Fuel Normalized Power Detection for Gas Turbine Lean Blowouts
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Solution Overview
Problem
Conventional gas turbine control systems, particularly those with Dry Low NOx (DLN) combustors, face challenges in detecting lean blowouts promptly and preventing subsequent combustion dynamics or flame loss, which can lead to high emissions, costly downtime, and physical damage due to the tight margins in ultra-low emissions operations.
Innovation Solution
A method and system that utilize Fuel Normalized Power (FNP) to detect shifts in power output not caused by changing fuel demand, triggering a response to increase margins against lean blowouts by adjusting the emissions control model, incorporating a threshold algorithm and first-order lag filtering to differentiate between blowout events and normal transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control systems rely solely on turbine exhaust temperature and compressor pressure ratio to determine operating conditions, then the control system is simple to implement, but the system cannot promptly detect lean blowouts and prevent subsequent combustion dynamics
Solution Approach 1:
The controller performs multiple functions using existing sensors: it continues to monitor turbine exhaust temperature and compressor pressure ratio for normal operation while simultaneously calculating fuel-normalized power and detecting lean blowout conditions. This multi-functionality improves detection reliability without adding dedicated hardware sensors.
Solution Approach 2:
The patent introduces fuel-normalized power as an intermediary parameter that mediates between existing measurements (turbine exhaust temperature, compressor pressure ratio, fuel flow rate) and the target detection goal (lean blowout conditions). This intermediary enables prompt detection while utilizing the existing control system infrastructure.
2Object-generated harmful factors
If the gas turbine operates at very lean fuel/air ratios to maintain low NOx emissions, then emissions are reduced, but the system operates closer to the lean blowout boundary increasing the risk of flame loss
Solution Approach 1:
The system continuously monitors fuel-normalized power and provides feedback when the turbine operates close to the lean blowout boundary. Upon detecting a lean blowout condition, the controller sends a signal to increase the fuel/air ratio, creating a feedback loop that maintains combustion stability while allowing operation at lean conditions for reduced NOx emissions.
Solution Approach 2:
The system performs preliminary detection of lean blowout conditions by monitoring fuel-normalized power before complete flame loss occurs. This preliminary action allows the controller to preemptively adjust the fuel/air ratio to prevent flame loss, maintaining combustion stability while preserving the ability to operate at lean conditions for emissions control.
3Object-generated harmful factors
If transient under-fire events are allowed to occur in advanced ultra low emissions combustion systems, then the system can maintain tight emission margins, but combustion dynamics or flame loss can result causing high emissions and potential damage
Solution Approach 1:
The system applies preliminary anti-action by detecting lean blowout conditions through fuel-normalized power monitoring before combustion dynamics or flame loss occurs. The controller preemptively signals to increase the fuel/air ratio, counteracting the tendency toward flame loss and preventing the harmful effects of combustion dynamics while maintaining tight emission margins during normal operation.
Data Source
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AI summary
A method and controller for identifying lean blowout conditions in a Dry Low NOx (DLN) combustor of a gas turbine 580 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) 515. FNP 515 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 520 between the calculated FNP 515 and a filtered FNP parameter 518 may be compared against a predetermined threshold 521. If the difference520 exceeds the predetermined threshold 521, a lean blowout is identified and a signal 525 may be transmitted to the turbine controls 575 to reposition combustor operation away from blowout conditions.