Government Poytechnic, Miraj
Department of Mechanical Engineering Seminar Report on
Reciprocating Air Compressor Compressor Submitted by: Miss Pathan !arhana M Roll no "#$#%
&hird 'ear ()"$*"+
-DE. Sr no ""
Particulars
Introduction
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Reciprocating Air Compressor
Classification of air compressor
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Reciprocating air compressor
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Single Stage Reciprocating Air Compressor
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Multistage Compressor
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Two stages air compressor
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Application of Reciprocating Compressor
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Conclusion
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References
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"" ntroduction
An air compressor is a machine which compresses the air and rise its pressure. The air compressor sucks the air from atmosphere ,compresses it and delivers the same under a high pressure to a storage vessel. From the storage vessel , it ma coned ! the pipeline to a place where the suppl of compressed air is re"uired. Since compression of air re"uire some work to !e done on it, therefore a compressor must !e driven ! some prime mover. Air compressors are used for suppling high#pressure air. There are man uses of high#pressure air in the industr. The main uses of high#pressure $compressed% air are &
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Reciprocating Air Compressor
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to drive compressed air engines $air motors% used in coal mines, to in'ect or spra fuel into the clinder of a (iesel engine $air in'ection (iesel engine%, to operate drills, hammers, air !rakes for locomotives and railwa carnages, water pumps and paint spras, to start large $heav% (iesel engines, to clean workshop machines, generators, automo!ile vehicles, etc., to cool large !uildings and air craft)s, and to supercharge I.C. engines.
&here are mainly t0o types of air compressors vi1 reciprocating air compressors and
rotar air compressors. Reciprocating air compressors are similar to reciprocating engines where a piston reciprocates inside a clinder. In rotar air compressors, air is compressed due to rotation of impeller or !lades inside a casing. The principal parts of a reciprocating air compressor are the same as that for a engine. The reciprocating air compressor ma !e single#acting $air is admitted to one side of the piston onl% or dou!le#acting $air is admitted to each side of the piston alternativel%, and ma !e single#stage or multi#stage. In a multi#stage compressor, the air is compressed in several stages instead of compressing the air full in a single clinder. This is e"uivalent to a num!er of compressors arranged in series. The pressure of air is increased in each stage. Single#stage compressors are used for deliver pressures upto *+ !ar, three#stage compressors for pressure upto ++ !ar and two#stage compressors for pressures in !etween *+ to ++ !ar. The average piston speed of a reciprocating air compressor is limited to a!out -++ to ++ meters per minute to reduce friction wear.
""( 2lassification of air compressor
The air compressors ma !e classified in man was, some of them are as !elow
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3ccording to 0or4ing
a. Reciprocating compressors !. Rotar compressors
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3ccording to action
a. Single acting compressors Government Polytechnic, Miraj.
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Reciprocating Air Compressor !. (ou!le action compressors
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3ccording to number of stages
a. Single stage compressors !. Multi stage compressors
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Depending upon pressure limit
a. /ow 0ressure air compressor $01* M23m % !. Medium 0ressure $*M23m1014M23m % c. 5igh 0ressure $4 M23m 01*+ M23m %
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Depending upon 2apacity
a. /ow Capacit $61 *.7 M-3s% !. Medium Capacit $ *.7M-3s 1 6 1 -M -3s% c. 5igh Capacit $6 8 7 M-3s%
(" Reciprocating air compressor
A reciprocating compressor or piston compressor is a positive#displacement compressor that uses pistons driven ! a crankshaft to deliver gases at high pressure. The intake gas enters the suction manifold, then flows into the compression clinder where it gets compressed ! a piston driven in a reciprocating motion via a crankshaft, and is then discharged. Applications include oil refineries, gas pipelines, chemical plants, natural gas processing plants and refrigeration plants. 9ne specialt application is the !lowing of plastic !ottles made of polethlene terephthalate $0:T%.
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Reciprocating Air Compressor
("" Single Stage Reciprocating 3ir 2ompressor 2onstruction !ig"
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Reciprocating Air Compressor
A single stage reciprocating air compressor consist of *.
Clinder
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0iston
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Connecting rod
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Inlet and discharge valve
7.
:lectric motor
5or4ing
;hen the piston moves downward $ during outward or suction stroke%, the pressure inside the clinder falls !elow the atmospheric pressure. (ue to this pressure difference the inlet valve $I.6.% get opened and the air is suck into the clinder, at inlet pressure until the piston completes the outward stroke. 2ow when the piston moves out upward $or during inward stroke% the pressure inside the clinder goes on increasing till it reaches to discharge pressure at this stage discharge valve get open and the air is delivered to the container. At the end of deliver stroke small "uantit of air, at high pressure, is left in the clearance space. As the piston start its suction stroke, the air contained in the clearance space e
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Reciprocating Air Compressor At this stage, the inlet valve gets opened as a result of which fresh air is sucked into the clinder, and the ccle is repeated.
5or4 done by a Single Stage Reciprocating 3ir 2ompressor:
;e have alread discussed in the a!ove section, the air is first sucked, compressed and then delivered. So there are three different operations of the compressor.
Thus we can see that there is three was to o!tain the workdone as follows&
*. ;ork is done on the piston during the suction of the air. . ;ork is done ! the piston during compression as well as deliver of the air. -. ;ork done ! a reciprocating air compressor is mathematicall e"ual to the work done ! the compressor during suction.
5ere we shall discuss the following two important cases of work done&
*. ;hen there is no clearance volume in the clinder, and . ;hen there is some clearance volume. =
;ork done ! a Single Stage Reciprocating Air Compressor without Clearance 6olume & Consider a single stage reciprocating air compressor without clearance
volume delivering air from one side of the piston onl.
