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FSR Split & DLN Split
Why are FSR split & DLN split divided into P1, P2, P3 & Q values?
1 out of 1 members thought this post was helpful...

In my machine (7FA.05) having FSR SPLIT & DLN SPLIT. this both splits values (in %) are divided by P1, P2, P3 & Q. Below values were taken from one of my prior working days: For FSR split #P1-11.7/P2-12.6/P3-32.7/Q-4.6. During this time unit in PRE SELECT LOAD MODE for 150MW with gas fuel firing.

For DLN split #P1-19.0/P2-20.5/P3- 53.0/Q-7.5.

Any one please give clear answer for above one, because of i am newer for this one. even i searched my plant control document also, but i didn't get clear answer for above one. I want come to know what is meaning of FSR SPLIT & DLN SPLIT with its origin and why them were divided to P1, P2, P3 & Q.

1 out of 2 members thought this post was helpful...


What was the FSR at the time you recorded the values?

You say you are new to the 7FA.05. Do you have experience with other gas turbines? If so, what manufacturer/model?

Have you had a look at the P&IDs for the unit--particularly the Gas Fuel system?

Dear CSA,

Not only that time always FSR VALUE=FSR SPLIT VALUE(SUM OF P1+P2+P3+Q).

Previously i have no experience in gas turbines.

When our previous conversation, at the time checked P&ID and manuals, but i didn't get clear answer. I want send fuel gas system P&ID to you for your kind reference, pls send your mail ID, If you interest.

3 out of 4 members thought this post was helpful...


FSR (Fuel Stroke Reference) is another way of expressing total fuel flow-rate reference--in percent. For gas fuel, if one maintains a constant pressure upstream of a GCV (Gas Control Valve) the flow through that valve is more proportional to stroke, or valve travel, or valve position (flow is said to be "linear with stroke"). Most gas fuel systems used on GE-design heavy duty gas turbines use a SRV (Stop-Ratio Valve) upstream of any GCV(s) to maintain a constant pressure upstream of the GCV(s) during operation at rated speed (frequency). So, the flow-rate through the GCV(s) is proportional to stroke (more stroke means more flow; less stroke means less flow).

Most gas fuel systems used on GE-design heavy duty gas turbines with DLN combustors use one SRV to control the pressure upstream of several (usually four) GCVs. Each GCV controls the flow-rate to a particular manifold that supplies a particular set of nozzles in the combustor. (In DLN combustors, there are multiple nozzles in each combustor to control where the fuel enters the combustor so as to help reduce emissions.)

So, FSR is split between the various fuel manifolds/nozzles, and the sum of the amount of FSR to each manifold/nozzle equals the total amount of FSR.

As for the DLN Split, well, for P1 (sometimes called PM1) 11.7% is approximately 19.0% of 61.6% FSR. For P2 (sometimes called PM2) 12.6% is approximately 20.5% of 61.6% FSR. For P3 (sometimes called PM3) 32.7% is approximately 53.0% of 61.6% FSR. And, for the Quaternary nozzles/manifold 4.6% is approximately 7.5% of 61.6% FSR. 19.0% + 20.5% + 53.0% + 7.5% = 100.0%. So, 19.0% of the current total fuel flow-rate is going to P1 (PM1); 20.5% of the current total fuel flow-rate is going to P2 (PM2); 53.0 of the current total fuel flow-rate is going to P3 (PM3); and 7.5% of the current total fuel flow-rate is going to the Quaternary (Quat).

I don't know why they're essentially saying the same thing twice or in two different ways, but possibly it has something to do with MBC (Model-Based Control) or DLN tuning.

Hope this helps!

Dear CSA,

Thank you very much to given clear answer.

1 out of 2 members thought this post was helpful...


Thanks for the feedback! (You can also click on the Thumbs Up or Thumbs Down icon of any post or reply, though if you click on Thumbs Down it would be nice to know why you didn't find the information/post helpful.)

As for the Gas Fuel P&ID (which I'd like to see), I don't like to take posts "off-line" where others can't see the information being discussed. Many previous posters have used one of many free Web hosting sites, like, to upload information/files, and then post the URL link to the location in a reply to the post. That way, everyone reading these posts (and a LOT of people follow these posts on can see and get the same information.

