Lift Fan Diffuser Duct with Splitters for Hover Efficiency
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Solution Overview
Problem
Existing lift fans face challenges in achieving adequate performance and efficiency in a compact package, particularly in providing direct lift and hover capabilities.
Innovation Solution
A lift fan apparatus incorporating a duct with a diffuser and splitters, which increases airflow and reduces flow separation, allowing for a more compact design while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lift fan is designed to provide adequate performance and efficiency, then the device size increases, but compactness deteriorates
Solution Approach 1:
The diffuser is nested within the duct structure, with the duct incorporating the diffuser as an integrated component. This allows the diffuser to be housed within the existing duct volume, maximizing the use of available space and achieving enhanced hover efficiency without proportionally increasing device size
Solution Approach 2:
The diffuser increases the flow area in the radial dimension rather than extending the duct length axially. By expanding the flow area outwardly within the duct, the design achieves improved airflow and hover efficiency while maintaining a compact axial footprint
2Productivity
If the duct flow area is increased to enhance hover efficiency, then airflow increases, but surface friction losses increase
Solution Approach 1:
The duct is segmented into distinct sections: an inlet section, a mid-section with constant flow area, and an exit section with increased flow area. The diffuser is positioned only in the exit section, allowing the majority of the duct length to maintain a compact cross-section while still achieving the desired airflow increase at the exit
Solution Approach 2:
The diffuser geometry is applied locally in the exit section rather than throughout the entire duct. This localized application increases the flow area only where needed to enhance hover efficiency, while minimizing the total surface area that would generate friction losses
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 solution enhances hover efficiency by increasing airflow through a given fan diameter and reduces surface friction losses, enabling more compact and efficient lift fan designs.
Implementation Method 1
a diffuser positioned downstream of the rotor. The diffuser has a flow area at an upstream end where it adjoins the mid-section, and a flow area at an exit which is greater than the flow area at the upstream end
Implementation Method 2
which increases airflow and reduces flow separation, allowing for a more compact design while maintaining efficiency
Data Source
Figure 1~2
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Figure 5~6
AI summary
A lift fan apparatus (10, 110, 210, 310) includes: a rotor (12, 112, 212) having at least one rotatable hub carrying at least one row of blades; a duct (36, 136, 236) surrounding the rotor (12, 112, 212), the duct (36, 136, 236) including spaced-apart peripheral walls extending between an inlet and an exit, the peripheral walls collectively defining a flow channel which includes a diffuser (50, 150, 250) disposed downstream of the rotor (12, 112, 212), in which a flow area at the exit is greater than a flow area at the rotor (12, 112, 212); and a plurality of spaced-apart splitters disposed in the diffuser (50, 150, 250), each of the splitters having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the splitters divide the diffuser (50, 150, 250) into a plurality of side-by-side flow passages (66, 166, 266, 366).