Gas Turbine Combustor Tapered Outlet Ring NOx Reduction
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Solution Overview
Problem
Conventional combustors for gas turbines face challenges in reducing NOx generation due to limited film air supply, leading to increased retention time and flame temperature, which results in higher NOx production, especially when premixed gas combustion occurs near the inner wall surface of the combustion liner.
Innovation Solution
The combustor design includes a pilot nozzle, main nozzles arranged circumferentially, a combustor basket, and a ring at the tip end with a decreasing inner diameter, promoting a swirling flow that moves the combustion region downstream, reducing high-temperature retention time and NOx generation by increasing mixing length and uniformizing fuel concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If compressed air is used as film air to prevent premixed gas combustion near the inner wall surface, then the premixed gas concentration is diluted and combustion is suppressed, but the volume of compressed air available for mixing with fuel decreases
Solution Approach 1:
The invention changes the geometric parameters of the outlet outer ring, specifically making the inner diameter decrease toward the downstream side (tapered configuration). This parameter change modifies the flow characteristics to suppress premixed gas combustion near the inner wall surface without requiring additional film air, thereby preserving the volume of compressed air available for fuel mixing while still preventing harmful combustion.
2Duration of action of moving object
If premixed gas combustion occurs on the upstream side of the combustor, then the retention time of high-temperature combustion gas increases, but the amount of NOx generation increases
Solution Approach 1:
The tapered configuration of the outlet outer ring (inner diameter decreasing toward downstream) changes the flow parameters to promote combustion occurrence further downstream in the combustor. This parameter change reduces the retention time of high-temperature combustion gas in the combustor, thereby reducing NOx generation while maintaining stable combustion.
3Device complexity
If the inner diameter of the outlet outer ring is constant, then the structure is simple, but premixed gas combustion occurs near the inner wall surface and retention time increases
Solution Approach 1:
The invention applies a tapered configuration where the inner diameter of the outlet outer ring decreases toward the downstream side. This geometric parameter change creates a flow control effect that suppresses premixed gas combustion near the inner wall surface, reduces retention time, and decreases NOx generation, while adding only moderate structural complexity.
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 NOx generation by moving the combustion region and high-temperature zone downstream, decreasing the size of recirculation flows, and enhancing fuel uniformity, thereby lowering flame temperature and NOx production.
Implementation Method 1
a ring provided at a tip end of the combustor basket... formed such that the inner diameter thereof decreases toward the downstream side of the flow of premixed gas... promoting a swirling flow that moves the combustion region downstream
Implementation Method 2
mixing of such gas is, even after the gas exits from the main burner, continuously promoted until combustion. Accordingly, a fuel concentration becomes more uniform toward the downstream side of the combustor
Implementation Method 3
decreasing the size of recirculation flows, and enhancing fuel uniformity, thereby lowering flame temperature and NOx production
Data Source
AI summary
An object is to realize combustion flame which can further reduce the amount of NOx generation. A combustor (14) includes a pilot nozzle (40); a plurality of main nozzles (44) arranged apart from the pilot nozzle (40) in the circumferential direction on the outer peripheral side of the pilot nozzle (40) and configured to perform premix combustion; a combustor basket (34) surrounding the pilot nozzle (40) and each main nozzle (44); an outlet outer ring (50) provided at a tip end of the combustor basket (34); and a combustion liner (36) fitted, at an inner surface thereof, onto the outer periphery of the combustor basket (34) and surrounding the outlet outer ring (50). The outlet outer ring (50) is formed parallel to an inner wall surface (66) of the combustion liner (36).