Screw Compressor pulsations

[AOkasha]

Hello all,

I am trying to measure the dynamic pressure out of a screw compressor (Atlas Copco GA7) with WCT-312 pressure transducer, but I cannot capture any pulsations

I have investigated GA7, and I think that it doesnot contain a muffler or silencer.

Does anyone can help me to know why the pulsations are suppressed

Thank you

 

[zdas04]

What would cause pulsations in a screw compressor? We see pulsations problems in a recip because EVERYTHING in a recip pulsates--from valve slam to piston travel participates in pulsation.

In a screw, there is never a shut-off/turn-on (no valves) event so the flow is micro-smooth (there are macro variations, but on a micro basis it is darn smooth).

David

 

[AOkasha]

These pulsations caused by a screw compressor are less than those caused by a reciprocating one working at the sama line pressure.

In screw compressor; the compression mechanism will create pulses in the flow because the lobes from each screw will be forced close together at specific points in the rotational line, which creates
pulses in the compressed gas flow.

you can check this:

http://www.gmrc.org/ckfinder/userfi... and Silencer Design for Screw Compressor.pdf

 

[zdas04]

If you knew, why'd you ask? Apparently SWrI has everything you'd ever want to know about pulsation in a screw except that you can't measure it. Minor point. If SWrI says its there it isn't important that the instruments we use to quantify pulsation can't see it.

David

 

[AOkasha]

I don't know what do you mean

 

[pmover]

tell us, how do you know that the pressure pulsations exist?

-pmover

 

[DLite30]

I don't think the sensor you're using is appropriate for what you're wanting to do. At least, it isn't one I would choose--the data sheet is rather vauge regarding frequency response. I would use a small piezo-electric transducer.

What device are you using, a CSI, like a 2130?

 

[crjones]

The pulsations are at four times per revolution, the rotor passing frequency. So the basic frequency is rpm*4/60. There are several other frequencies in the gas flow based on the discharge port. I agree with DLiteE30 you need a better transducer.

 

[Tuckabag]

I would think the rotor passing freq equation does not ring true for a screw type compressor, more so for a roots style blower where the you get opening and closing of a pocket of gas along the entire length of the rotor. This naturally doesn't occur with the screw rotors as mentioned previously due to the helical profile.
The screws certainly can/do scream during operation but I'd expect the outlet pressure to be smooth and pulsation free unlike a recip or a roots type.