In a screw-type refrigeration compressor, if the shaft of the screw is very long, can it compress many times?
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I have a rather naive question that I’ve been struggling to understand. In a twin-screw oil-injected refrigeration compressor, if the shaft lengths (lead distances) of the two screws are very long, wouldn’t it be possible to rotate them once more after each compression cycle, thereby allowing for many more compression cycles?
If the guide rod is long, the screw length must also be increased to achieve the effect described by the original poster.
In positive displacement compression, the volume space remains unchanged; therefore, a long shaft length (lead) of the screw is meaningless.
As the rotor completes one rotation, the working fluid goes through a cycle of intake, compression, and exhaust; from an axial perspective, the working fluid moves forward by a certain distance. If the shaft is long, another rotation will allow another cycle to take place, during which the fluid is compressed again. So why is it said that the volume does not change?
Eventually, this volume will reach zero; once it reaches zero, the compression ratio becomes theoretically infinite； So the gas will be allowed to exit the volume before the volume reaches zero. As for compressing again, I think it’s still necessary to use two sets of screws in series to achieve this better (taking efficiency and such factors into account). For reference only