Gas Turbine Controller Synchronizing Mass Flows for Combustion Stability
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Solution Overview
Problem
Modern gas turbines face challenges in maintaining combustion stability during rapid transient operations due to the narrow flammability range of lean premix flames, which can lead to instability and emissions issues, especially with differing dynamics in fuel, water/steam, and air supply systems.
Innovation Solution
A method and control system that dynamically compensates and accelerates command signals for fuel, water/steam, and air mass flows to synchronize their changes at the combustor inlet, using transfer functions to match the dynamics of each supply system, ensuring the fuel-to-air ratio remains within combustible limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean premix combustion is used to reduce emissions, then NOx emissions are reduced, but combustion stability deteriorates due to narrow flammability range
Solution Approach 1:
The control system performs preliminary synchronization of fuel, water/steam, and air mass flows before combustion occurs. By pre-coordinating the timing and rate of mass flow changes through dynamic compensation, the system ensures that all components reach the combustor simultaneously, maintaining stable combustion conditions even during rapid transients while preserving the emission benefits of lean premix combustion.
2Adaptability or versatility
If rapid transient operation is implemented to improve grid frequency response, then operational flexibility is improved, but combustion stability deteriorates due to exceeded flammability limits
Solution Approach 1:
The control system implements dynamic compensation that adapts to changing operating conditions in real-time. The controller continuously adjusts the coordination of mass flow commands based on the current state of the gas turbine, allowing rapid transient operations to be performed while maintaining combustion stability through dynamic adjustment of fuel, water/steam, and air supply rates.
Solution Approach 2:
The system uses feedback from measured operating conditions to continuously adjust mass flow commands. The controller receives feedback on the actual state of the gas turbine and uses this information to refine the coordination of fuel, water/steam, and air supplies, ensuring that combustion remains stable even during rapid transient operations required for grid frequency support.
3Device complexity
If direct command to actuators and control valves is used for simple control, then control system complexity is reduced, but mass flow synchronization deteriorates due to different system dynamics
Solution Approach 1:
The control system introduces an intermediary dynamic compensation layer between the controller and the actuators. This intermediary component processes the mass flow commands and applies appropriate compensation to account for the different dynamics of fuel, water/steam, and air supply systems. While this adds some complexity, it enables precise synchronization of mass flows without requiring complex redesign of the actuators or control valves themselves.
4Speed
If faster transient changes are implemented to improve response speed, then grid frequency support capability is improved, but flame stability deteriorates due to narrow flammability range
Solution Approach 1:
The control system performs preliminary coordination of all mass flow changes before they are executed. By pre-synchronizing the fuel, water/steam, and air supplies and ensuring they will reach the combustor simultaneously, the system enables faster transient changes to be made without compromising flame stability. The narrow flammability range is respected because the coordinated approach ensures all components arrive together within safe combustion limits.
Data Source
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AI summary
Method for transient operating of a gas turbine (1) and controller system (30) configured to carry out such a method as well as a gas turbine (1) comprising such a control system (30), where the controller (10) determines command values for an inlet air mass flow, fuel mass flow, and if applicable for a water or steam mass flow. In order to allow fast transient operation with a stable premix flame at least one command value is dynamically compensated in order to compensate for the different system dynamics of the supply systems in order to synchronize the resulting changes in fuel, water, steam, and/ or combustion air mass flows, which reach the combustor (3), so that the fuel to air ratio stays within the combustible limit.