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By:- Dinesh Kr. Sharma

  Lecturer 

  ME- SKIT

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Contents

IntroductionWorking of Otto cycle engine

Conventional Otto cycle engine

Miller cycle engine

Introduction to Compression Ratio (CR)

Variable Compression Ratio (VCR)engine

Miller cycle engine wit VCR

Computer simulation model

Results

Conclusions

References

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Model Of 4-cylinder Otto ycle En!ine

  Working model of Otto Cycle

engine

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  Otto Cycle

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Miller Cycle Engine with S-VT (Sequential Valve Timing)

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Is the ratio "y #hich the fuel$air mi%ture is com&ressed

"efore it is i!nited.

Limited in con'entional en!ines due to auto-i!nition.

Determines ho# efficiently the en!ine can utili(e theener!y in the fuel.

) of traditional en!ine is fi%ed and is a com&romise

across a #ide ran!e of o&eratin! conditions.

) for &assen!er cars ran!es "et#een *:+ and +,:+#hile ) for diesel en!ines can "e much hi!her.

What is Compression Ratio (CR)

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Disad'anta!es of 5i%ed )

!ecause CR cannot vary to fit a wide range of

operating conditions"

 #ower output is reduced

$uel efficiency is not optimi%ed

#ollution from combustion is not minimi%ed&

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Variable Compression Ratio (VCR)

Wat is it'e combustion camber volume Vc is altered to meet

te power needs to te veicle&

*t low power levels ig CR captures fuel efficiency

benefits&*t ig power levels low CR prevents knock&

CR modified to meet power demand (CR+s range from,"- to .-"-)

Increased fuel efficiencyClaims of up to /01 reduction in fuel consumption

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Miller Cycle !ngine "ith VCRModification in VCR engine by VV&

Miller Cycle wit variable compression ratio&

It as better results tan Miller cycle and Conventional

Otto Cycle in performance&2ess fuel consumption&

Improved efficiency&

3ngine can installed in every sort of veicle&

2ess maintenance&

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Comp#ter Sim#lation Model

Computer model structure for entropy generatin calculation2Bernardo )i"eiro 8or!e Martins9 nt;nio <unes 6,,=3

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!ngine characteristics and "orking conditio

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!ntropy $eneration in engineMain causes of Entropy generation

$ree 34pansionCombustion

5eat transfer

$riction

$low troug valves

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!ntropy generation d#e to Comb#stion

3ntropy generated during combustion corresponds to te

entropy increase due to te cemical reactions inside te

engine cylinder and eat transferred witin te mass ofgas&

*mount of entropy generation is calculated by7

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!ntropy generation d#e to 'eat transfer 6uring working of engine eat is e4canged between te

cylinder carge and te cylinder walls and ten between

te engine and te surrounding environment&

5eat transfer is a significant process during te

combustion and e4pansion stroke&

It is calculated using following formula7

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!ntropy generation d#e to %riction

8eneration of entropy during working of engine occurs

due to internal friction also&

*mount of entropy generated due to $riction is7

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Entropy generated in engine

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Entropy generated in each cycle

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