Information propagation in a subsonic compressor

Julian121 · May 1, 2019, 15:34

Could someone please explain about the information propagating in a subsonic compressor?

As seen in the image, I have put numerical probes in the IGV, Rotor, Stator and casing treatment.

My question is that since information in a subsonic flow regime propagates in upstream direction, should the passing frequencies of the rotor, the stator and the casing treatment or their harmonics appear in the probe I placed in the IGV?

How about the casing treatment?

ghorrocks · May 1, 2019, 18:56

I would imagine so. But whether those frequencies are strong and significant enough to be seen between all the other noise is another matter.

Julian121 · May 2, 2019, 01:57

How about the casing treatment?

Can the the passing frequency of IGV appear in the probe I placed in the casing treatment?

Does it mean that every component in a subsonic compressor feel the presence of other components regardless of their positions?

ghorrocks · May 2, 2019, 02:41

Theoretically, yes. But again, whether the signal from far away features is swamped by noise from other closer features is another matter.

Julian121 · May 17, 2019, 11:19

Which one of instanteous or averaged data should be used to capture blade passing frequency?

I have used a probe which recordrs absoulte pressure.

When I analyse the FFT of this probe, I get half or less than the half of the blade passing frequency.

Why does this happen?

May 1, 2019, 18:56		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I would imagine so. But whether those frequencies are strong and significant enough to be seen between all the other noise is another matter. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

May 2, 2019, 02:41		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Theoretically, yes. But again, whether the signal from far away features is swamped by noise from other closer features is another matter. Julian121 likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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May 2, 2019, 01:57		#3
Julian121 Senior Member Join Date: Aug 2012 Posts: 268 Rep Power: 14	How about the casing treatment? Can the the passing frequency of IGV appear in the probe I placed in the casing treatment? Does it mean that every component in a subsonic compressor feel the presence of other components regardless of their positions?

May 17, 2019, 11:19		#5
Julian121 Senior Member Join Date: Aug 2012 Posts: 268 Rep Power: 14	Which one of instanteous or averaged data should be used to capture blade passing frequency? I have used a probe which recordrs absoulte pressure. When I analyse the FFT of this probe, I get half or less than the half of the blade passing frequency. Why does this happen?