Augmenter Swirler Pilot Flame Stabilization
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Solution Overview
Problem
Aircraft gas turbine engine augmenters face challenges with unstable flame propagation due to lean fuel-air ratios and flow losses caused by traditional flameholders, leading to unreliable ignition and reduced engine efficiency during reheat operations.
Innovation Solution
The implementation of a fuel/air swirler with a swirl chamber and louvered or vane-equipped air swirler, combined with radial and step ring flameholders, and tubular injector chutes for efficient mixing and flame stabilization, along with a fuel injector and igniter for reliable ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If traditional flameholders are used for flame stabilization, then flame stability is improved, but flow losses increase and engine efficiency decreases
Solution Approach 1:
The invention extracts the flame stabilization function from traditional flameholders and relocates it to a pilot stage with a swirler device. The swirler creates a recirculation zone that stabilizes the pilot flame, which then propagates to the main combustor without requiring traditional flameholders in the main flow path, thereby reducing flow losses.
Solution Approach 2:
The pilot stage acts as an intermediary between the fuel injection system and the main combustor. It provides a stable ignition source that reliably ignites the main fuel-air mixture, eliminating the need for flameholders that would otherwise be required to stabilize the flame directly in the main flow.
2Power
If pilot spray rings receive fuel from aircraft fuel system during reheat operation, then thrust augmentation is enabled, but fuel pressure diminishes momentarily causing lean fuel-air ratio and pilot flame blowout
Solution Approach 1:
The swirler device is pre-configured to create a recirculation zone that traps hot gases and maintains a stable pilot flame before main fuel injection occurs. This preliminary flame stabilization ensures reliable ignition even when fuel pressure fluctuates during transient operations like reheat activation.
Solution Approach 2:
The swirler changes the flow parameters by creating a recirculation zone with reduced velocity and extended residence time. This modifies the local flow conditions to maintain a rich fuel-air ratio in the pilot stage, ensuring stable combustion despite system-wide fuel pressure variations.
3Object-generated harmful factors
If fuel-air ratio is reduced in pilot stage, then emission control is improved, but ignition reliability decreases due to lean mixture
Solution Approach 1:
The combustor is segmented into a pilot stage and a main combustor stage. The pilot stage maintains a rich fuel-air ratio for reliable ignition, while the main combustor operates with controlled fuel-air ratios for emission management. This segmentation allows independent optimization of ignition reliability and emissions.
Solution Approach 2:
Different fuel-air ratios are applied to different zones: the pilot stage receives a rich mixture for stable flame establishment, while the main combustor receives a controlled mixture for efficient combustion and emission control. The swirler creates local recirculation that maintains rich conditions in the pilot zone despite overall lean 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
This configuration enhances flame stability, improves ignition reliability, reduces flow losses, and increases engine efficiency by ensuring consistent combustion during both dry and reheat operations, while maintaining durability and performance.
Implementation Method 1
A swirler is effective for producing a recirculation zone which provides a stable light-off source for flameholders
Implementation Method 2
Fuel spraybars and flameholders are mounted between the turbines and the exhaust liner for injecting additional fuel when desired during reheat, thrust augmentation, or afterburning operation for burning in the augmenter combustor
Data Source
AI summary
A turbofan gas turbine engine augmenter includes a fuel/air swirler disposed between an axially extending bypass flowpath and an axially extending exhaust flowpath. A swirler inlet is axially open to and positioned substantially normal to the bypass flowpath and a swirler outlet is open to and positioned substantially parallel to the exhaust flowpath. A swirl chamber within the fuel/air swirler is between the swirler inlet and the swirler outlet. A swirl axis of the fuel/air swirler extends through the swirler outlet substantially normal to the exhaust flowpath. An air swirler may be centered about the swirl axis within the fuel/air swirler. The air swirler may be a louvered or have a plurality of swirling vanes. The swirler inlet may be radially offset with respect to the swirl axis. An air scoop may lead from the swirler inlet to a rounded swirler housing within which the air swirler is disposed.