Axial-Flow Blade U-W Edge Design for Friction and Surge
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Solution Overview
Problem
Axial-flow fluid machine blades experience frictional loss and surge issues due to uneven chord lengths, leading to airflow separation and performance degradation when the working point shifts to higher pressure ratios.
Innovation Solution
The blade design features a leading edge with a U-shape and a trailing edge with a W-shape in plan view, reducing chord lengths and surface areas, particularly between the tip, mid-span, and root portions, while maintaining a longer chord length at the mid-span area to prevent airflow separation and surge resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the chord length at mid-span portion is shortened to reduce surface area and frictional loss, then frictional loss is reduced and performance is improved, but airflow separation occurs at mid-span portion and surge is generated
Solution Approach 1:
The blade employs different chord length characteristics at different spanwise locations: the mid-span portion has a longer chord length to prevent airflow separation and maintain surge resistance, while the tip and root portions have shorter chord lengths to reduce surface area and frictional loss. This localized differentiation resolves the contradiction by optimizing each region for its specific functional requirement.
2Loss of energy
If the surface area of the blade is reduced to lower frictional loss, then frictional loss decreases and performance improves, but the blade becomes more susceptible to airflow separation and surge
Solution Approach 1:
The blade design applies local quality by maintaining a longer chord length at the mid-span portion where airflow separation is most likely to occur, while reducing chord lengths at the tip and root portions. This localized approach minimizes the total surface area and frictional loss while preserving airflow attachment at the critical mid-span region.
3Loss of energy
If the chord length is uniformly reduced along the blade span to minimize surface area, then frictional loss is reduced, but the blade cannot maintain surge resistance at high pressure ratios
Solution Approach 1:
Rather than uniformly reducing chord length, the invention applies local quality by selectively maintaining a longer chord length at the mid-span portion while shortening the chord lengths at the tip and root portions. This non-uniform distribution reduces overall surface area and frictional loss while preserving the surge-resistant property at the critical mid-span region where airflow separation typically initiates.
Data Source
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AI summary
An axial-flow fluid machine blade which achieves reduction of the frictional loss of the blade and provision of a high surge-resistant property is provided. An axial-flow fluid machine blade 60 used for an axial-flow fluid machine includes a leading edge 61 projecting at the tip portion and the root portion thereof toward the upstream side and a trailing edge 62 projecting at the tip portion, the mid-span portion and the root portion thereof toward the downstream side.