Axial Flow Impeller Divider Strip Layout for Turbulent Noise
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Solution Overview
Problem
Conventional axial flow impellers generate significant turbulent noise due to airflow separation at the rear blade edge, leading to turbulence.
Innovation Solution
An axial flow impeller design featuring a divider strip with a greater thickness than other blade positions, where the circumferential span from the divider strip to the front blade edge is between 0.2 and 0.4 times the span to the rear blade edge, and the rear blade edge is thinner than the front, reducing turbulence by directing airflow closer to the blade surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the blade thickness is uniform at all positions, then the manufacturing is simple, but the airflow separates before reaching the rear blade edge causing turbulent noise
Solution Approach 1:
The blade thickness is made non-uniform by introducing a divider strip that creates a localized thickened region. Specifically, the blade has a first thickness in a first circumferential region and a second thickness in a second circumferential region, where the thickness ratio is between 0.2 and 0.4. This local quality variation redirects airflow to delay separation and reduce turbulent noise while maintaining manufacturing feasibility.
2Object-generated harmful factors
If the blade thickness varies significantly, then the turbulence is reduced, but the structural strength may be compromised
Solution Approach 1:
The blade thickness parameter is changed in a controlled manner through the divider strip design. The thickness ratio between the first and second circumferential regions is optimized to be between 0.2 and 0.4, which is sufficient to redirect airflow and reduce turbulence while maintaining adequate structural strength. The gradual transition of thickness variation avoids sudden changes that would compromise strength.
3Object-generated harmful factors
If the airflow separation point is moved forward, then the blade surface area exposed to high-speed flow is reduced, but the airflow efficiency decreases
Solution Approach 1:
Instead of allowing airflow to separate naturally at the rear blade edge, the divider strip inverts the expected flow pattern by creating a thickened region that actively redirects airflow. This inversion moves the effective separation point backward, keeping airflow attached to the blade surface longer, thereby maintaining airflow efficiency while reducing turbulent noise 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 effectively moves the airflow separation point backwards, reducing turbulence and noise by approximately 2 dB compared to conventional impellers, while maintaining airflow efficiency and strength.
Implementation Method 1
the airflow separates before reaching the rear blade edge. As a result, the airflow becomes turbulent at a position adjacent to the rear blade edge of the blade
Implementation Method 2
the airflow becomes turbulent at a position adjacent to the rear blade edge of the blade, which generates a large turbulent noise
Data Source
AI summary
An axial flow impeller includes a hub and a blade at the hub. A blade edge of the blade includes a blade root edge, a front blade edge, a blade top edge, and a rear blade edge connected sequentially. The blade includes a divider strip arranged between the front blade edge and the rear blade edge and connecting the blade root edge and the blade top edge. At a same circumference, a ratio between a circumferential span from the divider to the front blade edge and a circumferential span from the front blade edge to the rear blade edge is equal to or greater than 0.2 and equal to or smaller than 0.4, a thickness of the divider strip is greater than thicknesses of other portions of the blade, and a thickness of the rear blade edge is smaller than a thickness of the front blade edge.