Chamfered Grommet Assembly for Gas Turbine Dilution Air Flow
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Solution Overview
Problem
Traditional dilution air grommet assemblies in gas turbine combustors exhibit low discharge coefficients, leading to impaired dilution air jet flow penetration and overheating, which affects engine efficiency and durability.
Innovation Solution
A grommet assembly with a chamfered core and cooling channels, featuring specific dimensional relationships and a conical surface angle of thirty degrees, enhances dilution air flow penetration by improving discharge coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional dilution air grommet assemblies are used, then the structure is simple, but the discharge coefficient is low leading to impaired flow penetration
Solution Approach 1:
The grommet core is segmented into multiple functional zones: an unchamfered portion and a chamfered portion with specific conical angles. This segmentation allows each zone to perform its specific function - the unchamfered portion maintains structural integrity while the chamfered portion optimizes flow penetration and discharge coefficient.
Solution Approach 2:
The grommet assembly implements local quality by providing enhanced cooling channels specifically at the core region where heat exposure is highest. The cooling channels are strategically positioned to address the local thermal conditions, improving metal temperature management where it is most critical while maintaining overall structural simplicity.
2Ease of manufacture
If traditional grommet design is used, then manufacturing is simple, but dilution air jet flow penetration is impaired
Solution Approach 1:
The invention changes critical geometric parameters of the grommet core, specifically implementing a chamfered portion with conical angles between 15-45 degrees and specific length ratios. These parameter changes significantly improve flow penetration speed and discharge coefficient while remaining compatible with standard manufacturing processes for metal components.
3Device complexity
If traditional grommet assembly is used, then structure is straightforward, but metal temperatures are high causing overheating
Solution Approach 1:
The grommet assembly introduces cooling channels as an intermediary thermal management system between the hot combustion chamber environment and the grommet core. These channels facilitate the flow of cooling air that acts as a thermal mediator, reducing metal temperatures through convective heat transfer while maintaining the straightforward overall assembly structure.
Solution Approach 2:
The invention utilizes pneumatic cooling by channeling compressed air through cooling passages in the grommet core. This pneumatic system removes heat from the grommet structure through forced convection, effectively reducing metal temperatures without requiring complex active cooling systems or moving parts.
4Device complexity
If traditional grommet design is used, then gas recirculation is high, but structural simplicity is maintained
Solution Approach 1:
The chamfered core design introduces a dimensional change at the grommet outlet edge, creating a conical transition that alters the flow field geometry. This dimensional modification redirects the dilution air jet to penetrate deeper into the combustion chamber, reducing harmful gas recirculation zones near the grommet while maintaining overall structural simplicity.
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
The improved grommet assembly significantly enhances dilution air jet flow penetration, reducing gas recirculation and metal temperatures, thereby increasing engine efficiency and durability.
Implementation Method 1
The grommet further includes a plurality of cooling channels spaced circumferentially about the grommet for flowing cooling air from the cooling cavity and into the combustion chamber
Implementation Method 2
A plurality of dilution holes are generally spaced circumferentially about the wall assembly and flow dilution air from a cooling plenum and into the combustion chamber
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A grommet assembly (102) and method of design to enhance the flow coefficient, thereof, includes a shell (76) having a first side (112) and an opposite second side (114), and a chamfered grommet (104) projecting through the shell (76) along a centerline and including an annular first end surface (134) spaced outward from the first side (112) and a conical face (138) spanning axially and radially inward from the annular first end surface (134) and axially beyond the second side (114). The assembly may further include a panel (80) spaced from the shell (76) and defining a cooling cavity (116) therebetween with the conical surface (138) defining at least in-part a hole (130) in fluid communication through the shell (76) and panel (80) and isolated from the cooling cavity (116). A plurality of cooling channels (144) in the grommet (104) are in fluid communication with the cooling cavity (116) and communicate through the panel (80). The combination of the conical face (138) and the cooling channels (144) improve the discharge coefficient of the grommet (104) while enhancing grommet cooling.