Hi friends, I wish you are doing well
am searching about equation of SRV GCV
I want to calcul the position % of those valves, according to the speed of TNH and TNL
Thanks for answering me

 

The formula for the pressure that is to be maintained by the SRV has been covered MANY times over nearly three decades on Control.com and threads detailing that formula can be found using the Search feature of Control.com (the magnifying glass icon) at the top of every Control.con webpage. (By controlling the pressure upstream of the GCV the flow through the GCV is proportional to GCV position (often called “stroke” in GE documents).

TNL actually has a couple of meanings/usages. It is primarily the mnemonic used for the LP (low pressure) shaft speed of a two-shaft GE-design heavy duty gas turbine. It has also been used as part of a load-biased HP (High Pressure) shaft speed reference calculation. Without knowing which usage you are referring to we can’t really be of any useful help.

The SRV is used to control the intervalve gas pressure—the pressure of the gas fuel between the outlet of the SRV and the inlet of the GCV. This is also called the P2 pressure, and its signal name is usually FPRG. The GCV, for a single shaft GE-design heavy duty gas turbine driving a synchronous electric generator used to control the power (torque) produced by the HP shaft that is transmitted to the generator rotor to produce generator output current (amperes). [Electric generators convert torque into amperes. Electric motors convert amperes into torque.] This is accomplished using one of two types of speed control: Droop Speed Control or Isochronous Speed Control. The topic of Droop Speed Control (the prevalent type of speed control has been covered MANY TIMES on Control.com. And the reference for the GCV is speed control. For most fuels, the speed control reference is a linear relationship with GCV position, so by controlling the inlet pressure of the GCV to make GCV position (stroke) the fuel flow-rate reference—also a straight line—the load of the machine can be easily manipulated. And, the load produced by the machine is directly proportional to fuel flow.

But, there is no direct relationship in the turbine control system between SRV position and GCV position that can be modeled (simulated) or used to explain how the two valves interact.

None. It’s a popular myth that just won’t die. The Control Specification provided with a GE Mark* turbine control system can be used to help understand the program running in the Mark* that calculates the reference for each of the two valves.

 

Hi Rayan
as you ask about equation of GCV and SRV.in the attached below detail study of the physical equation. but this is dos not make any differently, you have to Know how to calibrate and tune by speed troinc tools in MK* that is the impart end matters
30127_063019042608.pdf
Regards,

 

The MAIN purpose of the SRV (Stop-Ratio Valve) is to be the primary gas fuel shut-off (stop) valve. The secondary purpose of the SRV is to control the gas fuel pressure at the inlet to the GCV (in the intervalve area/cavity). This pressure is commonly referred to as the P2 pressure. The SRV is moved to whatever position is required to maintain the P2 pressure reference (usually signal name FPRG) for the gas fuel supply pressure and the GCV position.

Presuming the gas fuel supply pressure is stable (not varying during machine operation) the main reason P2 pressure increases or decreases is because the opening (position) of the GCV changes as the machine is started, accelerated and loaded or unloaded as required. More load means more fuel (fuel flow-rate is proportional to load) and as the GCV opens to increase the fuel flow-rate the P2 pressure will decrease—unless the SRV opens to maintain the P2 pressure. (The opposite happens during unloading.)

The SRV position varies if the P2 pressure varies—and there are two ways that can happen: if GCV position changes OR if gas fuel supply pressure changes (which, hopefully it doesn’t—it should be stable throughout the range of operation of the machine (start-up to loaded operation; loaded operation to shutdown operation).

The formula for P2 pressure is: FPRG=(TNH * FPGKRG2)+FPKGRG1. FOKGRG2 is a gain (Pressure per percent HO shaft speed) and FPKGRG1 is an offset (pressure). When loaded, a single shaft machine driving a generator will (should) operate at a constant speed (which produces a constant generator frequency). So TNH at rated speed will be 100%. BUT, as the GCV opening changes as the load changes the P2 pressure will tend to change—BUT the SRV regulator will sense the change in P2 pressure and move the SRV to whatever position is needed to keep the P2 pressure constant (because when the machine in this example is producing power it will do so at a constant speed (TNH will be 100%, plus or minus a few hundredths of a percent under normal operating conditions)).

Let’s say the machine in our example has a GCV position of 20% at FSNL (zero load). Further let’s say the GCV at rated load has a position of 70% (these are actual fairly typical values). This means that as load is increased from zero to rated the GCV position will increase from 20% to 70%—a range of 50%. 25% of rated load will require 25% of the range of GCV position—which is 12.5% of GCV position. So to go from zero load to 25% of rated the GCV will open from 20% to 32.5%. To go to 75% of rated load the GCV will have to open 75% of its loaded operating range (50%)—or 37.5% of the loaded operating range. To go from 25% of rated load to 75% of rated loa, the GCV will move from 32.5% to 57.5% opening.

As the GCV opens as load increases, the P2 pressure will tend to decrease BUT the SRV regulator will move the SRV to whatever position is necessary to keep the P2 pressure constant (because TNH should be constant for a generator drive machine)—meaning as the GCV opens so too will the SRV (at rated speed). BUT the P2 pressure should remain constant (as should the gas fuel supply pressure remain relatively stable/constant).

If you are referring to a two-shaft machine most of these same things happen, but the load reference will usually be centrifugal compressor discharge pressure (and/or flow-rate) and normal operating speed will usually be a range of speed not a fixed speed (which means P2 pressure will also vary somewhat depending on the actual machine speed).

That’s all I got.