EASTERN MEDITERRANEAN UNIVERSITYEASTERN MEDITERRANEAN UNIVERSITYDEPARTMENT OF MECHANICAL ENGINEERINGDEPARTMENT OF MECHANICAL ENGINEERING

Wankel Rotary Enginesy g

Presented by: Asst. Prof. Dr. Hasan Hacisevki

1) History of Rotary Machines:1) History of Rotary Machines:1) History of Rotary Machines:1) History of Rotary Machines:•• TheThe rotaryrotary combustioncombustion enginesengines camecame intointo voguevogue inin thethe FirstFirstyy gg gg

WorldWorld WarWar ThereThere areare threethree mainmain typestypes ofof truetrue rotaryrotary enginesengines::

11)) WankelWankel typestypes basedbased onon eccentriceccentric rotorsrotors11)) WankelWankel typestypes basedbased onon eccentriceccentric rotorsrotors..22)) ScissorScissor actionaction typestypes usingusing vanesvanes oror pistonspistons..33)) RevolvingRevolving blockblock typestypes ('cat('cat andand mouse'mouse' type)type)..

•• DesignsDesigns forfor rotaryrotary enginesengines werewere proposedproposed asas earlyearly asas15881588 bybyRamelliRamelli..

•• TheThe adventadvent ofof thethe automobileautomobile inin 18961896 toto setset thethe stagestage forfor aa properproperrotaryrotary combustioncombustion engineengine..

•• Furthermore,Furthermore, itit tooktook FelixFelix WankelWankel toto cataloguecatalogue andand organizesorganizes 862862configurationconfiguration pairs,pairs, ofof whichwhich 278278 areare impracticalimpractical..

•• WankelWankel investigatedinvestigated 149149 designsdesigns..

•• PriorPrior toto 19101910,, moremore thanthan 20002000 patentspatents forfor rotaryrotary pistonspistons werewere filedfiled..

•• OtherOther earlyearly designsdesigns werewere mademade byby HuygensHuygens inin 16731673 andand KeplerKepler..

•• FrenchmanFrenchman SensaudSensaud dede LavaudLavaud obtainedobtained aa patentpatent forfor aa fourfour phasephaserotaryrotary pistonpiston engineengine inin 19381938,, twotwo yearsyears afterafter FelixFelix WankelWankel..

2) Development:2) Development:2) Development:2) Development:•• TheThe WankelWankel engineengine waswas developeddeveloped inin thethe 7070's's byby manymany companies,companies,

ee..gg.. byby GeneralGeneral MotorsMotors,, DaimlerDaimler BenzBenz,, PeugeotPeugeot andand MazdaMazda..

•• TheyThey builtbuilt altogetheraltogether overover oneone millionmillion wankelwankel engineengine--operatedoperated carscars..yy gg gg pp

•• BecauseBecause ofof thethe arisingarising environmentalenvironmental regulationsregulations andand inin thetheconsequenceconsequence ofof thethe oiloil crisiscrisis nono moremore investmentsinvestments werewere donedoneconsequenceconsequence ofof thethe oiloil crisiscrisis nono moremore investmentsinvestments werewere donedone..

•• OnlyOnly MazdaMazda continuedcontinued toto developdevelop atat thethe rotaryrotary engineengine (e(e..gg.. inin 19991999theythey producedproduced aa newnew carcar withwith aa wankelwankel engineengine inside)inside)theythey producedproduced aa newnew carcar withwith aa wankelwankel engineengine inside)inside)..

•• TheThe futurefuture ofof thethe WankelWankel engineengine lookslooks ratherrather darkdark..

3) Main types of3) Main types of RCERCE::3) Main types of 3) Main types of RCERCE::•• KKMKKM KreiskolbenmotorKreiskolbenmotor oror planetaryplanetary rotationrotation motormotor (PLM),(PLM),

di ti i h ddi ti i h d bb t tit ti i h li h l h ih i ThTh ttdistinguisheddistinguished byby oneone stationarystationary peripheralperipheral housinghousing.. TheThe rotorrotormovesmoves inin anan orbitorbit andand propelspropels anan eccentriceccentric shaftshaft.. ThisThis isis easiereasier totomanufacture,manufacture, cool,cool, andand maintainmaintain thanthan DKMDKM.. IntakeIntake andand exhaustexhaustpassagespassages areare betterbetter.. BetterBetter coolingcooling isis achievableachievable.. ItIt isis moremorep gp g ggcompactcompact.. ModernModern rotariesrotaries areare KKMKKM typestypes..

