Method and system for detection of gas turbine combustion blowouts utilizing fuel normalized power response
A method and controller for identifying lean blowout conditions in a Dry Low NO x (DLN) combustor during a premix mode. An effective approach to quickly and reliably identify a blowout during operation in the premix mode is by the effect on fuel normalized power (FNP). FNP is a useful signal, in that a power reduction from a blowout may be distinguished much slower changes in power resulting from global fuel demand (changing load request). A difference between the FNP and a filtered FNP parameter may be compared against a predetermined threshold. If the difference exceeds the threshold, a lean blowout is identified and a signal may be transmitted to the turbine controller to reposition combustor operation away from blowout conditions.
1. A method for detecting a lean blowout in a combustion can of a gas turbine engine, the method comprising:
detecting a shift in generated power output that does not result from a changing fuel demand;
determining that the shift in generated power output results from a lean blowout in a combustor;
transmitting a signal to a turbine controller to initiate action to increase margin to lean blowout in all combustors; and
implementing a response increasing margin to lean blowout for all combustors; wherein the step of detecting a shift in generated power output that does not result from a changing fuel demand comprising calculating Fuel Normalized Power (FNP) according to: where Power is represented in Driven Megawatts at the output of the generator; Fuelref represents Total Fuel Reference demand supplied to the machine; and Fuelref FSNL represents Fuel Reference required at Full Speed No Load; and wherein the step of detecting a shift in generated power output that does not result from a changing fuel demand further comprising: tracking the calculated FNP; applying a filter to the calculated FNP to establish a filtered FNP; tracking the filtered FNP; and determining a difference between the filtered FNP and the calculated FNP; and wherein the step of determining that the shift in generated power output results from a lean blowout in a combustor comprising: determining if the difference between the filtered FNP and the calculated FNP exceeds a predetermined threshold.
2. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 1 , the step of calculating FNP further comprising:
monitoring FNP when the turbine generator breaker is closed.
3. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 1 , the step of detecting a shift in generated power output that does not result from a changing fuel demand comprising:
setting the Fuelref FSNL to the value of the Fuelref when the generator load breaker is closed.
4. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 1 , the step of applying a filter to the FNP comprising:
applying a lag filter to the FNP.
5. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 4 , the step of applying a lag filter to the FNP comprising:
applying a lag filter with a time constant of approximately 5 seconds.
6. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 1 , wherein a value for the predetermined threshold is less than a difference between the filtered FNP and the calculated FNP caused by blowout in at least one can during operation in the premixed mode and that is greater than a difference between the filtered FNP and the calculated FNP resulting from routine operational transients.
7. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 6 , the step of transmitting a signal to a turbine controller to initiate action to increase margin to lean blowout in all combustors comprising:
transmitting a signal to the turbine controller when the difference between the filtered FNP and the calculated FNP exceeds a predetermined threshold.
8. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 6 , the step of transmitting a signal to a turbine controller to initiate action to increase margin to lean blowout in all combustors further comprising:
locking in the signal for a predetermined time period to prevent multiple triggering signals from reaching the turbine controller.
9. The method for detecting a lean blowout in one combustion can of a gas turbine engine according to claim 1 , the step of implementing a response increasing margin to lean blowout for all combustors comprising:
implementing a step change in an emissions model algorithm gain.