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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Expt No : Batch : .
Date :. Student ID :
PERFORMANCE TEST ON TWO- STAGE RECIPROCATING AIR COMPRESSOR
Aim:
To conduct a performance test on the reciprocating air
compressor and to plot the following curves.
1. Adiabatic efficiency Vs Pressure ratio
2. Isothermal efficiency Vs Pressure ratio
3. Volumetric efficiency Vs Pressure ratio
Specifications:
Compressor : Low Pressure side High Pressure side
Bore 79mm 63mm
Stroke 80mm 80mm
Free Air Delivery : 500 lpm
Diameter of pipe (d1) : 57 mm
Diameter of orifice (d2) : 12 mm
Maximum Pressure : 15 kg/cm2
Coefficient of discharge (Cd) : 0.6
Torque arm length : 230 mm
Apparatus Required:
Air compressor test rig and Stop watch
Theory:
Atmospheric Pressure,
Pa =
N/m2
Where, lb = Barometer reading in mm of Hg
Absolute Inlet Pressure,
P1 = ( N/m2
Where, = Specific weight of water = 9810 N/m3
= Stabilization tank manometer reading in m of water
Delivery Inlet Pressure, P2 = (
) N/m2
Where, = Delivery pressure gauge reading in kgf/cm2
Pressure Ratio,
Density of Air,
Where, R = Characteristic gas constant = 287.14 J/Kg K T1 =
Temperature at suction in K
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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Observations:
Pre
ssu
re
rati
o
Pr
Ab
solu
te
del
iver
y
pre
ssu
re
P2
Ab
solu
te
inle
t
pre
ssu
re
P1
Tem
p
at
Del
iver
y
T2
K
Sp
eed
of
com
pre
ss
or
Nc
rpm
Spee
d
of
moto
r
Nm
rpm
Spri
ng
bal
ance
Rea
din
g
S kg
Ori
fice
Man
om
eter
Rea
din
g
Hw
m o
f w
ater
h2
cm
h1
cm
Su
ctio
n s
ide
Man
om
eter
Rea
din
g
hw
m o
f w
ater
h2
cm
h1
cm
Gau
ge
Pre
ssu
re
Pg
Sl
No
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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Head causing Flow,
m of air
Where, = Density of water = 1000 kg/m3
= Orifice meter manometer reading in m of water
Volume of Air Actually Compressed
(
Where, Cd = 0.6
A = Area of the orifice =
Ha = Head causing the flow
Swept Volume,
m3/s
Where, A = Area of cross section of LP cylinder =
Nc = Speed of compressor crank shaft in rpm
Volume of air reduced to NTP,
m3/s
Where, T0 = 273 K
P0 = 1.03 104 9.81 N/m2
Volumetric Efficiency
%
Actual work done on Compressor,
(a) Using Dynamometer
= 60
NT2 watts
Where, N = Speed of the motor in RPM
T = Torque = Load X Arm length N-m
(b) Using Energy meter
= 1000t
3600
K
20 watts
Where, K = Energy meter constant = 1600 Impulses/kWh
t = Time for 20 impulses in seconds
Isothermal work done,
watts
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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Adia
bat
ic
effi
cien
cy
ad
ia
%
Isoth
erm
al
effi
cien
cy
is
o
%
Adia
bat
ic w
ork
done
per
sec
ond
Wad
ia
Wat
ts
Isoth
erm
al
work
done
per
sec
ond
Wis
o
Wat
ts
Act
ual
work
don
e
per
sec
ond
Wac
t
b
Wat
ts
a
Wat
ts
Volu
met
ric
effi
cien
cy
V
ol
%
Volu
me
of
air
at N
TP
V0
Volu
me
of
air
actu
ally
com
pre
ssed
V1
Hea
d
Cau
sing
flow
Ha
m o
f ai
r
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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Isothermal Efficiency,
Rev. Adiabatic Work,
[(
)
] watts
Adiabatic Efficiency
Procedure:
Start the compressor on NO LOAD condition. For this purpose the
outlet valve shall kept fully open.
When the motor picks up speed, the outlet valve can be
closed.
The compressor should be adjusted to deliver air at a particular
delivery pressure by adjusting the shut
off valve of the storage tank.
Note the delivery pressure gauge reading, the manometer
readings, load on spring balance, speed, time
for 20 impulses of energy meter, etc.
Repeat the experiment for different delivery pressures up to 6
kgf/cm2.
Switch off the compressor at NO LOAD condition.
Tabulate the observations calculate the required values and plot
the necessary curves.
Result:
Inference and Discussions:
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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Sample Calculations:
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Two Stage Reciprocating Air Compressor Test Rig
Aerospace Engineering Department, IIST
Typical Graph
