Gas Turbine Combustor Control for Load Dump Stability
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Solution Overview
Problem
Gas turbines face challenges in maintaining combustion stability and reducing NOx emissions during load dump transitions, where sudden changes in fuel flow rates can lead to increased rotating speeds and high NOx emissions in full-speed no-load operations.
Innovation Solution
A control apparatus for a gas turbine combustor that includes detectors, recorders, and a fuel control unit to switch between diffusion and premix combustion modes based on rotating speed changes, ensuring stable combustion and reducing NOx emissions by adjusting fuel flow rates between diffusion and premix combustion burners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the fuel flow rate is reduced to suppress rotating speed increase during load dump, then the combustion stability deteriorates, but the rotating speed control is improved
Solution Approach 1:
The system dynamically switches between diffusion combustion and premix combustion modes based on real-time rotating speed conditions. During load dump, when rotating speed exceeds a threshold, the system transitions to diffusion combustion mode to maintain stability. When rotating speed is suppressed below the threshold, it switches back to premix combustion mode to reduce NOx emissions, thus adapting combustion characteristics to varying operational conditions.
Solution Approach 2:
The invention changes the combustion mode parameter (diffusion vs. premix) based on rotating speed conditions. By monitoring rotating speed and switching between different combustion modes, the system adjusts the fuel-air mixing ratio and combustion characteristics to simultaneously achieve stable combustion and control rotating speed during load dump events.
2Stability of the object's composition
If diffusion combustion is used to ensure high combustion stability, then the combustion stability is improved, but the NOx emission increases
Solution Approach 1:
The system dynamically switches between diffusion combustion and premix combustion modes based on real-time rotating speed conditions. During load dump, when rotating speed exceeds a threshold, the system transitions to diffusion combustion mode to maintain stability. When rotating speed is suppressed below the threshold, it switches back to premix combustion mode to reduce NOx emissions, thus adapting combustion characteristics to varying operational conditions.
Solution Approach 2:
The system periodically switches between diffusion and premix combustion modes based on rotating speed thresholds. This periodic switching allows the system to utilize the advantages of both combustion modes: diffusion combustion for stability during high-speed conditions and premix combustion for lower NOx emissions during controlled conditions.
3Object-generated harmful factors
If premix combustion is used to reduce NOx emission, then the NOx emission is reduced, but the combustion stability deteriorates
Solution Approach 1:
The system dynamically switches between diffusion combustion and premix combustion modes based on real-time rotating speed conditions. During load dump, when rotating speed exceeds a threshold, the system transitions to diffusion combustion mode to maintain stability. When rotating speed is suppressed below the threshold, it switches back to premix combustion mode to reduce NOx emissions, thus adapting combustion characteristics to varying operational conditions.
4Speed
If the fuel flow rate is controlled to switch to independent diffusion combustion during load dump, then the rotating speed increase is suppressed, but the NOx emission increases during full speed no-load operation
Solution Approach 1:
The system dynamically switches between diffusion combustion and premix combustion modes based on real-time rotating speed conditions. During load dump, when rotating speed exceeds a threshold, the system transitions to diffusion combustion mode to maintain stability. When rotating speed is suppressed below the threshold, it switches back to premix combustion mode to reduce NOx emissions, thus adapting combustion characteristics to varying operational conditions.
Solution Approach 2:
The system uses feedback from rotating speed monitoring to automatically adjust combustion mode. When rotating speed exceeds a predetermined threshold during load dump, the system detects this condition and switches to diffusion combustion mode. After suppressing rotating speed increase, when the threshold is no longer exceeded, it switches back to premix combustion mode to minimize NOx emissions during the prolonged full-speed no-load operation.
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
The solution ensures immediate combustion stability and reduces NOx emissions during full-speed no-load operations by promptly switching between combustion modes, thereby preventing compressor and turbine damage and minimizing metal temperature rises in burners.
Implementation Method 1
a detector for detecting a rotating speed of the gas turbine
Implementation Method 2
an arithmetic unit for calculating a change with time of the rotating speed from information of the recorder
Implementation Method 3
the fuel control unit, upon receipt of a signal from the arithmetic unit, for controlling fuel flow rates to be fed to the diffusion combustion burner and the premix combustion burner
Implementation Method 4
The diffusion combustor is a system for separately feeding and burning fuel and air in a combustion chamber
Implementation Method 5
a flame is formed in a state close to the stoichiometric ratio of fuel to air
Implementation Method 6
the premix combustor is a system for premixing fuel and air and then feeding and burning them in the combustion chamber
Implementation Method 7
the mixing ratio of fuel and air on the flame sheet is lower than that in the diffusion combustion
Data Source
Figure 1
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AI summary
An apparatus for controlling a gas turbine combustor having a diffusion combustion burner and a premix combustion burner comprising: a rotating speed detector for detecting a rotating speed of gas turbine, a recorder for recording the detected value of the rotating speed of gas turbine detected by the rotating speed detector, an arithmetic unit for calculating a change with time of the rotating speed of gas turbine in accordance with details of the detected value of the rotating speed of gas turbine recorded in the recorder, and a fuel control unit for judging a starting situation of reduction in the rotating speed of gas turbine on the basis of the change with time of the rotating speed of gas turbine calculated by the arithmetic unit and controlling respectively a fuel flow rate for the diffusion combustion burner to be fed to the diffusion combustion burner installed in the gas turbine combustor and a fuel flow rate for the premix combustion to be fed to the premix combustion burner.