Twin Lobe Compressor

8/18/2019 Twin Lobe Compressor

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INSTRUCTION MANUAL

FOR

TWIN LOBE COMPRESSOR

TEST RIG

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INTRODUCTON:

Compressed air is a source of storing mechanical energy. It is a reversible

procedure where work can be returned with small loss of energy in the form of

heat. A compressor is machine which takes air from atmosphere, compressor it

with aid of some mechanical energy & delivers it to storage vessel. The pressure of

air is increased by reducing volume compressed air then can be taken by pipe

wherever it is required.

APPLICATION:

a. In blast furnace, boiler furnace.

b. neumatic tools spray painting, sand blasting.

c. neumatic conveying of cement & grains.

d. In construction of large pro!ects, highway & tunnels.

e. "upercharging in IC #ngines & gas turbines.

f. neumatic brakes & clutches.

g. In air conditioning drying & ventilators

CLASSIFICATION:

A. RECIPROCATING TYPE:

In this type, successive volumes of air or gas are confirmed within closed space

where pressure is increased by reducing the volume characteri$ed for volumetric

capacity & large delivery pressure. %or larger pressure ratio, the compression is

carried out in multistaging with intercooler so that the compression process can be

made near to isothermal so as to minimi$e the work to supplied.

B. ROTATING TYPE:

In this type, air is trapped in the space formed by two manually emerging

surface.ue to which the volume in between surfaces reduces & ressure

increases.The rotary type compressor are characteri$ed by large volumetric

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capacity & relative low pressure .They are high running compressor. '((T",

)*(+#'", "*II-, C#T'I%-A* & A/IA* %*(+ C(0'#""('" are

rotary compressor.

WORKING OF TWIN LOBE COMPRESSOR:

%igure 12a3 shows Twin lobe compressor. There are two rotors, each having two

lobes, one rotor sets the drive from the motor & the other rotor is driven by the first

by gears e4ternal to the casing. The lobes rotor in opposite direction pressuri$ing

the gas .The lobes have well designed cyclical profiles to give perfect meshing &

leak proof seating between the high pressure space & the low pressure space at all

regular positions. A slight clearance between the meeting lobes avoids wear at

sealing surface.

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THEORY:

A volume 5s of the gas at the suction pressure p1 is trapped between the left hand

rotor & the casing, of shown in figure. This trapped volume of the gas does not

change its stage until this space is opened to the high pressure side. Instantly, some

high pressure gas from the receiver rushes back & mi4es irreversibly with the gas

in the blower until the pressure is equali$ed. The gas is then displaced in to the

receiver.

%igure 12b3 shows p6v diagram for roots blower. The flow gas in to the receiver is

not continuous despite the rotors at uniform speed.

+ork required to drive7 ∫1

2

Vap KJ /Cycle

There are 8 cycles per revolution in a Twin lobe compressor

+ork required to drive,

+9 85s 2p:6p13 ; n min

94Vs( p2− p1)×n

60 min.

8vs is the volume of air delivered per revolution.

As the ideal compression process is isentropic, work required for isentropic

compression is,

+i 9γ

γ −1 ; p1×4 Vsn

60 ;( p2 p1 )¿

¿¿

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'oots #fficiency 9 Isentropic work required

ActualWork required

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B. 'otary ositive displacement compressors are engineered & manufactured by

capable & e4perienced personnel in a modem plant with the latest imported &

.0.T 0achines & also with latest toolings. roduction is controlled by close

Inspection, tests & attention to the smallest detail. 'eliable field service is

maintained by factory trained personnel. Compressor range in capacity up to

D,DDD 0@>hr. Eou are invited to request information on si$es not covered in this

bulletin.

'otary ositive displacement has two figures eight impellers rotating in opposite

direction. As each lobe of an impeller passes the compressor inlet, it traps a quality

of air equal to e4actly one6fourth the displacement of the compressor. This

entrapment occurs four times per revolution, moving the entrained air around the

case to the compressor outlet -round helical timing gears accurately position the

impellers in relation to each other, maintaining the minute clearances so vital to the

high volumetric efficiency of the rotary positive compressor. )ecause the

compressor operates with very close internal tolerances, a slight amount of air

escapes past the opening clearances back to the suction side of the compressor.

This leakage, defined as FslipF is predictable constant volume for any given

compressor at any given pressure. %or ease in calculation, this leakage is e4pressed

in compressor rpm. A standard slip, based on handling air at standard condition,

has been established for each compressor si$e. %or gases having a specific gravity

other than

1.D the slip will vary & this must be taken into consideration when calculating total

operating speed unit. Compressor is built with the closest possible tolerances to

give highest volumetric efficiency.

7. SPECIAL FEATURES OF ROTARY POSITIVE DISPLACEMENT

COMPRESSOR.

a. 0anufactured on imported machines with latest technology.

b. All rotating parts dynamically balanced.

c. Computeri$ed profile of the Impeller for higher efficiency.

d. elical ground gears for silent operation & longer compressor life.

e. eavy6duty roller bearing ensure :8 hour continuous trouble free operation.

f. Tested as per )ritish "tandard 1G1 art6II

g. 5ery low maintenance cost.

h.1DDH oil free air.

