Hello to everyone,

Regarding GE 7FA igv opening during startup,

In manuals they mentioned, During start up, the inlet guide vanes are held fully closed, a nominal 27 degree angle, from zero to 83.5% corrected speed. Can anyone tell me if it is full closed then? what is the way of airflow from 0 to 83.5% of corrected speed? (this might be a childish question).

In igv vs corrected speed trend they mentioned 27 degree as mechanical stop of IGV.

 

Hello, PJK,

Engineers are really very poor technical writers. In the case of IGVs, "fully closed" and "fully open" generally refer to the minimum and maximum allowable IGV angles during operation--including starting, acceleration, full speed operation, and shutdown/deceleration.

In general, the Control Constants CSKGVMIN and CSKGVMAX reflect the minimum- and maximum allowable IGV angles during operation. And engineers refer to these limits as "fully closed" and "fully open", respectively, because these are the closed and open limits for operation.

There are mechanical stops on the IGV actuator and rack mechanisms to prevent travel too much further past these "closed" and "open" operating limits, usually one or two degrees less than the closed operating limit and one or two degrees more than the open operating limit.

So, it's really just another example of poor documentation--which has to be read for intent rather than literal content. "Fully closed" means the minimum operating angle during starting (until approximately 80% TNH), CSKGVMIN; "closed" refers to the minimum operating angle at Full Speed-No Load (100% speed prior to synchronization); and "fully closed" refers to maximum operating angle during loaded operation, CSKGVMAX.

Hope this helps!

 

Sure it helped me a lot. and thanks for your valuable information.

 

<b>>>CORRECTION<<</b>

>"Fully closed" means the minimum operating
>angle during starting (until approximately 80% TNH),
>CSKGVMIN; "closed" refers to the minimum operating angle at
>Full Speed-No Load (100% speed prior to synchronization);
>and "fully closed" refers to maximum operating angle during
>loaded operation, CSKGVMAX.

Should have read:

"Fully closed" means the minimum operating angle during starting (until approximately 80% TNH), CSKGVMIN; "closed" refers to the minimum operating angle at Full Speed-No Load (100% speed prior to synchronization); and <b>"fully open"</b> refers to maximum operating angle during loaded operation, CSKGVMAX.

Sorry for any confusion!!!

 

Really i got confused but i read 2 to 3 times and i got what you told sir.

Reply to my question itself i felt very happy, and once again thank you very much.