Lect No 05

1. Unit No:02
Energy Conversion Devices
Prof. Yash B. Parikh
M.Tech (Computer Integrated Manufacturing)
B.E.(Mechanical Engineering)
Assistant Professor
Department of Mechanical Engineering

2. Air Compressors
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3. Air Compressors
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 A compressor is a machine capable of compressing
and delivering the air at desires pressure.
 It is driven by a prime mover (Engine or an electric
motor).
 A compressor takes in atmospheric air,
compresses it and delivers the high pressure air
to a receiver(storage vessel) from which it may be
conveyed by a pipeline.

4. Applications of Compressed Air
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• For operating pneumatic hand tools such as drills.
• Painting and Spraying.
• For driving mining tools.
• To supply the air in blast furnace.
• To operate air brakes in automobiles.
• To inflate automobile tiers.
• To clean machines and work shop floor.

5. Applications of Compressed Air
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• Refrigerators and Air conditioners.
• Gas turbine power plants.
• Conveying materials like sand and concrete along a
pipe.
• Driving Air Motors.

6. Classification of Air Compressors
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7. Positive Displacement Type of Air Compressors
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 Reciprocating Compressors :
In industry, these are the most widely used.
• They work on the principles of a
bicycle pump.

8. Reciprocating Compressors
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9. Reciprocating Compressors
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• It has a piston sliding in a cylinder similar to
I.C.Engines.
• The air is compressed due to positive displacement.
• They can produce large pressure ratios with low
volume flow rate.
• They are of two types :
i) Single Acting Reciprocating Compressor
ii) Multistage Compressor

10. Single Stage v/s Multistage Compressors
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• A compressor is considered to be single stage when
the entire compression is accomplished with a single
cylinder.
• The compression of air in single stage has many
disadvantages and its use is limited where low
delivery pressure is required.
• Advantages of multistage compression is that it
provides a facility to install an inter cooler between
the stages.

11. Single Stage v/s Multistage Compressors
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• Less power is required to deliver the same quantity
of air at the same delivery pressure.
• Better lubrication due to lower temperature.
• Multistage are used for high pressures and have
lower discharge temperature (140 to 160 C)
compared to single stage (205 to 240 C)
• A multistage compression is more efficient and
mostly employed for high pressures.

12. Single Acting Reciprocating Air Compressors
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13. Rotary Compressors
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14. Rotary Compressors
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• Rotary compressors have rotors in place of pistons
and gives a continuous pulsation free discharge.
• They operate at high speed and generally provide
higher throughput than reciprocating compressors.
• Their capital costs are low, they are compact in size,
have low weight, and are easy to maintain.
• For this reason they have gained popularity with
industry.

15. Dynamic Compressors
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• In this type of compressor the air is not trapped
within the specified boundaries, but it flows at a
steady rate continuously.
Centrifugal Compressor :

16. Centrifugal Compressor
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• The centrifugal air compressor is a dynamic
compressor.
• It consists of an impeller which rotates at a very high
speed (as high as 30,000 rpm).
• Which produces centrifugal head on the air within
and causes the air to flow from surroundings axially.
• Due to transfer of energy from a rotating impeller to
the air get compressed.

17. Centrifugal Compressor
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• Centrifugal compressors are most frequently used for
medium volume and medium pressure air delivery.
• One advantage of a centrifugal pump is the smooth
discharge of the compressed air.
• The centrifugal force is utilized by the centrifugal
compressor.
• The air particles enter the eye of the impeller,
designated D.
• As the impeller rotates, air is thrown against the
casing of the compressor.

18. Centrifugal Compressor
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• The air becomes compressed as more and more air is
thrown out to the casing by the impeller blades.
• The air is pushed along the path designated A, B,
and C in Figure.
• The pressure of the air is increased as it is pushed
along this path.
• Centrifugal compressors can use a variety of blade
orientation including both forward and backward
curves as well as other designs.
• There may be several stages to a centrifugal air
compressor, and the result would be the same; a
higher pressure would be produced.