
Suction Valve open
Exhaust Valve closed
Compression Stroke Both Valves closed
Expansion or Power
Stroke
Both Valves closed
Exhaust Stroke
Exhaust Valve open
Suction Valve closed
20-May-21

9. 2-StrokeEngines
2-stroke
Reed
Valve
intake
20-May-21

10. Two-stroke Cycle Engine
principle of Operation
•2&4stroke–Difference!-methodoffillingcylinder
withfreshcharge&removingburnedgasesfrom
cylinder.
•2strokeenginesuctionisaccomplishedby
air/chargecompressedincrankcase/byblower.
•Nopistonstrokesrequiredforsuction/exhaust
operations.
•2pistonstrokesrequiredtocompletecycle,
compressionandexpansionorpowerstroke.
•Noseparateintakeandexhaust
20-May-21

11. Two Stroke Spark Ignition Engine
•Stroke1:Fuel-airmixtureisintroducedintothe
cylinderand
•isthencompressed,combustioninitiatedatthe
endofthestroke
•Stroke2:Combustionproductsexpanddoing
workandthenexhausted
•Power delivered to the crankshaft on every
revolution
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12. 2-stroke engine Compression and power
stroke
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13. ARE YOU READY TO
COMPARE NOW???
20-May-21

14. 20-May-21

15. TWO STROKE ENGINES
Two-strokeenginesdonothavevalves,
whichsimplifiestheirconstructionand
lowerstheirweight.
Two-strokeenginesfireonceevery
revolution,whilefour-strokeenginesfire
onceeveryotherrevolution.Thisgives
two-strokeenginesasignificantpower
boost.
20-May-21

16. TWO STROKE ENGINES
+ points
Theseadvantagesmaketwo-strokeengineslighter,
simplerandlessexpensivetomanufacture.
Two-strokeenginesalsohavethepotentialtopack
abouttwicethepowerintothesamespace
becausetherearetwiceasmanypowerstrokesper
revolution.
Thecombinationoflightweightandtwicethepower
givestwo-strokeenginesagreatpower-to-weight
ratiocomparedtomanyfour-strokeenginedesigns.
20-May-21

17. TWO STROKE ENGINES
+ points
Two-strokeenginescanworkinany
orientation,whichcanbeimportantin
invertedflightsoraerobaticflights.
Astandardfour-strokeenginemay
haveproblemswithoilflowunlessit
isupright,andsolvingthisproblem
canaddcomplexitytotheengine.
20-May-21

18. TWO STROKE ENGINES
-points
Two-strokeenginesdon'tlastnearlyas
longasfour-strokeengines.Thelackof
adedicatedlubricationsystemmeans
thatthepartsofatwo-strokeengine
wearalotfaster.
Two-strokeoilisexpensive,andyou
needabout.Youwouldburnabouta
gallon(3.785ltrs)ofoilevery1,000
milesifyouusedatwo-strokeenginein
acar.
20-May-21

19. TWO STROKE ENGINES
-points
Two-strokeenginesdonotusefuel
efficiently,soyouwouldgetfewer
miles(1.6km)pergallon(3.785ltrs).
Two-strokeenginesproducealotof
pollution
--somuch,infact,thatitislikelythatyouwon't
seethemaroundtoomuchlonger.
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20. FUEL
INTAKE
20-May-21

21. COMPRESSION
20-May-21

22. COMBUSTION
&
EXHAUST
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23. TWO STROKE
OPERATION
TWO STROKE
OPERATION
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24. FOUR STROKE ENGINES
conventional Otto engines
20-May-21

25. FOUR STROKE ENGINE OPERATION
20-May-21

26. Comparison between two stroke and four
stroke engines

27. FOUR stroke Engine
CHARACTERISTICS (compared with 2 stroke engines)
FOUR STROKE ENGINES LASTS LONGER THAN TWO STROKE ENGINES . The
lack of a dedicated lubrication system means that the parts of a two-stroke engine
wear a lot faster.
FOUR STROKE ENGINES DON’T BURN OIL IN COMBUSTION CHAMBER . Two-
stroke oil is expensive, and you need about 113.36 grams of it per gallon of gas. You
would burn about a gallon of oil every 1,000 miles if you used a two-stroke engine in
a car.
FOUR STROKE ENGINES ARE MORE FUEL EFFICIENT . Two-stroke engines do
not use fuel efficiently, so you would get fewer miles per gallon.
FOUR STROKE ENGINES ARE CLEANER . Two-stroke engines produce a lot of
pollution
INVERTED FLIGHTS MAY NOT BE EASY IN FOUR STROKE ENGINES. Two-
stroke engines can work in any orientation, which can be important in acrobatic
flights. A standard four-stroke engine may have problems with oil flow unless it is
upright, and solving this problem can add complexity to the engine.
20-May-21

28. Advantages of Two-stroke Engines
Advantages(over 4-stroke Engines)
•Power developed nearly twice compared
•Work required to overcome the friction of the exhaust and
suction strokes is saved.
•More uniform turning moment -lighter flywheel
•Engines lighter & occupy less space
•Construction is simple -reduces maintenance problems
•Because of scavenging, burnt gases do not remain in the
clearance space as in case of four-stroke engines.
20-May-21

29. Disadvantages of Two-stroke Engines
Disadvantages(over4-strokeEngines)
•Highspeed-lessefficient-reducedvolumetricη
•Shortcircuitingincreasesfuelconsumption&reducesthe
thermalη
•Effectivecompressionisless
•Liabletocauseaheavierconsumptionoflubricatingoil.
•Withheavyloads,enginesgetheatedduetoexcessiveheat
produced.Alsoatlightloads,runningofengineisnotvery
smoothbecauseoftheincreaseddilutionofcharge.
20-May-21

