644 ENGINEERING THERMODYNAMICS

dharm
\M-therm\Th13-3.pm5

Initial pressure, p 1 = 1 bar

Initial temperature, T 1 = 30 + 273 = 303 K

Maximum pressure, p 3 = p 4 = 60 bar

Cut-off = 4% of stroke volume

Number of working cycles/sec. = 3.

(^34)
0.04 Vs
p (bar)
60
1
2
5
1 (30°C)
V(m )^3
Vc Vs
Fig. 13.21
(i) Air standard efficiency :
Now, swept volume, Vs = π/4 D^2 L = π/4 × 0.25^2 × 0.3
= 0.0147 m^3
Also, compression ratio, r =
VV
V
sc
c

• i.e., 9 =
  0 0147. +V
  V
  c
  c
  ∴ Vc = 0 0147
  8

. = 0.0018 m 3

∴ V 1 = Vs + Vc = 0.0147 + 0.0018 = 0.0165 m^3

For the adiabatic (or isentropic) process 1-2,

p 1 V 1 γ = p 2 V 2 γ

p 2 = p 1 × V

V

1

2

F

HG

I

KJ

γ

= 1 × (r)γ = 1 × (9)1.4 = 21.67 bar

Also,

T

T

2

1

= V

V

(^1) r
2
1
F (^11419)
HG
I
KJ

−
−−
γ
()γ ( ). = (9)0.4 = 2.408