Centrifugal Fan Impeller Asymmetric Air Outlet Noise Reduction
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Solution Overview
Problem
Conventional centrifugal fans suffer from structural limitations and high noise levels due to non-uniform wake interactions with the fan impeller and tongue, which are exacerbated by narrow gaps and pressure differences.
Innovation Solution
The centrifugal fan impeller structure features blades extending from a hub with air outlets and inlets arranged at unequal intervals, reducing blade passing frequency and sound pressure weighting to minimize noise, while allowing for flexible design based on boundary conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the gap between the fan impeller and the tongue is narrowed to reduce size, then the centrifugal fan can be miniaturized, but the noise increases due to tongue oscillation caused by non-uniform wake interaction and pressure difference
Solution Approach 1:
The patent applies asymmetry by arranging air outlets at unequal intervals between adjacent blades, creating an asymmetric flow pattern that disrupts the periodic non-uniform wake interaction with the tongue. This asymmetric configuration prevents regular wake-tongue interactions that cause oscillation and noise, while maintaining a compact fan design.
Solution Approach 2:
The patent changes the parameter of air outlet interval distribution from uniform to unequal intervals. This parameter modification alters the blade passing frequency characteristics and wake distribution, reducing the single tone noise component while maintaining acceptable fan performance in a miniaturized configuration.
2Ease of manufacture
If uniform air outlets are arranged between blades, then the structure is simple and easy to manufacture, but the noise is loud due to regular blade passing frequency interactions
Solution Approach 1:
The patent deliberately introduces asymmetry in the air outlet arrangement, positioning outlets at unequal intervals between adjacent blades. This asymmetric design disrupts the periodicity of blade passing frequency interactions, effectively reducing tonal noise while maintaining manufacturing feasibility through straightforward blade geometry.
Solution Approach 2:
The patent applies local quality by varying the air outlet positions specifically in the regions where wake-tongue interactions occur most intensely. The unequal interval arrangement targets local noise generation zones without requiring complete redesign of the entire blade structure, balancing manufacturing simplicity with noise reduction.
3Ease of manufacture
If the fan impeller is designed with fixed uniform structure, then manufacturing is straightforward, but the design cannot be flexibly adapted to different boundary conditions and noise characteristics
Solution Approach 1:
The patent enables design flexibility by allowing local variation in air outlet positions between blades. Each blade can be independently configured with specific outlet intervals tailored to particular boundary conditions, application requirements, and noise characteristics, while maintaining overall structural manufacturability.
Solution Approach 2:
The patent introduces dynamic adaptability through the unequal interval air outlet arrangement, which can be optimized for different operating conditions, fan sizes, and noise requirements. This configuration allows the impeller design to be adapted across various applications rather than being locked into a single uniform design.
Data Source
AI summary
A centrifugal fan impeller structure includes a hub having multiple blades. The blades extend from a circumference of the hub in a direction away from the hub. Each two adjacent blades define therebetween a flow way, an air outlet and an air inlet. The air outlet and the air inlet are respectively positioned at two ends of the flow way in communication with the flow way. The air outlets are arranged at unequal intervals so as to greatly reduce noise in operation.