Otto CyclePowePoint

8/9/2019 Otto CyclePowePoint

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Otto Cycle


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Objective

Give background information about Otto Cycle

Further detail such as:

Applications

History


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History

Invented in !"# by $eau

de %ochas

In !" &ean &oseph 'tienne(enoir created a double)acting engine

%an on illuminating gas

*+ e,ciency

In !"# -icolaus August

Otto .ested a (enoir engine

replica

Created an engine toincrease e,ciency andreliability

Increase e,ciency bycompressing fuel mi/tureprior to ignition

Failed in creating the animproved (enoir 'ngine


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History Cont0

In !1" -icolaus August Otto

and 'ugen (angen created acombustion engine

First engine to compressfuel mi/ture prior tocombustion

Highest e,ciency of its

time

In !!2 Otto and (angencreated the 3rst high)speedengine

In !!4 Otto and (angen

created the 3rst automobileto be e5uipped 6ith an Otto'ngine

7ehicle 8odel 9aimler%eit6agen

First vehicle po6ered byan internal combustionengine

sed a four stroke enginebased on Otto;s design


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C y c l e

9i a gr

am s


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C y c l e

9i a gr

am s


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C y

c l e9i a gr am

s )@ 7


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C y c l e9

i a gr a

m). A


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# troke

'ngine•Involves just a po6erstroke and compressionstroke

•

imple= ine/pensive=high po6er to 6eight andpo6er to volume ratiosBgood for smaller engines

•Generally less e,cient

than a * stroke


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Advantages of a # stroke

spark ignition engines

impler con3guration as compared to a * strokeengine >#?

@roduce about t6ice as much po6er ascompared to a * stroke engine0

.his is due to the fact that a # stroke engine has apo6er stroke in every revolution0 >#?

Di d t f 2


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Disadvantages of 2stroke spark ignition

engines

hort engine life .his is due to a lack of a dedicated lubrication

system= 6hich causes the parts of a # stroke engineto 6ear do6n much faster0 >#?

8any # stroke engine applications involve high

%@8s0 .he more revolutions an engine e/periences=the faster it 6ill 6ear out0 >#?


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stroke spark ignition

engines

%e5uire more oil

# stroke engines re5uire about * ounces of Be/pensive oil per liter ofgas0 >#?

(ess fuel e,cient >#?

High amounts of pollution

@ollution comes from the combustion of the oil0 As a t6o stroke engine

becomes more 6orn= it can produce huge clouds of oily smoke0 >#? .he other reason for pollution is the fact that the airDfuel mi/ture leaks

out through the e/haust port each time it is loaded into thecombustion chamber0 >#?


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* troke 'ngine

Involves compression=

e/pansion= e/haust= andintake strokes

8i/ture of mechanical andchemical methods to drivethe piston and crankshaft


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Advantages of a * stroke

park Ignition

8ore tor5ue >2?

Although a # stroke engine is kno6n for producing higheramounts of speed and po6er= a * stroke engine sho6smore tor5ue at lo6 %@8s than # stroke engines0 .he e/trator5ue has to do a lot 6ith the e,ciency of the fuel burn0 A* stroke engine uses almost all of its fuel to impart po6er

to the crankshaft0

8ore reliable and relatively 5uieter operation0


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Advantages cont;d

(onger (ife Four stroke engines last much longer and use less oil than # stroke engines0 .he

more revolutions an engine performs= the 5uicker it 6ill 6ear out0 Four strokeengines are typically designed for lo6 %@8 applications= 6hich results in a longer

life0 >2?

Cleaner operation as compared to # stroke engines0 A * stroke engine has a dedicated oiling system that is kept separate from the

combustion chamber= 6hich ensures that the only thing burning in the engine isgasoline0 >2?

8ore Fuel e,cient >2? * stroke engines have a dedicated intake= po6er and e/haust stroke= 6hich keeps

fuel)to)e/haust crossover at a minimum0


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stroke Spark Ignition

engines

Cannot achieve high compression ratios as

compared to the 9iesel Cycle0 .his is due to thefuel prematurely igniting0 >?

@roduce only half as much po6er as a # strokeengine because a * stroke engine has only one

po6er stroke every t6o cycles0 >#?

8ore complicated and higher maintenance costsas compared to # stroke engines0 >#?


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',ciency Otto engines are

about 2E+ e,cient0

2E+ of the energygenerated by

combustion isconverted into usefulrotational energy atthe output shaft ofthe engine0

.he remainder beinglosses due to friction=engine accessories=and 6aste heat0


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@o6er Output

.he ma/imum amount of po6er generated by an engine is determined by the ma/imum amount of airingested0

.he amount of po6er generated by a piston engine is related to its sie Bcylinder volume= in four)strokedesign= volumetric e,ciency= losses= air)to)fuel ratio= the calori3c value of the fuel= o/ygen content of the air

and speed B%@80

.he speed is ultimately limited by material strength and lubrication0 7alves= pistons and connecting rods suersevere acceleration forces0 At high engine speed= physical breakage and piston ring utter can occur= resultingin po6er loss or even engine destruction0

%ing utter compromises the seal bet6een the ring and the cylinder 6all 6hich results in a loss of cylinderpressure and po6er0

If an engine spins too 5uickly= valve springs cannot act 5uickly enough to close the valves0 .his is commonly

referred to as Jvalve oatJ= and it can result in piston to valve contact= severely damaging the engine0

At high speeds the lubrication of piston cylinder 6all interface tends to break do6n0 .his limits the pistonspeed for industrial engines to about E mDs0


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%eal


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@otential Improvements) .urbocharger

.urbine driven device=

increases e,ciency andpo6er by forcing moreairDfuel into combustionchamber

.urbine is driven by e/haust

gas

Commonly used on vehicleand construction e5uipmentengines


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@ros:)8akes use of other6ise 6asted energy from

e/haust to drive turbine)Higher adiabatic e,ciency than superchargers)9oes not place direct mechanical load on engine

Cons:) 'ngine must reach su,cient speed to spoolturbine= i0e0 there is spool lag

olution: t6in charge through use of a superchargerand turbocharger both

@rosDCons


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'thics

.he e,ciency of the engine used aects the rate

of CO# emission0 Otto cycle more e,cient than agas turbine and jet engine0


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ources

>? Cengel= Kunus0 L.hermodynamics: An 'ngineering Approach = !th 'dition0LThermodynamics 8th Edition Yunus Cengel 0073398179 97800733981740 8cGra6 Hill

'ducation= n0d0 #? $rain= 8arshall0 LHo6 .6o)stroke 'ngines

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