This document discusses air compressors and their classification. It covers topics like the introduction to compressors, their uses, types of reciprocating and rotary compressors, their operation, advantages of multi-stage compressors, and a comparison between reciprocating and rotodynamic compressors. Reciprocating compressors can achieve higher pressures than rotodynamic compressors but are more complex and have higher costs. Multi-stage compressors improve efficiency over single-stage designs.

1. Elements of Mechanical Engineering
Air Compressors
Created by,
Devang Pandit(130110120025)
Yash Pandya(130110120026)
Akash Pansuriya(130110120027)
Tanuj Parikh(130110120028)

2. Topics To be Covered
• Introduction
• Uses if Compressed air
• Reciprocating compressors
• Operation of a compressor
• Work for compression
• Power required
• Reciprocating compressor efficiencies
• Multistage reciprocating compressors
• Rotary Compressors
• Comparison between reciprocating and rotodynamic
Compressors

3. Introduction
• The machine which takes in Air or any other
gas at lower pressure and compresses it to
high pressure are called compressors
• Compressors are power Consuming machine
• They are also considered as reversed heat
engine
• A compressor is used for increasing the
pressure of air is called air compressor

4. Classification of Compressors
Compressors are Classified According to:
(1) Method of Compression:
(a)reciprocating Compressors:
--Compressies air by Reciprocating Action of
piston inside a cylinder.
--Suitable for producing high pressure
(b) Rotary Compressors: Air is compress due to
rotation of impeller or blade inside a casing
similar to a rotary pump

5. (c)centrifugal compressor:
--Compression of air to desired pressure is
cariied out by centrifugal force
--suitable for medium pressure

6. (2)Delivery Pressure:
(a) Low Pressure-up to 1.1 bar
(b)medium pressure-1.1 to 8 bar
(c)High pressure-8 to 10 bar
(d)very high pressure-above 10 bar

7. (3) Principle Of operation
(a)Positive displacement:Pressure of air is increased
by reducing volume.
--These are capable to produce high pressure with
low volume flow rate
(b) Rotodynamic or steady flow Compressor :
Compreeson of air cariied out by roteting
element imparting velocity to the flowing air and
developed desired pressure.

8. (4) The number of Stages:
--Single stage – pressure upto 5 bar
--Multistage –pressure above 5 bar
(5) The number of cylinder:
--Single cylinder -- Multicylinder
(6)The pressure Limit
--Fans – pressure ration upto 1 to 1.1
--blowers- pressure ratio 1.1 to 2.5
--Compressors – pressure ratio above 2.5

9. (7) Volume Of air delivered
-(a) Low capacity- Volume flow rate up to
10m3/min
(b)Medium Capacity – Volume flow rate
10m3/min to 300m3/min
(c) high Capacity – Volume flow rate above
300m3/min

10. Uses of Compressed Air
• In refrigeration Cycle
• Operating Pneumatic tools like drill , hammers ,
rivetting machine etc
• Filling the air in automobile tyres
• Spray painting
• Increasing inlet pressure of I.C engine
• To operate air moter in mines where fire risks are more
• Pumping of water
• Gas turbine plant
• For sand blasting
• Operating blast furnaces

11. Reciprocating Compressors
It is widely used forCompressing
Air and satisfactory for all
ranges of pressure
Consist of the cylinder in which
a piston reciprocates
The piston Is driven by Rod
The crank is monted in a
crankcase

12. Operation Of a compressor
• (1) Operation without clearance:

13. Operation Of a Compressor
(2) Operation with Clearance:
1-2 Compression
process
2-3 delivery
process
3-4 Expansion
process
4-1 Suction
process

14. Multistage Reciprocating Compressure
• There are several disadvantages to compress
the air at a high pressure in a single cylinder.
• In single stage Compresseor If the ration of
pressure increase the volumatic efficiency
decrease

15. **The Following problem With single Stage
Compression:
--The higher the delivery pressure, the higher
will be delivery temperature
--the increase in temperature of air causes
reduction in density of air ,hence the mass
flow through compressor decreases
--The operation at high pressure and
temperature will need heavy working parts

16. ``
In low pressure cylinder air s compressed adiabatically from 1 to 2
The Compressed air is passed through intercooler-1 wher it is cooled
down from 2-2’

17. • The air is compressed adiabaticlly from 2-3’
• The Compressed air is cooled down from 3-3’
• Finally air enters into high pressure cylinder
for getting higher pressure

18. **Advantages OF Multistage compressor**
--Volumetric efficiency is increased due to the
smaller pressure range as the efforts of expansion
of air in the clearance volume is less
--Due to smaller working tempreture better
lubricating effect is provided
--In a multi stage Compressor the low pressure
cylinder is lighter
--There is less amount of leakage problems due to
less pressure differace for each stage

19. Advantages of multistage compressor:
--without intercooling the curve of compression will
follow the path (1-4), hence the saving in work
-- Volumetric efficency is increased due to smaller
pressure range
--less shaft power is requred for a given pressure ratio
due to the saving in work input
--Due to smaller working tempreratur, better lubricating
effect is provided
-- better mechanical balance and smoother torque angle
diagram is obtained

20. Comparison between Reciprocating
and Rotodynamic Compressors
Reciprocating Compressors
• Maximum delivery pressure
can be achieved as high as
1000 bar
• These are suitable for low
discharge and high pressure
application
• Air discharge is not continuous
• These compressors require
complicated lubrication system
• Rotational speed is low
Rotodynamic compressors
• Maximum delivery pressure
is up to 10 bar by
multistaging up 40 bar
• These are suitable for high
discharge and low pressure
application
• Air discharge is continuous
• Simple lubrication syste, is
required
• Rotational speed is high

21. • Size of this compressor is
larger than rotary
compressor for same
discharge
• Due to reciprocating parts
balancing is the major
problem
• Maintenance cost is more
• Efficiency is less than 100%
• Running cost is more
• Size of this compressors is
smaller than reciprocating
compressor for same
discharge
• There is no reciprocating
parts, balancing is not
problem
• Maintenance cost is less
• Efficiency is nearly 100%
• Running cost is less