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The Scroll Compressor

Displacement Compressors Compressor Types Compressors Compressed Air Wiki

There are two ways of compressing air, dynamic and displacement compression. We are talking about the latter here. One of these displacement compressors is the scroll compressor.

What are scroll compressors?

the scroll compressor, a graphic of the inside
A scroll compressor is a type of (usually) oil-free orbiting displacement compressor, i.e. it compresses a specific amount of air into a continuously decreasing volume. The compressor element consists of a stator spiral fixed in a housing and a motor-driven eccentric, orbiting spiral.

The spirals are mounted with 180° phase displacement to form air pockets with a gradually varying volume. This provides the scroll elements with radial stability. Leakage is minimized because the pressure difference in the air pockets is lower than the pressure difference between the inlet and the outlet. The orbiting spiral is driven by a short-stroke crankshaft and runs eccentrically around the centre of the fixed spiral. The inlet is situated at the top of the element housing.

When the orbiting spiral moves, air is drawn in and is captured in one of the air pockets, where it is compressed gradually while moving towards the centre where the outlet port and a non-return valve are situated. The compression cycle is in progress for 2.5 turns, which virtually gives constant and pulsation-free air flow. The process is relatively silent and vibration-free, as the element has hardly any torque variation as compared to a piston compressor, for example.

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