Reverse Fin Cooling Fan Noise Reduction
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Solution Overview
Problem
Small air-cooled internal combustion engines face challenges in effectively cooling engines without generating excessive noise due to air turbulence and blade pass frequency, which traditional cooling fan systems fail to address adequately.
Innovation Solution
The design incorporates a cooling fan with reversed fins that extend between a band and a plate, offset at an angle, and a screen with radially outward blades, optimizing airflow to reduce turbulence and noise by adjusting the spacing between the fins and the housing, and potentially omitting the band for reduced material use and increased stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional cooling fan designs are used, then engine cooling function is provided, but excessive noise is generated due to air turbulence and blade pass frequency
Solution Approach 1:
The patent applies the inversion principle by reversing the traditional fin orientation. Instead of fins extending forward from the plate, the fins extend backward (reverse fins), which fundamentally changes the airflow interaction pattern. This reversal reduces blade pass frequency noise and air turbulence while maintaining effective engine cooling, directly resolving the contradiction between cooling effectiveness and noise generation.
2Temperature
If fins are extended further from the plate, then cooling efficiency improves, but air turbulence and noise increase
Solution Approach 1:
By inverting the fin direction to extend backward instead of forward, the patent achieves improved cooling efficiency through extended fin surface area while simultaneously reducing air turbulence and noise. The reverse orientation allows the fins to interact with airflow in a manner that enhances heat dissipation without creating the turbulent eddies and blade pass frequency noise associated with traditional forward-extending fins.
3Strength
If the band is included in the cooling fan structure, then structural support is provided, but material usage increases and stiffness may be reduced
Solution Approach 1:
The patent applies the extraction principle by removing the band component from the cooling fan structure. The design achieves adequate structural support through the plate and reverse fin configuration alone, eliminating the need for the additional band material. This reduction in material usage also increases the overall stiffness of the remaining structure while maintaining necessary structural support for the cooling function.
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 airflow efficiency while minimizing noise by reducing blade pass frequency and turbulence, providing effective engine cooling without excessive noise.
Implementation Method 1
Small air-cooled internal combustion engines face challenges in effectively cooling engines without generating excessive noise due to air turbulence and blade pass frequency
Data Source
AI summary
An engine assembly includes a crankcase, shaft, blower housing, and cooling fan. The shaft is rotatably coupled to the crankcase and defines a rotational axis. The blower housing includes an internal space. The cooling fan is disposed within the internal space, includes a plate defining an upper surface, and is positioned to rotate with the shaft about the rotational axis. The cooling fan includes a band having an inner band radius and an outer band radius. The cooling fan includes a plurality of reversed fins extending between the band and the upper surface and between a root adjacent to the rotational axis and a tip adjacent to the outer band radius, each fin offset at an angle measured in a counterclockwise direction from a plane passing through the rotational axis and the tip to a plane passing through the root and the tip when viewed from above the cooling fan.