ADVANTAGES OF MULTI - STAGE COMPRESSION ARE :

1. Improved overall volumetric efficiency .If all compression were done in one cylinder the gas in the clearance volume would expand to a large volume before the new intake could begin. Th results in a very low volumetric efficiency. By cooling the gas between the stages a much higher efficiency can be obtained.

2. A reduction in work required per stroke, and therefore the total driving power,.

3. Size and strength of cylinders can be adjusted to suit volume and pressure of gas.

4. Multi - cylinders give more uniform torque and better mechanical balance thus needing smaller flywheel.

5. Since the maximum temperature reached during the compression process is greatly reduced by intercooling lubrication difficulties and explosion hazards are lessened.

6. Leakage Losses are reduced considerably.

Practice appears to indicate that the economical value of pressure ratio per stage is in range of 3 to 5. For compression of atmospheric air, single- stage machines are often used up to 550 kPa discharge pressure, two - stage from 350kPa to 2.1 MPa, three stage from 2.1 MPa to 7.0 MPa, and four of more stages for higher purposes.

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Mechinopedia For Mechanical Engineers

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