Sequential Combustor Auto-Ignition Flame Stabilization
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Solution Overview
Problem
Current sequential combustors for gas turbines face limitations in auto-ignition delay time and flame stabilization, leading to restricted combustor compactness, increased NOx emissions, and pressure losses due to reliance on recirculation zones and fluid dynamic processes.
Innovation Solution
The solution involves controlling auto-ignition reactions by varying the Mach number along the flow path, accelerating the fuel and oxidant flow in the premixing section to decrease static temperature, and then decelerating it to stabilize the flame, eliminating the need for recirculation zones and allowing combustion at higher Mach numbers, thus reducing NOx emissions and enabling a more compact combustor design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If recirculation zones are used to stabilize the flame, then flame stabilization is achieved, but pressure losses increase and combustor size increases
Solution Approach 1:
The invention extracts and eliminates the recirculation zones from the combustor design. By removing these fluid dynamic stabilization structures, the patent achieves flame stabilization through a different mechanism (auto-ignition control) while avoiding the pressure losses and increased combustor volume that recirculation zones inherently cause.
Solution Approach 2:
The invention replaces the mechanical/fluid dynamic stabilization mechanism (recirculation zones creating recirculating flows) with a chemical/thermal mechanism (controlled auto-ignition through temperature and residence time management). This substitution eliminates the need for large recirculation zones while achieving reliable flame stabilization.
2Reliability
If recirculation zones are used for flame stabilization, then flame stability is improved, but combustor volume increases
Solution Approach 1:
The invention extracts and eliminates the recirculation zones from the combustor design. By removing these fluid dynamic stabilization structures, the patent achieves flame stabilization through a different mechanism (auto-ignition control) while avoiding the pressure losses and increased combustor volume that recirculation zones inherently cause.
Solution Approach 2:
The invention changes the operating parameters of the combustor, specifically managing temperature profiles and residence times to enable controlled auto-ignition. By adjusting these parameters, the system achieves flame stabilization without requiring the large volumes necessary for recirculation zones, resulting in a more compact combustor design.
3Volume of moving object
If flow velocity is increased for compactness, then combustor size decreases, but flame stabilization becomes difficult
Solution Approach 1:
The invention changes the approach to flame stabilization by managing temperature and residence time parameters rather than relying on low velocity. By controlling the thermal history of the fuel-air mixture, the system enables reliable auto-ignition even at higher flow velocities, allowing for a more compact combustor while maintaining flame stability.
Solution Approach 2:
The invention replaces the mechanical/fluid dynamic stabilization mechanism (which requires low velocities and large recirculation zones) with a chemical/thermal mechanism (controlled auto-ignition). This substitution allows the combustor to operate at higher velocities while maintaining reliable flame stabilization, enabling compactness.
4Productivity
If auto-ignition delay time is reduced by increasing temperature, then CO turndown characteristics improve, but pressure drop increases
Solution Approach 1:
The invention changes the approach to reducing auto-ignition delay time by managing the thermal history and residence time of the fuel-air mixture rather than simply increasing inlet temperature. By controlling when and where auto-ignition occurs through temperature profiling, the system achieves improved CO turndown characteristics while avoiding the increased pressure drops that would result from higher inlet temperatures and associated velocity requirements.
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 extends CO turndown capabilities, reduces combustor size, lowers NOx emissions, and stabilizes the flame against perturbations, resulting in a more robust and cost-effective system with shorter residence times and improved integration into nozzle guide vanes.
Implementation Method 1
the flow of fuel and oxidant within the premixing section is accelerated, such that the static temperature drops, thereby slowing down the auto-ignition reactions
Implementation Method 2
after the high velocity premixing section the flow is accelerated still further, and then it is decelerated along a well-controlled, aerodynamically designed path. The resulting gradient in static temperature is then utilised to stabilize/anchor the auto-ignition flame
Implementation Method 3
the combustor comprises two distinct zones: the burner, or a premixing section (where the fuel and oxidant are premixed)
Implementation Method 4
At these temperatures, the fuel injected into the burner autoignites
Implementation Method 5
where the combustion takes place
Data Source
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AI summary
The present invention generally relates to a sequential combustor for a gas turbine. The invention additionally refers to a method for operating the same. Specifically, the invention concerns the second and/or subsequent stages of a re-heat, sequential or axiallystaged combustion system. According to the invention, variation in Mach number along the flow path is used to control static temperature variation, which in turn influences the progress of auto-ignition reactions that eventually lead to the onset of combustion.