Stepped Exhaust Diffuser Hub to Reduce Pressure Loss
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Solution Overview
Problem
The sudden expansion in the exhaust diffuser of a gas turbine leads to pressure loss and flow separation, reducing the efficiency of the exhaust process and affecting the overall efficiency of the composite power generation system.
Innovation Solution
A cylindrical hub extension with a stepped portion is introduced, forming a two-stage expansion pattern and equipped with quadrangular guides to distribute the flow, reducing sudden pressure changes and flow separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conical hub with constant diameter is used in the exhaust diffuser, then the structure is simple and easy to manufacture, but a sudden expansion in flow space occurs at the distal end, causing pressure loss and flow separation
Solution Approach 1:
The hub is segmented into multiple sections along its length: a first section with a first diameter, a second section with a second diameter smaller than the first, and a third section with a third diameter smaller than the second. This segmentation creates a stepped configuration that divides the single sudden expansion into multiple gradual expansions, reducing flow separation and pressure loss while maintaining manufacturing simplicity through standardized sectioned construction.
2Device complexity
If a conical hub with constant diameter is used in the exhaust diffuser, then the structural design is simple, but flow separation occurs at the rear of the hub, reducing exhaust efficiency
Solution Approach 1:
The hub is divided into three distinct sections with progressively smaller diameters, creating a stepped structure. This segmentation transforms the single abrupt expansion into multiple controlled expansion stages, reducing flow separation and improving exhaust efficiency. The segmented design adds only moderate structural complexity while significantly enhancing performance.
Solution Approach 2:
The hub diameter is varied along the longitudinal dimension, creating a stepped three-dimensional structure. This dimensional variation allows the flow space to expand gradually in the axial direction rather than suddenly, reducing flow separation and improving exhaust efficiency without requiring complex radial or circumferential modifications.
3Reliability
If the diameter of the conical casing gradually increases in downstream direction, then the exhaust diffuser can properly diffuse the combustion gas, but a sudden expansion occurs at the distal end of the hub, causing pressure loss
Solution Approach 1:
The hub is segmented into three sections with progressively smaller diameters, creating a stepped configuration that matches the gradual expansion of the conical casing. This segmentation allows the hub to properly diffuse combustion gas along its length while preventing sudden expansion at the distal end, thereby maintaining exhaust diffusion performance and reducing pressure loss simultaneously.
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 significantly reduces pressure loss and flow separation, improving the exhaust efficiency by minimizing the sudden expansion section and promoting uniform flow distribution.
Implementation Method 1
Due to this sudden expansion section of the flow space, a sudden change in pressure occurs in a flow of combustion gas
Implementation Method 2
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
Figure 1~2
Figure 3
Figure 4~5
AI summary
An exhaust diffuser hub (210) disposed at a longitudinal center of an exhaust diffuser (106) is provided. The exhaust diffuser hub (210) includes a hub extension (400) extending from a downstream end thereof in a longitudinal direction of the exhaust diffuser (106). A transverse cross-sectional area of the hub extension (400) is smaller than a transverse cross-sectional area of the hub (210).