We are using GE's 7FB model, and DCS is using MARK-VIe.

As a new engineer at a power plant, I've always had a lot of questions, but I couldn't solve them because there were a lot of restrictions. I'd really appreciate any answers to these questions.

1. Situation
- IGV opening Angle at Startup: 29° → PartSpeed (TNHCOR) 74% : 23° → PartSpeed 85% 41°
- 1st attempt: TNHA <= 0.1 or less at 3120 rpm for more than 60 seconds and shut down to L60PSNA. (Lopy attached)
- 2nd attempt changed pick-up time to 60 → 120 seconds, but shut down with the same alarm at 3097 rpm.
- 3rd attempt: successfully sealed after changing the constant to 23° → 27° when IGV Part Speed (TNHCOR) 74% is IGV opening.

2. Reason for changing IGV opening to 29 ⁰ → 23° at partial load of manoeuvre - The reason why IGV operates at minimum opening is because of maintaining flame stability and minimal exhaust emissions. Below is the reason we estimate.
1) Lowest angle to prevent surging
2) Exhaust temperature control
- It is said that HRSG thermal efficiency is increased by adjusting from partial load to high exhaust temperature setting, and I wonder if the partial load has a specific speed section.
I think the increase in HRSG thermal efficiency is the decisive reason for the change of IGV opening 29° → 23°.

2. PartSpeed(TNHCOR)85% cause the IGV opening to 41°, just as the opening to 23° is answered during initial gibbering, I would like to ask for information on what factor the opening is controlled by as the lopy block related to IGV opening is locked.

3. Rotating Stall Region
- I would like to ask if the training material affects the range of the Rotating Stall Region and the setting of the IGV opening. - In addition, I would like to ask if the cause of Bleed Valve#3.4 closing at 69% to 74% of PartSpeed is also the cause of surging.

4. Fuel Amount Correction Constant (CQTC) Logic
- IGCC CQTC Torie has only CTIM, but if the fuel gas temperature is not corrected, I would like to ask if there is a possibility that it will be shut down with L60PSNA due to the failure to control the fuel air flow rate when the exhaust gas temperature is high during the TRIP and restart as this case.

5. For the change of purge time - Currently, it re-enters to restart Crank Mode after Shutdown and purges for 15 minutes, but after 15 minutes, there is a temperature limit and you have to wait until the cold air rod. I don't think there will be any problem even if you raise it with a hot air rod during sewing, so I would like to ask if it is possible to change the purge time to 15 minutes → 10 minutes, and if not, whether the factors should be considered.

 

@vitamin D,

SOO mny questions.

I was a technician--not a designer.

Axial compressors are unique machines, with unique characteristics.

GE-design Frame 7FB machines are increasingly complicated machines.

Without being able to see the application code running in the Mark* VIe and the Control Specification for the machine and without knowing if the application running in the Mark* VIe uses ARES (Adaptive Real-time Engine Simulation, or also know as MBC--Model-Based Control), and finally without knowing what alarms (Process AND Diagnostic) are active when the scenarios you are trying to describe I can't be of help.

I'm a simple person, who worked primarily on GE-design heavy-duty B/E gas turbines (mostly generator drive applications) and in my later career I was roped into working on DLN combustions systems (something I wasn't really interested in doing but the money was too good to refuse) and F-class machines.

GE considers nearly everything about their machines these days to be company proprietary information. They write very little about the control schemes and their operation and tuning. They have remote monitoring and diagnostic centers which collect HUGE amounts of running data on most of the F- and H-class machines (including all the sub A- and B perverions) which they use to periodically adjust operating parameters and sequences. Without any fanfare or documentation, or very little documentation if any.

The FB probably also has multiple stages of variable axial compressor stator vanes, which increases the complexity of the axial compressor by at least one order of magnitude, if not two or more,--and good luck getting information from GE about that compressor. They are very proud of those axial compressors.

This is life in the world today. It's the same for other heavy duty gas turbine manufacturers, even worse for one particular manufacturer who segregates all work on their turbines into very small, niche tasks and does not cross-train their field service personnel because they don't want company proprietary information to be leaked to anyone, anywhere.

If you work on a site with an FB machine, then you probably have a CSA (Contractual Services Agreement) with GE and they get paid handsomely for supporting the operation of the machine and taking responsibility for maintenance and repair operations. This also allows site personnel to ask questions of their engineering staff--and that's what you should do with your questions. JUST BE PREPARED TO PROVIDE A LOT OF INFORMATION AND OPERATIONAL DATA (even though they have a lot of that data and information already through their remote monitoring and diagnostic center).

This is all I can offer you. I will tell you that the operating parameters they determine for the machine are the proper and correct parameters for that machine. It's rare that the parameters are found to be wrong. (It's not uncommon for operations to change over time, sometimes very soon after the site is commissioned, that require changes--but that requires engineering and knowledge I didn't have.) And, I will also posit that there is MUCH MORE to your questions and what you would do with the information than you are telling, or would tell in a public forum.

I probably suffer from vitamin D deficiency--having spent man-years of my life working in Control Cabs, Control Compartments and PEECCs (Power, Electrical and Electronic Control Compartments) which have NO windows, huddled in front of HMI monitors fixing HMI display problems while commissioning the machines. At the end of my career, if I had a question I would put together all my data and describe how I think the machine should be operating, detail how it is operating and ask if my presumptions are correct or not. I learned a lot from those exchanges, but at times it was like pulling fingernails with a pair of pliers (painful). But, I wasn't designing machines--I was only commissioning them. My job was only to make them START and synchronize and run up to Base Load without any alarms then unload and go on Cooldown without any alarms, ensure the protections in the Mark* worked properly, and turn over a smooth running machine based on the control schemes and operating parameters provided with the machine. Full stop. Period. That was my job, and I derived a lot of personal satisfaction from doing my job. And I was paid pretty well for that, though I was away from home a lot. But, I wasn't interested in designing machines or circumventing any normal operations.

Best of luck with your questions.