I am working as Tr. Engr. on a power plant based on GE 9HA gas turbine
Can any one explain about the DLN 2.6+ combustion modes e.g. 6.2A, 3.3, 3.1, MECL 6.2A.
The HA technology is pretty new and I haven't seen much in the way of documentation about it's operation and operating modes.
I would suggest that GE provided some training at the plant, and there are training manuals from that instruction around that you could access for detailed information.
Also, have a look at the Operations & Service Manuals provided with the unit(s) for information. I have been told that GE is now providing the manuals on CD/DVD (or flash drive) rather than printed copies, so it may take some asking around to get the access you need on a computer somewhere. Many plants these days have "libraries" and some have very strict systems in place for drawings and literature and manuals--but it is, or should be, available to anyone working at the plant for use in understanding, operating, maintaining and trouble-shooting.
Best of luck in your endeavours!
In addition what CSA said about looking into O&M Manuals; certainly you'll find what you need exactly, cause each machine has their own specifications.
While I can give you some specifications for DLB2.6+ on 9FB:
Look in general combustion mode is referring which VGC (1/2/3/4) is in use, of course which is not in use it must be in purge mode. Also its known that as permissive to pass a mode to another is the combustion reference temperature. for example to pass to the mode B, premix mode TTRF1 must be greater than 2250°F, of course with others permissives.
We can say that finding "D" in mode name exp: D5 (P),1D (L Lean-Lean), 3D (J 3D backup), 6D (A) means we're in diffusion mode which means that at least D5 or VGC-1 is in use.
Whenever VGC-1 is closing we get out from diffusion mode, and we get into premix mode. For example: mode (3 or N), (6.2 or C), (6.3 or B).
We have also some exceptional mode like (I PM1 FSNL) or Load rejection mode.
Mode PPM Piloted premix mode where all gas valves are in use and no purging at all. this could happen in some conditions as well as purge fault, condensate drain system fault etc. you can find in more details looking into the logic. also, take exp a signal L3FXN (permissive for Mode N (3), and look backward.
Hope this help.