Volumetric efficiency

[skyboy6142]

Hi Friends,

I have a question, I know volumetric efficiency related to volumetric efficiency.
Would you please tell me why when discharge pressure increases, volumetric efficiency decrease ?

Thanks.

[NH3LVR]

In the case of a piston compressor there is a small volume of gas left at the end of the discharge stroke. You have to have some clearance so that the piston does not hit the valve or in case of liquid. This gas has to re-expand as the piston moves downward. No suction gas is drawn in until the piston moves far enough to let this leftover gas expand. The higher the discharge pressure the further the piston has to move before this happens.

[skyboy6142]

In the case of a piston compressor there is a small volume of gas left at the end of the discharge stroke. You have to have some clearance so that the piston does not hit the valve or in case of liquid. This gas has to re-expand as the piston moves downward. No suction gas is drawn in until the piston moves far enough to let this leftover gas expand. The higher the discharge pressure the further the piston has to move before this happens.

Thanks for your reply and help