Principle of Operation
A centrifugal compressor accelerates the velocity of the gases (increases kinetic energy) which is then converted into pressure as the gas flow leaves the volute and enters the discharge pipe.
- Centrifugal compressors consist of stationary casing
- Containing rotating impeller (imparts a high velocity of air),
- Fixed diverging passage (The air is decelerated with rise in static pressure).
- Impeller may be single or double-sided
Basic Components
Impellers, Vanes, Volutes, Suction Eyes, Discharge lines, Diffuser Plates, Seals, Shaft, Casing
Suction Vane Tips = Part of the impeller vane that comes into contact with gas first.
Discharge Vane Tips = Part of the impeller vane that comes into contact with gas last
Impellers, Vanes, Volutes, Suction Eyes, Discharge lines, Diffuser Plates, Seals, Shaft, Casing
Suction Vane Tips = Part of the impeller vane that comes into contact with gas first.
Discharge Vane Tips = Part of the impeller vane that comes into contact with gas last
Types of Centrifugal Compressors
Single- Stage: Compress the gas once
Use for high gas flow rates, low discharge pressures
Multi- Stage: Take the discharge of one stage and pass it to the suction of another stage
Use for high gas flow rates, high discharge pressures
Usually operate at speeds > 3,000 rpm.
Air is sucked into the impeller eye and whirled at high speed by the vanes of the impeller disc.
The static pressure increases from eye to tip
Remainder of static pressure rise occurs in diffusers.
Normally half of pressure rise occurs in the impeller and 50% in diffuser.
Some stagnation pressure loss occurs.
Single- Stage: Compress the gas once
Use for high gas flow rates, low discharge pressures
Multi- Stage: Take the discharge of one stage and pass it to the suction of another stage
Use for high gas flow rates, high discharge pressures
Usually operate at speeds > 3,000 rpm.
Air is sucked into the impeller eye and whirled at high speed by the vanes of the impeller disc.
The static pressure increases from eye to tip
Remainder of static pressure rise occurs in diffusers.
Normally half of pressure rise occurs in the impeller and 50% in diffuser.
Some stagnation pressure loss occurs.
Why centrifugal compressor?
Centrifugal compressors are extremely popular because most are close to being oil-free. Although oil is used in the compressor which can create an aerosol, the special sealing systems used in most centrifugals reduce the level of oil contaminants to very low levels. Centrifugals are also popular because of the very large capacities (> 100,000 CFM) that are possible with a single compressor, combined with fairly high pressures (100 to 350 Kg/cm2). Centrifugals are economically attractive when flows are high.
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