Gas Turbine Premixer Injector Swirl Flow Stabilization
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Solution Overview
Problem
Designing premixer injectors for gas turbine engines is challenging due to the need to effectively mix air and fuel while also damping out thermo-acoustic instability, requiring a balance among various design criteria.
Innovation Solution
The premixer injector assembly features a fuel tube with fins and mixing channels, where air and fuel are injected through helical-shaped apertures and channels to create a swirl flow, stabilizing the flame and reducing thermo-acoustic instability through a pair of counter-rotating vortices, ensuring uniform mixing and robust operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mixing structures are used, then manufacturing is simpler, but air-fuel mixing effectiveness is insufficient
Solution Approach 1:
The mixing chamber is segmented into multiple regions by radial fins, creating distinct mixing zones that improve air-fuel mixing effectiveness. The fins divide the flow into separate streams that interact and mix more thoroughly, addressing the need for better mixing without requiring a complete redesign of the entire injector structure.
Solution Approach 2:
Helical grooves are introduced on the fuel injection plates, adding a rotational dimension to the fuel injection process. This creates swirling flow patterns that enhance mixing by introducing tangential velocity components, improving mixing effectiveness without significantly complicating the manufacturing process.
2Reliability
If simple injector design is used, then device complexity is lower, but thermo-acoustic instability is not effectively damped
Solution Approach 1:
Helical grooves on the fuel injection plates generate controlled swirling flows and vibrations that counteract thermo-acoustic instabilities. The rotational motion created by the helical features introduces high-frequency disturbances that dampen low-frequency combustion oscillations, improving thermal stability.
Solution Approach 2:
Radial fins act as intermediary structures between the air and fuel flows, facilitating controlled interaction and mixing. These fins create a buffer zone that promotes stable combustion by ensuring uniform mixing before the flame front propagates, thereby reducing thermo-acoustic instability.
3Productivity
If uniform mixing is prioritized, then combustion efficiency improves, but nitrogen oxides emissions increase
Solution Approach 1:
The injector creates locally optimized mixing zones with varying equivalence ratios. Radial fins and helical grooves produce regions of rich and lean mixing, allowing efficient combustion in certain zones while maintaining lower temperatures in others to reduce NOx formation. This spatial variation in mixture quality enables both high efficiency and low emissions.
Solution Approach 2:
The design changes the physical parameters of the flow by introducing swirl and rotation through helical features. These parameter changes affect the combustion process by extending residence time and improving mixing, which enhances efficiency while the controlled temperature distribution reduces nitrogen oxides emissions.
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 design effectively mixes air and fuel, stabilizes flames, reduces nitrogen oxides emissions, and minimizes thermo-acoustic instability, providing a robust and efficient premixing solution for gas turbine engines.
Implementation Method 1
air and fuel are injected through helical-shaped apertures and channels to create a swirl flow, stabilizing the flame and reducing thermo-acoustic instability through a pair of counter-rotating vortices
Implementation Method 2
stabilizing the flame and reducing thermo-acoustic instability through a pair of counter-rotating vortices
Implementation Method 3
The premixer injector assembly features a fuel tube with fins and mixing channels, where air and fuel are injected through helical-shaped apertures and channels
Data Source
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AI summary
A premixer injector assembly in a gas turbine engine includes at least one premixer injector. The premixer injector includes a fuel tube having a fuel feed passage enclosed by an outer surface, a plurality of fins coupled to the fuel tube extending from the outer surface of the fuel feed passage, the outer surface of the fuel feed passage between adjacent fins having a concave shape, a plurality of mixing channels defined between adjacent fins, a plurality of fuel injection apertures disposed along the fuel feed passage to direct fuel from the fuel feed passage to the mixing channels, an air tube coupled to the fuel tube to at least partially enclose the fuel tube, and a plurality of air injection openings arranged along the air tube to inject air to the mixing channels.