Centrifugal Fan Protrusion Reduces Blade Noise
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Solution Overview
Problem
Centrifugal fans in miniaturized portable electronic devices face a dilemma between heat-dissipating efficiency and noise generation due to intense wake flow disturbances, which worsen as air flow increases to enhance cooling.
Innovation Solution
A protrusion is integrated into the centrifugal fan's shell, positioned between the impeller and tongue portion, to reduce blade frequency noise without significantly altering air flow, thereby optimizing noise and heat-dissipating efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the air flow is increased to enhance heat-dissipating efficiency, then the cooling performance is improved, but the wake flow disturbance becomes more intense and generates more noise
Solution Approach 1:
A protrusion structure is introduced as an intermediary element between the impeller and tongue portion. This protrusion acts as a flow guide that mediates the interaction between the rotating blades and the shell, redirecting the wake flow to avoid direct impact on the tongue portion while maintaining the necessary air flow for heat dissipation.
Solution Approach 2:
The protrusion is strategically positioned at a specific location (15-195 degrees from the C-T connecting line) with specific dimensional characteristics (gap A between 0.5×P and 0.7×(W-D)). This localized structural modification creates different flow characteristics in different regions of the fan housing, guiding the wake flow away from the noise-generating tongue portion while preserving overall cooling performance.
2Productivity
If the volute fan shell is designed to generate high hydrostatic pressure and high rotation speed, then the air convection is improved, but the wake flow hitting the tongue portion creates blade frequency noise with large amplitude
Solution Approach 1:
The protrusion serves as a flow mediator that intercepts and redirects the wake flow before it can directly impact the tongue portion. By positioning the protrusion in the flow path, it changes the flow direction and distributes the wake flow more evenly, preventing the concentrated impact that generates blade frequency noise while maintaining high air convection.
Solution Approach 2:
The protrusion modifies the flow field parameters by changing the wake flow distribution pattern. It alters the pressure distribution and flow velocity vectors in the region between the impeller and tongue portion, transforming the concentrated high-velocity wake flow into a more distributed pattern that reduces impact noise while preserving the overall convective flow.
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 protrusion effectively reduces blade frequency noise while maintaining air flow, resolving the trade-off between noise and heat-dissipating efficiency in miniaturized devices.
Implementation Method 1
the wake flow generated by the blades of the fans hits a surface of a tongue portion
Data Source
AI summary
A centrifugal fan includes a shell, an impeller, a tongue portion, and a protrusion. The shell includes a top plate, a bottom plate, and a sidewall connecting to the top plate and the bottom plate. The top plate, the bottom plate, and the sidewall define an air outlet. The impeller is disposed in the shell. The tongue portion is disposed in the shell and neighboring the air outlet. The protrusion is disposed on an inner wall of the shell and is physically connected to the top plate and the bottom plate.