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Unit-4
Air compressors
1. What is meant by single stage compressor?
In single stage compressor, the compression of air from the
initial pressureto the nal pressure is carried out in one cylinder
only.
2. What is meant by multi stage compressor?
In single stage compressor, the compression of air from the
initial pressure
to the nal pressure is carried out in more than one
cylinder.
3. Indicate the application of reciprocating compressors in
industry.
The applications of compressed air are as follows
o !neumatic bra"eso !neumatic drillso !neumatic #ac"so !neumatic
liftso $prays paintingo $hop cleaningo In#ecting fuel in diesel
engine
%. What are the ad&antages of multi stage compression with
inter cooling o&er
single stage compression for the same pressure ratio?
o It impro&es the &olumetric e'ciency for the gi&en
pressure ratio.o The si(e of the cylinders )i.e., high pressure and
low pressure* may
be ad#usted to suit &olume and pressure of the airo It
reduces the lea"age loss considerablyo It reduces the cost of the
compressor.
+. ene the mechanical e'ciency and isothermal e'ciency of a
reciprocating
air compressor.
-olumetric e'ciency is dened as the ratio of &olume of free
air suc"ed
into the compressor per cycle to the stro"e &olume of the
cylinder
/ -olume of free air ta"en per cycle
$tro"e &olume of the cylinder
0. Why clearance is necessary and what its eect of the
performance of
reciprocating compressor?
When the piston reaches top dead centre in the cylinder, there
is a dead
space between top and cylinder head. This space is "nown as
clearance space
and the &olume occupied by this space is "nown as clearance
&olume.
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. Which type of compression is the best in reciprocating
compressor?
Isothermal compression
. What is compression ratio?
4ompression ratio is dened as the ratio between total &olume
and clearance&olume.
4ompression ratio / )Total &olume*5)clearance
&olume*
6. What is meant by inter cooler?
7n inter cooler is a simple heat heat e8changer. It e8changes
the heat of
compressed air from the low9pressure compressor to the
circulating water before
the air enters to the high9pressure compressor. The purpose of
inter cooling is to
minimi(e the wor" of compression.
1:. What are the factors that aect the &olumetric e'ciency
of a reciprocating
compressor?
1. 4learance &olume
2. 4ompression ratio
11. ;i&e the e8ample for positi&e displacement
compressor.
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$pray in#ection
Water #ac"eting
Inter9cooling
@8ternal ns
Ay a suitable choice of cylinder proportion
10. What is clearance &olume?
The clearance &olume is the &olume within the cylinder
when the piston it
at the end of its inward tra&el plus the &olume within
the passages leading to the
&al&es.
1. What are the uses of air compressor?
o ri&ing a compressed air engine
o ri&ing pneumatic tools
o $pray painting
o Alast furnace and boiler furnace
o !neumatic controls
1. What is the classication of air and gas compressors?
o
