Turbomachine Combustor Cap with External Turbulator Step
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Solution Overview
Problem
Conventional turbomachines face challenges in reducing undesirable pollutants like NOx and CO emissions while maintaining flame stability, particularly at lower loads, as they often require significant cooling airflow that can impact efficiency.
Innovation Solution
A cap assembly for a turbomachine combustor featuring a centerbody with an external turbulator member having a step-to-gap ratio between 0.8 and 1.2, which enhances air/fuel mixing and reduces the required cooling airflow by creating a passage that optimizes flame stability and emission control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional DLN combustors are used to reduce NOx and CO emissions, then pollutant generation is reduced, but flame stability deteriorates at lower loads due to lean fuel mixtures
Solution Approach 1:
The combustor is divided into distinct functional zones: a recirculation zone created by the step feature that stabilizes flames, and a separate mixing zone enhanced by turbulator members. This segmentation allows lean fuel mixtures to be maintained for low emissions while providing a stable recirculation region for flame anchoring.
Solution Approach 2:
Cooling airflow acts as an intermediary substance that serves dual purposes: it cools the combustor structure and, when properly managed through the gap passages, enhances mixing and stabilizes flames. The step feature intermediates between the cooling airflow and the combustion process, creating a recirculation zone that improves flame stability.
2Temperature
If significant cooling airflow is used to maintain combustor temperatures, then thermal management is improved, but combustion efficiency deteriorates due to reduced air/fuel mixing
Solution Approach 1:
The cooling airflow is directed through specific gap passages between the centerbody wall and external turbulator members, creating localized high-velocity jets that enhance mixing in specific regions. The step feature creates a localized recirculation zone that concentrates combustion activity, improving overall combustion efficiency despite the presence of cooling airflow.
Solution Approach 2:
The design utilizes pneumatic principles by allowing cooling airflow to pass through defined gap passages, where it interacts with the fuel/air mixture. The step feature creates a recirculation pattern that enhances the pneumatic mixing of gases, converting what would be wasted cooling flow into a useful mixing mechanism that improves combustion efficiency.
3Productivity
If the gap between the centerbody wall and external turbulator is reduced to enhance mixing, then air/fuel mixing is improved, but the risk of flame blowout increases
Solution Approach 1:
The step feature creates an asymmetric geometry in the gap passage, with the step positioned at a specific location rather than uniformly distributed. This asymmetry generates a recirculation zone on the downstream side of the step, creating a low-velocity region that protects the flame from blowout while maintaining good mixing in the high-velocity gap region.
Solution Approach 2:
The step feature introduces a radial dimension to the gap passage geometry, creating a three-dimensional flow pattern with recirculation zones. This dimensional change allows the gap to serve dual functions: maintaining narrow dimensions for good mixing while creating recirculation regions through the step that protect 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 solution effectively reduces pollutant emissions and enhances flame stability, leading to improved combustion efficiency and operational performance by optimizing air/fuel mixing and minimizing cooling airflow, thereby increasing overall turbomachine efficiency.
Implementation Method 1
An external turbulator member in operable communication with the cap assembly is spaced from the wall to form a passage defined by a gap between the wall of the centerbody and the external turbulator
Implementation Method 2
The external turbulator member includes a step positioned at the second end of the centerbody. The step defines a radial distance about the second end of the centerbody.
Implementation Method 3
guiding a cooling airflow through a passage defined by a gap extending between the wall of the centerbody and a turbulator member having a step portion
Data Source
AI summary
A turbomachine includes a combustor assembly, a cap assembly attached to the combustor assembly, a centerbody within the cap assembly, a wall of the centerbody having a first end, a second end and an intermediate portion, and an external turbulator member in operable communication with the cap assembly. The external turbulator member is spaced from the wall to form a passage defined by a gap between the wall of the centerbody and the external turbulator. The external turbulator member includes a step positioned at the second end of the centerbody. The step defines a radial distance about the second end of the centerbody. The external turbulator member is formed having a step-to-gap ratio relative to the centerbody in a range of about 0.8 to about 1.2.