Helmholtz Resonator Mounting for Gas Turbine Combustor Liners
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Solution Overview
Problem
Existing gas turbine combustors face challenges in effectively damping high-frequency acoustic vibrations due to the limitations of Helmholtz resonators being integrated into the cooling system, which restricts their tuning capabilities and can lead to thermo-mechanical stresses at welded joints.
Innovation Solution
A combustor design featuring an annular inner and outer liner with air holes, where Helmholtz resonators are mounted proud of the outer liner's surface, using a grommet assembly to allow differential thermal expansion and prevent thermo-mechanical stresses, while maintaining unobstructed cooling air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Helmholtz resonators are integrated into the cooling system between inner and outer liners, then the cooling function is utilized, but the ability to tune the resonators is reduced and thermo-mechanical stresses occur
Solution Approach 1:
The patent separates the resonator tuning function from the cooling system by providing independent adjustment mechanisms for resonator cavity dimensions and opening sizes, allowing each parameter to be optimized separately without compromising the other function
Solution Approach 2:
The patent introduces adjustable components such as movable plugs or adjustable openings that act as intermediaries between the resonator cavity and the cooling system, enabling independent control of resonator dimensions while maintaining cooling air flow paths
2Reliability
If welded joints are used to ensure gas tight seal between throat section and combustor wall, then sealing is improved, but thermo-mechanical stresses lead to cracks and reliability issues
Solution Approach 1:
The patent replaces rigid welded joints with flexible sealing elements such as grommets or elastomeric seals that can accommodate thermal expansion and contraction differences between the throat section and combustor wall, maintaining gas tight sealing without transmitting thermo-mechanical stresses
Solution Approach 2:
The patent designs the mounting structure to allow for differential thermal expansion between the throat section and combustor wall by providing clearance or expansion joints, preventing stress buildup from thermal mismatch while maintaining sealing integrity
3Adaptability or versatility
If Helmholtz resonators are located outside the outer liner, then separation from cooling air path is achieved, but cooling air flow may be affected
Solution Approach 1:
The patent positions the resonators in a spatial arrangement that allows them to be acoustically coupled to the combustor volume while physically separated from the cooling air path, using three-dimensional space utilization to achieve both independence and non-interference with cooling flow
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 dampens acoustic vibrations without impacting cooling efficiency and minimizes thermo-mechanical stresses, enhancing the reliability of the combustor by allowing independent tuning of resonators and accommodating thermal expansion differences.
Implementation Method 1
a Helmholtz resonator, in its simplest form, consists of an enclosed volume (cavity) containing air connected to the combustion chamber with an opening. Due to a pressure wave resulting from the combustion process, air is forced into the cavity increasing the pressure within the cavity.
Implementation Method 2
The energy of the pressure wave generated within the combustor is thus dissipated by resonance within the Helmholtz resonator. Energy dissipation is optimized by matching the resonance frequency of the Helmholtz resonator to the acoustic mode of the combustor.
Implementation Method 3
a grommet assembly that allows for relative thermal expansion between the inner liner and the outer liner proximate the throat
Data Source
AI summary
A combustor liner may include an annular inner liner and an annular outer liner with a plurality of air holes thereon. The outer liner may be positioned circumferentially around the inner liner such that an annular cooling space is defined between the inner and the outer liner. The combustor liner may also include at least one resonator coupled to the outer liner such that a base of the resonator is separated from the outer liner to form a gap with an external surface of the outer liner. The combustor liner may also include a throat extending from the base of the resonator penetrating the inner liner and the outer liner. The combustor liner may further include a grommet assembly that allows for relative thermal expansion between the inner liner and the outer liner proximate the throat.