/et
0* > Initial pressure of air $!efore compression%, 6* > Initial volume of air $!efore compression%, T* > Initial temperature of air $!efore compression%, 0, 6, T > Corresponding values for the final conditions $i.e. at the deliver point%, r > 0ressure ratio $i.e. 0 3 0*%.
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Reciprocating Air Compressor
A!ove diagrams shows the 0#6 and T#S of a single acting single stage reciprocating air compressor without clearance volume. ;hen return stroke take place, the air is compressed ! its ma'or part $i.e. compression stroke ?C% at constant temperature. The compression continues till, the pressure $0% in the clinder is sufficient to force open the deliver valve at C. After that no more compression takes place with the inward movement of the piston. 2ow during the remaining part of compressions stroke, the compressed air is delivered till the piston head reaches the clinder end. After that, the air is sucked from the atmosphere during the suction stroke A? at pressure 0 *.
Thus the compression of air ma !e isothermal, poltropic or isentropic@ so we can o!tain the workdone under these compressions&
" 5or4done during isothermal compression:
; > .- m R T * log r n ( 5or4done during polytropic compression 6P7 8 2onstant9:
; > $n3n#*% m R $T B T*% # 5or4done during isentropic compression:
; > m C p $T B T*%
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Reciprocating Air Compressor Po0er Reuired Driving a Single*stage Reciprocating 3ir 2ompressor:
The power re"uired to drive the compressor ma !e o!tained from the usual relation, 0 > $ ; 2w%3+ watts If 2 is the speed of the compressor in r.p.m., then num!er of working strokes per minute,
2w
>2
... $For single acting compressor%
>2
... $For dou!le acting compressor%
(# 3dvantages
*.The construction is simple. . Initial cost is less.
(/ Disadvantages
*.5eav moving component are re"uire to compress the air. . The power re"uirement for compressor is high. -. There might !e some !alancing pro!lem due to heav moving part.
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Reciprocating Air Compressor #" Multistage 2ompressor
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Compression of air from atmospheric or suction pressure to deliver pressure is take place in more than one clinder is called multistaging.
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The clinders are arrange series one after another the air is first compresses in first clinder than this high pressure high temperature air is than passed through second clinder where it again compresses
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To reduce the temperature rise an intercooler is arranged in !etween two clinders
#"" &0o stages air compressor
A schematic arrangement for a two stage reciprocating air compressor with water cooled intercooler is shown in finger.
First of all, the fresh air is sucked from the atmosphere in the low pressure $/.0.% clinder during its suction stroke at intake pressure 0* and temperature T*. The air after compression in the /. 0. clinder $i. e. first stage% from * to , is delivered to the intercooler at pressure 0 and temperature T. 2ow the air is cooled in the intercooler from to - at constant pressure 0 and from temperature T to T-. After that , the air is sucked in the high pressure $5. 0.% clinder during its suction stroke. Finall, the air, after further compression in 5. 0. clinder $ i. e. second stage% from - to is delivered ! compressor at pressure 0- and T.
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Reciprocating Air Compressor
sothermal efficiency $or compressor efficienc% of reciprocating air compressor&
It is the ratio of work or power re"uired to compress the air isothermall to the actual work re"uired to compress the air for the same pressure ratio. Dc > Isothermal work done 3 Indicated work done > E $ .- /og $ 0 3 0* % % 3 $ n 3 n#* % $ 0 3 0* % G $ n#* 3 n % B * H H
7olumetric Efficiency: It is the ratio of the volume of free air deliver per stroke to the
swept volume of the piston. The volumetric efficienc of a reciprocating air compressor is different when it is with or without clearance volume. 6olumetric efficienc with the clearance volume&
;here, Dv > 6olume of free air deliver per stroke 3 Swept 6olume of the piston > *JK#K$0 3 0*%G$*3n%
K > Clearance ratio > 6c 3 6s 6c > Clearance 6olume 6s > Swept volume of the piston 2 > 0oltropic inde<
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Reciprocating Air Compressor #"( nter*cooling of air in a t0o stage reciprocating air compressor " Perfect nter*cooling B ;hen the temperature of the air living the intercooler is e"ual to
the original of atmospheric air temperature, then the inter#cooling is known as perfect inter# cooling
( mperfect inter*cooling
;hen the temperature of the air living the intercooler is more than the original atmospheric air temperature then the inter#cooling is known as imperfect inter#cooling.
#( 3dvantages of Multistage compressor
*. Saving of work input as compared to single stage compressor. . It provide effective lu!rication !ecause of lower temperature range. -. It reduces cost of compressor. . It reduces leakage loss considera!l. 7. reduction in ma
## Disadvantages of multistage compressor
*. The construction is more complicated. . Initial cost is more.
/" 3pplication of Reciprocating 2ompressor
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Reciprocating Air Compressor
*. In auto service station for filling the air in tre and tu!e, also for cleaning the vehicle . 9perating pneumatic tools like rock drill. -. operating pneumatic !rake in vehicle. . In workshop for cleaning the machines. 7. In spra painting shop.
$" 2onclusion
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Reciprocating Air Compressor Thus it is clear that a single stage compressor cannot contri!ute to high deliver pressure demands 5igh compression in single stage reduces volumetric efficienc so overcome this pro!lem multistage compressor are use.
+" RE!ERE-2ES:
*H Thermal :ngineering ! R.S. Kurmi Government Polytechnic, Miraj.
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Reciprocating Air Compressor 5eat :ngineering ! (.S. Kumar -H ;e!site& •
authorstream.com
•
sachinchaturvedi.wordpress.com
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