compressor & seals

8/18/2019 Compressor & Seals

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General arrangement of a compressor s

Compressor The function of a compressor is to take a definite quantity of fluid (usually gas, and mo

often air) and deliver it at a required pressure.

An air compressor takes in atmospheric air compresses it and delivers the high-pressure a

to a storage vessel from which it may be conveyed by the pipeline to wherever the supply o

compressed air is required.

ompressor must be driven by some form of prime mover.CLASSIFICATION OF AIR COMPRESSORS

!. "eciprocating compressors #. "otary compressors.

$ingle-stage, or multi-stage.

$ingle-acting and double-acting

%lowers and superchargers are essentially air compressor

RECIPROCATING COMPRESSORS

onsists of a piston which reciprocates in a cylinder, driven through a connecting rod an

crank mounted in a crankcase.

There are inlet and delivery valves mounted in the head of the cylinder - pressure differenti

type - operate as the result of the difference of pressures across the valve.

&-' diagram for a single-stage reciprocating air compressor

Multistage reciprocating compressors

ultistage compression is a series arrangement of cylinders

in which compressed air from the cylinder before, becomesthe intake air for the cylinder, which follows.


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Singlee!e" Impeller #ou$le e!e" impeller

ROTAR% COMPRESSORS

achines which develop pressure and have a rotor as their primary element.

henever large quantities of air or gas are required at relatively low-pressure.

Classifications

!. *isplacement (positive) compressors

(i) "oots blower (ii) $liding vane compressor (iii) $crew compressor.

#. $teady-flow (or +on-positive displacement) compressors

(i) entrifugal (or radial) compressor (ii) Aial flow compressor.

Displacement Compressors

ompressors in which air is compressed by being trapped in the reduced space formed b

two sets of engaging surfaces.

Roots Blower

ne of the rotors is connected

to the drive and the second rotor

is gear driven from the first.

Vane Type Blower

onsists of a rotor mounted eccentrically.

The rotor is slotted to take the blades, which are of a non-metallicmaterial, usually fiber or carbon.

As each blade moves past the inlet passage, compression begins due to decreasing volum

between the rotor and casing.

*elivery begins with the arrival of each blade at the delivery passage.

Steady-flow Compressors

ompression occurs by transfer of kinetic energy from a rotor.

The centrifugal type of compressor was used in the earliest gas turbine units for aircraft.

or low-pressure ratios (no greater than about /0 !) the centrifugal compressor

or higher pressure ratios the aial flow compressor is more efficient or industrial and large marine gas turbine plants aial flow compressors are used.

or aircraft higher-pressure ratios, aial flow compressors are used.

The centrifugal compressors are used in0

(i) $uperchargers (ii) Turbo-prop.

entrifugal compressors are preferred where simplicity, light weight, ruggedness are mo

important than maimum efficiency and smaller diameter.

Centrifugal Compressor

!. urved radial vanes

#. 1mpeller - impeller may be single-eyed or double sided.2. asing.

/. *iffuser.

Centrifugal compressor


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Axial Flow Compressor

The flow proceeds throughout the compressor in a direction parallel to the ais of th

machine.

onsists of ad3acent rows of rotor (moving) blades and stator (fied) blades. The rotor blade

are mounted on the rotating drum and stator blades are fied to the casing stator.

ne stage of the machine comprises a row of rotor blades followed by a row of stator blades

The 4fied blades4 serve the following two purposes (i) onvert a part of the 5.6. of the fluid into pressure energy.

(ii) 7uide and redirect the fluid flow so that entry to the net stage is without shock.

Pre&ention of lea's Seals A seal is a device, which helps 3oin systems or mechanisms together by preventing leakag

(e.g., in a plumbing system), containing pressure.

Types of Seal

A"(esi&e) sealant

A sealant is a viscous material that changes state to become solid, once applied, and is used

prevent the penetration of air, gas, noise, dust, fire, smoke or liquid from one locatiothrough a barrier into another.

$ealants are used to close small openings that are difficult to shut with other materials

Gas'et

A gasket is a mechanical seal that fills the space between two ob3ects, generally to preven

leakage between the two ob3ects while under compression.

7askets are commonly produced by cutting from sheet materials, such as gasket pape

rubber, silicone, metal, cork, felt, neoprene, fiberglass, or a plastic polymer.

7askets for specific applications may contain asbestos.

O-ring An o-ring is a mechanical gasket in the shape of a torus8 it is a loop

of elastomer with a disc-shaped cross-section, designed to be

seated in a groove and compressed during assembly between two

or more parts, creating a seal at the interface.

O-ring $oss seal

A technique for 3oining two fluid-carrying pipes, hoses or tubing.

1n an o-ring boss system, a male threaded part is inserted

into a female threaded part, providing a mechanical seal.


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Piston ring

An open-ended ring that fits into a groove on the outer diameter of a piston in a reciprocatin

engine - internal combustion engine. ain function is to $eal the combustion chamber.

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