Gas Turbine Combustor Inner Cap Acoustic Damping
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Solution Overview
Problem
Current gas turbine combustor designs face challenges in mitigating both high and low frequency acoustic pressure oscillations, which can lead to hardware damage due to combustion instability and dynamic pressure pulses, especially in lean premixed combustion systems, and existing additive manufacturing methods require temporary supports for overhang structures, increasing manufacturing complexity and cost.
Innovation Solution
The method involves additive manufacturing of combustor inner caps with integrated high-frequency and low-frequency dampers, where the overhang structures are tilted at an angle less than or equal to 45 degrees, eliminating the need for temporary supports and allowing for the direct manufacturing of overhang ledges without additional processing steps, and the dampers are designed to target specific acoustic frequencies for effective damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If additive manufacturing is used to manufacture overhang structures, then manufacturing complexity increases due to need for temporary supports, but traditional manufacturing methods cannot achieve complex geometries
Solution Approach 1:
The patent changes the geometric parameter of the overhang structure by limiting the overhang angle to 45 degrees or less. This parameter modification allows the structure to be self-supporting during additive manufacturing without requiring temporary supports, thereby reducing manufacturing process complexity while still achieving complex geometries
Solution Approach 2:
Instead of adding temporary supports to enable overhang structures (traditional approach), the patent inverts the approach by designing the overhang angle itself to eliminate the need for supports. The solution flips the problem from 'how to support overhangs' to 'how to design overhangs that don't need support'
2Object-generated harmful factors
If lean premixed combustion systems are used, then NOx emissions are reduced, but combustion instability increases causing high dynamic pressure oscillations
Solution Approach 1:
The patent segments the combustion chamber into distinct regions with different acoustic damping characteristics. By placing specific dampers at strategic locations, the combustion instability problem is divided into manageable frequency ranges, allowing the lean premixed combustion to operate at low equivalence ratios without causing harmful pressure oscillations
Solution Approach 2:
The patent converts the harmful high-frequency acoustic oscillations into a beneficial design feature by intentionally designing dampers that target specific frequency ranges. The combustion instability that would normally cause damage is transformed into a controlled parameter that can be managed through acoustic damping, allowing the system to operate at optimal lean equivalence ratios
3Weight of moving object
If traditional manufacturing methods are used for combustor inner caps, then manufacturing process is simpler, but weight reduction opportunities are lost
Solution Approach 1:
The patent merges multiple components (inner cap, dampers, and support structures) into a single integrated additive manufactured part. This consolidation eliminates the need for separate manufacturing and assembly processes, achieving weight reduction through material optimization while maintaining manufacturing feasibility through the 45-degree overhang angle design
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 approach reduces the weight of the combustor inner cap by about 50% and effectively dampens acoustic pressure oscillations across a range of frequencies, preventing hardware failure and simplifying the manufacturing process by eliminating the need for temporary supports and subsequent removal steps.
Implementation Method 1
Specifically, metallic parts can be additively manufactured using, for instance, selective laser melting, selective electron beam melting processes, and direct metal laser melting (DMLM). In these processes, layers of metallic powder are disposed. A laser beam or electron beam is directed onto the bed of metallic powder, locally melting the powder, and the beam is subsequently advanced on the powder surface. Molten metallic substance solidifies
Implementation Method 2
devices and methods for making gas turbine combustor inner caps with acoustic damping that mitigates combustion dynamic pressure pulses
Data Source
AI summary
A method of making a combustor cap assembly uses an additive manufacturing process of consecutively adding material in layers along an upstream axial build direction starting from a base side positioned transverse to the upstream axial build direction. The base side has at least one acoustic port. A bump side extends from the base side in the upstream axial build direction and has at least one damper projecting from the bump side. The damper has at least one inclined face forming an angle with the upstream axial build direction of less than or equal to 45 degrees. The resulting cap assembly includes a hot side with an acoustic port and a cold side with at least one damper with an inclined face and a damper chamber in communication with the acoustic port.