•• DKMDKM DrehkolbenDrehkolben MaschineMaschine oror singlesingle--rotationrotation engineengine (SIM),(SIM), thethegg gg ( )( )firstfirst RCE,RCE, hashas thethe distinctivedistinctive featurefeature ofof anan innerinner rotatingrotating housinghousingandand rotorrotor movingmoving inin circularcircular motionmotion aroundaround aa fixedfixed centralcentral shaftshaft..This requires disassembling the motor to changeThis requires disassembling the motor to change

k l ( h ) h h i ik l ( h ) h h i ispark plugs (three), perhaps the main reason itspark plugs (three), perhaps the main reason itwas discarded. However, DKM is the smootherwas discarded. However, DKM is the smootherof the two, and high rates beyond 25,000 rpmof the two, and high rates beyond 25,000 rpmare possible, Bearing loads are lighter.are possible, Bearing loads are lighter.

Fig.1Fig.1

4) How Rotary Engines Work:4) How Rotary Engines Work:4) How Rotary Engines Work:4) How Rotary Engines Work:•• InIn aa pistonpiston engine,engine, thethe samesame volumevolume ofof

(th(th li d )li d ) lt t llt t l ddspacespace (the(the cylinder)cylinder) alternatelyalternately doesdoesfourfour differentdifferent jobsjobs;; intake,intake, compression,compression,combustioncombustion andand exhaustexhaust..

•• AA rotaryrotary engineengine doesdoes thesethese samesame fourfourjobs,jobs, butbut eacheach oneone happenshappens inin itsits ownownpartpart ofof thethe housinghousing..pp gg

•• It'sIt's kindkind ofof likelike havinghaving aa dedicateddedicatedcylindercylinder forfor eacheach ofof thethe fourfour jobs,jobs, withwithhh ii ii i lli ll ffthethe pistonpiston movingmoving continuallycontinually fromfrom oneone

toto thethe nextnext.. Fig. 2Fig. 2

5) The Basics:5) The Basics:5) The Basics:5) The Basics:•• InIn aa rotaryrotary engine,engine, thethe pressurepressure ofof combustioncombustion isis containedcontained inin aa

h bh b f df d bb tt ff thth h ih i dd l dl d ii bb ff ffchamberchamber formedformed byby partpart ofof thethe housinghousing andand sealedsealed inin byby oneone faceface ofofthethe triangulartriangular rotor,rotor, whichwhich isis whatwhat thethe engineengine usesuses insteadinstead ofof pistonspistons..

•• TheThe rotorrotor followsfollows aa pathpath thatthat lookslooks likelike somethingsomething you'dyou'd createcreate withwith•• TheThe rotorrotor followsfollows aa pathpath thatthat lookslooks likelike somethingsomething you'dyou'd createcreate withwithaa SpiroSpiro graphgraph..

•• ThisThis pathpath keepskeeps eacheach ofof thethe threethree peakspeaks ofof thethe rotorrotor inin contactcontact withwith•• ThisThis pathpath keepskeeps eacheach ofof thethe threethree peakspeaks ofof thethe rotorrotor inin contactcontact withwiththethe housing,housing, creatingcreating threethree separateseparate volumesvolumes ofof gasgas..

•• AsAs thethe rotorrotor movesmoves aroundaround thethe chamberchamber eacheach ofof thethe threethree volumesvolumesAsAs thethe rotorrotor movesmoves aroundaround thethe chamber,chamber, eacheach ofof thethe threethree volumesvolumesofof gasgas alternatelyalternately expandsexpands andand contractscontracts..

