Why does a reciprocating compressor reverse direction when rotated under pressure with no load?
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It is a two-stage, four-row horizontally arranged double-acting compressor; during the crankshaft rotation process, the pressure within the unit does not drop, remaining at around 5 MPa. The load is set to zero at this point, and the intake valve opens. Why does it reverse direction after the crankshaft rotation is completed?
I have also seen this phenomenon with my own eyes; usually people don’t pay attention to it.
Dude, I have a question: when the unit is under load, the air valve is already open. Normally, as the crankshaft moves through the compression stroke, the gas should return to the pipes, so there shouldn’t be enough force to cause the unit to reverse direction. Can you get sober a bit? Thank you!
Logically, at this point the gas forces acting on the piston parts should balance each other and not reverse direction. It is suspected that it might be due to the crankpins and counterweights in the crankcase.
Common situations that occur during shaft turning
It is likely that when the piston approaches the dead centers at both ends of the cylinder, the reaction force generated by the expansion of the high-pressure gas remaining in the clearance pushes the piston to move.
It doesn’t have to reverse every time; as long as it is stopped just before reaching the dead center, it will reverse.
When cranking the engine, one cylinder is nearly at top dead center; stopping at this point will cause it to reverse direction
Thank you all for your explanations! If the reversal is caused by gas expansion near the dead center, then is it useless to turn on the return line? In other words, is there no solution to this problem?
I haven’t paid much attention to this aspect; I’ll keep an eye on it in the future