Exhaust Diffuser Hub Extension for Reduced Flow Separation
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Solution Overview
Problem
The existing exhaust diffuser hub structure in gas turbines experiences significant pressure loss and flow separation due to sudden expansion in the flow space, leading to reduced efficiency in power generation systems.
Innovation Solution
The introduction of a cylindrical hub extension with a smaller transverse cross-sectional area than the hub, forming a stepped portion, and the use of guides on the side surfaces to manage the flow and reduce sudden expansion, thereby minimizing pressure loss and flow separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conical hub with constant diameter is used to form the exhaust diffuser, then the structure is simple and easy to manufacture, but sudden expansion in flow space occurs at the distal end, causing pressure loss and flow separation
Solution Approach 1:
The hub is segmented into two distinct sections: a constant-diameter section and a tapered extension section. This segmentation allows the flow space expansion to occur gradually through the tapered section rather than suddenly at the hub termination, reducing flow separation and pressure loss while maintaining manufacturing simplicity.
Solution Approach 2:
The hub extension adds a longitudinal dimension to the flow space transition, creating a gradual tapering effect along the exhaust diffuser length. This dimensional extension transforms the sudden expansion problem into a controlled, progressive expansion that minimizes energy loss.
2Ease of manufacture
If the hub diameter is constant to simplify manufacturing, then production is easier, but flow separation occurs at the hub end, reducing exhaust efficiency
Solution Approach 1:
The hub is divided into a constant-diameter portion and a tapered extension portion. This segmentation enables the flow to transition smoothly through the tapered section, preventing flow separation and maintaining high exhaust efficiency, while the constant-diameter section preserves manufacturing simplicity.
Solution Approach 2:
Different sections of the hub have different geometric properties: the main hub body maintains constant diameter for ease of manufacture, while the extension section features a tapered geometry to optimize flow characteristics. This local differentiation resolves the contradiction between manufacturing simplicity and exhaust efficiency.
3Volume of moving object
If a sudden expansion section is created at the hub distal end, then the exhaust diffuser structure is compact, but pressure loss increases due to sudden pressure change
Solution Approach 1:
The hub extension utilizes the longitudinal dimension to create a tapered transition zone, allowing the exhaust diffuser to achieve gradual flow expansion without significantly increasing the radial or axial footprint. This maintains compactness while reducing pressure loss.
Solution Approach 2:
The tapered hub extension introduces a curved, gradual transition geometry instead of a sharp angular expansion. This curved transition smooths the flow path and reduces sudden pressure changes, minimizing energy loss while maintaining a compact overall structure.
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 reduces pressure loss and flow separation, enhancing the exhaust efficiency by smoothing the flow transition and delaying sudden pressure changes, as evidenced by computational analysis.
Implementation Method 1
a sudden change in pressure occurs in a flow of combustion gas, thereby causing a loss. A portion of the flow drawn into the end of the conical hub is not properly joined, thereby forming a long flow separation section at a rear of the conical hub
Data Source
AI summary
An exhaust diffuser hub disposed at a longitudinal center of an exhaust diffuser is provided. The exhaust diffuser hub includes a hub extension extending from a downstream end thereof in a longitudinal direction of the exhaust diffuser. A transverse cross-sectional area of the hub extension is smaller than a transverse cross-sectional area of the hub.