Gas Turbine Fuel Split and Temperature Control for Composition Variation
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Solution Overview
Problem
Existing gas turbine control systems face challenges in maintaining stability and emissions compliance when faced with rapid variations in fuel composition, as current methods are either costly or slow in response, with fuel split control being limited in its authority and fuel temperature control being slow to react.
Innovation Solution
A dual-effector control system is employed, where a high-bandwidth fuel split module rapidly adjusts fuel distribution and a lower-bandwidth fuel temperature module maintains a margin to keep the fuel split module within its authority limits, allowing the system to accommodate a wider range of fuel quality variations without the need for costly Wobbe meters or gas chromatographs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fuel split control is used to rapidly adjust fuel distribution, then the response speed to fuel composition variation is improved, but the control authority is limited and becomes ineffective beyond certain boundaries
Solution Approach 1:
The control system is segmented into two independent effectors: a fast-acting fuel split control system and a slower fuel temperature control system. Each effector operates within its own optimal range, with the fuel split system handling rapid adjustments and the temperature system providing long-term stability. This segmentation allows the system to leverage the speed advantage of fuel split control while avoiding its authority limitations.
Solution Approach 2:
The control system dynamically switches between different effectors based on operating conditions. The fuel split control is activated for rapid response to composition changes, while the fuel temperature control takes over when the split control approaches its boundaries. This dynamic allocation of control authority extends the overall adaptability range of the system.
2Adaptability or versatility
If fuel temperature control is used to maintain constant MWI, then the adaptability to fuel composition variation is improved, but the response speed becomes slow due to heating and cooling time constants
Solution Approach 1:
The fuel temperature control system performs preliminary action by maintaining the fuel temperature within an optimal range in advance. This ensures that when rapid composition changes occur, the fuel is already in a state that allows the fuel split system to respond effectively, reducing the overall response time while maintaining adaptability.
Solution Approach 2:
The fuel temperature control acts as an intermediary between the fuel composition variation and the combustion process. By adjusting the temperature, it modifies the fuel properties to enhance the effectiveness of the fuel split control, bridging the gap between composition variation and stable combustion.
3Adaptability or versatility
If fuel split control is pushed to its boundaries to accommodate wider fuel variation, then the adaptability range is extended, but the stability and reliability of control are compromised
Solution Approach 1:
The system incorporates a buffer zone by maintaining the fuel split control away from its absolute boundaries. The fuel temperature control system provides a cushioning effect by compensating for composition variations, allowing the fuel split control to operate within a safer range while still accommodating wide fuel variation. This beforehand cushioning prevents the system from reaching unstable boundary conditions.
Data Source
AI summary
A system and method control a gas turbine subject to fuel composition variation. The method includes operating a first effector to control the gas turbine based on fuel composition. The method also includes operating a second effector to maintain operation of the first effector within a first boundary limit, the second effector operation being initiated when the operating the first effector reaches a second boundary limit within the first boundary limit.