Combustor Flame Holding Ring with Localized Openings for NOx Reduction
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Solution Overview
Problem
In gas turbines, the flame holding ring's uniform flame holding effect leads to local temperature increases and elevated NOx production due to insufficient pre-mixing upstream of the flame holding ring.
Innovation Solution
A combustor design featuring an upstream-side wall with varying air inlet densities and strategically positioned openings on the flame holding ring to create an uneven flame holding effect in the circumferential direction, impairing flame holding in regions with insufficient pre-mixing and reducing air flow through cut-outs and through holes, thereby suppressing NOx generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flame holding ring is disposed at the radially inner side of the outlet portions of the plurality of nozzles to stabilize the pre-mixed flame, then the flame holding effect is improved, but combustion occurs before pre-mixing progresses sufficiently at a relatively upstream position, which increases the temperature locally and increases NOx
Solution Approach 1:
The flame holding ring is provided with openings at specific locations to create local variations in flame holding capability. The openings are strategically positioned to impair flame holding in regions where pre-mixing is insufficient, while maintaining flame holding in regions where pre-mixing is adequate. This local differentiation allows the system to maintain overall flame stability while preventing localized premature combustion that generates NOx
Solution Approach 2:
The flame holding ring is segmented into different regions with varying flame holding characteristics. By dividing the ring into sections with and without openings, the invention creates distinct zones: one that promotes flame holding and another that impairs it. This segmentation enables selective control of combustion locations, preventing premature combustion in upstream regions while maintaining stable flame holding downstream
2Reliability
If the flame holding effect of the flame holding ring is uniform in the circumferential direction, then the flame is held stably, but combustion occurs at upstream positions where pre-mixing is insufficient, leading to local temperature increase
Solution Approach 1:
The flame holding ring incorporates openings at specific circumferential positions to create local differences in flame holding effect. These openings are placed in regions where premature combustion occurs, locally impairing flame holding to push combustion downstream to regions with better pre-mixing. This local modification prevents hot spots and temperature uniformity issues while maintaining overall flame stability
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 design effectively suppresses combustion at upstream regions with insufficient pre-mixing and reduces NOx production while maintaining stable flame holding, achieving a balanced combustion process.
Implementation Method 1
a plurality of air inlets for supplying air toward the flame holding ring via an annular space at the radially inner side of the outlet portions of the plurality of nozzles
Implementation Method 2
A combustor used for a gas turbine includes a plurality of nozzles disposed in the circumferential direction to form a pre-mixed flame
Implementation Method 3
a low flow-velocity region at the downstream side of the flame holding ring in the circumferential-directional region corresponding to the first region
Implementation Method 4
combustion occurs before pre-mixing progresses sufficiently at a relatively upstream position near the flame holding ring, which may increase the temperature locally
Data Source
AI summary
The upstream-side wall portion 54 includes, in the circumferential direction thereof, a first region 31 where air inlets 30 are formed at a lower density, and a second region 32 which is disposed at a position offset from the first region 31 in the circumferential direction, and in which the air inlets 30 are formed at a higher density than in the first region 31.