•• ItIt isis thisthis expansionexpansion andand contractioncontraction thatthat drawsdraws airair andand fuelfuel intointo thethess ss e p s oe p s o dd co c oco c o d wsd ws dd ueue oo eeengine,engine, compressescompresses itit andand makesmakes usefuluseful powerpower asas thethe gasesgases expand,expand,andand thenthen expelsexpels thethe exhaustexhaust..

Fig. 3

The rotor and housing of a rotary engine from a Mazda RX-7:These parts replace the pistons cylinders valves connecting rodsThese parts replace the pistons, cylinders, valves, connecting rods

and camshafts found in piston engines.

6) Mazda RX6) Mazda RX 8:8:6) Mazda RX6) Mazda RX--8:8:•• MazdaMazda hashas beenbeen aa pioneerpioneer inin developingdeveloping productionproduction carscars thatthat useuse

rotaryrotary enginesengines..

•• TheThe RXRX--77,, whichwhich wentwent onon salesale inin 19781978,, waswas probablyprobably thethe mostmost,, ,, p yp ysuccessfulsuccessful rotaryrotary--engineengine--poweredpowered carcar..

•• TheThe lastlast yearyear thethe RXRX--77 waswas soldsold inin thethe UnitedUnited StatesStates waswas 19951995TheThe lastlast yearyear thethe RXRX 77 waswas soldsold inin thethe UnitedUnited StatesStates waswas 19951995..

•• TheThe MazdaMazda RXRX--88,, aa newnew carcar fromfromMazdaMazda hashas aa newnew awardaward winningwinningMazda,Mazda, hashas aa new,new, awardaward winningwinningrotaryrotary engineengine calledcalled thethe RENESISRENESIS..NamedNamed InternationalInternational EngineEngine ofof thethe YearYear20032003,, thisthis naturallynaturally aspiratedaspirated twotwo--rotorrotor

Fig. 4

,, yy ppengineengine willwill produceproduce aboutabout 250250horsepowerhorsepower..

7) The Parts:7) The Parts:7) The Parts:7) The Parts:•• A rotary engine has an ignition system and a fuelA rotary engine has an ignition system and a fuel--delivery system delivery system y g g yy g g y y yy y

that are similar to the ones on piston engines. that are similar to the ones on piston engines.

8) Rotor:8) Rotor:8) Rotor:8) Rotor:•• TheThe rotorrotor hashas threethree convexconvex faces,faces, eacheach ofof

whichwhich actsacts likelike aa pistonpiston..•• EachEach faceface ofof thethe rotorrotor hashas aa pocketpocket inin it,it, whichwhich

increasesincreases thethe displacementdisplacement ofof thethe engine,engine,allowingallowing moremore spacespace forfor air/fuelair/fuel mixturemixtureallowingallowing moremore spacespace forfor air/fuelair/fuel mixturemixture..

•• AtAt thethe apexapex ofof eacheach faceface isis aa metalmetal bladeblade thatthatformsforms aa sealseal toto thethe outsideoutside ofof thethe combustioncombustionchamberchamber..

•• ThereThere areare alsoalso metalmetal ringsrings onon eacheach sideside ofof thetherotorrotor thatthat sealseal toto thethe sidessides ofof thethe combustioncombustionchamberchamber..

•• TheThe rotorrotor hashas aa setset ofof internalinternal geargear teethteeth cutcutintointo thethe centercenter ofof oneone side,side, thesethese teethteeth matematewithwith aa geargear thatthat isis fixedfixed toto thethe housinghousing..

•• ThiThi titi d t id t i thth thth dd•• ThisThis geargear matingmating determinesdetermines thethe pathpath andanddirectiondirection thethe rotorrotor takestakes throughthrough thethe housinghousing..

Fig. 5

9) Housing:9) Housing:9) Housing:9) Housing:•• TheThe housinghousing isis roughlyroughly ovaloval inin shapeshape (it's(it's

act allact all anan epitrochoidepitrochoid))actuallyactually anan epitrochoidepitrochoid))..•• TheThe shapeshape ofof thethe combustioncombustion chamberchamber isis

designeddesigned soso thatthat thethe threethree tipstips ofof thethe rotorrotor willwillalwaysalways staystay inin contactcontact withwith thethe wallwall ofof thetheh bh b f if i hh l dl d ll ffchamber,chamber, formingforming threethree sealedsealed volumesvolumes ofof gasgas..

