Centrifugal Fan Blade Front Edge Geometry for Exfoliation Control
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Solution Overview
Problem
Conventional centrifugal multiblade fans with tapered blades experience performance degradation due to exfoliation at the blade front edge, caused by significant discrepancies in inlet angles and inflow conditions between the side shroud and main shroud sides, leading to inefficient air flow and noise issues.
Innovation Solution
The centrifugal multiblade fan design features blades with a front edge shape that is inclined radially outward from the main shroud to the side shroud, maintaining a constant blade thickness and curvature radius, which reduces the difference in inlet angles between the two sides, minimizing exfoliation and performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the front edge of the blade is made shorter toward the side shroud to reduce the inner diameter, then the air blowing effect is improved on the main shroud side, but exfoliation at the blade front edge is easily caused on the side shroud side
Solution Approach 1:
The blade front edge is designed with different characteristics at different locations: the main shroud side maintains a longer chord length for effective air blowing, while the side shroud side has a specifically controlled front edge shape with reduced curvature radius to prevent exfoliation. This local differentiation resolves the contradiction between power generation and reliability.
Solution Approach 2:
The invention changes the geometric parameters of the blade front edge by controlling the curvature radius and inlet angle variations across the blade span. By optimizing these parameters, the design achieves both effective air blowing on the main shroud side and exfoliation prevention on the side shroud side.
2Reliability
If the inlet angle is made smaller from the main shroud side toward the side shroud side to limit exfoliation, then exfoliation is reduced, but the air flow efficiency deteriorates due to significant inlet angle discrepancies
Solution Approach 1:
The invention optimizes the inlet angle distribution across the blade by controlling the curvature radius of the front edge. This parameter control enables the inlet angle to vary smoothly from the main shroud side to the side shroud side, reducing exfoliation while maintaining air flow efficiency through coordinated parameter changes.
3Stress or pressure
If the blade chord length is made long on the side shroud side to improve static pressure, then static pressure is improved, but exfoliation at the blade front edge is caused due to rapid change in air flowing direction
Solution Approach 1:
The blade design incorporates different chord lengths and front edge shapes at different radial positions. The side shroud side has a specifically optimized front edge with reduced curvature radius to prevent exfoliation, while maintaining sufficient chord length for static pressure generation. This local quality differentiation resolves the contradiction between pressure and reliability.
Solution Approach 2:
The invention controls the curvature radius of the blade front edge, making it smaller on the side shroud side to reduce the rapid change in air flowing direction and prevent exfoliation, while maintaining the overall blade geometry for effective static pressure generation.
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 design enhances airflow efficiency by reducing inlet angle discrepancies, limiting exfoliation at the blade front edge, and improving overall performance while simplifying production and reducing costs.
Implementation Method 1
a centrifugal multiblade fan for drawing air from one end side of the fan in an axial direction of the fan and for blowing out the air radially outward of the fan
Data Source
AI summary
A centrifugal multiblade fan includes a rotatable shaft, blades, a side shroud, and a main shroud. A front edge has a shape inclined radially outward in a direction from the main shroud toward the side shroud. When viewed from an axial direction, a corner part on a positive pressure surface-side is located on a tangential line of a positive pressure surface reference curve at a positive pressure surface side reference corner part, and when viewed from the axial direction, a curvature radius of a negative pressure surface becomes larger in a direction from the side shroud toward the main shroud.