Radial Swirler Pre-Chamber Combustor Flame Flashback Prevention
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Solution Overview
Problem
In gas turbine Dry Low Emissions (DLE) combustion systems, the presence of hydrogen in the fuel mixture causes flame flashback into the pre-chamber due to higher flame speeds, leading to reverse flow and instability, which increases emissions and pressure fluctuations, and reduces component lifespan.
Innovation Solution
A combustor design featuring a radial swirler and a pre-chamber with a convergent portion that creates a vortex with a swirl number between 0.3 and 0.8, and a convergent shape with a specific area ratio and length to inlet diameter ratio, preventing flame flashback by increasing the velocity of the air/fuel mixture and stabilizing the flame location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydrogen is added to the fuel mixture to improve combustion efficiency, then energy output is improved, but flame flashback into the pre-chamber occurs due to higher flame speeds
Solution Approach 1:
The combustor is divided into distinct functional zones: a pre-chamber with convergent geometry for flame stabilization, a throat region for flow control, and a main combustion chamber. This segmentation allows the pre-chamber to handle the high-speed hydrogen combustion while the throat geometry prevents flashback propagation to the swirler, thus maintaining both high power output and flame stability.
Solution Approach 2:
The convergent pre-chamber acts as an intermediary zone between the swirler and main combustion chamber. Its specific geometry (inlet area to outlet area ratio of 1.45-1.70, axial length to inlet diameter ratio of 0.45-0.55) creates a flow regime that stabilizes the flame and prevents flashback while allowing efficient hydrogen combustion to occur, thus mediating between the conflicting requirements of high power and stability.
2Stability of the object's composition
If the swirler creates a strong vortex to stabilize the flame, then flame location is improved, but reverse flow increases causing emissions to worsen
Solution Approach 1:
The swirler is designed with specific parameters (swirl number between 0.3 and 0.8, annular array of vanes with specific geometry) that create an optimal vortex strength. This parameter optimization allows the flame to be stabilized at the desired location while preventing excessive reverse flow that would lead to increased emissions of nitrous oxides and sulphur oxides, thus resolving the contradiction between flame stability and emissions control.
3Reliability
If the pre-chamber is designed with a convergent shape to prevent flashback, then flame reverse flow is reduced, but the complexity of the combustor design increases
Solution Approach 1:
The convergent geometry is applied locally to the pre-chamber section where it is most needed for flashback prevention, rather than throughout the entire combustor. The specific dimensions (inlet area to outlet area ratio of 1.45-1.70, axial length to inlet diameter ratio of 0.45-0.55) are optimized for this local function, allowing effective flashback prevention while minimizing overall design complexity and maintaining manufacturability.
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 design effectively reduces flame reverse flow, stabilizes the flame, improves combustion dynamics, decreases emissions such as nitrous oxides and sulphur oxides, and extends the life of components by positioning the combustion flames further downstream, while accommodating hydrogen content up to 80% by volume in the fuel.
Implementation Method 1
The radial swirler comprises a base plate having an annular array of vanes and fuel injectors arranged to direct an air/fuel mixture radially inwardly and tangentially to create a vortex
Implementation Method 2
direct an air/fuel mixture radially inwardly and tangentially to create a vortex that flows through the pre-chamber
Implementation Method 3
The pre-chamber has a portion which is convergent in a downstream direction... preventing flame flashback by increasing the velocity of the air/fuel mixture
Data Source
AI summary
A combustor for a gas turbine engine having a central axis about which is arranged in flow sequence a radial swirler, a pre-chamber partly defined by a wall and a combustion chamber. The radial swirler has a base plate having an annular array of vanes and fuel injectors arranged to direct an air/fuel mixture radially inwardly and tangentially to create a vortex that flows through the pre-chamber and into the combustion chamber. The pre-chamber has a portion which is convergent in a downstream direction.