•• EachEach partpart ofof thethe housinghousing isis dedicateddedicated toto oneonepartpart ofof thethe combustioncombustion processprocess.. TheThe fourfoursectionssections areare::IntakeIntakeCompressionCompressionCombustionCombustionExhaustExhaust

•• TheThe intakeintake andand exhaustexhaust portsports areare locatedlocated inin thethehousinghousing.. ThereThere areare nono valvesvalves inin thesethese portsports..

•• TheThe exhaustexhaust portport connectsconnects directlydirectly toto thethe•• TheThe exhaustexhaust portport connectsconnects directlydirectly toto thetheexhaust,exhaust, andand thethe intakeintake portport connectsconnects directlydirectlytoto thethe throttlethrottle.. Fig. 6

10) Output Shaft:10) Output Shaft:10) Output Shaft:10) Output Shaft:•• TheThe outputoutput shaftshaft hashas roundround lobeslobes mountedmounted eccentrically,eccentrically, meaningmeaning thatthat theythey

areare offsetoffset fromfrom thethe centerlinecenterline ofof thethe shaftshaft..•• EachEach rotorrotor fitsfits overover oneone ofof thesethese lobeslobes..•• TheThe lobelobe actsacts sortsort ofof likelike thethe crankshaftcrankshaft inin aa pistonpiston engineengine..pp gg•• AsAs thethe rotorrotor followsfollows itsits pathpath aroundaround thethe housing,housing, itit pushespushes onon thethe lobeslobes..•• SinceSince thethe lobeslobes areare mountedmounted eccentriceccentric toto thethe outputoutput shaft,shaft, thethe forceforce thatthat thethe

rotorrotor appliesapplies toto thethe lobeslobes createscreates torquetorque inin thethe shaftshaft causingcausing itit toto spinspinrotorrotor appliesapplies toto thethe lobeslobes createscreates torquetorque inin thethe shaft,shaft, causingcausing itit toto spinspin..

Fig. 7The output shaft

11) How it’s put together:11) How it’s put together:11) How it’s put together:11) How it’s put together:

•• A rotary engine is A rotary engine is y gy gassembled in layers.assembled in layers.

•• TheThe twotwo--rotorrotor engineengine wewetooktook apartapart hashas fivefive mainmainlayerslayers thatthat areare heldheld togethertogetheraye saye s t att at a ea e e de d toget etoget ebyby aa ringring ofof longlong boltsbolts..

•• Coolant flows through Coolant flows through passageways surroundingpassageways surroundingall of the pieces.all of the pieces.

Fig. 8all of the pieces.all of the pieces.

Fig. 9

•• TheThe twotwo endend layerslayers containcontainthethe sealsseals andand bearingsbearings forforthethe sealsseals andand bearingsbearings forforthethe outputoutput shaftshaft..

•• TheyThey alsoalso sealseal inin thethe twotwosectionssections ofof housinghousing thatthatcontaincontain thethe rotorsrotors..

•• TheThe insideinside surfacessurfaces ofof thesethesepiecespieces areare veryvery smoothsmoothpiecespieces areare veryvery smooth,smooth,whichwhich helpshelps thethe sealsseals onon thetherotorrotor dodo theirtheir jobjob..

•• AnAn intakeintake portport isis locatedlocated ononeacheach ofof thesethese endend piecespieces..

Fi 10pp

Fig. 10One of the two end pieces of a two-rotor Wankel engine

•• TheThe nextnext layerlayer inin fromfrom thetheoutsideoutside isis thethe ovaloval--shapedshapedoutsideoutside isis thethe ovaloval shapedshapedrotorrotor housing,housing, whichwhichcontainscontains thethe exhaustexhaust portsports..

•• ThisThis isis thethe partpart ofof thethehousinghousing thatthat containscontains thetherotorrotor..rotorrotor..

Fig. 11Th t f th t h i th t h ld th tThe part of the rotor housing that holds the rotors

(Note the exhaust port location.)

•• TheThe centercenter piecepiece containscontainstwotwo intakeintake ports,ports, oneone forforppeacheach rotorrotor..

