Logarithmic Spiral Blade for Centrifugal Fan Flow Separation
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Solution Overview
Problem
Existing centrifugal fan designs fail to optimize airflow pressure and efficiency due to inefficiencies caused by flow separations along blade surfaces, despite various blade shapes and orientations being explored.
Innovation Solution
The design features a circular back plate, a ring-shaped shroud, and a tubular hub with blades having a logarithmic spiral shape and a mean camber line with an angle of return, along with a specific thickness distribution and inclination angle, allowing for a naturally fluid pathway that reduces flow separation inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional blade shapes (flat, forward curved, backward inclined) are used, then the fan structure is simple and easy to manufacture, but flow separation occurs along blade surfaces reducing efficiency and pressure
Solution Approach 1:
The patent applies curvature by forming the blade surfaces with specific radii of curvature (R1, R2, R3, R4) to create a naturally fluid pathway. The curved blade surfaces eliminate sharp edges and corners that cause flow separation, while the specific curvature radii optimize the airflow pattern to reduce energy loss.
Solution Approach 2:
The patent changes geometric parameters of the blade surfaces by defining specific curvature radii (R1, R2, R3, R4) and their relationships to blade dimensions (c, t, l). These parameter changes transform conventional flat or simply curved blades into optimized surfaces that prevent flow separation while maintaining manufacturability.
2Loss of energy
If unique airfoil blades or twisted flat blade designs are used, then fan efficiency improves, but the blade design complexity increases
Solution Approach 1:
The patent applies local quality by providing different curvature radii (R1, R2, R3, R4) at different locations along the blade surface. Each region of the blade has optimized curvature suited to its specific function in the airflow path, improving efficiency without requiring complex overall blade geometry.
Solution Approach 2:
The patent adds surface curvature dimensions to the blade design by defining radii of curvature in multiple directions. This transforms two-dimensional flat or twisted blades into three-dimensional surfaces with optimized airflow characteristics, improving efficiency through surface geometry rather than complex overall shape.
3Stress or pressure
If three-dimensional blades with specific thickness distribution are used, then airflow pressure increases, but manufacturing complexity increases
Solution Approach 1:
The patent changes thickness distribution parameters by defining specific curvature radii (R1, R2, R3, R4) that control the thickness variation along the blade. These parameter changes create optimized airflow pressure while the radii are expressed in terms of standard blade dimensions (c, t, l), maintaining manufacturability.
Solution Approach 2:
The patent uses curved surfaces with specific radii to create the three-dimensional thickness distribution. The curvature radii (R1, R2, R3, R4) define the thickness profile in a way that is both aerodynamically efficient and compatible with conventional manufacturing processes, avoiding the need for complex forming operations.
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 enhances the P-Q characteristics and energy efficiency of centrifugal fans by up to 15% and reduces electric power consumption by 40-100 W, improving airflow pressure and fan performance.
Implementation Method 1
reducing inefficiencies generated by flow separations along surfaces of the blades
Implementation Method 2
Boundary layer controlled logarithmic spiral blade
Data Source
AI summary
An impeller structure for a centrifugal fan apparatus includes a circular back plate, a ring-shaped shroud, and a tubular hub. The ring-shaped shroud and the tubular hub are respectively located a predetermined distance above and at the center of said circular back plate. The impeller structure further includes a plurality of blades which are annularly disposed around the tubular hub between the circular back plate and the ring-shaped shroud. Each of the plurality of blades includes a chord with a logarithmic spiral shape, and a mean camber line with an angle of return against the chord.