7 replies to this topic

[novagig]

Dear all,

 

I have a question about capacity control of fixed speed compressor. (especially inlet guide vane vs. control valve suction throttling)

 

1) I'm trying to define the pros & cons of inlet guide vane and control valve suction throttling

 

2) Turn down ratio of fixed speed compressor (inlet guide vane and control valve suction throttling) compared with variable speed compressor

 

Thank you in advance for your help.

[Bobby Strain]

Tried searching yet? These questions have been addressed in voluminous detail.

 

Bobby

[novagig]

Thank you Bobby.

 

Yes, I did.

 

But I am confusing.

Because my colleagues who was majored mechanical and chemical engineering have a different thinking about this compressor control.

[ankur2061]

novagig,

 

 

While I do not have a detailed comparison on IGVs and suction throttling, most literature on cenrifugal compressor flow control mentions that the Inlet Guide Vane (IGV) is much more efficient than suction throttling using a control valve. One obvious explanation is that by suction throttling, you are also expanding the gas to a lower pressure across the throttling valve and then re-compressing the gas with a higher pressure ratio, thus making the process more inefficient.

 

Centrifugal compressors have a much lower turn-down compared to a reciprocating compressor. However, with the modern variable speed drive technology available you can still turn-down to 20%. Obviously, it may be difficult to achieve the same turn-down with an IGV system or suction throttling.

 

Regards,

Ankur.

[Zauberberg]

See attached document. First 6 pages provide you with comparison of all capacity control methods for centrifugal compressors.

Attached Files

•  Compressor Control & Optimization.pdf   617.55KB   164 downloads

[novagig]

Thank you very much, Ankur Srivastava and Zauberberg.

 

Your valuable opinions are really helpful.

 

However, my colleague who was majored mechanical engineering said,

"suction throttling control is only for start up and has little availability of capacity control."

 

So, if it is possible, I wish to know the turn down ratio of fixed speed compressor (suction throttling control and IGV) in comparison with variable speed drive.

 

Thank you in advance for your help.

[Zauberberg]

For the same compressor (at fixed speed), turndown conditions will be the same regardless which control method you use, and it will be defined by the surge line (or proximity to surge). The only difference between various methods is how much less energy the compressor will consume by operating at lower flows. Suction throttling is less efficient method

[ankur2061]

novagig,

 

Have a look at the following link which tells about advanced control techniques for centrifugal compressors:

 

http://turbolab.tamu...5/05-TAKEDA.pdf

 

Regards,

Ankur.