Piston compressors
Piston compressors
theoretical compression process
– illustration – p-v & T-s graphs
2
t
2
p
2
s
T
s
2
s
1
2
T
2
p
case
-isothermal process (1-2
t
) – an ideal cooling
-isentropic process (1-2
s
)– reversible adiabatic process
-reversible polytrophic process (1-2
p
)
V
1
= V
c
– a cylinder
volume
work of compression / theoretical
pressure
1
1
1
1
2
1
1
n
n
t
p
p
V
p
n
n
L
1
V
p
L
t
t
=>
a
p
p
p
n
n
p
p
n
n
t
1
1
1
2
1
1
1
Theoretical pressure with a clearances
volume
cylinder volume
V
c
=V
1
=V
d
+V
b
piston displacement
(displacement volume) V
d
clearance volume
V
b
=V
3
volume of sucked gas with a
pressure p
1
V
s
=V
1
-V
4
1
2
3
4
P
2
P
1
n
1
n
2
p
v
V
ss
V
b
V
sk
displacement
volume V
d
clearance volume
V
b
=V
3
clearance volume
coefficient
13
,
0
03
,
0
3
d
o
V
V
1
2
3
4
P
2
P
1
n
1
n
2
p
v
V
ss
V
b
V
sk
Theoretical compression with a
clearances volume
displacement
volume V
d
clearance volume
V
b
=V
3
suction coefficient
d
s
d
s
V
V
V
V
V
4
1
describes reduction of a suction volume as a result of expansion
of a gas left at the clearance volume after the gas removal
d
d
d
d
d
s
V
V
V
V
V
V
V
V
V
V
V
4
3
4
3
4
1
1
d
o
s
V
V
4
1
o
n
d
d
p
p
V
V
V
V
V
V
2
1
1
2
3
3
4
4
1
1
1
2
2
1
1
2
0
0
1
1
2
0
n
n
s
p
p
p
p
Theoretical compression with clearance volume
and pressure drops during suction and gas
removal
volumetric efficiency
1
2
3
4
P
2
P
1
n
1
n
2
p
v
V
ss
V
b
V
sk
d
s
v
V
V
reduction of a suction
volume due to expansion of
a gas from a clearance
volume and pressure losses
during suction and gas
removal
d
indicator diagram
r
i
i
d
r
d
i
i
n
s
D
p
P
s
D
V
n
V
p
P
4
4
2
2
1
2
3
4
p
2
p
1
n
1
n
2
p
v
V
ss
V
b
V
sk
p
i
=var
=var
d
t
t
t
t
t
r
t
t
m
P
l
l
m
n
V
p
P
1
r
i
i
i
r
r
d
i
i
m
P
l
l
m
n
V
p
P
internal efficiency
i
i
t
t
r
i
t
r
i
t
t
i
t
i
P
P
m
m
P
P
m
P
m
P
l
l
i
i
t
t
r
d
i
r
r
d
t
t
r
sk
i
r
r
t
i
p
p
m
n
V
p
m
n
V
V
p
m
n
V
p
m
n
V
p
0
3
1
1
)
(
m
r
measured; m
t
estimated
mechanical efficiency
e
i
r
e
r
i
e
i
m
P
P
m
l
m
l
l
l
overall efficiency
i
e
t
e
i
t
r
i
t
m
i
e
i
i
t
e
t
o
P
P
P
P
m
m
P
P
l
l
l
l
l
l
r
m
r
s
d
r
s
d
r
s
t
n
V
n
V
V
n
V
m
0
3
1
1
r
t
t
n
V
p
P
1
- measured
- where P
t
– depends on a model process
multistage compressor
1
1
1
1
1
1
n
n
x
tI
p
p
V
p
n
n
l
1
1
1
2
n
n
x
X
x
tII
p
p
V
p
n
n
l
1
1
1
T
R
m
V
p
V
p
x
x
tII
tI
l
l
2
1
1
2
1
1
p
p
p
p
p
p
p
x
n
n
x
n
n
x
1
x'
3
4
P
x
P
1
p
v
P
2
2'
x"
2
t=const
if assume:
than
:
volumetric efficiency
d
s
d
B
A
V
V
V
V
V
V
A
2
3
4
P
2
P
1
p
v
V
s
V
d
B
1
m
2
m
1
theoretical model and a real
processes
1
2
P
2
P
1
n
1
v
1
2
4
P
2
P
1
n
1
n
2
v
V
s k
4
V
s s
1
2
3
4
P
2
n
1
n
2
p
v
V
s s
1
2
3
P
2
P
1
p
v
p
s
p
t
p
3
p
2
4
3
1
a real indicator diagram
b
suction volume and a
compression ratio
heat exchange and a
compression processes
T-s diagram