GE Gas Turbine:

1- Without IBH: Fuel Gas pressure required is within 21/24 barg at Y filter to allow transfer from LEAN-LEAN to PREMIX during star-up or load changes

2-With IBH: Fuel Gas pressure required is within 18/24 barg at Y filter to allow transfer from LEAN-LEAN to PREMIX during star-up or load changes

Would someone explain why does the transfer require higher pressure?

 

Mustapha,

If I understand this post and summary correctly, I think you have it slightly wrong.

When IBH is not enabled, the gas fuel supply pressure has to be higher because the Lean-Lean to Premix transfer takes place at a higher load/fuel flow-rate, so the extra supply pressure is necessary to ensure there will be enough fuel flow to get all the fuel flowing through the secondary fuel nozzles (and transfer passages/nozzles, if so equipped).

When IBH is enabled, the Lean-Lean to Premix transfer will occur at a much lower load, which makes the necessity of ensuring sufficient flow through the secondary (and transfer) nozzles/passages not so important because the fuel flow-rate will be lower at the lower transfer point.

 

Dear Sir,
We have a Fr-5 Gas Turbine with DLN1 combustion system .This is with Splitter valve .May i know the DLN Modes , load and TTRF value approx for various DLN mode changeover with and without IBH .

Matter a bit urgent please

 

@1895737,

These are typical values (from memory, as I don't have a CSPEC to look at at the present moment), but the combustion mode transfer points are usually the same with or without IBH active. The transfer from Primary combustion mode to Lean-Lean usually occurs at the TTRF value of approximately 1500 deg F, and the transfer from Lean-Lean to Premix combustion mode usually occurs at somewhere around 1950-1975 deg F.

When IBH is NOT active, the transfer from Primary to Lean-Lean will occur at around 50% of rated load and the transfer from Lean-Lean to Premix will occur at around 80% of rated load (these loads can be greatly affected by high ambient temperatures as well as low ambient temperatures).

When IBH IS active, the transfer from Primary to Lean-Lean will occur at around 40% of rated load, and the transfer from Lean-Lean to Premix will occur at around 60-70% of rated load (meaning that the unit gets into Premix combustion mode sooner when loading the machine, and it will stay in Premix longer when unloading).

But, the transfer points (TTRF temperatures) usually remain the same regardless of whether IBH is active or not; it's just the loads at which the transfers will occur differ when IBH is or isn't active.

Finally, are you having problems AFTER a recent maintenance outage?

 

Thank u very much

 

I should tell you that if you are commissioning a machine (a new machine?) a CSPEC should have been provided with the equipment.

Further, as GE "splinters" into more profit centers (Firenze and Belfort in addition to Greenville) long-standing control philosophies are being changed which could mean that the numbers above--which worked for decades--are no longer valid. And that includes logic/sequencing/application code is changing as well, especially as new control schemes are being developed by the different profit centers. DLN-I, long considered a "mature" technology is also undergoing some changes.

The only thing that really matters is how that machine is programmed. It can't really be compared to any other machine--except one of a similar recent vintage from the same profit center and with the same fuel control scheme and combustion hardware. I doubt (but I have been wrong before!) the transfer points will have changed very much, but its possible since the focus now is primarily on getting into Premix combustion mode as soon as possible and remaining in Premix as long as possible as the machine is being unloaded. It's even possible that there are changes to the IBH (Inlet Bleed Heat scheme and components which could affect the transfer points).

If you are working with an overall plant commissioning team to understand how to program the boiler (I presume there is a boiler or heat recovery steam generator (HRSG) on the exhaust of this machine) then you really want to be using the CSPEC for that machine, or looking at the application code and Control Constants (operating parameters) in the Mark* turbine control system (probably a Mark* VIe).

 

Sure . I will check .Thank you very much .