03 Basic Compressor Types

7/18/2019 03 Basic Compressor Types

1/38

Atlas Copco Mexicana

Fundamentos de Aire Comprimido Parte 2


2/38

Basic Compressor Types


3/38



4/38


Positive Displacement Reciprocating

Rotary Screw

Rotary Lobe

Scroll

Dynamic Radial--Centriugal


5/38

Positive Displacement TypePositive-Displacementunits are those in which

successive volumes of gas

are confined within a

closed space and elevated

to a higher pressure.



6/38


Positive Displacement

Reciprocating compressors Piston units developing pressure

t!roug! t!e action o a piston moving in

a cylinder

"ay be single or double acting

#!en air is compressed rom

atmosp!ere and compressed in a singlestro$e% it is said to be single acting&

Double acting compresses on t!e up

stro$e and down stro$e

"ay be single-stage% two-stage% or

multiple-stage% air or water-cooled&


7/38


Positive Displacement Reciprocating

Single Acting Double Acting


8/38



'il Flooded Rotary Screw

(wo intermes!ing rotors% male andemale perectly matc!ed

"ale generally drives emale rotor 'il is in)ected into t!e compression

c!amber or lubrication% cooling andsealing


9/38



'il Free Rotary Screw

*ntermes!ing rotors wit! timing gears

to prevent rotor contact

+o need or lubrication in t!e

compression c!amber

Lubrication is re,uired or bearings

and timing gears only


10/38

Rotary Screw compression process--traps consecutive quantities of gasbetween the male lobe and female flute. As screw turns, the enclosed volume

decreases, thus increasing the pressure. Compressed air is then pushed out of the

element at the discharge port.



11/38

As the rotors revolve, the airinlet is sealed off The rotary motion produces a

smooth compression, until each

section reaches the beginning of

the outlet port The compressed air then flows

smoothly out of the element



12/38

Airend Design

Optimum tip speeds 20 to 30 msec Oil !n"ected

#$ msec Oil %ree


#$2$


13/38



'il Free Rotary Lobe

(wo intermes!ing lobes wit! timinggears to prevent rotor contact

(!e rig!t sidelet side inta$e and

disc!arge design !elps eliminate

a.ial loads


14/38

Inlet port

Outlet port

Intake air

Compressed air

&uction Air at inlet pressure enters t!e compression c!amber

'utlet ports sealed o by emale rotor

Compression starts *n and outlet ports closed o

/olume is reduced% pressure increases

Delivery Female rotor uncovers outlet ports and compressed air lows out



15/38


Positive Displacement 'il-ree rotary scroll


16/38


Positive Displacement 'perating Principle


17/38

De'initions and %ormulas

Capacity calculations (Positive)Displacement* +olden rule, FAD% ACF"% and *CF" are i.ed volume low rates

w!ic! do not c!ange wit! respect to atmosp!eric conditions& *n

ot!er words% a given compressor% w!en operating at rated speed

and disc!arge pressure will essentially deliver t!e same volume low

rate regardless o inlet conditions&

&C%M deliveryo an air compressor is calculated rom t!e unit0sFAD volume low rate& SCF" delivery will vary% depending on !ow

t!e actual atmosp!eric conditions deviate rom t!e 1standard

reerence set o conditions& *n winter% t!e SCF" delivery o a given

air compressor is greater t!an during t!e summer% and vice versa&


18/38

-''ects on compressor per'ormance

As am.ient temperaturedecreases/ te 1eigt o' air in

a given cu.ic 'oot (density*

increases

As am.ient temperature

increases/ te density o' air

decreases

A positive displacement

compressor 1ill run unloaded

more in te 1inter tan in te

summer/ tere.y consuming

less po1er to produce tesame amount o' air


19/38

Tere can .e a 20 di''erencein compressor output .et1een1inter 4 summer

A compressor must .e si5ed toandle te 1orst caseconditions6tat is summer7

Tis is to ensure tat tecompressor can al1ays supplyenoug air to meet tecustomer8s demands