•• ItIt alsoalso separatesseparates thethe twotwoii ididrotors,rotors, soso itsits outsideoutside

surfacessurfaces areare veryvery smoothsmooth..

•• II thth tt ff hh tt ii•• InIn thethe centercenter ofof eacheach rotorrotor isisaa largelarge internalinternal geargear thatthatridesrides aroundaround aa smallersmaller geargearthatthat isis fixedfixed toto thethe housinghousingggofof thethe engineengine..

•• ThisThis isis whatwhat determinesdetermines thethebibi ff hhorbitorbit ofof thethe rotorrotor..

•• TheThe rotorrotor alsoalso ridesrides onon thethell i li l l bl b thth

Fig.12largelarge circularcircular lobelobe onon thetheoutputoutput shaftshaft..

gThe center piece contains another intake port

for each rotor.

12) Producing Power:12) Producing Power:12) Producing Power:12) Producing Power:•• RotaryRotary enginesengines useuse thethe fourfour--strokestroke

combustioncombustion cyclecyclecombustioncombustion cyclecycle..•• TheThe heartheart ofof aa rotaryrotary engineengine isis thethe rotorrotor..•• ThisThis isis roughlyroughly thethe equivalentequivalent ofof thethe pistonspistons

inin aa pistonpiston engineengine..ThTh ii dd ll i li l l bl b•• TheThe rotorrotor isis mountedmounted onon aa largelarge circularcircular lobelobeonon thethe outputoutput shaftshaft..

•• ThisThis lobelobe isis offsetoffset fromfrom thethe centerlinecenterline ofof thetheshaftshaft andand actsacts likelike thethe crankcrank handlehandle onon aawinchwinch givinggiving thethe rotorrotor thethe leverageleverage itit needsneedswinch,winch, givinggiving thethe rotorrotor thethe leverageleverage itit needsneedstoto turnturn thethe outputoutput shaftshaft..

•• AsAs thethe rotorrotor orbitsorbits insideinside thethe housing,housing, ititpushespushes thethe lobelobe aroundaround inin tighttight circles,circles,turningturning threethree timestimes forfor everyevery oneone revolutionrevolutionturningturning threethree timestimes forfor everyevery oneone revolutionrevolutionofof thethe rotorrotor..

•• AsAs thethe rotorrotor movesmoves throughthrough thethe housing,housing, thethethreethree chamberschambers createdcreated byby thethe rotorrotor changechangesizesize.. Fig. 13

I th W k l t i l ts es e..•• ThisThis sizesize changechange producesproduces aa pumpingpumping actionaction..

In the Wankel a triangular rotor incorporating a central ring gear

is driven around a fixed pinion within an oblong chamber.

13) The Four Strokes:13) The Four Strokes:13) The Four Strokes:13) The Four Strokes:IntakeIntake

•• TheThe intakeintake phasephase ofof thethe cyclecycle startsstarts whenwhenthethe tiptip ofof thethe rotorrotor passespasses thethe intakeintake portportthethe tiptip ofof thethe rotorrotor passespasses thethe intakeintake portport..

•• AtAt thethe momentmoment whenwhen thethe intakeintake portport isisexposedexposed toto thethe chamber,chamber, thethe volumevolume ofofthatthat chamberchamber isis closeclose toto itsits minimumminimumthatthat chamberchamber isis closeclose toto itsits minimumminimum..

•• AsAs thethe rotorrotor movesmoves pastpast thethe intakeintake port,port,thethe volumevolume ofof thethe chamberchamber expands,expands,drawingdrawing air/fuelair/fuel mixturemixture intointo thethedrawingdrawing air/fuelair/fuel mixturemixture intointo thethechamberchamber..

•• WhenWhen thethe peakpeak ofof thethe rotorrotor passespasses thetheintakeintake portport thatthat chamberchamber isis sealedsealed offoff Fig. 14intakeintake port,port, thatthat chamberchamber isis sealedsealed offoffandand compressioncompression beginsbegins..

Fig. 14The fuel/air mixture is drawn in the intake

port during this phase of the rotation.

