Otto cycle

L

t

=Q -

Q

o

Diesel cycle

L

t

=Q -

Q

o

Sabathe cycle

p

v

o

t

q

q

q





1



- theoretical efficiency















 



2

3

3

4

1

5

2

3

3

4

1

5

1

1

T

T

T

T

k

T

T

T

T

c

T

T

c

T

T

c

v

p

v

t





























factors definition





2

3

p

p





3

4

v

v





2

1

v

v















 



2

3

3

4

1

5

2

3

3

4

1

5

1

1

T

T

T

T

k

T

T

T

T

c

T

T

c

T

T

c

v

p

v

t











































































































































1

1

1

1

1

1

1

1

3

4

2

3

2

3

1

5

2

1

2

3

2

3

4

3

1

5

1

T

T

T

T

k

T

T

T

T

T

T

T

T

T

T

T

T

k

T

T

T

t

t



























































1

1

1

1

3

4

2

3

2

3

1

5

2

1

T

T

T

T

k

T

T

T

T

T

T

t







2

3

p

p





3

4

v

v





2

1

v

v

1

4

5

1

2

1

2

3

3

4

4

5

1

2

2

3

3

4

4

5

1

5





























k

k

T

T

v

v

p

p

v

v

T

T

T

T

T

T

T

T

T

T

T

T







1

1

1

1

2

3

4

1

5

3

3

4

1

5

4

4

5























































k

k

k

k

k

v

v

v

v

v

v

v

v

v

v

T

T





































k

k

k

k

T

T

1

1

1

1

5























































1

1

1

1

3

4

2

3

2

3

1

5

2

1

T

T

T

T

k

T

T

T

T

T

T

t







2

3

p

p





3

4

v

v





2

1

v

v

































k

k

k

k

T

T

1

1

1

1

5

1

1

2

1

1

2





















k

k

v

v

T

T









2

3

2

3

p

p

T

T











3

4

3

4

T

T









1

1

1

1

1

1





































k

k

k

t









1

1

1

1

1

1



































k

k

k

t

Sabathe cycle theoretical efficiency

for Otto cycle: =1

1

1

1







k

t





1

1

1

1

1

1



















k

k

t

k

for Diesel cycle: =1

isothermal cooling with
temperature T

0

- cooling agent (?)

isobaric cooling with a
pressure p

0

- cylinder use (?)

isochoric cooling

c

o

b

o

a

o

T

T

T

_

_

_





c

t

b

t

a

t

_

_

_











ambient
temperature
T

o

a

z

n

S

D

p

P

i

i













4

2



p

i

– indicated pressure, S – piston jump, n – rotation frequency, z – cylinder number

D – cylinder diameter, a – for two-stroke engine: 1, a – for four stroke engine: 2

indicated power – inner power

4-stroke
engine

2-stroke
engine

delivered heat

useful energy

outlet losses

cooling losses

friction losses

theoretical and real cycles – a comparision

reversible processes

irreversible processes

an agent – an ideal gas

real gas

closed system

breathing system

an agent – fixed chemical

composition

an agent – variable

chemical composition

heat exchange through a
cylinder wall

conversion of chemical
energy to internal one

(combustion)

no leakages

leakages

mechanical friction losses

fuel parameters

• octane number –

a measure of

ability to no-tap combustion. Isooctane has
a octane number equal to 100, and heptane
has 0. a value of octane number for a fuel is
a percent of octane in a mixture of octane
and heptane of the same features as the
fuel combustion ability

.

• cetin number –

ability to ignition without a

delay. Cetin has a cetin number equal to 100, and
metylonaftalen has 0.