Meridional Fan Blade Tip Non-Uniform Profile
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Solution Overview
Problem
Conventional axial flow fans in large-scale air ventilation and heating systems suffer from reduced efficiency and increased noise due to air leakage through the gap between the fan blades and the duct ring, primarily caused by uniform blade tips leading to vortex formation and turbulence.
Innovation Solution
The fan blades feature a non-uniform profile on the tip, with a flange extending axially on the downstream high-pressure side and a leading edge with a varying circumferential extent, along with undulating or stepped features to influence airflow and increase the leakage path resistance, thereby reducing turbulence and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform profile is used for fan blade tips, then manufacturing is simplified, but air leakage and turbulence increase, reducing efficiency and increasing noise
Solution Approach 1:
The blade tip is designed with different profiles at different locations: the leading edge has a non-uniform profile with varying thickness and curvature, while other portions maintain simpler geometry. This local differentiation reduces turbulence and air leakage without significantly complicating overall manufacturing
Solution Approach 2:
The blade tip profile is made asymmetric with respect to the uniform conventional design. The leading edge features varying thickness and curvature that are not symmetrically distributed, creating a non-uniform profile that disrupts vortex formation and reduces air leakage while remaining manufacturable
2Ease of manufacture
If a uniform profile is used for fan blade tips, then manufacturing is simplified, but noise generation increases due to vortex formation and turbulence
Solution Approach 1:
The non-uniform profile is applied specifically to the leading edge portion of the blade tip where vortex formation occurs, while other areas maintain simpler geometry. This localized modification reduces noise-generating turbulence without requiring complete redesign of the entire blade tip
Solution Approach 2:
The asymmetric non-uniform profile at the leading edge disrupts the symmetric vortex formation that occurs with uniform designs, reducing turbulence intensity and associated noise while maintaining ease of manufacture through targeted geometric modification
3Loss of energy
If the gap between fan tips and duct ring is minimized, then air leakage is reduced, but the risk of vortex formation and turbulence increases
Solution Approach 1:
The non-uniform profile is concentrated at the leading edge of the blade tip, creating a localized flow control feature that reduces turbulence without requiring increased gap clearance, thereby maintaining low air leakage while preventing vortex formation
Solution Approach 2:
The asymmetric leading edge profile disrupts the flow patterns that lead to vortex formation in the narrow gap between blade tips and duct ring, reducing turbulence while maintaining the minimal gap necessary for preventing excessive air leakage
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 fan efficiency by minimizing power consumption and noise by deflecting and dissipating the boundary layer, reducing air leakage and turbulence, and optimizing airflow through the leakage path.
Implementation Method 1
the non-uniform profile may be formed by undulations or by grooves or a mixture thereof in the outer surface... which increases the length of the leakage flow path and wherein the leading edge of the flange has a non-uniform profile so that the circumferential axial extent of the leading edge of the flange varies along the width of the blade tip
Implementation Method 2
The uniform profile of the known conventional blade tips lead to the generation of tight vortices at the blade tip and it is believed that these vortices, when they reach a critical state suddenly expand very rapidly, to the extent of provoking vortex bursting or collapse, which generates a great deal of turbulence
Implementation Method 3
a flange extending in the axial direction on the downstream, high pressure side of the fan, which increases the length of the leakage flow path
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
An axial fan adapted to be rotatably mounted in a cylindrical duct ring (3) has a plurality of fan blades (2) with peripheral blade tips (4) describing, in operation, a circular path adjacent the duct ring (3) The blade tips each have a leading edge (6) in the axial direction, a trailing edge (9) and a tip outer surface, at least one of the edges and/or the outer surface having a non-uniform profile for influencing the flow of air over the said tip outer surface.