GANDHINAGAR INSTITUTE OF TECHNOLOGY

ACTIVE LEARNING ASSIGNMENTELEMENTS OF MECHANICAL ENGINEERING(2110006)

AIR COMPRESSORSPREPARED BY: GUIDED BY:

Jay Chovatiya (150120116011) PROF. Sajan Chourasia

BRANCH: INFORMATION TECHNOLOGY- D-D1SEMESTER:2 (EVEN)

GOALS:IntroductionClassificationTerminologyReciprocating compressorApplication

AIR COMPRESSORS• An air compressor is a device that converts

power into potential energy by forcing air into a smaller volume and thus increasing its pressure.

• The energy in the compressed air can be stored while the air remains pressurized.

CLASSIFICATION:Air Compressors are classified on various categories, according to the: Principle of Working:1. Positive displacement2. Dynamic(Negative displacement)

Number of Stages:1. Single stage - pressure ratio upto 5 – 6.2. Multi stage – pressure ratio more than 6.

Acting of Piston:1. Single Acting 2. Double Acting

Number of Cylinders:1. Single Cylinder 2. Double Cylinder

Pressure Ratio:1. Fan- pressure ratio upto 1.12. Blower- pressure ratio 1.1 to 2.53. Compressor- pressure ratio more than 2.5

Method of Cooling:1. Air cooled 2. Water cooled

According to the Arrangement of Cylinder:1. Vertical 3. V-type2. Horizontal 4. Radial

AIR COMPRESSOR TERMINOLOGY SINGLE ACTING COMPRESSOR:Compressor in which suction, compression and delivery of air takes place only in one side of piston.

DOUBLE ACTING COMPRESSOR:Compressor in which suction, compression and delivery of air takes place on both sides of piston.

SINGLE STAGE COMPRESSOR:Compressor in which compression of air from suction pressure to delivery pressure takes place in one cylinder .

MULTI STAGE CYLINDER:Compressors in which compression of air from suction pressure to delivery pressure takes place in more than one cylinder.

COMPRESSION RATIO:It is defined as a ratio of an absolute discharge pressure to absolute suction pressure.

VOLUMETRIC EFFICIENCY:Defined as the ratio of actual volume of air taken in the compressor to the swept volume of the compressor.

COMPRESSOR CAPACITY:Volume of the air delivered by the compressor.Expressed in cubic metre per minute or cubic metre per second.

RECIPROCATING COMPRESSORS

• A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure

• The intake gas enters the suction manifold, then flows into the compression cylinder where it gets compressed by a piston driven in a reciprocating motion via a crankshaft, and is then discharged.

• It also consists of inlet valve and delivery valve and they operated because of the pressure difference across it.

RECIPROCATING AIR COMPRESSOR

Working:• When piston moves downward during suction stroke, the

compressed air left in the cylinder expands and due to expansion, the pressure inside the cylinder falls below atmospheric pressure which result in the opening of inlet valve opens and delivery valve remains closed and fresh air is sucked into the cylinder.

• At the time of upward stroke, there is slight increase in pressure which closes the inlet valve and when both the valves are closed the pressure inside the valve increases.

• So when the pressure inside the cylinder increases above the compressed air pressure on outside of delivery valve,the delivery valve remain open and compressed air is delivered into the receiver. So, at the end piston move downward and as pressure decreases delivery valve remain closed.

• When pressure falls below atmospheric once again inlet valve opens and thus the cycle is repeated.

Application:

•  Applications include oil refineries, gas pipelines, chemical plants, natural gas processing plants and refrigeration plants. One specialty application is the blowing of plastic bottles made of polyethylene terephthalate (PET).

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