IN gas turbine, frame6, on what p2 pressure depends

 

The P2 pressure reference is calculated by the Speedtronic panel using the formula:

FPRG = (TNH * FPKGNG) + FPKGNO

where
FPRG = Fuel Pressure Reference, Gas (in psig)
TNH = Turbine Speed (in percent)
FPKGNG = P2 Pressure Reference Gain (in psig/% Turbine Speed)
FPKGNO = P2 Pressure Reference Offset (in psig)

When the turbine is at 100% speed and producing power, the P2 pressure reference is relatively stable, as stable as the turbine speed, at least.

But that doesn't mean the SRV (Stop-Ratio Valve) will be at a stable or steady position when the turbine speed is steady and stable. Because as the GCV (Gas Control Valve) downstream of the SRV opens to increase fuel flow and power output the P2 pressure would tend to decrease if the SRV didn't change position. But, as the P2 pressure tends to decrease as the GCV opens the SRV will open to keep P2 pressure equal to the P2 pressure reference. The opposite happens when the GCV closes to reduce fuel flow and power output.

So, P2 pressure is a function of turbine speed. The SRV is positioned to make the actual P2 pressure equal to the P2 pressure reference, even if turbine speed isn't changing.

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