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Air-Standard Cycles

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Higher ratios produce

autoignition andknocking

Analysis of Otto cycleAnalysis of Otto cycle

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Air

Combustion

mixture

He


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5


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Analysis of Otto cycle

Thermal efficiency vs. compression ratio for

different values of the adiabatic exponent

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( ) ( ) ( ) ( )1 1 1

1 1m

p rp

r

= +

( )

( ) ( )1

1

1 1m

p rp

r

=

1=

Mean effective pressure vs. pressure ratio for different values of

compression ratio r.

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5. Analysis of Diesel cycle

( ) ( )11

11 1r

=

+

For dual cycle, thermal efficiency has been

defined as

is used for thermal efficiency of Diesel

cycle. We get

(.1!"

#

1p

p= =

( )11 11

1r

=

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Figure $.# Thermal efficiency vs. cut%off

ratio at different compression ratios and

adiabatic exponents.

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Mean effective

pressure,

( ) ( ) ( ) ( )1 1 1

1 1m

p rp

r

= +

1=

( ) ( ) ( )1 1

1 1m

p rpr

=

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6. Comparison of the cycles

The significant parameters in cycle analysis are compression

ratio, pea& pressure, pea& temperature, heat addition, heat

re'ection, and the net or&. )n order to compare the

performance of these cycles, some of the parameters are &eptfixed.

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6.1. For the same compression ratio and heat addition

Figure *.1. p%+ and T%s diagrams having the same compression

ratio and heat addition for the three cycles.

Otto Dual Diesel > >

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6.2. For the same compression ratio and heat rejection

Figure *.#. p%+ and T%s diagrams having the same compression

ratio and heat re'ection for the three cycles.

Otto Dual Diesel > >

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6.3. For the same same peak pressure, peak temperature

and heat rejection

Figure *.. p%+ and T%s diagrams having the same pea&

pressure, pea& temperature and heat re'ection for the three

cycles.Diesel Dual Otto > >

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6.4. For the same maximum pressure and heat input

Figure *.. p%+ and T%s diagrams having the same maximum

pressure and heat input for the three cycles.

Diesel Dual Otto > > (for the same,1Q

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6.6. For the same maim!m press!re and "or# o!tp!t

Figure *.-. T%s diagrams having the same maximum pressure

and heat input for the three cycles.

Diesel Dual Otto > >

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The net cycle work of an engine can be increased by either:

i) Increasing ther!"#)ii) Increase Qin#$%)

&

'# '!

QinWcycle

!

#

$

i)

(

ii)

Factors Affecting Work per Cycle

!"

("

(""

$""th

incycle

r

r

V

Q

VV

Wimep

=

=1

1#1

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Effect of Compression Ratio on Thermal Efficiency and ME

=

k

in

rr

r

VP

Q

P

imep 11

1111

k ! "#$

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/0T)23

Than& you for your attention

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class.ppt