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I am new to DLN machines which has become the latest trend among companies due to environmental regulations. I would like to have the working or proven sequence of DLN1,2 & 2.6 for MKV and MKVI panels for GE frame5 or Frame6 machines from any plant in the world so that I could get an idea on how the sequence is differentiated between different DLN versions.

Any help on this from anyone would be highly appreciated.

Thanks is advance,

GE Frame 5 or Frame 6 machines only use DLN-I or DLN-I+. DLN-2.x is generally only used on F-class turbines (7F and 9F units). (Frame 7Es and Frame 9Es generally can be equipped only with DLN-I combustion systems; some 7EA units have had DLN-I+ combustors fitted to them.)

DLN is an evolving technology, and the sequencing used to control different types of valves and processes changes over time. The general principles are the same, but the exact sequences and instruments and components vary slightly as development continues and improves.

The major things one needs to know about DLN-I is that has two separate "zones" in the combustion chamber where combustion takes place: the Primary- and Secondary Combustion zones. Fuel is split ("staged") between the two zones in order to achieve the lowest emissions possible (in the combustion mode referred to as Premix Steady State).

In general, Premix Steady State can only occur during loaded operation, and *without* Inlet Bleed Heating (a very poor description for the function provided by the system) only above approximately 80% of rated load to 100% of rated load. With Inlet Bleed Heat, the unit can operate in Premix Steady State combustion mode as low as approximately 40% of rated load, but there is an efficiency penalty for this (slight, but should be noted).

During loading of DLN-I systems, the unit goes from flame in the Primary Combustion Zone only (Primary Combustion Mode,) to flame in both Primary- and Secondary Combustion Zones (known as Lean-Lean Combustion Mode), to flame only in the Secondary Combustion Zone with premixing occurring in the Primary Combustion Zone (Premix Steady State Combustion Mode).

The transition from Lean-Lean to Premix Steady State Combustion Mode actually consists of several intermediate steps as fuel to the Primary Combustion Zone is shut off (to extinguish the flame) and then re-introduced to the Primary Combustion Zone where it is premixed in a very lean air-fuel mixture before entering the Secondary Combustion Zone.

This particular transition, the Lean-Lean to Premix Steady State transfer, takes time and makes the use of turbines equipped with DLN-I combustion systems very poor units for use in Isochronous Speed Control (frequency control) applications. There are some "compromises" which can be made for Isochronous control, but maintaining emissions compliance *and* maintaining frequency in a wide load range are mutually exclusive requirements. (Trust me on this--I don't care what the salesmen say.)

DLN combustion systems require a lot of TLC (Tender, Loving Care). They must generally be "re-tuned" after any maintenance outage (combustion-, hot gas path- or major inspections) and this can be expensive and time-consuming. There are some ways to mitigate this requirement, but the tuning process is not very well documented anywhere. (I've been told that the Frame 6 Users' Group has a core of people who claim they can tune Frame 6 DLN-I combustion systems without GE's or any outside firm's assistance.)

It should also be noted that many owners have reported having to re-tune their DLN systems as ambient temperatures change (say from 35 deg C to -20 deg C). There have been some advances made by GE in improving the ability of the Speedtronic to respond to ambient temperature changes like this, but they aren't inexpensive.

Lastly, DLN usually only refers to natural gas fuels. Some mixed gas fuels (using refinery off-process gases) can be accommodated, but not always and sometimes only NOx can be guaranteed (meaning, no CO guarantee).

Turbines equipped with DLN combustors can burn liquid fuel (distillate) but not in "premix" mode and require water- or steam injection for emissions reduction while burning liquid fuel. This greatly complicates the piping and control systems, and the tuning of water- or steam injection systems can be difficult for many people.

I would suggest you talk to GE or one of the other companies supplying DLN combustion systems for GE heavy duty gas turbines. They have some papers and other documents which you would probably find very helpful.

Hope this helps--at least to get started!

One more thing: If you buy a DLN unit or convert a unit to DLN, do yourself a great big favor: buy the best, most reliable emissions monitoring system you possibly can and then invest in training on that system for two or three technicians. Failure to do so can be very, very costly. VERY costly. And in the end, a new system will eventually be sourced.

Many alleged emissions problems can be traced to problems with the emissions monitoring systems, their piping systems, and the care and maintenance of the the systems.

Steve Calvert

I have solve a High Flow Lockout issue for TVA. this is for a GE 7EA Combustion Turbine. When the turbine was switched from Natural Gas to Diesel the unit would produce a error. This was caused by air backing up from the small water injection check valves near the turbine. My company installed a customized check valve near the turbine eliminating this problem.

My question is what other GE Combustion Turbines use this water injection system.

Thanks for your help.

how can I find out the existing frame 6Bs with DLNI, and their contacts, is there a source for these data?

thank you

Bob Johnston

Do you have Transferless DLN1 or the older version with a Transfer valve I can send you a document on how both systems work. Post your Email
I don't quite understand the intent of the post...

There is a Frame 6(B) Users Group. Just use your preferred Internet search engine.

If you are trying to ask a question about a problem, try asking it here. If you're trying to promote (sell) something, well, there are lots of ways to do that. Advertising or presenting on/at the Frame 6B Users Group website and/or meetings.

But we don't know exactly what you are looking for; it's not clear from your post.