Gas Turbine Fuel Demand Biasing for Combustion Efficiency
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Solution Overview
Problem
Traditional gas turbine control systems assume constant combustor efficiency across different operating modes, leading to issues such as failed mode transfers and oscillations in fuel control due to rapid changes in combustion efficiency during transient operations, particularly at low-load points.
Innovation Solution
A method and system that compensate for combustion efficiency variations by biasing the fuel demand signal using a calculated bias signal (1/η-1)*fuel demand, where η is the combustion efficiency, to maintain stable operation during mode transitions, thereby avoiding undesirable traits like high combustion liner temperatures and visible emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional gas turbine control systems assume constant combustor efficiency across different operating modes, then the control system is simple to implement, but it causes failed mode transfers and oscillations in fuel control during transient operations
Solution Approach 1:
The control system dynamically adjusts the fuel demand signal based on real-time combustion efficiency variations during mode transfers. The system transitions from assuming constant efficiency to actively compensating for efficiency changes by modifying the fuel demand signal using the compensation factor (1/η-1), where η represents combustion efficiency. This dynamic adjustment prevents failed mode transfers and fuel control oscillations while maintaining manageable system complexity through algorithmic compensation rather than hardware complexity.
2Power
If gas turbines operate at higher temperatures during mode transfers to maintain power output, then power output is maintained, but it increases the risk of lean blowouts and excessive emissions
Solution Approach 1:
The system changes the fuel demand parameter by applying a compensation factor (1/η-1) to the fuel demand signal based on combustion efficiency variations. This parameter modification allows the turbine to operate at lower temperatures during mode transfers while maintaining adequate power output, thereby reducing emissions and lean blowout risk without sacrificing power generation capability.
3Ease of operation
If combustion efficiency is not compensated during mode transfers, then the fuel control system is simple to operate, but it causes oscillations in fuel control and failed gaseous mode transfers
Solution Approach 1:
The control system implements feedback by continuously monitoring combustion efficiency and using this information to adjust the fuel demand signal. The compensation factor (1/η-1) is calculated based on measured or estimated combustion efficiency η, and this feedback loop ensures stable mode transfers between gaseous combustion modes while maintaining ease of operation through automated compensation rather than manual intervention.
Data Source
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AI summary
Compensation is provided for a fuel demand signal of a gas turbine controller 110 during transition between operating modes. The compensation adjusts fuel demand to account for combustion efficiency differences between the starting and ending operating mode that otherwise can lead to severe swings in combustion reference temperature and lean blowout.