Dears,

We have a big problem in our gas turbine power plants which is consists of 6* Siemens V94.2.3 gas turbine (Silo type). The problem is Humming phenomena or combustion chamber pressure oscillation which is observed in diffusion mode (only with Natural Gas) in partial load (about 50 to 70 MW). then load is locked or decreased fast (relative to oscillation amplitude)to control the oscillation.

The pressure oscillation is measured by one accelerometer installed on top of each CC.

Does anyone have an experience like this or any way to omit the problem?

 

hello,

the humming phenomena can be a result of different causes: ambient temperature, gas pressure and temperature, burner issue, combustion chamber geometry...

1- as you state you are operating 6 GT's. doe's the humming appear in the 6 or in one?

2- have you perform any maintenance?

3- is there any gas pressure or temperature change?

4- which control system is installed?

regards
Ahmed

 

As u say, this problem occurs in diffusion mode, what about exhaust temperature thermocouples? how load got restriction? do u have acceleration limits or lock average appears on exhaust thermocouples? humming problem may be due to clogging of diffusion nozzles, what about flame intensity?

do u have T 3000 control system?

 

Hello GTman, thanks for your reply,

load automatically is restricted and then decreased by control/protection system (Siemens) when the acceleration of each two C.C. reaches to a certain value which is equivalent to a combustion pressure oscillation amplitude (e.g. 30 mbar). All burners and gas lines for diffusion system have been checked. no problem was observed.
flame intensity monitors by two flame detectors and no intensity change could be observable because of high frequency of oscillation.

I'm not familiar with T 3000 control system. could you explain me more about it, please?

 

Hi Ahmed,
thanks a lot for replying me

As u notice, the humming can be consequence of many factors such as ambient or gas temp. change but only 1 or 2 certain GTs have this problem in all seasons and in other we didn't experience any problem.

we have had this problem from commissioning of GT up to now.

GT protection/control system has been produced by Siemens named Teleperm xp S7.

I am now looking for a person who experience this problem and a way to remedy it. adding excess air or reducing of it couldn't help us to escape from this problem.

best regards.
Mohammad