Dear CSA sir,

So, The main importance on FSR Split (Fuel Split) & DLN Split both is for only emission compliance? or any other purpose, If there are other reasons for both splitting, please kindly tell us the main points on above both types of splitting.

Thank you very much

2 out of 3 members thought this post was helpful...


It's not two different "splits"--it's two ways of describing the amount of fuel that is being directed to the different manifolds/nozzles, which means to the different areas of the combustor.

Have a reread of the replies above; it's not two different splits. There are still only four valves/manifolds and fuel nozzle sets. FSR split refers to the amount of current Fuel Stroke Reference that is going to each manifold/nozzles set. DLN split describes the percentage of total FSR that is going to each manifold/nozzle set.

Fuel is divided between various manifolds/nozzles sets in order to reduce the combustion gas temperature in the combustors in order to limit the formation of NOx emissions to protect the environment. By controlling the amount of fuel going to each are the amount of NOx emissions can be controlled (within a small range), and the dynamic pressure pulsations in the combustors can be limited/controlled as well. This type of combustion system is prone to develop high pressure pulsations of various types which can be very destructive to liners, nozzles and transition pieces and controlling how much fuel is delivered to nozzles in different areas of the combustors can help to reduce the pulsations and limit combustion hardware damage.

Early GE-design heavy duty gas turbines with conventional (diffusion flame) combustors had a single valve to control the amount of fuel going to the turbine fuel nozzles--and the control systems were designed to send a fuel flow-rate reference, expressed as a control valve position reference (where position was proportional to flow-rate) to control fuel flow-rate. Beginning with the Mark IV generation that reference was called FSR--Fuel Stroke Reference.

When they started developing DLN combustion systems where the total fuel flow-rate had to be divided into different manifolds/nozzle sets they just kept the single fuel reference, but calculated how much of that needed to go to which manifold/nozzle set.

Now it seems they've added a new way of measuring/monitoring fuel flow to various manifolds/nozzles with the DLN split measurement. It's just a different way of expressing the same thing--how much fuel is flowing to each manifold/nozzle set.

Hope this helps!

Dear CSA sir,

Thank you very much for give me a clear conception on this term. As a new guy, it was very essential for me to keep a clear idea on DLN split.

Have a nice day

Hello !

I enjoy reading this forum; and i thanks a lot CSA.

I have a question what about splitting & FSR DLN1?

i think the example that CSA is for DLN2.6

Thank you

Regardless of DLN type, there is only one FSR, and it's divided between fuel nozzles and/or combustion zones as needed.

By laplace1050 on 19 April, 2017 - 12:07 pm

Thanks for response CSA. maybe i am confusing, but there is no QUATERNARY for DLN1. so am asking if the splitting proportion are same for DLN1 & DLN2.6?

The splitting proportions are not the same for DLN-I and DLN-2.6. Some units which have Quaternary fuel don't use it. And even for units with DLN-I the splits aren't always the same. The splits for both type of DLN are adjusted during tuning to achieve the desired emissions.

FSR is the total amount of fuel as a percentage of the position of one valve (for non-DLN units) or two or more valves for units with either type of DLN. For DLN units the total FSR is split between however many valves are required for the current combustion mode. That's a little harder to understand when there are three or four valves (such as when IGCVs--Independent Gas Control Valves) but it's done by dividing (splitting) the fuel flow rates as necessary between the required valves to achieve the desired emissions.

Regardless of the number of valves. Would it surprise you to know that some Gas Fuel Modules used for DLN-I units have an extra, unused Gas Control Valve? That's because GE uses the same Gas Fuel Modules for both DLN-I and DLN-2.6. It's called standardization, and, yes, it's wasteful but it cuts down on design and manufacturing costs to use a common design for both types of DLN systems.

FSR is the total amount of fuel flow, based on valve position--which for the GE-design heavy duty gas turbine control system is proportional to stroke (position)--and which can be divided (split) between multiple valves and fuel manifolds/nozzles. By using FSR the same basic control (Droop or Isochronous Speed Control, and Exhaust Temperature Control) can be used for DLN and conventional, diffusion flame combustion systems.

Hope this helps.

By Laplace1050 on 21 April, 2017 - 2:43 am

>Hope this helps.

Thank you a lot Mr CSA for the answers, it help me a lot.