Impeller Blade Segmentation for Centrifugal Force Management
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Solution Overview
Problem
High-speed rotating impellers with swept-forward blades face challenges due to centrifugal force, leading to stress concentration, deformation, and radial displacement of blades, which affects airflow stability and increases noise and static pressure issues.
Innovation Solution
An impeller design featuring a substantially annular joining member positioned radially inward of the blades to reduce the moment at the blade base caused by centrifugal force, preventing deformation and radial displacement, and allocating different roles to inward and outward blade portions to manage airflow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the degree of forward sweep of the blades is increased to improve airflow characteristics, then the airflow stability is improved, but the centrifugal force moment at the blade base increases causing deformation and radial displacement
Solution Approach 1:
The blade structure is segmented into multiple portions (first portion, second portion, third portion) along the radial direction, with each portion having different cross-sectional area ratios. This segmentation allows optimization of airflow characteristics in the forward-swept regions while maintaining structural strength through controlled area variations that reduce stress concentration.
Solution Approach 2:
Different portions of the blade are designed with different local qualities - specifically, different cross-sectional area ratios at various radial positions. The first portion has a larger area ratio for strength, the second portion has a controlled ratio for airflow, and the third portion has a smaller ratio for reducing centrifugal force effects. This local differentiation resolves the contradiction between airflow stability and blade strength.
2Productivity
If the rotation speed of the impeller is increased to improve productivity, then the air flow quantity increases, but the centrifugal force causes blade deformation and contact with the outer frame member
Solution Approach 1:
The blade is divided into segments with different cross-sectional area characteristics along the radial direction. This segmentation creates a gradient structure that reduces the overall moment of inertia and centrifugal force effects, allowing higher rotation speeds without blade deformation or contact with the outer frame member.
Solution Approach 2:
The cross-sectional area ratio parameter is varied along the radial direction of the blade. By changing this parameter from the base toward the tip, the blade achieves optimal balance between aerodynamic performance at high speeds and structural resistance to centrifugal forces, preventing radial displacement and maintaining reliability.
3Strength
If a joining member is provided at the radially outer ends of the blades to counteract centrifugal force, then the blade deformation is reduced, but backward airflow occurs at the gap between the joining member and outer frame member causing noise and static pressure deterioration
Solution Approach 1:
The harmful effect of the joining member (creating gaps that cause backward airflow) is extracted and eliminated. Instead of using a separate joining member at the radially outer ends, the blade itself is designed with integrated cross-sectional area variations that provide both structural strength and seamless airflow path, removing the source of the harmful backward airflow.
Solution Approach 2:
The functions of the blade and the joining member are merged into a single integrated blade structure. The cross-sectional area variations along the blade radius simultaneously provide centrifugal force resistance and maintain continuous airflow, eliminating gaps and the associated backward airflow, noise, and static pressure issues.
4Strength
If the cross-sectional area of the blade base is increased to reduce stress concentration, then the blade strength is improved, but the device complexity increases
Solution Approach 1:
The blade structure is segmented into distinct portions with progressively varying cross-sectional area ratios. This segmentation provides systematic stress distribution from the base outward, strengthening the blade base through controlled geometric progression rather than abrupt changes, thereby reducing complexity while maintaining strength.
Solution Approach 2:
The blade cross-sections are designed with curved, continuous transitions rather than sharp angles or discontinuities. This curvature principle creates smooth area variations along the radial direction, reducing stress concentration at the base while maintaining manufacturing simplicity and avoiding complex geometric features.
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 design enhances airflow stability, reduces noise, and improves static pressure characteristics by minimizing the impact of centrifugal force on blades, ensuring stable air blowing even at high speeds.
Implementation Method 1
Rotation of the impeller causes a centrifugal force to be applied to the blades. The centrifugal force is directed in a direction substantially parallel to a radial direction, from the base of each blade where the blade is joined to a support portion.
Data Source
AI summary
An impeller, a fan apparatus, and a method of manufacturing the impeller are provided. The impeller includes a support portion, a plurality of rotor blades, and a joining member. The joining member is a substantially annular member provided to strengthen the rotor blades against influence of a centrifugal force, and extends in a circumferential direction along a circle centered on a central axis so as to join the rotor blades to one another. In each of the rotor blades, a point of intersection of a leading edge of the rotor blade with a radially outer end of the rotor blade is positioned forward, with respect to a rotation direction, relative to a point of intersection of the leading edge with an outside surface of the support portion. The joining member is positioned radially inwards of the radially outer end of each of the rotor blades.