Number of stages required depends on the pressure to be developed in compressor. Normally, following relationships are used with pressure and number of stages.
- Single stage compression is used for delivery pressures up to 5.6 kgf/cm2.
- Two stage compressions are used for delivery pressures up to 5.6−35 kgf/cm2.
- Three stage compressions are used for delivery pressures up to 35−84 kgf/cm2.
Advantages of Multistage Compression
- There is little chance of lubrication troubles due to lowering of maximum temperature.
- Leakage loss is minimized.
- There is gain in volumetric efficiency.
- More uniform torque with small size of flywheel can be generated.
Assumption in Multistage Compression: The following assumptions are usually made in calculation of work done in multistage compression:
- For each stage, pressures during suction and delivery remain constant.
- The index (n) in polytropic law is same in each stage of compression.
- Intercooling in each stage is done at constant pressure.
- Low pressure and high pressure cylinders handle the same mass of air.
- There is no interstage pressure drop, i.e., exhaust pressure of one stage equals the suction pressure of the next stage.
Leave a Reply