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8. CASING: ewly designed one piece style, including e4tra deep rib section for greater

rigidity under vaccum or pressure since. #very casing is hydraulically tested. In many

of internal inspection & clearance checks

IMPELLERS:

Are accurately machined for close tolerance operation, dynamically balanced for

smooth running & lower bearing loads. I.". -rade : is used in standard model however,

in higher speeds of compressors, forged>"o -. Iron material is used with integral shaft

arrangement.

TIMING GEARS:

Alloy steel, eat Treated, elical -round cut for greater strength & quieter

operation. elical -ears %itted with ad!ustable hub 2called locking device3 are mounted on

shaft for easy timing setting & easy in dismantling. o hydraulic !ack or any ammering

required ensuring longer life for )earings.

STEELSHAFT;

Are carefully machined & ground from Chrome Alloy "teel. The ground shafts are

fitted in impellers through interference fit which eliminates torsional deflections & permits

increased ratings & -reater efficiency.

BEARINGS:

Are eavy duty 'oller "pherical, double row, for ma4imum loading )earings are

held in machined bearing cartridges -ear & )earings are fi4ed a4ially against shaft

shoulder to control thrust loads & maintain end clearances.

LUBRICATION:

The basic units in the seriesF features trouble free splash lubrication of a Timing

-ears, -enerous si$e sumps are located in the -ear Case. The oil is poured in the gear

case & high temperature grease is poured in driver & driven cover. To prevent undedutcted

losses of lubricant, the series has been designed with visual indicator at oil end cover.

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SPECIFICATIONS:

The technical specifications of the test rig are as follows7

Comp!""o U#$%:

0odel T 6 8:

%abrication umber ::D1BJ

0anufacturing Eear7 :DDD

Tested on 18>D>:DDD.

%ree Air elivery :8.JJ m3/hr

+orking ressure D6@DDD mm of +C

'0 188D

MOTOR:

ower

'0 188D

5olts 88D5, @ , D $,

Type T#%C

COMPRESSOR TEST RIG:

The TestF 'ig Consists of Air Compressor with air suction tank, is fitted with an

orifice to determine the volume flow rate at the inlet side & pitot tube at outlet side

to measure pressure of compressed air. The e4it side of the compressor is

connected to reservoir. #nergy meter is used to record the power input to motor &

in turn the work required for compression. The control panel houses starter for

motor, main switch, Temperature Indicator.

PRECAUTIONS:

1. The reservoir cum air tank should be emptied before stating the compressor.

:. (rifice should not be blocked otherwise rubber sheet of Air tank will cut

drastically.

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A$m: To etermine 'oots #fficiency

APPARATUS:

"top +atch, Tachometer.

SPECIFICATIONS

0a4 elivery ressure @DDD mm of +C

ia. of (rifice 8D mm.

Coefficient discharge 2cd3 of surface D.B:

PROCEDURE:

1. ote down barometric pressure in mm of g & room temperature in Kc.

:. "tart the compressor.

@. After reaching stable pressure note down manometer reading in mm of water to

obtain intake air pressure.

8. ote down the pressure gauge manometer reading in mm of g to determine

outlet air pressure

. ote the time in sec required for 1D revolutions of energy meter.

G. 'epeat the same procedure @ 6 G for other desired pressure

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OBSERVATION TABLE:

S.

No

D!&$'!(

p!"")!

M*#om!%!

R!*+$#,

-mm

Comp!""o

"p!!+ /001

I#&!% A$

T!mp

-23

I#&!% A$

P!"")!

-B*

T$m! % -"!3

4o /1 R!' o4

E#!,( m!%!

H!*+ H* $#

m!%". o4

*$1.

:.

@.

8.

.

B.

G.

L.

J.

1D.

WORK RE5UIRED FOR ISENTROPIC COMPRESSION.

+i 9γ

γ −1 ; p1×4 Vsn

60 ;( p2 p1 )¿

¿¿

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g9 J.L1 m>sec:

a9 #quivalent manometer head of air in meters.

a is calculated as7

Mw w9Ma a

Mw9 ensity of water

w90anometer head of water in mtrs.

Ma 9 ensity of air

Ma is calculated by using relation7

a5a 9 m'Ta

Ma 9 Pa

Ra

ressure from height of mercury is calculated as

9 mMmg

Mm 9 ensity of mercury

m 9 )arometer height of mercury in m

' 9 Characteristic air constant

Ta 9 Temperature of intake air Kk

The atmospheric pressure is calculated as

a90.760×13600×9.81

103

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ensity of air is now given as

9 Ra

Pa 9101.4×103

287×297 9 1.1LJB m@

The eight of Air is given as

a 9 !wHw

!a

910×123×10−3

1.1896

C*&3)&*%$o#:

* A3%)*& 6o o4 3omp!""$o#

+a95 2:613

+here,

595olume of air handled in cubic m>sec.

19 Atmospheric pressure in bar.

: 9 ischarge pressure in bar.

I"!#%op$3 6o o4 3omp!""$o#

+i 9

γ

γ −1 ;

p1×V

;

( p2 p1 )¿¿¿

61? "

3 Roo%" E44$3$!#3( 9 Isentropic work required

ActualWork required

+a9

4Vs×n

60 ; 2:613

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94×0.0672×1404

60 ; 21.@613

9 1.LL

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Twin Lobe Compressor