CompressionCompressionpp

•• AsAs thethe rotorrotor continuescontinues itsits motionmotion aroundaroundthethe housinghousing thethe volumevolume ofof thethe chamberchamberthethe housing,housing, thethe volumevolume ofof thethe chamberchambergetsgets smallersmaller andand thethe air/fuelair/fuel mixturemixture getsgetscompressedcompressed..

•• ByBy thethe timetime thethe faceface ofof thethe rotorrotor hashasmademade itit aroundaround toto thethe sparkspark plugs,plugs, thethevolumevolume ofof thethe chamberchamber isis againagain closeclose totoitsits minimumminimum..

•• ThisThis isis whenwhen combustioncombustion startsstarts•• ThisThis isis whenwhen combustioncombustion startsstarts..

Fig. 15gThe mixture is compressed here.

CombustionCombustion

•• MostMost rotaryrotary enginesengines havehave twotwo sparksparkplugsplugs..p gp g

•• TheThe combustioncombustion chamberchamber isis long,long, soso thetheflameflame wouldwould spreadspread tootoo slowlyslowly ifif theretherewerewere onlyonly oneone plugplug..

•• WhenWhen thethe sparkspark plugsplugs igniteignite thethe air/fuelair/fuel•• WhenWhen thethe sparkspark plugsplugs igniteignite thethe air/fuelair/fuelmixture,mixture, pressurepressure quicklyquickly builds,builds, forcingforcingthethe rotorrotor toto movemove..

•• TheThe pressurepressure ofof combustioncombustion forcesforces thethett tt ii thth di tidi ti th tth t kkrotorrotor toto movemove inin thethe directiondirection thatthat makesmakes

thethe chamberchamber growgrow inin volumevolume..•• TheThe combustioncombustion gasesgases continuecontinue toto

expand,expand, movingmoving thethe rotorrotor andand creatingcreating Fig. 16pp gg ggpower,power, untiluntil thethe peakpeak ofof thethe rotorrotor passespassesthethe exhaustexhaust portport..

gThe mixture burns here, driving the rotor

around.

ExhaustExhaust

•• Once the peak of the rotor passes the Once the peak of the rotor passes the exhaust port the highexhaust port the high--pressurepressureexhaust port, the highexhaust port, the high--pressure pressure combustion gases are free to flow out the combustion gases are free to flow out the exhaust.exhaust.

•• As the rotor continues to move theAs the rotor continues to move theAs the rotor continues to move, the As the rotor continues to move, the chamber starts to contract, forcing the chamber starts to contract, forcing the remaining exhaust out of the port.remaining exhaust out of the port.

•• By the time the volume of the chamber isBy the time the volume of the chamber isBy the time the volume of the chamber is By the time the volume of the chamber is nearing its minimum, the peak of the nearing its minimum, the peak of the rotor passes the intake port and the whole rotor passes the intake port and the whole cycle starts again.cycle starts again. Fig. 17y gy g g

And the exhaust is expelled here.

14) Key Differences:14) Key Differences:14) Key Differences:14) Key Differences:Fewer Moving PartsFewer Moving Partsgg

•• TheThe rotaryrotary engineengine hashas farfar fewerfewer movingmoving partsparts thanthan aa comparablecomparable fourfour--strokestrokepistonpiston engineengine..

•• AA twotwo--rotorrotor rotaryrotary engineengine hashas threethree mainmain movingmoving partsparts:: thethe twotwo rotorsrotors andandthethe outputoutput shaftshaft..

•• EvenEven thethe simplestsimplest fourfour--cylindercylinder pistonpiston engineengine hashas atat leastleast 4040 movingmoving parts,parts,includingincluding pistons,pistons, connectingconnecting rods,rods, camshaft,camshaft, valves,valves, valvevalve springs,springs, rockers,rockers,timingtiming belt,belt, timingtiming gearsgears andand crankshaftcrankshaft..

•• ThisThis minimizationminimization ofof movingmoving partsparts cancan translatetranslate intointo betterbetter reliabilityreliability fromfromaa rotaryrotary engineengine.. ThisThis isis whywhy somesome aircraftaircraft manufacturersmanufacturers preferprefer rotaryrotaryenginesengines toto pistonpiston enginesengines..enginesengines toto pistonpiston enginesengines..

