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ACTIVE LEARNING PROCESS. Branch: Computer Engineering. Guided By : Prof. Jugal Panchal. Prepared By :. NAYAK RURUBEN JITENDRA - 13BECEG121 SUTHAR HARSHIL SHAILESHKUMAR 13BECEG118 PANCHOLI ADITIBEN J. - 13BECEG108. Introduction.

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Branch: Computer Engineering

Guided By :

Prof. JugalPanchal

Prepared By :






  • Types of compressors.
  • Positive displacement compressors.
  • Dynamic compressors.
  • Reciprocating compressor.
  • Rotary vane compressor.
  • Applications of compressors in industries.
  • Conclusion

Principles on which compressors work:

  • A compressor is a mechanical device that increases the pressure of a gasby 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.
positive displacement compressor
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, vane compressors & so on.

dynamic compressors
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.

reciprocating compressors
Reciprocating compressors
  • In a reciprocating compressor, a volume of gas is drawn into a cylinder; it is trapped and compressed by piston, then discharged into the discharge line. The cylinder valves control the flow of gas through the cylinder; these valves act as check valves.

Fig : of reciprocating compressor is as shown in next slide.

reciprocating compressors1
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.
reciprocating compressors2





Discharge volume


Suction intake volume

Piston displacement

Total cylinder volume


Reciprocating compressors
  • The states of the refrigerant in a reciprocating compressor can be expressed by four lineson a PV diagram as shown in Fig
reciprocating compressors3
Reciprocating compressors
  • The suction valve opens at point 4.
  • As the piston travels toward the bottom dead center, the volume of the cylinder increases and the vapor flows into the cylinder.
  • The pressure inside the cylinder is slightly less than suction line pressure. The pressure difference pushes the valve open on during the suction stroke.
reciprocating compressors4
Reciprocating compressors
  • At point 2, the pressure inside the cylinder has become slightly greater than discharge line pressure.
  • This causes the valve opening allowing the gas to flow out of the cylinder.
  • The volume continues to decrease toward point 3, maintaining a sufficient pressure difference across the discharge valve to hold it open.
reciprocating compressors5
Reciprocating compressors
  • At point 3, the piston reaches the top dead center and reverses direction.
  • At top dead center, as the piston comes to a complete stop prior to reversing direction, the pressure across the valve is equal.
  • So, the discharge valve is closed.
  • As the piston moves towards point 4, the volume increases and the pressure decreases in the cylinder.
  • The gas trapped in the cylinder expands as the volume increases until to point 4.
  • At point 4, the gas pressure inside the cylinder becomes less than the suction line pressure, so the suction valve opens again.
  • The cycle then starts over again.
  • The shape of the re-expansion line (Line 3-4) is dependent on the same compression exponent that determines the shape of the compression line.
rotary vane compressors
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.
rotary vane compressor1
Rotary vane compressor
  • A: Air is drawn in through the intake valve. B: Air is contained between the rotor and stator wall. C: Air is compressed by decreasing volume. D: High pressure air passes into the primary oil separator. E: Remaining traces of oil are removed in a final separator element, providing high quality air. F: System air passes through the after cooler, removing most of the condensate. G: Oil is circulated by internal air pressure. It passes through an air-blast oil cooler and filter before being returned to the compressor. H: Air flow is regulated by an inbuilt modulation system.

Energy Efficiency Opportunities

1. Location

  • Significant influence on energy use

2. Elevation

  • Higher altitude = lower volumetric efficiency

Energy Efficiency Opportunities

3. Air Intake

  • Keep intake air free from contaminants, dust or moist
  • Keep intake air temperature low
  • Every 4 oC rise in inlet air temperature = 1% higher energy consumption
  • Keep ambient temperature low when an intake air filter is located at the compressure.
application of compressors
Application of compressors
  • Reciprocating compressors are typically used where high compression ratios (ratio of discharge to suction pressures) are required per stage without high flow rates, and the process fluid is relatively dry.
  • Screw compressors: Trailer mounted diesel powered units are often seen at construction sites, and are used to power air operated construction machinery.
application of compressors1
Application of compressors
  • P.E.T bottling industries, gas filling stations usually use reciprocating compressors.
  • Processing equipment, Oxygen Generators Oil Atomization use compressors of required capacity.

Venu Manohar

  • Air compressors: a compressor that takes in air at atmospheric pressure and delivers it at a higher pressure.
  • Compressors serve the basic necessities & form an integral part of the company .