Fan Radial Gap Backflow Mitigation Features
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Solution Overview
Problem
Fans used in electronic devices experience backflow air recirculation, leading to flow disturbances and increased audible noise due to the pressure differential between the inlet and outlet, which affects air flow and noise generation.
Innovation Solution
Incorporating a rotating inlet flange and backflow mitigation features, such as helical protrusions or fan blades extending into the radial gap, to redirect and counteract backflow air, reducing recirculation and noise by increasing aerodynamic resistance and stagnating air within the gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a radial gap is provided between the shroud and housing wall to enable unrestricted rotational motion, then ease of operation is improved, but backflow air recirculation occurs causing harmful noise and flow disturbances
Solution Approach 1:
A backflow mitigation feature is introduced as an intermediary element within the radial gap. This feature acts as a mediator that allows the rotor to rotate freely while simultaneously blocking the backflow path of air from the outlet region back to the inlet region, thus preventing noise-generating recirculation without restricting rotational motion
Solution Approach 2:
The radial gap is segmented by the backflow mitigation feature into separate flow regions. The feature divides the continuous radial gap into distinct zones that prevent the formation of a complete recirculation path, allowing rotational freedom while blocking harmful backflow air movement
2Object-generated harmful factors
If backflow mitigation features are added to block backflow air, then audible noise is reduced, but device complexity increases
Solution Approach 1:
The backflow mitigation feature is designed to perform multiple functions simultaneously: it blocks backflow air to reduce noise, maintains the pressure differential across the fan, and allows unrestricted rotational motion of the rotor. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity
3Quantity of substance
If backflow air is allowed to recirculate, then air flow through the radial gap is maintained, but flow disturbances occur near fan blades reducing air flow efficiency
Solution Approach 1:
The backflow mitigation feature converts the potentially harmful recirculating backflow air into a beneficial unidirectional flow pattern. By blocking the recirculation path, the feature ensures that air moves efficiently from inlet to outlet without being disturbed by reverse flow, thereby improving overall air flow productivity while still maintaining appropriate air movement through the radial gap region
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
Significantly reduces audible noise and maintains air flow efficiency by mitigating backflow recirculation and disturbances near the fan blades, enhancing the operational quietness and performance of electronic device cooling systems.
Implementation Method 1
increase an aerodynamic resistance (e.g., an aerodynamic impedance) or a static pressure within the radial gap to counter-act the pressure differential generated between the inlet and an outlet of the fan housing
Implementation Method 2
operation of the fan generates a pressure differential on opposing sides of the housing (e.g., a lower pressure at the inlet and a higher pressure at the outlet), which induces a backflow of air
Data Source
AI summary
Systems and methods are provided for mitigating recirculation of backflow fluid through a fan. The fan includes a housing having a channel that extends from an inlet to an outlet of the housing. A rotor assembly is positioned within the channel and is configured to direct a fluid flow from the inlet to the outlet. The rotor assembly includes a hub, a plurality of fan blades, and a shroud disposed about a circumference of the fan blades, where a radial gap extends between the shroud and the housing. The radial gap is configured to receive a portion of the fluid flow from the outlet as backflow fluid. The rotor assembly also includes an inlet flange that is configured receive the backflow fluid from the radial gap and to direct the backflow fluid in a direction away from the inlet prior to discharge of the backflow fluid from the radial gap.