Engineer_ Full Information About Centrifugal Compressor

8/6/2019 Engineer_ Full Information About Centrifugal Compressor

http://slidepdf.com/reader/full/engineer-full-information-about-centrifugal-compressor 1/9

Home About Production Airplanes Power Simple Search ...

Full Information about Centrifugal

Compressor power

Most cooling systems, from residential air conditioners to large commercial and industrial chillers,

employ the refrigeration process known as the vapor compression cycle. At the heart of the vapor

compression cycle is the mechanical compressor. A compressor has two main functions: 1) to pump

refrigerant through the cooling system and 2) to compress gaseous refrigerant in the system so that it

can be condensed to liquid and absorb heat from the air or water that is being cooled or chilled .

There are many ways to compress a gas. As such, many different types of compressors have been

invented over the years. Each type utilizes a specific and sometimes downright ingenious method to

pressurize refrigerant vapor. The five types of compressors used in vapor compression sys tems are

Reciprocating, Rotary, Centrifugal, Screw and Scroll.

We can classify compression process into to types :

(a) Compression by decreasing volume:-

Required pressure is developed by trapping a gas in a chamber, reducing the volume of the chamber

and increasing the pressure of the gas by the ratio of initial chamber to the final volume.

(b) Compression by accelerating fluid :-

The second method of compressing gases is based on the conversion of kinetic energy into the

potential energy. Accelerating fluid to a higher velocity and then decelerating it by changing its

direction of flow transforms the accumulated energy into potential energy

We are going to talk about Centrifugal Compressor

Popular Posts

Airplane control surfaces

For an airplane to be controllable,

control surfaces are necessary. The

4 main surfaces are ailerons ,

elevator , rudder and flaps...

Introduction of Areodynamics ( Bernoulli’s Principle

)

Daniel Bernoulli (1700-1782) was a Swiss scientist

who studied fluid flows. From his work emerged

“Bernoulli’s Principle.” This law sta...

METAL CASTING ( PATTERN )

A pattern is a shaped form of wood or metal around

which sand is packed in the mold. When the

pattern is removed the resulting cavity is t...

Full Information about Centrifugal Compressor

Ads by Google Compr es sor Natur al Gas Gas Tur bine Flow Gas Shaf t Seal

Like 54 people like this. Be t he first of your friends.

5/23/2011 ZE-ENGINEER: Full Information about …

…blogspot.com/…/full-information-abo… 1



Centrifugal Compressors

Centrifugal compressors use the rotating

action of an impeller wheel to exert

centrifugal force on refrigerant inside a round

chamber (volute). Refrigerant is sucked into

the impeller wheel through a large circular

intake and flows between the impellers. The

impellers force the refrigerant outward,

exerting centrifugal force on the refrigerant.

The refrigerant is pressurized as it is forced

against the sides of the volute. Centrifugal

compressors are well suited to compressing

large volumes of refrigerant to relatively low

pressures. The compressive force generated

by an impeller wheel is small, so chillers that use centrifugal compressors usually employ more than

one impeller wheel, arranged in series. Centrifugal compressors are desirable for their simple design and

few moving parts.

Centrifugal compressor works on the principle

of accelerating a gas to a high velocity and

converting its KINETIC ENERGY (velocity) into

POTENTIAL ENERGY (pressure) by decelerating

the gas. The gas enters the eye of the impeller

and is accelerated to the outward edge of the

impeller as it rotates. It then enters a diffuser

where its direction is changed, causing

deceleration. This deceleration converts the KE

into the PE, pressure. If the gas is to be further

compressed, then a return chamber directs it from

the diffuser to the eye of the next impeller in

series. The gas enters a collector or volute when it is to leave the compression stage. It is discharged

to the process through a discharge nozzle.

§ The centrifugal compressor has no connecting rods, pistons and valves; so the shaft bearings are the

only points subject to wear. The compressor discharge pressure is a function of gas density, impeller

diameter and design, and impeller speed. Centrifugal compressor impellers rotate very rapidly:

Low speed 3,600 RPM

Medium speed 9,000 RPM

High speed above 9,000 RPM

Power is supplied by an electric motor or steam turbine. Vapor enters the on the center of impeller

around the shaft and is directed through the impeller blades. As the impeller accelerate the gas, by the

kinetic energy of the impeller is converted to the kinetic of fast moving gas. As the gas enter the volute,

it is compressed, and the kinetic energy is converted to the potential energy of compressed gas. The

velocity of the gas leaving the impeller is extremely high.

Most cooling systems, from residential air

conditioners to large commercial and industrial

chillers, employ the refrigeration process know...

Aluminium Alloy and aircraft

Aluminium Alloy There are many kinds of Alloys to

choose from but often, Aluminium is chosen as it

is lightweight (about ...

Ski board for 2010 Vancouver Winter Olympics .

The 2010 Vancouver Winter Olympics Are Coming!SO we’re going to talk about Ski boards . A high

performance ski base material is made ...

Sand casting

Expendable mold casting is a generic

classification that includes sand, plastic, s hell,

plaster, and investment (lost-wax technique)

moldi...

