Gas Turbine Exhaust Diffuser Flow Separation Control
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Solution Overview
Problem
Gas turbines face inefficiencies due to flow separation in radial diffusers, leading to pressure loss and reduced performance, as existing technologies struggle to prevent separation between the internal diffuser guide and struts.
Innovation Solution
The exhaust diffuser incorporates ejection and suction holes arranged in specific patterns and structures, including slits, grooves, and shutters, to manage the flow and prevent partial separation, enhancing aerodynamic performance by guiding exhaust gas effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a radial diffuser is used to change combustion gas flow from axial to radial direction, then the exhaust system can accommodate vertical/side exhaust stacks, but flow separation occurs between internal diffuser guide and struts causing pressure loss
Solution Approach 1:
The patent uses fluid injection through ejection holes and fluid suction through suction holes to control the boundary layer flow. Compressed air is injected to prevent flow separation, and separated flow is suctioned and reinjected, using pneumatic principles to maintain attached flow and reduce pressure loss in the radial diffuser.
Solution Approach 2:
The patent changes the physical state and properties of the boundary layer by injecting compressed air (changing density and velocity parameters) and by suctioning/reinjecting flow (changing flow direction and energy parameters). This modifies the boundary layer characteristics to prevent separation and maintain aerodynamic efficiency.
2Device complexity
If conventional diffuser designs are used, then structural simplicity is maintained, but flow separation cannot be prevented, reducing combustor performance
Solution Approach 1:
The patent segments the diffuser surface into multiple zones with ejection holes and suction holes distributed at different locations. This segmentation allows localized flow control at critical separation points while maintaining the overall diffuser structure, improving performance without excessive complexity.
Solution Approach 2:
The patent introduces compressed air as an intermediary substance to interact with the boundary layer. The injected compressed air acts as a mediator that energizes the boundary layer and prevents flow separation, while the suction system removes separated flow. This intermediary approach significantly improves performance with relatively simple implementation.
Data Source
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AI summary
An exhaust diffuser (100) that is mounted at an outlet of a gas turbine (10) to eject exhaust gas to the outside and includes hollow cylindrical internal diffuser guide (101) and external diffuser guide (102). Further, the exhaust diffuser (100) includes struts (110) disposed between the internal diffuser guide (101) and the external diffuser guide (102) to space the internal diffuser guide (101) and the external diffuser guide (102) at a predetermined distance from each other, ejection areas (120) formed on an outer side of the internal diffuser guide (101) and having ejection holes (121) for ejecting compressed air in a flow direction of exhaust gas, and suction areas (130) formed on the outer side of the internal diffuser guide (101), disposed close to the ejection areas (120), and having suction holes (131) for suctioning exhaust gas in the opposite direction to a flow direction of the ejected exhaust gas.