air compressor

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AIR COMPRESSORS

Prepare by :- Shivkumar Panjabi

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Introduction. Types of compressors. Positive displacement compressors. Dynamic compressors. Reciprocating & screw compressors. Centrifugal compressors. Applications of compressors in

industries. Conclusion & references.

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Introduction:

Principles on which compressors work: A compressor is a mechanical device that

increases the pressure of a gas by reducing its volume.

Compressor is a machine which increases the pressure of a fluid by mechanically decreasing its volume (i.e. by compressing it).(The fluid here is generally air since liquids are theoretically incompressible).

George Medhurst of England designed the first motorized air compressor in 1799 and used it in mining.

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Types of compressors:

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Positive displacement compressor

In the positive-displacement type, a given quantity of air or gas is trapped in a compression chamber and the volume it occupies is mechanically reduced, causing a corresponding rise in pressure prior to discharge. At constant speed, the air flow remains essentially constant with variations in discharge pressure.

Ex: Reciprocating compressors, screw compressors, vane compressors & so on.

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Dynamic compressors:

Dynamic compressors impart velocity energy to continuously flowing air or gas by means of impellers rotating at very high speeds. The velocity energy is changed into pressure energy both by the impellers and the discharge volutes or diffusers. In the centrifugal-type dynamic compressors, the shape of the impeller blades determines the relationship between air flow and the pressure (or head) generate.

Ex: centrifugal compressors, axial compressors.

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Reciprocating compressors

Principle of Operation Fig shows single-acting piston actions in the

cylinder of a reciprocating compressor. The piston is driven by a crank shaft via a

connecting rod. At the top of the cylinder are a suction valve

and a discharge valve. A reciprocating compressor usually has two,

three, four, or six cylinders in it.

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Reciprocating Compressor - Working

ME0223 SEM-IV

Applied Thermodynamics & Heat Engines

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Centrifugal compressors

The centrifugal air compressor is a dynamic compressor, which depends on transfer of energy from a rotating impeller to the air. The rotor accomplishes this by changing the momentum and pressure of the air. This momentum is converted to useful pressure by slowing the air down in a stationary diffuser.

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Centrifugal compressors

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AXIAL COMPRESSORS

Axial flow compressors are designed for high volume, high efficiency and high reliability applications.

Typical applications of Axial Compressors are air separation, sewage treatment, wind tunnel, FCC air blowers, Blast furnaces etc.

Now a days commonly used in Aeroplanes.

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Continued . . . .

Axial compressors have flow in the axial direction by accelerating air tangentially with blades attached to the rotors.

The Axial Compressor is composed of several rows of airfoil cascades.

Static rows are called Stators and rows which rotates are called Rotors.

Rotors

Stators

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Rotary vane compressors

Rotary vane compressors consist of a rotor with a number of blades inserted in radial slots in the rotor. The rotor is mounted offset in a larger housing that is either circular or a more complex shape. As the rotor turns, blades slide in and out of the slots keeping contact with the outer wall of the housing. Thus, a series of decreasing volumes is created by the rotating blades.

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Vane Compressor

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Lobe compressors

Lobe compressors are used in water treatment for backwashing of filter beds.

Effluent treatment for diffused aeration & agitation of effluents.

Aquaculture: For maintaining dissolved oxygen levels.

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Advantages of scroll compressor & applications

These devices are known for operating more smoothly, quietly, and reliably than conventional compressors .

The absence of pistons for gas compression enables scroll compressors to reach 100% volumetric efficiency, leading to reduced energy costs.

Their weight and footprint are considerably smaller compared to other bulkier types of compressors.

scroll compressors have been used food and fruit refrigeration, truck transportation, marine containers air-conditioning applications.

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