Atmiya College of Science & Technology

Air Compressors

Elements of Mechanical Engineering

Roll NO. Name Enrollment no.

56 Bhavya Vasani (GL) 130030117058

33 Meet Patel 130030117036

51 Bhargav Thakur 130030117055

55 Hitesh Vavnotiya 130030117059

56 Chintan Vyas 130030117060

08 Deep Vyas 130030117009

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• Intake air filters• Inter-stage coolers• After coolers• Air dryers• Moisture drain traps• Receivers

Main Components in Compressed Air Systems

Introduction The machine which takes in air or any other gas at low

pressure and compresses it to high pressure are called compressors.

A compressor is used for increasing the pressure of air is called Air compressor.

Classification of compressor:-

The compressors may be classified according to

1) Method of compression:a) Reciprocating compressorb) Rotary compressorc) Centrifugal compressor

2) Delivery Pressure:3) Principle of Operation:

a) Positive displacementb) Rotodynamic or steady flow compressor

4) The number of stages:a) Single stageb) Multi stage

5) The number of cylinder:a) Single cylinderb) Multi cylinder

6) The pressure limit7) Volume of air delivered8) Fluid to be compressed:

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Two Basic Compressor TypesTypes of Compressors

Type ofcompressor

Positivedisplacement

Reciprocating Rotary

Dynamic

Centrifugal Axial

• Used for air and refrigerant compression• Works like a bicycle pump: cylinder volume reduces while pressure increases, with

pulsating output• Many configurations available• Single acting when using one side of the piston, and double acting when using both

sides

Reciprocating Compressor

Types of Compressors

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Screw compressor

• Rotors instead of pistons: continuous discharge

• Benefits: low cost, compact, low weight, easy to maintain

• Sizes between 30 – 200 hp• Types

• Lobe compressor• Screw compressor• Rotary vane / Slide vane

Rotary Compressor

Types of Compressors

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• Rotating impeller transfers energy to move air

• Continuous duty

Centrifugal Compressor

Types of Compressors

• Designed oil free

• High volume applications > 12,000 cfm

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• Efficiency at full, partial and no load• Noise level• Size• Oil carry-over• Vibration• Maintenance• Capacity• Pressure

Comparison of Compressors

Types of Compressors

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• Capacity: full rated volume of flow of compressed gas

• Actual flow rate: free air delivery (FAD)• FAD reduced by ageing, poor maintenance,

fouled heat exchanger and altitude• Energy loss: percentage deviation of FAD

capacity

Capacity of a Compressor

Assessment of Compressors

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Compressor Efficiency

Assessment of Compressors

• Most practical: specific power consumption (kW / volume flow rate)• Other methods

• Isothermal• Volumetric• Adiabatic• Mechanical

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Isothermal efficiency

P1 = Absolute intake pressure kg / cm2Q1 = Free air delivered m3 / hrr = Pressure ratio P2/P1

Compressor Efficiency

Assessment of Compressors

Isothermal efficiency = Actual measured input power / Isothermal power

Isothermal power (kW) = P1 x Q1 x loger / 36.7

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Volumetric efficiency

D = Cylinder bore, meter L = Cylinder stroke, meter S = Compressor speed rpm χ = 1 for single acting and 2 for double acting cylinders n = No. of cylinders

Compressor Efficiency

Assessment of Compressors

Volumetric efficiency= Free air delivered m3/min / Compressor displacement

Compressor displacement = Π x D2/4 x L x S x χ x n

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• Consequences• Energy waste: 20 – 30% of output• Drop in system pressure• Shorter equipment life

• Common leakage areas• Couplings, hoses, tubes, fittings• Pressure regulators• Open condensate traps, shut-off valves• Pipe joints, disconnects, thread sealants

Leaks

Assessment of Compressors

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• Higher pressure• More power by compressors• Lower volumetric efficiency

• Operating above operating pressures• Waste of energy• Excessive wear

Energy Efficiency Opportunities

. Pressure Settings

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. Minimizing Leakage• Use ultrasonic acoustic detector• Tighten joints and connections• Replace faulty equipment

Energy Efficiency Opportunities

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. Controlled usage

• Do not use for low-pressure applications: agitation, combustion air, pneumatic conveying

• Use blowers instead

. Compressor controls

• Automatically turns off compressor when not needed

Energy Efficiency Opportunities

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. Maintenance Practices

• Lubrication: Checked regularly• Air filters: Replaced regularly• Condensate traps: Ensure drainage• Air dryers: Inspect and replace filters

Energy Efficiency Opportunities

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Compressors & Compressed Air

SystemsTHANK YOU FOR YOUR ATTENTION

© UNEP GERIAP