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Gas Turbine Fuel Gas Flow Measurement
Formula used for GE Gas Turbine Fuel Gas Flow Measurement.


We are having GE Frame 6B Gas turbines in our plants. For Fuel Gas Flow Measurement, they employ two differential pressure transmitters, one for high dp and one for low dp. Furthemore, they also employ one pressure transmitter and one temperature transmitter for so called pressure and temperature compensation.

I'm interested in knowing the formula which they use to calculate the compensated Fuel Gas Flow. I had a chance to see in the Mark VI control system, where these inputs are feeded to the block called GASFLWC1 which finally outputs the Mass Flowrate QM. The block has the following inputs:

High DP
Low DP
FQKGDB (0.25 inH2O)
FQKGSG (0.634502) Specific Gravity
GQKGG (2.047 n/d) Gas Constant

Can anybody tell me what formula they have employed with the above mentioned inputs to calculate the compensated mass flow rate QM?



Does the application code in the turbine control system (you didn't say what it is) not have a GASFLWCALCVn block? All of the internals of the block are shown in the graphic depiction of the block, and if the turbine control system is a Mark VI or -VIe if you right-click on the block and click on 'Item Help' a Help window will open with more information.

If the calculation is done in a macro in a Mark VI or -VIe you can dive into the macro in the Tree view window to see how the calculation is done to determine the formula.

Also, sometimes (more often than not) the formula is shown in the Control Specification, usually in Section 05.02.

If the turbine control system uses MBC (Model-Based Control) it might be done slightly differently.

It would be helpful if you told us what version of turbine control system is used on the turbine.


The control system is Mark VI. We just can't enter inside the block as it looks like blocked from GE. That is why i'm interested in knowing what formula this block uses to calculate mass flow rate.



>The control system is Mark VI. We just can't enter inside
>the block as it looks like blocked from GE.

What is the name at the top of the "block" in the main pane of the Toolbox window?

If the name is something like 'GASFLWCALCVn' then it's a gas turbine block, and you should be able to right-click on the block and in the pop-up that opens click (left-click) on 'Item Help'. If there is no Help for the block, a dialog should pop up to say "No help is available for this block" (or something to that effect).

If the block has no name like the one above at the top, or Toolbox says there's no help available for the block, then it is most likely a macro--written using "primitives" like ADD, SUB, MULT, DIV and SQRT, etc. In this case, you have to expand the macro in the Tree View pane of the Toolbox window (the tall narrow pane on the left). To expand the macro you need to click on the icon next to the macro name, and Voila! you will see, in the main pane of Toolbox, the macro magically open and display its contents to you. The passed parameter signal names will not be the same inside the macro as outside of it, but may be very similar--similar enough to follow the signals through the macro's functions to see what is happening.

Did you look in the Control Specification drawing to see if the formula is listed in the Gas Fuel section of the drawing?