SmootherSmoother

•• AllAll thethe partsparts inin aa rotaryrotary engineengine spinspin continuouslycontinuously inin oneone direction,direction, ratherratherthanthan violentlyviolently changingchanging directionsdirections likelike thethe pistonspistons inin aa conventionalconventional engineenginedddodo..

•• RotaryRotary enginesengines areare internallyinternally balancedbalanced withwith spinningspinning counterweightscounterweights thatthatareare phasedphased toto cancelcancel outout anyany vibrationsvibrations..areare phasedphased toto cancelcancel outout anyany vibrationsvibrations..

•• TheThe powerpower deliverydelivery inin aa rotaryrotary engineengine isis alsoalso smoother,smoother, Because,Because, eacheachcombustioncombustion eventevent lastslasts throughthrough 270270 degreesdegrees ofof thethe outputoutput shaft'sshaft's rotationrotation..

•• ThisThis meansmeans thatthat aa singlesingle--rotorrotor engineengine deliversdelivers powerpower forfor threethree--quartersquarters ofofeacheach revolutionrevolution ofof thethe outputoutput shaftshaft..

•• CompareCompare thisthis toto aa singlesingle--cylindercylinder pistonpiston engine,engine, inin whichwhich combustioncombustionoccursoccurs duringduring 180180 degreesdegrees outout ofof everyevery twotwo revolutions,revolutions, oror onlyonly aa quarterquarterofof eacheach revolutionrevolution ofof thethe crankshaftcrankshaft..

SlowerSlower

•• SinceSince thethe rotorsrotors spinspin atat oneone--thirdthird thethe speedspeed ofof thethe outputoutput shaft,shaft, thethe mainmainmovingmoving partsparts ofof thethe engineengine movemove slowerslower thanthan thethe partsparts inin aa pistonpiston engineengine..gg pp gg pp pp gg

•• ThisThis alsoalso helpshelps withwith reliabilityreliability..

15) Advantages:15) Advantages:15) Advantages:15) Advantages:

•• MostMost notablenotable isis thatthat theythey areare considerablyconsiderably simplersimpler andand containcontain farfarfewerfewer movingmoving partsparts;; forfor instance,instance, theythey havehave nono valves,valves, valvevalve trains,trains,etcetc..

•• InIn addition,addition, thethe rotorrotor spinsspins thethe driveshaftdriveshaft directly,directly, soso therethere isis nono needneedforfor connectingconnecting rods,rods, aa conventionalconventional crankshaft,crankshaft, balancebalance assemblies,assemblies,gg ,, ,, ,,etcetc..

•• AllAll ofof thisthis makesmakes aa WankelWankel engineengine muchmuch lighterlighter typicallytypically halfhalf thatthatAllAll ofof thisthis makesmakes aa WankelWankel engineengine muchmuch lighter,lighter, typicallytypically halfhalf thatthatofof aa conventionalconventional engineengine withwith equivalentequivalent powerpower..

16) Challenges:16) Challenges:16) Challenges:16) Challenges:ThereThere areare somesome challengeschallenges inin designingdesigning aa rotaryrotary engineengine::gg g gg g yy gg

•• Typically,Typically, itit isis moremore difficultdifficult (but(but notnot impossible)impossible) toto makemake aa rotaryrotary engineenginemeetmeet UU..SS.. emissionsemissions regulationsregulations..gg

•• TheThe manufacturingmanufacturing costscosts cancan bebe higher,higher, mostlymostly becausebecause thethe numbernumber ofof thesetheseenginesengines producedproduced isis notnot asas highhigh asas thethe numbernumber ofof pistonpiston enginesengines..gg pp gg pp gg

•• TheyThey typicallytypically consumeconsume moremore fuelfuel thanthan aa pistonpiston engineengine becausebecause thethethermodynamicthermodynamic efficiencyefficiency ofof thethe engineengine isis reducedreduced byby thethe longlong combustioncombustion--chamberchamber shapeshape andand lowlow compressioncompression ratioratio..