Turbine Combustor Micro-Mixer Nozzles for Screech Tone Mitigation
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Solution Overview
Problem
Combustion instability in turbomachines due to high-frequency dynamic fields, particularly 'screech' tones, leads to hardware damage and restricts the operating envelope, with existing solutions either limiting operating conditions or requiring complex control schemes for fuel-air ratio manipulation.
Innovation Solution
The implementation of micro-mixer nozzle arrangements with differential axial length dimensions in turbomachine combustors, where micro-mixer nozzle bodies of varying lengths are arranged in parallel to mitigate high-frequency dynamics, preventing harmonic and sub-harmonic vibrations that cause screech tones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If operating conditions are restricted to avoid combustion instability, then hardware damage is prevented, but the operating envelope is reduced
Solution Approach 1:
The invention changes the physical parameters of the fuel injection system by introducing micro-mixer nozzles with specific geometric characteristics (diameter 0.5-2.0mm, length-to-diameter ratio 0.5-2.0). These parameter changes modify the combustion process to suppress high-frequency dynamics across a broader operating range, resolving the contradiction between hardware protection and operating flexibility
Solution Approach 2:
The fuel injection system is segmented into multiple micro-mixer nozzles arranged in parallel, each with differential axial length dimensions. This segmentation creates distributed combustion zones that disrupt the coupling between combustion and acoustic fields, preventing screech tones while maintaining wide operability
2Object-affected harmful factors
If fuel-air ratio is manipulated to suppress combustion instability, then screech tones are reduced, but control complexity increases
Solution Approach 1:
The invention replaces the complex mechanical control system (fuel-air ratio manipulation) with a passive geometric solution (micro-mixer nozzle configuration). The noise suppression is achieved through the inherent acoustic properties of the micro-mixer structure rather than active control, eliminating the need for complex sensors and actuators
Solution Approach 2:
The micro-mixer nozzles self-regulate the combustion process through their geometric design. The differential axial lengths and small diameters create natural flow patterns that suppress high-frequency dynamics without requiring external control inputs, making the system self-regulating across operating conditions
3Object-affected harmful factors
If fuel-air ratio is manipulated to suppress combustion instability, then combustion dynamics are reduced, but combustion efficiency decreases
Solution Approach 1:
The micro-mixer nozzles create localized mixing zones with specific geometric characteristics that promote rapid and complete combustion. The small diameter and optimized length-to-diameter ratio ensure thorough fuel-air mixing at the nozzle level, maintaining high combustion efficiency while the distributed arrangement suppresses overall combustion dynamics
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 effectively reduces high-frequency dynamic-tone mitigation, allowing for a broader operating envelope without the need for complex control schemes, while maintaining efficient combustion.
Implementation Method 1
micro-mixer nozzle arrangements with differential axial length dimensions in turbomachine combustors, where micro-mixer nozzle bodies of varying lengths are arranged in parallel to mitigate high-frequency dynamics
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A turbomachine combustor (10) includes a combustion chamber (30); a plurality of micro-mixer nozzles (14) mounted to an end cover of the combustion chamber, each including a fuel supply pipe (26) affixed to a nozzle body (28) located within the combustion chamber, wherein fuel from the supply pipe mixes with air in the nozzle body prior to discharge into the combustion chamber; and wherein at least some of the nozzle bodies (28) of the plurality of micro-mixer nozzles (14) have axial length dimensions that differ from axial length dimensions of other of the nozzle bodies.