30. Scavenging process in 2 stroke
Engines
•Scavenging??
•Thereplacementoftheproductsofcombustionin
thecylinderfromthepreviouspowerstrokewith
fresh-airchargetobeburnedinthenextcycle.
20-May-21

31. Theoretical Scavenging Processes
•Theactualscavengingprocessisneitherone
ofperfectscavengingnorperfectmixing.It
probablyconsistspartiallyofperfect
scavenging,mixingandshort-circuiting.
•Thefirstphaseofthescavengingprocessisa
perfectscavengingprocesswhichthen
graduallychangesintoacompletemixing
process
20-May-21

32. Types of 2 Stroke Engines-Based on
scavenging techniques
1-Basedonscavenging(sweepingoutofburnt
gasesbyfreshcharge)method
i)Crankcase&ii)Separatelyscavengedengine
2-Basedonscavengingprocess(airflow)
i)Crossflowscavenging,
ii)Loopscavenging(MAN,Schnuerle,Curtistype)
iii)Uni-flowscavenging(opposedpiston,poppet
valve,sleevevalve)
3-Basedonoverallport-timing
i)Symmetrical&ii)Unsymmetricalscavenging
20-May-21

33. Crankcase-scavenged
20-May-21

34. Separately Scavenged Engine
Loop-scavenged 2-stroke Engine
20-May-21

35. Classification
Based On Scavenging Process
Cross Loop Uniflow
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36. Classification
Based On Scavenging Process…
Uni-flow Scavenging by Poppet Valve
20-May-21

37. Scavenging Pumps
20-May-21

38. Comparison of Two-stroke
CI And SI Engines
•2-stroke SI engine suffers from
-fuel loss& idling difficulty.
-fuel loss & hence low indicated thermal efficiency
-(SI) More Dilution, Short Circuit, Back Firing at low
speeds, less air available for combustion after
scavenging
-Fuel injection (CI) improves idling, avoids loss of
fuel and also eliminates backfiring as there is no fuel
present in the inlet system.
20-May-21

39. SI Engine Advantages
The SI engine offers the following
advantages
•Low initial cost.
•Low weight for a given power output.
•Smaller size for a given power output.
•Easy starting.
•Less noise.
•Less objectionable exhaust gas odor and less
smoke.
20-May-21

40. SI engine application
•UsesofTwostroke(SI)petrolenginesfindsextensiveusein
motorcycles,scooters,mopeds,pleasuremotorboats,etc.,
becauseofsimplicityandlowcost.
•Moped(50cc)with1.5KWat5000rpm
•Scooter(100cc)with3.5KWat5000rpm
•Scooter(150cc)with5KWat5300rpm
•Motorcycle(250cc)with9KWat4500rpm
•UsesofFourstrokepetrolenginesfindsextensiveusein
motorcycles,cars,jeeps,buses,trucks,pumpingsets,mobile
electricgeneratingsetsbecauseofsimplicityandlowcost.
•Fiatcar(1089cc)4-cylinderwith32KWat5000rpm
•Americancar6cylinderwith185KWat5000rpm
•Jeeps(4000cc)6cylinderwith90KWat
20-May-21

41. CI engine application
•UsesofTwostroke(CI)Dieselenginesfindsextensiveuseinship
propulsion
•Shipswith20,000KWat120rpm
•400-900mmbore
•UsesofFourstrokedieselengines(Mostversatileandthermally
efficient)
•100-4500rpmand1to35000KW
•Tractors-30KW
•Jeep,buses,trucks–40to100KW
•Dieselengines-morethan100KW
•Earthmovers–superchargedwith200to400KW
•Locomotives–600to4000KW
•Marine–100to35000KW
•Maindrawback–Vibrationandunpleasantsmellfromsmoke
20-May-21

42. CI Engine Advantages
TheCIengineoffersthefollowingadvantages.
•Lowspecificfuelconsumptionatbothfullloadand
partloadconditions.
•Utilizeslessexpensivefuels.
•Reducedfirehazard
•Longoperatinglife.
•Bettersuitedforsupercharging.
•Bettersuitedfortwo-strokecycleoperating,asthere
isnolossoffuelinscavenging.
20-May-21

43. Bajaj Pulsar
Specifications
www.mypulsar.com
•Bajaj pulsar 200 NS Bajaj pulsar 150
•Type : SOHC-4V-Liquid cooled 4 stroke DTSI
•Cost in delhi Rs. 85000
•Bore: 72 mm
•Stroke: 49 mm
•Displacement: 199.5 cc 149 cc
•Max power: 23.52 PS@9500 15.06 PS@9000
•Max torque: 18.3 NM @8000 12.5 Nm @6500
•Fuel system: Carburettor
•6 gears
•Combustion system: Triple spark 4 valves engines 27 % faster than twin spark and
50% faster than single spark
•Bajaj Discover 125 ST
•Cost Rs. 54200
•125 cc
•4 valves
•65 Km/hr

47. The 4-Stroke Engine
•Stroke Breakdown: (18)
–Intake:
–Compression:
–Power:
–Exhaust:

52. Four Stroke Cycle Animation
•Four Stroke Spark Ignition Engine

53. High Performance Application

55. 4-Stroke Engine
•Valve Operation During a Cycle:
(4)
•Briggs & Stratton 3hp Engine:
(3)
•Firing Order: (4) (exercise)
•4-Stroke Characteristics: (12)

57. The 2-Stroke Cycle Engine:
•Introduction: (3)
•Strokes: (2)
•No Valve Mechanisms: (3)

58. 2-Stroke Engine
•Stroke Breakdown: (11)
–Power:
–Compression:
•Differences Between The 2 & 4 Stroke:
(3)
•Advantages of the 2-Stroke: (8)
•Disadvantages of the 2-Stroke: (6)