THE MOST BEAUTIFUL CARS IN THE WORLD .

Alfa Romeo 8C Spider MSRP: $301,600 The 4.7-

liter, V8 engine gets 444 horsepower and 354

pound-feet of torque. Each angle on the front an...

Most Common Steel Types of Tools

Steel is a ferrous metal . Ferrous metals include

steel and cast iron . Most of the tools are made

from one of seven different types ...

New Ion Engine Could Reach Mars

In 39 Days

Recently, as the world celebrated

the first lunar landing, Apollo 11

astronauts Buzz Aldrin and Michael Collins both

called for NASA to ...

Archive

► 2011 (9)

▼ 2010 (18)

▼ December (2)

Full Information about Centrifugal Compressor

Casification of the compressors

► October (1)

► August (3)

► July (7)

► June (2)

► February (3)

► 2009 (10)

ZE-engineer on Facebook

Like





In order to pass from the low pressure in impeller to the higher pressure of the diffuser, the refrigerant

necessarily needs high velocity In absence of sufficient velocity, the refrigerant will stuck in the impeller

and the compressor will stall (surge) .

Therefore one of the fundamental parameter of centrifugal compressor design is the “tip speed ‘

Which must be in the range of 240 to 231 m/sec. This parameter

determines the speed and the

dimension of the impeller:

RPM=[TipSpeed(m/s)*1910]/

Diameter(cm.)

A centrifugal compressor must

be specifically designed for

the right pressure difference

we want to achieve.

Part load conditions are the most critical for centrifugal compressors

Gas speed is even more critical in unloaded condition, when the gas flow decreases and therefore could

not be able to overpass differential pressure to the diffuser. If this happens, the flow can go back into the

impeller bringing compressor to stall .

One of the most innovative technologies which allows to keep sufficient gas speed also in strongly

unloaded conditions and extends unit working range, is the movable impeller discharge technology.

Tags

airplanes (9)

news (12)

power (8)

Production (14)

simple (7)

About Me

Kareem

Roshdy

View my

complete

profile

Mohamed A hmed Sumit MȜtaz

Mohamed Ry an A mr PowerA nd

54 people like ZE-engineer.

Fa cebook social plugin





Based on the type of casing design,centrifugal compressors are classified into two types:

1) Horizontally split casing design(MCL/MCH type):- This design is used for low working pressure

below 40ata.These casings are in two halves with horizontal parting plane.DMCL Compressor have two

stages of compression in parallel in a single casing.The solution is most balanced.The other aspects of

construction are the same as for the MCL Compressor.

2) Verically Split Casing design (BCL/BCH type):-This design is made of barrel construction closedon the sides by end covers with help of studs.This type of construction is suitable for high pressure

operations up to 750kg/cm2. Another type of compressor is the PCL(Pipeline compressor),which has

casing in the form of a cup with a single closing flange in the vertical plane instead of two as with the

BCL.

Example of Designation of BCL

Compressor :

Example : 2 BCL 40 7

/ b

2 BCL 40 7 / b





Compressor Components

§ Casing

§ Counter Casing (If Applicable)

§ Diaphragm

§ End Cover (If Applicable)

§ Shaft

§ Impellers

§ Shaft Seals

§ Journal Bearing

§ Thrust Bearing

§ Coupling

COMPONENETS OF BCL COMPRESSOR

Construction of centrifugal compressor:

§ Every centrifugal compressor consist of two parts:- An impeller which forces the gas into the rotary

motion by the action of blades, and the casing which directs the gas to the eye of the impeller and then

leads it away from the impeller perimeter at a higher pressure. For most multistage compressors, shaft

end seals are located inboard of the bearings. The internal passages are formed by a set of diaphragms.

BARREL PULLING ARRANGEMENT

Rotor Assembly





Assembly of Diaphragms in Counter Casing

Assembly of Journal Bearing





BALANCING DRUM

There exists some amount of thrust generated at each impeller because of the differential pressure

prevailing across it. The cumulative thrust generated across all the impellers is huge and it needs to be

supported by the thrust bearing. The thrust bearing size becomes huge if all the gas thrust has to act on

the bearing. For this purpose a rotating element called “Balancing Drum” is incorporated on the rotor.

The drum is acted upon by a pressure differential which pushes the rotor in a direction opposite to that

of the gas thrust. The thrust so generated balances the thrust produced by the impellers. Amount of

balancing depends upon the size of the drum and pressure differential created across it. The pressure

differentiated is maintained by an efficient seal placed over the balancing drum.

Cross-section of a BCL Compressor





ShareThis

0 :التعليقات

Post a Comment

62





Create

Newer Post Older Post

Comment as: Select profile...

Post Comment Preview

هذه الرسالة روابط

Home

Copyright © 2010 ZE-ENGINEER Designed by Blog and Web and Blogger Templates

Subscribe in a reader

Followers

w ith Google Friend Connect

Followers (3)

Already a member? Sign in

Follow

ZE-ENGINEER

Rate My Blog

--

Free RSS Feeds Directory DreamHost Codes

Share


blogspot com/ /full-information-abo 9

Documents

Engineer_ Full Information About Centrifugal Compressor