7 replies to this topic

[amitchemengg]

How guide vane at suction regulates flow and pressure of the centrifugal compressor discharge?
Does one single disoriented blade affects the operating parameters of compressor?
Like capacity, surge line, disharge pressure....
We have a centrifugal compressor for air service with guide vane at suction. One of the blade of guide vane is immovable.
Compressor capacity is different from that of design.
I donot have much information on fluid dynamics in compressor, but think that one incongruent blade can lead to backmixing at suction thus reducing capacity..
If my thinking is wrong?
Plz lead me

[fallah]

Hi,

 

IGV will regulate the mass flow rate through the centrifugal compressor and will change the pressure which the first stage impeller can sense. Throttling the IGV will increase the pressure drop causing a drop in gas density hence a reduction in mass flow rate.

 

IGV varies the inlet angles to the first stage impeller blades hence varying the compressor capacity, then obviously when there is an immovable blade in IGV compressor capacity will be affected.

[breizh]

Hi Amit ,

To solve your problem , you need to talk to the manufacturer and perform the necessary maintenance to get your equipment in conditions .

Nothing else will work !

My thoughts

 

Breizh.

[ankur2061]

Amit,

 

Nice articles on IGVs at the following link:

 

http://www.plantserv...3/111/?show=all

 

http://www.plantengi...08b4ea6760.html

 

The stuck guide vane blade, if possible should be removed. Normally IGVs are mounted one pipe diameter upstream of the suction inlet flange.

 

Another option would be to make it open (parallel to the inlet axis) and keep it in that condition.

 

The only effect of both the aforementioned actions would be to reduce the available turn down on the compressor

 

The phenomena of back mixing in the impeller as you mentioned is related to surge.

 

Regards,

Ankur

[amitchemengg]

Thanx everyone..
Your information is really a help.
I am looking forward to solve the issue with ur provided information

[amitchemengg]

Ankur2061, I meant backmixing at suction, will it lead to reduction in capacity of the compressor?
We have experinced reduction in capacity and surging at lower line frequencies...
Our people not allowing overtravel of guide vane blades, and associating overtravel to surging..
I disagree the reason, but don't have solid proof..
I feel correction the immovable blade can reestablish tge original capacity of the compressor...
Guide vane blades make swirls at inlet and impeller takes those swirls at relatively no velocity change or minimal change, so that streamlining is maintained.
But one immovable blade can affect this streamlining and induces its effect to adjacent blades, so that in total effect becomes bigger....
I hve no justification(theoretical), have no equations describing flow regime,,, ...
I want to know if my thinking is correct?
Or where i can get correct answer?

[ankur2061]

Amit,

 

A centrifugal machine creates a vacuum at the impeller eye, so back mixing at suction is something which I am unable to comprehend.

 

To my knowledge, attributing surge to one guide vane blade does not make really any sense.

 

Many a times certain out of the box solutions need to be applied to solve the problem.

 

But one immovable blade can affect this streamlining and induces its effect to adjacent blades, so that in total effect becomes bigger....

 

Is this your own analysis or do you have some literature to support your statement?

 

By making the blade parallel to the flow axis, the effect (whatever little) will be negated. The swirl caused by any angle of the blade with the axis will not be there for a parallel blade.

 

Regards,

Ankur.

[amitchemengg]

thanx ankur2061,
That was my thinking..
I have read that guidevanes slightly overtraveled can enhance capacity by about 20%...
On that basis i made my conclusion...
May i be wrong...