TITLE.PM5

642 ENGINEERING THERMODYNAMICS

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\M-therm\Th13-3.pm5

Example 13.23. The swept volume of a diesel engine working on dual cycle is 0.0053 m^3
and clearance volume is 0.00035 m^3. The maximum pressure is 65 bar. Fuel injection ends at 5
per cent of the stroke. The temperature and pressure at the start of the compression are 80°C and
0.9 bar. Determine the air standard efficiency of the cycle. Take γ for air = 1.4.
Solution. Refer Fig. 13.20.

Fig. 13.20

Swept volume, Vs = 0.0053 m^3

Clearance volume, Vc = V 3 = V 2 = 0.00035 m^3

Maximum pressure, p 3 = p 4 = 65 bar

Initial temperature, T 1 = 80 + 273 = 353 K

Initial pressure, p 1 = 0.9 bar

ηdual =?

The efficiency of a dual combustion cycle is given by

ηdual = 1 –

11

()^111

.

rγ ()()

βργ

− ββγρ

−

−+ −

L

N

M

M

O

Q

P

P

...(i)

Compression ratio, r =

V

V

VV

V

sc

c

1

2

0 0053 0 00035

0 00035

=

+

=

..+

.

= 16.14

[]Q VV 2 ==c Clearance volume

Cut-off ratio, ρ =

V

V

VV

V

VV

V

s sc

c

4

3

3

3

5

=^100005

+

=. + ()Q VVV 23 ==c

=

0 05 0 0053 0 00035

0 00035

...

.

×+

= 1.757 say 1.76