200905094-Ppt on Classification of Air Compressors

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What is Compressor?

a device used for pumping...

compressible fluids i.e,air, gas & steam



PRIMEMOVER COMPRESSOR

HEAT REJECTED

HEAT SOURCE

HEAT TO RADIATION AND COOLANT

LOWPRESSURE AIR COMPRESSED AIR



CLASSIFICATION OF

COMPRESSORSCLASSIFICATION:

Compressors are classified in many ways out

of which the common one is theclassification based on the principle of operation.

TYPES OFCOMPRESSORS:

1. PositiveDisplacement

2. Roto-Dynamic Compressors.



Positive displacement compressors

In this type the volume of the cylinder isreduced mechanically to compress the gas.

Roto-dynamic compressors

In this type the centrifugal force or the

velocity of the moving gas is used for

producing compression of gas.



Positive displacement compressorscan be further divided intoReciprocating

and rotary compressors. Under the classification of reciprocating compressors, we have

1. In-line compressors,2. V-shaped compressors,3. TandemPiston compressors.4. Single-acting compressors,

5. Double-acting compressors,6. Diaphragm compressors.



The rotary compressors are divided intoS

crew compressors,

1. Vane type compressors,2. Lobe and scroll compressors

and other types.

Under the Roto-dynamic compressors,we have

1. Centrifugal compressors,2. Axial flow compressors.



The below picture shows the classification of

different types of compressors.



TYPES OF RECIPROCATING COMPRESSORS:

SINGLE-ACTING COMPRESSORS:

Single-stage compressors are generally used for pressures in the

range of 70 psig to 100 psig.

They have piston working on air only in one direction.The other end of the piston is free or open which does not performany work.The air is compressed only on the top part of the piston.T

he bottom of the piston is open to crankcase and not utilized forthe compression of air.



SINGLE ACTING RECIPROCATING COMPRESSOR



DOUBLE-ACTING COMPRESSORS:

Two-stage compressors are generally used forhigher pressures in the range of 100 psig to 250 psig.

They have two sets of intake and deliveryvalves on both sides of the piston.

As the piston moves up and down, both

sides of piston is utilized in compressingthe air.



The intake and delivery valves operatecorresponding to the stroke of thecompressor.

The compressed air delivery iscomparatively continuous when comparedto a single-acting air compressor.

Both sides of the pistons are effectivelyused in compressing the air.



ADVANTAGES

It has flexibility in capacity and pressure range.

Its compression efficiency is higher at compression ratioabove 2.

It is highly adaptability to low speed drive.

It is suitable for low, medium and high pressures and low

and medium gas volumes.

It has high delivery pressure.



DISADVANTAGES

Its operating speed is low.

The air supply is pulsating.

Cyclic vibrations occur.

Has complicated lubrication system.

There is a possibility of contamination of the airsupplied with oil.

The air compressor size is large for a given discharge.



ROTARY AIRCOMPRESSOR:

Air is compressed by two rotating or inter meshing rotors.

According to the type of construction Rotary Compressor

can be further classified as

(a) RotaryScrew Compressor,

(b)R

otaryV

ane Compressor.



(a) ROTARY SCREW COMPRESSOR.

Air is compressed between two rotating screw

and a casing.

The compression takes place by graduallyreducing space between these two parts.



ROTARY SCREW COMPRESSOR



(b)ROTARY VANE COMPRESSOR.

Air is compressed between casing &rotating rotor by the help of movable rotorblade.

This type of Air Compressor can be furtherclassified as SingleStage or DoubleStageRotaryAir Compressor.



ROTARY VANE COMPRESSOR



DYNAMIC TYPE AIR COMPRESSOR:

The DynamicTypeAir Compressors mechanically impart velocityto the air.

This is produced by the Impellers rotating at a high speed, inenclosed casing.

The air is forced into a progressively reduced volume.

The volumetric flow will vary inversely with the differentialpressure across the compressor.



This type of compressor is further classified as

(a) CentrifugalAir Compressor

(b)Axial FlowAir Compressor

(c) Roots Blower Compressor.



(a)CENTRIFUGAL AIR COMPRESSOR.

In a CentrifugalAir Compressor, an Impeller is mounted on a shaftand positioned within housing, consisting of an inlet duct, a volute

and a Diffuser.

The velocity to the air can be imparted by the high speed rotationof Impeller.

The Diffuser surrounds the Impeller and act to convert the Kinetic

energy of air into potential energy at a higher pressure level.



CENTRIFUGAL AIR COMPRESSOR



The centrifugal air compressor isa dynamic compressor which depends on

transfer of energy from a rotating impeller to

the air.

Centrifugal compressors produce high-pressure

discharge by converting angular momentum

imparted by the rotating impeller (dynamic

displacement). In order to do this efficiently,

centrifugal compressors rotate at higher speedsthan the other types of compressors.



ADVANTAGES

Pressure is high about 4.5:1.

Isothermal efficiency is about 80 to 82%.

More flexible during operation.

Part load performance is better.

Low starting torque required.

Delivery pressure is about 400 bar.



(b)AXIAL FLOWAIRCOMPRESSOR.

TheAxial FlowTypeAir Compressor is essentially a largecapacity, high speed machine with characteristics quitedifferent from the centrifugal air compressor.

Each stage consist of two row of blades, one row rotating &the next row of blade is stationery.

The rotor blades impart velocity and pressure to the air as the

motor turns, the velocity being converted to pressure in

stationery blades.



Axial compressors are rotating, airfoilbased compressors in which the working fluid principallyflows parallel to the axis of rotation.

Axial flow compressors produce a continuous flow of

compressed gas, and have the benefits of highefficiencies and large mass flow capacity, particularly inrelation to their cross-section.

Axial compressors are widely used in gas turbines, suchas jet engines, high speed ship engines, and small scale

power stations.



AXIAL FLOW AIR COMPRESSOR



ADVANTAGES

Pressure ratio per stage is 1.2:1.

Isothermal efficiency is about 86 to 88%.

Frontal area is smaller.

More suitable for multistaging.

Delivery pressure is about 20 bar.



(C)ROOTS BLOWERCOMPRESSOR:

This type is generally called as blower.

The discharge air pressure obtained from this type of machineis very low.

The Discharge Pressure of 1 bar can be obtained in Single Stageand pressure of 2. 2 bar is obtained from Double Stage.

T

he discharge pressure achieved by two rotors which haveseparate parallel axis and rotate in opposite directions.

This is the example of Positive Displacement Compressor inRotaryTypeAir Compressor.



ROOTS BLOWER AIR COMPRESSOR



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200905094-Ppt on Classification of Air Compressors