Gas Turbine Load Unload Path Control
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Solution Overview
Problem
Conventional gas turbine systems face challenges in controlling emissions during loading and unloading processes, particularly at low loads, where emissions compliance is difficult to maintain due to fluctuations in combustion modes and fuel nozzle activation.
Innovation Solution
A load/unload method for gas turbine systems that progresses through progressive combustion modes, activating a varying number of fuel nozzles in both primary and secondary combustion stages, while controlling the primary combustion stage exit temperature within a predefined target range to maintain emissions compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional combustion modes are used during loading/unloading, then the gas turbine system can operate across a wide load range, but emissions compliance cannot be maintained at low loads
Solution Approach 1:
The combustion section is divided into multiple combustion stages (header combustion stage and axial fuel staging combustion stage), each with independently controllable fuel nozzles. This segmentation allows selective activation of different combustion stages to optimize emissions control at various load levels while maintaining overall system adaptability.
Solution Approach 2:
The system dynamically adjusts combustion modes by selectively activating different fuel nozzles in the header and axial fuel staging stages based on operating conditions. This dynamic control enables the system to adapt combustion characteristics to maintain emissions compliance across the full load range, particularly at low loads where emissions control is most challenging.
2Power
If more fuel nozzles are activated to increase power output, then the gas turbine system achieves higher load, but carbon monoxide emissions increase during combustion mode transitions
Solution Approach 1:
The axial fuel staging combustion stage is positioned downstream from the header combustion stage, allowing preliminary combustion of fuel in the header stage followed by secondary combustion in the axial stage. This preliminary action ensures complete combustion and reduces carbon monoxide emissions even when multiple fuel nozzles are activated to increase power output.
Solution Approach 2:
The two-stage combustion system ensures continuous and complete combustion by sequentially activating fuel nozzles in both stages. This continuity prevents incomplete combustion and carbon monoxide generation, even during transient operations when power output is increased by activating multiple fuel nozzles.
3Device complexity
If the combustion section reference temperature is used for control, then the combustion section can be managed simply, but emissions compliance cannot be ensured during loading/unloading
Solution Approach 1:
The control system uses feedback from temperature sensors positioned at strategic locations (including the exit of the combustion region and intermediate points between combustion stages) to monitor combustion conditions. This feedback enables real-time adjustment of fuel nozzle activation and air flow to ensure emissions compliance while maintaining manageable control system complexity.
Solution Approach 2:
The system replaces simple reference temperature control with a multi-parameter control approach that incorporates temperature monitoring at multiple locations, fuel flow rates, and air flow rates. This substitution enables precise emissions control during loading/unloading while keeping the control system manageable through integrated electronic control.
4Temperature
If air flow is increased to control combustion temperature, then the combustion temperature can be maintained, but the low load capability is reduced
Solution Approach 1:
The system applies local quality control by independently managing air flow and fuel flow to different combustion stages. At low loads, the axial fuel staging combustion stage can be activated with reduced air flow, allowing combustion temperature control without requiring proportional increases in overall air flow, thus preserving low load capability.
Solution Approach 2:
The system changes operational parameters by selectively activating different fuel nozzles and adjusting air flow rates to match the specific combustion mode being operated. This parameter adjustment allows combustion temperature control at low loads without requiring excessive air flow, maintaining the system's low load capability while ensuring emissions compliance.
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 effectively reduces carbon monoxide emissions during startup and turndown processes, ensuring emissions compliance down to full speed no load (FSNL) and extending the low-load capability of the gas turbine system.
Implementation Method 1
a combustion section. Specifically, the compressed air is supplied to a number of combustors each having a number of fuel nozzles, i.e., burners, which use the air in a combustion process with a fuel
Implementation Method 2
The combustion section is in flow communication with a turbine section in which the combustion gas stream's kinetic and thermal energy is converted to mechanical rotational energy
Data Source
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AI summary
A loading/unloading method for a gas turbine system (100) is disclosed. The gas turbine system (100) includes a combustion section (106) featuring a primary combustion stage (108) with a first plurality of fuel nozzles (140, 162, 170, 176, 180, 182) and a downstream, secondary combustion stage with a second plurality of fuel nozzles (140, 162, 170, 176, 180, 182). For loading, the method progresses through each of a plurality of progressive combustion modes hat sequentially activate a higher number of at least one of the first or second plurality of fuel nozzles (140, 162, 170, 176, 180, 182); and for unloading, the method progresses through each of a plurality of progressive combustion modes that sequentially activate a lower number of at least one of the first or second plurality of fuel nozzles (140, 162, 170, 176, 180, 182). During each combustion mode, regardless of whether loading or unloading, a primary combustion stage (108) exit temperature of a combustion gas flow is controlled to be within a predefined target range corresponding to the respective combustion mode.