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Combustion Dynamics
Gas turbine consequences if wobbe index is too high and too low?

If wobbe index is too high that very combustion dynamic at fullspeed no load, why?

If wobbe index is too low that very combustion dynamic at base load, why?

2 out of 2 members thought this post was helpful...

I don't know which turbines you are using but I can talk GE industrial machines, but I reckon it is pretty much the same for all.

The fuel gas regulating system is normally set up according to a gas specification supplied by the customer at the time of ordering. This system will accept small variations in the specification but large changes can affect the quality of control. Low wobbe can mean that the machine cannot get enough fuel at Base Load as the control valve is fully open. high wobbe can be more dangerous, particularly at Start-up which is an open loop system with preset fuel valve control.

Things can be done with latest controls to correct these problems, but need a wobbe analyzer to feed back to and correct the control system.
Write back and tell us which turbines you have, and what kind of wobbe changes you are looking at and we can give you a better answer.

1 out of 1 members thought this post was helpful...

Thank you so much Mr.glenmorangie.

I operating GE gas turbine 6B. Now flue gas wobbe index is 1220-1290 BTU/scf. Next year gas wobbe index will change to 1220-1340 BTU/scf, but gas nozzle can support 1210-1291 BTU/scf. I would like to know what effect if wobbe index higher or lower gas nozzle specification?

1 out of 1 members thought this post was helpful...

Your main problem will be at light off, when you have the highest wobbe index. Remember this is a fixed GCV stroke setpoint. It would be worth contacting GE for some advice, maybe you can get away with it as you are only slightly above the maximum index number or maybe you can change the gas tips or modify the startup parameters.