Asymmetric Combustor Control for Gas Turbine Emissions
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Solution Overview
Problem
Conventional industrial gas turbine engines face challenges in reducing carbon monoxide (CO) emissions during part load operations, especially below a certain threshold, and existing methods struggle to maintain emissions compliance as nitrous oxide (NOx) emission limits continue to decrease.
Innovation Solution
The implementation of an asymmetric combustion mode in a can annular industrial gas turbine engine, where some combustor cans operate in a warm mode and others in a hot mode, with a fuel distribution strategy that adjusts the fuel split between diffusion and premix pilot burners to optimize flame stability and emissions reduction, while maintaining the same total fuel flow across all cans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional uniform combustion mode is used during part load operations, then emissions requirements can be met above a certain threshold, but emissions compliance becomes difficult or impossible below the threshold
Solution Approach 1:
The combustor array is segmented into multiple individual combustor cans, each capable of independent operation. During part load, only a subset of cans is activated while others remain inactive, allowing the system to maintain emissions compliance across a wider operational range by adjusting the number of active cans rather than relying on uniform combustion across all cans.
Solution Approach 2:
Different combustor cans are operated under different conditions - some cans run at higher fuel flow rates while others operate at lower rates or remain offline. This local differentiation allows the system to optimize emissions performance in active cans while maintaining overall power output, enabling compliance below traditional threshold limits.
2Reliability
If fuel flow to pilot burners is increased to maintain flame stability, then combustion reliability improves, but CO emissions increase
Solution Approach 1:
The fuel delivery system is segmented to provide independent fuel control to each combustor can and to separate control of pilot burners versus main burners within each can. This allows pilot burners to operate at optimized fuel rates for stability while main burners provide the bulk of fuel delivery, reducing overall emissions.
Solution Approach 2:
The system dynamically adjusts fuel flow parameters to pilot burners based on operating conditions. During part load operations, pilot burner fuel flow is optimized to maintain just sufficient flame stability rather than running at full capacity, thereby reducing CO emissions while preserving combustion reliability.
3Object-generated harmful factors
If asymmetric combustion mode is implemented to reduce total CO emissions, then emissions compliance improves, but combustion control complexity increases
Solution Approach 1:
The combustor array is divided into independently controllable segments (cans), each with its own fuel control system. This segmentation enables asymmetric operation where different cans run at different fuel rates or different numbers of cans are activated, providing flexible emissions control through simple on/off or rate-adjustment logic rather than complex centralized control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces total CO emissions by decreasing emissions from hot cans while increasing emissions from warm cans, allowing the engine to operate at lower load levels while maintaining emissions compliance, and stabilizes the transition between combustion modes to prevent instabilities.
Implementation Method 1
each can comprising burner stages and a pilot burner arrangement comprising a premix pilot burner and a diffusion pilot burner
Implementation Method 2
fuel to the A, B, and C stages is stopped; establishing an increased rate of fuel flow to the diffusion pilot burner of the warm can
Data Source
AI summary
A method, including: operating an industrial gas turbine engine having a plurality of combustor cans arranged in an annular array, each can having burner stages and a pilot burner arrangement having a premix pilot burner and a diffusion pilot burner; operating in asymmetric combustion, wherein at least one can is a warm can where respective burners stages are off and remaining cans operate as hot cans where respective burner stages are on; and while maintaining a constant rate of fuel flow to the pilot burner arrangement of the warm can, changing fuel fractions within the pilot burner arrangement of the warm can.