Air compressor

Prepare by :-
Shivkumar Panjabi 1
Prepare by :- Shivkumar Panjabi

 Introduction.
 Types of compressors.
 Positive displacement compressors.
 Dynamic compressors.
 Reciprocating & screw compressors.
 Centrifugal compressors.
 Applications of compressors in industries.
 Conclusion & references.
Prepare by :- Shivkumar Panjabi 2

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.

 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.

 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.

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.

Reciprocating Compressor - Working
ME0223 SEM-IV Applied Thermodynamics & Heat EnginesPrepare by :- Shivkumar Panjabi 8

 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.

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.

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

 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.

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.

 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.

Air compressor

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