Please, who can tell me what DLN-1 and DLN-2 mean in gas turbines.

 

Drop me an Email to [email protected] (miss the nospam)I have some GE documents on DLN I & II I can send you, it would be easier than trying to explain.

 

Dry Low NOx 1 and 2... term to determine the amount of Nox emmision from gas turbines... which can be controlled by injecting or spraying water into the inlet path of suction air, ie low pressure compressor side of gas turbine...

Low nox is explained, when temperature of inlet compressed air is low,,, more volume of air can be compressed and gas can be burned efficiently to reduce the amount of nox... in the exhaust...

 

DLN, or Dry Low NOx, is a means of limiting NOx emissions without using a diluent like water or steam. A Dry Low NOx combustor on a GE-design heavy-duty gas turbine is a combustor which will produce an extremely lean fuel-air mixture which will result in lower hot gas temperatures which will result in reduced NOx formation.

There are several versions of Dry Low NOx combustion systems: DLN-I, the first; DLN-2, the second; and DLN-2.6. There is even a DLN-2+ and DLN-2.0e and a DLN-2.6+ and, I believe and DLN-2.6e.

DLN-I and DLN-2 are fairly similar in that they basically have a "primary" and a "secondary" combustion zone. By controlling the amount of fuel in each zone (the "split") and whether or not there is flame in the zone when fuel is present the hot gas temperature can be reduced.

This is a pretty complicated system of gas control valves--and it's all based on empirical data obtained from combustion laboratory testing and field testing. Why? Because the "firing temperature" inside the combustion can (not to be comfused with the "firing temperature" which is the temperature at the trailing edge of the first stage turbine nozzles) is estimated during turbine operation. In other words, it's *not* measured. There are no T/Cs, pyrometers, laser heat detectors--nothing--to tell the control system the actual "firing" temperature.

The control system calculates a Combustion Temperature Reference: TTRF1. But it's a calculated value, and it's sole purpose is to serve as a "switch" for changing combustion modes. When the Combustion Reference Temperature reaches preset limits during loading of the unit, the combustion mode will change. When the Combustion Reference Temperature reaches preset limits during unloading of the unit, the combustion mode will change.

Why is this necessary? Because, essentially, other than the IGVs there is no way control the air flow through the turbine--and they are a "crude" method of controlling air flow (which, again, is not monitored on most machines). There is a lot of empirical data that says that when the IGVs are a certain angle and the fuel flow is approximately thus-and-such that the fuel-air mixture is a particular value. And that can also be equated to a Combustion Reference Temperature. So, when the fuel-air mixture reaches a certain point, the combustion modes are changed.

The IGVs can't be used like the butterfly in a carburetor or a fuel injection manifold. The axial compressor is a cruel beast in that it can surge or stall if certain conditions are inadvertently achieved. If the IGVs could be opened and closed without adversely affecting the axial compressor operating limits the DLN combustion system would be a much simpler system. But, everything in life isn't easy, is it?

It's really very difficult to explain with pictures. Contact Bob Johnston for the GE brochures which should be a little more help. And, write back if you have more questions.

 

Nanda, It's Dry Low Nox he is asking about mate, not wet nox, just in case anyone gets confused.

 

yes you r correct... if you need any documentation on how to control emission on gasturbines... i have list of docs.