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!