Protective grille with improved efficiency and noise characteristics
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Solution Overview
Problem
Conventional protective grilles on fans impair the static overall efficiency and increase noise, especially at higher volume flows when air is admitted through them.
Innovation Solution
A protective grille with a three-dimensionally curved axial design, featuring a convex radial outer region and a planar central region, with radial and circumferential webs of thinner walls, and varying angular placement of circumferential webs, reducing flow resistance and noise-generating turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a protective grille with thick-walled radial and circumferential webs is used to ensure sufficient stability, then the structural strength and stability are improved, but the flow resistance increases and noise increases
Solution Approach 1:
The protective grille employs a three-dimensionally curved axial design with a convex radial outer region and a planar central region. This curvature creates an arched shape that provides structural strength through geometric rigidity, allowing the use of thinner-walled radial and circumferential webs while maintaining stability and reducing flow resistance compared to conventional flat designs
Solution Approach 2:
The protective grille features different geometric properties in different regions: the radial outer region has a convex curved envelope surface for strength and stability, while the central region has a planar envelope surface parallel to the radial plane for optimized airflow. This local differentiation allows each region to fulfill its specific functional requirements
2Strength
If a protective grille with thick-walled radial and circumferential webs is used to ensure sufficient stability, then the structural strength and stability are improved, but the noise increases
Solution Approach 1:
The three-dimensionally curved axial design with convex radial outer region creates an arched structure that provides structural strength without requiring thick walls. The thinner walls reduce turbulence and noise-generating flow separation, achieving both structural integrity and noise reduction
Solution Approach 2:
The planar central region with envelope surface parallel to the radial plane optimizes airflow characteristics and reduces turbulence in the central flow path, while the convex radial outer region provides structural support. This local differentiation minimizes noise-generating turbulence throughout the grille
3Volume of moving object
If a protective grille is placed close to the fan wheel, then the compactness is improved, but the static overall efficiency of the fan deteriorates
Solution Approach 1:
The protective grille transitions from a conventional two-dimensional flat structure to a three-dimensionally curved axial design. This dimensional change allows the grille to be positioned closer to the fan wheel while maintaining adequate flow passage area and optimizing airflow characteristics, thereby improving compactness without sacrificing static overall efficiency
Data Source
AI summary
A protective grille for a fan has a web structure which comprises radial webs spaced apart in a circumferential direction and coaxial circumferential webs spaced apart in a radial direction. The protective grille has at least a radial outer region and a central region around a central axis of the protective grille. An envelope surface spanned by the radial outer region and the central region is of convexly curved form in the radial outer region and is of flat form, parallel to a radial plane of the protective grille, in the central region.