Gas Turbine Combustor Flow Guide for Ignition Stability
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Solution Overview
Problem
In annular type gas turbine combustors, high upstream flow velocity and interference between swirling air streams can lead to unstable circulation regions, reducing ignitability due to incomplete flash point propagation and deformation of the circulation region.
Innovation Solution
The implementation of a flow guide with a conical and cylindrical shape downstream of the fuel nozzle assemblies, which gradually increases the sectional area for air and air-fuel mixture flow, directing swirling air streams to expand radially and reducing interference between neighboring fuel nozzle assemblies, thereby stabilizing the circulation region and enhancing ignitability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If 50 to 80% of the total inflow air is allowed to flow through the fuel nozzle assemblies to create a leaned air-fuel mixture, then low NOx combustion is achieved, but the average flow velocity in the upstream region becomes high and the flash point propagation is prevented
Solution Approach 1:
A flow guide is introduced as an intermediary component between the fuel nozzle assemblies and the combustion chamber. The flow guide has a conical portion with gradually increasing sectional area that mediates the high-velocity air flow, converting it into a more controlled flow pattern that allows flash point propagation while maintaining the leaned combustion ratio for low NOx emission.
Solution Approach 2:
The flow guide changes the flow parameters (velocity distribution, flow direction) in the upstream region. By using a conical shape with gradually increasing area, the flow guide transforms the high-velocity uniform flow into a lower-velocity distributed flow, enabling flash point propagation while preserving the overall air-fuel ratio for low NOx combustion.
2Stability of the object's composition
If strong swirl is given to the air flowing into the combustion chamber to create a uniform air-fuel mixture, then mixing is improved, but swirling air streams from neighboring fuel nozzle assemblies interfere with each other and stable circulation region cannot be formed
Solution Approach 1:
The flow guide segments the swirling flow from each fuel nozzle assembly into distinct flow paths. By providing individual flow guides for each nozzle assembly, the interference between neighboring swirling streams is reduced, allowing each to maintain its circulation region while still achieving overall uniform mixing in the combustion chamber.
Solution Approach 2:
The flow guide extends the flow control into the radial dimension with its conical shape. This dimensional extension allows the swirling flows to expand radially outward, reducing their interaction in the axial direction and preventing interference between neighboring assemblies while maintaining mixing effectiveness.
3Productivity
If the flow velocity within the upstream region becomes high, then the leaned combustion ratio is maintained, but the circulation region is deformed and ignitability is lowered
Solution Approach 1:
The flow guide performs preliminary flow conditioning before the air-fuel mixture enters the main combustion zone. By pre-adjusting the velocity distribution and flow pattern in the upstream region, the flow guide ensures that ignition can occur reliably at lower velocities while still achieving the desired combustion efficiency in the main combustion zone.
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 flow guide design facilitates the formation of a stable circulation region, allowing for easier flame propagation and increased ignitability by minimizing the distance between neighboring fuel nozzle assemblies and preventing massive swirling flows, resulting in improved ignition performance.
Implementation Method 1
swirling air streams 100 from the neighboring fuel nozzle assemblies will interfere with each other
Implementation Method 2
the flow guide has a conical portion of a shape flared in a conical shape from the upstream side towards the downstream side
Data Source
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AI summary
An annular type gas turbine combustor having a plurality of fuel nozzle assemblies (10) on a circumference includes a pilot nozzle unit (12) for spraying a fuel for diffusive combustion from a pilot outer peripheral nozzle (34) into a combustion chamber (8), a main nozzle unit (14) provided so as to surround the pilot nozzle unit (12) for spraying a fuel for premix combustion, and a flow guide (27) disposed on a downstream side of each of the fuel nozzle assemblies (10) and having a sectional area of a passage for air and air-fuel mixture from each of the fuel nozzle assemblies (10), which gradually increase in a downstream direction.