-''ects on compressor per'ormance


20/38

9AR!AT!O:& !: O;TP;T !MAT!C CO:D!T!O:&

(Positive)Displacement*

!nletTemp

R= %AD AC%M !C%M &C%M >.Min

?$ @0 20 $$ B# 000 B@3B

$0 @0 20 $$ B# B #$330 @0 20 $$ B# 2# ?$2@

:ote, Calculations are .ased on .arometric pressure o' $ psiA

&tandard conditions de'ined as B psiA/ @0 %/ 0 R=

Effects on compressor performance


21/38

our annual po1er .ill 1ill .e .ased upon teaverageintaEe conditions


22/38

Basic Compressor Design

Dynamic PrincipleCentrifugal units arethose in which velocity

(kinetic energy) is

converted into pressure


23/38


Dynamic Centriugal

Are water-cooled% rotary% continuous-low

mac!ines&

#or$ing principle3 Rapidly rotating impellers

accelerates t!e gas as it passes t!roug!&

(!is $inetic energy is t!en transormed into

pressure as t!e air is successully slowed

down4partially in t!e impeller5s6 and

partially in stationary diusers blades&


24/38

Dynamic PrinciplePressure rise grap

&CRO>> 9O>;T-

!MP->>-RD!%%;&-R

!nlet

'lange

!mpeller

eye

!mpeller

rim

Di''user

outlet

Pressure rise

in impeller

Pressure rise

in di''user

&uction

pressure

Discarge

pressure

PR-&&;R-

R!&-



25/38

(!e centriugal compressor c!aracteristic curve(!e centriugal compressor c!aracteristic curve

&urge

&tone1all

%lo1

Pressure

Centrifugal CompressorCentrifugal Compressor

FundamentalsFundamentals


26/38

&;R+-&;R+-BreaEdo1n o' air'lo1 due to ig .acE pressure

(oscillation 'lo1*

&TO:- >&TO:- > (coEe*(coEe*Maximum 'lo1 a compressor can andle

at a given speed




27/38

TurndownTurndowncapacitycapacity




28/38

Controlmodes

/olume low

Pressure

"odulating blow-o

control

or constant pressureapplications

e.cess air is blown o to

atmosp!ere wasting 7!p&




29/38

0

!"

#" $00

$00

"0

15%

102%

! of "oad

100%

Power

82%

Centrifugalconstant pressure control

Positive Displacementload#unload control

P$%&R

S'*+S




30/38

Control modes

Auto dual control

most energy saving control

mode or luctuating air

demands

Pressure

/olume low




31/38

0

!"

#" $00

$00

"0

15%

102%

! of "oad

105%

100%

Power

20%

86%

Centrifugal

auto#dual control

Positive Displacementload#unload control

P$%&R

S'*+S




32/38

!nlet pressure

!nlet air temperature

Cooling 1ater temperature

-''ects on Compressor Per'ormance

Centri'ugal Compressors


33/38

Discharge

Pressure % 100

Power at

Coupling % 100

Inlet flow (weight/volume) percent 100

Decrease in inlet pressure

reduces flow

Decrease in inlet pressure

reduces power required

!nlet pressure!nlet pressure



34/38

Inlet air temperatureInlet air temperatureinfluenceinfluence

Discharge

Pressure %

Power at

Coupling

%

Inlet flow (weight/volume) % 100

Decrease in air temperature

increases flow

Decrease in air temperature

increases power

Increase in air temperature

reduces flow

Increase in air temperature

reduces power

urg

el

ine

Design point

100

100



35/38

Discharge

Pressure % 100

Power at

Coupling % 100

Inlet flow (weight/volume) % 100

Colder water

increases flow

Colder water increases

power requirement

!armer waterdecreases flow

!armer water decreases

power requirement

urg

el

ine

Cooling waterCooling watertemperaturetemperature



36/38

C!anges in Perormance From Summertime Perormance8

!nlet Temp ?$ $0 0

PD'lo1 (sc'm* 00 F2# F2$

po1er 00 F30 F@$

Dyn

'lo1 (sc'm* 00 F3 F322

po1er 00 F0 F2

GBased on multistage 1atercooled compressors

Positive Displacement vs Dynamic



37/38

:uestro compromiso es contri.uir

a me"orar su productividad a travHs

de la interacciIn e innovaciIn


38/38

Documents

03 Basic Compressor Types